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

29 July 2018

Bob Blog 29 July 2018

WEATHERGRAM

YOTREPS

Compiled Sun 29 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.

The state of the ENSO = neutral, but leaning towards an El Nino.

 

The Atmosphere:

The tropics influence our seasonal weather, swinging from El Nino to La Nina, and occasionally hovering in-between (called neutral). The La Nina is caused by cooler than normal seas along the equatorial eastern pacific and it shifts the subtropical ridge away from the equator. The El Nino, with its warmer than normal seas in the target region, 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. However, over the past two months, the SOI has settled into a sub-zero state, but has not been strong enough to be called an El Nino, and so is deemed to be NEUTRAL.

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

 

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 in mid-2017, and then a cool period until May this year. In the past two months NINO 3.4 has been around plus 0.5C, in NEUTRAL territory.

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

Waters beneath the surface are slightly warmer than normal, as seen at www.cpc.ncep.noaa.gov/

 

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 over the next few months and then remain steady a few months and then ease back in 2019. SO there may be an El Nino event, and it should peak between October and February.  CPC/IRI predictions are at  iri.columbia.edu/our-expertise/climate/forecasts/enso/current/

And the latest SST anomaly map shows warm yellow waters across the central Pacific.

See www.ospo.noaa.gov/Products/ocean/sst/anomaly/index.html

 

In summary, it seems that there may be an incoming El Nino, and it should peak late in the year. This is likely to cause the subtropical ridge between New Zealand and the Tropics to shift to the north, and thus to encourage the cold west to southwest winds to be more noticeable than normal around New Zealand and the Tasman Sea during the coming spring.

 

TROPICS

After a busy July in the NW Pacific, conditions are returning to normal for the start of August.  As seen at tropic.ssec.wisc.edu/

 

Rain eased over India and Japan last week, but the monsoon is active from Pakistan to SE Asia and over the Philippines

See: trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to stretch from PNG and Solomon Islands to north of Vanuatu to the Tuvalu/Tokelau area.

A passing trough is likely over Southern Cooks on Tue 31 July reaching Austral Islands on Thursday 2 August UTC.

A passing trough is expected to cross New Caledonia on Mon UTC and travel east along 20 to 25S reaching Tonga on Thursday UTC and then fade.

Trough crossing NZ on Thursday is expected to develop a subtropical LOW near 25S 180 around Friday 3 Aug UTC that may travel slowly along 25S and deepen to BELOW north of 1000hpa on Sun/Mom 5/6 August UTC and then further east. Associated trough should reach Cooks by Sun 5Aug followed by W/SW winds. Avoid.

 

Subtropical ridge (STR)

Weak HIGH is expected to travel east across northern NZ on Monday and then off to east.

Next HIGH is expected to travel across southern Tasman sea on Thu and build to east of South Island from Sat 4 August.

The squash zone between this HIGH and the LOW near 25S should produce an easterly gale with 5m+ swells near 27 to 30S next week. Avoid.

 

Around Tasman Sea, NZ to tropics.

Ridge over NZ on Monday and trough on Tuesday NW flow on Wednesday and a trough on Thursday. Then an easterly to NE flow for late in the week with Low to northeast and HIGH to southeast. A week to stay put.

 

Tahiti to Tonga

May be able to so some Island hopping north of 20S until Wed or Thu, then should stay put. Incoming trough reaching Cook Island, including Suwarrow, by Sun 2 Aug UTC followed by W/SW winds.

 

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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

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22 July 2018

Bob Blog 22 July

Bob Blog

WEATHERGRAM

YOTREPS

 

Compiled Sun 22 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.

 

After my notes on lightning last week, one of my readers has asked me to try and have ago at explaining the old folk-lore expression “Red sky at night, sailors delight; red sky in the morning, sailors warning”

(land dwellers change the sailor into a shepherd).

 

Reading weather signs is one thing that humans have been doing ever since we have been human enough to detect pattern amongst the chaos. And this sign is a good one, often proving true. In Matthew 16.2, Jesus told the Pharisees that “When evening comes and the sky is red, you say the weather will be fair, and in the morning when the sky is red and overcast, you say today will be stormy—you know how to interpret the appearance of the sky, but not the signs of the times!

 

“A Red sky at night is a delight.” Explanation, it’s as easy as 1,2,3: 1. The sun sets in the west, and, for many parts of the planet, 2 that’s where tomorrow’s weather is usually coming from. Usually the winds at cloud level above us are from northwest/west/or southwest, so weather features and clouds ride this steering field from west to east. If the western horizon is cloud-free, then there is a good chance that our tomorrow’s weather may be cloud-free.

3. Sunlight shining slant-wise loses all but its red colouring.

Air near the ground gets dirty: it accumulates particles of dust and salt and smoke that are small enough to float around (aerosols). Sun shining on these materials undergoes Mie scattering, whereby red light is mostly scattered forwards and blue light is mostly scattered laterally or backwards. As the sun sets, it beams through an increasingly longer path than at noon. It takes on a golden hue, or, if there is a lot of dust about, then the clouds above are side-lit in a rosy red. Colours can be seen to go through the spectrum and some colours are enhanced according to the aerosols of the day. Once the sun is set, red light from the aerosol layer mixes with the blue light scattered above it to form purple light.

 

“A Red Sky in the morning is a warning” Explanation: Sun rises over the eastern horizon. If that’s where the clear skies are, incoming light is rendered reddish by passing through cloud-free but dirty air. If there are clouds overhead, this usually means we are on the back end of a departing area of dry weather, and thus, as is the nature with weather, on the forward side of the next lot of rain approaching from the west. Dawn horizontally side-lights the overhead clouds with a reddish glow, enhancing our senses of pending gloom.

 

TROPICS

 

Tonight, we still have a “zone of interest” between Mexico and Hawaii.

It is a very busy time in the NW Pacific. This is in part to do with a MJO or Madden Julian Oscillation travelling into the Pacific

 

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 to south of Samoa.

A passing trough over the Southern Cooks is expected to turn into a low near 30S 160W by 23July UTC that should move off to the Southeast.

Another passing trough is expected visit Vanuatu on Mon 23 UTC, Fiji /Tonga on Tues UTC, Niue on Wed UTC and Southern Cooks on Thu 26 July UTC.

And yet another passing trough is expected to affect Eastern Coral Sea/New Caledonia area on Sat/Sun 28/29 UTC.

 

Subtropical ridge (STR)

HIGH is expected to linger in the northern Tasman Sea from Monday to Thursday and then travel off to the east along 30S.

Too many passing troughs for another HIGH this week. Me-thinks this is a sign of an incoming El Nino, that’s if I’m reading the sign of the times correctly.

 

Around Tasman Sea, NZ to tropics.

Developing low over central NZ on Monday. Then a Low is expected to form near the Kermadecs on Tuesday (as associated trough crosses Tonga). This low should deepen to below 980hpa and travel south along 170W on wed/Thu UTC and then go off to the east along 45S, bringing a SW to westerly flow to NZ, OK for departure to the tropics.

Near Australian coast a new low is expected to deepen off Sydney from Sat 28 July

 

Tahiti to Tonga

Winds around the Society islands look OK for departure any day this week. Try and stay north of the passing troughs.

 

Galapagos to Marquess

Useful southerly winds over Galapagos for going west at first. Go to 2S 106W and then 6S 128W then direct.

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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

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

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?

================

 

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.

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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

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

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