Translator

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

24 April 2016

Bob Blog 24 April 2016

WEATHERGRAM

YOTREPS

Issued 24 April 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:

Cyclone FANTALA is now weakening but developed to produce winds up to 150 knots (173 mph) on Monday, surpassing the 145-knot (167 mph) barrage of GONU (2007). And so FANTALA now holds the record for the strongest Indian Ocean Cyclone on record. Its track did go SE for a while then reverted to NW.

Another system that has had a peculiar track is TC AMOS. In my last weathergram it was TD17F bringing heavy rain to Fiji:

When TD17F developed into TC AMOS (between Rotuma and Wallis Islands) it was forecast to travel to south coast of Samoa and peak on Saturday night/Sunday morning (local date).

Well, AMOS didn’t do as it was ‘told’, and during Saturday changed direction for Samoa’s north coast, and peaked earlier than expected, thus not living up to its full potential. Something like a typical teenager.

TC AMOS is now turning to the south and well to the southeast of Pago Pago.

It brought a brief burst of wind to Pago and, from the wind record we can see that it travelled southeast around the northeastern side of Pago.

My link from www.aviador.esshows a wind change from NE to SW observed at Pago, peak gust 47 knots.

 

Will TC AMOS be the last cyclone of the season?

NOMINALLY the start of May is the end of the cyclone season. And NORMALLY, even though the sea surface temperatures under the South Pacific Convergence Zone are warm enough to trigger cyclones all year round now-a-days, May to October are USUALLY cyclone free, HOWEVER, We had Cyclone RAQUEL last June/July, and tropical depressions can form in any month with squalls that have gale winds, SO it is wise to remain vigilant, to anticipate gales in the South pacific during any month of the year, AND get real weather updates to help AVOID the worst for your voyage.

With WINSTON and then FANTALA both breaking records, there are some saying we have gone past the tipping point and can now expect more extreme storms more often – well that’s just extreme talk, and we are now here entering the quieter time of the year, and its getting colder by the week in the non-tropics of the South Pacific, SO let’s take our opportunities and go SAILING into the tropics. That’s what we are on planet earth for.

 

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 showing signs of weakening. It also shows the heavy rain of AMOS and FANTALA.

 

Panama to Galapagos:

Just headwinds this week. It is possibly too late now to get a good voyage to Marquesas. If anyone is still waiting then let me know.

 

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 from local Tuesday, but rather light before then.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

SPCZ is expected to be weakened this week as TC AMOS takes a lot of energy away.

However there is still plenty of activity around Tuvalu and Southern Cooks/parts of Tahiti.

 

STR= Sub-tropical Ridge

This week’s Tasman Sea High is further north than last week’s, a sign that we are getting closer to winter. It left New South Wales today and is expected to travel slowly across mid Tasman Sea and weaken over the North Island around Friday. By then, another more southern high is expected to build east of the South Island and then travel northeast across Chatham Islands on Saturday.

There is expected to be a weak squash zone on the north side of this week’s HIGH — north of 30S on Monday and travelling further north and fading over New Caledonia on Wednesday/Thursday.

 

Between NZ and the tropics

It is a good week of opportunity for going north out of NZ. There may still be some left-over slop in the sea state on Monday, but Tuesday/Wednesday looks great for departure to the tropics. There may just light winds for starters from Thursday until end of the week, and the next passing front in the Tasman Sea is expected to reach from Noumea to Northland by 4 May, so you should attempt to depart before 1 May to avoid its worst—and then again it may be less than strong north of 30S.

After 1 May the next window is likely, at this stage, to be around 10 May. May be better to go this week than 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 send a reply email saying LEAVE.

 

 

22 April 2016

TC AMOS update

On Saturday morning (Fiji/NZ/Samoa date) (22 2037 UTC)

AMOS was over open sea north of Wallis Island

and seems to be heading for south coast of Samoa on Sunday night.

 

Its centre may miss making “landfall” but the ring of its strongest winds are likely to affect both Savai’i and Upolu

 

The combination of steep hillsides and heavy rain is likely to produce significant landslides, especially on those hills facing the incoming wind---and in this case ,  that’ll be a wind from the northwest.

 

Brace accordingly .

 

For latest official track map go to www.met.gov.fj/aifs_prods/65648.html

 

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

20 April 2016

TC AMOS

TD17F  has managed to find its way over warm open seas so that it can deepen sufficiently to have gales around its centre and thus satisfy the criteria to be named as a TROPICAL CYCLONE, TC AMOS.   The  future track of AMOS is still somewhat at the whim of its surroundings -- however it does now appear be in a north-westerly steering field .

 

Fiji Met service this morning  (Thursday  21 May Fiji date) produced this graphic of its probable future, heading towards southern parts of SAMOA.

 

See  met.gov.fj/aifs_prods/65661.html or wp.me/p2CxPj-OX

 

17 April 2016

Bob Blog

WEATHERGRAM

YOTREPS

Issued 17 April 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.

 

How is El Nino doing?

The Southern Oscillation average for the last 30 days on 14 April was minus 0.98 compared with a reading of minus 2.4 in mid-March

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

 

Over the past month, the data shows that trade winds close to the equator have actually been slightly STRONGER than normal. The trade winds in the southern Pacific Ocean have been reaching as far as 3S. However there has been a convergence zone between Galapagos and Marquesas. There has also been a puddle of calm between Panama and Galapagos.

Wind averages and anomaly for past month from www.esrl.noaa.gov/psd/map/images/fnl/sfcwnd_30b.fnl.html

 

The TOA data for yesterday does show a slight westerly anomaly along the equator—but only from 180 to 160W and not enough to cancel out the trade winds. See www.esrl.noaa.gov/psd/map/images/fnl/sfcwnd_30b.fnl.html

 

The Tropics:

Cyclone FANTALA has an eye and is re-curving off the northeast end of Madagascar, so is expected to track to the southeast and weaken.

Track can be seen at www.tropicaltidbits.com

 

A tropical depression TD17F is travelling southeast tonight across Fiji, and brought them heavy rain over the past few days. Models have different tracks for it, and it seems likely to linger in the Fiji area this week and may do a counter-clockwise loop to north and then northwest of Fiji and then travel east and then southeast. Avoid.

 

Rain maps for the past fortnight show that the extra convergence zone that has been located between Galapagos and Marquesas is showing signs of weakening. See  trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

Panama to Galapagos:

There may be northerly winds to assist departure until local Wednesday, then SW headwinds are expected to reach Las Perlas.

South of 6N there are expected to be SW winds all week.

 

Travelling to Marquesas:

This looks like a good week to take off, with SE winds 8 to 10 knots locally around Galapagos and with that convergence zone in-between Galapagos and Marquesas clearing east of 110W.  A good idea to go via 7S or 8S at 110W so as to avoid squalls.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

SPCZ is expected to spend this week very active between Samoa and Tahiti

 

STR= Sub-tropical Ridge

High is expected to spread from Tasman Sea across central NZ from Monday to Wednesday.

There is expected to be a squash zone of enhanced easterly winds on the north side of this feature on Wednesday

Another High is expected to travel over southern NZ / Chatham Islands from Wednesday to Friday.

 

For NZ and Tasman Sea

First week of the school holidays is looking good. Next trough is expected to reach South Island on Friday and bring a southwest change to remainder of NZ on Saturday.

>>>>>>

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.

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

10 April 2016

Bob Blog 10 April

WEATHERGRAM

YOTREPS

Issued 10 April 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.

 

 

10th of April is a date marked in the heart of my generation of kiwi as being the anniversary of the ‘WAHINE” disaster.

On that date in 1968,48 years ago, the low that was once Cyclone GISELLE re-intensified near central NZ, resulting is large winds and swells that washed our Inter-Islander ferry ‘WAHINE”, with 734 people on board, on to the rocks near the entrance of Wellington Harbour. The storm peaked during the morning, and WAHINE took on water and dragged its anchors, and was pushed into further rocks. The winds started easing during the afternoon, and the ‘Abandon ship’ order was given at 1.30pm. The ship sunk in 12m of water at 2.30pm (no-one then on board). 51 died in the sea that day, 1 died a few days later, and another died of related wounds in 1990 taking the WAHINE death toll to 53. There were 3 other victims that day due to Cyclone Giselle itself.

See www.nzhistory.net.nz/culture/wahine-disaster for more information.

 

The estimated wind speed around Wellington during WAHINE storm, may be seen at www.gapwind.org/southeast-directions-over-study-area

Cook Strait is a gap with the Southern Alps to the SW and North island ranges to the northeast, and, as the saying goes, the wind gallops thru gaps.

 

EXTRA CONVERGENCE ZONE

That ‘extra convergence zone’ which has been between Galapagos and Marquesas since the equinox is STILL expected to affect travellers along this route for the next week.  Best seen on windyty.com using the rain accumulation of next ten days setting.

This extra convergence zone marks the north end of the SE trade winds, and there are only light winds between it and the Intertropical convergence zone, so that area is worth avoiding. Thus the best path at present from Galapagos to Marquesas is to find a gap and get south of the extra convergence zone.

 

EL NINO REVIEW

The heat content in the eastern equatorial Pacific (sea surface temperature) is now easing steadily and is on track to get back to normal levels by end of May.  This is shown by the NINO3.4 index as seen at

www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=nino34&p=monthly.

This graph shows how this El Nino episode compares with the last grand event in 1997/1998.

Switching to a weekly time scale, the Southern Oscillation Index SOI (taken from the atmosphere) is also rapidly relaxing, as seen at www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi&p=weekly

 

Over the past month the average winds in the equatorial Pacific have been reasonably close to normal, with no sign of any ‘equatorial westerlies’ and the trade winds also look normal in the northern Pacific and southeastern pacific.  Hopefully this means the ‘extra convergence zone’ will slowly disappear soon.  View average winds at

www.esrl.noaa.gov/psd/map/images/fnl/sfcwnd_30b.fnl.gif

 

TROPICS

AT present there are no cyclones around.  There is a tropical depression in the Indian Ocean which may go west and recurve over Mauritius.

Rain maps for the past week or two, as seen at trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif , show that the extra convergence zone has become stronger last week. The path of tropical cyclone ZENA just south of Fiji stands out clearly.  And Australia remains dry.

 

Panama to Galapagos:

The last day in this current period of good winds for departure is expected to be this Monday (local), and the remainder of this week is expected to have winds too light for sailing away from Panama Outlook is for light winds next week too.

Convection can be seen in the windyty.com rain accumulation map to be strong to west of 80W so best to divert form the direct route around this, using way point 5N 80W and so going via Isla del Malpelo.

 

Travelling to Marquesas:

Light winds around Galapagos. The west-going current near the equator now only goes to 110W and into an area of light winds, so is not the way to go. Between Galapagos and Marquesas is the extra convergence zone with tropical squalls—this has wind, but is not the way to go. SO, look for a gap in the squalls and get to south of the convergence zone, maybe 9 or 10 South and then go west. OR wait, as things may change next week or the week later.

 

WEATHER ZONES

 

SPCZ=South Pacific Convergence zone.

SPCZ is expected to spend this week active across the Coral Sea to northern Vanuatu to Fiji /Samoa area to between southern cooks and Tahiti. There are signs this zone may travel south late in the week onto Tonga. And computer models are picking that weak tropical low (central pressure around 1005 hPa) may form to NW of Fiji my mid-week and travel southeast across the Fiji area this weekend--- this low may (perhaps) bring another dose of rain to Fiji, and is likely to bring a relaxing of the fresh to strong trade winds there until Friday.

 

STR= Sub-tropical Ridge

New HIGH is expected to travel east across Tasman Sea on Wednesday and northern NZ from on Thursday to Monday. There is likely to be a zone of enhanced easterly winds on the north side of this HIGH.

 

For NZ and Tasman Sea

A trough is forecast to travel northeast across NZ from Monday to Wednesday, associated with the passage of a southern ocean low eastwards well south of NZ.

This is occurring at the same time that SAM, as measured by AAO, is expected to dive negative for the first time since last December. This means the following southerly winds may being noticeably colder air.

To see the AAO go to  www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/aao/new.aao_index_ensm.html

>>>>>>

 

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.

 

03 April 2016

bob blog 3 april

WEATHERGRAM

YOTREPS

Issued 3 April 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.

 

Congratulations to Donna Lange, who has successfully made it to Panama (29 March local) after her Yacht, Inspired Insanity, suffered two knockdowns and damage mid-February when about a week away from Cape Horn. Donna had to do the leg to Panama without any communications on board. You can read about her adventures at www.sailblogs.com/member/sailtwicearound/ (click on a recent blog and then keep clicking older at top right of blog window to get to the blogs on arrival).

 

That ‘extra convergence zone’ which has been between Galapagos and Marquesas since the equinox is STILL expected to affect travellers along this route for the next week.  Best seen on windyty.com using the rain accumulation of next ten days setting:

This extra convergence zone marks the north end of the SE trade winds, and there are only light winds between it and the Intertropical convergence zone—- these may be from the west, so are worth. Thus the best path at present from Galapagos to Marquesas is to get south of the extra convergence zone.

 

MARCH REVIEW

The averaged isobars of March show a strong subtropical ridge over the oceans in both hemispheres, with anomalously high pressure centres over North sea and Korea in northern hemisphere and dotted along the Southern hemisphere subtropical ridge and over South America.  This can be seen at www.esrl.noaa.gov/psd/map/images/fnl/slp_30b.fnl.html

The map shows how New Zealand was often afflicted with “eggbeater NE winds” caught in-between the rotating wind around a large High to the east and a low over the Tasman Sea.

 

TROPICS

AT present there are no cyclones around. But there are two tropical depressions on the South Pacific Convergence zone between Vanuatu and Fiji:

This duet of tropical lows are currently deepening and have a moderate chance of becoming tropical cyclone with gales (at least) near their centres by Wednesday mid-week. TD 14F is also known as 96P to Guam and they have produced an ensemble of possible future tracks . This can be seen at www.tropical tidbits.com

These systems are moving quite quickly so are not expected to affect any particular spot for long, but are likely to being squally weather to Fiji especially on Tuesday and Wednesday local.

 

The rain maps for the past week or two show that the extra convergence zone is starting to weaken from its western side. And Australia had a dry week last week.

Rain for the past fortnight may be seen at trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

 

Panama to Galapagos:

After a period of light winds, the forecast is for good NE winds from local Monday to local Saturday this week. Convection is mainly around 4 to 6N and mostly west of 85W so not much of a problem. No real advantage this week in going via Isla Del Malpelo, so may as well follow the current to 4deg N 83W then go direct. This waypoint may vary, so email me if you’d like a tailored waypoint.

 

Travelling to Marquesas:

Light winds around Galapagos. The west-going current near the equator is becoming random in strength and position—and the winds in-between the ITCZ and the extra convergence zone are light and variable, sometimes westerly, so those factors rule out that route. Going direct means encountering squalls in the extra convergence zone, not a good idea. SO the way to go is to get south of the convergence zone and skirt its southern edge.

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

SPCZ is expected to spend this week very active from Solomons to northern Vanuatu to Fiji /Tonga area, with north edge near Samoa. Keep watch for there may be two tropical cyclones by mid-week, travelling SE across southern Fiji/Tonga.

 

STR= Sub-tropical Ridge

New HIGH is expected to travel east across Tasman Sea on Monday/Tuesday, and central NZ on Wednesday then split into two centres, one fading over northern NZ by weekend and t’other travelling east along 45S.

 

For NZ and Tasman Sea

A trough is forecast to travel across the Tasman Sea and deepen as it crosses the South Island on Thursday, then weaken as it crosses the North Island on Friday, followed by decreasing southerly winds.

 

>>>>>> 

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.

 

Blog Archive