Translator

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

24 February 2013

BOBGRAM issued 24 Feb 2013

WEATHERGRAM
YOTREPS
Issued 24 Feb 2013
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.
The Atmosphere: The Southern Oscillation Index or SOI (30 day running mean) is based on the barometer readings from Tahiti and Darwin and sums up the weather pattern over the South Pacific in one number. It was almost minus 1 during December, relaxed to near zero during January, fell to minus 0.9 during mid-February and has recovered to minus 0.65 on 23 February. So it is unsteady with a negative tilt.

The Ocean: Sea surface temperatures across the equatorial Pacific act as a thermostat for the planetary weather engine. When they are different from normal we get a change in clouds around the equator and in the latitude zones of weather across the whole Pacific.
Well, in the past month the SST in this target zone has been slightly below normal, but relaxing toward normal, indicating a tendency towards neutrality. This shows up clearly in the monthly change of SST anomalies as seen at the Climate prediction centre at www.cpc.ncep.noaa.gov


WEATHER ZONES
The weather is getting busy in the South Pacific over the next few weeks.
A Madden Julian Oscillation of enhanced convection is moving from the Indian Ocean onto northern Australia and towards the Coral Sea, and this is likely to increase the risk of tropical cyclone formation during the next few weeks.
At present TC HARUNA is moving away from Madagascar, there is a tropical storm over NW Australia heading for Port Hedland (landfall expected by 27 0600UTC (Wednesday), and a tropical depression off to the west of NW Australia, heading for Cocos Islands area. A low of topical origin deepened off Queensland and made landfall over northern New South Wales.
In the coming week, there are early indications in the models of a tropical low forming in the Coral Sea and moving onto New Caledonia on Fri/Sat/Sun 1/2/3 March. Also a Low is expected to form south of Fiji on Mon/Teas and then maybe fade or move south off to the east of NZ on Wed/Thu/Fri.

The South Pacific Convergence Zone SPCZ has weakened during the last week and at present extends over north Vanuatu, Fiji and Tonga, with another branch active over French Polynesia. The cloud over Fiji is started to rotate and that is likely to produce a low between Fiji and NZ by Wed 27 Feb.

The Sub tropical ridge STR extends from Aussie Bight across the Tasman Sea and southern NZ and then eastwards along 45 to 40S. The centre over NZ is blocked by a low east of NZ and is expected to finally move off to the east on Wed and Thu 37/28 Feb. along about 35S. Between this High and the Low near Fiji there is a squash zone of enhanced SE winds around the north end of NZ.

Another High is expected to skirt around south of Tasmania on Sat 2 March and then progress NE across NZ next week.

There has been a series of blocking anticyclones over NZ during the past month, leaving the North Island HIGH and DRY.

TASMAN SEA/NZ TROUGHS
There is one front between those two highs. It is expected to move onto over the South Island on Fri/Sat 1/2 Feb and might affect the North Island on Sunday 3 Feb, but not much rain in it.

See my yotpak at http://www.boatbooks.co.nz/weather.html for terms used.
Weathergram with graphics is http://metbob.wordpress.com
Weathergram text only http://weathergram.blogspot.co.nz
Website http://www.metbob.com
Feedback to bob@metbob.com

17 February 2013

BOBGRAM issued 17 Feb 2012

WEATHERGRAM
YOTREPS
Issued 17 Feb 2013
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.
The Atmosphere: The Southern Oscillation Index or SOI (30 day running mean) is based on the barometer readings from Tahiti and Darwin and sums up the weather pattern over the South Pacific in one number. It dived to almost minus 1 during December, relaxed to near zero during January, and has dived to minus 0.9 so far during February. So things may now be tilting in the favour of weather systems that bring SW winds over the South Island (El Nino). But not this week---

To see the SOI for the past few months , updated weekly, view
http://weather.farmonline.com.au/climate/indicator_enso.jsp?c=soi&p=weekly

The Ocean: Sea surface temperatures across the equatorial Pacific act as a thermostat for the planetary weather engine. When they are different from normal we get a change in clouds around the equator and in the latitude zones of weather across the whole Pacific.
Well, in the past month the SST in this target zone has mostly slightly below normal, indicating a tendency towards La Nina in the Ocean. This dichotomy between atmosphere and ocean indicates that the tropics are having a mixed impact on our seasonal weather.

WEATHER ZONES
There is a Madden Julian Oscillation of enhanced convection moving from the Indian Ocean onto northern Australia this week. This can be seen at
http://cawcr.gov.au/staff/mwheeler/maproom/OLR_modes/h.6.MJO.S.html, where the blue zone (of less OLR) marks a strengthening of convection and an increased chance of tropical cyclone formation.
The latest EC model has a tropical cyclone forming off NW Australia this weekend and possibly making landfall around Mon 25 Feb.
Also all the computer models are showing a tropical depression forming off the Queensland Coast on Mon/Tue 18/19 Feb, then tracking offshore and following the coast southwards and deepening as far as 30S then weakening and making landfall over New South Wales around Friday. Avoid.

The South Pacific Convergence Zone SPCZ has strengthened and broadened a lot in the past week and is mainly draped between 10 and 25S, with clusters of convection over Fiji, from Samoa to Marquesas, and south of Southern Cooks. By the end of this week the SPCZ should be in much the same place and continuing strong, with the possibility of a low lingering south of southern Cooks.


The Sub tropical ridge STR extends from Aussie Bight across the Tasman Sea and NZ and then along about 35S. It is at its southern most position- consistent with the time of year.

The High crossing NZ on Monday is expected to move off to the east on Tuesday.
Another High is expected to cross South of Tasmania on Wednesday and then its eastern side is likely to fade south of NZ on Thursday. Its western side is expected to skirt the South Island SE coast on Friday and blossom east of or over the South Island during Sat/Sun 23/24 Feb.

There is one front between those two highs. It is expected to be over the South Island on Wed 20 Feb and should then peel off to the east, but may help a trough to form off NE of NZ on Thursday and Friday- and that may make for a SE flow for the TELECOM THREE KINGS race being held by Royal Akarana Yacht club.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
See my yotpak at http://www.boatbooks.co.nz/weather.html for terms used.
Weathergram with graphics is http://metbob.wordpress.com
Weathergram text only http://weathergram.blogspot.co.nz
Website http://www.metbob.com
Feedback to bob@metbob.com

10 February 2013

BOBGRAM issued 10 Feb 2013

WEATHERGRAM
YOTREPS
Issued 10 Feb 2013
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.
The Atmosphere: The Southern Oscillation Index or SOI (30 day running mean) dived to almost minus 1 during December, and relaxed to near zero during January. Around 3 Feb it was minus 0.4 and on 10 February it had dived to minus 0.9, so things are tilting in the favour of SW winds over the South Island now.

The Ocean: Sea surface temperatures across the equatorial Pacific act as a thermostat for the planetary weather engine. When they are different from normal we get a change in clouds around the equator and subsequent changes in the earthly wind zones has an impact on the latitude zones of weather across the whole Pacific.
Well, in the past month the SST in this target zone has mostly slightly below normal, indicating a tendency towards La Nina in the Ocean, and the ocean seems to be leading the atmosphere, perhaps.


WEATHER ZONES
There was a Madden Julian Oscillation of enhanced convection across the Pacific Ocean late January/early February and this has gone now… looking at the OLR measurements below it looks as though the next (and probably the last) chance for tropical cyclones this season is going to be with the next lot of below OLR (blue) shading in our region, during late February early March.


The South Pacific Convergence Zone SPCZ is mainly east of the 180 line, from Samoa to Tahiti and is expected to have a weak week ahead. Good for anyone wanting to do an island jump in the middle of the cyclone season.

The situation map shows a trough over Fiji on Sunday and cloud/rain in a low between Tonga and NZ. This Low is expected to weaken as it goes off to SE, from Wed 13 to Sat 16 February trade winds should then dominate the whole South Pacific north of the STR.

The Sub tropical ridge STR extends from Aussie Bight to north and then east of NZ with another branch along 30S from 160 to 120W.
The cell east of NZ is expected to be a slow-mover along 43 S expanding and travelling off to the east, leaving a lingering ridge over North Island until end of Monday.

A new High Cell is in the Aussie Bight and should squeeze around south end of Tasmania on Wed and Thu 13/14 Feb then travel NE across the Tasman Sea on Fri /Sat 15/16 and across NZ on Sun 17 Feb then off to the east.

TASMAN SEA/NZ TROUGHS
There is one front between those two highs. It is over Fiordland on Sunday night and should weaken as it travels east (NE across NZ) across South Island on Monday and off to the east of the North Island on Tuesday.
Acting as a herald for the new high, a southern ocean Low is expected to zip east on Wed/Thu 13/14 Feb, and on its northern end is cold front and southerly wind flick for eastern NZ. Heaps of swell around this low as well.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>><<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
See my yotpak at http://www.boatbooks.co.nz/weather.html for terms used.
Weathergram with graphics is http://metbob.wordpress.com
Weathergram text only http://weathergram.blogspot.co.nz
Website http://www.metbob.com
Feedback to bob@metbob.com

03 February 2013

BOBGRAM issued 3 Feb 2013

WEATHERGRAM
YOTREPS
Issued 3 Feb 2013

Ap0logises for any multiple resends--- problems with email server tonight.
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.
The Atmosphere: The Southern Oscillation Index or SOI (30 day running mean) dived to almost minus 1 during December, and relaxed to near zero during January. Around 3 Feb it was minus 0.4 .

The Ocean: Sea surface temperatures across the equatorial Pacific act as a thermostat for the planetary weather engine. When they are different from normal we get a change in clouds around the equator and thus changes the earthly wind zones and has an impact on the latitude zones of weather across the whole Pacific.
Well, in the past month the SST in this target zone has mostly been around normal, and so the oceanic pattern is neither El Nino, nor La Nina; it remains neutral.

WEATHER ZONES
The remains of OSWALD have moved off eastern Australia now and the flooding has gone. Interestingly, the clouds and rain over Indonesia have mostly gone too. Good riddance.
This coming week is usually the hottest week of the year in the mid-latitudes of the Southern hemisphere, and Australia is acting as a hot plate left out in the sun. There is NOT expected to be any relief from any monsoonal trough (except maybe over NW Australia)… just more mainly East to NE winds until at least mid-February.
.
The South Pacific Convergence Zone SPCZ is it its northern position from Solomons to French Polynesia , however there is also a more southern zone with a tropical depression near Fiji extending clouds onto Niue and Southern Cooks. The westerly winds on the northern side of this low are expected to increase, and the low may well turn into a TC. Anyway its future track is expected to go ENE across Tonga on Monday and then East and the SE across Southern Cooks on Wednesday 6 Feb. Avoid.

The Sub tropical ridge STR extends from Aussie Bight to north of NZ to east of NZ. During the coming week that high cell now in the Aussie Bight is expected to drift east and cro9ss central NZ on 6 to 8 February, just in time for picnic weather for WAITANGI DAY. "Positive Vibration" would have said/song Bob Marley (6 Feb= his birthday; ALSO still celebrated in NZ).
http://www.youtube.com/watch?v=ym4s9F4adDw – we can celebrate an end to blocking with a little music, yea.


TASMAN SEA/NZ TROUGHS
OK there are two troughs form NZ this week, after a record dry January is many parts of the country (http://www.niwa.co.nz/climate/summaries/monthly).

One trough is expected to cross on Mon/Tue but has to combat dry air and may not make much impact. The next trough is expected on Sun/Mon/Tue 10-12 Feb and should be able to bring more rain to our parched pastures.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>><<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
See my yotpak at http://www.boatbooks.co.nz/weather.html for terms used.
Weathergram with graphics is http://metbob.wordpress.com
Weathergram text only http://weathergram.blogspot.co.nz
Website http://www.metbob.com
Feedback to bob@metbob.com

Blog Archive