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

27 November 2016

Bob Blog 27 Nov

WEATHERGRAM
YOTREPS
Compiled 27 November 2016
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.

The Tropics
A tropical low formed in Coral Sea last week and faded as it travelled southward
to west of New Caledonia.
We start this week with another tropical low in the Coral Sea, and this one is
likely to fade somewhere near New Caledonia mid-week. It has been picked up in
the tropical tidbits web site and here is its likely track according to some
weather models, as seen at
www.tropicaltidbits.com/storminfo/96P_tracks_latest.png

Fiji Met service is watching another tropical low tonight located near
Rarotonga.
Their latest idea on its future can be downloaded from
www.met.gov.fj/aifs_prods/20036.txt
>>>>>>>>>>>>>>>
Tropical Disturbance Summary For area Equator to 25S, 160E to 120W
ISSUED FROM RSMC NADI Nov 270833 UTC.

TROPICAL DISTURBANCE 02F [1006HPA] WAS ANALYSED NEAR 20.0S 164.0W AT
270600UTC.
TD02F MOVING SOUTHEAST AT ABOUT 07 KNOTS.POSITION POOR BASED ON
HIMAWARI-8 AND GOES IR IMAGERY WITH ANIMATION AND PERIPHERAL
OBSERVATIONS. SST AROUND 27 DEGREES CELCIUS.

CONVECTION REMAINS PERSISTENT NEAR LLCC. ORGANISATION REMAINS POOR.
CIRCULATIONS EXTENDS UPTO 700HPA. TD02F LIES JUST EAST OF AN UPPER
TROUGH IN A MODERATE SHEARED ENVIRONMENT.

MOST GLOBAL MODELS HAVE PICKED UP THE SYSTEM AND MOVE IT TOWARDS THE
SOUTHEAST WITH SLIGHT INTENSIFICATION.

POTENTIAL FOR TD02F TO DEVELOP INTO A TROPICAL CYCLONE IN THE NEXT 24
TO 48 HOURS IS LOW.

*********************************************************************
NO OTHER SIGNIFICANT TROPICAL DISTURBANCE ANALYSED OR FORECAST IN THE
AREA.
>>>>>>>>>>>>>>>>
Rain accumulation maps from
trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif show easing
activity around French Polynesia, continuing activity in the Coral Sea area and
around central America, and an increase in activity over equatorial Indian
Ocean. The burst of rain west of Hawaii from a rather peculiar moving tropical
depression.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
The tropical low near Rarotonga is expected to move off to the SSE and deepen
near 30S. It is expected to "steal" the winds from the French Polynesia
/Southern Cooks area and should leave behind a lingering convergence zone.
Another tropical low is in the northern coral Sea and is expected to go Se and
fade around the New Caledonia area around mid-week. Worth watching as this is a
system that may need to be avoided.
The SPCZ around Tuvalu and Tokelau may drift southwards this week, and remain
intense. There could be convective showers over Samoa and Fiji by end of the
week.
Tropical accumulated rainfall for next week may be seen at windyty.com

Subtropical ridge (STR)
The subtropical ridge are continuing to be well defined and reasonably wide,
allowing anticyclones to migrate easterly in a patterned fashion.
The HIGH which is in the western Tasman sea tonight is expected to travel east
along 30/33S this week crossing northern NZ on Tuesday /Wednesday. There may be
a squash zone of enhanced westerly winds south of this high, especially until
Tuesday, but it seems to be reasonable on north side of this high.

Another High is expected to follow across the South Tasman Sea on Tue and Wed
and then stall over central NZ on Thursday and Friday, and move off to east of
NZ this weekend.

These subtropical highs offer reasonable weather for any yachts still seeking to
get from tropics to NZ/Australia, however there are light winds in the centre of
the ridge, and there are troughs in-between the ridges, so travelling in the
winds around the back side of a passing ridge may require sailing thru a
trough-that's OK if you do it at a good latitude mid trip, but may be
disconcerting if both you and the trough arrive at the destination the same day.


Tasman Sea/NZ Area troughs.
Strong westerlies over NZ on Monday and Tuesday, then the next trough should
arrive over the weekend and linger over North Island early next week.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
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