Bob Blog 13 Feb

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.
Compiled Sunday 13 February 2022

Where to put your AIS Antenna?
Here's an article update from Peter Mott of Passage Guardian about this
topic.
passageguardian.nz/pages/best-practice-ais-for-bluewater-sailing-yachts
Conclusion
A radar arch or stern post mounted antenna should deliver reliable satellite
reception, whilst permitting detection of cargo ships out to at least 20nm.
I have experience tracking vessels conducting circumnavigations that have
experienced knock downs and have lost everything on the mast head. The AIS
antenna mounted on the radar arch continued to operate normally.

Tropical Cyclone DOVI
DOVI's steering field around and above it took it south and then southeast.
Windy.com is a good resource for viewing this.
Here is link to animation of wind flow around DOVI as it crossed NZ. :
t.co/G9J3IbWHuz Watch this and see how the southerly gale wind arrives in in
Cook Strait BEFORE the Low made landfall. Hence the saying "It isn't so much
Wellington that blows, it's also Auckland that sucks"
And in the illustrated edition of this blog is a MetService manual analysis
of the situation at local 6am Sunday. showing detailed isobars around DOVI.

When I was at MetService in the days before automatic weather stations, it
was this dawn analysis (when the lighthouse keepers started the day) that
was the most important map of the day and we would spend up to an hour
drawing and watching it. Where the isobars bunch together the winds blow
stronger, so isobar=spacing matters. Also note the orographic trough leeward
of the Alps-Aotearoa.

TROPICS
DOVI formed in the Coral Sea and moved east onto Vanuatu then south past Nee
Caledonia into the Tasman Sea then southeast across North Island.
There is a zone of high potential for formation this week to northwest of
Australia.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
The SPCZ is less active than last week relaxing after a few heated weeks. m
Vanuatu/New Caledonia to Fiji. A trough forming over southern cooks and
south of there by mod-week is expected to drift westwards later in the week.

HIGHS and LOWS
The remains of DOVI are tonight east of North Island and travelling fast
eastwards and fading.
High H1 should remain slow-moving to southeast of French Polynesia this
week.
LOW L1 is expected to form in a tropical trough south of Southern Cooks by
mid-week and then go southeast.
High H2 tonight in the Tasman Sea is expected to travel east along40S
crossing central NZ on Thursday.
Another trough should cross NZ this weekend.

With H2 it is OK to travel from NZ to Australia this week, but difficult to
go the other way.
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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 64277762212
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