The 1999 Hurricane Season in East Central Florida—Multiple Storms with Multiple Impacts

During the 1999 Hurricane season, Tropical Cyclones Dennis, Floyd, Harvey, and Irene threatened east central Florida, requiring the issuance of Hurricane and/or Tropical Storm watches/warnings on four separate occasions. Hurricanes Floyd and Irene produced the most significant impacts across the region, although the intensity and direction of approach of these two hurricanes were starkly different. Floyd was a category four on the Saffir-Simpson scale and remained offshore, but tracked to within 185 km of the peninsula. Irene, a category one hurricane, made landfall over southwest Florida, then surprisingly weakened little while traversing over land for nearly 12 hours before reaching the east central coast. Irene then maintained minimal hurricane intensity while moving nearly parallel to the coast for several hours. This paper will concentrate upon the potential and realized impacts across east central Florida from these two very different hurricanes.

Within 24 hours of Floyd's closest point of approach, the forecast track indicated the potential for the western eyewall to reach the coastline. Local forecast products and information provided to emergency managers indicated the likelihood of category one hurricane conditions, but also stressed that a small deviation west of the expected track would bring very damaging category three winds onshore. Based on the strength of the hurricane, large radius of maximum winds, and uncertainty associated with the exact track, a massive coastal evacuation was ordered by local officials. The eventual hurricane track featured a small shift east of the official forecast, and thus limited the most serious effects to damaging wind gusts along the immediate coast and severe beach erosion.

Local forecasts during Irene initially stressed the threat of heavy rainfall and a minimal threat of wind damage as the hurricane was expected to weaken to a tropical storm and pass over the central Florida interior. Evacuations of coastal residents were not ordered, in sharp contrast to large scale evacuations ordered only weeks earlier due to Floyd. As Irene approached central Florida however, a more eastward track ensued, allowing the system to maintain minimal hurricane intensity and restricting excessive rains to a small coastal swath. This short term change in the track required quick modifications to local forecasts, strongly emphasizing imminent damaging wind gusts near the coast, and a reduced chance for flooding inland rains. As the center of Irene reached the Atlantic during the early morning hours, radar imagery indicated a reorganization of inner convective bands. These bands affected east central Florida coastal counties for over 12 hours as the center of the hurricane moved slowly up the coast. Although sustained winds did not reach hurricane force, wind gusts over 33.5 m/s and rain totals over 120 mm were recorded across several coastal counties, resulting in more extensive damage than had occurred during Floyd.