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

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.

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