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

30 December 2018

Bob Blog 30 Dec 2019

WEATHERGRAM

YOTREPS

Compiled Sun 30 Dec 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.

 

Here’s one of the original verses from Robby Burns “Auld Lang Syne”

 

We twa hae paidl'd i' the burn

Frae mornin' sun till dine.

But seas between us braid hae roar'd

Sin auld lang syne.

 

Or in modern English:

We two have paddled in the stream,

From morning sun till dine;

But seas between us broad have roared

Since long ago

 

So, here’s my wish to you for 2019: May there be more fun paddling in the stream.

 

THE TROPICS

Latest cyclone activity and TCFP tropical Cyclone Formation Potential may be seen at www.ssd.noaa.gov/PS/TROP/TCFP/index.html or tropic.ssec.wisc.edu

 

With the MJO of increased activity making its way across northern Australia eastwards to the western Pacific, tropical depressions are starting to develop and the next few weeks are looking to be busy.

 

Tropical Depression USMAN has been very slow-moving over Philippines, and associated heavy rain has a death toll of 16 people so far.  Track map from www.rappler.com/nation/special-coverage/weather-alert/219814-tropical-depression-usman-pagasa-forecast-december-28-2018-2pm

 

In the South Pacific,  there are 5 depressions at present.

94P and 98P are likely to deepen and travel SE. 94P/TD03F is likely to visit Fiji on 31 Dec/ 1 Jan and southern Tonga on Wed 2 Jan. Followed by 98P over Fiji on Friday 6 Jan and central Tonga on Sat/Sun 5/6 Jan.

 

95P is expected to deepen in Gulf of Carpentaria over next few days and then go east and deepen over Coral Sea, possibly making landfall near Bowen on Sunday 6 Jan.

 

96S and 97P are not expected to deepen.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is at peak activity this week and there is a good chance that tropical depressions may deepen into cyclones. Today a depression has formed to SE of Tonga , on the southeast end of the SPCZ, and this is expected to travel southeastwards, laying a trail of lower pressures so that moisture from the SPCZ can fine its way into the more southern latitudes.

 

Subtropical ridge (STR)

HIGH near 40S to east of NZ is expected to be slow-moving until Wednesday and then move off to the southeast.

HIGH in Tasman Sea near 35S is expected to remain slow-moving until Thursday and then be joined by another HIGH from Tasmania and the combo should move over NZ on sat/sun 5/6 Jan.

There is likely to be a squash zone of enhanced SE winds on the north side of these HIGHS. .

 

Troughs around Tasman/New Zealand

Fronts should visit the South Island this week and finally be followed by a southerly change reaching the North Island on Friday.

 

Between Tropics and Australia.

With a high in the Tasman Sea and low pressures in the Coral Sea, expect fresh to strong easterly or ESE winds between New Caledonia and Queensland.

 

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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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23 December 2018

Bob Blog 23 Dec

WEATHERGRAM

YOTREPS

Compiled Sun 23 Dec 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.

 

Today’ weathergram includes a link to a recent video from Mainsail that looks at marine meteorologists around the world—from dingy sailing to America’s Cup/Volvo/Vendee Glob races to forecasting for solo around the world sailors.  This video requires a good Internet connection, but should give you some “holiday” viewing that may share some of what motivates us meteorologists.

See

edition.cnn.com/2018/10/15/sport/mainsail-october-weather-americas-cup-spt-intl/index.html

 

At Christmas time we start thinking of the prospects for the Sydney Hobart Race starting on Boxing Day:

 

See sailing.org/news/88257.php

In an early forecast prediction, the Bureau of Meteorology's Simon Louis told a selection of navigators at a Rolex Sydney Hobart Yacht Race press conference at the Cruising Yacht Club of Australia today to expect a little of everything in the early stages of the 628 nautical mile race.

Louis said, "The long-range weather models show relatively light winds as the yachts leave Sydney Harbour, but with a 15-20 knot (and gusts to 35 knots) north to north-easterly winds which should continue during Boxing Day night and into the next day, with the breeze expected to go around to the west later." This scenario will leave some dead spots in between.  The model is also showing a weak trough over the far NSW coast throughout this period, with lighter and more variable winds off the far south coast and into Bass Strait.

 

 

THE TROPICS

Latest cyclone activity and TCFP tropical Cyclone Formation Potential as seen at www.ssd.noaa.gov/PS/TROP/TCFP/index.html or tropic.ssec.wisc.edu

 

CILIDA is travelling off to the southeast in the South Indian Ocean.  NE of this is a tropical depression named  KENUNGA  (from last week) near 18S 77E travelling southwest.

There is a near 20% probability of development in the next few days around Micronesia and up to 6% probability of a tropical cyclone forming around the northern part of Australia or in the Coral Sea.   This probability increases with time into the New Year, so if interested in sailing in that area, “you’d better watch out”.

This footprint of increased probability is consistent with an MJO oscillation of increased convection travelling eastwards from the Indian Ocean to the Pacific Ocean over the next few weeks.  When an MJO does this in December we usually have a period of near-equatorial westerly wind appear—and sure enough one of these is forming now around Papua New Guinea and likely to extend to almost 180 longitude  by the end of this week (as may be seen at windy.com).

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is active between Papua New Guinea/central and northern Vanuatu/ Samoa at first this week and is expected to drift south so that it may reach New Caledonia /Fiji/Tonga by the end of the week.  A tropical Low is likely to develop in the Coral Sea by early next week.

 

Subtropical ridge (STR)

 HIGH forming over Chatham Islands on Monday is expected to travel eastwards along 40S this week.

HIGH forming in western Tasman Sea on Monday is expected to travel eastwards and widen so that it spreads onto NZ on Sat/Sun 29/30 Dec, after affecting the Sydney-Hobart race. 

There is likely to be a squash zone of enhanced SE winds on the north side of these travelling Highs.

 

Troughs around Tasman/New Zealand

LOW is deepening to NW of NZ on Monday and expected to travel southeastwards across North Island on Tuesday/ Christmas Day, and then clear off to the southeast across Chatham islands on Wednesday/Boxing day, followed by a cool southerly flow for a few days over NZ, – with peak southerly swells along East Coast on Thursday/Friday.

  

Between Tropics and Australia.

With a high in the Tasman Sea and low pressures in the Coral Sea, expect strong easterly winds between New Caledonia and Queensland.

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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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16 December 2018

Bobblog 16 Dec

WEATHERGRAM

YOTREPS

Compiled Sun 16 Dec 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.

 

LISA BLAIR is expected to reach Sydney on Monday, after departing from there on 14 October, and should then complete her adventure to be the first woman to do a solo unassisted non-stop sailing circumnavigation of Australia, to raise awareness of the need for Climate Action Now.

Her tracker site is gis.ee/lb/ Shows that she was hove-to in a gale last night but is now making sail for Sydney in easing conditions.

Her vessel is named S/V CAN standing for Climate Action Now.

MetBob has proudly been sending her daily weather comments. It is an honour for me to be involved in a campaign that raises awareness of the need for Climate action.

It is fitting for Lisa that the COP24 UN Climate conference in Poland has finally today been adopted. OK, it’s really only a starting point, and some are still grumbling it isn’t ambitious enough, but it’s the start of a rule book.

We need to heed what our kids are saying about the need for action. See a 15yo Swedish schoolgirl talk to COP24 at tinyurl.com/yaryncz6 (this comes courtesy of Bernie Sanders’ Democracy Now Facebook site).

“It is the sufferings of the many which pay for the luxuries of the few.”

 

If you agree that we should slow down our use of fossil fuel, for the benefit of the future weather, and for our children’s sake, and have been thrilled by the adventurous spirit of LISA and CAN in their circumnavigation of Australia, then please visit her website and read her blogs at lisablairsailstheworld.com/. Yes, a book is coming, covering her circumnavigation of Antarctica.

 

THE TROPICS

Latest cyclone activity and TCFP tropical Cyclone Formation Potential as seen at www.ssd.noaa.gov/PS/TROP/TCFP/index.html or use tropic.ssec.wisc.edu

There is a twin of cyclones in north and South Indian Ocean, with TC PHETHAI moving north onto east coast of India in next few days, and TC KENANGA moving southwest over open sea in South Indian Ocean.

 

TC OWEN did redevelop in gulf of Carpentaria and has now returned southeast back to east of the Australian coast, but has lost its support supporting structure and is now unravelling. Its energy managed to activate and deepen the heat low over interior of Victoria/New South Wales last few days, producing enhanced NE winds offshore for Lisa Blair on SV CAN, and also drenching rain to places such as Melbourne on Friday, and golf ball-sized hail to Sydney on Saturday. I suppose one pro is that its rain has helped dampen the bush in northern Queensland after recent bushfires,

 

An MJO episode of enhanced convection is travelling eastwards this week across Indonesia and north Australia, and likely to move into Pacific Ocean later this month, increasing the risk of tropical cyclone formation, as can be seen in the formation Potential map.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is active between Papua New Guinea/central and northern Vanuatu/ Fiji and occasionally Tonga /Samoa. From early in the week a low of tropical origin is expected to drift off to the southeast of Tonga and deepen in the mid latitudes.

 

Subtropical ridge (STR)

HIGH over NZ tonight is expected to move off to the east next few days along 35S.

Part of this high is expected to reform near 25S to NE of NZ by mid-week and then slide to Southeast so that by weekend of 22/23Dec there may be a squash zone of near strong SE winds between Tahiti and Tonga.

 

Troughs around Tasman/New Zealand

Trough with a cold southerly wind change expected to reach southern NZ on Monday and then go northeast and reach North island as a low on Thursday.

Low over interior Victoria/New South Wales is expected to deepen off Bass Strait on Thursday, then travel east and cross the South Island on Saturday with wind and rain affecting all NZ.

 

Between Tropics and Australia.

With the remains of TC OWEN hovering off the northern Queensland coast and an STR near or south of 25/30South we can expect moderate SE winds between New Caledonia and Brisbane for most of this week.

 

From Tahiti to Tonga

Trough over Tonga /Niue early in the week, then OK, but enhanced SE winds on weekend of 22/23 Dec

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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

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

09 December 2018

Bob Blog 9 dec

WEATHERGRAM

YOTREPS

Compiled Sun 09 Dec 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 TROPICS

Latest cyclone activity and TCFP tropical Cyclone Formation Potential as seen at www.ssd.noaa.gov/PS/TROP/TCFP/index.html or tropic.ssec.wisc.edu

There are no Tropical cyclones around at present, although there are some potential regions for development near Sri Lanka and to east of Majuro. 

Tropical depression 05P/97P was named OWEN last Sunday, and then lost its tropical cyclone credentials (no more a ring of gale winds) on Tuesday, however it has continued has a tropical depression and is still spinning.  It seems likely to cross Northern Queensland over next day or so and may deepen again in Gulf of Carpentaria mid-week.

Plots of the main global models for the likely track of OWEN may be seen at tropicaltidbits.com

 

There is another tropical Low between 05P and New Caledonia—and this is being watched closely and has been labeled 98P (1000hPa).

The latest isobar map drawn by Fiji Met (www.met.gov.fj/weather_maps.php) also shows another low 997hPa at 23S165W and SE of Niue, and Fiji Met are watching this as a possible tropical disturbance in their TC 3 day outlook at www.met.gov.fj/tc_outlook.pdf

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is active between Samoa and Southern Cooks.  Part of it may move south and visit Fiji to Tonga on Thursday and Friday. 

 

Subtropical ridge (STR)

 HIGH in the Tasman Sea tonight is expected to travel NE and fade near 175E by end of Tuesday.

 Another HIGH is expected to form over southern NZ on Wednesday and to travel northeast along eastern NZ to be east of Northland by Sunday, extending a ridge back onto Northern NZ early next week.

 

Troughs around Tasman New Zealand

Trough is expected to deepen off Tasmania on Monday and weaken over Northern NZ on Thursday/Friday.

Another Low is expected to deepen off New South Wales on Thursday/ Friday and cross the Tasman Sea over the weekend and visit central NZ mid next-week.

Arrange to arrive in NZ between the troughs.

From Tahiti to Tonga

Active convergence zone this week.  May as well stay put.

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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

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

02 December 2018

Bob Blog 2 Dec

WEATHERGRAM

YOTREPS

Compiled Sun 02 Dec 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.

 

Review of November weather:

Sea Surface temperature anomalies as at end of November may be seen www.ospo.noaa.gov/Products/ocean/sst/anomaly/index.html

The eastern equatorial Pacific around Galapagos is the focal region for ENSO and is now getting warm enough to almost be called an El Nino event.  There is currently a patch of warm water around NZ, but this may change during the next month or so, affecting the NZ summer.  There is also warmer than normal conditions between Solomon Islands and French Polynesia, and this may add oomph to the South pacific Convergence zone. 

The Gulf Stream off the east coast of North America and the Kuroshio current off Japan still stand out, which is unusual so late in the year.

To see how the annual weather cycle and the seasons are working out, check the average isobar maps from www.esrl.noaa.gov/psd/map/images/fnl/slp_30b.fnl.html

The subtropical ridge in the southern hemisphere has weakened and gone north in November.

Zooming into the NZ area, there has been a radical drop in pressure north of 45S, the 1015hP isobar has retreated  well to west and east of the Tasman sea, and the tropics have dropped to below 1010.  Sure enough the weather features in the Tasman Sea were decided troughy (after a month marked by blocking highs).  I suppose December will either continue with a troughy Tasman or continue the rhythm and have some blocking highs. Wish we could tell in advance, but weather is a mix of pattern and chaos.

 

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

The rain map shows extra convergence around  and to the north of the Solomon Islands, and also that the Intertropical convergence zone and the South Pacific Convergence zone seem to be shifting toward the equator--- an El Nino trait.

 

THE TROPICS

Latest cyclone activity and TCFP tropical Cyclone Formation Potential as seen at www.ssd.noaa.gov/PS/TROP/TCFP/index.html or tropic.ssec.wisc.edu

Tropical depression 05P /97P has deepened to 993hpa in the Coral sea and is expected to continue to deepen over next 24 hours and go south and then go west, but may fade before it gets to northern Queensland.   It is quiet elsewhere for a change.

 WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is active and moving south. it is likely to visit Fiji by mid-week, maybe the Loyalty Group to Minerva on Thursday, and maybe Tonga by local Friday.

Subtropical ridge (STR)

A new HIGH is expected to travel eastwards into the South Tasman sea by Wednesday and then go NE into central Tasman sea by the weekend.  It is a slow-moving system and may fade around Wed 12 Dec and the be replaced by another High reaching northern NZ around sat/sun 15/16 Dec.

 

Tropics to New Zealand

Trough is expected to bring a W/SW change to North island during Tuesday and then that High in the Tasman sea should maintain a southerly flow over northern NZ until end of next week.  Departures from the tropics before Thursday will encounter weak headwinds near NZ.

Between Tropics and Australia.

The High moving into Tasman Sea from mid-week means easterly winds from New Caledonia to Australia, good for sailing to Australia.  If wanting to go the other way, then depart before mid-week or go well south to avoid the easterly winds.

 

From Tahiti to Tonga

Trough related to the SPCZ is likely to reach Tonga by local Friday and then travel east.

 

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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

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

25 November 2018

BobBlog 25 Nov

WEATHERGRAM

YOTREPS

Compiled Sun 25 Nov 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.

 

A friendly KIWI welcome to all the visiting yachts who have recently arrived in NZ.

When you are sailing around our cruising grounds you may wish to check out our coastl weather:

Where to get NZ weather

MetService has 18 Coastal areas and 11 Recreational areas and produces marine forecasts for these compiled by a dedicated team of specialized marine forecasters. These forecasts are updated four times daily and carry an outlook covering the following three days.  They are available at www.metservice.com,

or for your mobile at m.metsrvcie.com.

or download the MetService Marine Ap: see more at

about.metservice.com/our-company/ways-to-get-the-weather/weather-on-your-mobile/smartphone-apps/

or via MetPhone at

about.metservice.com/our-company/ways-to-get-the-weather/metphone/

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

If you have access to email when at sea the you can download the text of a coastal or recreational marine forecast by sending a email to query@saildocs.com, no subject needed, with message

SEND http://m.metservice.com/marine/coastal/NAME

Or SEND http://m.metservice.com/marine/rec/NAME

where NAME is the name of your desired region (e.g: brett or bay-of-plenty or lake-taupo)

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

Marine Radio

Taupo Maritime runs ZLM radio HF/SSB/SW stations on 2207,4146,6224, 13356 and 16531 kHz in English

Maps are sent via Radio Fax on the following frequencies 3247.4, 5807, 9459, 13550.5, and 16340.1

Schedules are on the MetService website

NOWCASTING: New Zealand Coastguard Weather information (Nowcasting) is available via VHF for 15 places around the North Island and 5 places around the South Island.

See the map at

www.coastguard.nz/media/418138/20161019_final_coastguard-nowcasting-weather-information-channel-map.pdf

or download their app: see more at 

www.coastguard.nz/boating-safely/coastguard-app-the-boaties-best-mate/

 

Trip planning

A lot can be said about the usefulness of windy.com for checking if it may be good to go sailing over next few days. 

During the past week one of my regular readers shared with me his blog on trip planning

See twoatsea.com/that-time-of-the-year-weather-watch-2018/

Weather enthusiasts are always seeking new web sites for delving into the weather, and the best I have come across I heartily recommend is weather.geek.nz/

In particular, when planning for the week ahead, check out weather.geek.nz/nz_model_tiles.php

The weather geek site contain many weather treasures, have fun browsing.

 

El Nino:

 The latest sea surface temperature map shows an anomaly of warmer than normal seas along the equator in the eastern equatorial Pacific.   This anomaly is getting stronger and when it becomes strong enough the event is called an EL NINO.

 

Now, as we move into December we can be reminded of the origins of the naming of this tropical anomaly as El Nino.   The full title is “El Nino di Navidad” or the Christ Child of the nativity.  It got this name because in Peru, once every few years, rain fell over the usually very dry interior. These rains arrive along with warmers seas along the Peru coast around Christmas time and so the event was named after the festival they were celebrating (Spanish is the leading language in Peru).   In moderation the rains are a blessing, and the title seems fitting.   But in the past few decades an El Nino brings flooding and landslides to Peru, It also makes the anchovies harder to catch, as these fish stay in the cooler waters, and in an El Nino the top of the ocean becomes coated with warmer seas from equatorial regions, so the anchovies go so deep they are out of reach.

 

This incoming El Nino is already showing itself in Peru:

www.freshplaza.com/article/9044580/effects-of-el-nino-landslides-in-peru-tornado-in-argentina/

 

NIWA have stated that this summer’s incoming El Nino is likely to behave differently from normal.  The warmer seas along the equatorial Pacific that make up an El Nino normally occur near South America, but this year they seem to be occurring more towards the central Pacific.  This is known as a central-based El Niño, or El Niño Modoki. Modoki is a Japanese word that means "same, but different".

See www.scoop.co.nz/stories/SC1811/S00066/update-on-el-nino.htm

The unsettled weather we have been having during November is typical of an incoming El Nino. We can use this as an indicator that the coming months may bring the Bay of Islands more days with southwest winds than normal, but there will still be plenty days with sea breezes or with northeast winds.  Maybe around a third each way.

 

THE TROPICS

Latest cyclone activity and TCFP tropical Cyclone Formation Potential are seen at www.ssd.noaa.gov/PS/TROP/TCFP/index.html

MAN-YI is heading towards Japan and is expected to peel off to the east of Japan.

 USAGI  is expected to make landfall near Ho-Chi-Minh city.

Looking at the weekly rain maps, last week’s shows the tracks of MAN-YI and USAGI, and also an intense buildup of convection along the equator near 140E, just north of PNG.

This is weakening at present, but the forecast is for a robust MJO event to move into the Pacific over the net two weeks, and that may indeed increase convections along the South Pacific Convergence zone.

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

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to strengthen between Solomon Islands and north of Fiji this week.  There may be a tropical low forming near Vanuatu next week in early December.  The convergence zone between Samoa and French Polynesia this week is expected to weaken away.

 

Subtropical ridge (STR)

The STR has been shifted to around 20 to 35S and is very weak.  One small High is expected to travel eastwards from New Caledonia to south of Tonga from Tuesday to Friday this week.

Tropics to New Zealand

A series of trough and lows are continuing to cross NZ, with major lows over the North Island on Tuesday 27 and Sat 1 Dec this week.  There should be an interlude of relative calm on local Thursday. Also, there should be more settled weather for arriving in NZ from Mon 3 Dec.

 

Between Tropics and Australia.

Low from interior of Australia is expected to deepen as it moves into the Tasman Sea by around Thursday and then travel to northern NZ by Saturday. This offers opportunities for sailing from Australia to New Caledonia, but closes opportunities for sailing t’other way this week.

From Tahiti to Tonga

Looks OK with easterly winds, something light.  However, there is expected to be a weak trough traveling east to south of 20S reaching Tongan area around wed UTC and then Southern Cooks area around Sat 1 Dec, with light variable winds.

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

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

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

18 November 2018

Bob Blog 18 Nov

WEATHERGRAM

YOTREPS

Compiled Sun 18 Nov 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.

 

SAM and the Polar Vortex

The Southern Annular Mode (SAM) is a parameter that measures the westerly winds that circle Antarctica. When it is positive the belt of strong westerly winds contracts towards Antarctica—so there a higher pressures and weaker winds over southern Australia/ New Zealand. When the belt moves north towards NZ, SAM becomes negative, and storms from the Southern Ocean can reach NZ.

 

One way of thinking about SAM is that it is a measure of the strength of the dam that walls the cold air over the Antarctic. When positive this wall is strong, and when negative this wall is weak and polar air can make be diverted outwards and northwards, maybe affecting New Zealand.

When SAM drops suddenly from positive to negative, there is an increased possibility of a “polar outbreak” somewhere in the southern hemisphere.

 

A light-hearted and animated presentation of SAM as one of the climate dogs that affect New South Wales may be seen at www.youtube.com/watch?v=G-S-YmE-Lkc . To meet the whole dog pack see www.dpi.nsw.gov.au/climate-and-emergencies/droughthub/information-and-resources/seasonal-conditions/climatedogs

 

A good proxy for SAM is the Antarctic Anomaly Oscillation (AAO) as seen at www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/aao/new.aao_index_ensm.html ,this shows that SAM is forecast to dip negative this week.  It's not a huge dip, but does make SAM as negative as it was in mid-October, and if we look at the air temperature maps on a polar stereographic projection using earth.nullschool.net we can see cold air spreading north between last Thursday and tonight, turning all NZ dark green.

This helps explain the coldness of the front crossing New Zealand early this week. The abrupt temperature change helped form a tornado over the Canterbury Plains this afternoon:

see www.newshub.co.nz/home/new-zealand/2018/11/watch-witnesses-in-awe-of-massive-tornado-north-of-ashburton.html

 

THE TROPICS

Latest cyclone activity as seen at tropic.ssec.wisc.edu

GAJA continues west after crossing southern India during the past week.

There is also BROCHRA near 12S 84W going WSW.

Looking at the weekly rain maps, last week’s shows a split in activity over the Indian Ocean away from the equator, an easing in the activity over the South Pacific and an increase in activity over the tropical Atlantic.

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 and extend from east of the Solomon Islands to between Fiji and Samoa. It is likely to produce a trough that may visit Tonga mid-week and Niue area on Wed UTC, fading over Southern Cooks on Thu UTC.

 

Subtropical ridge (STR)

Since SAM is going negative , the Subtropical ridge is retreating to the north.

A High is expected to form near 25S between New Caledonia and New Zealand by mid-week and then travel eastwards to fade over Southern Tonga by the weekend.

 

Tropics to New Zealand

A series of trough and lows are expected around New Zealand this week. There should be an interlude of relative calm on local Friday.

 

Between Tropics and Australia.

OK at first, but maybe a trough travelling from Australia interior across the coast and into the Tasman sea on or around late local Thursday followed by west to southwest winds.

 

From Tahiti to Tonga

Weak trough passing over Tahiti on local Sunday, then looks Ok to go with eastly wind that may last over a week to north of 18S. Further south there is another passing trough to take into account.

 

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

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

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

11 November 2018

Bob Blog 11 Nov

WEATHERGRAM

YOTREPS

Compiled Sun 11 Nov 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.

 

HOW TO ACTIVATE A FRONT

I once send a wedding telegram along the lines of “Beware: whatever promotes upward motion can lead to frontal development”. I was reminded of this last Thursday when the front crossing the South Island turned into a monster, dropping around 700mm of rain into Cropp River (Southern Alps , between Mt Cook and Hokitika). The torrential rain mainly fell over the Southern Alps. Rivers flooded, and  the main highways were closed by slips and a washed out bridge.

 

Meteorologist know that the most important equation they need to understand is the omega equation. Basically, if you tap your barometer and it dips the you know you have falling pressure, and this is linked to rising motion/increased wind/ heavier rain. The equation explains how: it relates omega (change of air pressure over time) with changes in vorticity advection and thermal advection (I won’t explain these in much detail tonight, except that CVA (cyclonic vorticity advection) and WA (warm advection) result in negative omega (upward motion/ thicker clouds), and AVA (anticyclonic vorticity advection)/CA (cold advection) result in positive omega (sinking motion/clearing sky).

 

The recent weather event over New Zealand shows what happens when a well-defined upper trough with a strong jetstream travels eastwards faster than the associated front near the surface.

 

1. On Wednesday night, the jetstream was west of the surface front

as seen in an Isobar map 1am Thursday courtesy of MetService with red arrow showing jetstream.

 

2. Then by 1am Friday the jetstream moved on top of the front.

This was the day the front dumped its heaviest rain. There was also a “tropical pipeline” or moist conveyor belt feeding the front with moisture from the heat trough over Australia. Our own version of the pineapple express.

 

3.  And  by 1am Saturday the upper trough buckled, so that the jetstream stopped advancing over the South Island, and the front travelled off to northeast of the jetstream and decayed to a trickle.

 

Between 1 and 2, the CVA and WA reached high levels over the front, turning it into a monster (being over the Southern Alps also helped promote its upward motion). Then between 2 and 3 CVA and WA dropped off and the front faded.

 

Our global weather models have the ability to watch all these atmospheric equations with precision and can handle the forecasting of these events well in advance. Interestingly, if we add an extra 0.5 C to the air temperatures and re-run the global model, we can end up with as much as an extra 10% in the resulting rainfall.

 

Note that the subtropical ridge over the South Pacific was sufficiently north of the North Island to allow this front to spread over all of NZ. This is typical of EL NINO and is likely to become a trend over the next few months (but not the coming week). One positive response to the incoming El Nino is the hydro lake levels in NZ. Lake Pukaki was dropping in past few months but is now rising nicely: see www.meridianenergy.co.nz/about-us/our-power-stations/lake-levels

 

THE TROPICS

Latest cyclone activity as seen at tropic.ssec.wisc.edu shows that it is busy at present in the Indian Ocean.

ALCIDE is expected to fade or divert to the north of Madagascar.

GAJA is forecast to travel across southern India.

 

Looking at the weekly rain maps, last week’s shows high intensity rainfall in the Indian Ocean, and an increase in activity over the Solomon island to Samoa/Niue. and a relaxing of convection in the Intertropical convergence zone across the Pacific.

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

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is active from Solomon Islands to Tuvalu and is expected to produce a trough that should visit Fiji on Wednesday, Tonga on Thursday, Niue on Friday UTC and then go off to the SE.

 

Subtropical ridge (STR)

Unlike last week, the STR for the coming week is expected to be around New Zealand until Thursday. Another High is expected to travel across the South Tasman Sea from Saturday 17 to Mon 19 Nov.

 

Tropics to New Zealand

There is expected to be a squash zone of enhanced SE winds between Fiji/Tonga and NZ especially near 25 to 30S from Tuesday to Thursday. Further south, it looks Ok for arriving in NZ over next ten days. Trough from the south Tasman Sea is expected to spread onto South Island on Thu and then fade over the North Island on Friday.

 

Between Tropics and Australia.

Looks mostly OK, but maybe a trough offshore Coffs on Friday/Saturday with southerly winds near the coast.

 

From Tahiti to Tonga

Trough over Tonga on Thu 15 UTC and Niue/ Southern Cooks on Friday 16 UTC then travelling off to the SE. North side of this trough may reach Tahiti around Sun 18 November. Trough is preceded by NW winds and followed by a period of W /SW winds.

 

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

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

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

04 November 2018

Bob Blog 4 Nov 2018

WEATHERGRAM

YOTREPS

Compiled Sun 4 Nov 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.

 

REVIEW OF LAST MONTH WEATHER PATTERNS

Sea Surface temperature anomalies as at start of November may be seen www.ospo.noaa.gov/Products/ocean/sst/anomaly/index.html

The eastern equatorial Pacific around Galapagos is the focal region for ENSO and is now on a steady warming trend. Cyclones have been stirring the seas between Mexico and Hawaii, making avenues of cooler surface water. There is a zone of warmer seas from Solomon Island to Samoa. Temperatures around Australia and the Tasman sea remain below average, a possible indicator of drier than normal conditions in the next month or so. Also, this should cool the southwest winds that reach New Zealand.

The Gulf Stream off the east coast of North America and the Kuroshio current off Japan still stand out but not as much as last month.

 

To see how the annual weather cycle and the seasons are working out, check the average isobar maps from www.esrl.noaa.gov/psd/map/images/fnl/slp_30b.fnl.html

The subtropical ridge in the southern hemisphere has intensified during October

 

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

The rain map shows extra convergence around equatorial Indian Ocean.

 

THE TROPICS

Latest cyclone activity as seen at tropic.ssec.wisc.edu

shows XAVIER off the west Mexico coast, and it is expected to stay offshore.

Looking at the weekly rain maps, last week’s shows an increase in activity across the equatorial Indian Ocean, and a relaxing of convection around Papua New Guinea and the Mariana Islands. Not much change elsewhere.

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

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is sitting over northern Coral sea and northern parts of Vanuatu across Wallis and Futuna to northern Tonga, and part of it may travel southeast to Southern Cooks this week.

 

Subtropical ridge (STR)

High is travelling east along 25 to 35S past northern NZ from Monday to Friday and the expected to linger to east of New Zealand until early next week.

 

Tropics to New Zealand

Trough from the Tasman Sea is expected to spread onto central New Zealand by Fri 9 Nov and then stall, so that a zone of cloud and rain with light winds spreads onto northern NZ by Tue 13 to Thu 15 November. It looks OK to arrive in NZ with this trough.

 

Between Tropics and Australia.

Avoid a passing trough across the northern Tasman Sea on Wed and Thursday with light variable winds.

 

From Tahiti to Tonga

There may be a trough forming near Niue around Sunday 11 November, otherwise the forecast is for useful easterly winds.

 

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

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

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

 

28 October 2018

Bobblog 28 Oct

WEATHERGRAM

YOTREPS

Compiled Sun 28 Oct 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 = trending towards an El Nino

The Ocean:

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.

Latest SST anomaly map shows warmer yellow/orange waters appearing around the Easter Equatorial Ocean between the Galapagos and the dateline.  See Sea surface temperatures across the Pacific on 25 Oct from www.ospo.noaa.gov/Products/ocean/sst/anomaly/index.html

 

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 until last June . The current warm period is intensifying and may soon reach the El Nino threshold.

Trend to an El Nino is seen at www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=nino34&p=monthly

 

The Atmosphere:

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.

Since last May the SOI has been mostly negative, consistent with a weak but rather persistent El Nino. In early October it reached -1 for a week, but it needs to meet or exceed -1 for a month to meet the El Nino threshold. The blocked high that affected New Zealand over the past few weeks has been one of the factors that has relaxed the SOI, but this is about to be replaced by passing troughs, and that should help the SOI to become more negative.

SOI trend is 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 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 are likely to be near the +1.0C anomaly satisfying the definition of an El Nino during the next six months.

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

 

THE TROPICS

Latest cyclone activity are seen at tropic.ssec.wisc.edu

Super Typhoon YUTU ripped thru the Northern Mariana Islands during the past week.

And OSCAR may be going westwards for now but is expected to remain offshore.

 

Looking at the weekly rain maps, last week’s shows a relaxing of convection around Mexico and just north of Fiji, but an increase in activity about Papua New Guinea to the Mariana Islands (where YUTU formed). Not much change elsewhere.

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

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is sitting over northern Coral sea and northern parts of Vanuatu across Wallis and Futuna to northern Tonga, and part of it may travel southeast to Southern Cooks this week.

 

Subtropical ridge (STR)

The remains of last week’s BFH are travelling eastwards along 30S well to east of NZ.

Next High is expected to form in the Tasman Sea near 30S by Tuesday and fade by Thursday as another forms near 40S. This other High is then expected to travel NE to 25S and to north of NZ over the weekend.

 

Tropics to New Zealand

Troughs are expected to cross northern NZ on Mon29/Tue 30 / Wed 31 Oct and then sun 4 Nov and then Wed 7 Nov and maybe Sunday 11 Nov. Arrange to arrive in-between troughs.

 

Between Tropics and Australia.

For those headed to Queensland or Coffs with the Down Under Go West Rally, now in its last week: Highs in the central Tasman Sea should maintain and useful easterly flow from New Caledonia to Australia this week. Winds may get over 20 knots this Thursday and again Wed 7 November.

For more info about the Go West Rally www.downunderrally.com/about-go-west

 

From Tahiti to Tonga

There is a passing trough over Tonga on Monday UTC reaching Austral Islands by Wed UTC then moving off to the south. Should be a useful SE flow after this passing trough.

 

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

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

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

 

21 October 2018

Bob Blog 21 Oct

WEATHERGRAM

YOTREPS

Compiled Sun 21 Oct 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.

 

There has been a Big Fat High (BFH) parked over northern NZ since 13 Oct as seen on the Auckland Airport barograph (using windy.com)

We can see how the intensifying high squeezes to isobars on its periphery closer together.  This makes a squash zone of enhanced winds, in this case from Tonga to Fiji and almost to Vanuatu.

Windy.com can also plot the past 20 days of reports.  The bottom trace is a barograph and shows that this BFH relaxed between 17 and 19 October—This also caused a temporary easing of the squash zone, and several yachts picked this window of opportunity to depart Fiji/Tonga for NZ.  They still encountered a (weakened) squash zone, and it wasn’t comfortable, but could have been worse, and they got the rare opportunity of sailing from Fiji or Tonga to New Zealand without encountering a passing trough.  Sweet, and no longer on the menu.

The squash zone is expected to relax again from Tuesday.

 

The illustrated edition shows bumps twice a day in the Auckland barograph--- these are the impact of the semi-diurnal atmospheric tide.  It is always best to log your barometer reading around 10am or 10pm (local) when it’s at the top of this cycle.

 

A quick look at the mid-atmosphere 500 hPa map around the southern hemisphere shows how the blocked high around NZ is linked to two other highs around the hemisphere. This is called the wave 3 pattern.

So, when the winds aloft decrease to a crawl because of gaps in the jetstreams, that is when the surface Highs just stay where they are and are called “blocked”. 

 

 

THE TROPICS

Latest cyclone activity is seen at tropic.ssec.wisc.edu

WILLA is aiming to make landfall near SW tip of Mexico, VICENTE is expected to weaken as it travels northwest along the coast.

 Looking at the weekly rain maps, last week’s shows a build-up of convection around Mexico and just north of Fiji, but decreasing convection elsewhere, especially around the Indian Ocean. 

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

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is sitting over northern Coral sea and northern parts of Vanuatu across northern Fiji and northern Tonga towards Niue and may spread towards Southern Cooks by the end of this week.

A tropical low may forms on the SPCZ to south of Niue late this week and then travel off to the southeast. Watch our for this if travelling from Tahiti to Tonga. 

 

Subtropical ridge (STR)

The BFH which has been blocked over northern NZ is expected to start relaxing by Tuesday and then to move off to east of NZ.

Next HIGH is expected to form in South Tasman Sea from Thursday and to move onto NZ early to mid-next-week.

 

Tropics to New Zealand

The squash zone between Fiji/Tonga and NZ is expected weaken by Tuesday 

A Low is expected to form between New Caledonia and New Zealand late this week and then travel east, providing the challenge of a period of southerly winds to yachts sailing south.  Yachts from Tonga can anchor in Minerva reef and wait this out.  Yachts from Fiji will need some waypoints to handle those southerly winds.

 

Between Tropics and Australia.

For those headed to Queensland or Coffs with the Down Under Go West Rally

An active trough may reach Bundaberg area from around Sat/Sun 27/28 Oct,

so that a departure from New Caledonia by local Tue 23 may encounter that trough near the Bundaberg coast where it may be active /squally. And a departure on local Wednesday may encounter that trough further offshore where it may be weaker. This timing can change.

For more info about the Go West Rally go to www.downunderrally.com/about-go-west

 

From Tahiti to Tonga

Squash zone in this area is now fading.  An active trough is expected to reach Tonga around 27-28 Oct UTC followed by a period of NW winds, avoid.

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

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

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

14 October 2018

Bob Blog 14 Oct

WEATHERGRAM

YOTREPS

Compiled Sun 14 Oct 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.

 

I’m back “on deck” in Auckland and available to help those voyaging the South Pacific

In early October the Australian and South Pacific Cyclone centres issue their preliminary outlooks for the coming season:

The Burau of Australia headline is: Lower number of cyclones likely for Australia

Then they posted a rather confusing graphic at

www.bom.gov.au/climate/cyclones/australia/

To understand how the graphic's numbers fit in with the headline, invert them.

SO for Australia as a whole the average is 11 cyclones and the probability of average or less is 63%.

 

NIWA say that multiple severe tropical cyclones are expected: and use the assumption that the ocean temperatures are leading into an El-Nino of the El Nino-Modoki (central Pacific based) flavour during the early part of the cyclone season.

What's an El Nino-Modoki? See www.jamstec.go.jp/frcgc/research/d1/iod/enmodoki_home_s.html.en

This tugs the South Pacific Convergence zone eastwards, thus maybe reducing the cyclone risk around New Caledonia/Vanuatu, and increasing the risk for Samoa/Cook Islands/Austral Islands..

 

NIWA in New Zealand came up with following graphics:

www.niwa.co.nz/climate/southwest-pacific-tropical-cyclone-outlook/southwest-pacific-tropical-cyclone-outlook-october-2018

 

The Pacific Islands Climate Outlook Forum was held over the last few days in Nadi Fiji to help prepare for the coming cyclone season and their outlook statement is imminent.

 

Next, a quick look at the current cyclones:

After several very busy weeks, including MICHAEL over Florida in the past few days (with devastating storm surge at Mexico Beach), tonight: all we have is LUBAN over Yemen and Strom(from the Tropics) LESLIE over Portugal.

 

 

Looking at the weekly rain maps, from trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif ,

last week’s shows the path of MICHAEL and SERGIO around North America, a build-up of activity between India and Indonesia, an easing in activity around Micronesia, and much the same elsewhere.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is sitting over northern Coral sea and northern parts of Vanuatu and on-and-off to north of Fiji. It is expected to drift south towards Fiji late this week. A tropical low may form on this zone early next week and then travel eastwards towards Samoa.but then fade again by mid-next-week.

 

Subtropical ridge (STR)

It looks like the next two weeks are likely to be dominated by a BFH (Big Fat High).

A BFH has formed in the Tasman Sea and is a slow-mover with a squash zone of enhanced SE/E winds and larger swells on its northern side, peaking around southern Tonga and just south of Fiji on Monday.

From Tuesday to early Thursday (UTC) the BFH is expected to weaken around NZ as a passing trough from the Southern Ocean travels across southern and the eastern NZ. This should also weaken the squash zone north of the BFH (yea).

Then the BFH (and its squash zone) is expected to rebuild until around Wed 24 Oct and slowly travel eastwards getting east of NZ next week with a lingering ridge over north NZ.

 

Tropics to New Zealand

The best days this week to depart from Tonga /Fiji to NZ are Wednesday or early Thursday, when the squash zone weakens for a few days.

This is a rare example of a good weather pattern for arrival in NZ, with no troughs, and once it fades later this month, I suspect we will have a succession of troughs in the Tasman Sea -- and we should enjoy this weather pattern for what it is worth, even if it comes with a touch of a squash zone.

 

Between Tropics and Australia.

For those headed to Queensland or Coffs with the Down Under Go West Rally

A trough is hovering off the Queensland coast at present (its arrival brought damaging hail to Bundaberg area last Thursday) but should fade by Tuesday when it feels the domination of the BFH.

So, it is looking Ok to depart from Vanuatu/New Caledonia to Australia this week.

Note that a trough is expected to reach Coffs harbour area around local Sat/Sun and then fade, and then a more substantial trough is expected to reach Brisbane around wed 24 oct and to travel east, fading near New Caledonia by Fri 26 oct—so if you depart after Friday 19 Oct then that trough become a factor.

For more info about the Go West Rally go to www.downunderrally.com/about-go-west

 

From Tahiti to Tonga

Mainly OK for sailing this week, but a passing trough is expected to affect Rarotonga around local Sunday 14 Oct,

and a squash zone of strong 25+ knots SE winds may affect south of 18S from Niue to southern Tonga area on local Monday 15 Oct and from local Thurs 18 to Mon 22 Oct.

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

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

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

07 October 2018

BobBlog 7 Oct

WEATHERGRAM

YOTREPS

Compiled Sun 7 Oct 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.

 

I know that I wrote last weekend telling you there may be not be a weathergram today,

but I managed to find time after a kava session this evening, washed down with Octopus and cassava 😊.

 

TROPICS

The number of tropical features has decreased during the past week.

The remains of LESLIE are heading for the UK.

SERIGO is heading to make landfall in Baja California.

And KONG-RAY is moving off to east of Japan.

 

Looking at the weekly rain maps, last week's shows a drop in activity around Solomon Islands and Micronesia, otherwise little change.

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

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is sitting over Solomon Islands and expected to spread SE towards northern Vanuatu on Monday and then across Fiji on Tuesday in a coming-and -going fashion, and linger there until next week. By late Wednesday a trough should form south of Fiji, to around 30S, and this is expected to travel southeast so that it merges with the eastern side of a low from the Tasman sea crossing NZ on Friday then moving off to east of NZ. The convergence zone is likely to linger over Fiji in a stop and go fashion.

 

Subtropical ridge (STR)

HIGH weakening over northern NZ on Monday is expected to travel east along 30 to 35S reaching 140W/French Polynesia around Sat 15 local

This HIGH is NOT expected to have sufficient intensity to build a zone of strong easterly trade winds on it northern side. SO, note that is looks OK to venture from Tahiti to Tonga this week.

 

Next HIGH is expected to move in from west to south Taman Sea from Friday 12 Oct.

This should start to fade over northern NZ by Monday 15 Oct.

 

Between Tropics and Tasman/NZ/Aus.

Front/trough between Highs is expected to travel onto western South Island by Tuesday and deepen into a Low visiting northern NZ around Fri 12 Oct, and then move off to the East-south east. Avoid.

To avoid the southerly winds following this trough arrange departure from Tonga or Fiji to be after Fri 12 Oct.

 

From New Caledonia to Australia

Weather is looking OK for a voyage from New Caledonia to Australia this week.

 

From Tahiti to Tonga

With a HIGH travelling slowly just south of this route, this is a good week to do this voyage.

Note that a departure after 11 Oct may have an encounter with a passing trough and a period of changing winds on west end of voyage.

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

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

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

 

 

 

 

 

Bob Blog 7 Oct

WEATHERGRAM

YOTREPS

Compiled Sun 7 Oct 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.

 

I know that I wrote last weekend telling you there may be not be a weathergram today,

but I managed to find time after a kava session this evening, washed down with Octopus and cassava 😊.

 

TROPICS

The number of tropical features has decreased during the past week.

The remains of LESLIE are heading for the UK.

SERIGO is heading to make landfall in Baja California.

And KONG-RAY is moving off to east of Japan.

 

Looking at the weekly rain maps, last week's shows a drop in activity around Solomon Islands and Micronesia, otherwise little change.

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

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is sitting over Solomon Islands and expected to spread SE towards northern Vanuatu on Monday and then across Fiji on Tuesday in a coming-and -going fashion, and linger there until next week. By late Wednesday a trough should form south of Fiji, to around 30S, and this is expected to travel southeast so that it merges with the eastern side of a low from the Tasman sea crossing NZ on Friday then moving off to east of NZ. The convergence zone is likely to linger over Fiji in a stop and go fashion.

 

Subtropical ridge (STR)

HIGH weakening over northern NZ on Monday is expected to travel east along 30 to 35S reaching 140W/French Polynesia around Sat 15 local

This HIGH is NOT expected to have sufficient intensity to build a zone of strong easterly trade winds on it northern side. SO, note that is looks OK to venture from Tahiti to Tonga this week.

 

Next HIGH is expected to move in from west to south Taman Sea from Friday 12 Oct.

This should start to fade over northern NZ by Monday 15 Oct.

 

Between Tropics and Tasman/NZ/Aus.

Front/trough between Highs is expected to travel onto western South Island by Tuesday and deepen into a Low visiting northern NZ around Fri 12 Oct, and then move off to the East-south east. Avoid.

To avoid the southerly winds following this trough arrange departure from Tonga or Fiji to be after Fri 12 Oct.

 

From New Caledonia to Australia

Weather is looking OK for a voyage from New Caledonia to Australia this week.

 

From Tahiti to Tonga

With a HIGH travelling slowly just south of this route, this is a good week to do this voyage.

Note that a departure after 11 Oct may have an encounter with a passing trough and a period of changing winds on west end of voyage.

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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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30 September 2018

Bob blog 30 Sep

WEATHERGRAM

YOTREPS

Compiled Sun 30 Sep 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.

 

 

Note that there will be NO Weathergram next weekend (7 October).

I shall instead be on holiday in Fiji , so next weathergram is 14 October.

 

REVIEW OF SEPTEMBER 2018

Sea Surface temperature anomalies as at end of September may be seen www.ospo.noaa.gov/Products/ocean/sst/anomaly/index.html

 

The eastern equatorial Pacific around Galapagos is the focal region for ENSO and is now on a steady warming trend. Warmer than normal seas between Mexico and Hawaii have been forming a procession of tropical cyclones. There is a zone of warmer seas from Solomona Islands to Tonga. Temperatures around Australia and the Tasman sea remail below average, a possible indicator of drier than normal conditions in the next month or so. Also this should cool the southwest winds that reach New Zealand.

The Gulf Stream off the east coast of North America and the Kuroshio current off Japan still stand out as warmer than normal.

 

To see how the annual weather cycle and the seasons are working out, check the average isobar maps from www.esrl.noaa.gov/psd/map/images/fnl/slp_30b.fnl.html

 

The isobar maps show an intense High over that part of  Antarctica which is south of Australia. The subtropical ridge in the southern hemisphere has intensified during September.

 

Zooming into the NZ area, the 1010hP (between dark and light blue) isobar has shifted to south of New Zealand. And the 1020 has blossomed from the Aussie Bight to western Tasman Sea. .

 

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

The rain map shows extra convergence around Papua New Guinea and Solomon Islands.

The blue stripes in the North Pacific and Atlantic show the rain tracks of last month’s cyclones.

 

TROPICS

The number of tropical features has increased during the past week.

Map of current storms may be seen at  tropic.ssec.wisc.edu/

And we had an out-of-season cyclone LUIA in the Solomon Islands:

It has since faded away. Last time we had a cyclone in South Pacific in September was in 1950, Last time we had an out-of-season cyclone was RAQUEL in July 2015

 

Looking at the weekly rain maps (trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif), last week’s shows the rain track of TRAMI across Japan, and LIUA across the Solomon Islands. There is also a resurgence of activity along the ITCZ in the eastern North Pacific.

 

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ faded today after a burst of activity last week culminating in the brief formation of TC LIUA. There is still some activity near 13S mainly between 180 and 160E. This activity is shifting southwards and expected to visit Fiji on Wednesday as a passing trough, followed by a Southerly flow between Fiji and NZ on Thursday.

A passing trough over Tahiti is expected to travel east across Tuamotu islands by local Wednesday. Followed by increasing winds from the south-southeast.

 

Subtropical ridge (STR)

HIGH often over 1030hPa to travel east from 180 to 140W along 30 to 35S. with a squash zone of enhanced SE winds on its northern side. This squash zone is expected to be mainly north of 20S and is worth avoiding.

 

Between Tropics and Tasman/NZ/Aus.

That trough travelling south over Fiji on Wednesday is expected to morph into a Low lingering near northern NZ on Thursday and Friday, slowly travelling southeastwards. Avoid.

From around Thursday, that trough should have cleared from Fiji, so that a voyage from Fiji to NZ may be OK, but will need to go SW at first in southerly winds.

From Tonga may have to wait until Friday for OK weather for a voyage to NZ.

From New Caledonia to Australia. looks ok to go, but Mon/Tue/wed departures may encounter south to southwest winds for starters.

 

From Tahiti to Tonga

Avoid the squash zone by staying south of 20S. Anticipate a passing trough along the way early next week.

 

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

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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