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 Accumulation |
As a powerful and dangerous Category 4 hurricane, Hurricane Charley came ashore packing sustained winds of 145 mph. The combination of heavy rain, wind, and a 10- to 15-foot storm surge caused widespread damage and 23 deaths. Recent estimates put the total property damage from Charley at $7.5 billion.
OneRain, Inc. analyzed the rainfall created from Hurricane Charley as it crossed the Florida peninsula, encompassing 27 hours from the morning of August 13 to the morning of August 14. We began with 15-minute estimates of rainfall, then adjusted these estimates with data from over 300 rain gages provided by four water management districts in Florida. The adjustment technique is spatially-dependent, wherein rainfall estimates at radar pixels are modified according to data from nearby rain gages. Special care was taken to disregard data from gages at or near the eye of the hurricane, as rain gages can perform erratically when subjected to high winds. The end result is a dataset of rainfall estimates covering the state of Florida, at 15-minute time intervals, throughout the 27-hour period when Charley affected the state.
 Captiva Island Before and After source: USGS |
The total 27-hour accumulation image (link) shows several interesting features. There are two distinct bands of precipitation evident: the first was caused by Charley and spreads from the southwest coast to the northeast coast, and the second was caused by a frontal system that was dominating the weather in the northwest part of the state. That front was associated with a very strong low pressure system -- an autumn-like system that brought record cold temperatures to many parts of the Midwest and South. As Charley approached the southwest coast of Florida on the morning of August 13, areas in the eastern panhandle of Florida were being hit with heavy rain from this completely independent weather system. According to OneRain’s analysis, some areas in western Levy County received over 3 inches of rain, none of it actually associated with Charley.
 Storm Damage source: Associated Press |
We have prepared an animation (link), a 4 megabyte .AVI file, that illustrates how Charley moved across the region. The interplay between Charley and the frontal system was quite interesting to watch as Charley approached Florida. By the time Charley made landfall, rain from the frontal system was all but gone, yet that frontal system made a definite impact on the path of Charley by accelerating its turn to the northeast.
The heavy rain in and around the eye wall accounts for the southern swath of heavy precipitation seen in the total accumulation image (link). Considerably less precipitation fell west of Charley's eye than east of it; this shows up as the “valley” of low rainfall between rainfall from the frontal system and rainfall from Charley. Areas in and around Tampa, for example, received very little rain as they were caught in the neutral ground between Charley and the cold front.
 Storm Track source: NOAA |
As the hurricane tracked to the north-northeast, it did weaken a bit but still maintained hurricane status. The center of circulation passed right over Orlando (where a 105 mph wind gust was measured) and Daytona Beach (a gage 15 miles south of Daytona Beach registered a 15-minute average wind speed of 115 mph), and the eye is still clearly visible on the radar animation as it moves out over the Atlantic Ocean shortly after midnight.
OneRain’s analysis shows that total rainfall was relatively modest for a landfalling tropical system. This was due in part to the acceleration imparted on Charley by the upper-level winds associated with the frontal system. The area that received the most rainfall was the southwest/northeast corridor from Winter Haven, in central Polk County, to Orlando, in Orange County, to Sanford, in Seminole County. In isolated pockets in this region, rainfall estimates reached over 3.25 inches, with a maximum of 3.55 inches recorded just north of Orlando, near Fairview Shores. Orange County was perhaps the hardest hit, with widespread areas receiving over 3 inches of rain.
Rainfall in notable metropolitan areas included:Daytona Beach: 2.2 inches (ranging from just over 1.5 inches in the north part of town to over 3 inches in the south)
Fort Myers: 2.2 inches
Orlando: 2.4 inches
Punta Gorda (near landfall location): 1.7 inches
