Sunday, May 5, 2013

Weather by Satellite Phone

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 satellite phone air time, 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 NWS 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 wx data requires a special software (grib viewer) and some caution in its interpretation. Grib viewers are discussed at the end of this article.

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 (wx) by satphone via email we need a satellite email service and we need data sources. To be practical, the email service must provide file compression, because of the high cost of Iridium air time. Satphone email services that provides compression and allows for attachments includes:

• Sailmail from  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 note on using Airmail with an Iridium satphone., the home of sailmail, remains a worldwide excellent source of grib and other weather data that can be viewed using any grib viewer.

• OcensMail (PC and Mac)

And there are at least two from the UK, but we are not sure of the pricing or services on these.

• Teleport-Mail from (PC). Listed as "Around 10 GBP per month."

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

• Skyfile Mail from, which is another global provider of air time (Astrium) that offers an email service option to their customers of air time. They also offer weather data from Météo France as well as Grib formatted forecasts at no charge to their air time 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. I am not familiar with the details. See note on winlink and Iridium phones.

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 Oens/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.

There may be more options, but those are the ones I know of.

Please refer to our earlier note A Few Nuts and Bolts of Satphone Usage, as those are the basics for any communications with the phones.

Satphone Weather Sources
Free sources of wx by email

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 air time is about the same for ten emails as is is for one.

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

The systems below all work well but the format must be followed rigorously (note spaces vs no spaces) and file names are case sensitive (xxx.txt is not the same as xxx.TXT). In the tables below the top line is a source for Help on the service. The Send email to line is the address you use to request a product. These could be saved in your address book. When the subjet line is not used, I tend to add in the subject line a short reminder of what I asked for. Next are two samples you can use to test the services.

Remember you must have an installed grib viewer to see the grib data. See note at the end of this article for grib viewer options. For Mac computers, you may have to chose the right app to read the attachments manually the first time.

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:

FTPmail from NWS
Help Online help page
Email product requests to:
Subject anything
Sample 1
cd fax
get marine5.txt
index to text forecasts for Atlantic coast
Sample 2
cd fax
get PWAE98.TIF
24-hr wind and wave forecast map for Atlantic coast

has all forms of weather data including a convenient grib request system. 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.

Saildocs Weather Service
Help Send blank email to get help files
Email product requests to:
Subject anything
Body send index
send nws-atl
send gribinfo
send ANZ450
You can ask for several products at once. Here we ask for a list of catalogs, list of Atlantic text codes, info on grib requests, and the actual txt forecast for Sandy Hook NJ
Body send gfs:8N,28N,77W,57W Get default-format grib file of wind and isobars for 3 days in the region shown. There are many options (see gribinfo file) for cusomizing this request. Also read the gribnews files for other model data and options.

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 2 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.

Mail A Sail
Help Send blank email to get help files
Email product requests to:
1. Subject PYEA11.SMALL.TIF File names go in the subject line
1. Boby Left blank
2. Subject grib gfs 8N:77W:28N:57W 12,24,36,48,60,72 GRD,PRMSL See their gib info file for specs. There are many options to specialize the request.
2. Body Left blank

Starpath Ship Reports
returns all ship reports, worldwide, within 300 nmi of your location over the past 6 hours.
Help An online help page
Email product requests to:
Subject left blank
Body 18.34N, 67.34W enter position in decimal degrees

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.  But is 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 our textbook Modern Marine Weather for safe guidelines to the use of this convenient product.

There is 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.

For reference, here is a summary of some related terminology.

"WinLink" is a network of individuals with radio transmitters who process and relay email and voice transmissions from Ham operators. The network is operated by volunteers. There is no charge to Ham operators to use it.

"Sailmail" is a similar network of individuals with radio transmitters who process and relay email and voice transmissions from mariners who need not be a Ham operator. To my knowledge the individual stations making up these two networks are completely independent. The Sailmail annual usage fee of $250/yr is intended to support the costs maintaining and supplying member stations.

"Airmail" is a software program for PCs (by Jim Corenman) that has two versions, one for use with WinLink and one for use with Sailmail, that resides in your computer and serves as the interface between an email program on your computer and the satphone or HF radio. When using a HF radio you also need a Pactor modem.

"Saildocs" is a communications service (operated by Jim Corenman) that provides weather and other documents such as world news, stock prices, or actually any file of graphic that appears on the Internet,  by satphone or HF radio. This service can be accessed by any email program, either wireless underway, or on land by the Internet. Its primary goal is to support Sailmail users, but it is free to others as well.

"ViewFax" is the free grib and graphic map viewer software program for PCs written by Jim Corenman for use with Saildocs products, but it will also view grib files received from other sources.

"Ocens Mail " refers to both the software program and the email service it accesses. It is a bundle package, neither part works without the other. The same is true of X-gate.

"WeatherNet" is a patented commercial service from that offers request and delivery of compressed weather products via satphone without the need of email.

Grib Viewers
This is a big topic, so just an outline here. A Grib Viewer is a software prgram or subroutine in an echart 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 echart 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. Later we will try to expand on this subject.


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.

Panoply. A very versatile tool used more often for the raw data from NOAA, so several extra steps are required. It is not often used by mariners underway, but a powerful piece of free software. Sort of a steep learning curve, however.

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

Zygrib is an excellent PC and Mac grib viewer.

... and several others, which we do not have recent experience with.


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, then come back to this one to appreciate what it offers. If you use Mac and PC, we recommend your 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 echart programming.

Expedition tactical ECS software from

For Mac there is a top of top of the line grib viewer with extensive data download options at  This is a $20, must-have app for Mac users.

... and several others, which we do not have recent experience with.

And one final note, 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

NOTE: the above was posted prior to latest update to RTOFS, based on the NRL's GOFS 3.1, so we are optimistic that these data will improve.

1 comment:

Anonymous said...

David .... thank you for this info. Although I'm reading it 2 years after post, it is still excellent information. My wife and I are getting ready to do the Caribbean Island hopping adventure (should take us 3-4 years) and accordingly are looking at various things of which weather underway is very important. Save journeys.