Bob Blog 12 Jan 2020



Compiled Sun 12 Jan 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.

MJO (Madden Julian Oscillation) active phase is visiting the western pacific

The Madden Julian Oscillation is an occasional visitor to the Pacific (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

(as seen on the phase diagram at


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 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.

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


Cyclone CLAUDIA is travelling westwards offshore of the NW Australian coast.

A tropical low just SE of Solomon Island s is likely to deepen into a Cyclone over northern Vanuatu on Monday and continue SE to Fiji by Thursday and maybe skirt south Tonga on Friday/Saturday and then go south to east of NZ next week.


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 from Solomon Islands to Tonga, with a tropical cyclone travelling SE/ SSE along this path. Not a good week for Island hopping.


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

Subtropical ridge (STR)

HIGH east of NZ over 1020hPa is expected to linger near 40S 160W until mid -week and then fade.

High in the Tasman sea today is expected to skirt around the South Island and then to travel east

to east of the South Island along 45S.

Tasman Sea /NZ/Aus

A trough over the South Island is expected to weaken over the North island on Monday.

This should be followed by a SE flow maintained by the High east of the South Island.

For Noumea to Aus: Mainly SE winds so OK.


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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