Bob's Blog

WEATHERGRAM

YOTREPS

 

Compiled Sun 22 September 2019

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.

 

Equinox is tomorrow NZ time. Monday at 7:50pm ( 25 0725 UTC)b

At this point in time the overhead sun is directly over the equator, shifting from the northern hemisphere to the southern hemisphere.

If you check sunrise /sunset times for your place for Mon 23 Sep, you will find that these compute to something like 12hr 7mins of sunlight. This is because sunrise and sunset are defined with respect to the top limb of the sun, rather than the centre of the sun, and that adds a few minutes of sunlight to the day. You’ll find (if you look) that the day that has closest to exactly 12 hours of daylight, called the equilux, is around three days earlier than the September equinox.

In New Zealand, the change to NZDT Daylight time occurs at 2am (becomes 3am NZDT) on the last Sunday of September, and so that’s 29 September. Clock goes forward I hour.

The change to daylight saving occurs on different dates for the nations around the South Pacific so I think it’s a good idea for you to have a summary for reference

 

Date Place Daylight saving time zone

29 Sep New Zealand UTC+13 (NZDT)

29 September Samoa UTC+14 (NZDT

29 Sep Chatham Islands UTC+13h45mins (CHADT)

6 Oct New South Wales, Tasmania UTC+11 (AEDT)

6 Oct Lord Howe Is. UTC+11 (AEDT) (30 minute ahead)

6 Oct Norfolk Island UTC+12 (AEDT)

10 Nov Fiji UTC+13 (Fiji Summer Time FJST)

No changes in Tonga or American Samoa or Vanuatu or Queensland/Northern Territory/Western Australia or New Caledonia.

 

As yachts start their end-of-spring migration, with the approaching South Pacific Cyclone Season, nominally on 1 November (starting at low risk). it is also useful to have a summary of the various national holidays, as these limit available departure dates.

 

From East to west

French Polynesia 1 Nov All Saints Day, 11 Nov Armistice day

Cook Islands: Mon 28 Oct Gospel day

Niue: Oct 19 to 22 Constitution day celebrations, Oct 25 is Gospel day.

Tonga Nov 4 Constitution Day

Fiji Oct 10 Fiji Day, Oct 28 Diwali, Nov 11 Prophet Mohammed’s Birthday.

New Caledonia Sep 24 National Day, 1 Nov All Saints Day, 11 Nov Armistice Day .

New Zealand Oct 22 Labour day.

Australia: OCT 7 Labour Day (ACT, NSW &SA), Queen’s Birthday (QLD)

 

THE TROPICS

The latest cyclone activity report is at tropic.ssec.wisc.edu and TCFP tropical Cyclone Formation Potential at www.ssd.noaa.gov/PS/TROP/TCFP/index.html

 

At present there are five active Cyclones JERRY and LORENA and MARIO and KIKO and TAPAH and several areas of potential activity in North Atlantic and North Pacific. ‘

 

WEATHER ZONES

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to stretch from Solomon Islands to Samoa.

Squash zone of enhanced SE winds on north side of a passing HIGH on MONDAY from Vanuatu to Samoa/Tonga easing on Tuesday.

Passing trough over southern Cooks/ parts of Tahiti on local Sunday/Monday followed by fresh SE winds on local Monday.

 

Subtropical ridge (STR)

The STR briefly visited 40S over NZ last week. It is returning to north of NZ this week

HIGH to NE of NZ on Monday travelling east along 30S around 1024, so no squash zone.

Next HIGH forming in Tasman Sea by Wednesday to travelling NE to 30S then travelling east past northern NZ by Sunday.

 

Tasman Sea /NZ/Aus

Trough over northern NZ on Tuesday, followed by a SW swell until Friday, strong on Wednesday, easing by weekend.

Another Front is expected over northern NZ Monday 30 Sep followed by southerly winds reaching as far north as Fiji by Wednesday 2 October and Tonga by Thursday 2 October. No good for trips from tropics to NZ arriving next week.

For Noumea to Aus: OK at first but interrupted by a passing trough on Sunday Monday 29/30 Sep with light winds/

 

Tahiti to Tonga: Try and time your voyage after the passing trough (affecting parts of Tahiti on local Sunday /Monday) so depart from Tuesday.

 

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

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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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