The 13 March 1993 Severe Squall Line over Western Cuba

Abstract

On 13 March 1993 a powerful prefontal squall line hit western and central Cuba. At 0000 UTC, a fast-developing extratropical cyclone with a well-defined cold front was located in the northeast Gulf of Mexico. Over the eastern Gulf of Mexico there was a 300-hPa jet streak interacting with a low-level jet. A hodograph typically associated with supercells or severe squall lines was observed at Key West, Florida. The air mass over the eastern Gulf of Mexico, Florida, and Cuba was conditionally unstable. Instability was enhanced by moist air at the surface interacting with a dry intrusion in the midtroposphere from the Mexican Plateau. Lifting induced by a strong short-wave trough favored the formation a compact squall line with embedded bow-echoes and line-echo wave patterns. Damaging winds were widespread with the squall line. Thus, the event fits the definition of a serial derecho. One of the two bow echoes that affected Cuba included a small but strong mesocyclone in its forward flank, as detected by radar and surface observations. The mesocyclone caused great damage in a 20-km-wide strip over the Havana and Havana City provinces, producing a family of downbursts in its southern portion. Estimated damage up to F2 on the Fujita scale was experienced in the effected area. Another bow echo struck the central region of Cuba producing similar damage. The squall line event described in this study is the most damaging one ever recorded in Cuba.