Bob Blog 3 June 2018



Compiled Sun 03 June 2018

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.

Weather trend over the last month.

Sea Surface temperature anomalies as at end of April may be seen at


Overall, a quick glance shows more warm anomalies than cool, so there is a net discontinuity in our oceans. It is becoming blindingly obvious, and any politicians ignoring this need to be voted OUT for the sake of our offspring.

Looking at the details, some areas of the planet are almost opposite from what they were at end of March. Now we have sea temperatures in the south Tasman Sea below normal rather than well above normal, and there are warm rather than cool anomalies near the Galapagos Islands.

The Gulf Stream off the east coast of North America has moderated.

Warm anomalies continue around Philippines and between Mexico and Hawaii, an indicator to a busy cyclone season there over next few months.

To see how the annual weather cycle and the seasons are working out, here is a quick look at the average isobar maps from

Average isobars for past 30 days and their anomaly for MAY


The isobar maps show that subtropical ridges are looking strong in North Pacific an North Atlantic, but weak in the South Pacific. The large HIGHS over Australia and South America are around 160degrees longitude apart, suggestive that WAVE TWO is dominant in the upper flow of the Southern hemisphere and blocking highs are on the cards.

Zooming into the NZ area, the 1015hP (between blue and white) isobar has travelled north over the area east of NZ indicating an abundance of SW winds. Strangely a 1025 (green) isobar has formed over Australia. This helps to intensify the SW winds over NZ.

April clip_image006


The last 30 days of rainfall, and its anomaly, as seen at TRMM at


The rain map shows extra convergence in the ITCZ across the Arabian sea, across the North Pacific Ocean, and into the Caribbean/Florida area – most of this is attributable able to early season cyclones. This may be indicative of a busy northern hemisphere cyclone season.

In the Southern Hemisphere there are large dry regions: Around Madagascar, Australia, South Pacific Convergence Zone, and Brazil. NZ seems to be having a positive share of rainfall, no doubt thanks to its lower than normal isobars.


The Indian Monsoon is arriving a few days ahead of normal as seen at


There are a couple of tropical depressions in the NW Pacific, and one of them may develop further as it travels northeast to the east of Japan. If you are intending to travel I this area, stay alert.

If we compare the past week’s rain map with the previous week we can see a build up of activity over Indonesia and along the ITCZ across the North Pacific.



– see



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

SPCZ=South Pacific Convergence zone.

The SPCZ is expected to stay put from Solomon island to Vanuatu to southern Fiji. It is expected to have a quiet week between Tahiti and Tonga. A tropical LOW is expected to form between New Caledonia and Fiji by end of the week and the travel south this weekend towards northern NZ.

clip_image019 clip_image021

Accumulated rainfall for next week from

Subtropical ridge (STR)

A High is expected to build east of NZ near 30S 160W on Monday and travel east along 30 to 35S this week.

Next High is expected to move into central Tasman sea on Thursday and weaken over central NZ on Saturday and then travel quickly further east on Sunday.

Around Tasman Sea, NZ to tropics /FP

A Tasman LOW is poised to travel southeast across the North Island on Queen’s Birthday Monday, followed by a vigorous cold and squally SW/S flow on Tuesday and Wednesday (stay put). There is expected to be a brief easing of conditions on Thursday and Friday thanks to a passing ridge, BUT by Saturday and on Sunday, strong to gale easterly winds are expected over northern NZ on the approach of a low from the direction of Fiji. Yachts heading northwest to Noumea should be able to depart Ok on Thursday.   Yachts travelling north or northeast capable of 240  or more miles per day may be able to depart Thursday and escape the next incoming low, but slower yachts should perhaps stay put and await a better-looking voyage, maybe around Thu 14 Jun,  on the approach of the next High.

Australia to tropics

Too many head winds easterly this week, but maybe Ok to depart this weekend.

Galapagos /Marquesas

From Galapagos area to Marquesas, departure can be any time this week.

Best path for avoiding direct down-windsailing is to go to 11S 135W, then go direct.


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

Leave a comment

Please log in using one of these methods to post your comment: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.