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

29 May 2016

Bob Blog 29 May 2016

WEATHERGRAM

YOTREPS

Issued 29 May 2016

 

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

Tropical Storm Bonnie, the first of the year to threaten the United States, stalled in the Atlantic before strengthening slightly today.

 

Rain maps for the past fortnight from trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif show a drop in the rain over the Bay of Bengal, so maybe the Monsoon is stuttering. Not much change over the Pacific.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

SPCZ is expected to remain draped from PNG across to the Tokelau/Samoa area, with a touch over northern Cooks.

A new convergence zone is expected to build in the Coral Sea this week and move on Vanuatu on 6-7-8 June.

 

STR= Sub-tropical Ridge

The next HIGH travelling east off Tasmania on Monday is expected to build over the central Tasman Sea from Tuesday to Friday and then cross NZ on Sat-Sun-Mon.

 

Voyage Outlooks:

 

Panama to Galapagos:

Light to moderate southerly winds around Panama this week, so not a good week to depart.

Also the ITCZ seems to be active and squally at times between 8N and 5N, so another week when its better to stay put.

 

Travelling to Marquesas:

Winds near Isla Isabela are expected to be moderate southerly this week so departure any day is OK. May as well get best from the current by going to 4S then west to 135W and then direct. And around Marquesas Islands expect moderate easterly winds from local Monday.

 

Tahiti to the west

The SPCZ may affect Tuamotu area until local Tuesday (and after Thursday) but should remain clear from the Tahiti area this week. Looks like a good week for steady SE winds for sailing west towards Niue and Tonga. One proviso on this is that the outlook is for a trough to move onto the Tonga area around 09/10 June UTC.

 

Between NZ and the tropics

After two weeks of disturbed westerly pattern with active troughs, it looks like there should be a pattern change over NZ this week as , finally, a HIGH moves across Tasman Sea and then onto NZ on sat Sun Mon 4-5-6 June, our Queen’s Birthday Holiday. Yippee!

 

There are still a few days to go with disturbed SW winds over Northland. One more trough embedded in the SW flow is expected to deepen into a Low that may travel NE across the North Island on early Wednesday local, preceded by strong westerly winds on early Tuesday and followed by strong SE winds on Wednesday night.

 

So that means the next good looking departure is THURDAY, local, in quiet southerly winds.

 

There is the option of a good enough departure late on Tuesday, using the lighter winds near the middle of that passing LOW to sail with, but it rather tricky as the real world is delivering an outcome somewhat different for the ideas from the models.

 

Than Annual Auckland to Fiji yacht race starts on Saturday. This year it is ANZ Sail Fiji 2016, see sailfiji.co.nz/. Early indications is that the fleet are likely to encounter a front around mid-next week 8 June and the northerly winds ahead of this will slow them down, and may thwart any race record this year.

 

Between Australia and New Caledonia

There are easterly winds east of 160E this week. Best departure is Monday, but even that will need to tack a lot.

A series of troughs are likely to cross the Brisbane area from Wed to Sunday, so may as well stay put and maybe look at a departure Monday/Tuesday 6/7 June.

 

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

See my yotpak at boatbooks.co.nz/weather.html for terms used.

See my website http://www.metbob.com for information on tailor-made voyage forecasts

– Feedback to bob@metbob.com. Tell anyone you like that to subscribe they should email me.

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

Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom right to subscribe.

To unsubscribe, send a reply email saying LEAVE.

             

22 May 2016

Bob Blog 22 May 2016

WEATHERGRAM

YOTREPS

Issued 22 May 2016

 

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.

 

William (Bill) Gray, the founder of seasonal Cyclone forecasting, discoverer of cycles in hurricane activity, and Professor Emeritus of Colorado State University, died last month at age 86. This blog is dedicated to his memory.

 

El Nino

As we move into the time of year that the El Nino parameters typically change El Nino , we can see the current El Nino episode by looking at the Southern Oscillation Index (SOI) which counts the number of isobars between Darwin and Tahiti, and thus comes from the atmosphere. This s gradually weakening, but in a stuttering fashion. We can not tell if its latest stutter is its last.

A good view can be gleaned from www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi

 

An El Nino episode occurs when there is an excess of heat energy being stores on the planet. This heat is stored mainly on the eastern side of the planet’s largest Ocean, namely around the eastern equatorial Pacific. The NIN3.4 index measures this storage and is showing temperatures in the target area are definitely returning to normal levels. A comparison with last mega El Nino in 1997/1998 can be seen from latest graph at www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=nino34&p=monthly, and shows this mega El-Nino was slightly stronger and has lasted longer.

 

The Tropics

TC ROANU brought the worst floods in 25yeras to Sri Lanka and led to a death toll of at least 24 people in Bangladesh (2 million people relocated by its storm surge).

This brings a wet start to the Indian monsoon… but the rains are weeks away from NW Indian. NW Indian is having its annual pre-monsoon heat wave, but this year has already broken records with 51C measured in Phalodi, in the western state of Rajastan last Thursday.

Rain maps for the past fortnight from  trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif show cyclone ROANU in the Bay of Bengal.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

SPCZ is expected to remain draped from PNG across northern Vanuatu to the Tokelau/Samoa /Suwarrow/north-of-Tuamotu area, with a touch over northern Vanuatu from Tue to Friday local.

 

STR= Sub-tropical Ridge

The next HIGH over Australia is expected to move into the northern Tasman Sea on Wednesday and fade by Thursday. Next High departing Australia is likely to do so on Saturday, and may linger in Tasman Sea until mid-next week.

 

Voyage Outlooks:

Panama to Galapagos:

Light to moderate southerly winds around Panama this week, so not a good week to depart.

 

Travelling to Marquesas:

Winds near Isla Isabela are expected to be southerly this week and best for departure on local Mon to Wednesday. May as well get best from the current by going to 4S then west to 130W and then direct. Light winds are expected over Marquesas from local Monday to next weekend.

 

Tahiti to the west

The SPCZ has shifted to north of Tahiti and Tuamotu so this week should have more settled weather than last week for a departure. Since the SPCZ is likely over the northern route, take the middle route (Palmerston/Niue), or southern route (Aitutaki/Beveridge reef) rather than the northern route via Suwarrow.

 

Between NZ and the tropics

Another week of boisterous westerlies over northern NZ with one deep Low from Monday to Wednesday and another on Saturday and Sunday.

May be better to stay put until next week, unless you want to go east towards Tahiti.

 

Between Australia and New Caledonia

A Monday departure is looking best this week, but may have light winds for starters.

A Tuesday departure may encounter strong winds from a front near 160E on Friday.

A Wednesday departure may encounter strong winds from a front near 157E on Friday

A Thursday departure may encounter strong winds from a front at the start.

And a Friday or onwards depart may encounter lots of easterly winds east of 160E.

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

See my yotpak at boatbooks.co.nz/weather.html for terms used.

See my website www.metbob.com for information on tailor-made voyage forecasts–

Feedback to bob@metbob.com. Tell anyone you like that to subscribe they should email me.

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

Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom right to subscribe.

To unsubscribe send a reply email saying LEAVE.

15 May 2016

Bob Blog15 May

WEATHERGRAM

YOTREPS

Issued 15 May 2016

 

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

Several annual outlooks for the North West Pacific 2016 cyclone season have been published. The first forecast for the year was issued by CSU on December 11, who anticipated that one of four different scenarios could occur. TSR subsequently issued their first outlook for the 2016 season during December 16, 2015 and predicted that activity would be about 20% below the 1950–2015 average, or about 15% below the 2005–2015 average. Specifically they thought that there would be 13 tropical storms, 5 hurricanes, 2 major hurricanes and an ACE index of 79 units. A few months later, TSR issued their second prediction for the season during April 6, 2016 and lowered the predicted number of named storms to 12 but raised the number of hurricanes to 6. On April 14, CSU predicted that the season would be near-normal, predicting 13 named storms, 6 hurricanes and 2 major hurricanes with ACE near 93. On April 15, North Carolina State University predicted the season would be very active, with 15-18 named storms, 8-11 hurricanes and 3-5 major hurricanes. A month later, the United Kingdom Met Office (UKMO) released its forecast, predicting a slightly above-average season with 14 named storms and 8 hurricanes. It also predicted an ACE index of 125, being the average ACE index 103.

See www.metoffice.gov.uk/weather/tropicalcyclone/seasonal/northatlantic2016

 

Nothing much happening at present. We await the onset of the Indian Monsoon. Mid to late May is the Everest ascent season, and indeed there has been ascent during the past week. Once the Monsoon starts, that’s it for climbing Everest because jetstream winds return to the Himalayas.

 

Rain maps for the past fortnight show that the extra convergence zone that has been located between Galapagos and Marquesas has now faded. Wet clouds are starting to approach India from the south. Downpours in the SPCZ brought floods to parts of Samoa last week.

 

Rain for the past fortnight from  trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

SPCZ is expected to remain draped from PNG across northern Vanuatu to the Samoa area, with another branch that is over Tahiti and Tuamotu Islands relaxing from local Monday to Thursday.

 

STR= Sub-tropical Ridge

The BIG FAT HIGH that was to northeast of North Island last week had faded and is moving off to the east. The STR is expected to spend a few weeks weak and along 30S, allowing a series of troughs to travel across the Tasman Sea and New Zealand area.

 

Voyage Outlooks:

Panama to Galapagos:

Light winds for departing from Panama this week, and with a northerly touch to them on Monday and Tuesday.

 

Travelling to Marquesas:

Winds near Isla Isabela are expected to be southerly between 4 and 12 knots this week. May as well get best from the current by going to 5S 130W and then direct. Light winds are expected over Marquesas until local Tuesday and then a convergence zone with showers for Wednesday to Friday, then a day or so of 20 to 30kt SE winds and then better conditions next week.

 

Tahiti to the west

The WARC fleet are heading west from Tahiti this week, mostly going to Suwarrow, see www.worldcruising.com/world_arc/

The SPCZ has been active last week over Tahiti and Tuamotu but is expected to quieten down from local Monday to Thursday, so that offers a good opportunity for departure. Light winds are expected locally for the next few days. The gap in activity extends west wards to Suwarrow this week, but SPCZ is likely to reactivate after 21 May, more so to north 15S.

 

Between NZ and the tropics

The  Sea Mercy fleet  have mostly departed Opua for Minerva. Yachts can be tracked using the YiT website at www.yit.nz/

There may be problems getting away from NZ this week. 

There is a series of fronts all lined up ready to move onto North Island.

Monday's front is just an entrĂ©e. Wednesday’s may be the thundery one. And Friday's may turn into a LOW and be longer lasting --until perhaps Tuesday 24 May. It looks as though, during this period, it may be better to stay put so as to avoid the strong winds off the Northland coast every other day. However there may an opportunity to get away between fronts on Tuesday.

 

Between Australia and New Caledonia

The “Go East” Rally is considering departure around 7 June from Southport Yacht Club to Noumea, and some early birds are departing from any Aussie eastern seaboard before that. See www.downunderrally.com/#!go-east-the-about-go-east-rally/c5ve

Southport starts this week in the light winds of the Subtropical ridge. A useful southerly wind for sailing is expected to arrive on or around Thursday, and this can be taken to Noumea as a track to east in S winds then direct in SE winds. Another option is to depart on Wednesday and go direct, staring by motoring in light winds then sailing in SSE/SE winds. Nice weather this week and start of next week.

 

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

See my yotpak at boatbooks.co.nz/weather.html for terms used.

See my website www.metbob.com for information on tailor-made voyage forecasts–

Feedback to bob@metbob.com. Tell anyone you like that to subscribe they should email me.

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

Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom right to subscribe.

To unsubscribe from WordPress: click the "unsubscribe" link on the bottom of the email.

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

08 May 2016

Bob Blog 8 May 2016

WEATHERGRAM

YOTREPS

Issued 8 May 2016

 

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.

 

Those of you who are preparing to travel from NZ to the Fiji/Tonga are is the next few weeks may benefit from the thorough briefing of resources available at the blog of the skipper of SV DOMINO at dominocatamaran.blogspot.co.nz (click on May 6).

Thanks to M and JP.

 

The Tropics

Nothing much happening at present. We await the onset of the Indian Monsoon. We are in that period where the overhead sun is shifting north from 15N (1 May) to 22N (30 May), or from central India to northern India. Because of the shape of India there is more land under the overhead sun each day, and until the monsoon arrives there is nothing to stop this extra sunshine from turning into heat. Watch for heat wave problems in India this and next week.

Rain maps for the past fortnight from trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif show that the extra convergence zone that has been located between Galapagos and Marquesas is continuing to weaken. No sign of any monsoon over India.

Panama to Galapagos:

Good news. There is a northerly wind expected around Panama on local Monday and Tuesday, should be the best days this week to get off to Galapagos. Maybe the best window for weeks.

 

Travelling to Marquesas:

Also looking good. Winds near Isla Isabela are expected to be OK for departure any day you like this or next week.

There still seems to be some squalls from a convergence zone between 5S125W and Marquesas. These squalls stop a direct voyage. But the good west going current is now best at around 5S. SO take 5S to around 120W and then go direct to Marquesas.

Winds over the Marquesas are expected to be light and variable from this wed local to Tue 17 local. If approaching during this period then come in from NORTHEAST of the Marquesas to get the best of the dying breeze.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

SPCZ is expected to spread all the way from PNG across Rotuma area and then thin out near Samoa but expand again and linger over French Polynesia. It seems to be slowly shifting north.

 

STR= Sub-tropical Ridge

The BIG FAT HIGH to northeast of North Island that dominated last week’s weather is expected to travel off to the east along 35S and fade when is gets east of 120W.

High pressures in the region NE of NZ have been keeping the fronts away from North Island for many weeks, but it looks like this may change this week,

The next HIGH is expected to build to east of South Island on late Monday/Tuesday, after a front peels off to east of the South Island on Monday Morning. This HIGH may bring a ridge of light wins to North Island on Tuesday, and then is expected to travel off to east of NZ.

Another HIGH may travel off central Australia /30S into Tasman Sea and across to north of NZ on Fri/Sat /Sun 13 to 15 May

 

Between NZ and the tropics

Easterly onshore wind over northern NZ on Monday so may as well stay put for that. These are expected to turn northerly by end of Tuesday and for Wednesday as the ridge to the south moves off to the NE. OK to depart in these northerly winds if you are off to Minerva –however, will need to go east at first.

FRONT is expected to cross North Island on Thursday, maybe with strong winds. Avoid.

This front changes the pattern over the North Island and following it there is expected to be a series of trough with strong west to SW winds in the Tasman Sea. The first of these should bring strong and squally winds to Auckland and maybe Whangarei on Friday 13 May, but perhaps just fresh winds to Opua.

A better pattern for departure is likely on Saturday, with just moderate west to SW winds. And then another trough with strong winds is likely on Sunday 15 May

 

>>>>>> 

See my yotpak at boatbooks.co.nz/weather.html for terms used.

See my website www.metbob.com for information on tailor-made voyage forecasts– Feedback to bob@metbob.com. Tell anyone you like that to subscribe they should email me.

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

Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom right to subscribe.

To unsubscribe  send a reply email saying LEAVE.

01 May 2016

BobBlog 1 May 2016

WEATHERGRAM

YOTREPS

Issued 1 May 2016

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

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

Monthly averaged winds:

 

C. M. Risen and D.B Chelton produced the SCOW (Scatterometer Climatology of Ocean winds) at numbat.coas.oregonstate.edu/scow/index.html. Christian Feldbauer of SY PITUFA (currently in Tahiti) has recently made this data available for easier web page viewing at www.pitufa.at/oceanwinds/. He has also (in 2010) made the data available as a kmz file for Goggle Earth viewing

at www.pitufa.at/wp-content/uploads/2010/12/prevailing_ocean_winds.kmz

Thanks Christian

We can compare the May data with what happened with last month’s wind from www.esrl.noaa.gov/psd/map/images/fnl/sfcwnd_30.fnl.gif

And the anomalies from www.esrl.noaa.gov/psd/map/images/fnl/sfcwnd_30a.fnl.html

These maps show that last month the main difference from normal in the Southern hemisphere has been a strange shift to the south and buildup of the “Andes” HIGH located west of South America. There was also a burst of near equatorial westerly winds between Tuvalu and Northern Cooks, possibly an artifact left over by AMOS.

 

The Tropics

Nothing much happening at present.

Rain maps for the past fortnight (from trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif) show that the extra convergence zone that has been located between Galapagos and Marquesas is continuing to weaken. It also shows a weakening of intensity in the South Pacific convergence zone.

 

Panama to Galapagos:

It seems there are still a few yachts interested in this route, so I’ll mention prospects for a few more weeks.

This week the best looking date to go is local Tuesday 3 May/Wednesday 4 May (lighter winds for starters).

 

Travelling to Marquesas:

Now that the convergence zone that was in-between Galapagos and Marquesas is weakening away, the optimal route may be north of the direct route, making use of the strong near equatorial currents. Winds near Isla Isabela are expected to be Ok for departure on local Sunday and Monday and again on local Wednesday.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

SPCZ is expected to be weak and recovering this week, mostly around Tuvalu and Tokelau, but also a branch along 15S from 140 to 165W.

 

STR= Sub-tropical Ridge

The HIGH that crossed the North Island this weekend is expected to linger to NE of NZ and became a BIG FAT HIGH (BFH) until it fades on Friday. This is likely to also form a STRONG squash zone on the north side of the BFH and near southern Tonga especially on Tuesday and Wednesday Tongan dates. Avoid.

Another HIGH is expected to cross South Island on Friday and then build to east of South Island from Saturday 7 May.

 

Between NZ and the tropics

It is not an ideal weather pattern for travelling north from NZ this week, but a reasonable voyage to Tonga can be achieved by going east at first in the northerly flow on the rear end of the BFH. Since the BFH is expected to fade by Friday, that’s when a turn to the north can be taken that will go to Tonga in easterly winds.

At present the outlook for next week is for passing troughs, so not very promising.

>>>>>> 

See my yotpak at boatbooks.co.nz/weather.html for terms used.

See my website www.metbob.com for information on tailor-made voyage forecasts– Feedback to bob@metbob.com.

Tell anyone you like that to subscribe they should email me.

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

Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom right to subscribe.

To unsubscribe send a reply email saying LEAVE.

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