Preliminary Report
Hurricane Floyd
07 - 13 September 1993

1993 PRELIMINARY REPORTS

Tropical Storm Arlene (TS)
Tropical Storm Bret (TS)
Tropical Storm Cindy (TS)
Tropical Storm Dennis (TS)
Hurricane Emily (3)
Hurricane Floyd (1)
Hurricane Gert (2)
Hurricane Harvey (1)

a. Synoptic History

Floyd formed from a tropical wave that crossed the west coast of Africa on 28 August accompanied by relatively large height falls at low levels of the atmosphere. Inland surface reports in the vicinity of Dakar, and observations from several ships, indicate that the wave also contained a well-defined low-level cyclonic circulation surrounding a low level pressure center of about 1009 mb on the 28th and 29th.

Satellite pictures indicate that the low moved steadily westward for about a week with deep convection periodically developing in its vicinity. Initial Dvorak technique satellite classifications began on the 29th, but by late on the 31st the system became "too weak to classify" when thunderstorm activity nearly ceased. Deep convection redeveloped on 3 September about 500 nautical miles to the east of the Leeward Islands, but significant strengthening was limited by a southwesterly vertical wind shear.

The area of disturbed weather then gradually began to move northwestward and become better organized. On the 6th, a reconnaissance flight by a unit of the U.S. Air Force Reserve detected a broad area of surface pressures near 1011 mb centered within a weak low-level circulation about 150 nautical miles north of the Virgin Islands. On the following day, a reconnaissance mission detected a 1008 mb low within a small, low-level circulation associated with persistent thunderstorm activity. Flight-level winds of 67 mph were measured at an altitude of 1500 feet that afternoon. The aircraft data is the basis for indicating in the "best track" that the system became a tropical depression during the morning of the 7th and strengthened to become Tropical Storm Floyd during the afternoon.

Floyd quickly became embedded in the fast air currents between a strong large-scale trough approaching the tropical cyclone from the northwest and a subtropical high to the east. The steering flow accelerated Floyd northward to 23 mph, and the storm's center passed about 200 nautical miles to the west of Bermuda on 8 September. Strong southwesterly wind shear kept the system from strengthening and, in fact, the last reconnaissance flight in Floyd indicated that the central pressure had risen to 1012 mb by mid day on the 8th. The system still appeared sheared on the day's final visible satellite pictures, with a low-level cloud center appearing poorly-organized on the southwestern edge of the main area of convective clouds.

Floyd's structure changed considerably over night and the storm intensified. By morning, the low-level circulation center was no longer exposed, but estimated to be near the center of the convective overcast. The storm was racing northeastward at about 40 mph near the eastern end of the ribbon of warm Gulf Stream waters. Beginning near 1500 UTC, satellite imagery occasionally showed a recessed spot within the deep clouds near the estimated circulation center that could be interpreted as a partially formed eye. At 2000 UTC, the circulation center of Floyd passed about 40 nautical miles to the northwest of Canadian Buoy 44141. The buoy reported a pressure of 998 mb, a sea-surface temperature of 27.1°C, and a peak 2-minute wind of 69 mph during the hour ending at 2000 UTC. It is quike likely that a 1-minute wind speed of at least 74 mph occurred elsewhere within the southern part of the surface circulation, probably a little closer to the circulation center. Based on this analysis and the hint of an eye on satellite pictures, Floyd is estimated to have become a hurricane with 75 mph maximum 1-minute surface wind speed at 1800 UTC on the 9th.

Floyd's forward speed continued to increase late on the 9th and early on the 10th. The hurricane was moving at nearly 52 mph when it began to lose its tropical characteristics over 19°C water. Deep convection diminished on the 10th, and as the day progressed, it became displaced further to the northeast of the estimated low-level circulation center. Ship reports indicated an expanded wind field to the south. The system is estimated to have become an extratropical storm with 75 mph winds at 1800 UTC on the 10th.

Surface data indicate that the extratropical storm decelerated on an eastward heading over the following two days. The system began another deepening phase on the 11th and its center swept inland on the Brittany coast of France early on the 13th with a pressure of about 966 mb and estimated maximum sustained surface winds near 81 mph.

b. Meteorological Statistics

The hurricane is estimated to have maintained maximum sustained winds of 75 mph and a minimum pressure of 990 mb until becoming extratropical.

c. Casualty and Damage Statistics

No reports of damage or casualties related to Floyd have been received by the NHC.