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What's wrong with FIS-B weather?

Updated: Jul 19, 2019

A lot. Is it better than having nothing? Yes, and no. But you need to drill down to the product level to see the value or lack thereof.


In August 2018 the FAA began to broadcast six new weather products to include lightning, cloud top height, icing, turbulence, center weather advisories (CWA) and graphical AIRMETs (G-AIRMETs). This was fantastic news to many pilots. So where's the downside to FIS-B weather? Let's look at some of these newly broadcast products and discuss these limitations. Note, these are presented in no particular order and by no means are a complete list of the cons.


G-AIRMETs


Graphical AIRMETs or G-AIRMETs are issued by aviation meteorologists at the Aviation Weather Center (AWC) in Kansas City, Missouri. The legacy textual AIRMET Zulu encapsulated both a forecast for icing as well as a forecast for the freezing level. Now the freezing level is captured in its own G-AIRMET.


The freezing level G-AIRMET has a poor spatial resolution. That's not the fault of the FIS-B broadcast, it's just the nature of the freezing level G-AIRMET. At a 4,000-foot resolution, it's hardly useful when there isn't a big change in the freezing level over a wide region as depicted in the G-AIRMET shown below. The freezing level contours of 12,000 feet to 16,000 feet MSL span the entire north to south distance along the west coast of the U.S. So what's the freezing level in northwestern Nevada? In mountainous regions, a freezing level difference of 2,000 feet can mean the difference between a safe passage or one fraught with icing concerns. For comparison, the SiriusXM broadcast, the data has a resolution down to 100 feet.

Freezing level G-AIRMET produced by forecasters at the AWC