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

25 January 2014

BOBGRAM issued 26 Jan 2014

WEATHERGRAM
YOTREPS
Issued 26 January 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.

Just a quick edition this week-we are busy celebrating my mums 90th!

SOI 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.

SOI has bounced back up in the past few weeks. Its 30-day running mean was
plus 0.81 on 25 Jan.

TROPICAL TOPICS
There is a tropical depression forming in the Coral Sea by Monday and this
is likely to develop into a Tropical cyclone by Wednesday and may then head
for the Queensland coast (GFS), or maybe for the New Caledonia/Tasman Sea
area by the end of the week (ECMWF)

By mid-week there is also a good chance of a tropical depression developing
over the Fiji area and then moving SE to the east of NZ.

WEATHER ZONES
South Pacific Convergence Zone SPCZ
This is very active in the Coral Sea at present and expected to get very
active over Fiji by mid-week. It is active between Samoa and French
Polynesia early in the week, but this branch is expected to ease during the
week.

Sub-tropical Ridge STR
The HIGH in the Tasman Sea is expected to stay there all week and then
weaken and maybe poke the tongue of a ridge onto the South Island on weekend
of Sat 1/2 Feb.

New Zealand area
Troughy, yet again, but not as much as last week. . An active front is
crossing the North Island tonight followed by a strong southerly flow on
Monday. For the remainder of the weak NZ is expected to have a SE flow
between a HIGH in the Tasman and a trough that is expected to stay between
Fiji and the dateline.

See my yotpak at boatbooks.co.nz/weather.html for terms used.
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe.
Weathergram text only (and translator) is at weathergram.blogspot.co.nz

Website is at metbob.com - To unsubscribe send an email to bob@metbob.com
saying unsubscribe.
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19 January 2014

BOBGRAM issued 19 Jan

WEATHERGRAM
YOTREPS
Issued 19 January 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.

SOI 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.
SOI has bounced back up in the past few weeks. Its 30-day running mean was
plus 0.64 on 19 Jan.

Weather Pattern for the past month.
The pressure anomaly map for the past month reveals that NZ has been troughy
and most of Australia has had higher than normal air pressures.

TROPICAL TOPICS
Tropical cyclone JUNE lost energy when it encountered the tall mountain
ranges of New Caledonia and is now moving over cooler seas and slowly
winding down, and will likely be just a Low by Monday (can be called Ex TC
JUNE). It still has plenty of wind and rain near its centre and is expected
to cross North Island on Monday (= Monday night/Tuesday local time).

WEATHER ZONES
South Pacific Convergence Zone SPCZ
TC JUNE was the product of a burst of convective activity over the Coral Sea
early last week.

The SPCZ is now an extension of and connected to the monsoonal heat trough
over Australia. This is expected to shift north across Australia this week,
relieving the heat over Victoria and New South Wales. When this zone gets
far enough north this may help trigger the formation of a tropical low over
northern Australia by the weekend.
There is a large Low over Western Australia for much of the week, and this
is expected to drift north as well.

Sub-tropical Ridge STR
The STR is in its typical summer position across the Southern Bight and the
Tasman Sea, and along 30 to 40S well east of NZ, but remains weak around NZ.

The HIGH which is expected to bud off Tasmanian on Wednesday should cross
central NZ on Friday/ Saturday 24/25 Jan, followed by a trough heralded by a
strong NW flow on Sunday.

Tasman Sea /New Zealand
Troughy. The remains of TC JUNE are expected on Monday (night local time to
Tuesday).
If it arrived a few days later then it could have coincided with the arrival
of a low with cold air fresh from the southern ocean ---and the combination
may have been a monster. As it is, that low fresh from the southern ocean is
expected to sideswipe southern NZ on local Wednesday night/Thursday, and by
then Ex-JUNE is likely to be near 50S.

See my yotpak at boatbooks.co.nz/weather.html for terms used.

Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe. Weathergram text only (and translator) is at
weathergram.blogspot.co.nz

Website is at metbob.com - To unsubscribe send an email to bob@metbob.com
saying unsubscribe. Feedback to bob@metbob.com

15 January 2014

BOBGRAM issued 12 Jan 2014

WEATHERGRAM
YOTREPS
Issued 12 January 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.

SOI 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.
SOI has dropped recently and is now slowly rising. Its 30-day running mean was plus 0.16
on 12 Jan.

TROPICAL TOPICS-
Tropical cyclone IAN brought damaging wind and waves to islands in the Ha'apai Group of
Tonga last night and is now being captured by a mid-latitude trough and shunted to the
southeast. It is expected to wind down as it encounters cooler seas.

There is also a Cyclone in the Indian Ocean called COLIN. It is travelling SW and expected
to re-curve to the SE near 25S.

WEATHER ZONES
South Pacific Convergence Zone SPCZ
TC IAN was the product of a burst of convective activity that came from the Solomons.
Another burst of activity can be seen currently over northern Australia forming the
Intertropical convergence zone there. This burst is expected to travel south onto
Australia from Wednesday-forming a tropical Low over NW Australia. The burst should also
spread into the Coral Sea and activate the SPCZ there- A tropical low is expected to form
in the Coral Sea by Friday 17 January and is likely to move towards NZ North Island next
week. Watch out for this low.

Sub-tropical Ridge STR
The STR is in its typical summer position across the Southern Bight and the Tasman Sea.
The High that is currently in the Tasman Sea is expected to stay put until Friday and then
weaken as it crosses the northern North Island on Sat 18 Jan.

Tasman Sea /New Zealand
Troughy. One trough is moving across the North Island on Monday and another on
Thursday/Friday, both followed by SW winds - not very summery this week.

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

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