Bob’s Blog 14 Oct

WEATHERGRAM

YOTREPS

Compiled Sun 14 Oct 2018

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.

I’m back “on deck” in Auckland and available to help those voyaging the South Pacific

In early October the Australian and South Pacific Cyclone centres issue their preliminary outlooks for the coming season:

The Burau of Australia headline is: Lower number of cyclones likely for Australia

Then they posted this rather confusing graphic:

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See http://www.bom.gov.au/climate/cyclones/australia/

To understand how those numbers fit in with the headline, invert them.

SO for Australia as a whole the average is 11 cyclones and the probability of average or less is 63%.

NIWA say that multiple severe tropical cyclones are expected: and use the assumption that the ocean temperatures are leading into an El-Nino of the El Nino-Modoki (central Pacific based) flavour during the early part of the cyclone season.

See http://www.jamstec.go.jp/frcgc/research/d1/iod/enmodoki_home_s.html.en

This tugs the South Pacific Convergence zone eastwards, thus maybe reducing the cyclone risk around New Caledonia /Vanuatu, and increasing the risk for Samoa/Cook Islands/Austral Islands..

NIWA in New Zealand came up with following graphics:


See www.niwa.co.nz/climate/southwest-pacific-tropical-cyclone-outlook/southwest-pacific-tropical-cyclone-outlook-october-2018

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And this translates to the following Cyclone Outlook count:

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This seems easier to understand than the Australian outlook map.

The Pacific Islands Climate Outlook Forum was held over the last few days in Nadi Fiji to help prepare for the coming cyclone season and their outlook statement is imminent.

Next, a quick look at the current cyclone map:

image

After several very busy weeks, including MICHAEL over Florida in the past few days (with devastating storm surge at Mexico Beach) , tonight: all we have is LUBAN over Yemen and Strom(from the Tropics) LESLIE over Portugal (not shown on above map).

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Path of Hurricane MICHAEL

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Looking at the weekly rain maps, last week’s shows the path of MICHAEL and SERGIO around North America, a build-up of activity between India and Indonesia, an easing in activity around Micronesia, and much the same elsewhere.

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See: trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

WEATHER ZONES

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Weather Zones (see text) as expected Wednesday 00UTC showing isobars, winds, waves(magenta), STR, and SPCZ. Pink area = lightning likely (high CAPE)

BFH=Big fat High

SPCZ=South Pacific Convergence zone.

The SPCZ is sitting over northern Coral sea and northern parts of Vanuatu and on-and-off to north of Fiji. It is expected to drift south towards Fiji late this week. A tropical low may form on this zone early next week and then travel eastwards towards Samoa.but then fade again by md-next-week.

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Accumulated rainfall for next week from windyty.com. CZ= convergence zone.

Subtropical ridge (STR)

It looks like the next two weeks are likely to be dominated by a BFH (Big Fat High).

A BFH has formed in the Tasman Sea and is a slow-mover with a squash zone of enhanced SE/E winds and larger swells on its northern side, peaking around southern Tonga and just south of Fiji on Monday.

From Tuesday to early Thursday (UTC) the BFH is expected to weaken around NZ as a passing trough from the Southern Ocean travels across southern and the eastern NZ. This should also weaken the squash zone north of the BFH (yea).

Then the BFH (and its squash zone) is expected to rebuild until around Wed 24 Oct and slowly travel eastwards getting east of NZ next week with a lingering ridge over north NZ.

Tropics to New Zealand

The best days this week to depart from Tonga /Fiji to NZ are Wednesday or early Thursday, when the squash zone weakens for a few days.

This is a rare example of a good weather pattern for arrival in NZ, with no troughs, and once it fades later this month, I suspect we will have a succession of troughs in the Tasman Sea — and we should enjoy this weather pattern for what it is worth, even if it comes with a touch of a squash zone.

Between Tropics and Australia.

For those headed to Queensland or Coffs with the Down Under Go West Rally

A trough is hovering off the Queensland coast at present ( its arrival brought damaging hail to Bundaberg area last Thursday) but should fade by Tuesday when it feels the domination of the BFH.

So, it is looking Ok to depart from Vanuatu/New Caledonia to Australia this week.

Note that a trough is expected to reach Coffs harbour area around local Sat/Sun and then fade, and then a more substantial trough is expected to reach Brisbane around wed 24 oct and to travel east, fading near New Caledonia by Fri 26 oct—so if you depart after Friday 19 Oct then that trough become a factor.

For more info about the Go West Rally go to www.downunderrally.com/about-go-west

From Tahiti to Tonga

Mainly OK for sailing this week, but a passing trough is expected to affect Rarotonga around local Sunday 14 Oct, and a squash zone of strong 25+ knots SE winds may affect south of 18S from Niue to southern Tonga area on local Monday 15 Oct and from local Thurs 18 to Mon 22 Oct.

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If you would like more detail for your voyage, then check metbob.com to see what I offer.

Or Facebook at /www.facebook.com/metbobnz/

Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe at bottom).

Weathergram archive (with translator) is at weathergram.blogspot.co.nz.

Contact is bob@metbob.com or txt 6427 7762212

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