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

19 June 2016

Bob Blog 19 June

WEATHERGRAM
YOTREPS
Issued 19 June 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 winter solstice is upon us. The sun "stands still" at 1034UTC on 21 June.
This is when its declination (as seen from earth) is most south and it "stands"
before turning north. It's the longest night/shortest day and one of the four
turning pints of the year. Yet meteorologicaly it has very little meaning and is
really the START of the three coldest months in the southern hemisphere. The
coldest time of the year is usually 6 weeks AFTER the solstice: hence the saying
"when the days start getting longer, the dawns gets colder".
Enough misery, now for some GOOD news.

El Nino continues to fade
The heat stored in the top layers of the sea over the eastern equatorial Pacific
has been steadily dropping and is now almost in the NEUTRAL range. The monthly
NINO3.4 graph at www.farmonlineweather.com.au allows us to compare the recent El
Nino with the previous "big one" of 1997/98. Our recent El Nino has lasted
longer and was slightly stronger. Curious climatologists are thinking this is
part of a trend, but it is difficult to tell.
The SOI index has also been in the NEUTRAL zone for the past two weeks.


Tropics are still quiet- maybe a drought of cyclone?
India's monsoon is making progress, but still around 10 days behind schedule.
Last fortnight of weekly rain profiles from
trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif shows that the
heaviest rain is now shifting from Myanmar/Burma to Vietnam/South China. That's
normal.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ is expected to remain draped from PNG across to the Tuvalu/Tokelau area,
then Northern Cooks to Tuamotu Islands. The zone currently has a break in it
over Suwarrow, but that is not expected to last long. See windyty.com an select
rain accumulation next 10days.

STR= Sub-tropical Ridge
STR is along 25 to 30S in Tasman Sea but more like 35 to 40S east of NZ.
The HIGH that is east of NZ tonight is expected to travel slowly east along
around 40S this week then go NE next week towards 30S. There is expected to be a
squash zone between this High and the low on its northern side, but this is only
expected to affect sailors in-between NZ and Tahiti.

Voyage Outlooks:
Tahiti to the west
A trough is approaching Tahiti with NE winds preceding it, so best wait for it
to come and go and depart around wed/Thu 22/23 June local. Such a voyage should
have OK winds, but may encounter some squalls around 27 June local. Too early to
tell for sure, for sure.

Between NZ and the tropics
NOPE. NOT this week, may as well stay put. The NE winds that precede the next
trough are expected to spread onto Northland from Monday, then the trough on
Wednesday, and another on Saturday, this is OK for those going east to Tahiti,
but NOT for anyone going to Tonga/Fiji/New Caledonia/Australia. May as well do
something else.

Between Australia and New Caledonia
YEP. OK, wait for sea to settle after Sunday's night trough, then should be Ok
to sail to New Caledonia. But make it quick, as the next rough is likely over
Queensland by Friday
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See my yotpak at boatbooks.co.nz/weather.html for terms used.
See my website http://www.metbob.com for information on tailor-made voyage
forecasts- Feedback to bob@metbob.com. Tell anyone you like that to subscribe
they should email me.
Weathergram text only (and translator) is at weathergram.blogspot.co.nz.
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