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

29 April 2018

Bob Blog 29 April



Compiled Sun 29 April 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.

FIVE Amendments/additions to last week’s blog.

1.For those depending on Shortwave radio, remember that ZLM / Taupo Maritime Radio offer a continuous 7/24 Trip reporting service see

2.Northland Radio ZMH292 is owned and operated by Peter Mott and provides free of charge check in service on multiple maritime frequencies.  Note that Peter is NO LONGER a coordinator for PACSEANET.  Northland Radio tracks vessels and has a formal policy for dealing with a missed check in.   To use Northland Radio, operator requires Maritime Restricted Radio Operators Certificate (MRROC).  In the maritime radio service, the callsign is assigned to the vessel, and in New Zealand it starts with ZM. See

3.PACSEANET is a ham (amateur radio) network providing a free of charge check in service on amateur frequency 14300KHz USB in the 20 metre band (at 0300UTC).  To participate, operator needs to hold an Amateur Radio Operators Certificate (General class or above).  In the amateur radio service, the callsign is assigned to the licensed operator, so this is a different callsign from using a maritime callsign.  In New Zealand amateur callsigns start with ZL.   See

4.EMAIL: To get a one-off weathergram via email:

Send an email to, no subject needed with message SEND nz.wgrm

Or Send an email  to, no subject needed with message WEATHERGRAM


To subscribe/unsubscribe to Weathergram

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5.And exciting NEW information

In association with  we have set up two new ways to subscribe to WEATHERGRAM

long – (this has all the text), ideal for those using sat phone or HF SSB with sailmail/winlink and

short - for those using satellite messengers such as Garmin inReach—reducing the weathergram to 4 text messages.

To subscribe, email the message (no subject needed) "subscribe boatname" to for long version or to for short version. Boatname has to be unique and less than 20 characters long.

Once subscribed you will receive weekly weathergram in short format optimised for satellite messenger. You also will be able to send message to to ask Bob a question. The Boatname that you used when subscribing will be used to sign your message.



There is expected to be a weak MJO burst of extra energy travelling across Northern Australia to Coral Sea during the next two weeks.  This increases the risk of tropical cyclone formation.

One has formed in the Indian Ocean near 12S 88E between Cocos and Chagos Islands.




SPCZ=South Pacific Convergence zone.

The SPCZ has been reasonably quiet for past few weeks and is expected to gradually become more active over the next few weeks.  This week its activity should be focused on a line stretching from Solomon Islands to northern Vanuatu to southern Fiji.

The “extra convergence zone” around 5 to 7S from SW of Galapagos around 95W to 110Wis still there but fading. 

Accumulated rainfall for next week is seen at


Subtropical ridge (STR)

HIGH is expected to travel east this week, into central Tasman Sea south of Lord Howe island on Monday and Tuesday, then onto central NZ by Thursday and Chatham Islands by Friday, then off to the east.

Around Tasman Sea

Low is expected to cross northern NZ on Monday and then should move off to the east from Tuesday.   There is likely to be a SQUASH ZONE of strong SE winds just NE of NZ on Thursday between the new HIGH and the old Low.  This zone at its peak may have swell over 5 metres from the southeast so is worth avoiding.

Should be Ok to depart from northern NZ for the tropics after that squash zone, maybe on Thursday- such a voyage may encounter NE winds near 26S on Sun/Mon 5/6 may,  but these can be accommodated with waypoints.


New Zealand to French Polynesia

That Low travelling east asway from NZ with a squash zone on Thursday  is likely to delay a comfortable start from NZ until Thursday (but perhaps a start  from Auckland southwards may be done late Wednesday).  Those who departed last week should make their way to around 28S to get on the right side of this system.


Panama to Galapagos /Marquesas

For sailing from Panama, there is expected to be some moderate northerly winds early n the week and the best-looking day for departure is YUESDAY (local). Will need to work in with SW/S/SE winds from 5N onwards.

From Galapagos area to Marquesas, departure can be any time this week. Best path for wind and current is to motor/sail to 5or 6S 95W then go west to 125W and then go direct


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

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