Can you use gridded NUCAPS fields to diagnose the rain/snow line?

February 13th, 2020 |

900-mb Temperature fields (color-shaded; the 0ºC line is in black) derived from NOAA-20 NUCAPS profiles, 0624 UTC on 13 February, along with 0600 UTC METAR observations (Click to enlarge)

Gridded NUCAPS fields include a wide range of thermodynamic variables. The plot above shows the 900-mb temperature field. Is it possible to use this data to diagnose a rain/snow transition line?

Over southern New England, the relationship between 900-mb temperatures and surface precipitation observations seems robust: snow is restricted to most (but not all!) places where 900-mb temperatures are cooler than 0ºC. and rain falls where temperatures exceed 0ºC. Where terrain might be an influence in trapping cold air near the surface — the Catskills, for example, or the Alleghenies over New York and Pennsylvania, the relationship is not so straightforward. This data source warrants future investigations on its utility in these situations.

Leave a Reply