Heavy rainfall and flash flooding in Maryland

July 30th, 2016 |

GOES-13 0.63 µm Visible (top) and 10.7 µm Infrared Window (bottom) images [click to play animation]

GOES-13 0.63 µm Visible (top) and 10.7 µm Infrared Window (bottom) images [click to play animation]

A 2-panel comparison of GOES-13 (GOES-East) Visible (0.63 µm) and Infrared Window (10.7 µm) images (above) showed a band of thunderstorms oriented southwest-to-northeast across northern Virginia and northern Maryland late in the day on 30 July 2016. Cells within this band produced very heavy rainfall and extreme flash flooding at Ellicott City, Maryland — located northwest of Baltimore/Washington International Airport KBWI, and marked with a cyan * symbol — with a total of 6.60 inches of rain in just over 2 hours (NWS Baltimore/Washington Public Information Statement | Event summary). The coldest cloud-top IR brightness temperature was -67º C at 0045 UTC on 31 July (8:45 pm local time).

The MIMIC Total Precipitable Water product at 3-hour intervals (below) indicated the presence of TPW values in the 2.0 to 2.5 inch range over parts of the region.

MIMIC Total Precipitable Water product [click to enlarge]

MIMIC Total Precipitable Water product [click to enlarge]

Upstream rawinsonde data profiles from Washington Dulles International Airport in northern Virginia (below) showed TPW values of 46.8 mm or 1.83 inches at 12 UTC on 30 July, and 49.2 mm or 1.94 inches at 00 UTC on 31 July (although the later data looks suspect, given the balloon was launched as strong thunderstorms were approaching).

Washington Dulles VA rawinsonde profiles [click to enlarge]

Washington Dulles VA rawinsonde profiles [click to enlarge]