Introduction:
Tropical Storm Fay was a storm that formed in the Atlantic basin August 15, 2008 and was down graded to a tropical depression on August 24, 2008. The storm made a record four landfalls on the United States, all in the state of Florida (Figure 3). The major impact of the storm was in Florida, Georgia, and Alabama from August 18 to August 26, dropping over 20” of rain in parts of Florida, and over 10” of rain in Georgia and Alabama. The storm also impacted other states with large amounts of rain in a short period of time. Florida, Georgia, and Alabama are the focus of this map animation of Tropical Storm Fay.

Daily precipitation reports of the storm were compiled from CoCoRaHS. These precipitation reports gave unprecedented coverage over the area and were very useful during and after the storm to compile the data for reports of Tropical Storm.

Methods:
The precipitation reports from each day were added to the accumulated total from the previous days. This means the second day of the storm, August 20, is the total from the first and second day’s reports. The third day’s accumulation, August 21, is from the total of the first, second and third day’s totals, and so on. The first day of the storm, August 19, is a one day precipitation total for the previous 24 hours. The normal report time for CoCoRaHS is 7:00 AM Local Time, covering the previous 24 hours. For the purpose of consistency in the maps, only precipitation reports between 5:00 AM and 9:00 AM Local time were used. Also, only stations that reported every day at the same time between August 19 and August 27 were used.

There were a total of 537 stations used for the report (Figure 1).

Figure 1: CoCoRaHS Stations used in Tropical Storm Fay Analysis

 

What we are seeing:
While looking at the animation, the approximate track of Tropical Storm Fay can be seen as the precipitation amounts accumulate each day (Figure 2). The animation also shows where the storm slowed and more rain fell. On August 21 the forward motion of Fay slowed almost to a stand still. This allowed large amounts of rain to accumulate on August 21 and 22 near Cape Canaveral and Brevard and Volusia Counties in Florida, which had the highest totals for the storm. Fay also had higher precipitation in the Florida Panhandle, mainly in Tallahassee, Florida, and southwestern Georgia. Even though the track of the “eye” of the storm did not take it into Georgia, the state still received a lot of precipitation from the outer rain bands of the storm. By the time Fay reached Alabama it was downgraded to a Tropical Depression; however, a lot of rain still fell in the state.

It is very interesting to see the areas that received a lot of rain versus the areas that did not. The Tampa Bay, Florida area and western Panhandle of Florida both had low amounts of accumulation compared to the other areas of the storm.

Roll over image for Animation

Figure 2: Animation of Tropical Storm Fay Accumulation maps.

Final Thoughts:
Tropical Storm Fay was not known for the damage caused from the wind and storm surge that accompanies most tropical storms and hurricanes, but rather the record amount of rain it dropped on parts of Florida, Georgia, and Alabama. The highest CoCoRaHS accumulation was 23.50” while a National Weather Service (NWS) Cooperative weather station reported 27.65”. The storm caused an estimated $560 million of damage in the three states between flooding and damage from wind and tornadoes generated by the storm.

There were benefits from Tropical Storm Fay as well. It pulled Florida out of a hydrological drought. The rains recharged Lake Okeechobee, raising the lakes level by 4’ in less than one week.

Figure 3: Tropical Storm Fay track from Weather Underground.

Acknowledgements:
A big thank you to the CoCoRaHS observers in Florida, Georgia, and Alabama for sticking through the storm to check your gauge and report the large amounts of rain to the CoCoRaHS website. We appreciate your reports.

Links:

National Hurricane Center Reports for 2008
http://www.nhc.noaa.gov/2008atlan.shtml

Florida CoCoRaHS State Coordinator Melissa Griffin’s, “Tropical Storm Fay Newsletter”
http://www.coaps.fsu.edu/climate_center/CoCoRaHS/TS%20Fay/TS_Fay.pdf