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

09 October 2016

Bobgram 9 October 2016

WEATHERGRAM
YOTREPS
Compiled 9 October2016

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.

FLEET CODE
Back when I was a boy the FLEET CODE was established allowing a weather map to
be sent to the whole Fleet all at once via Morse code transmitted over
Shortwave. In this age of readily available GRIB data (from some models) the
FLEET code has fallen off the back shelf of technology. However, the Fiji Met
Service are still manually converting their analysis map into fleet code and,
thanks to Mike Harris of Pangolin and the people at saildocs these maps can be
downloaded as email and drawn on your own computer as you travel around the
South Pacific.

They have an advantage over GRIB files in that they contain convergence zones,
as seen by Fiji Met Service meteorologists using satellite imagery to fine tune
placements.
To download the latest Nadi Fleet code send an email to query@saildocs.com, no
subject needed, saying SEND nadi-fleetcode.
When you receive the reply email, use something such as notepad to save the data
as a file and store this, say, on your desktop, as, e.g. fleet.txt
Mike Harris' PANGOLIN website contains a page which allows you to save a beta
version of PhysPlot. Go to www.pangolin.co.nz/physplot . This is a windows
program physplot.exe (now called a desktop ap) which can open that file
fleet.txt and turn it into a weather map for you.
Tonight's situation on Fleet map shows a convergence zone north of Fiji shifting
south, and a weak trough has been drawn over Fiji.

The Tropics
Tonight in the Atlantic, TV MATTHEW, after hitting Haiti hard last week, has
finished grazing the east USA coastline and is now moving east out to sea. TC
NICOLE is on the SE side of MATTHEW. See ruc.noaa.gov/tracks/

And in the Pacific TC SONGDA is likely to recurve soon, but TC AERE in the China
Sea may make landfall over Vietnam, rather an usual event.


Rain for the past fortnight as seen at
trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif
shows an increase in convection Christmas Island area to NW of Australia, and in
the South Pacific, especially to north of Fiji. MATTHEW's rain-footprint stands
out clearly.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ this week is expected to congeal into a wet trough over Fiji during Monday
= Fiji Day. A Low may form over the Lau group late on Monday, bringing some
strong winds and squally rain to Tonga on Monday night and Tuesday. Avoid.
This Fijian trough is expected to spread westwards, so that a zone of LIGHT
WINDS is expected over western Fiji to Vanuatu. Not good for sailing.
So the South Pacific convergence zone this week goes thru a period of
intensification, then congealment (over Fiji) and then a venting of its energy
off to the southeast. This pattern is consistent with the arrival of an MJO
(Madden Julian Oscialltion) in the South Pacific , as seen at
www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_mjo_index/mjo_index.html
When the blue shaded area in this MJO time/latitude cross section enters the
South Pacific we tend to see tropical lows. Note that these MJO arrivals occur
once every 4 to 8 weeks at this time of year, but may be more regular during the
coming cyclone season. Worth watching.

Subtropical ridge (STR)
This is expected to remain weak and further north than normal along round 25S
between Australian coast and 180. Further east it should spread south. No squash
zone this week.

Travel from Tahiti to Tonga:
Winds may be Ok for a departure on local Sunday, then just light winds are
expected over Tahiti area until next week,

Travel between the Tropics and NZ:
Light winds over western Fiji and Vanuatu area this week, so maybe stay put and
wait for trade wins to return.
There is a Low affecting Tongan area on Monday/Tuesday, then light variable
winds for the remainder of the week. So maybe wait for something better.
If you are already on your way to NZ then be mind-fall that a LOW from Tasman
sea is likely reach northern NZ around Sun 16/Monday 17, and another maybe
around Thu 20/Fri 21 Oct. try and avoid these dates for arrival, but these are
provisional and may change, so also seek an update.

Travel between New Caledonia and Brisbane area:
Weak trough is expected to cross Brisbane area on Tue 11 Oct. followed by a few
days with southerly winds. This trough should spread east reaching New Caledonia
around Sat 15 Oct and then lingering there until Sunday 16 Oct
No strong winds expected with this trough so maybe Ok to sail thru it, but not
100%.
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See my yotpak at boatbooks.co.nz/weather.html for terms used.
See my website www.metbob.com for information on tailor-made voyage forecasts-
Feedback to bob@metbob.com.
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