a. Synoptic History
Satellite pictures and upper-air data indicate that
Hurricane Andrew formed from a tropical wave
that crossed from the west coast of Africa to the tropical North
Atlantic Ocean on 14 August 1992. The wave moved westward at about 20
kt, steered by a swift and deep easterly current on the south side of an
area of high pressure. The wave passed to the south of the Cape Verde
Islands on the following day. At that point, meteorologists at the
National Hurricane Center (NHC) Tropical Satellite
Analysis and Forecast (TSAF) unit and the Synoptic Analysis Branch (SAB) of
the National
Environmental Satellite Data and Information Service (NESDIS) found
the wave sufficiently well-organized to begin classifying the intensity
of the system using the Dvorak (1984)
analysis technique.
Convection subsequently became more focused in a region of
cyclonic cloud rotation. Narrow spiral-shaped bands of clouds developed
around the center of
rotation on 16 August. At 1800 UTC on the 16th (UTC precedes EDT by four
hours), both the TSAF unit and SAB
calculated a Dvorak T-number of 2.0 and the "best track" (Table 1 and Fig. 1 [85K
GIF]) shows that the transition from tropical wave to tropical
depression took place at that time.
The depression was initially embedded in an environment of
easterly vertical wind shear. By midday on the 17th, however, the shear
diminished. The depression grew stronger and, at 1200 UTC 17 August, it
became Andrew, the first Atlantic tropical
storm of the 1992 hurricane
season. The tropical cyclone continued moving rapidly on a heading
which turned from west to west-northwest. This course was in the general
direction of the Lesser Antilles.
Between the 17th and 20th of August, the tropical storm
passed south of the center of the high pressure area over the eastern
Atlantic. Steering currents carried Andrew closer to a strong
upper-level low pressure system centered about 500 n mi to the
east-southeast of Bermuda and to a trough that extended southward from
the low for a few hundred miles. These currents gradually changed and
Andrew decelerated on a course which became northwesterly. This change
in heading spared the Lesser Antilles from an encounter with Andrew. The
change in track also brought the tropical storm into an environment of
strong southwesterly vertical wind shear and quite high surface
pressures to its north. Although the estimated maximum wind speed of
Andrew varied little then, a rather remarkable evolution
occurred.
Satellite images suggest that Andrew produced deep
convection only sporadically for several days, mainly in several bursts
of about 12 hours duration. Also, the deep convection did not persist.
Instead, it was stripped away from the low-level circulation by the
strong southwesterly flow at upper levels. Air Force Reserve unit
reconnaissance aircraft investigated Andrew and, on the 20th, found that
the cyclone
had degenerated to the extent that only a diffuse low-level circulation
center remained. Andrew's central pressure rose considerably (Fig. 2 [87K
GIF]). Nevertheless, the flight-level data indicated that Andrew
retained a vigorous circulation aloft. Wind speeds near 70 kt were measured at an altitude of 1500 ft near a
convective band lying to the northeast of the low-level center. Hence,
Andrew is estimated on 20 August to have been a tropical storm with
40 kt surface winds and an astonishingly high
central pressure of 1015 mb (Figs. 2 and 3
[87K GIF]).
Significant changes in the large-scale environment near and
downstream from Andrew began by 21 August. Satellite imagery in the
water vapor channel indicated that the low aloft to the east-southeast
of Bermuda weakened and split. The bulk of the low opened into a trough
which retreated northward. That evolution decreased the vertical wind
shear over Andrew. The remainder of the low dropped southward to a
position just southwest of Andrew where its circulation enhanced the
upper-level outflow over the tropical storm. At the same time, a strong
and deep high pressure cell formed near the U.S. southeast coast. A
ridge built eastward from the high into the southwestern Atlantic with
its axis lying just north of Andrew. The associated steering flow over
the tropical storm became easterly. Andrew turned toward the west,
accelerated to near 16 kt, and quickly intensified.
Andrew reached hurricane strength on the morning of 22
August, thereby becoming the first Atlantic hurricane to form from a
tropical wave in nearly two years. An eye formed that
morning and the rate of strengthening increased. Just 36 hours later,
Andrew reached the borderline between a category 4 and 5 hurricane and
was at its peak intensity (Table 1). From
0000 UTC on the 21st (when Andrew had a barely perceptible low-level
center) to 1800 UTC on the 23rd the central pressure had fallen by 92
mb, down to 922 mb. A fall of 72 mb occurred during the last 36 hours of
that period and qualifies as rapid deepening
(Holliday and Thompson, 1979).
The region of high pressure held steady and drove Andrew
nearly due west for two and a half days beginning on the 22nd. Andrew
was a category 4 hurricane when its eye passed over northern Eleuthera
Island in the Bahamas late on the 23rd and then over the southern Berry
Islands in the Bahamas early on the 24th. After leaving the Bahamas,
Andrew continued moving westward toward southeast Florida.
Andrew weakened when it passed over the western portion of
the Great Bahama Bank and the pressure rose to 941 mb. However, the
hurricane rapidly reintensified during the last few hours preceding
landfall when it moved over the Straits of Florida. During that period,
radar, aircraft and satellite data showed a decreasing eye diameter and
strengthening "eyewall"
convection. Aircraft and inland surface data Fig. 4 [121K
GIF]) suggest that the deepening trend continued up to and slightly
inland of the coast. For example, the eye temperature measured by the
reconnaissance aircraft was at least 1-2C warmer at 1010 UTC (an hour
after the eye made landfall) than it was in the last "fix" about 15 n
mi offshore at 0804 UTC. These measurements suggest that the convection
in the eyewall, and the associated vertical circulation in the eye and
eyewall, became more vigorous as the storm moved onshore. The radar data
indicated that the convection in the northern eyewall became enhanced
with some strong convective elements rotating around the eyewall in a
counter-clockwise fashion as the storm made landfall. Numerical models
suggest that some enhancement of convection can occur at landfall due to
increased boundary-layer convergence in the eyewall region. That
situation appeared to have occurred in Andrew. The enhanced convection
in the north eyewall probably resulted in strong subsidence in the eye
on the inside edge of the north eyewall. This likely contributed to a
displacement of the lowest surface pressure to the north of the
geometric center of the "radar eye" (cf., Fig. 4 and 6 [107K
JPEG]). It is estimated that the central pressure was 922 mb at landfall
near Homestead AFB, Florida at 0905 UTC (5:05 A.M. EDT) 24 August (Fig.
4).
The maximum sustained surface wind speed (1-min average at
10 meters [about 33 ft] elevation) during landfall over Florida is
estimated at 125 kt (about 145 mph), with gusts at that
elevation to at least 150 kt (about 175 mph). The sustained wind
speed corresponds to a category 4 hurricane on the Saffir/Simpson Hurricane
Scale. It should be noted that these wind speeds are what is
estimated to have occurred within the (primarily northern) eyewall in an
open environment such as at an airport, at the standard 10-meter height.
The wind experienced at other inland sites was subject to complex
interactions of the airflow with trees, buildings, and other obstacles
in its path. These obstructions create a turbulent, frictional drag that
generally reduces the wind speed. However, they can also produce brief,
local accelerations of the wind immediately adjacent to the structures.
Hence, the wind speed experienced at a given location, such as at a
house in the core region of the hurricane, can vary significantly around
the structure, and cannot be specified with certainty. The landfall
intensity is discussed further in Section b.
Andrew moved nearly due westward when over land and crossed
the extreme southern portion of the Florida peninsula in about four
hours. Although the hurricane weakened about one category on the Saffir/Simpson Hurricane
Scale during the transit over land, and the pressure rose to about
950 mb, Andrew was still a major hurricane when its eyewall passed over
the extreme southwestern Florida coast.
The first of two cycles of modest intensification commenced
when the eye reached the Gulf of Mexico. Also, the hurricane continued
to move at a relatively fast pace while its track gradually turned
toward the west-northwest.
When Andrew reached the north-central Gulf of Mexico, the
high pressure system to its northeast weakened and a strong mid-latitude
trough approached the area from the northwest. Steering currents began
to change. Andrew turned toward the northwest and its forward speed
decreased to about 8 kt. The hurricane struck a sparsely populated
section of the south-central Louisiana coast with category 3 intensity
at about 0830 UTC on the 26th. The landfall location is about 20 n mi
west-southwest of Morgan City.
Andrew weakened rapidly after landfall, to tropical storm
strength in about 10 hours and to depression status 12 hours later.
During this weakening phase, the cyclone moved northward and then
accelerated northeastward. Andrew and its remnants continued to produce
heavy rain that locally exceeded 10 inches near its track (Table 2b). By
midday on the 28th, Andrew had begun to merge with a frontal system over
the mid-Atlantic states.
b. Meteorological Statistics
The best track intensities were obtained from the data
presented in Figs. 2, 3, 4, and 5 (95K GIF).
The first two of those figures show the curves of Andrew's central
pressure and maximum sustained one-minute wind speed, respectively,
versus time, along with the observations on which they were based. The
figures contain relevant surface observations and intensity estimates
derived from analyses of satellite images performed by the TSAF unit, SAB and the Air Force Global
Weather Central (USAF in figures). The aircraft data came from
reconnaissance flights by the U.S. Air Force Reserve
815th Weather Reconnaissance Squadron based at Keesler AFB, Mississippi.
Additional data were collected aboard a NOAA
aircraft.
Table 2 lists
a selection of surface observations. The anemometer at Harbour Island,
near the northern end of Eleuthera Island in the Bahamas, measured a
wind speed of 120 kt for an unknown period
shortly after 2100 UTC on the 23rd. That wind speed was the maximum that
could be registered by the instrument.
Neither of the two conventional measures of hurricane
intensity, central barometric pressure and maximum sustained wind speed,
were observed at official surface weather stations in close proximity to
Andrew at landfall in Florida. Homestead Air Force Base and Tamiami
Airport discontinued routine meteorological observations prior to
receiving direct hits from the hurricane. Miami International Airport
was the next closest station, but it was outside of the eyewall by about
5 nautical miles when Andrew's center passed to the south of that
airport.
To supplement the official information, requests for data
were made to the public through the local media. Remarkably, more than
100 quantitative observations were received (see Figs. 4 and 5). Many of
the reports came from observers who vigilantly took readings through
frightening conditions including, in several instances, the moment when
their instruments and even their homes were destroyed.
Some of the unofficial observations were dismissed as
unrealistic. Others were rendered suspect or eliminated during follow-up
inquiries or analyses. The remainder, however, revealed a physically
consistent and reasonable pattern.
1. Minimum pressure over Florida
The final offshore "fix" by the reconnaissance aircraft
came at 0804 UTC and placed the center of the hurricane only about 15
nautical miles, or roughly one hour of travel time, from the mainland. A
dropsonde indicated a pressure of 932 mb at that time. The pressure had
been falling at the rate of about 2 mb per hour, but the increasing
interaction with land was expected to at least partially offset, if not
reverse, that trend. Hence, a landfall pressure within a few millibars
of 932 mb seemed reasonable.
Shortly after Andrew's passage, however, reports of minimum
pressures below 930 mb were received from the vicinity of Homestead,
Florida (Fig.
4). Several of the barometers displaying the lowest pressures were
subsequently tested in a pressure chamber and calibrated by the Aircraft Operations
Center (AOC) of NOAA. Two key
observations came from a Mrs. Hall and Mr. Martens, sister and brother.
They rode out the storm in residences about one-quarter mile apart. Mrs.
Hall's home was built by her father and grandfather in 1945 to be
hurricane-proof. Although some of the windows broke, the 22-inch thick
concrete and coral rock walls held steady, allowing her to observe her
barometer in relative safety. The AOC tests indicate
that the minimum pressure at her home was near 921 mb. The barometer at
her brother's home was judged a little more reliable and the reading
there was adjusted to 923 mb. Based on the observations and an eastward
extrapolation of the pressure pattern to the coastline, Andrew's minimum
pressure at landfall is estimated to be 922 mb. This suggests that the
trajectory of the dropsonde deployed from the aircraft did not intersect
the lowest pressure within the eye.
In the United States, this century, only the Labor Day (Keys') Storm
in 1935 [103K GIF] (892 mb) and Hurricane Camille in
1969 [122K GIF] (909 mb) had lower landfall central pressures than
Andrew (Hebert et al. 1992).
2. Maximum wind speed over Florida
The strongest winds associated with Andrew on 24 August
likely occurred in the hurricane's northern eyewall. The relatively
limited number of observations in that area greatly complicates the task
of establishing Andrew's maximum sustained wind speed and peak gust at
landfall in Florida. While a universally accepted value for Andrew's
wind speed at landfall may prove elusive, there is considerable evidence
supporting an estimate of about 125 kt for the maximum
sustained wind speed, with gusts to at least 150 kt (Fig.
5).
The strongest reported sustained wind near the surface
occurred at the Fowey Rocks weather station at 0800 UTC (Fig. 5). The
station sits about 11 n mi east of the shoreline and, at that time, was
within the northwest part of Andrew's eyewall. The 0800 UTC data
included a two-minute wind of 123 kt with a gust to 147
kt at a platform height of about 130 ft. The U.S. National Data Buoy Center used
a boundary-layer model to convert the sustained wind to a two-minute
wind of 108 kt at 33 ft elevation. The peak
one-minute wind during that two-minute period at Fowey Rocks might have
been slightly higher than 108 kt.
It is unlikely that this point observation was so
fortuitously situated that it represents a sampling of the absolute
strongest wind. The Fowey Rocks log (not shown) indicates that the wind
speed increased through 0800 UTC. Unfortunately, Fowey Rocks then ceased
transmitting data, presumably because even stronger winds disabled the
instrumentation. (A subsequent visual inspection indicated that the mast
supporting the anemometer had become bent 90 degrees from vertical.)
Radar reflectivity data suggests that the most intense portion of
Andrew's eyewall had not reached Fowey Rocks by 0800 UTC and that the
wind speed could have continued to increase there for another 15 to 30
minutes. A similar conclusion can be reached from the pressure analysis
in Fig. 4
which indicates that the pressure at Fowey Rocks probably fell by about
another 20 mb from the 0800 UTC mark of 968 mb.
Reconnaissance aircraft provided wind data at a flight
level of about 10,000 ft. The maximum wind speed along 10 seconds of
flight track (often used by the NHC to represent a one-minute wind speed
at flight level) on the last pass prior to landfall was 162 kt, with a spot wind speed of 170
kt observed. The 162 kt wind occurred at
0810 UTC in the eyewall region about 10 n mi to the north of the center
of the eye. Like the observation from Fowey Rocks, the aircraft provided
a series of "point" observations (i.e., no lateral extent). Somewhat
higher wind speeds probably occurred elsewhere in the northern eyewall,
a little to the left and/or to the right of the flight track. A wind
speed at 10,000 ft is usually reduced to obtain a surface wind estimate.
Based on past operational procedures, the 162 kt
flight-level wind is compatible with maximum sustained surface winds of
125 kt.
One of the most important wind speed reports came from
Tamiami Airport, located about 9 n mi west of the shoreline. As
mentioned earlier, routine weather observations ended at the airport
before the full force of Andrew's (northern) eyewall winds arrived.
However, the official weather observer there, Mr. Scott Morrison,
remained on-station and continued to watch the wind speed dial. Mr.
Morrison notes that around 0845 UTC (0445 EDT) the wind speed indicator
"pegged" at a position a little beyond the dial's highest marking of
100 kt, at a point that he estimates corresponds
to about 110 kt. (Subsequent tests of the wind
speed dials observed at the airport indicate that the needles peg at
about 105 kt and 108 kt, respectively). He
recounts that the needle was essentially fixed at that spot for three to
five minutes, and then fell back to 0 when the anemometer failed. Mr.
Morrison's observations have been closely corroborated by two other
people. He has also noted that the weather conditions deteriorated even
further after that time and were at their worst about 30 minutes later.
This information suggests that, in all likelihood, the maximum sustained
wind speed at Tamiami Airport significantly exceeded 105 kt.
A number of the wind speeds reported by the public could
not be substantiated and are therefore excluded from Fig. 5. The
reliability of some of the others suffer from problems that include
non-standard averaging periods and instrument exposures, and equipment
failures prior to the arrival of the strongest winds.
The only measurement of a sustained wind in the southern
eyewall came from an anemometer on the mast of an anchored sailboat (see
Fig. 5).
For at least 13 minutes the anemometer there showed 99
kt, which was the maximum that the readout could display. A small
downward adjustment of the speed should probably be applied because the
instrument was sitting 17 m above the surface rather than at the
standard height of 10 m. On the other hand, the highest one-minute wind
speed during that 13-minute period could have been quite a bit stronger
than 99 kt. Again, there may have been stronger
winds elsewhere in the southern eyewall. For a westward-moving hurricane
the wind speed in the northern eyewall usually exceeds the wind speed in
the southern eyewall by about twice the forward speed of the hurricane
(Dunn and Miller 1964). In the case of Andrew, that difference is about
32 kt, and suggests a maximum sustained wind stronger than 130 kt.
Several indirect measures of the sustained wind speed are
of interest. First, a standard empirical relationship between central
pressure and wind speed (Kraft 1961) applied to 922 mb yields around
135 kt. Second, the Dvorak technique
classification performed by the NHC Tropical Satellite
Analysis and Forecast unit using a 0900 UTC satellite image gives
127 kt. Also, an analysis of the pressure
pattern in Fig. 4 gives
a maximum gradient wind of around 140
kt.
The strongest gust reported from near the surface occurred
in the northern eyewall a little more than a mile from the shoreline at
the home of Mr. Randy Fairbank. He observed a gust of 184 kt moments before portions of a windward wall
failed, preventing further observation. The hurricane also destroyed the
anemometer. To evaluate the accuracy of the instrument, three
anemometers of the type used by Mr. Fairbank were tested in a wind
tunnel at Virginia Polytechnic Institute
and State University. Although the turbulent nature of the hurricane
winds could not be replicated, the results of the wind tunnel tests
suggest that the gust Mr. Fairbank observed was less than 184 kt and
probably near 154 kt. Of course, stronger gusts
may have occurred there at a later time, or at another site. Damage at
that location was significantly less than the damage to similar
structures located about 2 miles south of this neighborhood, implying
even stronger winds than observed at this location.
Strong winds also occurred outside of the eyewall,
especially in association with convective bands (Fig. 6). A
peak gust to 139 kt was observed at a home near
the northern end of Dade County (Fig. 5) on an
anemometer of the brand used by Mr. Fairbank. Applying the reduction
suggested by the wind tunnel tests to 139 kt
yields an estimate close to the 115 kt peak gust
(a five-second average) registered on a National Ocean Survey anemometer
located not far to the east, at the coast.
3. Storm surge
During the afternoon of 23 August, Andrew crossed over the
north end of the island of Eleuthera in the Bahamas and generated
significant storm surge flooding. Two high water marks were recorded and
referenced to mean sea level. The first mark of 16 ft was recorded in a
house in the town of Little Bogue. The second mark of 23 ft was recorded
in a damaged house in the town of The Current several miles west of
Lower Bogue. Since this structure was located near the shoreline it
suggests that battering waves riding on top of the storm surge helped to
create this very high water mark.
During the morning hour of 24 August, Andrew generated
storm surge along shorelines of southern Florida (Fig. 7)
(103K GIF). On the southeast Florida coast, peak storm surge arrived
near the time of high astronomical tide. The height of the storm tide (the
sum of the storm surge and astronomical tide, referenced to mean sea
level) ranged from 4 to 6 ft in northern Biscayne bay increasing to a
maximum value of 16.9 ft at the Burger King International Headquarters,
located on the western shoreline in the center of the bay, and
decreasing to 4 to 5 ft in southern Biscayne Bay. The observed storm
tide values on the Florida southwest coast ranged from 4 to 5 ft near
Flamingo to 6 to 7 ft near Goodland.
Storm tides in Louisiana were at least 8 ft (Table 2a) and
caused flooding from Lake Borgne westward through Vermillion
Bay.
4. Tornadoes
There have been no confirmed reports of tornadoes
associated with Andrew over the Bahamas or Florida. Funnel sightings,
some unconfirmed, were reported in the Florida counties of Glades,
Collier and Highlands, where Andrew crossed in daylight. In Louisiana,
one tornado occurred in the city of Laplace several hours prior to
Andrew's landfall. That tornado killed 2 people and injured 32 others.
Tornadoes in the Ascension, Iberville, Baton Rouge, Pointe Coupee, and
Avoyelles parishes of Louisiana reportedly did not result in casualties.
Numerous reports of funnel clouds were received by officials in
Mississippi and tornadoes were suspected to have caused damage in
several Mississippi counties. In Alabama, the occurrence of two damaging
tornadoes has been confirmed over the mainland while another tornado may
have hit Dauphin Island. As Andrew and its remnants moved northeastward
over the eastern states, it continued to produce severe weather. For
example, several damaging tornadoes in Georgia late on 27 August were
attributed to Andrew.
5. Rainfall
Andrew dropped sufficient rain to cause local floods even
though the hurricane was relatively small and generally moved rather
fast. Rainfall totals in excess of seven inches were recorded in
southeast Florida, Louisiana, and Mississippi (Table 2b).
Rainfall amounts near five inches occurred in several neighboring
states. Hammond, Louisiana reported the highest total, 11.92
inches.
c. Casualty and Damage Statistics
Table 3 lists
a count of casualties and damages associated with Andrew. The number of
deaths directly attributed to Andrew is 26. The additional indirect loss
of life brought the death toll to 65 (see footnote 2). A
combination of good hurricane preparedness and evacuation programs
likely helped minimize the loss of life. Nevertheless, the fact that no
lives were lost in the United States due to storm surge is viewed as a
fortunate aberration.
Table 3a
reveals that more than one-half of the fatalities were indirect. Many of
the indirect deaths occurred during the "recovery phase" following
Andrew's passage.
Damage is estimated at $25 billion. Andrew's impact on
southern Dade County, Florida was extreme from the Kendall district
southward through Homestead and Florida City, to near Key Largo (Table 3b).
Andrew reportedly destroyed 25,524 homes and damaged 101,241 others. The
Dade County Grand Jury reported that ninety percent of all mobile homes
in south Dade County were totally destroyed. In Homestead, more than 99%
(1167 of 1176) of all mobile homes were completely destroyed. The Miami
Herald reported $0.5 billion in losses to boats in southeast
Florida.
The most devasted areas correspond closely in location to
the regions overspread by Andrew's eyewall and its accompanying core of
destructive winds and, near the coastline, decimating storm surges.
Flight-level data about an hour prior to landfall places the radius of
maximum wind at 11 n mi (in the northern eyewall at 10,000 ft altitude).
The radius of maximum wind at the surface was likely a little less than
11 n mi. (Figure 6)
displays a radar reflectivity pattern (similar to rainfall intensity)
about 30 minutes prior to landfall, superimposed on a map of southern
Florida, from which it can be seen that the average diameter of the
"radar" eye was about 11 n mi at landfall.)
The damage to Louisiana is estimated at $1 billion.
Damage in the Bahamas has been estimated at $0.25
billion.
Andrew whipped up powerful seas which extensively damaged
many offshore structures, including the artificial reef system of
southeast Florida. For example, the Belzona Barge is a 215 ft, 350-ton
barge that, prior to Andrew, was sitting in 68 ft of water on the ocean
floor. One thousand tons of concrete from the old Card Sound bridge lay
on the deck. The hurricane moved the barge 700 ft to the west (50-100
tons of concrete remain on deck) and removed several large sections of
steel plate sidings.
Damage in the Gulf of Mexico is preliminarily estimated at
$0.5 billion. Ocean Oil reported the following in the Gulf of Mexico: 13
toppled platforms, five leaning platforms, 21 toppled satellites, 23
leaning satellites, 104 incidents of structural damage, seven incidents
of pollution, two fires, and five drilling wells blown off
location.
Hurricanes are notoriously capricious. Andrew was a compact
system. A little larger system, or one making landfall just a few
nautical miles further to the north, would have been catastrophic for
heavily populated, highly commercialized and no less vulnerable areas to
the north. That area includes downtown Miami, Miami Beach, Key Biscayne
and Fort Lauderdale. Andrew also left the highly vulnerable New Orleans
region relatively unscathed.
d. Forecast and Warning Critique
Track forecast errors by the NHC and by the suite of track
prediction models are given in
Table 4. On
average, the NHC errors were about 30% smaller than the current 10-year
average. The most significant changes in Andrew's track and intensity
(see Fig.
1, Table
1) were generally well anticipated (noted in NHC's Tropical Cyclone
Discussions) and the forecast tracks generally lie close to the best
track. However, the rate of Andrew's westward acceleration over the
southwestern Atlantic was greater than initially forecast. In addition,
the NHC forecast a rate of strengthening that was less than what
occurred during Andrew's period of rapid deepening.
Several of the dynamic track models had stellar
performances during this hurricane. The Aviation Model and a tracking
routine that follows a simulated hurricane vortex (AVNO) performed
especially well. However, this was the first storm for which AVNO output
was available to NHC forecasters. Hence, its operational reliability was
not established. The GFDL and QLM
models also had small errors. It should be pointed out, however, that
the NHC works on a six-hourly forecast cycle and that the models
mentioned above are run just once per 12 hours. Moreover, the output
from these models becomes available to forecasters no earlier than the
following six-hour forecast cycle.
Historically, the NHC90 statistical-dynamical model has
been the most accurate of NHC's track guidance models. The NHC90 errors
were rather large during Andrew. Because the NHC90 uses output from the
Aviation Model it is possible that the recent changes in the latter
model may be responsible for the NHC90's degraded performance.
Table 5 lists
a chronology of watches and warnings issued by the National Hurricane
Center and the Government of the Bahamas. The associated lead times
(based on landfall of the eye) are given in
Table
6.
Massive evacuations were ordered in Florida and Louisiana
as the likelihood of Andrew making landfall in those regions increased
(Table 7).
About 55,000 people left the Florida Keys. Evacuations were ordered for
517,000 people in Dade County, 300,000 in Broward County, 315,000 in
Palm Beach County and 15,000 in St. Lucie County. For counties further
west in Florida, evacuation totals exceeding one thousand people are
Collier (25,000), Glades (4,000) and Lee (2,500).
It is estimated that 1,250,000 people evacuated from
parishes in southeastern and south-central Louisiana.
About 250,000 people evacuated from Orange and Jefferson
Counties in Texas.
The winds in Hurricane Andrew wreaked tremendous structural
damage, particularly in southern Dade County. Notwithstanding, the loss
of life in Hurricane Andrew, while very unfortunate, was far less than
has previously occurred in hurricanes of comparable strength. Historical
data suggests that storm surge is the greatest threat to life. Some
lives were likely saved by the evacuation along the coastline of
southeast Florida. The relatively small loss of life there serves as
testimony to the success and importance of coordinated programs of
hurricane preparedness.
References
Dunn, G. E. and B. I. Miller, 1964: Atlantic Hurricanes. Louisiana State University Press, Baton Rouge, LA. 326 pp.
Dvorak, V. F., 1984: Tropical cyclone intensity analysis using satellite data. NOAA Technical Report
NESDIS 11, National Oceanic and Atmospheric Administration, U. S. Department of Commerce, Washington, DC, 47 pp.
Hebert, P. J., J. D. Jarrell, and M. Mayfield, 1992: The deadliest, costliest, and most intense hurricane of this century (and other frequently requested facts). NOAA Technical Memorandum NWS NHC-31, National Oceanic and Atmospheric Administration, U.S. Department of Commerce, Washington, DC, 40 pp.
Holliday, C. R., and A. H. Thompson, 1979: Climatological characteristics of rapidly intensifying typhoons. Mon. Wea. Rev., 107, 1022-1034.
Kraft, R. H., 1961: The hurricane's central pressure and highest wind. Mar. Wea. Log., 5, 157.
Acknowledgments
Much of the data in this summary was provided by NWS WSFO/WSO
reports from MIA, EYW, MLB, PBI, TBW, SIL, BTR, LCH, JAN, BHM, MOB, MEM,
BPT and ATL. Sam
Houston of the AOML Hurricane
Research Division collected additional observations. Jerry Kranz of
the NOAA Aircraft
Operations Center performed the barometer calibrations. Martin Nelson provided a summary
on the damages to artificial reefs adjacent to the southeast Florida
coast. Joan David, Stan Goldenberg and Mike Black developed several of
the figures. Sandra Potter helped prepare the manuscript.
[1] When indirect and continuing costs are considered, the total could ultimately rise to $40 billion, according to a personal communication from William E. Bailey, Co-Director, Hurricane Insurance Information Center. Mr. Bailey indicates that Floridians filed more than 725,000 insurance claims related to
Andrew.
[2] Based on data from the Dade County Medical Examiner. The Miami Herald reported on 31 January 1993 that it could relate at least 43 additional (indirect) deaths in Dade County to Hurricane Andrew.
