Rapid Refresh (RAP) and High-Resolution Rapid Refresh (HRRR) Forum

cold air damming

Posted By: Bill Bua
Date: 30-January-04 2037Z

Gary -- The EDAS did indeed stop using surface temperatures recently because such use had an adverse effect aloft. There was difficulty in determining the vertical extent of temperature errors resulting from strong surface-based inversions, for example, which was making the 850-hPa temperature too low in the Eta analysis. It has been noticed that there have been problems with shallow cold air masses this winter, which have been attributed to this analysis change. Until there is a way to assimilate surface temperatures with a variable radius of influence in the vertical depending on stability, however, I don't think you'll see surface temperatures assimilated. Something to keep an eye on for the next storm early next week, I suspect, especially in the central/northern Mid-Atlantic! Bill

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