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

22 April 2018

Bob blog 22 April , where to get weather info



Compiled Sun 22 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.


Now that cruising sailors are on their final preparations for departing New Zealand / Australia for the warmth of the tropical Islands, ‘t’is is a good time to review the ways to obtain weather forecasts and/or ways to give position reports when at sea.


This may look like advertising, oh well, I only do it once a year. I advise those who are planning to depart to do their homework NOW, check these web sites and at least know what’s available. If I’ve forgotten something, please sting me with feedback. I have not canvassed any of the services listed below for promotion, so what you read now is purely my opinion, hopefully unbiased, except when I mention MetBob.


1. For those depending on Shortwave radio, all the Oceanic the HIGH SEAS forecast for the area SUBTROPIC from MetService is read out in English via ZLM at 0303hr, 0903hr, 1503hr and 2103hr NZST on 6224 and 12356KHz and at 0333hr, 1003hr, 1533hr and 2203hr NZST on 8297 and 16531 KHz.


The SUBTROPICS boundary changed on 13 December 2017 and the map  shows the new boundaries, see


2. With SSB there is access to the well-known PacSeaNet, offering a free-of-charge daily check-in service.


Your SSB license allows you to participate. Listen in at 0300UTC on 14300KHz in the 20 metre band.


Position reports are received and reported in the well-know YOTREPS format and displayed online. People onshore can listen in to the radio feed from the website. This net includes 17 listening station dotted between Australia and Alabama. They pride themselves in being able to listen to all yachts across the Pacific, reception conditions allowing.


3. Another SSB service is offered by Yachts in Transit or YiT. Patricia and David from Gulf Harbour Radio use the web site \to keep track of boats that listen to their rollcall/weather service. FIRST register on this web site with your boat and crew details and then you simply email or radio in your position and conditions in preferably each day ( or via SSB). These reports are plotted on a webpage for you and your friends. The website offers a link to hear the radio online, and also to view all the South Pacific AIS data.


David is on air, daily except Sunday NZ date at 1915UTC/0715am NZST on ZMH286 on 8752Khz or 8779KHz or 8297KHz. Other frequencies have been allocated for far away yachts. He first takes in reports and then, at 1930UTC/0730am NZST does a round-up of the weather in each island group, including passage weather,  from east to west across the South Pacific,


4. Those who have access to email have several options:


Saildocs may be used to relay the text details of a webpage even if you only have email and no access to the Internet. They are able to send you the latest edition of MetService warnings by sending an email, no subject necessary, to with message




For subtropics use SEND


For Fiji MetService High Sea use SEND


This system also works for Northland coastal sailors using a smart phone with email.


The formula to get a copy of the latest coastal area BRETT via email is to send an email to with message SEND


5. YOTREPS was originally setup to allow yachts with email access to file their position reports and receive weather data. It started back in 1997/1998 thanks to the inspiration of Mike Harris of SV PANGOLIN. He has retired from this now and it is being maintained by You can still use it to file your YOTREPS by email to and receive by email the Fleet code or my weathergram. I have had problems uploading my weathergram to them over last few weeks,but should be able to get that sorted.


6. Some satellite phones now provide wifi/bluetooth that allows nearby smart phones to connect to the Internet via an ap.  One of the smart phone aps that make good use of this feature is which supplies forecast model data, Observations, and, at the Professional Account level, tools for routing and comparing departure dates. It also has a position tracking tool.


And, I think, also has a position tracking option via an ap.


7. Some satellite phones now allow text messages, even if they don’t allow emails. Text messages are all that is needed by some web-based position-tracking sites such as YellowBrick or Garman InReach or Bluewater Tracks.


Of course, the AIS system allows tracking via Satellite (without  “phone”), but the display online of that data is restricted by subscription to sites such as


8.  A new provider is— using sophisticated filters to reduce the text of  a weather forecast /warning to a pithy TEXTABLE alternative, free of charge to the average user of text on any satphone. They also have a forecasting option based on NOAA weather models. They have asked me if I would like to make my Weathergram available via their system. If you’d like this, please provide me with some feedback, and I’ll decide accordingly.


9. MetBob. Ahhh yes—— I am available to help with emails or texts covering weather to help with departure date planning, waypoints for the voyage and updates along the way.


Here is a copy of my terms and services for your consideration:


There are three ways I, as retired MetService weather ambassador, may further help you with weather information:


Weathergrams (free), MetPack (a book), and voyage forecasts (charges apply).


a: Weathergrams: This is a Weathergram. I occasionally (usually on a Sunday) email out my evaluation of weather patterns around the South Pacific, aiming on what weather is worthwhile to AVOID. These are great for helping to pick windows of opportunity for good sailing weather.


Internet site is .


Illustrated edition is at


b: Mariners MetPack for Southwest Pacific: This book is available from


It is also online free of charge at


Pass that around,  as this link, in  itself, is worth a free drink anywhere, so I’m told.


c: Voyage Forecasts: When available I can compile and email weather forecasts for your voyage on the high seas in the South Pacific. Charge is $10NZ per 5 minutes with NO Goods or Sales tax component. Anything taking less than 5 minutes is called a quickie and sent without charge.


Preparation – Takes me 5 to 10 minutes (usually less than 5 so no charge), to do a weather outlook picking departure day that avoids rough weather.


Departure – Takes me 30 to 40 minutes to do a full voyage forecast, see for an example.


Updates – Takes me around 10 to 20 minutes. When underway, to get an update email or TXT me a position report and ask for an update.


I tab together the charges during the voyage and email you an Invoice via PayPal AFTER the voyage.


This may be settled via cheque or securely online by credit card on PayPal –


My PayPal name is


Forecast limitations: Weather is a mix of pattern and chaos. A forecast is just an idea from isobar/computer patterns, and chaos comes from the real world to unravel the pattern.


I combine together the data from a combination of several wind/wave/current models/patterns and use a routing program to come up with what I think is the most comfortable looking voyage, reducing it to a series of simple waypoints for you to follow.


My ideas should only be used as a supplement to official sources, not a replacement. My liability is limited to the value of my invoice. Under the Law of the Sea (UNCLOS) and GMDSS regulations: the skipper is responsible for navigation of the vessel..


End of where-to-get-weather  review==============================================




We are having a quiet period at present. The MJO phase diagram can be used to detect further activity, if you know how to read it. Basically, it says the next dose of activity in the western parts of the South Pacific may be in the Northern Coral Sea in early May, but does not look to be marked enough to do much. We shall see.


MJO Phase diagram is seen at



SPCZ=South Pacific Convergence zone.

The SPCZ is going thru a quiet period at present, and should be weaker this week than last week.

Even so, at the southeast end of the SPCZ a LOW is expected to form around 30S 155-160E around 26/27 April at the end of this week. This affects yachts sailing from NZ to French Polynesia but may help them follow the rhumb line rather than do the “east then left: triangular route.

There is still an “extra convergence zone” around 5 to 7S from SW of Galapagos around 95W all the way to west of 180. It’s not extreme but is worth avoiding. It shouldn’t really be there in late April, but c’est la vie: maybe it marks the dying part of the recent La Nina.


Accumulated rainfall for next week may be seen at


Subtropical ridge (STR)

It’s the second and final week of the school holidays in NZ, and all parents are watching the weather map for a STR to cross New Zealand, Yes, there is one. And it looks like it should travel east across the North Island on Wednesday and Thursday—something only possible in Autumn. Wednesday is ANZAC day, a day to remember war victims/heroism—and a new Peace Memorial (rather than a war memorial) is opening in Porirua, Wellington.

So, parents, you have been given your window, don’t muck it up.


As for cruising sailors, anyone attempting an early departure from northern NZ is likely to be thwarted by onshore NE wind after that mid-week High and should wait until around 1 May when the southerly wind son the backside of the following low decrease. That gels with the nominal 1st of May.


Around Tasman Sea

Problems. A low is expected to form in a trough of New South Wales, south of Lord Howe Island. This is expected to travel across North island don Friday /Saturday, mucking up last weekend of school holidays.

Opportunities: That low should kill the trade winds between New Caledonia and Australia and offer OK conditions, at least for motoring, from Australia to New Caledonia.


Panama to Galapagos /Marquesas

For sailing from Panama, there is expected to be some moderate northerly winds on Monday. After that the winds are likely to switch to light southwesterly. So, if you are waiting to go, go Monday.

As from getting from Galapagos to Marquesas this week, first motor sail to around 5S 95W (may also find a tail current), then can sail direct, but that “extra” convergence zone continues to straddle 5 to 6S from about 90W to beyond 120W. Something to avoid.



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

Feedback to or txt 6427 7762212

I’m on Facebook at /

Weathergram text only (and translator) is at

Weathergram with graphics is at, Subscribe/unsubscribe at the bottom. Or, to unsubscribe, send a reply email saying LEAVE.


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