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

08 June 2014

BobBlog issued 8 June 2014

Issued 8 June 2014
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.

D-day was 70 years ago this week, a good report of the weather forecasting
crucial to this turning point of WWII is at http://uk.

It was a year ago this week that we got the final test message from SV NINA
in the mid Tasman Sea and since then nothing has been seen of the vessel and
its occupants.
Herald reporter Annan Leask has marked this occasion with this report
The Nina Mystery is now one year old, and the MH370 mystery is nearly 3
months old. We live in interesting times. Our hearts go out to the lost and
to their families, and we hope that some lessons are learnt from these
events. Pray, one minutes silence please.
The Ocean:
The warmer the sea the quicker it evaporates, tossing water vapour into the
air, where is rises and cools into cloud. The equatorial Pacific region
hosts the warmest sea on the planet. Thus its sea surface temperatures SST
is a factor in the running of planetary weather engine.
An index for this is NINO3.4 and its abnormalities tend to influence changes
in clouds along the equator and thus tweak the latitude zones of weather
around the planet. Recently a lot of extra heat has been stored in the upper
depths of the equatorial Pacific Ocean and some of this is now reaching the
surface near the Galapagos.

Over the last few weeks we have had little if any in the way of
cyclones/hurricanes/typhoons around the planet.
The Indian Monsoon is starting to arrive over southern India, about a week
behind normal, leading to some very dry anomalies.

Tropical rain maps over the past two weeks shoe that the convergence zones
are starting to get closer than normal to the equatorand this is producing
a warm zone along 20S, including over Brazil where the Football World cup
starts on Thursday. This is typical El Nino.


SPCZ= South Pacific Convergence Zone
This has weakened and travelled north in the past week, and is hard to find
in the weather prog maps for the coming week. There is likely to be a
convergence zone for a few days associated with and on the south side of a
low in the Coral Sea, but this is expected to fade away by Thursday.

STR= Sub-tropical Ridge
The STR has in the last week deviated to well south of its normal position,
with the HIGH that is currently moving across Tasmania expected to travel SE
across south Tasman Sea to SE of NZ by Tuesday and then east
along 50S, with central pressure well over 1030. There are enhanced
easterly winds on the north side of this High, and they are expected to help
spin up several LOWS in the 30 to 40S latitudes in the South Pacific this
week, including two over the NZ area. Lots to avoid, and rather an
abnormal situation. It is what old-style meteorologists would call low

Departing from NZ to the tropics
Very wet front travelling south across the North Island on Monday is likely
to stall over central NZ on Tuesday to Thursday. Winds over Northland
should ease by Wednesday and then be in an OK direction for departure, but
better check this forecast again on Monday the Low that is currently
stationed west of Taranaki is expected to go west and then fade, and this
may allow an secondary to form on the front and do a clockwise loop over or
just west of the North Island, getting deeper than the first low and causes
all sorts of local wind/rain complications. This secondary should clear off
on Friday 13th

See my yotpak at for terms used.
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