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

03 July 2016

Bob Blog 3 July 2016

Issued 3 July 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.

Back in the early 70s when I was a university student working at New Zealand
Meteorological Service I was asked to help Edith Farkas with her study of
observations of deplenishing amounts of ozone in the stratosphere. She was a
good example of how it was possible to be a woman meteorologist in New Zealand
even then---
These studies resulted in the Montreal Protocol in 1987 whereby the UN banned
the use of CFCs as a refrigerant. The Ozone hole peaked in 2000, and has had
minor drops ever since, increasing briefly in October 2015. A news release this
week announces that new studies of the data shows that increase was caused by
the eruption of the Chilean Volcano Calbuco, and the hole is actually on "a path
to heal". The Montreal protocol is a beacon of hope for us humans on this
planet, a sign that we can indeed terraform beneficially.

This year is turning out to be the warmest on record--- a good discussion on
this and other weather topics is given by MetService Severe weather forecast
Eric Brenstrum at'-science-wor

Tropical cyclones are starting to form.
AGATHA and BLAS are storms in the northeast Pacific that have formed on the
Intertropical Convergence zone west of Mexico. These two storms are expected to
go off to the northwest, but they may be followed by a third storm forming this
weekend that may go westnorthwest all the way to Hawaii area by end of next
And NEPARTAK is a storm in the NW pacific to south of Guam moving northwest
towards Taiwan.

Last fortnight of weekly rain profiles as seen at
shows how the Intertropical convergence zone is now intensifying over the
eastern pacific.
Also there is intense rain over south China and Southeast Asia.

SPCZ=South Pacific Convergence zone.
SPCZ is expected to remain draped from Coral Sea across northern Vanuatu to the
Tuvalu/Tokelau area, then to Northern Cooks/Marquesas. There is also likely to
be a developing trough near the end of the week over the Tahiti area.

STR= Sub-tropical Ridge
STR is weak and well to the north.
The HIGH that is north east of NZ of Monday is expected to travel east along
30S. There may be a small squash zone of enhanced Se winds on its northern side
near 18 to 19S between Palmerston Island and Tonga from Tues to Thursday UTC.
The next HIGH to exit Australia may be at 45S late this week, travelling east
across southern and central NZ this weekend. It may indeed have a squash zone
on its northern side, over or near northern NZ.

Voyage Outlooks:
Tahiti to the west
Looks OK for departure to the west between now and Tuesday local, albeit with
light winds for starters. After that a developing trough is expected to bring
some squalls and increase the SE winds to over 20 knots.. May have to wait until
20 July for next window of appropriate weather.
Since the SPCZ is expected to remain north of 15S, it appears that a voyage to
the west should travel along the drier and more settled latitudes near 17S.
Weather may not remain settled all the way from Tahiti to Tonga, as a trough is
expected to affect the Tongan area from 10 to 12 July local.

Between NZ and the tropics
MAYBE NOT this week (again), may as well stay put (again). A fast boat can
possibly depart from Opua on Monday (after a passing low) but is likely to
encounter strong + winds from a front on Thursday.
A LOW is crossing northern NZ on Thursday and Friday and is expected to linger
to north of NZ until next week. The northerly winds ahead of this low are
expected by Wednesday. So it's another stay put week.

Between Australia and New Caledonia/Fiji
OK to depart from Coffs/Brisbane area on Monday (local), but otherwise stay put
for a trough is expected there on Tuesday deepening into a LOW off Sydney
rapidly on Tuesday night. Stay put Tuesday to Thursday local then it may be OK
to go.
See my yotpak at for terms used.
See my website for information on tailor-made voyage forecasts-
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