Bob blog 26 June 2016

WEATHERGRAM

YOTREPS

Issued 26 June 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.

Sea Mercy is making good progress in Fiji. Marie Dufour on cat DOMINO has written a blog about conditions and needs in the villages they have visited, read this at  dominocatamaran.blogspot.co.nz/ and read the adventures of SV PERRY at www.svperry.com/2016/06/the-lau-group-fiji.html#more

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In the past week (the week after the winter solstice) there have been some stormy weather around the planet. The monsoon arrived as a burst of thunderstorms in India, with 93 people killed by lightning strikes in 2 days. Bihar, an eastern state was hardest hit, with 59 confirmed deaths… mainly farmers planting rice.

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Monsoon advance as seen at www.imd.gov.in/pages/monsoon_main.php

Heavy rain has also visited South Chia, triggering a fatal tornado /hail storm which claimed 98 lives in east China’s Jiangsu Province. And heavy flooding has brought widespread damage to West Virginia in the United States of North America, killing at least 26 people.

Tropics are still having a cyclone drought. Some tropical lows near and north of the Philippines, otherwise quiet, or so it seems.

Last fortnight of weekly rain profiles shows that the heaviest rain is now shifting east across Vietnam/South China and towards Philippines. That’s normal.

The Tasman Sea area has switched from dry to wet.

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

WEATHER ZONES

Weather Zones (see text) as expected mid-week on Wednesday (GFS model) showing wind, isobars, current, swell black arrows / Sig wave height purple lines, SPCZ and STR.

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SPCZ=South Pacific Convergence zone.

SPCZ is expected to remain draped from PNG across to the Tuvalu/Tokelau area, then to Northern Cooks. The GFS model is picking that a trough may develop on the SPCZ in the Coral Sea around 4/5 July and then move onto New Caledonia/ Vanuatu around 6/7 July, but this is NOT being forecast by the ECMWF model at this stage, so can be treated as a 50% probability.

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This week’s SPCZ as seen on windyty.com

STR= Sub-tropical Ridge

STR is along 25 to 30S in Tasman Sea but more like 35 to 40S east of NZ.

The HIGH that is east of NZ near 40S and south of French Polynesia is expected to travel slowly east along around 40S this week going towards South America.

The next HIGH over eastern Australia on Tue to Thurs is expected to fade as it crosses the Tasman on Friday and NZ on Saturday. It will probably fade so much that it is not going to offer a large enough gap-between-lows for yachts seeking to depart from NZ for the tropics.

Voyage Outlooks:

Tahiti to the west

Satellite imagery shows the convergence zone over Tahiti tonight. This is expected to weaken and shift to the north during tomorrow, bringing strong SE winds and dry conditions to the Borabora to Papeete area on local Monday. From late local Monday these winds should moderate, and then there is likely to be a dry period with light to moderate SE/E winds over the Tahiti area for the next week or mare. That’s a change from the recent wet windy weather in the area.

Since the SPCZ is expected to remain north of 15s, it appears that a voyage to the west should travel along the drier and more settled latitudes near 17 to 19S.

Weather may not remain settled all the way from Tahiti to Tonga, as a weak trough from the SW may travel across Tonga around 1-3 July, followed by SW swells. So it may be desirable to stop at an Island such as Palmerston Island or Niue /Beveridge reef along the way.

Between NZ and the tropics

MAYBE NOT this week (again), may as well stay put (again). A LOW is crossing NZ on Monday, and then a brief ridge on Tuesday. Too brief for getting away, as the next LOW is expected on Wed/Thu/Fri. Then another brief ridge on Saturday followed by a LOW on Mon/Tue 4/5 July, and a front on Wed 6 July. Maybe OK to sail north on Thu 7 July, too far away to tell.

Between Australia and New Caledonia/Fiji

OK, wait for sea to settle after Monday’s Tasman Low, maybe Wed or Thursday.

Then should be Ok to sail to New Caledonia/Fiji.

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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.

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

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