Receiving Weather Underway

Weather Information Sources for Cruisers- emphasis on the South Pacific but applies to all areas.

This was compiled by Ventana in March 2002 (with minor updates in 2003).  It was primarily intended for cruisers possessing a familiarity with these subjects.  It has had minor modifications to clarify things for those less experienced.  For more info feel free to email us at ventanaweb@aol.com.

The basic weather data is usually gathered by the various governments involved. Once the data is collected forecasts are made by the governments and any number of private entities using various computer models. Often you may pay a private source for the same info that is available for free. The raw data crunched by different modeling programs will often come up with forecasts that differ in their predictions and accuracy.  In remote areas of the Pacific there are few stations to provide the raw computer data.   Like anything on a computer it is GIGO- That is garbage in garbage out.

The majority of outside weather information will arrive to cruisers via HF radio via voice weather broadcasts, weatherfaxes or email reports. Satellite phones will give you more options that are not covered here.

Email Reports
By far the best source of onboard weather is via Winlink email reports.  Winlink is a totally volunteer effort set up by a number of US based amateur (ham) radio operators.  Winlink provides to sea going ham radio operators a system of onboard email and a huge list of worldwide weather and news bulletins.  Besides complete weather bulletins for the Caribbean, Atlantic and Pacific oceans you can get everything from the latest news in St. Petersburg, Russia to the weather forecast for South Africa - all available nearly instantaneously from Winlink.  To use Winlink you must be a General Class ham radio operator and you need a ham or marine SSB radio, a radio modem and a computer.  Most cruising boats have a radio and computer on board.  The modem costs about $600.  The daily usage is free.  The free computer software to connect to Winlink is called Airmail.  I may have used the terms interchangeably in this document. 

 To visit the Winlink website click here

Non hams who have email capability (Sailmail or others) can also get various emails with detailed weather from saildocs.com or buoyweather.com. 

For non hams another method to receive weather is via weatherfaxes broadcast by the various government stations.  To gather these you need an SSB or shortwave radio and a computer.  There are various shareware programs that will help you convert the data so you can see it on your computer.  Popular ones are JVComm or MScan Meteo.  XAXERO/Coretex also makes a non shareware program to do the same thing. 

Real-time satellite pictures showing cloud cover are available with dedicated receivers and software.  These systems are larger and more expensive than most cruising sailboats will want.

Voice Weather Reports
Voice Weather Reports would include USCG and other countries voice broadcasts as well as information on the various cruisers nets.

Winlink and Email Reports
Winlink/Airmail provides reports directly from the internet to you as well as functioning as a full service email program.

Winlink Bulletins:
On a daily basis we received from the Winlink So Pacific Catalog Folder:
 French Polynesia Marine Wx in French

If we were underway we also received via email a buoyweather.com report for our area and a GRIB file for our area.  The large GRIB files are in the Winlink catalog, but we preferred the smaller ones  available via saildocs.com

We also downloaded via Winlink the weekly So Pacific Weather outlook from Bob McDavitt in New Zealand. 

On rare occasions we downloaded a WMO Bouy report.

To read the Nadi  Fiji Fleet code you need a WIAC decoder.  Most computer equipped cruisers have this program to share. 

The airmail forecasts for French Polynesia are in French and you can
click here for a French- English weather dictionary. 

Grib files may be decoded by Raytheon’s Raytech Navigator Program or the decoder in the airmail software while the WMO reports can be decoded by a program called Digital Atmosphere.  The Airmail program is free while  there is a charge for the others. 

GRIB- (graphics in binary) is a system to deliver a lot of information in a small file size so it lends itself well to airmail or sailmail. Using the Raytheon software you can overlay weather info directly on any electronic chart or a simple basemap. These files also are available in a 3 day forecast format that can be animated over the basemap. This allows you to see projected movement of fronts, isobars and wind shifts. The gribs are also available for areas not covered by the NOAA weatherfaxes. The gribs are on the airmail global wx files list. Sailmail or airmail users may also receive them via email by sending a specially coded email request to saildocs.com .

This is a site that you can email with a weather request for a certain lat/lon and get back via email a small file with wind speed/direction and swell information. You can get up to a 5 day forecast. It is possible to email a list of lat/lons where you are today and where you expect to be tomorrow, the next day, etc. out 5 days. Each day you would get moving projections for your route. The files are based on the GRIB data but have been converted to text only so they are very small- great for sailrmail users who cannot receive attachments.  The disadvantage is that if you only request a specific lat/lon you do not get the big picture of weather patterns as you would with a graphic. Each email costs 10 cents and you can prepay via credit card in blocks of 100, 200 etc. I plan to at least start across the Pacific with a $10 (100 message credit).
This is one of my favorite weather reports.

Webpages via email
saildocs.com by Jim Corenman, the creator of airmail and sailmail software and an effort called atolweb.com will send any specific webpage to boats at sea for no charge so if you have a favorite URL page, weather or otherwise you can get it by emailing them. info@saildocs.com or atolweb@sto-p.com

Quickskat -- These are graphics generated by NASA satellites that actually use a type of radar to read the wind and sea conditions of specific spots on the ocean from space. Like WMO buoys they are based upon actual conditions over open ocean so they are very valuable to us. The reports show a color for windspeed and a direction for wind arrows. Unfortunately when receiving them via winlink (even via telnet) I am unable to read the wind arrow directions. When I view them from the Internet site directly they are very nice.

Digital Atmosphere (WMO)- this is a sophisticated program that takes the input from WMO bouy reports and other weather reporting stations and generates full weather reports. You can choose to display as little as wind arrows or as much as wind, pressure, temperature, rainfall, etc. Buoy 51028 is placed at the equator near 154 degrees west. But there are few if any other So Pacific buoys. If there are no buoys near your locale I am not sure of the accuracy of the generated forecast. Near islands with reporting stations the reports are very impressive and based upon nearly real time data.


Winlink Instructions
Both the decoded programs and many of the files that do not need decoding will come to you as attachments on airmail files. If they are graphics they will come as tif, gif , jpeg or png files. You will need software that can display these formats. Most windows operating systems come with a Kodak image viewer or the files can be viewed with imaging or photo programs such as Adobe photoshop etc. If you click on the attachment icon in airmail and the file does not open automatically you can drag it to your desktop and click it there. If it says no program associated with this file type just browse the program list and tell it to open this file type with whatever graphics/image program. you use. Adobe will do almost any format. JVComm will do png. Kodak will do tifs and gifs. If it still won’t open then open your imaging program (i.e. adobe) then go to file open then browse to the desktop and click on it there.


With the advent of high speed Pactor III on Winlink if I want a single weatherfax I find it easier to get it via Winlink rather than receiving the weatherfaxes as they are broadcast by Honolulu, Australia or New Zealand.  If you want several faxes however Winlink becomes impractical and you are better off monitoring the broadcasts.

 n the Caribbean I found it easy  to receive all the faxes via broadcast.  However a search of the Pt Reyes schedule shows this is not as easy as it should be as the So Pacific forecasts are interspersed with North Pacific ones. You would have to tune in several times per day just to get one complete set of faxes. (Surface analysis, current and forecast wind/wave, and sat pix). The Hawaii schedule is more user friendly and the areas covered are large enough to include much of the Pacific cruising area. 

NOAA Wefax-- Despite the huge list of wefaxes available on airmail, when I viewed each one I found that most of them were for the northern hemisphere north of 20 degrees north.

I suggest anyone interested in wefaxes download the NOAA pdf file that gives all the worldwide fax schedules. It is available at:

Navtex- SITOR
The Pacific high seas text forecast is also available via navtex from Hawaii and Guam
Sitor is also available

For the complete schedules for Hawaii, Australia and New Zealand click here.

Voice Weather

Voice Wx Broadcasts are available from USCG in Pt Reyes CA and from Hawaii. Bob MacDiVitt (the “Herb” of NZ also does Pacific weather and the various nets also repeat weather information.  The Coconut Breakfast Net covers the area from Marquesas westward and was excellent in 2002 and 2003.  It is on at 1830 UTC on 12353 USB providing weather, position reporting and other info for cruisers.  Taupo Radio gives a mid pacific voice report on 12356 at 2103 UTC or 16531 at 2153 UTC.NOAA Voice Weather Broadcasts.

Hawaii at 0005Z, 0600Z, 1200Z, 1800Z
Freq: 6501 (ITU 601), 8764 (ITU 816), 13089 (ITU 1205)

Guam at 0330Z, 0930Z, 1530Z, 2130Z
Freq: 6501 (ITU 601), 13089 (ITU 1205)

Pt Reyes, CA 0430Z, 1030Z, 1630Z, 2230Z
Freq: 4426 (ITU 424), 8764 (ITU 816), 13089 (ITU 1205), 17314 (ITU 1625)


Maritime Mobile Service Net- runs about 20 hrs per day. This is a ham net but will take emergency calls from anyone. I think it is a better bet than the coast guard for an emergency call. Freq is 14300 or alternate 14313 USB.

Pacific Seafarers net checkins 0230Z- 0420Z same frequencies as above.

Coconut Breakfast Net- Marquesas and westward 1830 UTC on 121353 or 12356.

US Coast Guard telephone 800-246-7236
US Coast Guard Hawaii 415-669-2000


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Webmaster- Rob Dubin                            © copyright 2003-2006   Rob  Dubin               Page Last updated 09/02/2006