Weather Facts


How to obtain weather information by satellite phone  (published July 2013)

As satellite phones become commonplace for today’s blue water sailors, the question is, what services are available and how do you choose between them to get the best information for you and your crew?

Weather data are available underway by satphone from commercial weather services or by conventional email request and delivery. These same data are available by HF (SSB) radio, or by Internet links on land, which is the best way to practice, because it saves the satphone airtime, which is typically the largest cost in the process.
The types of data include:

(1) text reports and forecasts.
(2) graphic analysis and prognosis maps from the National Weather Service (NWS), Ocean Prediction Center (OPC) and other agencies.
(3) numerical weather model forecast maps in GRIB format. These are available from several models, but the most common are GFS wind and isobars and the WW3 sea state and wind data, which in principle accounts for sea state and currents, but does not include isobars. This very popular form of weather data requires a special GRIB viewer and some caution in its interpretation. See below for more on GRIB viewers.

In the methods we cover now, these products are requested and delivered by email messages and attachments. I am not covering the several excellent sources that are available by Internet alone, such as,,,, and for viewing grib forecasts online. And we are not covering the several excellent dedicated commercial weather providers such as WeatherNet ( or ClearPoint(––both have extensive discussions online showing the value added to their commercial weather product delivery programs. Similar presentations are available at the websites of their European counterparts, such as NaviMail (, Theyr ( and WetterWelt (

To get weather by satphone via email you need a satellite email service and you need data sources. To be practical, the email service must provide file compression, because of the high cost of Iridium airtime. Satphone email services that provide compression and allow for attachments include:

Sailmail from $250/yr membership fee. Sailmail is a cooperative association that provides email service via HF radio. If you already use that service from them you can apply it to the satphone and Internet at no extra charge. Access to the Sailmail service is through the PC program called Airmail. See
OcensMail (PC and Mac) $59 set up + $20 to $26/month depending on contract period.

Xgate from (PC and Mac) $59 set up + $20 to $26/month depending on contract period.

Note: OcensMail and Xgate are the same program offered by two independent companies at the same price. The programs work with all forms of wireless communications, not just satphone. The companies share several products, but otherwise have different arrays of products related to satellite voice and data communications. Starpath School of Navigation works with both of them on a regular basis.

Teleport-Mail from (PC). Listed as “Around 10 GBP per month,” which would be about $17/mo.

OnSatMail from, based in the UK offer email services to their air time customers at an additional fee.

Skyfile Mail from, which is another global provider of airtime (Astrium) that offers an email service option to their customers of airtime. They also offer weather data from Météo France as well as GRIB formatted forecasts at no charge to their airtime customers.

WinLink from Ham operators can use a special version of Airmail ( to access the WinLink server for free email over the satphone (and HF radio, which it was originally designed for). This is similar to using Airmail connected to the Sailmail Network server. WinLink users can access the Saildocs for weather products. It would be best to check with your Ham operator friends who use this service for their review and suggestions. See

On this option, however, it is very important to point out that free Ham email via WinLink cannot be used for any business related emails. This means you cannot discuss your personal business or occupation or financial matters, nor can you even ask for tech support for any equipment on the boat or search for places to buy parts for the boat. This is a strong limitation when considering a general email service underway. There is also anecdotal evidence that connections and services are not as dependable and convenient as they are with the paid services from Sailmail or the Ocens/X-gate programs, but I do not have direct experience with that. Needless to say, there are many benefits to being a Ham operator underway, as there are many networks available for cruising information and it is a way to keep in touch with other mariners (especially by HF radio) without extra service fees.

You can access and receive products from any of the sources below. You can test and study each one of these using a direct Internet connection without the added expense of satphone airtime, which is clearly a good idea. Below are samples on how to get started.

The systems below all work well but the format must be followed rigorously. Note: spaces vs. no spaces, file names are case sensitive and xxx.txt is not the same as xxx.TXT.

Remember, you must have an installed GRIB viewer to see the GRIB data. For Mac computers, you may have to choose the right app to read the attachments manually the first time.

For all of these services send only plain text messages as described, without any signatures. It is best to send the requesting email as part of a larger batch of emails to save connection times. The airtime is about the same for ten emails as it is for one.

FTPmail from NWS offers essentially all text and graphic weather maps from the NWS, but no GRIB formatted model forecasts. Also, the graphic weather maps are not compressed, so these must be selected with care for delivery by satphone. See:

Saildocs has all forms of weather data including a convenient GRIB request system. It can be used for wx data even if not using Sailmail for your email server. Get started by sending a blank email to Then you get instructions for the rest of the program. You can also ask for text forecasts by the NWS region codes, described on the Marine Weather Services Charts, ie Sandy Hook, NJ is ANZ450.

Mailasail offers text, graphic and GRIB files worldwide for many products. Start by sending a blank email to, and follow instructions for getting three more product-specific help files. They offer compressed graphic maps by a factor of two, which is very helpful. They do not have as many products as Sailmail or FTPmail, but they advertise that they will add specific products on request. Note: they use the subject line, not the body, for the request.

Global Marine Networks offers WW3 model wind predictions in GRIB format by email request. They use the subject line, not the body, for the request.
Starpath Ship Reports returns all ship reports, worldwide, within 300 nm of your location over the past 6 hours.

Starpath ASCAT Winds returns a graphic image of the winds from the latest pass over the submitted position. These files are about 35 KB, so study the help page to learn when new data is available and if it might be useful to you. A good place to see them at work is

One of the values of the email requests for any type of coastal weather on your approach to land is you can get the local coastal reports and forecasts long before you are within VHF range, which might help planning your approach.

There are issues of timing to workout when viewing model forecasts in GRIB format that extend over several forecast periods. In principle, the first one of a series should be the one corresponding to the latest run of the model, and that map is to a large extent a good representation of the surface analysis at the valid time of the map. Each sequential map will be forecasts for the indicated time interval after that one. Check that the map time labels agree with that system. It is always good practice to compare these model predictions with the corresponding man-made surface analysis and prognosis maps available at the Ocean Prediction Center (

There are also known circumstances where the GFS model is not dependable.

Please refer to the textbook Modern Marine Weather, for safe guidelines to the use of this convenient product.

There is a tremendous amount of data available and you will see there are many options for getting it. You have to compare the options for your specific needs and then practice. Once you have the choices made and working, the reception of email weather becomes very automated and easy. Many of the services above offer a “subscription” format for the request, so that the same map or product is sent to you automatically each day, updated to latest values.

It is also valuable to compare these methods with the enhanced convenience and efficiency offered by the commercial services such as WeatherNet, ClearPoint, and others. Each has a demo program for evaluation.

This is a big topic, so this is just an outline. A GRIB Viewer is a software program or subroutine in an e-chart program that will display GRIB files. Most standard GRIB files can be viewed on any GRIB viewer, although this is not universally true. There are free stand-alone viewers and commercial viewers and there are many e-chart programs that will show GRIB wx data right on the navigational charts in use.

Again, some are free or open source products, others are commercial products. Here is a list of products with just a few short notes. Look for a later article to expand on this subject.

Free viewers
ViewFax 5.0.056. Viewfax has direct internet/satphone access for GRIB’s, images and text bulletins via Saildocs. These are compressed files, and are suitable for receiving directly via satphone without further compression.

UGrib. This is made for showing GRIB files downloaded from their web site, but it will also show files nicely from other sources.

Panoply. A very versatile tool used more often for the raw data from NOAA, so several extra steps are required. Mariners do not use it underway often, but it is a powerful piece of free software.

OpenCPN. Is an excellent open source ECS program with an add on for overlaying GRIB weather maps.

Commercial products
Ocens Grib Explorer. This product cost $199, but it is certainly one of the nicest GRIB viewers for mariners. There is a PC and a Mac version. The PC version has a few more options than the Mac version. Both have timed full feature demo versions, but if starting from scratch it would be best to practice with the free ones above, and then come back to this one to appreciate what it offers. If you use Mac and PC, we recommend you try both to see which is best for you.

Time Zero ECS software from Furuno (MaxSea) or from Nobeltec (Odyssey) each have an excellent GRIB viewer incorporated into the e-chart programming.
Expedition tactical ECS software from

We can also get ocean currents in grib format, but we are still struggling to find a model that will have actual practical value to our navigation. When we do, there will be an announcement at

David Burch is the director of Starpath School of Navigation, which offers online courses in marine navigation and weather at He has written eight books on navigation and received the Institute of Navigation’s Superior Achievement Award for outstanding performance as a practicing navigator.