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

13 August 2017

Bob Blog 13 Aug 2017

WEATHERGRAM
YOTREPS
Compiled Sun 13 Aug 2017

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.

TROPICS
At present tropical cyclone JOVA is travelling ESE (a strange direction) off the west Mexican coast and a tropical depression is expected to take a clockwise path around the Atlantic Ocean.
Meanwhile TC BANYAN is in the Northwest Pacific and is expected to go north and then northeast - its remains may reach Alaska, perhaps.
We can see these tracks at ruc.noaa.gov/tracks/

Last week's rain map, compared with the week before, shows continuing high rainfall around the NW Pacific, and the equatorial Indian Ocean, and the equatorial Atlantic Ocean. It has been very wet around Bangladesh, and there is a build-up of activity along the South Pacific Convergence zone.

Rain for the past week is from trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
The SPCZ is expected to shrink and shift to the north this week. The build-up of shower activity that occurred last week is expected to be gathered by a tropical trough and conducted south-southeastwards across Tonga /Niue area on Wednesday 16 Aug UTC.

Subtropical ridge (STR)
High to northeast of NZ is expected to travel east along 30 to 35s this week and build to a peak of over 1035 on Thursday 17 Aug UTC. This is expected to produce a squash zone of enhanced trade winds on the north side of this High on 17 to 19 Aug UTC-this should mainly affect French Polynesia.
New High is expected to move off eastern Australia into North Tasman Sea on Monday, and to travel along 20 to 30S past northern NZ on wed/thu UTC. This high is taking the typical path of a winter anticyclone.


Between Australia /NZ and the tropics:
Light winds in the subtropics between 20 and 30s with the incoming high.
South of 30s the pattern is a typical winter of disturbed westerlies, made stronger and squally by a deep Southern Ocean low travelling east along 45 to 55S, 960hpa, in Aussie Bight by Tuesday and south of the Taman Sea by Friday. SW swells up to 5+ metres with a period over 10 seconds in Tasman sea by this weekend.

French Polynesia to the west:
The trough that is expected to travel south-southeast over the Tonga/Niue area on Wed 16 Aug is likely to dominate the landscape this week for any vessels hoping to travel westwards towards Tonga.
It is likely to be an active trough because it is taking away (southwards) the build-up of extra energy from the SPCZ. Also, as this extra warmth comes south it is likely to encounter the colder denser airmass which crossed North Island tonight showing itself as an upper trough with lots of thunder and lightning.
I'll assume that it may be better to wait for this trough to make its way south-southeast, and so delay that trip toward Tonga until later this week or early next week.
The trough should bring a brief period of strong NE winds to Niue on Wednesday morning local or Rarotonga around Friday morning local.
If you would like more detail for your voyage, then check metbob.com to see what I offer.
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See my website http://www.metbob.com for more information
Feedback to bob@metbob.com or txt 6427 7762212
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.
To unsubscribe send a reply email saying LEAVE.
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06 August 2017

Bob Blog 6 Aug 2017

WEATHERGRAM
YOTREPS
Compiled Sun 6 Aug 2017

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.

TROPICS
NORU is still going and is expected to visit Japan this week, and NALGAR is over the open ocean further east. There are two tropical depressions on the Atlantic Ocean that may develop further during the coming week. We can see these at ruc.noaa.gov/tracks/

Last week's rain map, compared with the week before, shows continuing high rainfall around Japan, the equatorial Indian Ocean, and possibly the equatorial Atlantic ocean, and decreasing amounts elsewhere.

Rain for the past fortnight from trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
The SPCZ starts this week draped from Solomon Islands to Tuvalu and Tokelau Islands to Northern Cooks. An MJO event is moving into the western Pacific this week and that should help activate the SPCZ.
A convergence zone /trough is expected to travel east across the Society Islands on local Monday. Better to stay put for that and depart local Tuesday.
Next trough from the west is expected to reach New Caledonia on local Wednesday and Tonga area on local Friday, it's a minor trough but worthy of consideration.

Subtropical ridge (STR)
High east of NZ is expected to travel east along 30s until Thursday and then weaken as a High from further south builds around 160W.
New High is expected to move off eastern Australia into North Tasman Sea on Thursday, and travel along 28S past norther NZ by Saturday 12 Aug.

Between Australia /NZ and the tropics:
Low is expected to travel east along 40S from Monday to Wednesday across Southern Tasman sea. Moving southeast across central NZ on Thursday.

French Polynesia to the west:
A trough/convergence zone that is expected to be crossing the Society Islands on local Monday UTC. Wait until TUESDAY and its should be ok to go west from Society islands.
The SPCZ is expected to be mainly confined to the Solomon Islands to Tokelau Islands area, but may extend to Suwarrow by end of the week.

If you would like more detail for your voyage, then check metbob.com to see what I offer.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
See my website http://www.metbob.com for more information
Feedback to bob@metbob.com or txt 6427 7762212
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.
To unsubscribe send a reply email saying LEAVE.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

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