Moonlit Overshooting Tops in NPP VIIRS Day/Night Band

A strong cluster of thunderstorms developed over Central Michigan overnight on 3 July 2012.  These thunderstorms were captured by the Suomi NPP satellite overpass at 07:42 UTC by the Direct Broadcast antenna located at the University of Wisconsin-Madison Cooperative Institute for Meteorological Satellite Studies (CIMSS).  The data was processed and sent in real-time to the NWS office at Sullivan (MKX) where it was displayed in AWIPS.  The VIIRS Day/Night band provides forecasters with visible imagery at night at high spatial resolution (1km) from lunar illumination.  The first image below shows the features of the cloud tops, including overshooting tops as well as gravity waves.  Also visible are the lights emanating from the underlying cities including Detroit (large bright lights in the Southeast Corner).  The infrared 11 micron window brightness temperature image (second image) provides a thermal view of the same scene.  The coldest tops are -70C.      

Suomi NPP VIIRS Day/Night Band image of a strong thunderstorm over Central Michigan illuminated by moonlight with overshooting tops and gravity waves evident.  The Day/Night band supplies forecasters with a visible band capability at night when the moon is out.  The VIIRS data is acquired from the direct broadcast antenna at the University of Wisconsin-Madison CIMSS, processed via CSPP software and supplied to the NWS MKE office in real-time for display in AWIPS.  The image is from 3 July 2012, 07:42 UTC.

Suomi NPP VIIRS Window Channel Infrared image (11 micron) of a strong thunderstorm over Central Michigan.  The coldest cloud tops are -70 C, and the spatial resolution is about 1 km.  The VIIRS data is acquired from the direct broadcast antenna at the University of Wisconsin-Madison CIMSS, processed via CSPP software and supplied to the NWS MKE office in real-time for display in AWIPS.  The image is from 3 July 2012, 07:42 UTC.

Kathleen Strabala CIMSS, Steve Hentz MKX

GOES-R Fog/Low Cloud product over Lake Superior

The GOES-R Fog/Low Cloud product IFR Probability (that is, the probability of visibilities at or below 3 miles), below, shows a pocket of higher values near the coast of Lake Superior in northwest Ontario.  Visible imagery (bottom) confirms the presence of stratiform clouds in this region.  Southwest winds move relatively warm and moist air over the cooler lake surface (Lake SSTs are at or below 50), chilling the air to its dewpoint.   The GOES-R Fog/Low Cloud product fuses Rapid Refresh data and satellite data.

Scott Lindstrom, UW-CIMSS and Steve Hentz NWS-MKX

UW Cloud Top Cooling product and Lightning

The UW Cloud Top Cooling (CTC) product is used at NWS-Sullivan to anticipate (or corroborate) the development of deep moist convection and lightning.  Images above, of cloud-top cooling from Tuesday morning, 3 July 2012, show regions of cooling that occur just before (or concurrent with) the initial lightning strokes.  During the GOES-R era, when temporal resolution is increased, the ability of CTC to anticipate convective development should increase.

Scott Lindstrom, UW-CIMSS and Steve Hentz NWS-MKX

Ice Detection in Hudson Bay using VIIRS data from Suomi NPP

 VIIRS visible imagery (0.68 micrometers) (above) over Hudson Bay, 1801 UTC on 2 July.

VIIRS Snow/Ice Band (1.62 micrometers) (above) over Hudson Bay, 1801 UTC on 2 July

Channels on the VIIRS instrument on board Suomi NPP allow easy discrimination between ice and water clouds.  Ice is a very effective absorber of energy at 1.61 micrometers;  thus, if you compare visible imagery (top) with 1.61-micrometer imagery, regions that are very white in the visible (lots of reflection) and very dark at 1.61 micrometers (lots of absorption, not so much reflection) are assumed to be ice, either at the surface, or in clouds.  In the example above, ice is indicated over central Hudson Bay -- it is very white in the visible, and dark in the 1.61 micrometers.  Similarly, ice clouds are indicated over the southwest part of the image, where clouds are indicated as white in the visible, but not white at all in the 1.61 micrometers.  This is a handy method especially in winter to discriminate between surface snow and water-based clouds.

Scott Lindstrom, UW-CIMSS, Steve Hentz, NWS-MKX