The Weather Fax - SailNet Community
 
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The Weather Fax

Red sky at night a sailor's delight. This simple rhyme was probably the first weather forecasting tool you used. And it's a good one too, as red skies indicate dry air to the west and fair weather is on the way. But before you venture offshore, access to additional up-to-date weather information is imperative. For comprehensive, current and reliable information offshore, marine weather facsimile transmissions are the standard.

Weather fax transmissions are similar to the fax transmissions you receive via the telephone at home or work. The sender's fax machine scans a document and processes it into line after line of different colored dots-black, white and gray. The fax machine then translates the dots into tones, where a tone's pitch corresponds to the color of the dot. If you have ever listened to a fax transmission, you probably heard the warbling, high- and low-pitched tones. These tones are sent over the phone lines as each line is scanned. As your fax decoder receives the tones, it translates them back into dots and subsequently, characters on a sheet of paper and like magic you see what he sender placed into his fax machine.

Instead of using phone lines, a weather station's fax broadcasts over marine SSB frequencies. A demodulator cable allows sailors to connect a PC's serial port to the audio output of the SSB receiver to collect and decode the broadcast information automatically. By using a specialized software program, the broadcast weather fax information can be displayed on the computer screen and printed out or saved to the hard drive for reference.

The weather fax information broadcast typically consists of up to a dozen different kinds of synoptic weather charts that show the meteorological conditions over a given area. Approximately 70 stations around the world broadcast charts for their surroundings so with few exceptions, it is possible to get weather charts worldwide.

The interpretation of these charts is left to you so an understanding of marine weather is necessary to fully understand them. I would suggest that you take the weather course offered by the U.S. Power Squadron in your area first and to also read the weather chapter in Bowditch and the Mariner's Guide to Radiofacsimile Weather Charts by Dr. Joseph M. Bishop. The Weather Trainer by Starpath is an excellent tool for understanding and interpreting weather charts. This is a revolutionary, easy-to-use interactive program that you can use on your computer to learn weather forecasting.

There are several weather fax software programs available to you for about $180. Weather Fax for Windows and PC HF FAX version 8.0 for Windows. Both programs include a demodulator, software and instructional manual. The PC HF FAX program also includes an instructional tape and the program can also receive FEC, NAVTEX, Morse and SITOR.

For a complete listing of all HF weather fax frequencies and broadcast times check out: ourworld.compuserve.com/homepages/HFFAX

You also may want to visit this site when you are surfing the web to see the GOES East IR - North and South America Satellite Weather Map in real time. weather.unisys.com/satellite/sat_ir_east.html

NOAA has interactive marine observation reports in real time at: www.nws.fsu.edu/buoy where you can click on a buoy or CMAN station to get the current conditions for your area.

EDITOR'S NOTE: Also check the Useful Weather Web Sites article from SailNet Weather Advisor Bob Rice.

Jim Sexton is offline  
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