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

09 January 2010

BOBGRAM7 issued 10 Jan 2010

Issued 11 Jan 2010
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.

A new Madden Julian Oscillation of extra convection is making its way
eastwards across Northern Australia, It almost triggered a tropical
low last Mon 4 Jan, but that bunch of cloud went for a visit into the
Aussie interior instead bringing them some welcome rain, but helping to
displace some desert air towards the south Coast (Melbourne and Geelong
hit the low 40s over weekend).

Some souped-up activity is expected to move into the Coral Sea this
week. There is already a branch of the South Pacific Convergence zone
in the Coral Sea and I think this will start breeding low pressure areas
by the 16-17 Jan weekend. Watch this space.

The South Pacific Convergence zone SPCZ started last week in a zone from
Samoa to the French Polynesia FP area. Mid=last-week a low formed over
Southern Cooks, as mentioned in last week's Weathergram, and moved off
the southeast. The cooler drier southerly flow and rising pressures on
its western side has dried out the SPCZ between FP and Fiji for a few
days, but a new zone is now slowly forming along 10S.

After a week or more of strong subtropical ridges, we may now be due for
a week or so of weaker ridging in the Tasman Sea area.

The High well east of NZ at 170W today should remain strong centred
south of 45S and drift to around 150W by the 16-17 Jan weekend, with
enhanced trade winds returning to the Southern Cooks to Tonga area as a

The next-high-to-the-west: over Tasmania today, is expected to just move
north and fade over the Lord Howe area on Thursday 14 Jan. A new high
should then bud across Tasmania and bring another dry weekend as it
crosses northern NZ on 16-17 Jan. As this high moves off next week: IF
the resulting falling pressure coincides with one of those lows or
troughs that may form in the Coral Sea, then there is a likelihood of
some rain from the subtropics reaching Northland where it is needed, but
too far away to be sure yet.. more in next weathergram.

Unsettled: A LOW has formed east of Otago on today's front: it should
bring cold (and maybe damp) southerlies to eastern areas until
Wednesday. Then the next front should move onto the South Island on
Thursday, and develop a low east of Canterbury on Thursday night (local)
with damp cold southerlies for eastern areas until Saturday.

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