Bob Blog 09 Feb



Compiled Sun 09 Feb 2020

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 Madden Julian Oscillation is an occasional visitor to the Pacific (as a burst of extra convection that can trigger cyclones). It usually takes 10 to 20 days for the active part of an MJO event to travel across the Pacific

Another parameter that helps us watch convective patterns in the tropics is Outgoing longwave radiation or OLR. When the tropical convergence zones are active their cloud blocks radiation from escaping to outer space, and OLR is low, coloured blue (for bubbly). When skies are clear radiation can escape to outer space and OLR is high, coloured orange or (mellow) yellow.

A constructed analogue forecast of future values of the OLR, using the MJO, show that we are expected to have a phase of low OLR (blue values) over the next few weeks, and that means an active South Pacific convergence zone and increased cyclone risk .

Deeper blue indicates less OLR and that means MORE convective activity.


As seen at


The Tropics

The latest cyclone activity report is at and TCFP tropical Cyclone Formation Potential at (but not this week).


Tropical Cyclone DAMIEN was very active when it made landfall near KARRATHA in NW of Australia and is now weakening as it moves inland.

Tropical Depression 06F is brewing west of Vanuatu, 994hPa tonight near 16S 163E, and likely to become a tropical cyclone going southwest and skirting the NW end on New Caledonia on Monday. The system is then expected to make a beeline SW and parallel to the Queensland coast passing by Brisbane on Friday and getting into the south Tasman Sea by the weekend.


Weather Zones (see text) as expected Wednesday 00UTC showing isobars, winds, waves(magenta) STR, and SPCZ. Pink area = lightning likely (high CAPE)


SPCZ=South Pacific Convergence zone.

The SPCZ is active this week across the Coral Sea, Vanuatu, Fiji and Tonga.

I have already mentioned the tropical system near Vanuatu

The cyclone risk remains high in the South pacific and there may be another forming near Fiji /Tonga by the weekend. Take care and get updates if planning to Island hop.


Accumulated rainfall for next week from (isobars are for Sunday night).

Subtropical ridge (STR)

HIGH over southern Tasman Sea is expected to slowly travel NE across central NZ on wed /Thu.

Another High is expected to travel into south Tasman Sea on Friday heading for east of the South Island over the weekend.

Tasman Sea /NZ/Aus

Weak trough is expected to cross NZ on Thursday

As for sailing across the Tasman: probably a no-go this week due to possible cyclone

From Panama to Galapagos/Marquesas:

Northerly winds to around 4N.

Then a weak ITCZ and variable winds from 4N to 2N (will need some waypoints).

There is expected to be a slight change in a pattern in the wind direction north of Galapagos This is expected to swing from easterly to light to westerly from mid-week. There are some great west-going currents north of Galapagos, but once this wind direction change occurs we will need to try and go SW of Galapagos instead.

The main problem with the “SW of Galapagos” voyage is some southerly winds forecast between 2N and 2S. These will require waypoints.


If you would like more detail for your voyage, then check to see what I offer.

Or Facebook at /

Weathergram with graphics is at (subscribe/unsubscribe at bottom).

Weathergram archive (with translator) is at

Contact is or txt 6427 7762212


Published by metbob

Pattern and Chaos

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