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Preliminary Report
Hurricane Irene
13 - 19 October 1999

Lixion A. Avila
National Hurricane Center
22 November 1999

Tropical Storm Arlene
Tropical Depression Two
Hurricane Bret
Hurricane Cindy
Hurricane Dennis
Tropical Storm Emily
Tropical Depression Seven
Hurricane Floyd
Hurricane Gert
Tropical Storm Harvey
Tropical Depression Eleven
Tropical Depression Twelve
Hurricane Irene
Hurricane Jose
Tropical Storm Katrina
Hurricane Lenny

[1999 Atlantic Hurricane Season]

Irene was a typical wet October tropical cyclone that moved over the Florida Keys and southeast Florida dumping from 10 to 20 inches of rain. This resulted in severe flooding conditions. This type of tropical cyclone was a common phenomena during the 30's and 40's. Figure 1 shows the track of Irene over Cuba and Florida.

Figure 1. Detailed track of Irene showing the landfall points and a GOES 8 visible satellite image at the time of landfall near Flamingo, Florida.

a. Synoptic History

A broad area of low pressure prevailed over the southwestern Caribbean from the 8th to the 10th of October, accompanied by disorganized clouds and thunderstorms. This system did not show signs of tropical cyclone development until a tropical wave reached the western Caribbean Sea on 11 October. On the 12th, a U.S. Air Force Reserve reconnaissance plane was dispatched to the region and found an incipient low-level circulation and a broad low pressure area of 1006 mb just to the northeast of the coast of Honduras. However, the circulation was too disorganized to be classified as a tropical depression. Satellite imagery during the night showed that the thunderstorm activity increased and both banding features and upper-level outflow became quite distinct. Post -analysis of surface and upper-air data from Grand Cayman, and satellite Dvorak T-numbers indicate that Tropical Depression Thirteen formed in the northwestern Caribbean Sea about 0600 UTC 13 October. It reached tropical storm status by 1200 UTC on the 13th. Data from a reconnaissance aircraft later in the day confirmed Irene was a strengthening tropical storm. Irene moved on a general northward track and slowed down considerably before curving to the north-northeast just to the southwest of the Isle of Youth, Cuba, where it made its first landfall at 1200 UTC 14 October. Radars from Cuba and Key West showed the center of Irene moving on a north-northeast track over western Cuba. The center of the tropical cyclone then crossed the Havana and Ciudad Havana provinces between 2100 and 2300 UTC on the 14th. Irene reached hurricane status over the Florida Straits and the calm of the center moved over Key West near 1300 UTC 15 October. Most of the hurricane force winds were confined to the east of Irene's center over the lower to middle Florida Keys. Irene made its 4th landfall near Cape Sable, Florida and then moved across southeast Florida bringing tropical storm conditions (sustained 39-73 mph winds) and torrential rains (10 to 20 inches). Figure 1 is a visible satellite image of Irene near landfall. During the period while Irene was crossing Florida, sustained hurricane force winds appeared to be limited to squalls offshore the east coast of Florida, as reported by reconnaissance aircraft and indicated by available National Weather Service (NWS) surface observations and Doppler radar.

Irene moved back over water in northern Palm Beach County near Jupiter a little after 0000 UTC on the 16th. It retained hurricane strength and moved on a general northward track paralleling the Florida east coast heading for the Carolinas. An upper-level trough, sweeping eastward across the eastern United States, forced Irene on a fast northeast track. The core of Irene missed the mainland Carolinas but produced very heavy rains inland. It then brushed North Carolina's Outer Banks before moving out to sea.

During a 12-hour period beginning on the evening of the 18th, Irene went through a rapid intensification phase. The central pressure dropped from 978 to 958 mb and the winds increased from 70 to 95 knots. This may be attributable to a combination of a trough interaction and the tropical cyclone moving over very warm water. These two factors together have been known to be the cause of explosive deepening. Hurricane Opal (1995), while located in the Gulf of Mexico, was an example.

Thereafter, Irene continued to accelerate and finally became absorbed by a much larger extratropical low near Newfoundland. The system as a whole became an intense extratropical storm over the North Atlantic.

Irene's track is shown in Figure 2. Table 1 is a listing, at six-hourly intervals, of the best-track position, estimated minimum central pressure and maximum 1-minute surface wind speed.

b. Meteorological Statistics

The best track pressure and wind curves as a function of time are shown in Figure 3 and are primarily based on data provided from numerous reconnaissance missions flown into Irene by U.S. Air Force (Reserve) and NOAA Aircraft Operations Center aircraft. Satellite intensity estimates from the Tropical Analysis and Forecast Branch (TAFB), the Satellite Analysis Branch (SAB) and the Air Force Weather Agency, (AFGWC in figures) were also included in this analysis. Irene was under constant surveillance by three Cuban Weather Radars located at Havana, Isle of Youth and Pinar del Rio, respectively. Radar fixes were relayed to the National Hurricane Center by the Cuban Weather Service and then combined with fixes from Key West radar.

Irene was upgraded to tropical storm status based on a satellite intensity estimate from TAFB and upper-air data from Grand Cayman, which reported 38 knots at the 5,000-feet level and 31 knots near the surface when the tropical cyclone was about 150 n mi from that island. Operationally, Irene was upgraded to hurricane status just before landfall over the Isle of Youth. However, numerous observations from Cuba and a post-analysis of satellite imagery indicate that Irene was most likely a tropical storm while crossing Cuba. Peak winds reported from Cuba were 68 knots at Havana forecast office.

In addition to National Hurricane Service (NWS) reports, observations from the South Florida Water Management District, shown in Table 2, indicate that gusts to hurricane force were experienced near Lake Okeechobee. Based on the Miami WSR-88D (Weather Surveillance Radar -1988 Doppler) signatures, these gusts were likely produced by small-scale meso-cyclone induced downbursts. Four weak tornadoes occurred in Broward and Palm Beach counties.

The rapid intensification of Irene on the 18th off the North Carolina coast was documented by by a reconnaissance plane investigating the hurricane during that period. The report indicated a very small closed eyewall of about 3 n mi in diameter and 114 knot winds at 850-mb. A dropsonde in the eyewall measured 129 knots at the 902-mb level. The wind field was very small and highly asymmetric.

c. Casualty and Damage Statistics

There were 8 indirect casualties associated with Irene. They were five people electrocuted (four in Broward and one in Dade counties). There were three drowning in vehicles driving into canals (one in Palm Beach and two in Broward). In addition, there were three injured by tornadoes in Broward.

Irene caused considerably damage due to flooding in South Florida. In some residential areas. Flooding lasted for a week displacing several hundred people and isolating thousands more. The total losses (agricultural and property) were estimated near $600 millions mostly in Dade, Broward and Palm Beach counties. Additional losses to near $200 millions occurred in the rest of the state of Florida. An estimated 700,000 costumers lost electricity.

d. Forecast and Warning Critique

The average official track errors during Irene's life as a tropical storm or hurricane were 54 n mi at 12 hours (21 cases), 92 n mi at 24 hours (19 cases), 104 n mi at 36 hours (17 cases), 127 n mi at 48 hours (15 cases) and 221 n mi at 72 hours (11 cases). With the exception of the 12- to 24-hour forecasts, these errors are lower than the previous 10-year averages of the official track errors. These 10-year average errors are 48, 89, 128, 164 and 242 n mi for 12, 24 ,36, 48 and 72 hours, respectively.

Table 3 lists the numerous watches and warnings issued. Some residents of southeast Florida expressed displeasure with the NWS forecasts. Although a tropical storm warning was issued for a portion of southeast Florida (meaning sustained winds between 39 and 73 mph) as indicated in Table 3, and torrential rains of 10 to 20 inches with locally higher amounts were forecast, some residents, especially in southeast Florida claimed that such conditions were "unexpected" or "surprising". There is an apparent disconnect between an accurate forecast issued some 36 hours in advance and a public perception of "surprise". The remedial challenge in this case appears to be related to communications and not to the forecast. The combined resources of NWS, the emergency management community and the local media apparently did not adequately convey the message to the public that: (a) track forecasts are not exact; (b) hurricanes are not a point but cover a broad area; and (c) serious effects usually extend for hundreds of miles from the center. Instead, some residents, as well as isolated TV reporting, focused on the center of Irene.

Indeed, the center of Irene was forecast to move along the west coast of Florida as indicated by most of the reliable and state-of-the-art track models shown in Fig. 4a. Instead, the center of Irene kept moving toward the north-northeast. The NHC nevertheless factored uncertainties into its forecast advisories and issued warnings appropriately as shown in Fig. 4b.

Figure 2. Best track positions for Hurricane Irene, 13-19 October, 1999.


Figure 3. (A) Preliminary best track minimum central pressure and (B) maximum sustained wind speed curves for Hurricane Irene. Vertical dashed lines denote landfalls.


Figure 4. (A) Track forecast models and best track of Irene and (B) warnings and watches for Irene at 0000 UTC 14 October, 1999.

Table 1. Preliminary best track, Hurricane Irene, 13-19 October, 1999
Position Pressure
Wind Speed
Lat. (°N)Lon. (°W)
060017.383.3100430tropical depression
120018.583.4100335tropical storm
14/000020.783.6 99955"
060021.083.6 99960"
120021.382.9 99760"
180022.482.4 99560"
180051.045.096880being absorbed by a low
14/1200*21.783.099760western Isle of Youth, Cuba
14/1900*22.782.598660Batabano Cuba
15/1300*24.681.698765Key West Fl.
15/2000*25.381.198770Cape Sable Fl.
18/060034.875.296495brushed the Outer Banks NC.
18/075635.474.4958 95minimum pressure

*landfall points

Table 2. Hurricane Irene selected surface observations, October 1999.
Maximum surface wind speed
Location Pressure
gust (kts)
(storm total)
Havana Casablanca   6814/2020  4.80
Playa Giron        10.7
Topes de Collantes        8.70
Jaguey Grande       8.70
Jovellanos       7.10
Melena del Sur       7.20
Union de Reyes       7.10
Batabano       6.40
Guines       6.20
Cienfuegos       5.50
Nueva Gerona       5.40
Colon       4.80
Big Pine Key  698915/0000   
Sombrero Key C-MAN990.5 15/1700576915/1530   
Molasses Reef C-MAN991.5 15/2100536415/2020   
Long Key C-MAN988.7 15/2000506115/2000   
Sand Key C-MAN987.0 15/1200435715/0610   
Dry Tortugas C-MAN  415115/0850   
Key West Intl. Airp.987.615/1010384715/0518  8.85
Marathon Airp.989.6      7.18
Key West   384715/16301.5  
Vaca Key    15/08002.3  
Tavernier       9.82
Fowey Rock Lt C-MAN991.915/2300577315/2200   
Miami Beach  52 15/1950  9.49
Tamiami Airp.990.915/2353456015/2130   
Lake Worth C-MAN 16/0300445316/0300   
Homestad AF990.915/225742 74*15/1809  14.57
Miami Int. Airp.990.115/2256416115/2008  10.99
Pompano Beach Airp. 991.016/0253405015/2202   
Ft. Lauderdale Exec. Airp.909.516/0153405015/2048   
Ft. Lauderdale Int. Airp.990.916/0123     13.38
Opalocka Airp. 989.916/0053394915/2257   
West Palm Beach Airp. 990.916/0453375316/0211  10.88
North Perry Airp. 15/2029375015/2029   
Winter Heaven1003.116/1927 4215/2033   
Fort Myers (FMY)1000.115/2328 3816/0228   
Fort Myers (RSW)1000.016/0017 3815/2305   
Bunnel (X47)   3816/2222   
St. Augustine Airp. (SGJ) 997.717/----- 4717/0020  2.03
Mayport Navy Base (NRB) 996.817/0820 4817/0302  1.62
Craig Field (CRG)    3817/0311  2.90
Orlando (MCO)1000.216/2053334216/1553  1.70
Daytona Beach (DAB) 997.216/2353364916/1853  3.87
Melbourne ASOS993.916/1650475916/1323   
Melbourne (MLB)  405816/1050  5.36
Patrick AFB (COF) unofficial ASOS   505916/1048   
Vero Beach (VRB)  396216/0910   
Ft. Pierce989.116/1053374516/0753   
Buoy 41009 984.815/0900456016/1100   
Bunnell X47   3816/2222   
Flagler Beach Vol. Fire Dptm.998.716/unkn     2.48
King's Bay Platform    5117/1200   
St. Simons Island Ga.997.317/0907 4717/03031.9  
Fernandina Beach     2.9  
South Carolina
Gray Reef Buoy (41008)    5117/0800   
Charleston International Airp.       3.09
Johns Island       6.22
Charleston City Office       4.23
North Carolina
Frying Pan Shoals Tower   496117/2250   
Diamond Shoals (DSLN7)983.018/0200454917/2250   
Cape Lookout (CLKN7)989.018/0100 4018/0303   
Duck Pier (DUCN7)994.018/0700404917/0300   
Frisco (HSE)986.018/0139334117/2215  3.53
Beaufort (MRH)   3518/0326  3.14
Cherry Point (NKT)   3918/0210  4.68
Wilmington (ILM)994.618/0202     2.86
Cape Fear       5.50
Elizabethtown       6.69
New Bern        6.39
Snowhill        5.50
Ernul       11.00
Norfolk997.318/0552 3518/1152  7.34
Oceana NAS (NTU)996.618/0756 4218/1056  7.47
Newport News (PHF)998.618/0654 3418/1054   
Wallops Island998.518/0754 3418/0754   
Chesapeake       12.00
Porthmouth       10.02
Courtland       7.10
NWS CO-OP Observer Rainfall
Ft. Lauderdale       13.38
Hollywood       13.13
Homestead General Airp.       12.03
North Dade County       8.35
NWS Unofficial amounts/readings
Cooper City       15.43
West Pembroke Pines       14.85
Saga Bay       13.89
South Miami       13.50
Boyton beach       17.45
Plantation       11.70
Tamiami Trail / Krome Ave.        11.60
Everglades / US 27       10.38
Lauderdale Lakes       9.73
El Portal       9.53
Pompano Beach       9.34
Lake Worth  4453   9.17
Biscayne Bay/320 St.       8.95
Weston       8.79
North Miami Beach       8.25
West Boca Raton       7.80
Opa-locka       7.60
Sawgrass Mills       7.41
North Palm Beach       7.55
Leisure City       7.08
Jupiter         6.44
South Florida Water Management
Belle Glade   8116/230   
20-25 miles SW of Clewinston    7915/2226   
Lake Okeechobee (middle)   7016/0522   
25 mi west of Palm Beach   5915/0055   
west of Lake Ockeechobee   5615/2239   
35 mi west of Boca Raton   5015/2314   
Krome Ave (near Homestead)   5015/2003   
La Belle   4315/1712   
Kissimee   4016/1510   

aASOS and C-MAN are 2 min; buoys are 8 min.
bDate/time is for sustained wind when both sustained and gust are listed.
cStorm surge is water height above normal astronomical tide level.
dStorm tide is water height above National Geodetic Vertical Datum (1929 mean sea level).
* This type of anemometer has been unreliable in the past.

Table 3. Tropical Cyclone watch and warning summary for Hurricane Irene
Action Location
13/1500Tropical Storm WarningCayman Islands.
13/1500Hurricane WatchCuban provinces of Pinar del Río, Havana, Ciudad Havana and Isle of Youth.
13/2100Hurricane WarningCuban provinces of Pinar del Río, Havana, Ciudad Havana, Matanzas and Isle of Youth.
13/2100Hurricane WatchLower and Middle Florida Keys, West of Craig Key including Dry Tortugas.
14/1200Tropical Storm WarningDiscontinued for Cayman Islands.
14/1500Hurricane WarningDry Tortugas.
14/1500Hurricane WatchWest coast of Florida from Flamingo to Boca Grande.
14/1500Tropical Storm WarningLower and Middle Florida Keys, West of Craig Key.
14/2100Hurricane WarningSouth of Florida City around the Florida peninsula to Boca Grande, including all Florida Keys and Dry Tortugas
14/2100Tropical Storm Warning and Hurricane WatchFrom Florida City to Jupiter Inlet and Lake Okeechobee.
14/2100Hurricane WatchNorth of Boca Grande to Longboat Key.
15/0300Hurricane WarningExtended Northward along Florida West Coast to Anclote Keys.
15/0300Hurricane WatchFrom North of Anclote Keys to Yankeetown
15/0300Hurricane WarningDiscontinued for Cuban provinces of Pinar del Río, Matanzas and Isle of Youth.
15/0900Tropical Storm Warning and Hurricane WatchExtended Northward along Florida East coast to South of Flagler Beach.
15/0900Hurricane WarningDiscontinued for all Cuban provinces
15/1200Tropical Storm WatchBimini, Grand Bahama and Abaco Islands in Bahamas.
15/2100Tropical Storm Warning (Downgraded from Hurricane Warning)North of Bonita Beach to the Anclote Keys.
15/2100Tropical Storm WarningExtended Northward from Florida City to Fernandina Beach and Lake Okeechobee.
15/2100Tropical Storm WatchNorth of Fernandina Beach to Savannah, Georgia.
15/2100Hurricane WatchAll discontinued.
16/0300All WarningsDiscontinued South of Florida City, the Florida Keys, the Dry Tortugas and the Florida West coast.
16/0300Tropical Storm WatchExtended Northward from North of Fernandina Beach to Little River Inlet, South Carolina.
16/0300Tropical Storm WatchDiscontinued for Abaco Islands, Bahamas.
16/0900Tropical Storm WarningExtended North of Fernandina Beach, Florida to Edisto Beach, South Carolina.
16/0900Hurricane WatchNorth of Edisto Beach to Cape Hatteras, North Carolina including Pamlico Sound.
16/0900Tropical Storm WarningDiscontinued along the Florida East coast from Jupiter Inlet Southward, including Lake Okeechobee.
16/1500Hurricane WarningFrom Edisto Beach, South Carolina to Surf City, North Carolina.
16/1500Tropical Storm WatchDiscontinued for Bimini and Grand Bahama Island.
16/2100Hurricane WarningExpanded from Savannah, Georgia to Cape Hatteras, North Carolina including Pamlico Sound
16/2100Hurricane WatchNorth of Cape Hatteras to the North Carolina/Virginia border, including Albemarle Sound.
16/2100Tropical Storm WarningDiscontinued South of Vero Beach, Florida.
17/0300Tropical Storm Warning(Replacing Hurricane Watch)North of Cape Hatteras to the North Carolina/Virginia border, including Albemarle Sound.
17/0300Tropical Storm WarningDiscontinued South of New Smyrna Beach, Florida.
17/0900Tropical Storm WarningDiscontinued South of St. Augustine Beach, Florida.
17/1500Tropical Storm WarningDiscontinued South of Fernandina Beach, Florida.
17/2100All WarningsDiscontinued from Edisto Beach, South Carolina Southward.
18/0000Hurricane WarningDiscontinued South of Santee River, South Carolina.
18/0300All WarningsDiscontinued from Surf City, North Carolina Southward.
18/0300Tropical Storm Warning (downgraded from Hurricane Warning)North of Surf City, North Carolina to North Carolina/Virginia border, including Pamlico and Albemarle Sounds.
18/0600All WarningsDiscontinued from Bogue Inlet, North Carolina Southward.
18/0900All WarningsDiscontinued everywhere they had still been in effect.

*Tropical Cyclone watches and warnings are issued by respectively countries in coordination with the National Hurricane Center.


Last updated January 28, 2000