Splitting Supercell

May 12, 2008


Referred by: Mark Thornton, Milli Bar; NOAA
Summary author: Mark Thornton

The base reflectivity Doppler radar images above document the splitting of a supercell thunderstorm into two separate storms in Coleman County, Texas on the evening of March 17, 2008. The image on the left shows the original storm at 7:22 p.m. (local time), while the image on the right, captured just twenty-two minutes later, shows the storm not long after the split. A majority of supercell thunderstorms travel to the right of the mean wind trough, a deep layer of the atmosphere. Splitting supercells are unique in that the dynamics that cause the split typically promote the development of both a traditional longer-lived right-moving storm and a rarer, more transient left-moving one. However, in environments characterized by strong unidirectional wind shear, the left-moving storm may persist, and even strengthen, long after the split. Such was the case on this evening. Approximately forty-five minutes after the split, the "right-mover" spawned a weak tornado near Silver Valley, Texas. Although no severe weather was attributed to the "left-mover," by the time of the Silver Valley tornado, it was nearly 30 km (about 19 miles) to the northwest.