Day/Night Band Provides Better Detail of Low Clouds

During the overnight hours of 23-24 November, 2012, persistent stratus and flurries lingered over much of Wisconsin in the wake of a strong cold front which had swept through the previous day.  As indicated by the below Green Bay 00z sounding, the stratus was shallow and only several hundred feet thick.  Cloud bases were 2 to 3 thousand feet. 




















The short-term forecast concern was timing of the cloud erosion.  The below CONUS wide view 11-3.9 micron imagery from 08z 24 Nov indicated widespread clouds blanketing most of Wisconsin and the western Great Lakes. 


0758z 24 NOV 2012 11-3.9 micron imagery

   At about the same time, the below NPP VIIRS Day/Night band CONUS view indicated thin spots and breaks in the cloud cover across Wisconsin and the western Great Lakes. 


0758z 24 Nov 2012 Day/Night Band

Taking a closer view of the 11-3.9 micon imagery below, the clouds appear to shroud all of Wisconsin except for the far northwest corner. 



11-3.9 micron imagery - closeup

But a closer view of the Day/Night band showed more breaks in the cloud cover across Wisconsin as well as thin spots.  The clearing over northern Lake Michigan and Door County was much more discernable using the D/N band. 

Also, the illumination (reflectance) from the metropolitan areas highlighted the thinness of the clouds as well as helped make the breaks more discernable. 

Day/Night Band Closeup

By using the Day/Night band, a clearer picture of the cloud cover covering Wisconsin was determined.  This better understanding would allow the short-term forecaster to make a more reliable forecast of clouds and timing of low cloud erosion. 

The moon was in waxing gibbous and was 85.3% lit on 24 Nov 2012.  

Marc Kavinsky
National Weather Service - Milwaukee/Sullivan