The storms that ravaged the southern United States this past week not only produced deadly severe weather, but also incredible flooding. Figure 1 shows parts of the Florida Panhandle and southern Alabama received in excess of 10 inches of rain on Tuesday, April 29 alone!
A previous blog post introduced the Overshooting Top Detection product and explained its utility in severe weather situations. Overshooting tops are also indicators of where heavy rainfall may be occurring. Furthermore, the constant presence of overshooting tops over a particular location over an extended period of time may indicate a prolonged period of heavy rainfall, which could lead to flooding.
The animation in Figure 2 shows GOES-East IR imagery with overshooting top detection’s overlaid from the afternoon of the April 29 into the early morning hours of the April 30. During much of this period, GOES-East was in Rapid Scan Mode, meaning images were often available every 5-10 minutes (instead of 15). Notice the persistence of overshooting tops centered over the Mobile area throughout the period, where copious amounts of rainfall were recorded. By about 09Z, a downward trend in overshooting top detection’s had begun as the storm system shifted eastward and weakened. The Overshooting Top Detection product provides a day/night capability for forecasters to easily identify where within a convective system the strongest updrafts are occurring, and where severe weather and/or heavy rainfall may be occurring given other meteorological factors.
Figure 3 shows this same system during the early morning hours of April 30 at much higher resolution. This is a 375 m IR image taken with the Suomi NPP VIIRS instrument. Notice the visibility of features that aren’t easily seen in current GOES IR imagery such as gravity waves and overshooting tops.
– Bill Line, SPC/HWT GOES-R Satellite Liaison