JACKSONVILLE, Fla. – This time of the year thunderstorms occur nearly every day in Jacksonville and northeast Florida, but certain weather factors can turn a typical storm into a destructive flash flood event.
Our subtropical climate between the Gulf and Atlantic is loaded with moist tropical air that can dump trillions of gallons of water over our city when systems like Irma bring the right weather conditions together.
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But our ordinary thunderstorms can quickly turn into flash flood killers so the Jacksonville National Weather Service put together a list of features to watch out for.
First, slower moving storms will always dump more rain.
Remember how Hurricane Harvey brought 60+ inches of rain northeast of Houston. Storms can run out of moisture ending quickly but not if a nearby source resupplies moisture. Warm ocean currents like the Florida and Loop Current offer this source of fuel.
Big surprises can show up by morning time because rain rates are also higher at night with tropical systems.
Secondly, cold fronts can focus rain adding a big boost.
Fronts typically stall out across the northern Gulf states concentrating rain while magnifying a storms potential through extra lift to the air.
Third, upper level lows trap storms.
Air swirling around these upper level atmospheric areas does not allow tropical moisture to move so it rain and rains in a state of gridlock.
Finally, unavoidable urbanization.
With city growth comes increasing runoff and flood issues from developments which reduce the ability of water to percolate into the ground.