Waiting for cirrus to dissipate

Considerable overnight and ongoing convection over the upper midwest on August 2nd has left a large cirrus shield over Wisconsin. The UW Convective Initiation (UWCI) product does not detect convective development in regions where significant ice clouds already exist. The 'ice mask' -- where UWCI cannot be computed, can be displayed in AWIPS, and it shows the extent of the ice cloudiness over Wisconsin. A small gap has developed over the extreme southwest part of the state. If this region expands with time, then UWCI might be able to detect incipient convection over the upper midwest later this afternoon.






A MODIS Cirrus Channel image (1.38 micrometers) from 1710 UTC on 2 August shows that cirrus persists over the upper midwest.














Submitted by Scott Lindstrom (UW CIMSS) and Denny VanCleve (NWS-MKX)

Using NearCast vertical theta-e differences on a Warm Humid morning

Note the outflow boundary that is moving southward (in the 1512 UTC radar composite to the left) into the MKX WFO, arcing from northern Sauk County (south of the Dells) through central Columbia County. (The convection that has spawned this outflow is in the northern strip of counties of the WFO to the west of Fond du Lac) What are the chances that convection will fire along this outflow boundary? Are there products that could help you decide if the convection will continue, or will redevelop as the outflow boundary moves south?






The NearCast forecast of Theta-e differences valid at 1530 UTC shows a region of stronger stability over the MKX WFO -- suggesting that any convection that moves into southeast Wisconsin will struggle to develop. Convection might pop -- and it did over northeast Dane County at 1627 UTC (see below) -- but that convection was short-lived.










NearCast output suggests the convection over Dane County will not persist. The highest tops were to 20-25000 feet, and no lightning occurred. (Radar image at left from 1627 UTC)
















Posted by: Scott Lindstrom (CIMSS) and Denny VanCleve (MKX)