The Aviation Digital Data Service’s Web site has been called the go-to Web site for one-stop aviation
weather shopping. The variety of products covers all the bases, and the site’s cutting-edge products (such as the current and forecast icing products) make for a wealth of first-class preflight planning aids. Under the “flight folder” link at the left of the ADDS homepage you can even call up Canadian and other foreign weather information.
Come October 2009 yet another new product, the Graphical Airmet (G-AIRMET) is set to be commissioned as a primary operational source of airmet information. For now, it remains an experimental tool, and is not for operational use.
The G-Airmet page is online. Alternatively, go to the ADDS homepage, click on the “Air/Sigmet” tab, and then look for the “Graphical Airmet” link at the top of the page. The site is simple to navigate, and includes a “play” button that lets you animate any of the eight airmet advisory categories in a loop that covers a 12-hour time frame. You can view a single airmet, or click on more than one to create an overlay. G-Airmets will be issued every six hours, and make forecasts in three-hour intervals for the 12 hours following the issue time. When it’s made operational, G-Airmets will augment the text and graphic airmets you have known and used for years.
The motivating ideas behind the G-Airmet initiative are simple. The original, all-text airmets use high-altitude VOR locations to mark the boundaries of potentially hazardous conditions. If you are a true aviation savant you’ll be able to decipher all those three-letter code combinations. But most of us are not so blessed. So although VOR-defined text airmets may be helpful, their areas can be difficult to visualize.
Enter the graphic airmet plots that are currently operational. These charts are the visual equivalent of the text airmet. Can’t quickly figure out what “FROM 70SSE BOY TO 70SE DDY TO TBE TO 50WSW ALS TO 70SSE BOY” means? No problem. Just look at the airmet graphic (and its links) that dominate today’s ADDS airmet page. Those boundaries are drawn for you, and the airmet can be printed out for use in the cockpit.
Having a single airmet graphic is nice, but the Aviation Weather Center wanted to provide a staggered look at an airmet’s trend. The airmets now plotted come out at six-hour intervals—just like the text airmets—and can cover the upcoming six hours, along with a six- to 12-hour outlook period.
The problem with plotting 12 to 18 hours’ worth of airmet weather on a single chart is that the data is “smeared.” The box containing the airmet includes the most recent advisories as well as those up to 12 hours in the future. In some cases, today’s graphically depicted airmets can encompass an area the size of the entire eastern half of the contiguous United States. This can be misleading, as rotten weather may begin farther west, then travel east during an airmet’s valid time. But you’d have no way to know that—other than to check the text airmets.
G-Airmets take care of this problem by giving a snapshot of airmet coverage every three hours. The G-Airmet’s valid time is posted with its graphic, and the subsequent three-hour forecast intervals can be accessed by clicking on the five posted time-interval buttons at the top right of the chart.
Right now, there’s a safety- and risk-analysis process going on between the AWC and the FAA. The goal is to review the G-Airmet, and identify any high- or low-risk aspects. You can help in this process by providing your feedback. Just click on the “G-AIRMET Feedback” link at the bottom right of the G-AIRMET page. As for me, I can’t see any down sides to this great new product.
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