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

12 April 2009

BOBGRAM7 issued 12 April 2009

WEATHERGRAM

YOTREPS

Issued 12 APR 2009  

Bob McDavitt's ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas come from the patterned world of weather maps, so please fine-tune to your place. Dates are in UTC unless otherwise stated.

 

LAST WEEK

Finally a relatively quiet week in the South Pacific tropics, after the drama of LIN last weekend.

 

TROPICS

The South pacific Convergence Zone SPCZ is not as active as it was a week ago.  There is one branch of activity from the Coral Sea to New Caledonia ad another, coming and going, from Tokelau/ Samoa to Northern Cooks to Marquesas… This branch used to extend to a section between Marquesas and Galapagos, but that section is weakening now.

 

During the coming week not much change is expected to happen in the tropics… There will be some developments in the subtropics with one Low  likely to briefly form south of Niue on Wednesday UTC then head off to the southwest, and another low to form near Lord Howe Island in the Northern Tasman Sea next weekend. Both these lows will “steal wind”, broadening apart the isobars in the tropics immediately to their north. Avoid these lows.

 

SUBTROPICAL RIDGE

The Subtropical ridge line is still at its equinoctial latitude of around 40S.  There is a big fat high BFH mainly over the North island of NZ at present and stretching out along 40S to the east, with a squash zone of enhanced trades on its northern side mainly along 20S from around Kermadecs all the way to about 160E from Monday to Wednesday.  Avoid.

 

 

NZ

The forecast is for the BFH over NZ to be kicked off east by a front arriving over the South Island on Monday and fading over central NZ on Tuesday. Then a new BFH is expected to grow to 1033 near Chathams on Wednesday and to move slowly east over the next few days, as another front moves onto the South Island on Thursday and fades over the central NZ on Friday.

 

This week the fronts will likely be preceded by strong northerlies and followed by westerly winds.

 

 

The terms used are more fully explained in the METSERVICE Yacht Pack.

           More info at http://weathergram.blogspot.com

             Feedback to bob.mcdavitt@metservice.com

 

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