Bob McDavitt's ideas for sailing weather around the South pacific

06 December 2015

BOB Blog 6 Dec 2015



Issued 06 December 2015


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.


The Chennai (India) floods death toll is over269, and the Cumbria (UK) flooding/wind death toll attributed to “Winter Storm Desmond” is 1, so far.



The averaged isobar anomalies for November, as seen at

show that the lowest lows have been in the Arctic, Southern Ocean near NZ,  the south Indian Ocean and off the Mexican west coast.

During the next month we can expect the low anomalies that are now near Mexico to drift south toward Tahiti.


Tropical Cyclones

There are currently no tropical cyclones around. However another tropical depression is being picked by GFS model to form near 5N 145W by mid-week.

There is expected to be an eastwards progression of active convection from the Indian Ocean into the Coral Sea region later this month,

and the likelihood of formation of a tropical cyclone in the week finishing 25 Dec may be seen from Meteo France at caledonie/cyclone/coin-des-experts (click on the three overlaid diagrams for the latest).


The Weekly rain maps, as seen at,

show rain concentrations in TUNI during the past two weeks, and a build up of rain in the Indian Ocean (and around Chennai).



SPCZ=South Pacific Convergence zone.

The main part of the SPCZ remains strong in activity and extends across Tuvalu/ Tokelau and Northern Cooks.

Another weaker convergence zone is lying along 15 to 17S from Vanuatu to Fiji.


STR= Sub-tropical Ridge

High is bending around south side of Tasmania tonight and expected to travel NE across the Tasman Sea this week and linger to north of NZ from Friday to Sunday.


Over NZ/Tasman:

Weakening front travelling off to north of NZ tonight followed by SW flow on Mon/Tues then a W to NW flow over the North Island for remainder of week. Next front is expected to travel onto North Island late Sunday 13 Dec, associated with a deepening low skirting southern NZ.


Travelling Tahiti to Marquesas.

The trough associated with the low that once was TC TUNI is expected to travel north across the Tuamotu region during next few days and weaken- This should bring SE/E winds between Tahiti and Marquesas until mid-week allowing a rare opportunity to sail this route.


Between Tropics and NZ:

The subtropical ridge is laying down a curtain of light winds along 25 to 30S.

Fronts over Northland are weak and seem to be arriving on late Sundays at present.


See my yotpak at for terms used.

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