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Bob McDavitt's ideas for sailing weather around the South pacific

15 July 2018

Bob Blog 15 July 2018

WEATHERGRAM

YOTREPS

Compiled Sun 15 July 2018

 

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

Kayaker Scott Donaldson made successful land fall in new Plymouth early last week after departing from Coffs harbour in early May.  See www.stuff.co.nz/national/105168174/Kiwi-Scott-Donaldsonreaches-Taranaki-the-first-person-to-kayak-the-Tasman-solo

 

I have been helping Scott with twice daily txt messages looking at currents, wind and swell. Scott is an adventurer motivated to raise money to help those with live with Asthma (such as he and his son)

If this success inspires anything in you then please show it by funding his donation page:

givealittle.co.nz/cause/tasman-kayak--- Do this soon as the page closes by end of July.

Surely such an adventure is worth a $10 donation?

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WINDY.COM have added a new layer, called THUNDERSTORMS, which comes from the global ICON model from DWD as a combination of rain and lightning density. More resolution than the CAPE parameter.

See community.windy.com/topic/6269/windy-is-the-first-weather-service-in-the-world-to-globally-forecast-thunderstorms.

Technical details are at confluence.ecmwf.int//display/FCST/45r1+new+parameters%3A+lightning+flash+density

Lightning is static electricity. Any object that spikes upwards from an otherwise flat horizon is asking to be struck by lightning. When updrafts in a shower cloud exceed around 25 km/hr (13 knots), air and water molecules are rubbed together, creating static electricity (making lots of free electrons). In the updraft, rain, ice, and snow are jumbled, and the lighter particles are lifted to the cloud top, whilst freed electron tend to attach to the heavier particles at base of the cloud. Like charges repel, and so this reservoir of electrons in the base of the cloud causes the free electrons in the ground beneath the cloud to go elsewhere. This forms an area of positive charge in the ground under the cloud. When the cloud gets blown around, this positively-charged area follows the cloud like a shadow. When the reservoir of charge in the cloud gets large enough, an explosive discharge occurs.

 

First, groups of electrons leap outwards and downwards in all directions towards the positive area near the ground. This happens in jumps, called leaders, each taking around a nanosecond, and at the end of each jump the pause may break the leader into two. When one of these leaders is within about 100 metres of the ground a group of positively-charged particles streams up from the earth to meet the leader. These are called streamers and are best made from a spike or tower (or tree). When the streamer meets the leader, the stored energy (100 million volts) is released suddenly enough so that the air in the stream is ionized. It turns to plasma, 20,000C+, or 10 times hotter than the surface of the sun for a fraction of a second. This ionization works its way up the streamer (so the light starts at the bottom and ends at the top), and this is called the return stroke. On its way up all the places where the streamer has divided get lit, hence the spread-out pattern of some lightning photos. After the first strike, the main pathway between the ground and the cloud reservoir of charge can go through another ionization episode (or strike). This is the flicker seen in a lightning strike.

 

A normal lightning path or bolt may be many kilometres long and is only as thick as a thumb. The speed of sound is 1 kilometre in about 3 seconds or 1 mile in about 5 second, and you can use the time difference between the flash and the bang to measure the distance between you and the strike. Lightning may be seen when it is 60 kilometres away, but thunder is only audible for maybe 10 to 20 kilometres. In the 19th century, thunder was thought to be caused by the implosive collapse of the partial vacuum of the lightning bolt. Nowadays, the consensus is that it is the shock wave of the sudden thermal expansion as the bolt forms plasma (air breaking the sound barrier). The rolling sound after the initial clap is sound arriving later from parts of the lightning bolt that are further away. Over land, rolling thunder also echoes off surrounding terrain.

 

80% of lightning discharges occur from top to bottom of a cloud, or between two nearby clouds (C2C or cloud to cloud). The ones that reach the ground are called C2G or cloud to ground.

 

I handle weather forecasts for around 400 yachts each year, and in the past year two have lost their navigation instruments due to lightning damage (both in tropical waters).  This seems to be a higher rate than the normal quote of 1 in a 1000 per year.

 

A yacht mast “spikes out from a flat surface” and thus tends to act like a lightning rod. Normally it is connected to the keel reasonably well by its rigging. Since lightning is static electricity it tends to flow on the outside of a surface, and so a metal mast and rigging should take most of the charge to the keel and surrounding seawater. Some extrapolate from that to say there is a cone of protection underneath the mast, but some say that’s a myth (see www.lightningsafety.com/nlsi_pls/cone-of-protection-myth.html). Installing a proper lightning rod and connecting this via copper plate to the keel may just divert some of the lightning charge so that it blows thru the copper plate, holing the keel. Opinions differ on this point.

 

When you see a lightning squall coming, the standard advice is to get the sails down and the engine going on auto helm, and standby in the companion way or below deck and cross your fingers. I’d like to add that you protect your electronic equipment: Disconnect your antenna, and gather any mobile navigation equipment such as GPS, satellite phone, tablet, laptop, etc., and toss them into the galley oven (or a microwave if you have one) as an approximation to a Faraday cage.

 

TROPICS

Tonight, we still have BERYL in the North Atlantic (now out of the tropics), and a “zone of interest” between Mexico and Hawaii.

If we compare the past week’s rain with the previous week we can see an increase in the intensity of convection around Malaysia and Indonesia. This is part of a MJO event, a trend to increased convection spreading east into the NW Pacific. This is likely to trigger tropical cyclone activity around Micronesia over the next week or two.

- see trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to hover over PNG and Solomon Islands, with a weak stretch across the Wallis and Futuna area.

A passing trough is expected to visit Tonga on Monday UTC and then travel east to visit Rarotonga on Thursday UTC and linger there until Sunday 22 July UTC.

 

Subtropical ridge (STR)

HIGH near 40S and east of NZ near 180 tonight is expected to slowly travel east along 40S this week. Associated squash zone of enhance d trade winds is expected to peak near 20 to 25S over Gambier Islands on wed to Fri 18 to 20 July UTC.

Next HIGH is expected to travel east along 25S across the north Tasman Sea on from Mon to Thu and then linger over northern NZ on Friday and Saturday UTC.

 

Around Tasman Sea, NZ to tropics.

Trough moving off NZ on Monday followed by a westerly flow. A weak trough is expected on Wednesday followed by a SW flow on Thursday.  Light winds with a passing ridge on Friday and then another trough is expected from the Tasman Sea on Saturday/Sunday.

 

Australia to tropics

A slow-moving ridge over the northern Tasman Sea this week.

 

Tahiti to Tonga

Winds around the Society island may reach a peak on local Sunday/Monday 15/16 July as a squash zone (associated with a passing HIGH) travels east.  For the remainder of the week there should be an OK east to ESE flow from Tahiti to Tonga with a minor squash zone along 25S.

South of 18S, A passing trough should reach Rarotonga area from Thursday/Friday UTC.

 

Galapagos to Marquess

SE to E to NE winds, mostly less than 20 knots. To use available currents, go to 2S 93W and then 6S 125W and then direct.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

If you would like more detail for your voyage, then check metbob.com to see what I offer.

Or Facebook at /www.facebook.com/metbobnz/

Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom).

Weathergram archive (with translator) is at weathergram.blogspot.co.nz.

Contact is bob@metbob.com or txt 6427 7762212

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

 

08 July 2018

Bob Blog 8 July

WEATHERGRAM

YOTREPS

Compiled Sun 08 July 2018

 

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

Acceleration zones

Terrain effects near mountainous islands interrupts the wind flow and divides it into rivers of wind and puddles of calm. Today’s EC (9km resolution) model as seen on windy.com shows this in the trade winds over Fiji, with an onshore seabreeze developing around Momi Bay. The EC model data is running with only a few real world observations but its portrayal closely matches the observed data at Nadi Airport.

When I was a forecaster in Fiji back in the 70s I discovered that whenever the pressure difference across Fiji gets around 2 hPa or higher (isobars drawn 2hPa apart, the winds in the accelerated zones such as Vatu-i-Ra passage, Bligh water, and the SW end of Viti Levu may be funnelled to over 25 knots. Today the EC model shows orange-coloured speeds in these acceleration zones, for 21-averaged knots or more. These zones are strongest over the sea, and it would be good to be able to position some wind stations on nearby land.

The Fiji MetService has several local rules they use for compiling the Fiji Marine forecast. This evening’s edition responds to that timeless “isobar rule”:

Marine Weather Bulletin

Issued from the National Weather Forecasting Centre Nadi

at 7:30pm on Sunday the 8th of July 2018

A STRONG WIND WARNING REMAINS IN FORCE FOR ALL FIJI WATERS.

Situation:

A high pressure system to the south of Fiji continues to direct

strong east to southeast wind flow over the Fiji waters.

 

Forecast to midnight tomorrow for Fiji waters:

East to southeast winds 20 to 25 knots. Rough seas. Moderate southerly swells.

 

Further outlook: Easterly winds 20 to 25 knots. Rough seas. Moderate southerly swells.

===

Interestingly, the GFS model, with its 13km resolution, and .25x.25 degree grib distribution does not capture these terrain effects:

 

TROPICS

Tonight, we have Storms THREE and BERYL in the North Atlantic and MARIA in the NW Pacific.

If we compare the past week’s rain with the previous week we can see an increase in the intensity of convection around Japan (severe flooding there in the past week). Also, the rain across the South Pacific has become more intense. It remains very intense around central America.

– see trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to weaken during the coming week. It is expected to hover from Solomons to Samoa, and the zone over the Solomon Islands is expected to drift slowly south this week.

The trough which visited Samoa over the weekend is expected to travel SE across the Tahiti area on local Monday and fade over the Tuamotu islands on local Tuesday.

The next trough from the west is expected to reach the New Caledonia area on local Friday, Vanuatu on Saturday, and Fiji/Tonga/Samoa early next week.

 

Subtropical ridge (STR)

HIGH is travelling east along 30S to east of NZ this week. It should have a squash zone of enhanced trade winds on its Northern side, reaching a peak near 15S between Tahiti and Samoa on Tue/Wed UTC.

Next HIGH is expected to travel across South Tasman Sea on Tue/wed UTC, northern NZ on Thu UTC and then to east of NZ along 35S from Fri UTC, fading near 170W by Sunday UTC.

 

Around Tasman Sea, NZ to tropics.

Large trough is crossing NZ on Monday and Tuesday with winds backing to SW then southerly and bursts of squally showers.

Too unsettled to depart on mon/Tue. OK to get away of Wed, but will need to allow for encounter with northerly winds ahead of the next trough

A Trough is expected to move off Australia and onto the eastern seaboard on local Thursday, and then deepen into a low between Lord Howe and New Caledonia on Friday. It is further is forecast to go southeast towards northern NZ over the next three-four days, turning in to a multi-centred system with centres below 1000hPa.

 

Australia to tropics

Stay put until after that low forms and moves away. Should be OK to go from around Sun 15 July.

 

Tahiti to Tonga

It may be better to stay put next few days – due to squash zone of enhanced trade winds reaching a peak near 15S between Tahiti and Samoa on Tue/Wed UTC.

A departure on Thu/Fri UTC may be able to get as far as Palmerston Island before the next trough arrives from the west, maybe Niue.

 

Galapagos to Marquess

SE to ESE winds, mostly less than 20 knots. To use available currents, go to 2S 95W and then 6S 125W and then direct.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

If you would like more detail for your voyage, then check metbob.com to see what I offer.

Or Facebook at /www.facebook.com/metbobnz/

Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom).

Weathergram archive (with translator) is at weathergram.blogspot.co.nz.

Contact is bob@metbob.com or txt 6427 7762212

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

01 July 2018

Bob Blog 1 July 2018

WEATHERGRAM

YOTREPS

Compiled Sun 01 July 2018

 

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

JUNE REVIEW

Sea Surface temperature anomalies as at end of June may be seen at www.ospo.noaa.gov/data/sst/anomaly/2018/anomnight.6.28.2018.gif

As has been the case for a few years now, the warm anomalies outweigh the cool, so there is a net discontinuity in our oceans. The eastern equatorial Pacific is the focal region for ENSO and is now on a slowly warming trend. Temperatures around Australia and into the Tasman Sea are about to below normal, a possible indicator of drier than normal conditions in the next month or so.

The Gulf Stream off the east coast of North America still stands out as warmer than normal.

Warm anomalies continue in the north Pacific indicate a busy cyclone season for next few months.

To see how the annual weather cycle and the seasons are working out, here is a quick look at the average isobar maps for past 30 days from www.esrl.noaa.gov/psd/map/images/fnl/slp_30b.fnl.html

 

The isobar maps show that subtropical ridge in the southern hemisphere is looking robust. The North Atlantic and Northeast Pacific HIGHS are looking less strong than this time last month. The June Lows in the Tasman Sea have been less than the May Lows.

 

Polar westerly winds are stronger around Antarctica from NZ to South America but weaker than normal from South America to South Africa and around Australia to New Zealand. It’s complicated.

 

Zooming into the NZ area, the 1015hP (between blue and white) isobar has stayed put in the tropics and travelled east across NZ. It’s subtle, but observable. This indicates a change from a westerly flow to a (cooler) SW flow:

The last 30 days of rainfall, and its anomaly, as seen at TRMM at trmm.gsfc.nasa.gov/trmm_rain/Events/thirty_day.html

shows extra convergence in the ITCZ from Bangladesh to Philippines , across s the North Pacific Ocean, around the Mexican west Coast and across the equatorial Atlantic, but it has been drier than normal over the Caribbean..

In the Southern Hemisphere there are large dry regions: Around Madagascar/ Western Indian Ocean, Vanuatu to Southern Cooks (the normal position of the South pacific Convergence zone), and the Amazon.

 

The Indian Monsoon 2018 arrived faster and earlier than normal, as seen at www.imd.gov.in/pages/monsoon_main.php

 

 

TROPICS

Tonight, we have a TC off the west of Mexico (FABIO) and in the China Sea (PRAPIROON). Also, the remains of EMILIA are travelling to the NW, leading the way for FABIO.

 

If we compare the past week’s rain with the previous week we can see that the intensity of the rain in the South Pacific Convergence Zone and around central America is intensifying.

– see trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to stay put from northern Coral Sea /Solomon Islands to northern Vanuatu, to Samoa to Southern Cooks. A small low should form on the SE end of the SPCZ, to SE of southern Cooks, on Tuesday 3 July UTC and deepen as it gets further SE.

And a small but rather intense passing trough/tropical low os expected to form over Wallis/Futuna are on Thu/Fri UTC and travel over Vava’u are on Fri UTC and Niue/Southern Cooks area on Sat UTC. Avoid.

 

Subtropical ridge (STR)

New HIGH is expected to spread into the Tasman sea on Mon/Tue and then travel NE across northern NZ on Wed/Thu and further NE next weekend.

 

Around Tasman Sea, NZ to tropics.

Looks Ok for a voyage for NZ to tropics any day this week.

Small low is expected to form off Queensland coat on Monday and fade in situ by Thursday. Strong disturbed westerly flow is expected to spread east from Tasmania/southern New Wales from Wednesday, reaching South Island of NZ by Friday.

TROUGH that crossed NZ on Sunday is expected to deepen into a LOW over Chatham Islands on Monday UTC that is expected to go NE on Tuesday/Wednesday UTC and then east/southeast. Avoid this Low.

 

Australia to tropics

Not this week, too much head wind. But an opportunity may be appearing around Sat 7 July.

 

Tahiti to Tonga

A dose of strong SE winds is expected to affect northern parts of this area on Monday and Tuesday UTC. And on Fri/Sat UTC a small but intense low/passing trough is expected to affect the Vava’u to Niue area. Next week may be better.

 

Galapagos to Marquess

SE to E winds, mostly less than 20 knots. To use available currents, go to 2S 95W and then 5S 120W and then direct.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

If you would like more detail for your voyage, then check metbob.com to see what I offer.

Or Facebook at /www.facebook.com/metbobnz/

Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom).

Weathergram archive (with translator) is at weathergram.blogspot.co.nz.

Contact is bob@metbob.com or txt 6427 7762212

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

24 June 2018

Bob Blog

WEATHERGRAM

YOTREPS

Compiled Sun 24 June 2018

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

Cyclone Slowdown.

In Nature Magazine this month there was an article about a gradual slowdown in the speed of movement of tropical cyclones. James Kossin (www.nature.com/articles/s41586-018-0158-3) studied data from 1949 to 2016 and showed tropical steering fields have reduced by 10% globally and by as much as 15 to 20% regionally (as much as 30% over land in NW Pacific). The slower a cyclone moves the greater the amount of rain it can deliver to the places it visits. Indeed the peak rain rates of storms have been measured to have increased by 30% over the past 60 years, see www.businessinsider.com.au/hurricanes-and-rain-getting-stronger-2018-6 and www.businessinsider.com.au/hurricanes-moving-more-slowly-causing-more-damage-2018-6

 

Marine Barometer.

I’ve been trying out a few smart apps on my mobile phone (iPhone 6S) to use its inbuild gps and motion/pressure sensors to measure air pressure (a barometer). Some can mimic a barograph, but need continual access to your location, and that drains the battery.

The one app I like the best, and I think will appeal to mariners, is the Marine Barometer (for iPhone or android) from Starpath (go to Apple store or Google Store and search for Marine Barometer). In particular it appeals to me for it has an averaging function over 14 seconds, so it’ll work OK on a yacht going up and down in a sea way (sea waves have a period of 7 or less seconds and swells have a period of 7 to 14 seconds). Also, it simply allows you to store your readings and thereby keep a log. See www.starpath.com/marinebarometer/about.htm.

 

TROPICS

All quiet at present, but there is a tropical depression off the Mexican west coast.

If we compare the past week’s rain map with the previous week we can see a general relaxation everywhere.

– see trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to stay put from northern Coral Sea /Solomon Islands to northern Vanuatu, and be weak over Fiji, and sporadic over Tonga. A passing convergence zone is expected from Niue area to south of Southern Cooks.

 

Subtropical ridge (STR)

A High is expected to travel east along 35S this week, entering Tasman Sea from New South Wales on Tuesday and Wednesday, and then onto central NZ on Thu/Fri/Sat, and then off to NE of NZ on Sunday/Monday. There is likely to be a squash zone of strong SE winds on the nort side of this high in the Coral Sea.

 

Around Tasman Sea, NZ to tropics /FP

TROUGH is expected to cross Northern NZ on Monday followed by strong SW flow on Tuesday with large swells to 25S. Conditions are looking OK for departure from northern NZ to the topics from Wednesday but may encounter strong SE winds north of 25S next week. 

 

Australia to tropics

Strong SE winds are forecast in the Coral sea this week, and there seem to be too many SE/E wind for a good trip form Brisbane to Noumea this week.

 

Tahiti to Tonga

A convergence zone is expected over Niue are on Tue UTC and Raro area on Wed UTC. Otherwise it looks like a good enough week—and be aware there is the possibility of a squash zone next week, so this week may be better.

 

Galapagos to Marquess

SE to E winds, mostly less than 20 knots. To use available currents, go to 5S 110W and then 5S 120W and then direct.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

If you would like more detail for your voyage, then check metbob.com to see what I offer.

Or Facebook at /www.facebook.com/metbobnz/

Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom).

Weathergram archive (with translator) is at weathergram.blogspot.co.nz.

Contact is bob@metbob.com or txt 6427 7762212

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

17 June 2018

Bob Blog 17 June

WEATHERGRAM

YOTREPS

Compiled Sun 17 June 2018

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

CAPE  addendum.

I was asked to try and track down who originated the CAPE index. I‘ve looked and not found—maybe someone who reads this can fill us in. The earliest stability indices where when we started to use weather balloons to measure the vertical temperature profile and plotted this data on what we call tephigrams.

 

See a tephigram at www.meteo.mcgill.ca/wxlab/ATOC-546/notes/lesson07.convection/ this us a Meteorologist’s lunch: 27  parameters listed on the right, and CAPE is the red area .

For teh latest tephigram see weather.uwyo.edu/upperair/sounding.html ( select New Zealand and  Gif Stuve  then NZWP )

Spot indices such as the Lifted index  LIFT (difference between Temperature of environment and temperature of adiabatically-lifted parcel at , say, 500hPa),  and Showalter index  SHOW (much the same but at 850hPa) can be computed quickly on a Tephigram and were the first ones used. CAPE can also be shaded-in on a Tephigram and takes into account the whole vertical range of the temperature profile (what we call the “sounding”) and so carries more finesse. When computer models started to go global we needed a good way to parametrise the  vertical temperature profiles  so they could  be compared around the planet. That’s when CAPE became popular.

 

The earliest paper I could find using it is M. W. Moncrieff, M.J. Miller (1976). "The dynamics and simulation of tropical cumulonimbus and squall lines". Q. J. R. Meteorol. Soc. 120 (432): 373–94. Bibcode:1976QJRMS.102..373M. doi:10.1002/qj.49710243208. At rmets.onlinelibrary.wiley.com/doi/abs/10.1002/qj.49710243208

 

CAPE is good, but not a universal convective index. You can see how it is always highest in the tropics. This is because when the air is warmer, CAPE can be higher.   However, thunderstorms in the mid latitudes triggered by air being forced to rise over a mountain range--- such as the Southern Alps or the Andes --- can have updrafts just as powerful as their tropical cousins –even if they have much lower CAPE values.

 

As we approach the SOLSTICE this week(Thu 21June 1007UTC), it is time to check the state of the ENSO = neutral

 

The Atmosphere:

El Nino and La Nina are opposite ends of the swing of an identifiable tropical influence on our seasonal weather. The La Nina, caused by cooler than normal seas along the equatorial eastern pacific, shifts the subtropical ridge away from the equator, and the El Nino, with warmer than normal seas, draws the subtropical ridge closer to the equator. Their comings and goings can last several months, maybe over a year, and so their status can be used to help forecast the weather for the coming season.

 

ENSO = El Nino/Southern Oscillation. The main parameter we watch from the atmosphere is the Southern Oscillation Index SOI (30 day running mean) as it sums up the whole weather pattern over the South Pacific in one number. It is based on the standardized difference in the barometer readings between Tahiti and Darwin, in other words it counts the average number of isobars between them on the weather map. When the SOI is more than plus one (standard deviation from its mean) for more than a month we call it a LA NINA event, and when it stays more than minus one we call it an EL NINO event.

 

From June 2017 to May 2018 the SOI has been mostly between plus 0.5 to plus 1, sometimes higher, consistent with a weak but rather persistent La Nina. The subtropical ridge line was further from the equator than normal, and trade winds were stronger than normal.

However, over the past month, the SOI has settled into a near zero state, and has a NEUTRAL status.

Neutral conditions as seen at www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi&p=weekly

(Note that in this graph on the vertical axis 10= 1 standard deviation)

 

The Ocean:

NINO3.4 is a region in the eastern equatorial Pacific Ocean that acts as a heat storage area during an El Nino or becomes cooler than normal during a La Nina. This plays with the heat budget of the atmosphere and thus with the weather patterns.

At the farmonline web site we can see the trend in the sea surface temperature in the NINO3.4 area. The diagram shows the warm seas of the El Nino of 2015 looking like a hump on a camel. Since then there has been a cool period late 2016/early2017, then a warm period until July/Aug 2017, and then a cool period. That cool period seems to be coming to an end now, and the sea surface temperature are near normal.

Fading La Nina as seen at www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=nino34&p=monthly

 

The International Research Institute of the Climate Prediction Centre compiles data from several ENSO prediction models. The model predictions for the Nino 3.4 SST anomaly is that the seas ae likely to gradually WARM during the rest of this year, but the average of the predications has only warming to 0.5 above normal--- not enough to be called an El NINO event (but closer to it that we have been for a while).Then again 3 of the models are hinting at an El NINO by end of the year.

CPC/IRI predictions are at iri.columbia.edu/our-expertise/climate/forecasts/enso/current/

 

Latest SST anomaly map shows a zone of slightly warmer sea from Galapagos along equator to dateline. Worth watching, if it grows we can expect the trade winds to weaken. The remains of the cooler seas of the recent La Nina seem to be further south.  Sea surface temperatures across the Pacific can be seen  at www.ospo.noaa.gov/Products/ocean/sst/anomaly/index.html

 

TROPICS

There has been an MJO in the North Pacific over past week or so, triggering several developments: MALIKSI bypassed Japan, followed by EWINIAR

AT present we have TC GAEMI off the south of Japan, also expected to peel off to the northeast, and this is likely to be followed by another tropical depression. Can be seen at www.metoc.navy.mil/jtwc/products/wp0818.gif

 

Off the western Mexico coat we had tropical storm ALETTA and BUD over a week ago and now we have TC CARLOTTA pounding the Mexican coast with potential flodding rain for Acapulco.. It’s the second-earliest fourth tropical cyclone in this region during the satellite era (since 1966), missing out on being the earliest by 6 hours.

Can be seen at www.nhc.noaa.gov/storm_graphics/EP04/EP042018_5day_cone_no_line.png

 

If we compare the past week’s rain map with the previous week we can see a build-up of activity over yanmar and in the China Sea, and a focussing of activity off western Mexico. Activity has eased across the South Pacific.

– see trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to stay put from Solomon island to north of Vanuatu, and be weaker than last week. There may be some rain from a passing trough other Austral island of southern French Polynesia.

 

Subtropical ridge (STR)

A High is expected to travel east along 25 to 30S from 180 to 150west this week. There is likely to be a small squash zone of enhanced trade winds and swell on its northern side, affecting mainly 17S from 150W to 170W /Niue mainly on Tue/Wed UTC.

Next HIGH from the west is expected to enter the south Tasman Sea around Thu 21 June and then spread across NZ on Sat/Sun 23/24 June.

 

Around Tasman Sea, NZ to tropics /FP

LOW1 is expected to cross central NZ on Monday /Tuesday, and Low2 is expected to travel from northern Tasman Sea on Tuesday to east of northern NZ by Thursday.

After Low2 there is a reasonable-looking weather pattern for heading off north to tropics or east to Tahiti. Might be able to depart on Thursday, but that voyage may have some strong winds off shore on its first night.

 

Australia to tropics

There is a good opportunity this week, on the back end of Low1/Low2.

However, strong SE winds are forecast in the Coral sea this week.

 

Tahiti to Tonga

South Pacific convergence zone is not really a factor of concern this week.

Passing trough over Australs on Monday 18June UTC and gambier Islands on Tuesday 19 June UTC.

There is expected to be a zone of enhanced ESE winds over 20kt and swells over 2.5m along around 17S from 150W to 170W /Niue mainly on Tue/Wed UTC.

Next trough from the west is expected to reach New Caledonia on Tue 19 June UTC, Fiji/Tonga on Thu 21 June UTC, and then Rarotonga around Sun 24 June UTC.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

If you would like more detail for your voyage, then check metbob.com to see what I offer.

Or Facebook at /www.facebook.com/metbobnz/

Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom).

Weathergram archive (with translator) is at weathergram.blogspot.co.nz.

Contact is bob@metbob.com or txt 6427 7762212

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

 

 

10 June 2018

Bob's Blog

WEATHERGRAM

YOTREPS

Compiled Sun 10 June 2018

 

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

CAPE  an index for thunderstorms and lightning

One of the parameters available from the www.windy.com sidebar is the CAPE index—the Convective Available Potential Energy.

Basically, this measures buoyancy of the air, the amount of heat released if there is any convection. On earth we normally have static stability. Sometimes parts of the atmosphere become unstable. The way we meteorologists study instability is called the “parcel method”: we look at a parcel of air starting off near the ground with temperature T(parcel) or Tp and compare this with the vertical temperature profile of the wider environment, called T(environment) or Te. If the parcel of air is lifted it will cool at the standard atmospheric lapse rate. So the “lifted-Tp” is less than starting Tp. However, the wider environment may have some unstable layers. In these layers the “lifted- Tp” gets HIGHER than the surrounding Te, or lifted-Tp>Te, meaning the parcel has gained buoyancy (or become less dense than its surroundings) and will accelerate upwards. It will continue accelerating upwards until it eventually finds a matching Te (neutral buoyancy) and then slow to a stop (or until deposited ice particles stick together, but that’s another story). This is the convective process, and you can see it happening in the rising turrets of active cumulus clouds.

Modern weather models have many vertical dots in their matrix, and thus store a vertical profile of the atmospheric temperature or a Te. With aid of a rather complex equation (which I won’t show here), we can turn this Te profile into a single number that shows how much energy is released (in joules per kilogram) if a parcel of air is triggered to rise from the surface. This is called CAPE and if it is zero then the parcel just drops back again. If CAPE is positive then the parcel will rise, and the higher the CAPE, the faster the rise.

It has been suggested (but not yet measured) that the updraft speed in a thunderstorm needs to be over around 25 km/hr (13 knots) in order to be able to be strong enough to separate the charged particles and produce lightning discharge. This seems to correspond with a CAPE of 2000, so this is the threshold I use for the pink area of CAPE in my weather map for these blogs.

 

There was a squally front over the Lau group of Fiji and southern Tonga last Thursday night.  It occurred in an area well east of the main convergence zone and its sudden onset, and six hours duration, and ferocious content was downright dangerous and, in some cases, damaging.

Computer models don’t have enough incoming data to be able to get a good enough “grip” of the atmosphere to resolve such squall lines, and all they were showing was a zone of light winds. The satellite imagery showers jetstream cloud, mainly further west, and the weather maps mainly showed a convergence zone to southwest of Fiji. The jetstream cloud could be used as a warning sign, for these squalls are known to occur near the equatorward side of the the entrance region of a jetstream.

I have used the earth.nullschool.net archive to zoom in on a surface wind map of Fiji area, with a white overlay of CAPE. The CAPE is high all the way between Fiji and Samoa, so does seem to over some warning of squalls, albeit rather vague and imprecise. I suspect that if we had more incoming data, the CAPE view would also be more precise. In the meantime, all I can offer to those afflicted by that thumping, is that weather is a mix of pattern and chaos. Our following of the pattern is vaguer than the reality of the chaos.

 

TROPICS

Off the western Mexico coast we have tropical storm ALETTA and BUD.

Travelling northeast past Japan we have TC MALIKSI and in the China Sea we have Tropical depression EWINIAR

 

If we compare the past week’s rain map with the previous week we can see a build-up of activity over India to Indonesia/Vietnam, along the ITCZ across the North Pacific and Panama, and also along the SPCZ especially near Fiji.

– see trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to stay put from Solomon island to Vanuatu to southern Fiji. There may be an arm of extra convection from Tuvalu to Tokelau and possibly to Tuamotu Islands. It is expected to have another quiet week between Tahiti and Tonga

 

Subtropical ridge (STR)

A High over southern New Zealand on Monday is expected to travel northeast to east of NZ towards 35S 120W by end of the week. There may be enhanced trade winds between 10 and 20S to north of this high from mid-week.

Next HIGH from the west is expected to enter the Tasman Sea around Thu 21 June—a long way away

 

Around Tasman Sea, NZ to tropics /FP

LOW1 approaching NZ from the north is expected to curve westwards and cross the Auckland area on Tuesday. It has strong winds and rain tied up with its warm front in its dangerous quadrant (southeast of centre) and this is expected to affect the Gisborne area, which is vulnerable and flood-prone due to heavy rain last week.

There is another Low, Low2, near Lord Howe Island tonight, and this is expected to go northeast and fade.

 

This means that after Low1 gets south of Northland, there is a reasonable window of opportunity for sailing north to the tropics---the voyage will encounter a zone of lights winds near 30S.

Another trough is expected to travel east across the Tasman Sea on Saturday reaching South Island on Sunday and North Island on Monday 18 June. Preceded by strong NW winds—finally a good direction for kayaker Scott Donaldson attempting to Kayak across the Tasman Sea (with me watching the weather) Sadly Scott got caught in an eddy loop last week and it has taken a week to get out of it. Follow Scott’s progress at tasmankayak.com/

 

Australia to tropics

There is a good opportunity this week, with LOW2 until is around until Tuesday and with the trough approaching from the west until Friday.

 

Galapagos /Marquesas

From Galapagos area to Marquesas, departure can be any time this week. Best path for avoiding direct down-windsailing is to go to 10S 130W, then go direct.

 

Tahiti to Tonga

South Pacific convergence zone is well to the north this week, and route is clear of any strong convection. Expect ESE winds over 20 knots between 10 and 18S from 12 to 15June with 2m+ swells as HIGH passes to the south.

 

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

If you would like more detail for your voyage, then check metbob.com to see what I offer.

Or Facebook at /www.facebook.com/metbobnz/

Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom).

Weathergram archive (with translator) is at weathergram.blogspot.co.nz.

Contact is bob@metbob.com or txt 6427 7762212

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

 

27 May 2018

Bob Blog 27May 2018

WEATHERGRAM

YOTREPS

Compiled Sun 27 May 2018

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

TROPICS

In the Arabian Sea MEKUNU has made landfall onto Oman and faded away. As seen at metoc.navy.mil/jtwc/products/io0218.gif

ALBERTO has started toff ten north American Cyclone season slightly earlier than normal and is referred to as a Subtropical STORM  From www.nhc.noaa.gov/storm_graphics/AT01/AL012018_5day_cone_no_line.png

And the Indian Monsoon is arriving on time in SE parts of Colombo (As seen at windy.com)

 

If we compare the past week’s rain map with the previous week we can see the cyclonic activity in the Arabian Sea and Florida/ Caribbean area  – see trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to stay put from Solomon island to Northern Vanuatu to south of Fiji to Southern Cooks.

A trough with extra wind and rain is expected to travel east across Fiji/Tonga/ Niue on Monday UTC 

Accumulated rainfall for next week  can be seen at windyty.com

 

Subtropical ridge (STR)

The STR continues to be weak in the South pacific this week.

The HIGH over the southern Tasman Sea on Monday is helping to feed a polar outbreak by shovelling polar air northwards.

This HIGH should travel eastwards across NZ on Tuesday/Wednesday/Thursday.  And then intensify as it travels off to the east of NZ late this week.

 

Around Tasman Sea, NZ/Aus to tropics

Some people have been referring recent NZ weather to be a “false spring” with periods of warmth and now a polar outbreak.  However, the nights are noticeably getting longer, and the transition from autumn weather systems to winter weather systems is now complete, with cold fronts reaching as far as 25south.

This week a LOW is expected to form in the south Tasman Sea on Wednesday and the its progress to the east is expected to be delayed by the high on its eastern flank.  This Low is finally expected to travel east across central NZ, with wind and rain, on Mon 4 June, a public holiday in NZ.  

Those travelling to tropics should be able to get far enough north with a Monday departure so as to get to north side of trough when it arrives this weekend, an Ok voyage.   However, a Tuesday or Wednesday or Thursday departure may start in light winds and get caught by the northerly winds ahead of the next trough from Thursday, or in the next trough itself on Sunday/Monday.

 

New Zealand to French Polynesia

A departure by Wednesday this week looks good. And should be able to ride to polar outbreak.

 

Galapagos /Marquesas

From Galapagos area to Marquesas, departure can be any time this week. Best path for wind and current is to motor/sail to south of 4S then go to 6S 110W, then follow the current to 7S 128W then go direct. 

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

If you would like more detail for your voyage, then check metbob.com to see what I offer.

Or Facebook at /www.facebook.com/metbobnz/

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom).

bob@metbob.com or txt 6427 7762212

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

 

Bob Blog 27 May

WEATHERGRAM

YOTREPS

Compiled Sun 27 May 2018

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

TROPICS

In the Arabian Sea MEKUNU has made landfall onto Oman and faded away. As seen at metoc.navy.mil/jtwc/products/io0218.gif

ALBERTO has started toff ten north American Cyclone season slightly earlier than normal and is referred to as a Subtropical STORM  From www.nhc.noaa.gov/storm_graphics/AT01/AL012018_5day_cone_no_line.png

And the Indian Monsoon is arriving on time in SE parts of Colombo (As seen at windy.com)

 

If we compare the past week’s rain map with the previous week we can see the cyclonic activity in the Arabian Sea and Florida/ Caribbean area  – see trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to stay put from Solomon island to Northern Vanuatu to south of Fiji to Southern Cooks.

A trough with extra wind and rain is expected to travel east across Fiji/Tonga/ Niue on Monday UTC  

Accumulated rainfall for next week  can be seen at windyty.com

 

Subtropical ridge (STR)

The STR continues to be weak in the South pacific this week.

The HIGH over the southern Tasman Sea on Monday is helping to feed a polar outbreak by shovelling polar air northwards.

This HIGH should travel eastwards across NZ on Tuesday/Wednesday/Thursday.  And then intensify as it travels off to the east of NZ late this week.

 

Around Tasman Sea, NZ/Aus to tropics

Some people have been referring recent NZ weather to be a “false spring” with periods of warmth and now a polar outbreak.  However, the nights are noticeably getting longer, and the transition from autumn weather systems to winter weather systems is now complete, with cold fronts reaching as far as 25south.

This week a LOW is expected to form in the south Tasman Sea on Wednesday and the its progress to the east is expected to be delayed by the high on its eastern flank.  This Low is finally expected to travel east across central NZ, with wind and rain, on Mon 4 June, a public holiday in NZ.  

Those travelling to tropics should be able to get far enough north with a Monday departure so as to get to north side of trough when it arrives this weekend, an Ok voyage.   However, a Tuesday or Wednesday or Thursday departure may start in light winds and get caught by the northerly winds ahead of the next trough from Thursday, or in the next trough itself on Sunday/Monday.

 

New Zealand to French Polynesia

A departure by Wednesday this week looks good. And should be able to ride to polar outbreak.

 

Galapagos /Marquesas

From Galapagos area to Marquesas, departure can be any time this week. Best path for wind and current is to motor/sail to south of 4S then go to 6S 110W, then follow the current to 7S 128W then go direct.  

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

If you would like more detail for your voyage, then check metbob.com to see what I offer.

Or Facebook at /www.facebook.com/metbobnz/

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom).

bob@metbob.com or txt 6427 7762212

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

20 May 2018

Sam is going negative

WEATHERGRAM

YOTREPS

Compiled Sun 20 May 2018

 

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

Weather regimes – SAM

Humans love finding patterns in things. Our orbit around the sun is so repeatable and predictable that we have “seasons”. Watching weather maps long enough, one can see that sometimes the same weather system (or extreme) may repeat in clusters. Last week I blogged about ENSO showing how flip-flops of the sea surface temperatures near the Galapagos are used to help decide if the weather pattern for the next season or so can be slotted into an El Nino or a La Nina regime. There are other cyclic anomalies on different time scales that we can use to help forecast if a weather regime may occur over the next few months.

 

Tonight, I think I’ll blog about SAM, the southern annular mode. This is a measure of the strength of the westerly winds in the Polar vortex - the ring of westerly winds that circle the planet between 50S and the Antarctic circle (66 S). The value of SAM alters the north-south movement of this vortex. A high positive value of SAM occurs when the air pressure over Antarctica are lower than normal, so that the westerly winds in the polar vortex are stronger than normal (note, the actual isobars over Antarctica are always higher than those in the polar vortex, but SAM works with the anomaly values, not the actual values). So, in a high positive SAM the polar vortex is shifted southwards, and pressures over NZ are higher than normal, with weaker than normal westerly winds and settled weather.

 

This can be seen at blog.metservice.com/Southern-Annular-Mode

 

However, when SAM is negative, the westerly winds in the polar vortex are weaker. This allows the polar vortex to spread outwards and thus northwards, so that west to southwest winds over NZ are stronger than normal.

 

SAM tends to flip-flop from positive to negative, and then to hold a phase for several weeks. When SAM jumps from positive to negative, it usually means that the polar vortex weakens, and the blob of cold air that has been sitting over Antarctica and getting colder over a number of weeks is able to burst outwards like a dam break. In other words: “a polar outbreak”.

 

I can not find any real time. or forecast data for SAM (which refers to differences  in pressure anomalies in the zone south of 50S), however a proxy of SAM is available, namely the AAO or Antarctic Annular mode (average 700hPa Z wind component 20S to 90S) as at  www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/aao/new.aao_index_ensm.html

 

And forecast issued today shows that the AAO is about to have a negative jump later this week. This indicates a good chance of a polar blast somewhere (not necessarily affecting NZ). Looking at EC data of the surface air temperature forecast on windy and comparing Sunday with the forecast for Friday, it seems that the main change may occur around south and southeast of South America.

 

TROPICS

It was an interesting week with a tropical cyclone making landfall from the Red Sea onto Ethiopia. There’s also a tropical low in the Arabian Sea and it is expected to make landfall onto Oman, the horn of Africa, this week. And the Indian Monsoon is poised to strike a few days earlier than normal.

See timesofindia.indiatimes.com/india/monsoon-to-arrive-on-southern-coast-on-may-29/articleshow/64221885.cms

Next week a tropical low is expected to form in Gulf of Mexico and then make landfall on Florida next weekend.

 

If we compare the past week’s rain map with the previous week 

as at trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

we can see the increase in activity across the Indian Ocean. There are also been a build up in activity in the NE Pacific Ocean. And the South Pacific Convergence zone has weakened and split into two.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

No tropical depressions or troughs this week. The SPCZ is expected to weaken and retreat to be just between Solomon Islands and Tuvalu, maybe as far east as Tokelau. This provides a good weather pattern for yachts seeking to go westward this week.

 

Subtropical ridge (STR)

The STR is weak in the South pacific this week, and that allows a LOW to form in a passing trough near 30S 170W on Monday UTC and to deepen and it travels off to the SE reaching a peak 995hpa near 38S 140W on Wednesday, then fade and go east. May affect traffic between NZ and Papeete, avoid.

Next HIGH is still quasi stationary around Aussie Bight this week, but expected to poke out a tongue of a ridge along 30S from Wednesday, and this should expand be a High east of NZ from Friday. No squash zones.

 

Around Tasman Sea, NZ/Aus to tropics

Disturbed SW flow. One front travelling east over NZ on Tuesday/Wednesday., with SW swells reaching 7+m in eastern Tasman Sea.

Next front travelling east across NZ on sat/Sun 26/27 May. There is a chance that a HIGH may bud off from Southern Ocean and move into Tasman Sea after this front. In which case there may be a good weather pattern for departing from NZ to the tropics around Monday 28 May. Still too far away to be sure.

The SW swells from South Tasman sea should reach New Caledonia south coast with a burst over 3m from Thursday 24 May until early next week.

 

New Zealand to French Polynesia

Avoid departing when a front s near NZ as on Tue/wed or Sat/sun, otherwise Ok to go.

 

Panama to Galapagos /Marquesas

Panama area is surrounded by active shower activity this week, and there are SW winds, so nothing favourable on offer this week. If you do motor off, go SSE to 4N 79W then SSW to 2N 80W and then west to 2N 86W.

From Galapagos area to Marquesas, departure can be any time this week. Best path for wind and current is to motor/sail to 4 South 95W, then sail to 6S 127W and then go direct.

 

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

If you would like more detail for your voyage, then check metbob.com to see what I offer.

Or Facebook at /www.facebook.com/metbobnz/

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom).

bob@metbob.com or txt 6427 7762212

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

 

13 May 2018

Bob Blog 13 May 2018

WEATHERGRAM

YOTREPS

Compiled Sun 13 May 2018

 

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

The state of the ENSO =  neutral

 

The Atmosphere:

El Nino and La Nina are opposite ends of the swing of an identifiable tropical influence on our seasonal weather: the La Nina, caused by cooler than normal seas along the equatorial eastern pacific. shifts the subtropical ridge away from the equator, and the El Nino, with warmer than normal seas, draws the subtropical ridge closer to the equator. Their comings and goings can last several months, maybe over a year, and so their status can be used to help forecast the weather for the coming season.

ENSO = El Nino/Southern Oscillation. The main parameter we watch from the atmosphere is the Southern Oscillation Index SOI (30 day running mean) as it sums up the whole weather pattern over the South Pacific in one number. It is based on the standardized difference in the barometer readings between Tahiti and Darwin, in other words it counts the average number of isobars between them on the weather map. When the SOI is more than plus one (standard deviation from its mean) for more than a month we call it a LA NINA event, and when it stays more than minus one we call it an EL NINO event.

For the past year the SOI has been mostly around plus 0.5 to plus 1.0, consistent with a weak but rather persistent La Nina. The subtropical ridge line has been further from the equator than normal, and trade winds were stronger than normal, but are now close to normal.

However, over the past month, the SOI has settled into a near zero state, and has a NEUTRAL status.

Neutral conditions may be as seen at www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi&p=weekly

(Note that in this graph on the vertical axis 10 = 1 standard deviation)

 

The Ocean:

NINO3.4 is a region in the eastern equatorial Pacific Ocean that acts as a heat storage area during an El Nino or becomes cooler than normal during a La Nina. This plays with the heat budget of the atmosphere and thus with the weather patterns.

At the farmonline web site we can see the trend in the sea surface temperature in the NINO3.4 area. The diagram shows the weekly temperature anomalies since Jan 2015, with the El Nino of 2015 looking like a hump on a camel. Since then there has been a cool period late 2016/early2017, then a warm period until July 2017, and then a cool period. That cool period seems to be coming to an end now, and the sea surface temperature are near normal.

Near normal as seen at www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=nino34&p=monthly

Waters beneath the surface are slightly warmer than normal

 

The International Research Institute of the Climate Prediction Centre compiles data from several ENSO prediction models. The model predictions for the Nino 3.4 SST anomaly is that the seas ae likely to gradually WARM during the rest of this year, but the mean of the predications has only warming to 0.5 above normal--- not enough to be called an El NINO event (but closer to it that we have been for a while).

See CPC/IRI predictions at iri.columbia.edu/our-expertise/climate/forecasts/enso/current/

 

Latest SST anomaly map shows the remains of a large blue pool of cooler water across the central equatorial Pacific. Also, there are warmer yellow waters appearing around the Galapagos.

See the Sea surface temperatures across the Pacific on 10May at www.ospo.noaa.gov/Products/ocean/sst/anomaly/index.html

 

TROPICS

 

There are a few tropical depressions in the north Pacific, but they seem to be weak this week.

The rain map for the past week shows peak rainfall occurring around Indonesia and Micronesia – see rmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

No tropical depressions or troughs this week. The SPCZ is expected to remain strong over Solomon Islands and then weak across Tuvalu and Tokelau, then strong from around Niue to Southern Cooks.

 

Subtropical ridge (STR)

HIGH to east of NZ is expected to remain quasi-stationary near 30S shifting from 160W on Monday to 140W by end of the week.

Next HIGH is expected to remain quasi stationary around Aussie Bight this week and may poke out a tongue of high pressure across the north Tasman sea late in the week. There should be a squash zone of strong SE winds forming in the northern coral sea from Tues 15 Nay, in response to this HIGH, and this squash zone may extend to New Caledonia/ southern Vanuatu next week.

 

Around Tasman Sea

Low 1 in mid Tasman Sea on Monday is expected to travel onto central NZ on Wednesday.

Low 2 should form southeast of Lord Howe on Wednesday and then travel onto northern NZ on late Thursday. After that there may be a trough passing over NZ on Sunday, and then, with luck, a swing to SW winds.

 

New Zealand to Tropics

There may be a gap between passing troughs lows with a departure from Northland on Tuesday, or late Friday, otherwise may need to wait until SW winds arrive next week.

 

New Zealand to French Polynesia

Northwest to westerly winds or an offer for a good start this week.

OK for sailing east, but don’t depart in the passing troughs on late Thursday.

 

Panama to Galapagos /Marquesas

For sailing from Panama, the upcoming week looks to have head winds from SW /S around 15 knots. May be better to stay put and hope for better next week.

From Galapagos area to Marquesas, departure can be any time this week. Best path for wind and current is to motor/sail to 4 South 95W, then sail to 7S 130W and then go direct

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

If you would like more detail for your voyage, then check metbob.com to see what I offer.

Feedback to bob@metbob.com or txt 6427 7762212

I’m on Facebook at www.facebook.com/metbobnz/

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com, Subscribe/unsubscribe at the bottom.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

 

06 May 2018

Bob Blog 6 May 2018

WEATHERGRAM

YOTREPS

Compiled Sun 06 May 2018

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

ONE addition to last week’s Blog:

In French Polynesia: the PolyMagNet (Polynesian Magellan net) takes reports from vessels under way and is a good source for information exchange about anchorages, weather, services, events and activities. Twice daily on 8173 kHz at 18:00 and 4:00 UTC. Most of the 7 net controllers have been around French Polynesia for many years and have plenty of info to share with new arrivals.

 

Weather trend over the last month.

Sea Surface temperature anomalies as at end of April may be seen at www.ospo.noaa.gov/data/sst/anomaly/2018/anomnight.4.30.2018.gif

The SST anomaly image is now noticeably different from what it was at end of March.  With sea temperature sin the south Tasman Sea near normal, and the cool anomalies near the equatorial East Pacific much weaker than what they were.  In fact, some warm anomalies are starting to show near the Galapagos

The Gulf Stream off the east coast of North America continues to stand out as being much warmer than normal; this extra heat continues to energize storms over the northeast of North America into their spring.  Warm anomalies continue over much of the North Pacific, and that may be an indicator to a busy cyclone season there later this year.

During April there really was only one cyclone KENI which started near Vanuatu and peaked near Kadavu in southern Fiji. There was intense monsoonal rain over Fiji during the fortnight ahead of KENI, and the cyclone managed to take those clouds away. A full time-map of the season’s cyclones can be seen on wikipedia at en.wikipedia.org/wiki/2017%E2%80%9318_South_Pacific_cyclone_season

To see how the annual weather cycle and the seasons are working out, take a  look at the average isobar maps and their anomalies at www.esrl.noaa.gov/psd/map/images/fnl/slp_30b.fnl.html

The averaged-isobar map shows that subtropical ridges are looking good in both hemispheres.  The anomalies show that the HIGHS which were affecting NZ have been replaced by lows. The 1015hP (between blue and white) isobar has retreated during the last month to a smaller area over the NZ region, and can be seen shifting northwards over Australia.

The last 30 days of rainfall, and its anomaly, may be seen at TRMM at trmm.gsfc.nasa.gov/trmm_rain/Events/thirty_day.html

This rain map shows the “extra convergence zone” stretching from just south of Galapagos westwards to NW of Marquesas, but weaker than normal.  It also shows very dry conditions for the past month over northern Australia, and dry in Brazil.

 

 

TROPICS

The MJO oscillation is traveling across northern Australia this week, but is weak and not expected to do much.There is a weak tropical depression between Philippines and Micronesia and it is expected to shift off to the north this week.

 

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to remain close to where it was last week, with  its activity focused on a line stretching from Solomon Islands to Rotuma to Samoa to Southern Cooks.

Convection between Galapagos and Marquesas is expected to continue to weaken.   

Accumulated rainfall for next week from windyty.com.

 

Subtropical ridge (STR)

HIGH in the central Tasman Sea on Monday is expected to slowly travel is expected to slowly travel across northern NZ on Wed and Thursday, and then off to the northeast of NZ from Friday.  There is likely to be a squash zone of enhanced trade winds on the north side of this HIGH from Southern Cooks to Tonga early next week.

Around Tasman Sea

Deep Low from the Southern Ocean is expected to whip past southern NZ on Monday /Tuesday /Wednesday with strong westerly winds and large swells.

Another Low is expected to visit Tasmania on Thursday and then travel northeast into the central Tasman sea on Sunday and Monday. Avoid.

This Low should bring a S/SW wind change to the Southport to Noumea route on Sunday/Monday 13/14 May. The SE winds should return to the Noumea area by end of Tuesday 15 May, but it may be a few weeks before this pattern repeats, so this opportunity may be best on offer for a while for sailing from Southport to Noumea.

 

New Zealand to Tropics

Looks Ok for departures until Tuesday. After that, voyages going north  are likely to encounter northerly winds ahead of the next incoming trough by Friday.

New Zealand to French Polynesia

Light winds over northern NZ until Wednesday, and then northerly winds, which may be somewhat wet, but ok for sailing east.

 

Panama to Galapagos /Marquesas

For sailing from Panama, the upcoming week looks to be just light winds as far as 5North and then  SSW to SE winds.  Difficult.

From Galapagos area to Marquesas, departure can be any time this week. Best path for wind and current is to motor/sail to 4 South 95W, then sail to 7S 130W and then go direct

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If you would like more detail for your voyage, then check metbob.com to see what I offer.

Feedback to bob@metbob.com or txt 6427 7762212

I’m on Facebook at /www.facebook.com/metbobnz/

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com.

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29 April 2018

Bob Blog 29 April

WEATHERGRAM

YOTREPS

Compiled Sun 29 April 2018

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

FIVE Amendments/additions to last week’s blog.

1.For those depending on Shortwave radio, remember that ZLM / Taupo Maritime Radio offer a continuous 7/24 Trip reporting service see www.maritimenz.govt.nz/about/what-we-do/safety-and-response/maritime-radio.asp

2.Northland Radio ZMH292 is owned and operated by Peter Mott and provides free of charge check in service on multiple maritime frequencies.  Note that Peter is NO LONGER a coordinator for PACSEANET.  Northland Radio tracks vessels and has a formal policy for dealing with a missed check in.   To use Northland Radio, operator requires Maritime Restricted Radio Operators Certificate (MRROC).  In the maritime radio service, the callsign is assigned to the vessel, and in New Zealand it starts with ZM. See northlandradio.nz/faq/

3.PACSEANET is a ham (amateur radio) network providing a free of charge check in service on amateur frequency 14300KHz USB in the 20 metre band (at 0300UTC).  To participate, operator needs to hold an Amateur Radio Operators Certificate (General class or above).  In the amateur radio service, the callsign is assigned to the licensed operator, so this is a different callsign from using a maritime callsign.  In New Zealand amateur callsigns start with ZL.   See pacseanet.com

4.EMAIL: To get a one-off weathergram via email:

Send an email to query@saildocs.com, no subject needed with message SEND nz.wgrm

Or Send an email  to yotreps@oceantracking.com, no subject needed with message WEATHERGRAM

 

To subscribe/unsubscribe to Weathergram

Via saildocs, send an email to query@saildocs.com, no subject needed with message SUB nz.wgrm   (or SUBSCRIBE nz.wgrm)

To cancel use CANCEL nz.wgrm or UNSUB nz.wgrm or UNSUBSCRIBE nz.wrrm

 

Via oceantracking, send an email to totreps@oceantacking.com, no subject needed with message JOIN WEATHERGRAM

To cancel use LEAVE WEATHERGRAM

5.And exciting NEW information

In association with www.cruisersat.net  we have set up two new ways to subscribe to WEATHERGRAM

long – (this has all the text), ideal for those using sat phone or HF SSB with sailmail/winlink and

short - for those using satellite messengers such as Garmin inReach—reducing the weathergram to 4 text messages.

To subscribe, email the message (no subject needed) "subscribe boatname" to weathergram@cruisersat.net for long version or to weathergram_short@cruisersat.net for short version. Boatname has to be unique and less than 20 characters long.

Once subscribed you will receive weekly weathergram in short format optimised for satellite messenger. You also will be able to send message to weathergram_short@cruisersat.net to ask Bob a question. The Boatname that you used when subscribing will be used to sign your message.

 

TROPICS

There is expected to be a weak MJO burst of extra energy travelling across Northern Australia to Coral Sea during the next two weeks.  This increases the risk of tropical cyclone formation.

One has formed in the Indian Ocean near 12S 88E between Cocos and Chagos Islands.

see www.metoc.navy.mil/jtwc/products/sh2118.gif

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ has been reasonably quiet for past few weeks and is expected to gradually become more active over the next few weeks.  This week its activity should be focused on a line stretching from Solomon Islands to northern Vanuatu to southern Fiji.

The “extra convergence zone” around 5 to 7S from SW of Galapagos around 95W to 110Wis still there but fading. 

Accumulated rainfall for next week is seen at windyty.com.

 

Subtropical ridge (STR)

HIGH is expected to travel east this week, into central Tasman Sea south of Lord Howe island on Monday and Tuesday, then onto central NZ by Thursday and Chatham Islands by Friday, then off to the east.

Around Tasman Sea

Low is expected to cross northern NZ on Monday and then should move off to the east from Tuesday.   There is likely to be a SQUASH ZONE of strong SE winds just NE of NZ on Thursday between the new HIGH and the old Low.  This zone at its peak may have swell over 5 metres from the southeast so is worth avoiding.

Should be Ok to depart from northern NZ for the tropics after that squash zone, maybe on Thursday- such a voyage may encounter NE winds near 26S on Sun/Mon 5/6 may,  but these can be accommodated with waypoints.

 

New Zealand to French Polynesia

That Low travelling east asway from NZ with a squash zone on Thursday  is likely to delay a comfortable start from NZ until Thursday (but perhaps a start  from Auckland southwards may be done late Wednesday).  Those who departed last week should make their way to around 28S to get on the right side of this system.

 

Panama to Galapagos /Marquesas

For sailing from Panama, there is expected to be some moderate northerly winds early n the week and the best-looking day for departure is YUESDAY (local). Will need to work in with SW/S/SE winds from 5N onwards.

From Galapagos area to Marquesas, departure can be any time this week. Best path for wind and current is to motor/sail to 5or 6S 95W then go west to 125W and then go direct

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

If you would like more detail for your voyage, then check metbob.com to see what I offer.

Feedback to bob@metbob.com or txt 6427 7762212

I’m on Facebook at /www.facebook.com/metbobnz/

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com, Subscribe/unsubscribe at the bottom.

Or, if email wasn’t from WordPress then send a reply email saying LEAVE or QUIT

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

 

22 April 2018

Bob blog 22 April , where to get weather info

WEATHERGRAM

YOTREPS

Compiled Sun 22 April 2018

 

Bob McDavitt’s ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.

 

Now that cruising sailors are on their final preparations for departing New Zealand / Australia for the warmth of the tropical Islands, ‘t’is is a good time to review the ways to obtain weather forecasts and/or ways to give position reports when at sea.

 

This may look like advertising, oh well, I only do it once a year. I advise those who are planning to depart to do their homework NOW, check these web sites and at least know what’s available. If I’ve forgotten something, please sting me with feedback. I have not canvassed any of the services listed below for promotion, so what you read now is purely my opinion, hopefully unbiased, except when I mention MetBob.

 

1. For those depending on Shortwave radio, all the Oceanic the HIGH SEAS forecast for the area SUBTROPIC from MetService is read out in English via ZLM at 0303hr, 0903hr, 1503hr and 2103hr NZST on 6224 and 12356KHz and at 0333hr, 1003hr, 1533hr and 2203hr NZST on 8297 and 16531 KHz.

 

The SUBTROPICS boundary changed on 13 December 2017 and the map  shows the new boundaries, see http://www.metservice.com/marine-surf/high-seas/pacific

 

2. With SSB there is access to the well-known PacSeaNet, offering a free-of-charge daily check-in service.

 

Your SSB license allows you to participate. Listen in at 0300UTC on 14300KHz in the 20 metre band.

 

Position reports are received and reported in the well-know YOTREPS format and displayed online. People onshore can listen in to the radio feed from the Pacseanet.com website. This net includes 17 listening station dotted between Australia and Alabama. They pride themselves in being able to listen to all yachts across the Pacific, reception conditions allowing.

 

3. Another SSB service is offered by Yachts in Transit or YiT. Patricia and David from Gulf Harbour Radio use the web site http://www.yit.co.nz \to keep track of boats that listen to their rollcall/weather service. FIRST register on this web site with your boat and crew details and then you simply email or radio in your position and conditions in preferably each day (send@yit.co.nz or via SSB). These reports are plotted on a webpage for you and your friends. The website offers a link to hear the radio online, and also to view all the South Pacific AIS data.

 

David is on air, daily except Sunday NZ date at 1915UTC/0715am NZST on ZMH286 on 8752Khz or 8779KHz or 8297KHz. Other frequencies have been allocated for far away yachts. He first takes in reports and then, at 1930UTC/0730am NZST does a round-up of the weather in each island group, including passage weather,  from east to west across the South Pacific,

 

4. Those who have access to email have several options:

 

Saildocs may be used to relay the text details of a webpage even if you only have email and no access to the Internet. They are able to send you the latest edition of MetService warnings by sending an email, no subject necessary, to query@saildocs.com with message

 

SEND http://m.metservice.com/warnings/marine

 

For subtropics use SEND http://tgftp.nws.noaa.gov/data/raw/fq/fqps43.nzkl..txt

 

For Fiji MetService High Sea use SEND http://www.met.gov.fj/aifs_prods/10140.txt

 

This system also works for Northland coastal sailors using a smart phone with email.

 

The formula to get a copy of the latest coastal area BRETT via email is to send an email to query@saildocs.nz with message SEND http://m.metservice.com/marine/coastal/brett

 

5. YOTREPS was originally setup to allow yachts with email access to file their position reports and receive weather data. It started back in 1997/1998 thanks to the inspiration of Mike Harris of SV PANGOLIN. He has retired from this now and it is being maintained by www.oceantracking.com You can still use it to file your YOTREPS by email to Reports@oceantracking.com and receive by email the Fleet code or my weathergram. I have had problems uploading my weathergram to them over last few weeks,but should be able to get that sorted.

 

6. Some satellite phones now provide wifi/bluetooth that allows nearby smart phones to connect to the Internet via an ap.  One of the smart phone aps that make good use of this feature is www.predictwind.com which supplies forecast model data, Observations, and, at the Professional Account level, tools for routing and comparing departure dates. It also has a position tracking tool.

 

And, I think, Windy.com also has a position tracking option via an ap.

 

7. Some satellite phones now allow text messages, even if they don’t allow emails. Text messages are all that is needed by some web-based position-tracking sites such as YellowBrick or Garman InReach or Bluewater Tracks.

 

Of course, the AIS system allows tracking via Satellite (without  “phone”), but the display online of that data is restricted by subscription to sites such as marinetraffic.com.

 

8.  A new provider is cruisersat.net— using sophisticated filters to reduce the text of  a weather forecast /warning to a pithy TEXTABLE alternative, free of charge to the average user of text on any satphone. They also have a forecasting option based on NOAA weather models. They have asked me if I would like to make my Weathergram available via their system. If you’d like this, please provide me with some feedback, and I’ll decide accordingly.

 

9. MetBob. Ahhh yes—— I am available to help with emails or texts covering weather to help with departure date planning, waypoints for the voyage and updates along the way.

 

Here is a copy of my terms and services for your consideration:

 

There are three ways I, as retired MetService weather ambassador, may further help you with weather information:

 

Weathergrams (free), MetPack (a book), and voyage forecasts (charges apply).

 

a: Weathergrams: This is a Weathergram. I occasionally (usually on a Sunday) email out my evaluation of weather patterns around the South Pacific, aiming on what weather is worthwhile to AVOID. These are great for helping to pick windows of opportunity for good sailing weather.

 

Internet site is weathergram.blogspot.com .

 

Illustrated edition is at metbob.wordpress.com/

 

b: Mariners MetPack for Southwest Pacific: This book is available from www.boatbooks.co.nz/weather.html#23104.

 

It is also online free of charge at about.metservice.com/our-company/learning-centre/mariners-met-pack/

 

Pass that around,  as this link, in  itself, is worth a free drink anywhere, so I’m told.

 

c: Voyage Forecasts: When available I can compile and email weather forecasts for your voyage on the high seas in the South Pacific. Charge is $10NZ per 5 minutes with NO Goods or Sales tax component. Anything taking less than 5 minutes is called a quickie and sent without charge.

 

Preparation – Takes me 5 to 10 minutes (usually less than 5 so no charge), to do a weather outlook picking departure day that avoids rough weather.

 

Departure – Takes me 30 to 40 minutes to do a full voyage forecast, see http://www.metbob.com for an example.

 

Updates – Takes me around 10 to 20 minutes. When underway, to get an update email or TXT me a position report and ask for an update.

 

I tab together the charges during the voyage and email you an Invoice via PayPal AFTER the voyage.

 

This may be settled via cheque or securely online by credit card on PayPal –

 

My PayPal name is bob@metbob.com.

 

Forecast limitations: Weather is a mix of pattern and chaos. A forecast is just an idea from isobar/computer patterns, and chaos comes from the real world to unravel the pattern.

 

I combine together the data from a combination of several wind/wave/current models/patterns and use a routing program www.expeditionmarine.com/about.htm to come up with what I think is the most comfortable looking voyage, reducing it to a series of simple waypoints for you to follow.

 

My ideas should only be used as a supplement to official sources, not a replacement. My liability is limited to the value of my invoice. Under the Law of the Sea (UNCLOS) and GMDSS regulations: the skipper is responsible for navigation of the vessel..

 

End of where-to-get-weather  review==============================================

 

TROPICS

 

We are having a quiet period at present. The MJO phase diagram can be used to detect further activity, if you know how to read it. Basically, it says the next dose of activity in the western parts of the South Pacific may be in the Northern Coral Sea in early May, but does not look to be marked enough to do much. We shall see.

 

MJO Phase diagram is seen at www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/forca.shtml

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is going thru a quiet period at present, and should be weaker this week than last week.

Even so, at the southeast end of the SPCZ a LOW is expected to form around 30S 155-160E around 26/27 April at the end of this week. This affects yachts sailing from NZ to French Polynesia but may help them follow the rhumb line rather than do the “east then left: triangular route.

There is still an “extra convergence zone” around 5 to 7S from SW of Galapagos around 95W all the way to west of 180. It’s not extreme but is worth avoiding. It shouldn’t really be there in late April, but c’est la vie: maybe it marks the dying part of the recent La Nina.

 

Accumulated rainfall for next week may be seen at windyty.com.

 

Subtropical ridge (STR)

It’s the second and final week of the school holidays in NZ, and all parents are watching the weather map for a STR to cross New Zealand, Yes, there is one. And it looks like it should travel east across the North Island on Wednesday and Thursday—something only possible in Autumn. Wednesday is ANZAC day, a day to remember war victims/heroism—and a new Peace Memorial (rather than a war memorial) is opening in Porirua, Wellington.

So, parents, you have been given your window, don’t muck it up.

 

As for cruising sailors, anyone attempting an early departure from northern NZ is likely to be thwarted by onshore NE wind after that mid-week High and should wait until around 1 May when the southerly wind son the backside of the following low decrease. That gels with the nominal 1st of May.

 

Around Tasman Sea

Problems. A low is expected to form in a trough of New South Wales, south of Lord Howe Island. This is expected to travel across North island don Friday /Saturday, mucking up last weekend of school holidays.

Opportunities: That low should kill the trade winds between New Caledonia and Australia and offer OK conditions, at least for motoring, from Australia to New Caledonia.

 

Panama to Galapagos /Marquesas

For sailing from Panama, there is expected to be some moderate northerly winds on Monday. After that the winds are likely to switch to light southwesterly. So, if you are waiting to go, go Monday.

As from getting from Galapagos to Marquesas this week, first motor sail to around 5S 95W (may also find a tail current), then can sail direct, but that “extra” convergence zone continues to straddle 5 to 6S from about 90W to beyond 120W. Something to avoid.

 

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

If you would like more detail for your voyage, then check metbob.com to see what I offer.

Feedback to bob@metbob.com or txt 6427 7762212

I’m on Facebook at /www.facebook.com/metbobnz/

Weathergram text only (and translator) is at weathergram.blogspot.co.nz.

Weathergram with graphics is at metbob.wordpress.com, Subscribe/unsubscribe at the bottom. Or, to unsubscribe, send a reply email saying LEAVE.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 

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