BOBGRAM issued 12 Jan 2014

WEATHERGRAM
YOTREPS
Issued 12 January 2014

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.

SOI The Southern Oscillation Index SOI (30 day running mean) sums up the weather pattern
over the South Pacific as one number. It is based on the standardized difference in the
barometer readings between Tahiti and Darwin.
SOI has dropped recently and is now slowly rising. Its 30-day running mean was plus 0.16
on 12 Jan.

TROPICAL TOPICS-
Tropical cyclone IAN brought damaging wind and waves to islands in the Ha'apai Group of
Tonga last night and is now being captured by a mid-latitude trough and shunted to the
southeast. It is expected to wind down as it encounters cooler seas.

There is also a Cyclone in the Indian Ocean called COLIN. It is travelling SW and expected
to re-curve to the SE near 25S.

WEATHER ZONES
South Pacific Convergence Zone SPCZ
TC IAN was the product of a burst of convective activity that came from the Solomons.
Another burst of activity can be seen currently over northern Australia forming the
Intertropical convergence zone there. This burst is expected to travel south onto
Australia from Wednesday-forming a tropical Low over NW Australia. The burst should also
spread into the Coral Sea and activate the SPCZ there- A tropical low is expected to form
in the Coral Sea by Friday 17 January and is likely to move towards NZ North Island next
week. Watch out for this low.

Sub-tropical Ridge STR
The STR is in its typical summer position across the Southern Bight and the Tasman Sea.
The High that is currently in the Tasman Sea is expected to stay put until Friday and then
weaken as it crosses the northern North Island on Sat 18 Jan.

Tasman Sea /New Zealand
Troughy. One trough is moving across the North Island on Monday and another on
Thursday/Friday, both followed by SW winds - not very summery this week.

See my yotpak at boatbooks.co.nz/weather.html for terms used.
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