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

22 February 2015

BobBlog

WEATHERGRAM
YOTREPS
Issued 22 February 2015
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 TROPICAL TOPICS Cyclone MARCIA did a surprise increase to
Category 5 on Friday and the had gusts over 200kph upon landfall see my
blog at http://metbob.wordpress.com/2015/02/20/tc-marcia-observations/
At present the remains on MARCIA are fading in the Tasman Sea and the
remains of LAM are over Western Australia:

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ is expected to develop over Coral Sea to Fiji and is worth watching
over the next week, its activity may turn into a tropical depression or
stronger at any time.
STR/NZWEATHER = Sub-tropical Ridge
The STR is expected to stay over northern NZ, so that sailing around NZ is
likely to be light variable winds until later this week when increasing NE
winds are expected ahead of a trough from the north getting strong around
Cape Regina by around Sunday 1 MARCH See my yotpak at
boatbooks.co.nz/weather.html for terms used.
Weathergram text only (and translator) is at weathergram.blogspot.co.nz
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe.
My website is at metbob.com Feedback to bob@metbob.com To unsubscribe send
a reply email saying LEAVE.
Bob McDavitt

15 February 2015

Bob Blog

WEATHERGRAM
YOTREPS
Issued 15 February 2015
Bob McDavitt's ideas for sailing around the South Pacific.

The Ocean: extra heat has been stored in the Pacific Ocean for a while now,
and Oceanic indices are still in El Nino territory but relaxing. In fact Sea
surface temperatures in the eastern Pacific Ocean are now less than normal.
But they remain above normal in the western and central Pacific.

The Atmosphere: The Southern Oscillation Index SOI (30 day running mean)
sums up the weather pattern over the South Pacific as one number. It is
based on the standardized difference in the barometer readings between
Tahiti and Darwin. It has been negative since July and dived below -10
(Australian units) for much of September, and again for a week in November,
then relaxed in early December and during January, and is now diving
negative.

TROPICAL TOPICS
The tropic are going through a quiet time at present There are some tropical
lows around NE of Australia and maybe in Gulf of Carpentaria moving south,
and one over Vanuatu and another to NW of Australia both of these are
travelling southeastwards and not expected to develop.

The weekly rain maps over the past fortnight show a shift in the most
intense rain southwards across the equator and towards NE Australia. This is
the zone with the warmest sea surface temperatures in the planet at present
and it has stored plenty of heat in the last month to feed several top
category cyclones. What has been missing over recent weeks is the
opportunity. Late this month we expect another MJO cycle of enhanced
convection to travel east across northern Australia and into the Coral Sea
so although the risk of a cyclone may be low this week, it is expected to
rise rapidly towards the end of February.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ should slowly intensify this week in the Coral Sea The tropical low
near Vanuatu today is expected to travel SE to south of Fiji and be ripped
apart by the strong SE winds at the surface and strong NW winds aloft. There
is a jet stream between NZ and Fiji at present and this can help rip things
apart (it can also help develop things if they are in the right place but
more about that at another time).

STR (Sub-tropical Ridge) and over NZ
A large HIGH is travelling slowly across NZ next few days. Its eastern flank
is expected to weaken away from Tuesday to Wednesday allowing a trough and
southerly change to affect the east coast on Thursday and Friday, and then
the western flank of the HIGH is expected to travel across southern NZ on
Sat 21 and then off to the east leaving a NE flow over NZ.

See my yotpak at boatbooks.co.nz/weather.html for terms used.
Weathergram text only (and translator) is at weathergram.blogspot.co.nz
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe.
My website is at metbob.com Feedback to bob@metbob.com To unsubscribe,
send a reply email saying LEAVE.

08 February 2015

Bob Blog

WEATHERGRAM
YOTREPS
Issued 8 February 2015
Bob McDavitts ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world

A quick and short blog this evening as I was driving from Wellington to
Auckland today and had to fix a puncture along the way, replacement tyre was
a space-saver and they upset the wheel balance and reduce a cars maximum
controllable speed (on good roads) to 80kph  an interesting speed for me to
attempt on the Auckland motorways).

TROPICAL TOPICS
Cyclone OLA faded in the north Tasman last week but its clouds brought some
much needed rain to northern NZ on Wednesday 4 Feb.
At present there is a named cyclone in the NW Pacific called HIGOS heading
for the area north of Guam and weakening.
And TC FUNDI in the Indian Ocean which may bring gales to an area south of
Madagascar on Monday (local).
The weekly rain maps over the past week show the track of OLAs rain onto
northern NZ and the recent downpours in Madagascar.
Comparing this with the previous weeks map shows a DROP in the top
intensity of tropical rainfall, but a greater spread in area.
Weekly rain signatures are seen at
http://trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ is expected to weaken further and split into a northern and a southern
zone. Spreading the convergence like this only weakens its ability to gang
together the thunderstorms into cyclones, and so we should have a cyclone
free weekunusual at this time of the year.

STR= Sub-tropical Ridge
The blocking of January has been replaced by mobile and strong Highs in
February  with increasingly noticeable troughs in-between.
The HIGH that is crossing Tasmania on Monday should travel east onto
southern NZ on local Tues/Wed and then east along 45S.
Next HIGH is expected to travel SE from the Aussie Bight on Thu 12 Feb and
skirt around the south of NZ, at 47 to 50S on Fri/Sat 13/14 Feb and then
travel east along 45S.
With the STR so far south, there are likely to be strong SE winds likely
this week between 25 and 35S building easterly swells to over 3 metres
especially in the zone north of the migratory Highs.

Over NZ/Tasman
Between the migratory Highs there are cold fronts/troughs with brief SW
changes - one on Monday(local) and one on Thursday/Friday (local); these
travel NE but are expected to fade over southern North Island (as they move
away from their upper support).

See my yotpak at boatbooks.co.nz/weather.html for terms used.
Weathergram text only (and translator) is at weathergram.blogspot.co.nz
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe.
My website is at metbob.com
Feedback to bob@metbob.com
To unsubscribe, send a reply email saying LEAVE.

01 February 2015

Bob Blog

WEATHERGRAM
YOTREPS
Issued 1 February 2015
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 Ocean: The extra heat that has been stored in the eastern equatorial
Pacific Ocean is now decreasing and no longer pointing to an El Nino
episode.

The Atmosphere: The Southern Oscillation Index SOI (30 day running mean)
sums up the weather pattern over the South Pacific as one number. It is
based on the standardized difference in the barometer readings between
Tahiti and Darwin. It has been negative since July and dived below -10
(Australian units) for much of September, and again for a week in November,
then relaxed in early December, and has been up and down over past few
weeks.

TROPICAL TOPICS
Cyclone OLA has appeared in the area west of New Caledonia on Saturday and
is expected to go south then southwest and weaken and then be erratic.

In the Indian ocean, to south of Diego Garcia, TC EUNICE is travelling ESE
and soon expected to curve to the SE and fade.

The weekly rain maps over the past fortnight show heavy rain associated with
tropical depressions and TC EUNICE in the Indian Ocean, and also TC OLA.
There has also been heavy rain in past week from Samoa to Niue.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ is expected to weaken and retreat to the north and west this week to an
area between Vanuatu and Tuvalu. It should shed the clouds associated with
TC OLA into the Tasman sea.
A Low is shown in some model weather maps over Fiji by Wednesday. This has
less than a 50% chance of forming (other models do not have it forming)
anyone in the area should remain vigilant and get updates.

STR= Sub-tropical Ridge
The STR spent January over the NZ area thanks to a series of blocking HIGHS
near 180.
The Blocking index time-longitude graph shows this strong blocking near
180 has now faded, and now indicates that it is shifting more towards
160E/Australian Bight. This suggests we can expect more Highs over SE
Australia during February and fewer building over NZ in other words a swing
to a more SW wind flow over the South Island.

Over NZ/Tasman
By mid-week a deep low is shown on the forecast weather map in the south
Tasman Sea, and this shows how this change of weather pattern may work:
with a low expected to deepen rapidly as it crosses the south Tasman Sea
so that it delivers strong SW winds to most of NZ on Wednesday. This new
regime will be wetter and winder for southern and western NZ than the
January blocking regime, but might only bring occasional showers to Nelson
and Canterbury-Hawkes Bay.

See my yotpak at boatbooks.co.nz/weather.html for terms used.
Weathergram text only (and translator) is at weathergram.blogspot.co.nz
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe.
My website is at metbob.com Feedback to bob@metbob.com To unsubscribe send
a reply email saying LEAVE.

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