Hurricane Dennis - Landfall Analysis

Dennis made landfall earlier this afternoon in the Florida panhandle just west of Navarre as a Category III hurricane - not quite as strong as originally anticipated. Analysis of aircraft and satellite data suggest that Dennis was in the process of an eyewall replacement cycle just a few hours before landfall - a cycle that never had a chance to complete itself because the hurricane ran out of ocean real estate - and thats fortunate. A few hours before landfall the eye began to look ragged and RECON confirmed that the intensity had decreased - significantly. Just prior to landfall, the hurricane was regaining strength, but the new eyewall never had a chance to fully complete its formation because of landfall. Some dry air intrusion also occurred (coming in from the west and south) and delayed any rapid development of the new eyewall. Here are some data points of interest:

1516Z: maximum flight level winds of 127 knots - translates to about 114 knots at the surface = Cat IV
1745Z: max flight level winds of 89 knots - translates to 80 knots at the surface = Cat I. This is the report that a lot of folks disregarded, but in fact it was when the original eyewall had collapsed.
1800Z: flight level winds rebound to 105 knots - or 95 knots at the surface = Cat II. The new eyewall begins to form.
1818Z: flight level max now reported at 118 knots - or about 103 knots at the surface = Cat III
1925Z: landfall near Navarre - one tower report of a sustained wind of 99mph (Cat II) at a location just east of the eyewall. Aircraft microwave measurements of 102-105 knots = Cat III
1930Z: aircraft max flight level wind report of 117 knots - about 105 knots at the surface = Cat III

Given the above, it seems likely that Dennis made landfall as a mid-strength Cat III Hurricane. Although the overall system was large, the core and eye were small and the Cat III winds would have only extended over a very narrow area west of Navarre.

As a post-script, Dennis is not the strongest storm to make landfall in this general area. Hurricane Eloise (1975) made landfall near Destin with sustained winds of 110 knots (also Cat III - and I was in Ft Walton for that one). I'm sure that there must have been others.

Although the winds near the center are barely at hurricane strength now, Dennis remains a significant rainmaker with a very real potential for flooding conditions as he moves northward and slows down in his forward speed. Folks in Alabama and Tennessee and elsewhere in the southeast still need to exercise caution and keep informed through their local meteorological services.
ED

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