Preliminary Report
Hurricane Dean
31 July - 09 August 1989

1989 PRELIMINARY REPORTS

Tropical Storm Allison (TS)
Tropical Storm Barry (TS)
Hurricane Chantal (1)
Hurricane Dean (2)
Hurricane Erin (2)
Hurricane Felix (1)
Hurricane Gabrielle (4)
Hurricane Hugo (5)
Tropical Storm Iris (TS)
Hurricane Jerry (1)
Tropical Storm Karen (TS)

a. Synoptic History

On 27 July a westward moving tropical wave emerged from the northwest coast of Africa, as detected in analyses of rawinsonde data from Dakar and in METEOSAT imagery. On 31 July the wave showed sufficient deep convection and a persistent enough cloud system center to be classified using the Dvorak technique by satellite analysts at the NHC. The weather system became the fifth tropical depression of the 1989 hurricane season near 0600 UTC on the 31st while located midway between the Lesser Antilles and the Cape Verde Islands.

The depression generally moved westward near 17 mph, and based on satellite intensity estimates, attained tropical storm strength by 0600 UTC on 1 August. Tropical Storm Dean moved toward the west-northwest while continuing to strengthen, and was upgraded to a hurricane near 1200 UTC on 2 August immediately after the first report of hurricane force winds from an Air Force reconnaissance plane.

By 3 August, Dean decreased in forward motion and turned toward the northwest, in response to a collapsing ridge to the north and a developing upper-level trough off the U.S. east coast. By 4 August, Dean turned more toward the north as the upper trough off the U.S. deepened. This northward direction of motion continued with an increase in forward speed to near 17 mph, bringing the eastern eyewall over the island of Bermuda near 1800 UTC on 6 August. This was the first time sustained hurricane force winds were recorded at Bermuda since Hurricane Emily passed over the island in 1987.

The lowest pressure reported by reconnaissance aircraft was 970 mb, just after the hurricane passed Bermuda. However, after the last aircraft penetrated the cyclone, the cloud pattern observed in satellite imagery became even better organized with a well-defined eye embedded within a small but cold central dense overcast. Based on satellite estimates, the minimum pressure and maximum winds likely occurred near 0000 UTC on 7 August.

After passing Bermuda, Dean turned toward the northeast and accelerated in response to an upper level trough moving eastward across the northeast U.S. The cyclone passed over Sable Island, Nova Scotia, then began to slowly lose tropical characteristics as it moved over southeastern Newfoundland, The cyclone became extratropical over the North Atlantic while moving toward the northeast at about 52 mph.

b. Meteorological Statistics

As the eastern eyewall passed over Bermuda, the highest sustained wind reported was 81 mph with gusts to 113 mph at the U.S. Naval Annex on the western end of the island.

Sable Island, Nova Scotia reported sustained hurricane force winds while St. Pierre Island off the south coast of Newfoundland and Bonavista on the northeast coast of Newfoundland both reported sustained tropical storm force winds.

1. Storm Surge Data

Although the hurricane remained well offshore of the U.S. east coast, tides of 1.7 feet above normal were reported on the Outer Banks of North Carolina, and were apparently generated by swells from Hurricane Dean.

2. Rainfall Data

The 24 hour rainfall at Bermuda associated with Dean was 2.45 inches.

c. Casualty and Damage Statistics

There were no reported deaths due to Hurricane Dean. Since the hurricane veered away from the northeast Caribbean, no significant damage was reported from the Leeward or Virgin Islands. However, two persons on a sailboat en route from the Virgin Islands to Bermuda narrowly escaped disaster when caught in the hurricane. An Air Force plane on a reconnaissance mission into the eye of Dean spotted the sailboat, which reportedly was not equipped with a radio to receive the latest marine advisories.

Personal injuries reported on Bermuda totalled 16. Eleven of these were minor, while the more serious injuries included glass in eye, broken arm, dislocated shoulder and head injuries. Although it is difficult to accurately assess the total cost of damage caused by Dean, the common estimate given by public officials in Bermuda is $5 Million. Insurance companies reported claims for damage on 648 buildings, 72 boats, 36 vehicles and 1 pier. In addition to this cost, $3.9 Million in damage occurred to the U.S. Naval base, bringing the total damage assessment on Bermuda to $8.9 Million.

No significant damage or injuries were reported on Sable Island Island or Newfoundland, although Canadian Coast Guard had to rescue three Frenchmen after their sailboat was demasted by the hurricane off the coast of Nova Scotia.