Busy CI day in Northeastern U.S.

On 18 May 2011, CI was occurred in many locations in Virginia, West Virginia, far northern North Carolina, and southern Pennsylvania. Shown is the SATCAST CI nowcast at 1730 UTC, with radar images between 1730 and 1817 UTC. Annotated on the SATCAST image are the "CI locations" labeled (a)-(k). On the radar time series, the same regions are highlighted. In the lower right image of the radar sequence, on the 1817 UTC image, are the locations (circled or with an arrow pointing to where the CI event occurred), and the approximate lead times (in minutes) that SATCAST provided. These are subjectively determined. Events where no CI event was observed (a follow-on echo of 35 dBZ intensity) are labeled as "F" for "false alarm."

This event/time period shows how SATCAST performs in a situation in which CI was widespread. It remains challenging for a forecaster to identify exactly where a CI event forms related to a given CI nowcast despite the high number of SATCAST CI nowcasts. In this case, the flow was southerly and hence all CI events occurred to the north (or north-northwest) of a nowcast location. These storms were generally low-topped (25,000-30,000 ft), directly associated with a closed upper low circulation.