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

27 January 2013

BOBGRAM issued 27 Jan 2013

WEATHERGRAM
YOTREPS
Issued 27 Jan 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) was hugging the plus 0.5 value in Sep Oct Nov, during December it dived to almost minus 1, but in January it has relaxed and is, on the 27th, near zero.

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 this 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 monsoonal trough over central Australia continues to have little cloud and rain—this is why much of the Australian continent is being baked in the sun. Queensland managed to briefly brew tropical cyclone OSWALD. Its remains are still bringing wind and rain. It's remains should move off to the south by Wednesday.

The main convection of the ITCZ is over Indonesia – north of its normal position at this time of the year - over the Timor sea and northern Australia. It extends into a South Pacific Convergence Zone SPCZ between 5 and 10S from Papua New Guinea to Northern Cooks. This convergence zone spirals into TC GARRY which is over Southern Cooks. This is expected to wander off to the SE, but another tropical depression is likely to quickly replace it in the zone between Samoa and Southern Cooks later this week.

We are now entering the business period of the Tropical Cyclone season and another Tropical depression may form out of the convection cloud that is sitting near 20S to South of Fiji. This is expected to be a slow-moving system

TASMAN SEA/NZ TROUGHS
Large High is blocked just east of NZ .. it exit route to the east is cut off by remains of TC GARRY until Wed 30 Jan. This High should then move off by Sat 2 Feb and allow a new Low to develop in the Tasman Sea on Thursday 31 /Fri 1Feb and move across South Island on Sun 3 Feb followed by another High.

These HIGHS are expected to maintain strong easterly winds and moderate to heavy easterly swells over northern NZ for the next week of two. These may be OK for Auckland Anniversary Regatta on Mon 28 Jan, but not OK for going fishing off northern NZ this week.
However, the blocked HIGH does allow summer sailing around central NZ until Wed 30 Jan.
Enjoy.
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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

20 January 2013

BOBGRAM issued 20 Jan 2013

WEATHERGRAM
YOTREPS
Issued 20 Jan 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) was hugging the plus 0.5 value in Sep Oct Nov, during December it dived to almost minus 1, but in January it has relaxes and is, on the 20th, near plus 0.2.

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 this changes the earthly wind zones and has an impact on the latitude zones of weather.
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 monsoonal trough over central Australia continues to have little cloud and rain—this is why the Australian continent is acting something like a hot plate left out in the sun and having a continuing heat wave. A few thunderstorms, but their lightning is triggering bush fires. Meanwhile the clouds have been lingering over Indonesia, creating floods. Not normal.
Some cloud and rain is settling over Northern Aussie this week.

The South Pacific Convergence Zone SPCZ currently extends along 10S from Tokelau to Tuvalu and south across the Cook Islands. There is a tropical depression between Rotuma and Futuna … hard to say what its future may be at this stage.

MADDEN JULIAN OSCILLATION
Madden and Julian were meteorologists who in 1971 published their discovery of a process by which energy for promoting convection and tropical cyclone formation travels from the Indian Ocean to the Pacific Ocean. This is now called the MJO (Madden Julian Oscillation), AND one of these is likely to arrive in the Coral sea this week, making the next few weeks likely to be 'the business end' of this tropical cyclone season. Computers are expected tropical cyclones to occur in NW Australia, the Gulf of Carpentaria, the Coral Sea and/or over Samoa heading for the Cooks.

At present there is not much happening- except for that TD between Rotuma and Futuna. Basically this is NOT a week to go to sea in the South Pacific, but details are still unsure.

TASMAN SEA/NZ TROUGHS
Large High is crossing central NZ from Mon/Tue 21 to 22 Jan. A weak replacement trough is likely over the South Island on Wed 23 Jan and North Island during the local morning of Thu 24 Jan.
Another High in the Sub Tropical Ridge is expected to move across NZ on Thu /Fri 24/25 Jan and linger to east of NZ until the start of next week.
So, it's a week of summer sailing over NZ.
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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

13 January 2013

BOBGRAM issued 13 Jan 2012

WEATHERGRAM
YOTREPS
Issued 13 Jan 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) was hugging the plus 0.5 value in Sep Oct Nov, and during the last few weeks it dived to almost minus 1, but as at 13 Jan has relaxed again to near zero.

The Ocean: Sea surface temperatures across the equatorial Pacific act as a thermostat for the planetary weather engine. When they are warmer than normal ( El Nino) we get more evaporation and clouds in that region and this augments the earthly wind zones and has an impact on the latitude zones of weather.

Well, in the past month the SST in this target zone has mostly been slightly below normal, and the oceanic pattern is neither El Nino, nor La Nina; it remains neutral.

The latest SST anomaly data also shows there is a much warmer than around the seas neighbouring NW Australia. This is the source area for TC NARELLE which is side-swiping west Australia this week.

WEATHER ZONES
The monsoonal trough is sitting over central Australia as is normal for this time of year, but its clouds and rain are late—may arrive later this month—and so Australian continent has become something like a hot plate, heating up in the sun. This explains its continuing heat wave.

The latest pressure and rain map for the region shows this, along with path so far of TC NARELLE and some likely future paths of that system. It also shows the STR Sub tropical ridge from Aussie bight to north of NZ, and the SPCZ South Pacific convergence zone, which is now covering a wide latitude band.

The tropical Low near Tonga is expected to deepen over next few days over NIUE and SOUTHERN COOKS and then go off to the south. BRACE FOR IT.

TASMAN SEA/NZ TROUGHS
The incoming jetstreams has been crossing the mid Tasman Sea. This has been controlling the fronts crossing NZ--- they have been very active over the South Island, but weakening over the North Island.

Surface Low that is now in the mid Tasman is expected to deepen as it crosses central NZ on Tuesday and Wednesday. Avoid any sailing these days. This should be followed by another summer High for another summer weekend.
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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

06 January 2013

BOBGRAM issued 6 Jan 2013

WEATHERGRAM

YOTREPS

Issued 6 Jan 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: Things are changing. The Southern Oscillation Index or SOI (30 day running mean) was hugging the plus 0.5 value in Sep Oct Nov, but during the last few weeks has dived to almost minus 1. An interesting swing towards an El Nino.

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During the past week FREDA faded away over New Caledonia, and has turned into a mid-latitude low that has deepened a little just east of NZ during today and should weaken again as it moves off to the SE on Monday.

Australia is having a heat wave. The Monsoonal trough is expected to form a tropical cyclone over the sea west of Darwin on Monday and this system is likely to spend the remainder of the week travelling counter clockwise along Australia's west coast. A heat low may form somewhere over the interior and the pressure difference between the lows and the High over the Aussie Bight are likely to make for some strong hot winds reaching their pick over South Australia/Victoria from Mon 14 to Wed 16 Jan.

The South Pacific Convergence Zone SPCZ is now reforming in its normal summer position from Solomons to Fiji /Tonga with another convergence zone over French Polynesia. The next tropical LOW that is expected to form on the SPCZ is likely to do so near Minerva to South of Tonga around Sat/Sun 12/13 Jan.

STR Subtropical ridge

There is a STR high at 40S in the Aussie Bight. This is expected to move NE across the Tasman Sea on Monday/Tuesday 7/8 Jan and then weaken into a tongue-shaped ridge as it travels eastwards to north of NZ on Wed 9 Jan and then go SE and expand into a High again near 40S 160W by Thursday 10 Jan. Another High is expected to reach Aussie Bight from Tue 8 Jan and fade over Bass Strait on Thursday 10 Jan. Another high is expected to form near 45S in Aussie Bight on Sat 12 Jan and travel east to South Island on Tue/wed 15/16 Jan. All these highs have strong winds on their northern side.

TASMAN SEA/NZ TROUGHS

Trough moves off to east of NZ on Monday.

Front is expected to move onto South Island on Wed 9 Jan preceded by strong NW winds, hot in the east and wet in the west. This should be followed by strong westerly flow over much of NZ on Thu 10 Jan. Another front is expected over South Island on Sat12 Jan preceded by strong NW flow. This front is likely to be cross NZ on Sat/Sun followed by a southerly flow by Monday 14.

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NEWS: Jeanne Socrates in NEREIDA (Neptune's daughter) is about to round Cape Horn. She is doing a solo-non-stop unassisted circumnavigation, and I am helping (on the side) by watching the weather with her. There are lows ahead of and behind her so check out and see how things turn out.

To learn more about her story visit http://www.svnereida.com/ and if you are impressed then please click on the link to Marie Curie Cancer care and leave a donation at http://www.justgiving.com/jeannesocrates.

More News: I have been awarded in the New Year's Honour List-as a member of NZ order of merit for services to meteorology and yachting.
http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10856717

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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

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