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

31 August 2008

BOBGRAM7 issued 31 Aug 2008

Issued 31 August 2008 NZST
Bob McDavitt's ideas for South Pacific sailing weather.
(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

South Pacific Convergence Zone SPCZ is building in strength over Papua
New Guinea and Solomons. Further east there are two branches-one from
Tokelau to Northern Cooks along around 10S, and t'other sort of in the
Tonga/Kermadecs region, stretching east along 20/25S to a peak south of
French Polynesia.

The pattern is dominated by the Big Fat High BFH east of NZ this
weekend. It is rare to find a 1040+hpa anticyclone in our part of the
world - I can't seem to find a tele-connection between it and GUSTAV in
Gulf of Mexico, suffice it to say that planet Earth is going through
some extreme weather at present. We in MetService have a saying, when
High above 1030, weather will get dirty... so when High above 1040,
weather will get naughty. The squash zone between this High and the low
that will form on its NW shoulder (as they do) will be particularly
intense over the Kermadecs area on Monday and Tuesday. Fiji Met has
already issued a gale warning on this.

The Low that forms south of Fiji/west of Kermadecs on Monday is forecast
to wander south/southeast to east of Chathams by Sat 6 Sep as the High
wanders east. There's another squash zone on the north side of this
High, and it'll reach its peak over Southern Cooks on the 6/7 Sep
weekend UTC w and strong easterly winds from Tuamotu to Southern Cooks
and with 4m+ swells around Southern Cooks . AVOID.

Next trough rolling in from Tasman Sea is a trough between two Highs, so
this is a new pattern for us - a change from those lows that have been
forming in Tasman Sea and dumping rain on us. The trough should bring
rain to western South Island and gusty NW to eastern NZ from Mon to Thu
---stalling a while as a secondary low forms near Brisbane--and finally
secondary low and trough should cross the North Island on Thu and Fri
and maybe Sat and Sun. Avoid departing/arriving Northland Thu-Sun.

Sailing NZ/Fiji, Tonga? Wait until the Low has gone, after 4 Sep.
Sailing NZ/Noumea, looks OK.
Sailing Eastern Aussie? Not good this week, wait for that Low off
Brisbane has gone.

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