Bobgram 15 June

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 15 June 2025
HOW TO EVADE THE WORST
The "Law of storms" or more pedantically correct "Law of Gyration,"
(or the law of the rotation of winds) was compiled in 1860s to help
sailing master mariners know which way to sail when encountering the
winds that rotate around storms. These were compiled soon after the
birth of weather maps with isobars and around 50 years before the
birth of weather maps with fronts.
Here is a link to the original article thanks to STARPATH
https://www.starpath.com/resources2/Practical_Matters_from_Dove.pdf
Around 30 years ago during the (in those days) Queens Birthday in
early June 1994 a fleet of yachts sailing from New Zealand to Fiji
encountered a deepening Low that formed off the southeast of Ne
Caledonia.
This became known as the "Pacific Storm" and prompted me to collect
together notes about South Pacific sailing as the MetService Mariners
Met Pack. This is still available at
http://about.metservice.com/our-company/learning-centre/mariners-met-p
ack/

As part of that booklet, I revisited Dove's "Law of storms" and
produced these two flow charts, reproduced in my illustrated
weathergram for your educational enjoyment at
https://metbob.wordpress.com/2025/06/16/bob-blog-15-june/



TROPICS
The latest cyclone activity report is at zoom.earth and
tropic.ssec.wisc.edu and Tropical Cyclone Potential is from
http://www.ospo.noaa.gov/products/ocean/tropical/tcfp/

Tropical Storm Wutip drenched South China's Hainan and Guangdong
provinces as the first named storm of the typhoon season. . Tropical
Storm Cosme , short-lived Hurricane Barbara spun up off Mexico's
Pacific coast followed by DELILA

WEATHER ZONES
Rain accumulation this week from Windy.com shows a well-defined South
Pacific Convergence zone from Solomons to Samoa.

Wind and rain accumulation this week from Windy.com shows enhanced SE
winds in the Coral Sea and around L1 east of New Zealand.
LOWS and HIGHS
LOW L1 tonight comprises of several tight centres forming under a jet
stream between 25 and 30S and in area north of NZ. These should gel
into one on Monday and then travel southeast and deepen in the
subtropics. There is likely to be a lull on the tropical side of L1
along with a passing trough over Niue on Monday/Tuesday and Southern
Cooks mid-week. This passing trough is looking to be mediocre in the
tropics. However, L1 has strong winds around it
HIGH H1 in south Tasman Sea is expected to spread across central NZ
mid-week and then travel east from 40S to 30S when east of NZ. After
Wednesday it may enhance the trade winds on its northern side,
especially between Niue and southern Cooks.
Low L2 is expected to cross Tasmania on Tuesday and then southern New
Zealand on Thursday followed by a southerly flow over NZ on Friday.
This is followed by H2 travelling between 30 and 40S crossing New
South Wales on Wednesday and northern NZ on Saturday/Sunday.

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If you would like more details about your voyage, check metbob.com
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 text 64277762212.
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