Bob Blog 27 Nov

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 27 November 2022


Lightning strikes over New Zealand: Waikato takes 1st place

Lightning strikes recorded last week over New Zealand (16 – 25 November).

Last week, between 16 – 25 November, the Aotearoa / New Zealand region saw 91,349 lightning strikes (Source: MetService), with around a 1/3 of those situated over the land. All regions of the country have experienced significant lightning activity, however of all the regions around the country, the Waikato Region takes 1st place with 4,255 lightning strikes over the period, followed by Westland (3,114) and Hawke’s Bay (2,970). Dunedin had the lowest recorded number of strikes, with 42 recorded over the 9-day period.


Lightning is the most damaging weather hazard for yachts. When you anticipate it, the standard recommendation is to put some hand-held nav instruments in the gally oven for protection for the duration, so if the yacht is hit and losses its electrics, not all is lost.

When we have unstable air in the chimney of a shower cloud, rising water droplets bash into sinking ice crystals and all that rubbing together rips off electrons that float to the top, leaving an accumulating positive charge at cloud base. Lightning occurs when the air between two electrically charged regions can no longer keep them apart. The average discharge is several gigajoules.

To put this in context, between the 9 days between 16-25th November approximately the same amount of energy was discharged into the atmosphere (or ground) as that either generated by the New Zealand National Grid or consumed within all industry sectors in New Zealand  (Source:


The latest cyclone activity report is at and and Tropical Cyclone Potential is from


There are no named storms at present. There is a zone of potential development in the China Sea.


Weather Zones Mid-week GFS model showing isobars, winds, waves (purple), rain (red), STR (Subtropical Ridge), SPCZ (South Pacific Convergence Zone) CZ (Convergence Zone) and CAPE (lime)


CAPE maps mid-week GFS from Predictwind, showing chance of lightning


Rain Accumulation next five days from


The SPCZ is somewhat quiet from Solomons to north of Fiji, then has an active convergence zone/trough over southeastern parts of French Polynesia.


HIGH H1 has been south of French Polynesia for a while is this week expected to go off to the northeast.

HIGH H2 now between Fiji and NZ is expected to travel east along 30S.

HIGH H3 should stay slow-moving in the south Tasman Sea this week, and move onto NZ at end of the week, breaking the spell of wet weather

LOW L1 formed over Wairarapa today, cancelling the Wellington Santa parade, and is expected to travel off to the east southeast.

LOW L2 is forming around New Caledonia area and expected to deepen as it travels southeast

is expected to travel across the south Tasman Sea.

LOW L3 should travel east across the south Tasman Sea.

LOW L4 is expected to deepen off Bundaberg and travel across the north Tasman Sea late this week.

So, things are busy this week in the South Pacific, and changeable, but NZ looks good for arrival from 3 to 6 December.


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