Bobgram

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.

Today, 13 July is "Seafarers Sunday". On this day several churches pray special prayers for mariners and those who livelihood involves working on the ocean. This often-dangerous job, at mercy of winds and waves, requires spending weeks away from loved ones.

Over the centuries, seafarers have worked out rules to help avoiding sailing into the right parts of passing storms. Storms are often related to passing depressions or low-pressure systems as seen on a weather map. One of these rules is the "law of storms" as compiled in the mid-19th century (see metbob.wordpress.com/2025/06/16/bob-blog-15-june/)

Basically, this can be summarised that the way to go, to evade the roughest weather is to the right of the incoming wind.
Buys-Ballot law was compiled at much the same time. In the Southern hemisphere it can be stated thus: If you look into the wind then the LOW is on the left. This means concurs with the "law of storms" to go right or put wind on port in order to evade the worst of the storm.

However, when your voyage involves encountering a passing trough then the best thing to do is to put the incoming wind on starboard and sail directly into the approaching rain. By so doing we MINIMISE the time spent in the peak conditions of the trough. This is a case where the way to go is on a starboard tack, the opposite to the law of storms. My illustrated edition today at metbob.wordpress.com/2025/07/14/bob-blog-13-july/ gives more details of this exception.


TROPICS

* Typhoon Danas in Taiwan killed two people, and more than 300 were injured.
* Two deaths are being blamed on the flooding unleashed over the Carolinas by Tropical storm Chantal.
* TC NARI is affecting east coast of Japan.

WEATHER ZONES
Rain accumulation this week from Windy.com shows well defined SPCZ between Solomon Islands and Samoa. Also a passing trough southeast of French Polynesia .

The wind accumulation shows NO squash zones in the tropics, but the westerly winds of the "roaring 40s" are extending north of 30S around the south Pacific.
LOWS and HIGHS
Low L1 near 35S and 145W (to southeast of French Polynesia) is travelling southeast and associated trough is expected to pass by Tahiti late this week, bringing small squalls and then a lull.
HIGH H1 near 25S over Queensland is expected to stretch eastwards and keep a weak subtropical ridge between 25 and 30S across the South Pacific. taking a southern route from South of NZ along 45S.
Low tonight to NE of New Zealand is expected to travel south along 180. From mid-week on its front a secondary Low L2 is expected to form near35S and south of the Cooks Islands (near 160W).
Low L3 is expected to form over inland Australia on Tuesday then cross the Tasman on Wednesday and NZ on Thursday. Later in the week is may expand into a multi-system trough east of NZ.
L3 is followed by HIGH H travelling along 3o to 40S S and reaching NZ around Sun/Mon 19/20 July.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
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.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>