Hurricane Fran formed from a
tropical wave that emerged from the west coast of Africa on 22 August.
Deep convection associated with the wave was organized in a banding-type
pattern and animation of satellite images suggested a cyclonic
circulation. Ship reports soon confirmed that the circulation was on the
surface. The post-analysis "best track" in Figure 1 shows that the system
became a tropical depression just southeast of the Cape Verde Islands at
1200 UTC 23 August. Best track position, central pressure and maximum
one-minute sustained wind speed are listed for every six hours in Table 1.
The tropical depression moved westward near 15 knots for the next few days
without significant development. This lack of development may be
attributed, in part, to disrupted low-level inflow due to the large and
powerful Hurricane Edouard which was centered about 750 n mi to the
west-northwest. Satellite intensity estimates suggest that the depression
became Tropical Storm Fran at 1200 UTC 27 August while located about 900 n
mi east of the Lesser Antilles.
Fran began to track toward the west-northwest in the wake of Hurricane
Edouard. Deep convection became more concentrated and Fran is estimated to
have reached hurricane status at 0000 UTC 29 August while centered about
400 n mi east of the Leeward Islands. The center of Fran was about 150 n
mi to the northeast of the Leeward Islands near 1200 UTC 30 August.
The tropical cyclone weakened to just below hurricane strength later on
the 30th, possibly due to the low-level inflow being disrupted again by
Edouard. About this time, changing steering currents caused Fran to turn
toward the northwest and slow to about 5 knots.
By 1200 UTC 31 August, as
Edouard moved farther away, Fran had regained hurricane strength. As
Hurricane Edouard moved northward off the U.S. mid-Atlantic coast, the
subtropical ridge became better established to the north of Fran, causing
Fran to resume a west-northwestward motion with an increased forward speed
of about 10 knots. Fran moved on a track roughly parallel to the Bahama
Islands with the eye remaining a little more than 100 n mi to the
northeast of the islands.
Fran strengthened to a category three hurricane by the time it was
northeast of the central Bahamas on 4 September. The powerful tropical
cyclone began to be influenced by a cyclonic circulation centered over
Tennessee that was most pronounced in mid to upper levels of the
atmosphere. Fran was steered by the resulting flow around the low over
Tennessee and the western extension of the subtropical ridge over the
northwest Atlantic. The hurricane gradually turned toward the northwest to
north- northwest and increased in forward speed.
The minimum central pressure
dropped to 946 mb and maximum sustained surface winds reached
105 knots, Fran's peak intensity, near 0000 UTC
5 September when the hurricane was centered about 250 n mi east of the
Florida east coast.
Fran was moving northward near
15 knots when it made landfall on the North Carolina coast. The center
moved over the Cape Fear area around 0030 UTC 6 September, but the
circulation and radius of maximum winds were large and hurricane force
winds likely extended over much of the North Carolina coastal areas of
Brunswick, New Hanover, Pender, Onslow and Carteret counties. At landfall,
the minimum central pressure is estimated at 954 mb and the maximum
sustained surface winds are estimated at 100 knots.
The strongest winds likely occurred in streaks within the deep convective
areas north and northeast of the center.
Fran weakened to a tropical storm while centered over central North Carolina and
subsequently to a tropical depression while moving through Virginia. The
tropical cyclone gradually lost its warm core as it moved over the eastern Great
Lakes and became extratropical near 0000 UTC 9 September while centered over
southern Ontario. The remnants of Fran were absorbed into a frontal system near
0600 UTC 10 September.
Meteorological Statistics
Figures 2 and 3 show the curves of minimum
central sea-level pressure and maximum one-minute "surface" wind speed,
respectively, as a function of time. The observations on which the curves
are based are also plotted and consist of aircraft reconnaissance data and
Dvorak-technique estimates using satellite imagery, as well as synoptic
fixes after landfall. According to international agreements within the
world meteorological community, the surface wind is actually the wind
representative of 33 feet (10 meters) above the ground.
All operational aircraft
reconnaissance flights into Fran were provided by the U.S. Air Force
Reserves. These
"Hurricane Hunters" made 71 center fixes during 17 flights. The minimum
central pressure reported by aircraft was 946 mb at 2306 UTC 4 September.
A circular eye with a diameter of 25 n mi was observed on aircraft radar
at this time. The 946 mb minimum pressure was measured by dropsonde and
was the lowest pressure reported during Fran's existence. The maximum
winds of 114 knots from a flight level of 700 mb
(near 10,000 feet) were measured about 6 hours prior to the 946 mb
pressure report. Flight-level winds in excess of 100 knots were reported
several times during the two days prior to landfall.
113-knot winds were reported from aircraft 52 n mi east of the
hurricane center at 2314 UTC 5 September, and 107-knot
winds were reported 41 n mi northeast of the center at the time of
landfall. However, the core of the hurricane weakened somewhat on radar
presentations, and a closed eyewall was not reported by aircraft during
the two hours prior to the center moving onshore.
Objective intensity estimates from digital infrared satellite imagery
peaked near the time that the minimum central pressure was reported by
reconnaissance aircraft.
The WSR-88D (Weather Surveillance Radar - 1988 Doppler) at Wilmington, North
Carolina, measured winds in excess of 120 knots aloft
as the inner convective bands approached the Cape Fear area at 2130 UTC 5
September.
A ship with call sign LAVX4 reported 85 knot
winds and a pressure of 984 mb at 1800 UTC 5 September while located about 60 n
mi northeast of the hurricane center. Several other ship reports were helpful in
defining the extent of tropical storm force winds, as were reports from a
network of drifting buoys deployed offshore of the Carolinas in advance of Fran.
Table 2 lists ship reports of at least tropical storm force winds in the
vicinity of Fran.
Several wind gusts to hurricane force were measured from coastal areas in North
Carolina. As usual for landfalling hurricanes, however, reports of sustained
hurricane force winds are difficult to find. Table 3 lists selected U.S. surface
observations. The NOAA C-MAN station at Frying Pan Shoals (about 50 n mi
south-southeast of Wilmington, North Carolina) reported sustained winds of
79 knots and gusts to 108 knots
from a tower about 80 feet above sea level.
Numerous pressure and wind reports from North Carolina were relayed to the NHC
through amateur radio volunteers. The lowest measured pressure was 954 mb from
Southport. The highest measured wind gust was 119 knots
at an elevation of 30 feet (mounted on a house approximately 4 feet above the
chimney) from a Davis wind instrument located on Hewletts Creek in Wilmington. A
gust to 109 knots was measured in Wrightsville Beach.
Although these measurements are very much desired to supplement the more
official observations, they will not be listed in Table 3 until their accuracy
is verified.
Several tornadoes were indicated by Doppler radar in North Carolina and
Virginia. Confirmation, however, has been difficult due to the extensive nature
of straight line wind damage across the region.
At the time of this report, a post-storm high water mark survey was being
conducted by the U.S. Army Corps of Engineers and the U.S. Geological Survey.
Many high water marks remain to be surveyed and "tied into" bench marks. The
locations of the maximum values cannot be finalized until the survey is
complete. However, initial survey results show an extensive storm surge along
the North Carolina coast primarily southwest of Cape Lookout. Still water mark
elevations on the inside of buildings, indicative of the storm surge, range from
8 to 12 feet. Outside water marks on buildings or debris lines are higher due to
the effect of breaking waves.
Rainfall totals exceeding six inches were common near the path of Fran. WSR-88D
radar precipitation estimates were as high as 12 inches over portions of
Brunswick and Pender counties in North Carolina. Extensive flooding spread well
inland from the Carolinas into Virginia, West Virginia and Pennsylvania. Some of
this flooding was considered the most severe in years. Near Washington, D.C.,
for example, the Old Town district of historic Alexandria was partially
evacuated as the Potomac River rose, flooding streets with more than three feet
of water. The next update of this report will include an analysis of rainfall
along the path of Fran to be provided by the NWS Eastern Region Headquarters.
Casualty and Damage Statistics
According to Associated Press reports, Hurricane Fran was responsible for 34
deaths. Most of the deaths were caused by flash flooding in the Carolinas,
Virginia, West Virginia and Pennsylvania. Twenty-one died in North Carolina
alone. However, the total death count will likely be revised downward in the
next update of this report based on data from NWS personnel to be published in
Storm Data, since the NWS attempts to list deaths directly attributable
to the weather. For example, most vehicle accidents and heart attacks from
over-exertion after a hurricane are not considered direct deaths.
Storm surge on the North Carolina coast destroyed or seriously damaged numerous
beachfront houses. Widespread wind damage to trees and roofs, as well as downed
power lines, occurred as Fran moved inland over North Carolina and Virginia.
Extensive flooding was responsible for additional damage in the Carolinas,
Virginia, West Virginia, Maryland, Ohio and Pennsylvania.
Nearly a half-million tourists and residents were ordered to evacuate the coast
in North and South Carolina. Press reports from Reuters News Service stated that
4.5 million people in the Carolinas and Virginia were left without power.
The Property Claim Services Division of the American Insurance Services Group
reports that Fran caused an estimated $1.6 billion dollars in insured property
damage to the United States. This estimate includes $1.275 billion in North
Carolina, $20 million in South Carolina, $175 million in Virginia, $50 million
in Maryland, $20 million in West Virginia, $40 million in Pennsylvania and $20
million in Ohio. A conservative ratio between total damage and insured property
damage, compared to past landfalling hurricanes, is two to one. Therefore, the
total U.S. damage estimate is $3.2 billion.
Forecast and Warning Critique
During Fran's life as a
tropical storm or hurricane, the average official track forecast errors
ranged from 66 n mi at 24 hours (37 cases) to 137 n mi at 48 hours (33
cases) to 185 n mi at 72 hours (29 cases). These errors are at least 25
percent less than the previous ten-year averages of the official track
errors.
The BAMD (deep-layer Beta and
Advection Model) and the GFDI (interpolated version of the Geophysical
Fluid Dynamics Laboratory model) provided the best guidance in terms of
the lowest track forecast errors. However, the GFDI model showed a
distinct bias to the left of the actual track (Figure 4). The guidance
from this model, which is generally acknowledged to be the most accurate
one operationally available to the NHC, resulted in some left bias in the
official forecasts near landfall.
Most NHC intensity forecast errors were 15 knots or less. All but one
intensity forecast made after 2100 UTC 02 September correctly indicated a
landfalling category three hurricane.
Table 4 lists the various
watches and warnings that were issued. Hurricane warnings were posted for
the hardest hit portions of the North Carolina coast about 27 hours prior
to landfall.
