BOBGRAM issued 3 Nov 2013

WEATHERGRAM
YOTREPS
Issued 3 November 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.

Another quick Weathergram this week.

Last week XTRA changed their email server settings and only allowed bobmcd@xtra.co.nz to send 200 of these emails to my email list of 620. So I resent via bob@metbob.com but several of you do not have that address set on their white list of allowable emails, and would have missed out. I'm hoping tonight's edition gets to you all.

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.

It reached a high of 0.52 on 22 September, and since then has dropped to around zero. On 3 November it has a 30-day running mean of -0.16 , close to zero.

WEATHER ZONES
South Pacific Convergence Zone SPCZ
The SPCZ is expected to spend most of this week north of 15S.

Sub-tropical Ridge STR
The STR has weakened to a few lines mainly along 25S. Between 25S and 45S the South Pacific this week has a near regular steady progression of Highs and Lows, all mainly travelling along 40S.

The Low which is expected over North Island on Wednesday should travel off to the southeast and weaken.

The next High from the west is expected to travel across Tasmania/South Tasman Sea on Mon 11 Nov. This High is then expected to intensify over or just east of NZ early to mid-next week, 12-15 November, and form a squash zone of strong easterly winds between NZ and Fiji /Tonga for a few days. Avoid.

Route Briefings
Between tropics and NZ

Try and time your voyage from the tropics so the arrival tine in New Zealand does NOT coincide with a front or strong winds.

The Low crossing the North Island during mid-week has OK winds in its trough between NZ and the tropics—except that some swell over 3 metres may get as far north as 25S on 6 November.

From 12 November onwards (mid next week) some strong easterly winds are likely between NZ and the tropics because of the squash zone of the north side of a large High. It's too far away to tell exactly at this stage, but this needs to be taken into account by anyone wishing to depart from the tropics late this week, heading for NZ.

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