Bob Blog 15 Jan 2017: When do we sail to Panama/Marquesas?

WEATHERGRAM

YOTREPS

Compiled Sun 15 January 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.

A new edition (the third) of The Pacific Crossing Guide by Kitty Van Hagen is now available, and this edition gives reference to MetBob as well., so I recommend it as a useful source of info if you are planning on voyaging around the South Pacific this year.

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Google it and buy form you favourite supplier/Bookshop. The nearest to me is www.boatbooks.co.nz/cruzeswpac.html#30125

ANTARCTICA CUP

This week Lisa Blair is setting off for the “Antarctica Cup” racetrack, departing from Albany in southwest Australia. http://www.acronautic.com/antartica-cup-ocean-race/

I consider her to be a worthy sailor and I shall be sponsoring this adventure by watching the weather for her.

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Lisa is doing this to spread the word about Climate change—her vessel has been renamed CAN for Climate Action Now. This is indeed a worthy cause and I encourage you to track her proceedings at lisablairsailstheworld.com/blog or http://www.facebook.com/LisaBlairSailstheWorld/ and spread the word.

Her departure was meant to be today but has been delayed a few days by an electrical fault.

When is it best to depart America for Galapagos/Marquesas?

The South Pacific cyclone season ends in April, and the Northeast Pacific cyclone season starts in June, so it is generally understood that the best time to depart San Diego or Western Mexico or Panama for Galapagos or Marquesas is between mid-February and early June, crossing the equatorial area between cyclone seasons.

In an El Nino year there is a low risk of strong winds near Marquesas in April/May – but this is NOT an El Nino year. Departing too early means possibly being caught in a zone of light winds between equator and 10S , especially east of 100W, but there are usually some useful currents to follow. One thing I’d like to point out, is that soon after the March 21st equinox (when the overhead sun starts shifting northwards into the northern Hemisphere) the prevailing winds between Panama and the equator swing from “occasionally NE” to “mostly SW”, so that makes departures from Panama in April onwards difficult.

This can be gleaned by checking the monthly averaged ocean winds from Scatterometer data as gathered for sailors by the crew of at SV PITUFA at http://www.pitufa.at/oceanwinds/

 

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The Tropics are still having a quiet period between active cyclones. There is a little activity over the sea off southeast Asia: Tropical depression 01W (ONE) is heading for southern parts of Vietnam, as seen at metoc.ndbc.noaa.gov/

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Rain maps show that activity is on the decrease around Indonesia and SE Asia, and on the increase around central and NE of Australia

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

WEATHER ZONES

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Weather Zones (see text) as expected mid-week on Wednesday (GFS model) showing wind, isobars, current, swell black arrows / Sig wave height purple lines, SPCZ and STR.

SPCZ=South Pacific Convergence zone.

SPCZ is active this week mainly east of 180, and this reflects the warmer than normal sea temperatures between Fiji and Tahiti. The depression that is tonight to south of Niue (and has been around a few days now) is expected to remain slow-moving and fade by nid week. However, a new LOW is expected to form to southeast of Rarotonga and south of Papeete on Wednesday, and this feature should deepen and travel slowly east late this week, bringing squally NW winds to parts of FP French Polynesia and cooler clearer southerly winds+ SW swells to Southern Cooks.

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Tropical accumulated rainfall for next week from windyty.com

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Sea Surface temperature anomalies as seen at http://www.ospo.noaa.gov/data/sst/anomaly/2017/anomp.1.12.2017.gif

Outlook for next cyclone: Still too far away to be sure, but Meteo France are picking an increasing likelihood of tropical cyclone formation over Vanuatu between 22 and 28 Jan as seen at www.meteo.nc/nouvelle-caledonie/cyclone/coin-des-experts

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This prognosis takes into account the MJO cycle (rather weak at present) and sea surface temperature changes.

Subtropical ridge (STR)

High in North Tasman sea on Sunday is expected to fade over northern NZ by Wednesday.

A new High is expected to spread into the south Tasman Sea on Thursday, and cross NZ area on Friday.

Tasman Sea/NZ Area troughs.

A deep low is expected to cross southern NZ on Wednesday bringing strong winds and a brief cold SW change on Thursday.

After that Thursday/Friday High, be on watch for a LOW from central Australia to deepen quickly over the warmer than normal seas off Sydney on Friday, and then deepen more as it crosses Tasman Sea on Saturday and central NZ on Sunday/Monday. Avoid.

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