Tropical Cyclone Report

Hurricane Claudette

Hurricane Claudette made landfall in Texas as a Category 1 hurricane on the Saffir-Simpson Hurricane Scale and on the northeastern Yucatan Peninsula of Mexico as a tropical storm. It maintained tropical storm status for more than 24 hours after landfall in Texas.

a. Synoptic History

Claudette formed from a tropical wave that moved westward from the coast of Africa on 1 July. The wave first showed signs of convective organization on 6 July. By 7 July satellite imagery indicated sufficient organization to possibly classify the system as a tropical depression near the Windward Islands. However, the wave was moving westward at 20-25 kt at the time, and neither surface observations nor an investigation flight by the Air Force Reserve Hurricane Hunters indicated that the system had a closed circulation. The aircraft did report flight-level winds of tropical-storm force north of the vorticity maximum that passed near Barbados and St. Lucia.

The wave continued rapidly westward with a further increase in organization. Satellite intensity estimates suggested the system was near tropical storm strength by 1500 UTC 8 July. However, a second investigative flight could not find a closed center at that time. Finally, near 1800 UTC the plane found a small area of southwesterly winds and a pressure of 1006 mb. The wave became Tropical Storm Claudette at that time. The "best track" chart of the tropical cyclone's path is given in Figure 1, with the wind and pressure histories shown in Figure 2 and Figure 3, respectively. The best track positions and intensities are listed in Table 1.

Claudette continued quickly westward through 9 July, then it turned northwestward with some deceleration on the next day. A continued northwestward motion brought Claudette to its first landfall, on the northeastern Yucatan Peninsula of Mexico near 1000 UTC 11 July.

During this period, Claudette underwent two notable fluctuations in intensity. The first occurred around 0300-0400 UTC 9 July, when flight-level winds reported by an Air Force Reserve Hurricane Hunter aircraft northeast of the center suggested that Claudette might have reached hurricane strength. Subsequent data shortly thereafter showed much lower winds, and it is estimated that Claudette did not become a hurricane at that time.

A second noteworthy sequence of intensity changes occurred on 10 July. An increase in convective organization and strengthening began between 0000-0600 UTC. A Hurricane Hunter flight near 1200 UTC reported a 10-n mi wide eye (also apparent in visible and microwave satellite imagery), along with flight-level winds, dropsonde winds, and pressures that indicated Claudette had become a hurricane. The cyclone maintained hurricane intensity through 1600 UTC. The central core then completely collapsed during the next two hours. The aircraft could not fix the center at 1800 UTC due to the poor definition of both the wind field and the convective pattern. While it is possible the aircraft did not sample the maximum winds on the attempted 1800 UTC penetration, rapid weakening was clearly underway.

Claudette then proceeded to become very disorganized. The center became broad and poorly defined, and multiple low-level centers were seen several times in satellite imagery between 1800 UTC 10 July and 0000 UTC 12 July. The convection was displaced well to the north and east by southwesterly shear, with aircraft and ship data indicating tropical storm-force winds in the convective area. Much of the motion during this time may be due to reformation of the center caused by convective bursts. The best track shows 45-50 kt winds during this period, but there is much greater than normal uncertainty about both the winds and the central pressure due to the disorganized nature of the storm.

The storm moved northwestward into the southern Gulf of Mexico on 11 July. A north-northwestward jog occurred on 12 July while Claudette became a little better organized. The storm meandered erratically northwestward on 13 July, then turned northward later that day. These track changes were likely due to a combination of 1) weakening of a mid/upper-level ridge along the northern Gulf coast caused by a developing trough over the eastern United States, and 2) reformation of the center caused by strong but asymmetric convection to the northeast. This change in motion was accompanied by some decrease in the shear, and while the center remained mostly exposed, Claudette slowly and unsteadily strengthened on 13 July.

A building deep-layer ridge over the western United States and the western Gulf coast states forced Claudette to gradually turn west-northwestward late on 14 July. This brought the storm to an area of lighter shear, which allowed an eyewall to form and for Claudette to again become a hurricane at 0600 UTC 15 July. A faster west-northwestward motion brought the center of Claudette to the Texas coast at Matagorda Island (just east of Port O'Connor) at 1530 UTC that day. Strengthening continued up to landfall, with estimated maximum winds increasing to 80 kt and the central pressure falling to 979 mb.

Claudette turned westward just after landfall and weakened to a tropical storm at 0000 UTC 16 July. It then turned west-northwestward again while moving into northern Mexico later that day. This motion would continue until dissipation. Claudette was slow to lose organization, as the radar and satellite presentations of its structure remained distinct for more than 24 hr after landfall. Surface data indicates the system maintained tropical storm strength until 0000 UTC 17 July. The low-level circulation dissipated over the mountains of northwestern Mexico later that day. However, the mid- and upper-level moisture and vorticity continued west-northwestward, eventually crossing southern California into the Pacific.

b. Meteorological Statistics

Observations in Claudette (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 Aircraft Operations Center. Surface data from ships and land stations are included as well (Table 2 and Table 3). Microwave data from the TRMM, DMSP, and NOAA satellites, and data from the WSR-88D Doppler radars in Houston, Corpus Christi, and Del Rio, Texas also played a significant role in determining the best track of Claudette.

The Air Force Hurricane Hunters made 52 fixes during Claudette's life, while the NOAA Hurricane Hunters made 4. The maximum flight-level winds observed by the aircraft were 85 kt at 0334 UTC 9 July (1500 ft) and at 1517 UTC 15 July (700 mb) - the latter as the eye of Claudette was crossing the Texas coast. Global Positioning System (GPS) dropsondes deployed by the aircraft reported surface winds of 73 kt at 1526 UTC 10 July and 70 kt at 1516 UTC 15 July. The latter dropsonde recorded a 96 kt wind at the 976 mb level.

At the time of the first occurrence of 85 kt winds on 9 July, the aircraft reported a central pressure of 1001 mb. Two hours later, a pass through the same part of the storm at 850 mb showed winds of only 56 kt. Based on this, it is estimated that Claudette remained a tropical storm and the best track will show 60 kt at 0600 UTC 9 July. However, there is greater than normal uncertainty about the value.

The 73-kt dropsonde surface winds on 10 July occurred during Claudette's short-lived intensification into a hurricane over the northwestern Caribbean. The aircraft reported a minimum pressure of 988 mb at 1201 UTC, then reported 76-kt flight-level winds at 700 mb at 1526 UTC. During the aborted attempt to fix the center two hours later, the maximum 700- mb winds were only 51 kt. The aircraft reported a minimum pressure of 1005 mb at the time, but this was likely not at the center and the actual central pressure is speculative. However, the weather officer on the aircraft reported that the pressure near the center was about 10 mb higher that 2 h earlier.

Aircraft and surface data indicate hurricane conditions occurred over portions of the middle Texas coast. The maximum sustained winds reported by an official observing site was a 10-min average of 65 kt at the Remote Automated Weather Stations (RAWS) site on Matagorda Island, Texas (Table 3). The Texas Coastal Ocean Observation Network (TCOON) station at Port O'Connor reported a 6-min average sustained wind 62 kt with a gust to 78 kt in the western eyewall. Victoria, Texas, reported 54-kt sustained winds with a gust to 72 kt, although that data is incomplete due to a power failure. Tropical storm conditions occurred along much of the middle and upper Texas coast and extended well inland across southern Texas. Cotulla, Texas, reported sustained winds of 36 kt with a gust to 46 kt at 0246 UTC 16 July, while Del Rio, Texas, reported a gust to 47 kt.

Tropical-storm force winds also occurred well inland over portions of southwestern Texas, including 38-kt sustained winds with a gust to 50 kt at the Terrell County airport at 1658 UTC 16 July. While this station is at an elevation of 2300 ft, there is no evidence that mountainous terrain enhanced the winds, and this report is the basis for keeping Claudette a tropical storm through 1800 UTC 16 July. Other reports of tropical storm wind gusts occurred at Mt. Locke in the Davis Mountains, and at Guadalupe Pass and The Bowl in the Guadalupe Mountains. These winds were likely enhanced by mountainous terrain.

Tropical storm conditions likely occurred over portions of the northeastern Yucatan Peninsula, but there were no reports of tropical-storm winds from that area. Winds gusted to tropical-storm force at Montego Bay, Jamaica. Winds also gusted to tropical-storm force on St. Lucia during the passage of the pre-Claudette tropical wave.

Many unofficial observations were received from the landfall area, with a selection included in Table 3. A storm chaser (Tony Whitener) in Port O'Connor reported 83-kt sustained winds with a gust to 93 kt measured at the top of a vehicle with good exposure. While this observation is included in Table 3, it is notable that the winds are 15-20 kt higher than the nearby TCOON station and thus appear unrepresentative. A report from Seadrift indicated 84-kt sustained winds with a gust to 96 kt. However, an inspection of the site by National Weather Service (NWS) personnel showed that the anemometer placement may have caused funneling of the winds across the instrument. Thus, the report is not included in Table 3.

The 84-kt and 83-kt unofficial observations suggest the possibility that Claudette strengthened to a Category 2 hurricane as it was making landfall. This was not supported by the aircraft data, which suggest maximum sustained winds of 75-80 kt as the eye crossed the coast. Data from the NWS WSR-88D Doppler radars indicated winds of 95-105 kt between 5,000-10,000 ft in the northwest eyewall after Claudette made landfall. It is uncertain how to convert these winds to sustained surface winds over land. However, reduction factors derived from GPS dropsonde data over water suggest 85-90 kt sustained surface winds. A further reduction for land friction would reduce the radar winds to at or below the 75-80 kt range suggested by the aircraft data.

Damage surveys were conducted by the staffs of NWS forecast offices in Corpus Christi and Houston in order to help define the surface winds at landfall. These surveys concluded the damage was consistent with Category 1 sustained winds. Unpublished information from a damage survey by a wind engineering expert with the commercial engineering firm Haag Engineering supports this determination.

Based on the surveys, the data, and uncertainties (i.e., the possibility that the aircraft did not sample the strongest winds), the landfall intensity of Claudette is estimated to be 80 kt - at the high end of Category 1 on the Saffir-Simpson Hurricane Scale.

Several ships encountered Claudette during its life (Table 2). The most significant observations included: 1) the Explorer of the Seas, which reported 49-kt sustained winds in the Yucatan Channel at 0356 UTC 11 July; 2) the Rhapsody of the Seas, which reported 56-kt sustained winds at 0600 UTC 14 July; 3) the James N. Sullivan, which reported 55 kt winds at 1500 UTC 14 July; and 4) the Galveston Bay, which reported 54-kt sustained winds at 2100 UTC 14 July. Several oil rigs in the northwestern Gulf of Mexico reported hurricane-force winds 100-200 ft above the surface (Table 3). Not included in Table 3 is a wind gust of 119 kt reported at the rig C337 which appears unrealistic.

The lowest pressure reported by reconnaissance aircraft was 979 mb just before landfall at 1414 UTC 15 July. The lowest observed pressure on land was 980.0 mb observed by the Port O'Connor storm chaser when the eye passed over.

Storm-surge flooding of 3-6 ft above normal tide levels occurred near where the eye of Claudette made landfall. Storm tides (storm surge plus astronomical tide) of 6-9 ft were measured in the Galveston-Freeport area (Table 3). Tides were 1-2 ft above normal as far north as the southwestern Louisiana coast and as far south as the Baffin Bay, Texas area.

Claudette moved quickly westward after landfall, which limited rainfall totals. The highest storm-total rainfall was 6.5 in four miles south-southeast of Tilden, Texas (Table 3a), and there are other reports of 3-6 in amounts along the storm track. NWS WSR-88D radar data estimates that as much as 8 in may have fallen in some areas. These rains caused minor flooding in southern Texas and some flash flooding in southwestern Texas. Rainfalls of 1-3 in also occurred over portions of the Yucatan Peninsula and the Cayman Islands, with 3.22 in reported in Cancun.

Two tornadoes were reported during Claudette. One was an F1 that damaged several buildings in Palacios, Texas. The other touched down in Port Lavaca, Texas, causing damage to some homes.

c. Casualty and Damage Statistics

Claudette is responsible for one direct and two indirect deaths. The direct death was a 13-year old boy crushed by a falling tree in Jourdanton, Texas. The first indirect death was a 33-year old woman who was hit by a falling limb after the storm was over. The second indirect death was at Navarre Beach, Florida when a 71-yr old man died after being pulled from surf generated by Claudette. Press reports suggest the man suffered a heart attack while swimming.

The American Insurance Services Group reported that Claudette caused $90 million in damage to insured property in the United States. The total damage estimate is twice this or $180 million. The damage includes five stations of the TCOON and Texas Automated Buoy System (TABS) networks destroyed by the hurricane. No significant damage was reported from Mexico, the Cayman Islands, or Jamaica. Minor damage was reported in St. Lucia from the pre-Claudette tropical wave.

d. Forecast and Warning Critique

The track forecast errors for Claudette were generally small compared to normal. Average official track errors (with the number of cases in parentheses) were 36 (30), 57 (30), 89 (28), 117 (26), 140 (22), 154 (18), and 154 (14) n mi for the 12, 24, 36, 48, 72, 96, and 120 h forecasts, respectively¹. These errors are much lower than the average official track errors for the 10-yr period 1993-2002² (45, 81, 116, 150, 225, 282, and 374 n mi, respectively) (Table 4). These errors are also much lower than those of the Climatology-Persistence methods, indicating the track forecasts had considerable skill. The track forecast philosophy was quite good overall. From Claudette's beginnings, the storm was forecast to move westward to the western Caribbean, northwestward into the Gulf of Mexico, and then westward toward the western Gulf coast. However, the extent of the northward motion over the Gulf was not fully anticipated, nor was the westward acceleration as Claudette approached the western Gulf coast.

The intensity forecast errors for Claudette were also well below the long-term means. Average official intensity errors were 5, 7, 7, 9, 9, 8, and 8 kt for the 12, 24, 36, 48, 72, 96, and 120 h forecasts, respectively. For comparison, the average official intensity errors over the 10-yr period 1993-2002 are 6, 10, 13, 15, 19, 21 , and 22 kt, respectively. The intensity forecast errors were lower than those of the Statistical Hurricane Intensity Forecast System (8, 11, 14, 17, 22, 19, and 16 kt for the 12, 24, 36, 48, 72, 96, and 120 h forecasts, respectively), indicating that the intensity forecasts had considerable skill. The intensity forecasts were generally correct in anticipating that southwesterly vertical shear would slow development until Claudette was near the western Gulf coast. However, significant overforecasts occurred when Claudette briefly reached hurricane intensity on 10 July, as the intensity forecasts at the time incorrectly called for continued strengthening. Additionally, the amount of intensification near the Texas coast was underforecast by 5-10 kt.

Table 5 lists the watches and warnings associated with Claudette. Hurricane warnings for the Texas coast were issued about 24 h before the center made landfall. A hurricane watch was issued for the area from Port O'Connor southward about 48 h before Claudette made landfall, while a hurricane watch was issued for the remainder of the landfall area about 30 h before the center made landfall. The first tropical storm warnings for the northeastern Yucatan Peninsula were issued 37 h before the center made landfall. Hurricane warnings issued on 10 July for the Yucatan Peninsula proved unnecessary, because Claudette weakened rapidly after being a hurricane for a few hours.

¹ All forecast verifications in this report include the depression stage of the cyclone. National Hurricane Center verifications presented in these reports prior to 2003 did not include the depression stage.

² Errors given for the 96 and 120 h periods are averages over the two-year period 2001-2002.

Acknowledgements

Much of the data from the affected area was provided by the NWS Weather Forecast Offices at Houston, Corpus Christi, San Antonio, and Midland, Texas, and Lake Charles, Louisiana. NOS data were provided by the NOAA National Ocean Service. RAWS data were provided by the National Interagency Fire Center. TCOON data were provided by the Division of Nearshore Research at Texas A&M University-Corpus Christi. TABS data were provided by the Geochemical and Environmental Research Group of Texas A&M University. Other data were provided by the NOAA Forecast Systems Laboratory and the Weather Underground web site. Data from Mexico, the Cayman Islands, and Jamaica were provided by the meteorological services of those countries.

Figure 1: Best track positions for Hurricane Claudette, 8-17 July 2003.

Figure 2: Selected wind observations and best track maximum sustained surface wind speed curve for Hurricane Claudette, 8-17 July 2003. 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 Hurricane Claudette, 8-17 July 2003.