Bob Blog 29 Jan 2017



Compiled Sun 29 January 2017

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 Tropics in the South Pacific/Australia region are starting to show signs of life, with a Tropical depression today off the NW of Australia travelling West and then likely to go WSW into Indian Ocean.


There is a pulse of extra convection now in the Indian Ocean and travelling eastwards towards Australia. This is a Madden Julian Oscillations. It is expected to weaken as it moves across Australia next few weeks but may intensify when it reaches South Pacific by mid-February. This area of enhanced convection shows as a bubbly blue area in the OLR (Outgoing Longwave Radiation) extrapolations that may be seen at


We can see the enhanced rain in the Indian Ocean that is associated with this MJO in the past two weekly rain maps. Another trend shown by these two maps is the burst of heavy rain two week ago near Tahiti (by a passing depression), now relaxing. Also, we can see that the ITCZ is intensifying near Indonesia and Majuro.



Rain for the past fortnight from


Weather Zones (see text) as expected mid-week on Wednesday (GFS model) showing wind, isobars, current, swell black arrows / Sig wave height purple lines, SPCZ and STR.


SPCZ=South Pacific Convergence zone.

SPCZ is expected to stretch from Solomons to Southern cooks.

A topical depression is expected to form to south of French Polynesia on weekend of 4/5 Feb local. Later this month we can expected deeper developments so if you want to avoid cyclones and Island hop, then this is your week, and no later.


Tropical accumulated rainfall for next week from

Subtropical ridge (STR)

Highs near 35S over northern NZ for Auckland Anniversary weekend is expected to move off to the east during the week.

For Waitangi Day-weekend a High is expected to travel east across central NZ on Sat/Sun followed by a ridge over northern NZ on Monday. Bon chance.

Tasman Sea/NZ Area troughs.

A front is expected to travel NE across South Island on Tuesday and Wednesday, then stall and fade over southern North Island on Thursday. This is followed by a southern dip in the Sub tropical ridge/ STR


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