Synoptic History of Hurricane Floyd
Cooperative Institute for Meteorological Satellite Studies, Space Science and Engineering Center, University of Wisconsin-Madison
Table of Location, Pressure and Wind Speed during Life of Hurricane Floyd
Stages of Development of Hurricanes
Following Text adapted from the Preliminary Report
by Richard J. Pasch, Todd B. Kimberlain and Stacy R. Stewart
National Hurricane Center
18 November 1999
Hurricane Floyd, 7 - 17 September, 1999
Floyd can be traced back to an easterly wave that emerged from western Africa on 2 Sept. This system was not impressive, in terms of the organization of the convection shown on satellite images, but there was evidence of curvature in the cloud lines. The system was recognizable as a synoptic-scale entity.
The wave proceeded westward across the eastern tropical Atlantic at about the normal speed of propagation of easterly waves (6 degrees of longitude per day) for several days. Late on 5-Sept, near 15N 32.5W, a center of circulation was estimated, but the system lacked much deep convection. On 6-Sept there was a curved band of deep convection present. A favorable upper-level outflow pattern existed over the area, and the cloud pattern became more consolidated and better organized on 7-Sept.
By 1800 UTC on 7-Sept the disturbance became a Tropical Depression, located about 1000 miles east of the Lesser Antilles. A deep layer ridge prevailed to the north of the cyclone and the associated steering current moved the system west-northwestward at 12-15 knots.
When it reached a position about 750 n mi (nautical miles) east of the 3 Leeward Islands, the cloud pattern became sufficiently well organized for the system to become Tropical Storm Floyd by 0600 UTC on 8-Sep. Although large-scale conditions appeared conducive for strengthening, there was a lack of a well-defined inner core.
The tropical storm slowly strengthened and became Hurricane Floyd by 1200 UTC on 10-Sept. At this point, the hurricane was centered about 200 n miles east-northeast of the northern Leeward Islands. As Floyd was nearing hurricane status, a mid-tropospheric trough in the vicinity of 60-65W longitude caused a slowing of the forward speed, and then a turn toward the northwest. The northwest motion continued until the 11th, keeping the hurricane well to the northeast of the islands of the northeastern Caribbean.
After strengthening nearly to category 3 status early on the 11th, the hurricane weakened to 85 knots around 0000 UTC on the 12th. Early on the 12th, rising mid- to upper-tropospheric heights to the north of Floyd forced a turn toward the west. The westward turn also marked the beginning of a major strengthening episode. Maximum sustained winds increased from 95 knots to 135 knots, and the central pressure fell about 40 mb from early on the 12th to early on the 13th. The minimum central pressure recorded was 921 mb. From 0600 to 1800 on the 13th, Floyd was at the top end of category four intensity on the Saffir/Simpson Hurricane Scale.
Floyd was aimed at the central Bahamas until late on the 13th, when the heading became west-northwestward. The eye passed just 20 to 30 n mi northeast and north of San Salvador and Cat Islands on the night of the 13th. Floyd's eyewall passed over central and northern Eleuthera on the morning of the 14th, and after turning toward the northwest, Floyd struck Abaco island on the afternoon of the 14th. By the time the hurricane hit Abaco, it had weakened somewhat from its peak, but Floyd was still a borderline category three/four hurricane.
As a mid- to upper-tropospheric trough over the eastern United States eroded the subtropical ridge over the extreme western Atlantic, Floyd continued to turn gradually to the right. The center of the hurricane paralleled the central Florida coast, passing about 95 n mi east of Cape Canaveral around 0900 UTC 15 September. By the afternoon of the15th, Floyd was abeam of the Florida/Georgia border and headed northward toward the Carolinas.
Although there was a fluctuation in intensity, related to an eyewall replacement event discussed in the next section, overall the intensity of Floyd diminished from the 13th to the 15th. Environmental causes for intensity change are not entirely understood, but two large-scale factors probably contributed to a gradual decline: the entrainment of drier air at low levels from the northwest, and increasing south-southwesterly vertical shear. As Floyd neared the North Carolina coast late on the 15th, its maximum winds decreased below category three status.
After turning toward the north-northeast with forward speed increasing to near 15 knots, Hurricane Floyd made landfall near Cape Fear, North Carolina at 0630 UTC 16 September as a category two hurricane with estimated maximum winds near 90 knots. Floyd was losing its eyewall structure as it made landfall. Continuing to accelerate north-northeastward, Floyd's center passed over extreme eastern North Carolina on the morning of the 16th and over the greater Norfolk, Virginia area around 1500 UTC that day. Floyd then weakened to a tropical storm and moved swiftly along the coasts of the Delmarva peninsula and New Jersey on the afternoon and early evening of the 16th, reaching Long Island by 0000 UTC 17 September. By that time, the storm's forward speed had increased to near 29 knots. The system decelerated as it moved into New England.
By late on the 16th and early on the 17th, Floyd was becoming more involved with a frontal zone that existed along the Atlantic seaboard. The system took the form of a frontal low and thus became extratropical by the time it reached the coast of Maine at 1200 UTC 17 September. The cyclone turned toward the northeast and then east-northeast, moving over the coast of New Brunswick late on the 17th, Prince Edward Island early on the 18th and Newfoundland late on the 18th and early on the 19th. Floyd's extratropical remnant merged with a large extratropical low over the north Atlantic and was no longer a distinct entity by 1800 UTC 19 September.
Heavy rainfall preceded Floyd over the mid-Atlantic states due to a pre-existing frontal zone and the associated overrunning. Hence, even though the tropical cyclone was moving fairly quickly, precipitation amounts were very large. Rainfall totals as high as 15 to 20 inches were recorded in portions of eastern North Carolina and Virginia. At Wilmington, North Carolina, the storm total of 19.06 inches included a 24-hour record of 15.06 inches. Totals of 12 to 14 inches were observed in Maryland, Delaware, and New Jersey. New records were set in Philadelphia for the most amount of rain in a calendar day, 6.63 inches. In southeastern New York, rainfall totals were generally in the 4 to 7 inch range but there was a report of 13.70 inches at Brewster. Totals of nearly 11 inches were measured in portions of New England. Storm surge values as high as 9 to 10 feet were reported along the North Carolina coast.
A number of tornadoes were sighted in eastern North Carolina. There was a confirmed tornado in Bertie County and another in Perquimans County. The latter tornado destroyed two houses and damaged three or four others. At least ten tornadoes were reported by spotters in the Newport/Morehead City County Warning area, and these apparently caused some structural damage. Four tornadoes or funnel clouds were seen in the Wilmington area, but no damage was apparent.
Casualty and Damage Statistics
There were 57 deaths that were directly attributable to Floyd, 56 in the United States and 1 in Grand Bahama Island. The death toll by state is as follows: North Carolina 35, Pennsylvania 6, New Jersey 6, Virginia 3, Delaware 2, New York 2, Connecticut 1, and Vermont 1. Most of these deaths were due to drowning in freshwater flooding. Floyd was the deadliest hurricane in the United States since Agnes of 1972.
In the United States, the Property Claims Services Division of the Insurance Services Office reports that insured losses due to Floyd totaled 1.325 billion dollars. Ordinarily this figure would be doubled to estimate the total damage. However, in comparison to most hurricane landfalls, in the case of Floyd there was an inordinately large amount of freshwater flood damage, which probably alters the two to one damage ratio. Total damage estimates range from 3 to over 6 billion dollars.