Tropical Storm Dean 2001

Preliminary Report
Tropical Storm Dean
22 - 29 August 2001


Tropical Storm Allison (TS)
Tropical Storm Barry (TS)
Tropical Storm Chantal (TS)
Tropical Storm Dean (TS)
Hurricane Erin (3)
Hurricane Felix (3)
Hurricane Gabrielle (1)
Hurricane Humberto (2)
Hurricane Iris (4)
Tropical Storm Jerry (TS)
Hurricane Karen (1)
Tropical Storm Lorenzo (TS)
Hurricane Michelle (4)
Hurricane Noel (1)
Hurricane Olga (1)

Dean developed over the Virgin Islands and produced heavy rains in Puerto Rico.


a. Synoptic History

Dean formed from a large tropical wave that crossed Dakar with minimal shower activity between 14 and 15 August. It moved westward and gradually began to develop thunderstorms. By the time the wave was near 58 to 59 W, there was enough organization on satellite imagery to dispatch a reconnaissance plane to the area. Reports from the plane indicated that the wave had a large amplitude and strong winds, but no closed circulation. At 1200 UTC 22 August, as the wave was moving over the northern Leeward Islands at 17 to 23 mph, it developed a surface center. The center was observed on satellite imagery as well as on San Juan radar. This was later confirmed by a reconnaissance plane and surface observations.By the time the system developed a surface circulation, it already had tropical storm force winds, northeast of the 1009 mb center. This transition is not uncommon to occur with strong, fast-moving tropical waves. It is estimated that Dean formed at 1200 UTC 22 August and moved west-northwestward through the U.S. Virgin Islands. During the next 24 hours, Dean encountered a hostile shearing environment produced by an upper-level trough, causing the low-level center to move away from the convection. A reconnaissance mission on the 23rd was not able to find a closed circulation and Dean became a tropical wave by 1500 UTC.

Dean's remnants moved rapidly to the north and became embedded within a large middle-level trough just east of the U.S. A reconnaissance flight on the 24th found a broad area of low pressure and a few squalls. The low appeared to have some non-tropical characteristics since the strongest winds and convection were removed from the minimum pressure area. On the 25th, the low moved very little and convection began to develop near the center of circulation. By 1800 UTC on the 26th, there was enough thunderstorm activity to re-classify the system as a tropical depression and it is estimated that it reached tropical storm status by 0000 UTC on the 27th. Dean continued to strengthen and reached its peak intensity of 69 mph and a minimum pressure of 994 mb at 1800 UTC 27 August. Thereafter, Dean moved over cooler waters and became an extratropical cyclone by 1800 UTC on 28 August. It was absorbed by a frontal low north of 50 N on the 29th.

b. Meteorological Statistics

Juliana Airport at Saint Maarten reported gusts to 40 mph at 1000 UTC on the 22nd. St Thomas reported 40-mph winds with peak gusts to 48 mph at 1818 UTC. St Croix reported gusts to 47 mph at 1731 UTC on the same day. Craig D. Karnits, a private observer in St Croix reported several peak gusts to 72 mph with a Texas Weather Instrument WRL32 anemometer. However, the instrument is located on a 300-foot hill. A report of 63 mph and 1004 mb pressure from the vessel WGMJ was used to reinitiate advisories on Dean. Heaviest rainfall occurred in Puerto Rico.

c. Casualty and Damage Statistics

No reports of casualties associated with Dean have been received. However, there were reports of damage caused by heavy rains in Puerto Rico. Widespread flooding along the eastern and southern sections of the island caused two bridges to collapse. A large number of highways were inundated. There were 1320 homes flooded. Preliminary reports indicate that the agricultural damage is about $2 Million. There were power outages, small trees blown down and some roads damaged in the US Virgin Islands.

Maximum Intensity For Tropical Storm Dean
22 - 29 August, 2001

Position Pressure
Wind Speed
Lat. (°N) Lon. (°W)
27/1800 40.6 59.4 994 70 Tropical Storm