Page 19 - Volume 15 Number 1

The 12-hour maximum icing potential field (top) shows a marked decrease in values after the product becomes a calibrated icing probability field (bottom). With the potential field there are lots of areas with values exceeding 75 (shown in red). However, the calibrated probability field valid at the same time and with the same 12-hour forecast length doesn’t exceed 45 percent. This demonstrates the uncertainty that is now factored in with increasing forecast length.
good weather model that goes out that far and we’ll run FIP on it.”
It is one thing to produce an icing forecast with any reasonable accuracy out to 12 hours in the future, but 60 hours is certainly a stretch at the moment.
In July 2011, FIP is slated to be flipped over to use the Weather Research and Forecast – Rapid Refresh (WRF- RR) model. This will potentially allow FIP to be extended to 18 hours. Of course, that won’t happen immediately since icing forecasts beyond 12 hours have never been verified. However, the most significant improvement is that the WRF-RR has a•much larger forecast domain than the RUC. As a result, it’ll provide icing forecasts for all of North America. T&T
Scott Dennstaedt is a CFI and former NWS me- teorologist based in Fort Mill, S.C. To learn more about aviation weather, visit his Web site at http://avwxworkshops.com.
At 12 hours out, the forecast’s uncertainty is reflected in a lower probability, which doesn’t mean ice won’t be there.
JANUARY 2011
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