Making Sense of Snowfall Accumulations in NCEP Models
(322)
Geoffrey Manikin, NASA
SPoRT / University of Alabama in Huntsville, College Park, MD
Logan Dawson, NOAA/NWS/NCEP/EMC
and I.M. Systems Group
Tracey Dorian, NOAA/NCEP/NWS/EMC
and I.M. Systems Group
Abstract:
Converting model QPF to
actual forecasts of amounts of snow remains a major challenge for forecasters.
Attempts have been made to apply snow-to-liquid ratios (SLRs) that are more
reasonable and representative than the standard 10:1, but simply determining
what amount of model QPF is snow is extremely difficult right at the start.
This presentation attempts to help understand how model snow water equivalent
is derived and help forecasters understand major discrepancies that often exist
between model &ldquosnow accumulations&rdquo and precipitation type. A
quick overview of precipitation type computations in the NCEP models will be
given. Alternatives to examining snow accumulation maps will also be discussed,
including using changes in accumulated snow depth, explicit parameters from
sophisticated model microphysics, and alternate SLRs. Applications of these
snow accumulation and precipitation type tools to winter storm cases
highlighted by EMC's Model Evaluation Group (MEG) will be featured.
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