BOBGRAM issued 27 Jan 2013

WEATHERGRAM
YOTREPS
Issued 27 Jan 2013
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.

The Atmosphere: The Southern Oscillation Index or SOI (30 day running mean) was hugging the plus 0.5 value in Sep Oct Nov, during December it dived to almost minus 1, but in January it has relaxed and is, on the 27th, near zero.

The Ocean: Sea surface temperatures across the equatorial Pacific act as a thermostat for the planetary weather engine. When they are different from normal we get a change in clouds around the equator and this changes the earthly wind zones and has an impact on the latitude zones of weather across the whole Pacific.

Well, in the past month the SST in this target zone has mostly been around normal, and so the oceanic pattern is neither El Nino, nor La Nina; it remains neutral.

WEATHER ZONES
The monsoonal trough over central Australia continues to have little cloud and rain—this is why much of the Australian continent is being baked in the sun. Queensland managed to briefly brew tropical cyclone OSWALD. Its remains are still bringing wind and rain. It's remains should move off to the south by Wednesday.

The main convection of the ITCZ is over Indonesia – north of its normal position at this time of the year - over the Timor sea and northern Australia. It extends into a South Pacific Convergence Zone SPCZ between 5 and 10S from Papua New Guinea to Northern Cooks. This convergence zone spirals into TC GARRY which is over Southern Cooks. This is expected to wander off to the SE, but another tropical depression is likely to quickly replace it in the zone between Samoa and Southern Cooks later this week.

We are now entering the business period of the Tropical Cyclone season and another Tropical depression may form out of the convection cloud that is sitting near 20S to South of Fiji. This is expected to be a slow-moving system

TASMAN SEA/NZ TROUGHS
Large High is blocked just east of NZ .. it exit route to the east is cut off by remains of TC GARRY until Wed 30 Jan. This High should then move off by Sat 2 Feb and allow a new Low to develop in the Tasman Sea on Thursday 31 /Fri 1Feb and move across South Island on Sun 3 Feb followed by another High.

These HIGHS are expected to maintain strong easterly winds and moderate to heavy easterly swells over northern NZ for the next week of two. These may be OK for Auckland Anniversary Regatta on Mon 28 Jan, but not OK for going fishing off northern NZ this week.
However, the blocked HIGH does allow summer sailing around central NZ until Wed 30 Jan.
Enjoy.
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