The Apalachee Bay Effect: Impacts on Severe Weather in the Florida Big Bend (321)

Andrew Lahr, National Weather Service, Tallahassee, FL



Apalachee Bay, which is located in the northeastern Gulf of Mexico just south of the Florida Big Bend region, has relatively cool water surface temperatures during the winter and spring months compared to the remainder of the Gulf. As a result, sea surface temperatures that can drop into the 50s Fahrenheit (10-15 degrees Celsius) are often significantly cooler than the overrunning air mass when southerly flow crosses Apalachee Bay and moves across the Florida Big Bend. February and March are climatologically the most active months for severe weather outbreaks across the County Warning Area (CWA) covered by the Tallahassee National Weather Service Forecast Office. With a primary ingredient for severe weather being the warm, unstable southerly flow ahead of an approaching system, the cool surface temperatures of Apalachee Bay could lessen available instability by creating a shallow stable layer that is advected inland into the Florida Big Bend region. This study analyzes the climatology of severe weather across different regions in the Tallahassee CWA, and examines which types of severe weather (tornadoes, hail, and/or damaging wind) could be affected by the relatively stable layer advected inland from Apalachee Bay. Results show a local minimum of tornadoes with F2/EF-2 or greater strength in the Florida Big Bend region, while spatial distributions of damaging straight line winds and large hail in the Florida Big Bend are not significantly different from other regions in our CWA.