Bob Blog 28 Feb

Bob McDavitt’s ideas for sailing around the South

Disclaimer: Weather is a mix of pattern and chaos;
these ideas are from the patterned world.

Compiled Sunday 28 Feb

Satellite view of recent rain

The Tropical rain Measuring Mission provided us with
recent rain measurements via satellite that could be viewed on Goggle earth via
kml until the mission was decommissioned in 2018.

It has been replaced by the GPM or Global
precipitation Mission and data from this satellite, sadly not available as a kml
file, can be gleaned from, with a
choice of 7day, 24 hour or 30 minute timesteps.


Sadly, there is no latitude/longitude grid.

This data is also available from the nasa viewer
website at, in the Layer picker click “+Add
layers” (bottom left) and search for “GPM” or “IMERG” then select Rain rate
(Ascending) and Rain rate (Descending), then close the selection windows to view
the data.


Sadly no coastal boundaries or lat/long grid.

The Tropics

The latest cyclone activity report is at and Tropical Cyclone Potential is from


TC MARIAN is moving southwest across the South Indian

A strong monsoonal trough lies across the South
Pacific with several small lows brining squally showers but these have a low
likelihood of growing further. There is a Tropical Depression 99P in the Coral
Sea that has a high potential of this system becoming a Tropical cyclone by


Weather Zones Mid-week GFS model showing isobars,
winds, waves(magenta), Rain (Blue), STR (Subtropical Ridge), and SPCZ (South
Pacific Convergence Zone).


Predict wind CAPE mid-week gives two possibilities
for SPCZ.


SPCZ=South Pacific Convergence zone.

SPCZ is stretching southeast from Solomons to Tonga.
 TC is expected in the Coral Sea.

A passing trough extends to southeast of French
Polynesia and this may form a low near the Austral Group by local Thursday that
should travel off to the South.

The rain accumulation map is starting to show a line
of showers at 5S to south of the Galapagos.  This is the start of an annual system
that is sort-of-a-mirror-image of the ITCZ, due to the noon day being directly
overhead 5 degrees South latitude from around 5 to 10 March.




Accumulation next five days from

Subtropical ridge (STR)

HIGH 1022 east of South Island is expected to travel
east along 47S and build to over 1030 near 140West.

Next HIGH is expected to travel east across Tasmania
on Saturday 6 March and then travel northeast across the Tasman Sea and onto
North Island early next week.


NZ/Tasman troughs

Low 1005 in Tasman Sea is expected to travel off to
the south. Another Low is expected to form east of Tasmania on Monday and deepen
to below 984 as it passes by Campbell island on Wednesday with a few days of
strong westerly flow over NZ, turning SW on Thursday and Friday.

Start of America’s Cup in Auckland has been delayed
by a COVID lockdown.


Panama to Galapagos/Marquesas

Good northerly winds in Panama this week, but these
may become light and variable by mid-March. Wind flow over Galapagos is expected
to turn to be from the south from mid-arch. Current is expected to peel off to
the north of Galapagos, so way to go to Marquesas this week is via 3N 92W.


If you would like more detail for your voyage, then
check to see what I offer.

Or Facebook at /

Weathergram with graphics is at
(subscribe/unsubscribe at bottom).

Weathergram archive (with translator) is at

Contact is or txt 6427 7762212