Hurricane Opal made landfall near Pensacola Beach, Florida as
a marginal Category 3 hurricane
on the Saffir/Simpson Hurricane
Scale, causing extensive storm surge
damage to the immediate coastal areas of the Florida panhandle. It was the first major
hurricane to strike the Florida panhandle since
Eloise in 1975 (103K GIF).
a. Synoptic History
Satellite imagery and synoptic analyses indicate that Opal
originated from a tropical wave
that emerged from the west coast of Africa on 11 September. The wave moved
westward across the Atlantic into the western Caribbean Sea by 23 September
and merged with a broad area of low pressure centered in the vicinity of 15N°
80°W. The combined system drifted west-northwestward toward the
Yucatan peninsula over the following few days without significant
development. Deep convection increased near the
center of the low and the post-analysis
"best track" in Figure 1
(108K GIF) shows that a tropical depression
formed about 70 n mi south-southeast of Cozumel, Mexico at 1800 UTC 27 September.
Best track position, central pressure and maximum one-minute sustained wind speed are
listed for every six hours in Table 1.
Steering currents were weak and the tropical depression moved
slowly over the Yucatan peninsula for the following three days.
Convective banding increased and ship reports suggest that the
depression became Tropical Storm
Opal at 1200 UTC 30 September while centered near the north-central coast
of the Yucatan peninsula. The storm gradually strengthened and moved slowly
westward into the Bay of Campeche.
Air Force Reserve unit
aircraft investigating Opal over the southwestern Gulf of Mexico
reported that the minimum central pressure steadily dropped. Aircraft reports
and satellite estimates
suggest that Opal strengthened into a hurricane near 1200 UTC 2 October while
centered about 150 n mi west of Merida, Mexico. A banding type
eye appeared in satellite imagery
later in the day while a large amplitude mid- to upper-level trough moving into the
central United States began turning Opal slowly toward the north.
On 3 and 4 October, the hurricane turned toward the north-
northeast to northeast and gradually accelerated. During this
period, the water temperature beneath the hurricane's circulation
was near 28 to 29C, and a large upper-level anticyclone was well
established over the Gulf of Mexico. Rapid intensification
occurred not only as a result of these favorable environmental
conditions on the large scale but, and perhaps more importantly,
due to significant changes on a smaller scale within the
hurricane's inner core. Opal intensified into a category four
hurricane on the Saffir/Simpson Hurricane Scale
early on 4 October at which time reconnaissance aircraft reported a small, 10 n mi
diameter eye. The minimum central pressure of 916 mb, with maximum
sustained surface winds estimated at 130 knots,
occurred when the hurricane was centered about 250 n mi south-southwest of Pensacola,
Florida near 1000 UTC 4 October. The peak intensity appears to
have occurred near the end of an eyewall
contraction cycle. Soon thereafter, the small inner eyewall diminished as an outer eyewall
became more dominant. The hurricane weakened during this process,
but was still a marginal Category 3 hurricane as the center made
landfall at Pensacola Beach, Florida near 2200 UTC 4 October. The
collapse of the inner eyewall, reduced sea surface temperatures
along the Gulf coast and increased upper-level westerlies likely
contributed to the weakening.
The hurricane was moving north-northeastward near 20 knots at
landfall with the sustained hurricane force winds in the eastern
quadrants of the circulation primarily between Pensacola Beach and
Cape San Blas. The minimum central pressure at landfall was 942
mb. Maximum sustained surface winds are currently estimated at 100
knots in a narrow swath at the coast near the extreme eastern tip
of Choctawhatchee Bay about midway between Destin and Panama City.
Although no official reports of surface winds were received within
this area, data from reconnaissance aircraft and Doppler radar
suggest that the peak winds occurred in this location. It should
be emphasized that the strongest winds were in a very limited area
and most of the coastal areas of the Florida panhandle experienced
winds of a Category 1 or Category 2 hurricane (between 65 and 95
knots). Although the winds were diminishing at the time of
landfall, extensive damage due to storm surge and breaking waves
occurred over most of the coastal areas of the Florida panhandle.
Opal weakened rapidly after moving inland, becoming a tropical
storm over southern Alabama and a tropical depression over southeastern Tennessee.
The cyclone was declared
extratropical on the best
track as it moved northeastward over the Ohio Valley and eastern Great Lakes into
southwestern Quebec. The strongest winds occurred well away from the center of the
cyclone during the extratropical stage.
b. Meteorological Statistics
Figure 2 (44K GIF) and
Figure 3 (51K GIF)
show the curves of minimum central pressure and
maximum one-minute wind speed, respectively, versus time, along
with the observations on which they are based.
U.S. Air Force Reserve
aircraft provided
a total of 38 operational center fixes
during approximately 122 flying hours of reconnaissance on this hurricane. The minimum central
pressure reported by aircraft was 916 mb at 0945 UTC 4 October. This
represented a 53 mb drop in pressure within 24 hours and a 42 mb
fall within about 12 hours. This was a very rapid rate of
deepening, but it is not unprecedented. Several western North
Pacific typhoons have deepened at an even faster rate. The maximum
winds of 152 knots from a flight-level of 700 mb were measured
shortly after the 916 mb pressure report. At 2006 UTC,
approximately two hours prior to landfall, the aircraft reported
126 knots 59 n mi east of the center. At 2203 UTC,
near the time of landfall, the aircraft reported 115 knots
54 n mi east of the center. In addition to the Air Force Reserve reconnaissance, a
NOAA aircraft
flew a 10 hour research mission at the time of landfall.
A ship with call sign XCKX reported 75 knot
winds at 1200 UTC 4 October while located about 90 n mi west-southwest of the
hurricane center. Several other ship reports were helpful in
defining the extent of tropical storm force winds. Table 2 lists
ship reports of at least tropical storm force winds in the vicinity
of Opal.
The strongest winds reported by a land station were 73 knots
with gusts to 125 knots from Hurlbert Field, Florida. Table 3a
lists selected surface observations, and Table 3b lists selected
observations made by NOAA's National Data Buoy Center (NDBC)
platforms near the path of Opal.
Isolated tornadoes were reported from the Florida panhandle to
the mid-Atlantic states. One fatality occurred in Crestview,
Florida as a result of a tornado. Another tornado injured several
people and severely damaged a number of structures as it swept
through Charles, Prince Georges and Anne Arundel Counties in Maryland.
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 from
southeastern Mobile Bay and Gulf Shores, Alabama, eastward through
the Florida panhandle to Cedar Key, Florida. Still water mark
elevations inside of buildings or tide gage maximums, which damp
out breaking wave effects and are indicative of the storm surge,
ranged from 5 to 14 feet above mean sea level. Outside water marks
on buildings or debris lines on sand dunes within 200 feet of the
Gulf of Mexico shoreline generally ranged from 10 to 21 feet. For
example, the tide gage at the Panama City Beach pier recorded a
maximum of approximately 8.3 feet above mean sea level, indicative
of storm surge. At the end of the pier a debris line elevation of
approximately 18 feet above mean sea level was recorded. Thus, the
breaking waves on top of the storm surge added approximately 10
feet. Many structures in this combined storm surge and breaking
wave zone that were not elevated high enough suffered major
structural damage.
The combination of Opal and a frontal system resulted in heavy
rains along the path of the hurricane. Rainfall totals generally
ranged from 5 to 10 inches over portions of the Florida panhandle,
Alabama and Georgia. Rains in South Carolina averaged 2 to 4
inches while in North Carolina 3 to 5 inches were common.
Highlands, North Carolina recorded 8.95 inches and Robinson Creek,
North Carolina recorded 9.89 inches. Elsewhere, 1 to 3 inch totals
occurred over portions of the northeast U.S. from Maryland
northward. These rains have been described as beneficial to areas
of the northeast U.S. that had been experiencing a prolonged dry period.
c. Casualty and Damage Statistics
The total number of deaths directly associated with Opal is
currently set at 59, and were distributed as follows:
Guatemala - 31 (from flooding during the developing stages of
Opal)
Mexico - 19 (from flooding)
U.S. - 9 including
Florida (1 from a tornado)
Alabama (2 from a tree falling on a mobile home)
Georgia (5 from falling trees)
North Carolina (1 from a tree falling on a mobile home)
There were no reported deaths due to storm surge flooding,
which is remarkable in view of the vulnerable population and
extensive salt water damage observed.
The Property Claim Services Division of the American Insurance
Services Group preliminary estimate of insured property damage for
the United States is $2.1 billion. Considerable uncertainty exists
concerning the amount of additional damage due to flood claims,
uninsured property damage (including damage to roads and bridges
and other government property) and the cost of cleanup. If the
estimate of insured property damage proves to be correct, the total
damage estimate from Hurricane Opal could reach $3 billion.
Without adjustments for inflation, Opal could rank as high as third
on the list of costliest twentieth-century U.S. hurricanes. With
adjustments for inflation, Opal will likely still be ranked in the
top ten on that list.
Most of the severe structural damage occurred at the coastline.
The crumbled piers, demolished homes and eroded or submerged
highways were primarily a result of the storm surge. In addition,
however, strong winds spread damage well inland. Opal downed
numerous trees, knocking out power to nearly 2 million people in
Florida, Alabama, Georgia and the Carolinas. The Robert Trent Golf
Course in Opelika, Alabama lost over 7000 trees during the storm.
Many people in Florida were without water for several days.
d. Forecast and Warning Critique
During the time when Opal was of tropical storm or hurricane
strength, the mean official track forecast errors of 42 (18 cases),
102 (16 cases), 161 (14 cases), 231 (12 cases) and 326 (8 cases) n
mi at 12, 24, 36, 48 and 72 hours respectively were slightly larger
than the long-term averages from the previous ten years.
The intensity forecasts showed a negative bias (i.e., intensity
was underestimated). The trend for the strengthening of Opal while
over water was correctly forecast by the NHC, but the amount of
rapid deepening was not anticipated by the official forecasts or by
any available objective intensity prediction techniques.
Table 4 lists the coastal watches and warnings
issued during Opal. Approximately 31 hours elapsed between the time a
hurricane watch was issued and
the time of landfall on the Florida panhandle. Approximately 19 hours
elapsed between the time of issuance of a
hurricane warning
was issued and the time of landfall.
Table 4. Watch and warning summary, Hurricane Opal.
Date/Time (UTC) | Action | Location |
30/1500 | Tropical Storm Warning |
Northeast portion of the Yucatan Peninsula from Cozumel and Cancun to Progreso |
01/0300 | Tropical Storm Warning extended |
Yucatan Peninsula from Progreso to Celestun |
01/2100 |
Tropical Storm Warning extended |
Yucatan Peninsula from Progreso to Veracruz |
Tropical Storm Warning discontinued |
Yucatan Peninsula east of Progreso |
03/0900 | Hurricane Watch |
Morgan City, Louisiana to just west of Pensacola, Florida |
03/1500 |
Hurricane Watch extended |
Pensacola to the Mouth of the Suwannee River, Florida |
Tropical Storm Warning discontinued |
All portions of the Yucatan Peninsula |
03/2100 | Tropical Storm Warning |
Morgan City, Louisiana to the Mouth of the Suwannee River, Florida |
04/0300 | Hurricane Warning |
Mobile, Alabama to Anclote Key, Florida |
Tropical Storm Warning extended |
South of Anclote Key to Venice, Florida |
Tropical Storm Warning and Hurricane Watch discontinued |
West of Grand Isle to Morgan City, Louisiana |
04/0900 |
Hurricane Warning extended |
Mobile, Alabama westward to the Mouth of the Mississippi River including coastal
Mississippi |
Tropical Storm Warning and
Hurricane Watch extended |
Grand Isle, Louisiana westward to just east of Morgan City, Louisiana including
Metropolitan New Orleans |
05/0300 |
Tropical Storm Warning, Hurricane Warning, and Hurricane Watch
discontinued | West of Mobile, Alabama |
05/0500 |
All remaining coastal Watches and Warnings discontinued |
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