Tropical Cyclone Report

Hurricane Isidore

Hurricane Isidore was a slow-moving tropical cyclone that hit western Cuba as a category 1 hurricane (on the Saffir-Simpson Hurricane Scale) and the northern Yucatan Peninsula as a category 3 hurricane. It made landfall on the Louisiana coast as a strong tropical storm.

a. Synoptic History

A tropical wave moved off the coast of Africa on 9 September accompanied by a large area of thunderstorms. The convective activity decreased significantly as the system moved toward the west-southwest during the next few days, but the wave maintained a good low-cloud signature and cyclonic rotation. As the wave approached 50 West, the shower activity began to increase and an upper-level anticyclone became evident over the system. By 1800 UTC 14 September, there was enough convection and rotation to classify the system as a tropical depression as it approached Trinidad and the northern coast of Venezuela. The depression moved west-northwestward and its development was halted by its interaction with land. By 1800 UTC 15 September, the system had degenerated into a tropical wave in the eastern Caribbean Sea. However, as the wave entered the western Caribbean Sea, it redeveloped a closed circulation and regained tropical depression status at 1200 UTC 17 September, about 120 n mi south of Kingston, Jamaica.

The depression became Tropical Storm Isidore around 0600 UTC 18 September, and, embedded within a weak steering current, the tropical cyclone moved very slowly toward the northwest, passing just west of Jamaica. Isidore then moved very slowly toward the west-northwest across the Cayman Islands and became a hurricane at 1800 UTC 19 September. Its winds reached 90 knots around 0600 UTC 20 September as it was nearing the southwest coast of the Isle of Youth, Cuba. Although the minimum pressure continued to drop, Isidore's winds decreased a little bit and the hurricane made landfall near Cabo Frances in western Cuba at 2100 UTC 20 September with maximum winds of 75 knots. For more than 12 hours, Isidore relentlessly pounded western Cuba. The hurricane then moved west and southwestward toward the Yucatan Peninsula. Isidore re-strengthened and reached its maximum intensity of 110 knots at 1800 UTC 21 September. However, its minimum central pressure of 934 mb occurred at 1200 UTC 22 September, just before landfall near Puerto Telchac on the north coast of Yucatan.

Isidore meandered for 24 to 36 hours over northern Yucatan and weakened to a minimal tropical storm. It then moved northward over the Gulf of Mexico where the circulation expanded but the cyclone never redeveloped an inner core of strong winds. Isidore made landfall with winds of 55 knots and a minimum pressure of 984 mb just west of Grand Isle, Louisiana at 0600 UTC 26 September. Once it moved inland, Isidore weakened to a tropical depression and moved north-northeastward across the southeastern United States, producing torrential rains. It became an extratropical storm over southwestern Pennsylvania at 1800 UTC 27 September, and was then absorbed into a frontal zone.

The "best track" chart of the tropical cyclone's path is given in Figure 1a and Figure 1b, with the wind and pressure histories shown in Figure 2and Figure 3, respectively. The best track positions and intensities are listed in Table 1.

b. Meteorological Statistics

Observations in Isidore (Figure 2 and Figure 3) include satellite-based Dvorak technique intensity estimates from the Tropical Analysis and Forecast Branch (TAFB), the Satellite Analysis Branch (SAB) and the U. S. Air Force Weather Agency (AFWA), as well as flight-level and dropwindsonde observations from flights of the 53^rd Weather Reconnaissance Squadron of the U. S. Air Force Reserve Command and the NOAA hurricane reconnaissance plane. Fixes from various Cuban radars, as well as data from the Cancun radar received at the NHC in real time were very useful in tracking Isidore. Data from the NOAA high altitude jet was used to analyze the environment surrounding the hurricane and was ingested by numerical models.

Isidore was upgraded to tropical depression status based on a fix provided by a reconnaissance plane. It was a report of a poorly defined center of 1009 mb with 20 to 25 knot southwesterly winds at 1500 feet around 1800 UTC 14 September. It was downgraded to a tropical wave in the eastern Caribbean Sea the next day, when a reconnaissance plane could not find a closed circulation.

Isidore moved very close to the south of Cayman Brac, which reported sustained winds of 42 knots with gusts to 61 knots at 0325 UTC 19 September. During the time Isidore was moving nearby the Isle of Youth, the eye contracted to 8 n mi, and based on data from a dropsonde in the eyewall, surface winds were near 90 knots. Thereafter, there was a slight weakening as suggested by data from a reconnaissance aircraft. In fact, the official best track over Cuba was adjusted with data provided by the Cuban Weather Service. Surface observations from Cuba and a post-analysis of aircraft and dropsonde data suggest that Isidore crossed Cuba with 75-knot winds and not with the 85 knots indicated operationally. The minimum pressure measured in western Cuba was 970 mb at Isabel Rubio, and that station experienced gusts to 75 knots at 2140 UTC 20 September and about 554 mm (21.7 in) of rain. Several locations in the area reported the calm of the eye. There was a strong storm surge along the south coast of Cuba in Playa Cajio, south of Habana and in Ensenada de Cortes, Pinar del Rio. When Isidore was already in the Gulf of Mexico, rainbands over Cuba produced a wind gust of 86 knots in an isolated tornado in the town of Candelaria at 1600 UTC 23 September.

Isidore's peak intensity of 110 knots at 1800 UTC 21 September, was a compromised between adjusted aircraft flight-level winds and satellite estimates. Although the winds remained unchanged, the central pressure continued to drop to a minimum of 934 mb at 1200 UTC 22 September. At this time, the cloud pattern looked the best one imagery and the three satellite agencies reported T-numbers of 6.5 on the Dvorak scale, corresponding to 127 knots. However, aircraft data did not support such intensity.

The maximum winds reported by a station in Yucatan were gusts to 70 knots, with a minimum pressure of 969.9 mb at Merida around 2350 UTC 22 September as the western eyewall moved through the area. Figure 4a and Figure 4b are radar images showing the eye of Isidore making landfall in western Cuba and Yucatan, respectively.

Later, when a weakened Isidore was heading for Louisiana, it reached 55-knot winds based on data from the "Deepwater Pathfinder", which reported sustained winds of 56 knots with gusts to 71 knots and 20 ft waves at 1743 UTC 27 September. Because Isidore was a large tropical cyclone, there were numerous observations from ships of tropical storm force winds. Some of these observations are given in Table 2

The Belle Chase Naval Air Station in Louisiana experienced northeast winds of 50 knots with gusts 60 knots at 0155 UTC 26 September. This is the highest wind reported by any station as Isidore made landfall in the Louisiana coast. The highest storm surge reported along the U.S. coast was 8.3 feet and occurred at Rigoletes, Louisiana and at Gulfport Harbor, Mississippi. Additional selected surface observations from land stations and data buoys are given in Table 3 and Table 4.

c. Casualty and Damage Statistics

Press reports indicate that there were 2 indirect deaths attributable to Isidore in Merida, Mexico. One was electrocuted by a downed power line, another died in a weather-related car crash. Four direct and one indirect deaths occurred in the United States. One was a marine fatality drowning from a rip current near Port Fourchon, LA on 22 September when Isidore was still over Yucatan, another one was a drowning in a vehicle parked near a casino in Mississippi when storm surge inundated the parking lot. A third died when a tree fell across his car in eastern Mississippi, and the forth one died after driving into 10 feet of water in Clarksville, Tennessee. The indirect death occurred in Mississippi when a man suffered from a cardiac arrest and could not be reached by rescuers due to floodwaters.

Damage from Isidore in Jamaica was mainly related to torrential rains. Western Cuba and Yucatan were severely damaged by the hurricane primarily the agriculture and cattle industry. According to Tropical Cyclone Reports from the weather services of Cuba and Mexico, numerous houses and power lines were damaged by wind.

In the United States, the Property Claim Services Division of the Insurance Services Office reports that insured losses due to Isidore totaled 165 million dollars. Using a two to one factor for insured to overall damage gives a total damage estimate of $330 million. Most of the damage occurred in Louisiana.

d. Forecast and Warning Critique

Average official track errors (with the number of cases in parentheses) for Isidore were 32 (31), 55 (31), 73 (29), 101 (27), and 177 (23) n mi for the 12, 24, 36, 48, and 72 h forecasts, respectively. These errors are lower than the average official track errors for the 10-yr period 1992-2001 of 43, 81, 115, 148, and 222, respectively. Table 5 which includes the track model errors indicates that the NCEP global model (GFS) performed remarkably well with errors lower than the official forecast errors. Furthermore, the U.S. Navy global model (NGPS), which has been upgraded this hurricane season, performed even better than the GFS. These two global models captured the anomalous southward track of Isidore over Yucatan. This uncommon southward track was not taken into consideration in the official forecast and may have been the cause of errors larger than these two models.

Average official intensity errors were 9, 16, 22, 30, and 46 kt for the 12, 24, 36, 48, and 72 h forecasts, respectively. These errors are higher than the average official intensity errors over the 10-yr period 1992-2001 which are: 7, 11, 14, 16, and 19 kt, respectively. Because the official track forecast kept Isidore over water a continued strengthening was indicated. Instead, Isidore moved over Yucatan and weakened, causing large intensity errors. Tthe official intensity forecasts were correct in not predicting a rapid intensification after Isidore moved back over the Gulf of Mexico and headed for Louisiana.

Due to Isidore's track near many land areas, a large number of watches and warnings were issued and coordinated with various countries from the Caribbean region. They are summarized in Table 6.

Figure 1a: Best track positions for Isidore, 14- 27 September 2002. Track after 0000 UTC 27 September is based on analyses from NOAA Hydrometeorological Prediction Center.

Figure 1b: Best track positions for Isidore, 14- 27 September 2002 denoting the landfall points.

Figure 2: Selected wind observations and best track maximum sustained surface wind speed curve for Isidore, 14-27 September 2002. Aircraft observations have been adjusted for elevation using 90%, 80%, and 80% reduction factors for observations from 700 mb, 850 mb, and 1500 ft, respectively. Dropwindsonde observations include actual 10 m winds (sfc), as well as surface estimates derived from the mean wind over the lowest 150 m of the wind sounding (LLM), and from the sounding boundary layer mean (MBL).

Figure 3: Selected pressure observations and best track minimum central pressure curve for Isidore, 14-27 September,

Figure 4a: Image from Havana radar provided by the Instituto de Meteorologia, Cuba during the time Isidore was making landfall in western Cuba

Figure 4b: Image from Cancun radar provided by the Servicio Meterorologico Nacional of Mexico during the time Isidore was making landfall near Puerto Telchac, Yucatan.