FIP Overview
The Forecast Icing Potential (FIP) is an automatically-generated
forecast of icing potential. FIP examines numerical weather prediction
model output (from the Rapid Update Cycle, RUC) to calculate the
potential for in-flight aircraft icing conditions. This icing potential
demonstrates the confidence that an atmospheric location, represented
by a three-dimensional model grid box, will contain supercooled liquid
water that is likely to form ice on an aircraft.
NOTE: By FAA policy, FIP is classified as a restricted supplementary
weather product, authorized for use by meteorologists and dispatchers
only.
NOTE: While CIP is a calibrated probability, FIP remains an uncalibrated
icing potential. FIP will be calibrated to probability in a future
version.
The algorithm analyzes the model output from a vertical column, determines
the cloud top and base heights, checks for embedded cloud layers, and
identifies a precipitation type. Once the likely locations of clouds and
precipitation are found, the physical icing situation is determined,
and a fuzzy logic method is used to estimate the icing potential. The
fuzzy logic interest maps are based on clues from the model output,
reflecting relevance to the presence of icing. Numerous fields from the
model are used to determine the icing potential at each model grid box
horizontally and vertically.
The FIP is issued every hour and generates hourly forecast for 3 hours
into the future. For example, forecasts issued at 1300Z would be valid
for 1400Z, 1500Z and 1600Z. Six-, 9-, and 12-hour forecasts are issued
every three hours beginning at 00Z. For example, a forecast suite issued
at 0300Z would have valid times at 0900Z, 1200Z and 1500Z respectively.
On the FIP graphics, the scale is from 0 to 85%,
using cool to warm colors with warmer colors indicating higher icing
likelihood. Potential ranges from 0% (no icing expected) to 85%
(icing likely). SLD icing potential charts display in the same manner,
with the addition of grey areas to depict areas of unknown potential.
Like the CIP graphics, FIP graphics are also available for alternating
altitudes or as a chart displaying composite maximum potential.
NOTE: The scale is not calibrated as a true probability value. It does,
however, have value in pointing out differences in the likelihood of
encountering icing at a given location. For example, a value of 70 does
not indicate there is a 70 percent chance of encountering icing. However,
when comparing it to other higher or lower values will indicate if there
is a greater or lesser likelihood of encountering icing. No information
is provided as to the severity of icing and none should be inferred.
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