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

26 June 2011

BOBGRAM7 issued 26 June 2011

WEATHERGRAM
YOTREPS
Issued 26 June 2011
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 of weather maps, so please fine-tune to your place. Dates are in UTC unless otherwise stated.

TROPICS
Southern Oscillation Index SOI is in neutral territory, staying between 0.26 on 19 June and 0.29 on 26 June.

Galapagos to Marquesas: Slight change. The seas around Galapagos are now getting slightly warmer than normal and the SSE winds there are slightly less than normal. It is making more sense to get west as soon as possible and seek the better winds west of 95W. So just one way point may be all that's needed now…somewhere near 6S 132W and then head for Marquesas. There are some tropical showers 3-5S at 130w.

As for the Panama to Galapagos leg: it is looking better than last week, the ITCZ seems to be a little more north in that area, so it is now a route with light winds, and may be some tail winds on Monday.

South Pacific Convergence Zone SPCZ has reactivated and is mainly draped from Solomons, across Vanuatu and Fiji then to the southeast. There are also some convergence zones over Tuvalu and Tokelau and, unusually, between 2 to 5S from 130w to 160W.

This coming week the SPCZ should stay in much the same place in Coral Sea/Vanuatu, but may drift to north of Fiji with part of it drifting from the south onto Tonga by end of week - and linking with a low or trough that may form around the Kermadecs.

SUBTROPICAL RIDGE STR
New High is taking its time over Australia along 35S, and pushing a tongue across northern Tasman Sea along 30S… this is enhancing the trade winds in Coral Sea into a squash Zone. Fiji MetService has issued a gale warning on this area for tonight.

This high is expected to finally get into the Tasman Sea east of Tasmania at 40S by Tuesday 28 June. This will make for a squash zone between it and a Low that is then expected to deepen in the cold air over North Island. There will be strong SW winds /rough seas / heavy swells in this squash zone and these will travel north and east reaching the area between North Island and Fiji/Tonga on wed/Thu June then ease and move off to the east. Anyone travelling this route may wish to consider waiting until after Thursday for this stretch of ocean to settle.

The high may fade away this weekend with its remnants crossing southern or central NZ, bring frosty air. By early July, a new high cell should form east of NZ along 40S. There will still be a squash zone on the high's northern side: this is likely to re-intensify in Coral Sea over the weekend, but may ease further east.

TASMAN SEA/NZ AREA
The secondary low that crossed the North Island this weekend was cold enough to bring 10cm snow to Ruapehu. There's another of these lows likely to deepen over the North Island on Tuesday—strong cold southerlies for Cook Strait / southern North Island (in squash zone between high and low) and another dose of snow for Ruapehu, especially on Wednesday. This is a typical "Old man southerly", but may be notable as it's the first we have had in a long while.

SAILING TO/FROM NORTHERN NZ.

It may be more comfortable to let this week's Low go first.

As for the next low that may form around Kermadecs early in July: well, still too far away to resolve much detail, but it may be easier to go clockwise around (travelling north) than this Thursday's low, and is NOT expected to have as much strong wind/rough sea/heavy swell.

The terms used are more fully explained in the METSERVICE Yacht Pack.
More info at http://weathergram.blogspot.com
Feedback to bobmcd@xtra.co.nz

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