Hurricanes and tropical storms cause a significant flooding problem where 25-30% of all deaths in these types of storms are caused by freshwater flooding. Where the heaviest rain falls depends on several factors.
Often people perceive the dangers are only confined to the coast but enhanced rainfall will often focus well inland or away from the center of a landfalling tropical cyclone because of the effects of physical geography or interaction with additional nearby weather systems.
Hurricane Matthew brought 6 to 7 inches of rain to Jacksonville with a few localized locations getting 8 inches in Ortega and Jacksonville Heights even as the center passed closed to our coast. The rain could of been much heavier if the storm slowed down. Certainly 7 inches of rain is high but it is within an average of 5 to 10 inches of rain for a storms moving between 6 and 30 knots.
The uplift from topography due to hills and mountains common along the mid Atlantic coast is the reason why Hurricane Matthew dumped much higher rain totaling over 20 inches over North Carolina far from the storm center.
Rain typically is heaviest east of the center track close to the eye but interaction with other weather systems can extend rain in front and west of the surface center.
Matthew did this as it moves inland and turns towards the north or northeast keeping the bulk of rain out over the Atlantic.
Another example is a rainfall bullseye near Tampa because storms often track west of Florida offshore in the Gulf without making landfall in the state. Their eastern outer bands can produce precipitation in the Tampa region.
Our biggest flood threat is when a storm core or eyewall passes over the First Coast. Only 10% of the heaviest rain is situated in a hurricanes eyewall yet it contains the location for greatest flood potential especially if it slows down.
Fun fact: it takes a raindrop 8 minutes to fall to the surface from the freezing level which is typically around 14,000 feet.
Copyright 2017 by WJXT News4Jax - All rights reserved.