Andrew was a small and ferocious Cape Verdehurricanethat wrought unprecedented economic devastation along a path through thenorthwestern Bahamas, the southern Florida peninsula, and south-central Louisiana.Damage in the United States is estimated to be near 25 billion, making Andrewthe most expensive natural disaster in U.S. history¹. Thetropical cyclone struck southern Dade County, Florida,especially hard, with violent winds andstorm surgescharacteristic of a category 4 hurricane (seeaddendum on upgrade to category 5) on theSaffir/SimpsonHurricane Scale, and with a central pressure (922 mb) that is thethird lowest this century for a hurricane at landfall in the UnitedStates. In Dade County alone, the forces of Andrew resulted in 15deaths and up to one-quarter million people left temporarily homeless. Anadditional 25 lives were lost in Dade County from the indirect effects ofAndrew². The direct loss of life seems remarkablylow considering the destruction caused by this hurricane.

a. Synoptic History

Satellite pictures and upper-air data indicate that Hurricane Andrewformed from atropical wavethat crossed from the west coast of Africa to the tropical North AtlanticOcean on 14 August 1992. The wave moved westward at about 20 kt, steered bya 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 thefollowing day. At that point, meteorologists at the NationalHurricane Center (NHC)Tropical Satellite Analysis and Forecast (TSAF) unit and theSynopticAnalysis Branch (SAB) of theNational Environmental Satellite Data and Information Service (NESDIS) foundthe wave sufficiently well-organized to begin classifying the intensity of the system using theDvorak (1984) analysis technique.

Convection subsequently became more focused in a region ofcyclonic cloud rotation. Narrow spiral-shaped bands of cloudsdeveloped around thecenterof rotation on 16 August. At 1800 UTC on the 16th (UTC precedes EDT by fourhours), both theTSAF unit and SAB calculateda Dvorak T-number of 2.0 and the"best track"(Table 1 andFig. 1 [85K GIF]) shows that thetransition from tropical wave totropical depressiontook place at that time.

The depression was initially embedded in an environment of easterly vertical windshear. By midday on the 17th, however, the shear diminished. The depression grew strongerand, at 1200 UTC 17 August, it became Andrew, the first Atlantictropical stormof the 1992hurricane season.The tropical cyclone continued moving rapidly on a heading which turned from westto west-northwest. This course was in the general direction of the Lesser Antilles.

Between the 17th and 20th of August, the tropical storm passedsouth of the center of the high pressure area over the easternAtlantic. Steering currents carried Andrew closer to a strongupper-level low pressure system centered about 500 n mi to theeast-southeast of Bermuda and to a trough that extended southwardfrom the low for a few hundred miles. These currents graduallychanged and Andrew decelerated on a course which became northwesterly.This change in heading spared the Lesser Antilles froman encounter with Andrew. The change in track also brought thetropical storm into an environment of strong southwesterly verticalwind shear and quite high surface pressures to its north. Althoughthe estimated maximum wind speed of Andrew varied little then, arather remarkable evolution occurred.

Satellite images suggest that Andrew produced deep convectiononly sporadically for several days, mainly in several bursts ofabout 12 hours duration. Also, the deep convection did not persist.Instead, it was stripped away from the low-level circulationby the strong southwesterly flow at upper levels. Air Force Reserve unit reconnaissance aircraft investigated Andrew and, onthe 20th, found that thecyclone haddegenerated to the extent that only a diffuse low-level circulationcenter remained. Andrew's central pressure rose considerably(Fig. 2 [87K GIF]). Nevertheless,the flight-level data indicated that Andrew retained a vigorouscirculation aloft. Wind speeds near70 kt were measured at analtitude of 1500 ft near a convective band lying to the northeastof the low-level center. Hence, Andrew is estimated on 20 August tohave been a tropical storm with40 kt surface winds and anastonishingly high central pressure of 1015 mb(Figs. 2 and 3 [87K GIF]).

Significant changes in the large-scale environment near anddownstream from Andrew began by 21 August. Satellite imagery inthe water vapor channel indicated that the low aloft to the east-southeastof Bermuda weakened and split. The bulk of the lowopened into a trough which retreated northward. That evolutiondecreased the vertical wind shear over Andrew. The remainder ofthe low dropped southward to a position just southwest of Andrewwhere its circulation enhanced the upper-level outflow over thetropical storm. At the same time, a strong and deep high pressurecell formed near the U.S. southeast coast. A ridge built eastwardfrom the high into the southwestern Atlantic with its axis lyingjust north of Andrew. The associated steering flow over thetropical 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 tropicalwave in nearly two years. Aneyeformed that morning and the rate of strengthening increased. Just 36 hours later,Andrew reached the borderline between a category 4 and 5 hurricane (seeaddendumon upgrade to category 5) and wasat its peak intensity (Table 1). From 0000 UTC on the 21st (whenAndrew had a barely perceptible low-level center) to 1800 UTC onthe 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 andqualifies asrapid deepening(Holliday and Thompson, 1979).

The region of high pressure held steady and drove Andrew nearlydue west for two and a half days beginning on the 22nd. Andrew wasa category 4 hurricane when its eye passed over northern EleutheraIsland in the Bahamas late on the 23rd and then over the southernBerry Islands in the Bahamas early on the 24th. After leaving theBahamas, Andrew continued moving westward toward southeast Florida.

Andrew weakened when it passed over the western portion of theGreat Bahama Bank and the pressure rose to 941 mb. However, thehurricane rapidly reintensified during the last few hours precedinglandfall when it moved over the Straits of Florida. During that period,radar, aircraft and satellite data showed a decreasing eye diameter andstrengthening"eyewall" convection.Aircraft and inland surface dataFig. 4 [121K GIF]) suggest that the deepening trend continued up to and slightly inland of the coast. Forexample, the eye temperature measured by the reconnaissance aircraftwas at least 1-2C warmer at 1010 UTC (an hour after the eyemade landfall) than it was in the last"fix"about 15 n mi offshore at 0804 UTC. These measurements suggest that the convectionin the eyewall, and the associated vertical circulation in the eye andeyewall, became more vigorous as the storm moved onshore. The radardata indicated that the convection in the northern eyewall becameenhanced with some strong convective elements rotating around theeyewall in a counter-clockwise fashion as the storm made landfall.Numerical models suggest that some enhancement of convection canoccur at landfall due to increased boundary-layer convergence inthe eyewall region. That situation appeared to have occurred inAndrew. The enhanced convection in the north eyewall probablyresulted in strong subsidence in the eye on the inside edge of thenorth eyewall. This likely contributed to a displacement of thelowest surface pressure to the north of the geometric center of the "radar eye"(cf.,Fig. 4 and6 [107K JPEG]). It is estimated that thecentral pressure was 922 mb at landfall near Homestead AFB, Florida at 0905UTC (5:05 A.M. EDT) 24 August (Fig. 4).

The maximum sustained surface wind speed (1-min average at 10meters [about 33 ft] elevation) during landfall over Florida isestimated at125 kt (about 145 mph), with gusts at that elevationto at least 150 kt (about 175 mph). The sustained wind speedcorresponds to a category 4 hurricane on theSaffir/SimpsonHurricane Scale (seeaddendumon upgrade to category 5). It should be noted that these wind speeds arewhat is estimated to have occurred within the (primarily northern)eyewall in an open environment such as at an airport, at thestandard 10-meter height. The wind experienced at other inlandsites was subject to complex interactions of the airflow withtrees, buildings, and other obstacles in its path. These obstructionscreate a turbulent, frictional drag that generally reducesthe wind speed. However, they can also produce brief, localaccelerations of the wind immediately adjacent to the structures.Hence, the wind speed experienced at a given location, such as ata house in the core region of the hurricane, can vary significantlyaround the structure, and cannot be specified with certainty. Thelandfall intensity is discussed further in Section b.

Andrew moved nearly due westward when over land and crossed theextreme southern portion of the Florida peninsula in about fourhours. Although the hurricane weakened about one category on theSaffir/Simpson Hurricane Scaleduring the transit over land, and the pressure rose to about 950 mb, Andrew was still a majorhurricane when its eyewall passed over the extreme southwestern Florida coast.

The first of two cycles of modest intensification commencedwhen the eye reached the Gulf of Mexico. Also, the hurricanecontinued to move at a relatively fast pace while its trackgradually turned toward the west-northwest.

When Andrew reached the north-central Gulf of Mexico, the highpressure system to its northeast weakened and a strong mid-latitudetrough approached the area from the northwest. Steering currentsbegan to change. Andrew turned toward the northwest and itsforward speed decreased to about 8 kt. The hurricane struck asparsely populated section of the south-central Louisiana coastwithcategory 3intensity at about 0830 UTC on the 26th. The landfall location is about 20 n miwest-southwest of Morgan City.

Andrew weakened rapidly after landfall, to tropical stormstrength in about 10 hours and to depression status 12 hours later.During this weakening phase, the cyclone moved northward and thenaccelerated northeastward. Andrew and its remnants continued toproduce 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 inFigs.2, 3,4,and5 (95K GIF).The first two of those figures show the curves of Andrew's central pressure andmaximum sustained one-minute wind speed, respectively, versus time, along with theobservations on which they were based. The figures contain relevantsurface observations and intensity estimates derived fromanalyses of satellite images performed by theTSAF unit,SAB and theAir Force Global Weather Central(USAF in figures). The aircraft data came from reconnaissance flights by theU.S. Air Force Reserve 815th Weather Reconnaissance Squadronbased at Keesler AFB, Mississippi. Additional data were collectedaboard aNOAA aircraft.

Table 2 lists a selection of surface observations.The anemometer at Harbour Island, near the northern end of Eleuthera Islandin the Bahamas, measured a wind speed of120 kt for an unknownperiod shortly after 2100 UTC on the 23rd. That wind speed was themaximum 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 closeproximity to Andrew at landfall in Florida. Homestead Air ForceBase and Tamiami Airport discontinued routine meteorologicalobservations prior to receiving direct hits from the hurricane.Miami International Airport was the next closest station, but itwas outside of the eyewall by about 5 nautical miles when Andrew'scenter passed to the south of that airport.

To supplement the official information, requests for data weremade to the public through the local media. Remarkably, more than100 quantitative observations were received (see Figs.4 and5).Many of the reports came from observers who vigilantlytook readings through frightening conditions including, in severalinstances, the moment when their instruments and even their homeswere destroyed.

Some of the unofficial observations were dismissed as unrealistic.Others were rendered suspect or eliminated during follow-upinquiries or analyses. The remainder, however, revealed a physicallyconsistent and reasonable pattern.

1. Minimum pressure over Florida

The final offshore "fix" by the reconnaissance aircraft came at0804 UTC and placed the center of the hurricane only about 15 nauticalmiles, or roughly one hour of travel time, from the mainland.A dropsonde indicated a pressure of 932 mb at that time. The pressurehad been falling at the rate of about 2 mb per hour, but theincreasing interaction with land was expected to at least partiallyoffset, if not reverse, that trend. Hence, a landfall pressurewithin a few millibars of 932 mb seemed reasonable.

Shortly after Andrew's passage, however, reports of minimumpressures below 930 mb were received from the vicinity ofHomestead, Florida (Fig. 4).Several of the barometers displaying the lowest pressures were subsequentlytested in a pressure chamber and calibrated by theAircraft Operations Center (AOC)ofNOAA.Two key observations came from a Mrs. Hall and Mr. Martens, sisterand brother. They rode out the storm in residences about one-quarter mileapart. Mrs. Hall's home was built by her father and grandfather in 1945to be hurricane-proof. Although some of the windows broke, the 22-inch thickconcrete and coral rock walls held steady, allowing her to observe herbarometer in relative safety. TheAOCtests indicate that the minimum pressure at her home was near 921 mb. The barometer at herbrother'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 pressurepattern to the coastline, Andrew's minimum pressure at landfall isestimated to be 922 mb. This suggests that the trajectory of thedropsonde deployed from the aircraft did not intersect the lowestpressure within the eye.

In the United States, this century, only theLabor Day (Keys') Storm in 1935 [103K GIF](892 mb) andHurricane Camille in 1969[122K GIF] (909 mb) had lower landfall central pressures than Andrew(Hebertet al. 1992).

2. Maximum wind speed over Florida (seeaddendumon upgrade to category 5)

The strongest winds associated with Andrew on 24 August likelyoccurred in the hurricane's northern eyewall. The relativelylimited number of observations in that area greatly complicates thetask of establishing Andrew's maximum sustained wind speed and peakgust at landfall in Florida. While a universally accepted valuefor Andrew's wind speed at landfall may prove elusive, there isconsiderable evidence supporting an estimate of about125 kt forthe maximum sustained wind speed, with gusts to at least 150 kt(Fig. 5). (Please seeaddendumon upgrade to category 5.)

The strongest reported sustained wind near the surface occurredat the Fowey Rocks weather station at 0800 UTC(Fig. 5). Thestation sits about 11 n mi east of the shoreline and, at that time,was within the northwest part of Andrew's eyewall. The 0800 UTCdata included a two-minute wind of123 kt with a gust to 147 kt ata platform height of about 130 ft. The U.S.National Data BuoyCenter used a boundary-layer model to convert the sustained wind toa two-minute wind of108 kt at 33 ft elevation. The peakone-minute wind during that two-minute period at Fowey Rocks might havebeen slightly higher than108 kt.

It is unlikely that this point observation was so fortuitouslysituated that it represents a sampling of the absolute strongestwind. The Fowey Rocks log (not shown) indicates that the windspeed increased through 0800 UTC. Unfortunately, Fowey Rocks thenceased transmitting data, presumably because even stronger windsdisabled the instrumentation. (A subsequent visual inspectionindicated that the mast supporting the anemometer had become bent90 degrees from vertical.) Radar reflectivity data suggests thatthe most intense portion of Andrew's eyewall had not reached FoweyRocks by 0800 UTC and that the wind speed could have continued toincrease there for another 15 to 30 minutes. A similar conclusioncan be reached from the pressure analysis inFig. 4 which indicatesthat the pressure at Fowey Rocks probably fell by about another 20mb from the 0800 UTC mark of 968 mb.

Reconnaissance aircraft provided wind data at a flight level ofabout 10,000 ft. The maximum wind speed along 10 seconds of flighttrack (often used by the NHC to represent a one-minute wind speedat flight level) on the last pass prior to landfall was162 kt,with a spot wind speed of170 kt observed. The162 kt wind occurredat 0810 UTC in the eyewall region about 10 n mi to the north ofthe center of the eye. Like the observation from Fowey Rocks, theaircraft provided a series of "point" observations (i.e., nolateral extent). Somewhat higher wind speeds probablyoccurred elsewhere in the northern eyewall, a little to the leftand/or to the right of the flight track. A wind speed at 10,000 ftis usually reduced to obtain a surface wind estimate. Based onpast operational procedures, the162 kt flight-level wind iscompatible with maximum sustained surface winds of125 kt.

One of the most important wind speed reports came from TamiamiAirport, located about 9 n mi west of the shoreline. As mentionedearlier, routine weather observations ended at the airport beforethe 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 speedindicator "pegged" at a position a little beyond the dial's highestmarking of100 kt, at a point that he estimates corresponds toabout110 kt. (Subsequent tests of the wind speed dials observed at theairport indicate that the needles peg at about105 kt and 108 kt, respectively). He recounts that the needle was essentially fixed atthat spot for three to five minutes, and then fell back to 0 whenthe anemometer failed. Mr. Morrison's observations have beenclosely corroborated by two other people. He has also noted thatthe weather conditions deteriorated even further after that timeand were at their worst about 30 minutes later. This informationsuggests that, in all likelihood, the maximum sustained wind speedat Tamiami Airport significantly exceeded105 kt.

A number of the wind speeds reported by the public could notbe substantiated and are therefore excluded fromFig. 5. Thereliability of some of the others suffer from problems that includenon-standard averaging periods and instrument exposures, and equipmentfailures 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(seeFig. 5).For at least 13 minutes the anemometer there showed99 kt, which was the maximum that the readout could display. Asmall downward adjustment of the speed should probably be appliedbecause the instrument was sitting 17 m above the surface ratherthan at the standard height of 10 m. On the other hand, thehighest one-minute wind speed during that 13-minute period couldhave been quite a bit stronger than99 kt. Again, there mayhave been stronger winds elsewhere in the southern eyewall. For a westward-movinghurricane the wind speed in the northern eyewall usually exceedsthe wind speed in the southern eyewall by about twice the forwardspeed of the hurricane (Dunn and Miller 1964). In the case ofAndrew, that difference is about 32 kt, and suggests a maximumsustained wind stronger than130 kt.

Several indirect measures of the sustained wind speed are ofinterest. First, a standard empirical relationship between centralpressure and wind speed (Kraft 1961) applied to 922 mb yieldsaround135 kt. Second, the Dvorak technique classification performedby the NHCTropical Satellite Analysis and Forecast unitusing a 0900 UTC satellite image gives127 kt. Also, an analysisof the pressure pattern inFig. 4gives a maximum gradient wind of around140 kt.

The strongest gust reported from near thesurface occurred in the northern eyewall a little more than a milefrom the shoreline at the home of Mr. Randy Fairbank. He observeda gust of184 kt moments before portions of a windward wall failed,preventing further observation. The hurricane also destroyed theanemometer. To evaluate the accuracy of the instrument, threeanemometers of the type used by Mr. Fairbank were tested in a windtunnel atVirginia Polytechnic Instituteand State University. Although the turbulent nature of thehurricane winds could not be replicated, the results of thewind tunnel tests suggest that the gust Mr. Fairbank observed wasless than 184 kt and probably near154 kt. Of course, strongergusts may have occurred there at a later time, or at another site.Damage at that location was significantly less than the damage tosimilar 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, especiallyin association with convective bands (Fig. 6).A peak gust to139 kt was observed at a home near the northern end ofDade County (Fig. 5) on an anemometer of the brand used byMr. Fairbank. Applying the reduction suggested by the wind tunnel tests to139 ktyields an estimate close to the115 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 endof the island of Eleuthera in the Bahamas and generated significant stormsurge flooding. Two high water marks were recorded and referenced tomean sea level. The first mark of 16 ft was recorded in a house in thetown of Little Bogue. The second mark of 23 ft was recorded in a damagedhouse in the town of The Current several miles west of Lower Bogue. Sincethis structure was located near the shoreline it suggests that batteringwaves 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 alongshorelines of southern Florida(Fig. 7)(103K GIF). On the southeast Florida coast, peak storm surge arrived near the time of highastronomical tide. The height of thestorm tide(the sum of the storm surge and astronomical tide, referenced to mean sea level) rangedfrom 4 to 6 ft in northern Biscayne bay increasing to a maximum value of 16.9 ft at the BurgerKing International Headquarters, located on the western shoreline in the centerof the bay, and decreasing to 4 to 5 ft in southern Biscayne Bay. The observedstorm 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 associatedwith Andrew over the Bahamas or Florida. Funnel sightings, someunconfirmed, were reported in the Florida counties of Glades,Collier and Highlands, where Andrew crossed in daylight. InLouisiana, one tornado occurred in the city of Laplace severalhours prior to Andrew's landfall. That tornado killed 2 people andinjured 32 others. Tornadoes in the Ascension, Iberville, BatonRouge, Pointe Coupee, and Avoyelles parishes of Louisiana reportedlydid not result in casualties. Numerous reports of funnel cloudswere received by officials in Mississippi and tornadoes weresuspected to have caused damage in several Mississippi counties.In Alabama, the occurrence of two damaging tornadoes has beenconfirmed over the mainland while another tornado may have hitDauphin Island. As Andrew and its remnants moved northeastwardover the eastern states, it continued to produce severe weather. For example, several damaging tornadoes in Georgia late on 27August were attributed to Andrew.

5. Rainfall

Andrew dropped sufficient rain to cause local floods eventhough the hurricane was relatively small and generally movedrather fast. Rainfall totals in excess of seven inches wererecorded in southeast Florida, Louisiana, and Mississippi(Table 2b). Rainfall amountsnear 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 anddamages associated with Andrew. The number of deaths directly attributed to Andrewis 26. The additional indirect loss of life brought the death tollto 65 (seefootnote 2). A combination ofgood hurricane preparedness and evacuation programs likely helpedminimize the loss of life. Nevertheless, the fact that no liveswere lost in the United States due to storm surge is viewed as afortunate aberration.

Table 3a reveals that more than one-half ofthe fatalities were indirect. Many of the indirect deaths occurredduring the "recovery phase" following Andrew's passage.

Damage is estimated at $25 billion. Andrew's impact onsouthern Dade County, Florida was extreme from the Kendall districtsouthward through Homestead and Florida City, to near Key Largo(Table 3b). Andrew reportedly destroyed 25,524 homesand damaged 101,241 others. The Dade County Grand Jury reported that ninetypercent of all mobile homes in south Dade County were totallydestroyed. In Homestead, more than 99% (1167 of 1176) of allmobile 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 theregions overspread by Andrew's eyewall and its accompanying coreof destructive winds and, near the coastline, decimating storm surges.Flight-level data about an hour prior to landfall places the radius ofmaximum 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 than11 n mi. (Figure 6) displays a radar reflectivitypattern (similar to rainfall intensity) about 30 minutes prior to landfall, superimposedon a map of southern Florida, from which it can be seen that the averagediameter 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 manyoffshore structures, including the artificial reef system of southeastFlorida. For example, the Belzona Barge is a 215 ft, 350-tonbarge that, prior to Andrew, was sitting in 68 ft of water on theocean floor. One thousand tons of concrete from the old Card Soundbridge lay on the deck. The hurricane moved the barge 700 ft tothe west (50-100 tons of concrete remain on deck) and removedseveral large sections of steel plate sidings.

Damage in the Gulf of Mexico is preliminarily estimated at $0.5billion. 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 wellsblown off location.

Hurricanes are notoriously capricious. Andrew was a compactsystem. A little larger system, or one making landfall just a fewnautical miles further to the north, would have been catastrophicfor heavily populated, highly commercialized and no less vulnerableareas to the north. That area includes downtown Miami, MiamiBeach, Key Biscayne and Fort Lauderdale. Andrew also left thehighly vulnerable New Orleans region relatively unscathed.

d. Forecast and Warning Critique

Track forecast errors by the NHC and by the suite of trackprediction models are given inTable 4.On average, the NHC errors were about 30% smaller than the current 10-yearaverage. The most significant changes in Andrew's track and intensity (seeFig. 1,Table 1)were generally well anticipated (noted in NHC'sTropical Cyclone Discussions) and the forecast tracks generally lieclose to the best track. However, the rate of Andrew's westwardacceleration over the southwestern Atlantic was greater thaninitially forecast. In addition, the NHC forecast a rate ofstrengthening that was less than what occurred during Andrew'speriod of rapid deepening.

Several of the dynamic track models had stellar performancesduring this hurricane. The Aviation Model and a tracking routinethat follows a simulated hurricane vortex (AVNO) performedespecially well. However, this was the first storm for which AVNOoutput was available to NHC forecasters. Hence, itsoperational reliability was not established. TheGFDL and QLM models also had small errors.It should be pointed out, however, that the NHC works on a six-hourlyforecast cycle and that the models mentioned above are runjust once per 12 hours. Moreover, the output from these modelsbecomes available to forecasters no earlier than the following six-hour forecast cycle.

Historically, the NHC90 statistical-dynamical model has beenthe most accurate of NHC's track guidance models. The NHC90errors were rather large during Andrew. Because the NHC90 usesoutput from the Aviation Model it is possible that the recentchanges in the latter model may be responsible for the NHC90'sdegraded performance.

Table 5 lists a chronology of watchesand warnings issued by the National Hurricane Center and the Government of the Bahamas.The associated lead times (based on landfall of the eye) are giveninTable 6.

Massive evacuations were ordered in Florida and Louisiana asthe 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 BrowardCounty, 315,000 in Palm Beach County and 15,000 in St. LucieCounty. For counties further west in Florida, evacuation totalsexceeding one thousand people are Collier (25,000), Glades (4,000)and Lee (2,500).

It is estimated that 1,250,000 people evacuated from parishesin southeastern and south-central Louisiana.

About 250,000 people evacuated from Orange and JeffersonCounties in Texas.

The winds in Hurricane Andrew wreaked tremendous structural damage, particularlyin southern Dade County. Notwithstanding, the loss of life inHurricane Andrew, while very unfortunate, was far less than haspreviously occurred in hurricanes of comparable strength. Historicaldata suggests that storm surge is the greatest threat to life.Some lives were likely saved by the evacuation along the coastlineof southeast Florida. The relatively small loss of life thereserves as testimony to the success and importance of coordinatedprograms 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 byNWSWSFO/WSO reports fromMIA,EYW, MLB, PBI,TBW,SIL, BTR,LCH,JAN,BHM,MOB,MEM, BPT andATL. Sam Houston of theAOML Hurricane Research Division collected additionalobservations. Jerry Kranz of theNOAA Aircraft Operations Center performed the barometercalibrations.Martin Nelson provided a summaryon the damages to artificial reefs adjacent to the southeast Florida coast.Joan David, Stan Goldenberg and Mike Black developed several ofthe figures. Sandra Potter helped prepare the manuscript.

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          [1] When indirect and continuing costs are considered,the total could ultimately rise to $40 billion, according to apersonal  communication  from William E. Bailey, Co-Director,Hurricane Insurance Information Center. Mr. Bailey indicates thatFloridians filed more than 725,000 insurance claims related toAndrew.

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          [2] Based on data from the Dade County Medical Examiner. The Miami Herald reported on 31 January 1993 that it could relateat least 43 additional (indirect) deaths in Dade County to HurricaneAndrew.