Bob Gram 27 March

WEATHERGRAM

YOTREPS

Issued 28 March 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 El Nino index is relaxing over the past week, as seen at the www.farmonlineweather.com.au Climate site

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And the seas are losing that storage of heat now:

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So the weather pattern in the Pacific is slowly returning to normal.   At present the water surface is sliding downhill from east to west so there is a good west-going current.

Another factor to consider is the extra convergence zone which has been hovering along 3 to 5S between the Galapagos and Marquesas over the past few weeks. To see how this zone is likely to preform over the next week or so, go to www.windyty.com and click on the Rain accumulation and set this to the next 10 days:

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This extra convergence zone marks the north end of the SE trade winds, and there are only light winds between its north-end and the Intertropical convergence zone—- these may be from the west, so are worth avoiding (wind versus current=choppy).

TROPICS :

AT present there is a tropical depression over the sea between South Africa and Madagascar this system is expected to fade in a few days.

A rather weak tropical low is now lingering around the New Caledonia area and by next weekend, 2/3 April, this – or another feature that follows it—may start deepening over Fiji.  SO avoid this part of the South pacific for the next week or two if you can.

The rain maps for the past week or two show an increase in activity around Madagascar and around New Caledonia as well as the ITCZ and the extra convergence zone in the South Pacific Ocean just south of the equator.

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

Panama to Galapagos:

Light winds at present, however, an avenue of useful Northeast winds for this departure seems likely to appear around Mon 4 April. 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. There is a tail current just to north of the equator, but this is becoming random in strength and position—and there may be some near-equatorial westerly winds, so that would place head wind versus current = choppy and uncomfortable.

Better to dive to 6 south, south of the extra convergence zone, then go direct. If a small low does form on this extra convergence zone then it may induce some strong SE winds as far south as 6South, so be on the watch to avoid that.

WEATHER ZONES

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Weather Zones (see text) as expected mid-week on Wednesday (GFS model) showing wind, isobars, Sig wave height green lines, SPCZ and STR.

SPCZ=South Pacific Convergence zone.

SPCZ is expected to spend this week regenerating across the Coral Sea/Fiji area. A smaller branch should bring squally showers between Samoa and Southern Cooks.

That “extra” CZ near 5S between Galapagos and Marquesas is expected to linger for another week.

STR= Sub-tropical Ridge

New HIGH is expected to travel east across Tasmania on Monday and southern Tasman Sea on Tuesday and central NZ on Wednesday and then build as it travels off to the east along 40S.

There is expected to be a squash zone of enhanced easterly / NE winds on the north side /northwest side of this feature, especially next weekend as it travels off to the east of NZ

For NZ and Tasman Sea

A weak trough is forecast to travel across the South Island on Tuesday, and then a HIGH should come from the west and go off to the east. On the back end of that HIGH, a trough in the Tasman Sea is likely to bring some wind and rain to the north end of the country on Fri/Sat/Sun 1/2/3 April.

>>>>>> 

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.

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