MM5 Snow Cover Initialization, April 2002

In early April 2002, we noticed some extremely cold temperature forecasts for Seattle and for Medford. Here is the time series for Seattle from the 12-km domain:
Upon inspection, we noticed that the USAF snow cover data was completely bogus.

We compared to an earlier USAF snow cover plot and to the ETA 221 snow cover as derived from water-equivalent snow depth. As you can see below, the ETA 221 was superior and it led to much more reasonable temperature forecasts:.
Data SourceSnow Cover Plot
USAF Really Bad Snow Cover
USAF Previous day's Bad Snow Cover
ETA 221 Superior Snow Cover

For further comparisons, you may scan this directory, or look at this loop of 93 images comparing USAF and ETA 221 snow fields from Jan 24th through Feb 23 2002. In those images, the MM5 takes values of 10 or higher as snow cover. To compare sea-level pressure temperature and wind forecasts, you may scan the 0Z April 1 directory, the 12Z April 1 directory, or look at this 00Z April 1 loop, or the 12Z April 1 loop comparing forecasts using USAF and ETA 221 snow fields.

As of the 0Z 1 April 2002 forecast, we are initializing the MM5 with the ETA 221 water-equivalent snow depth.