Preliminary Report
Hurricane Hortense
03 - 16 September 1996

1996 PRELIMINARY REPORTS

Tropical Storm Arthur (TS)
Hurricane Bertha (3)
Hurricane Cesar (1)
Hurricane Dolly (1)
Hurricane Edouard (4)
Hurricane Fran (3)
Tropical Storm Gustav (TS)
Hurricane Hortense (4)
Hurricane Isidore (3)
Tropical Storm Josephine (TS)
Tropical Storm Kyle (TS)
Hurricane Lili (3)
Hurricane Marco (1)

Hortense became the second category four hurricane and the fourth category three hurricane on the Saffir-Simpson Hurricane Scale (SSHS) of the season. Hortense was a wet hurricane and most of the damage was caused by its accompanying torrential rains. Hortense crossed the southwestern tip of Puerto Rico and the eastern top of the Dominican Republic as a category one hurricane and the associated floods killed at least 21 people. Hortense moved northward over the western Atlantic and crossed Nova Scotia as a weakening hurricane.

 

a. Synoptic History

A broad area of low-pressure associated with a tropical wave crossed Dakar, Africa on 30 August. The Dakar vertical-time section during that period showed a well marked cyclonic wind shift below 700 mb and a 63-mph easterly jet at 550 mb. Surface observations indicated that a 1005 mb low associated with the wave moved just south of the Cape Verde Islands on the 31st. Although the system had a well defined low- to middle- level circulation, satellite images indicated that the deep convection was minimal. The low-pressure area continued moving westward and during 3 September, it crossed an array of NOAA drifting buoys. Data from these buoys helped to determine that the system had become a tropical depression at 1200 UTC 3 September.

The depression continued almost due westward around the periphery of a strong high pressure ridge with no significant change in strength. Satellite images suggest that for the next couple of days, deep convection was rather intermittent and not well organized. In fact, on 6 September, the first reconnaissance flight into the system found a broad circulation and only a few squalls. As the depression approached the Lesser Antilles, upper- level winds became more favorable for strengthening and satellite images showed an increase in deep, organized convection. It is estimated that the depression reached tropical storm status at 0600 UTC 7 September. An early reconnaissance flight on that day reported peak winds of 71 mph at flight level and a minimum pressure of 1001 mb confirming the strengthening of the system.

Hortense moved over Guadeloupe, where the pressure dropped to 998 mb and produced sustained winds of 53 mph with gusts to 81 mph. It also produced torrential rains. The tropical cyclone moved westward into the eastern Caribbean and encountered a fast eastward moving upper-level short wave. This increased the vertical wind shear which temporarily inhibited strengthening. In fact, high resolution visible satellite images clearly showed that the low-level center of the tropical cyclone became exposed during the morning of the 8th. A new burst of deep convection developed over the center later in the afternoon and a gradual intensification began. By then, the short-wave had moved out of the area and the shear had relaxed. Hortense became a hurricane at 0600 UTC 9 September.

After slowing down just to the south southeast of Puerto Rico, Hortense took a jog toward the northwest and the center moved over southwestern Puerto Rico. Fixes from the San Juan WSR-88D radar indicate that the eyewall of Hortense reached the coast near Guanica about 0600 UTC on the 10th and moved over the southwestern tip of the island for about 2 hours.

Hortense moved through the Mona Passage and weakened slightly while the circulation was interacting with land. The center passed very close to Punta Cana, on the eastern tip of Dominican Republic where a calm was felt and the pressure dropped to 988 mb. The hurricane continued on a northwesterly track and the center moved just east of the Turks and Caicos Islands. Hurricane conditions were observed in some of these islands. Thereafter, Hortense briefly reached category four status with a peak intensity of 138 mph and 935 mb minimum pressure at 0000 UTC 13 September.

A developing trough along the eastern United States forced the hurricane to turn northward with an increase in forward speed. A weakened Hurricane Hortense rapidly crossed eastern Nova Scotia on 15 September and became extratropical while moving just south of Newfoundland later on that day.

b. Meteorological Statistics

There are unconfirmed reports of gusts to 109 mph in the southwestern tip of Puerto Rico about 0800 UTC 10 September. These strong winds may have been a local effect caused by the Venturi effect (acceleration between walls). Residents of the southwestern portion of Puerto Rico reported calm winds and that the "stars were out" as the eye crossed the area. Peak winds of hurricane force were reported over the Dominican Republic, and hurricane force winds were registered in Grand Turk and Nova Scotia.

Hortense was upgraded to a category four hurricane of 138 mph based on a report from a Hurricane Hunter plane of 141 mph at 700 mb in the northeast quadrant at 2130 UTC followed by 147 mph in the southeast quadrant at 2220 UTC. The plane also reported a minimum pressure of 935 mb, a closed eyewall of 11 nautical miles in diameter and an excellent stadium (outward slope of the convective clouds in the eyewall) effect at 2323 UTC. In addition, satellite objective T-numbers were of the order of 6.5 on the Dvorak scale, corresponding to an intensity 146 mph and a pressure of 935 mb. Visible satellite images revealed a spectacular cloud pattern with a clearly distinct eye during that time.

1. Rainfall Data

c. Casualty and Damage Statistics

There were 21 deaths attributed to Hortense; 18 in Puerto Rico and 3 in Dominican Republic.

Hortense devastated portions of Puerto Rico but most of the damage was not done by winds or storm surge. Instead, torrential rains produced flash floods and mud slides which killed at least 18 people. A preliminary report from FEMA indicates that nearly 11,463 homes were severely damaged by Hortense and agricultural losses were of the order of $127 Million. In addition, there was significant inland flooding in the low-lying areas as well as serious coastal flooding in Nagabo, Guayanilla and Ponce.

Three people were killed and 21 reported missing in the Dominican Republic and there was significant damage primarily in the northeastern portion of the country. A school and one church were demolished by winds or falling trees, numerous houses were damaged and several electrical poles went down. There was a 9-foot storm surge along the northeast coast. Roads were blocked due to flooding both from the storm surge and from torrential rains. In Samana, 80 percent of the agriculture was damaged.