Preliminary Report
Tropical Storm Edouard
02 - 11 August 1990

1990 PRELIMINARY REPORTS

Tropical Storm Arthur (TS)
Hurricane Bertha (1)
Tropical Storm Cesar (TS)
Hurricane Diana (2)
Tropical Storm Edouard (TS)
Tropical Storm Fran (TS)
Hurricane Gustav (3)
Tropical Storm Hortense (TS)
Hurricane Isidore (2)
Hurricane Josephine (1)
Hurricane Klaus (1)
Hurricane Lili (1)
Tropical Storm Marco (TS)
Hurricane Nana (1)

a. Synoptic History

Edouard began on 2 August near latitude 38°N, longitude 23°W as a wave on a cold front. Within the next 24 hours the wave developed into a strong midlatitude cyclone capped with an upper-cold low at the 200-mb level. Rapid baroclinic development over sea surface temperatures of 22°C produced a 1009-mb storm by 1200 UTC 3 August.

The non-tropical storm drifted northward on 3 August and began to weaken slightly on 4 August as it turned toward the southwest and moved across the Azores. Heavy rains and gusty winds of 23 to 35 mph were reported by the islands on 4 August. From 6 August through the morning of 8 August the system made a counter-clockwise loop while located between 200 and 300 miles to the southwest of the Azores. During this time deeply organized convection developed near the center of the circulation, and the system was designated Tropical Depression Six at 1800 UTC 6 August.

The cyclone at the 200-mb level had drifted to the southwest with the surface circulation. By the morning of 8 August the upper low began to move toward the northeast and weakened to an open trough by the morning of 9 August. The depression responded by strengthening to storm strength (satellite and ship data) by 1800 UTC 8 August and moving toward the northeast. Strong shearing from the southwest stripped the storm of its convection by 10 August. The system was downgraded to a tropical depression by 1200 UTC and declared extratropical by the morning of 11 August.

The extratropical low-pressure center with winds of 23 to 35 mph continued toward the east and dissipated near the coast of Portugal on 13 August.

Edouard was never totally tropical since the system had an upper-cold low or trough over its low-level circulation at all times. Nor was the storm ever over warm termperatures warmer than 23°C. However during the critical time period of 6 to 8 August when the system made the 360° loop and began to threaten the Azores, the system developed deeply organized convection. The National Hurricane Center observed these tropical characteristics and declared the system tropical.

b. Meteorological Statistics

Strongest winds of 46 mph were recorded by the ship VRAZ near 38.9°N, 24.7°W within 24 hours (1800 UTC 3 August) after the wave began to develop on the cold front. Various reporting stations in the Azores reported storm-force gusts on 9 August as the tropical storm moved northeastward toward the islands.

Maximum sustained winds from the town of Horta at 0600 UTC 9 August were from the southeast at 35 mph with gusts to 69 mph. Lowest surface pressure was 1004.6 mb. Lajes Air Force Base on the island of Terceira reported surface winds of 38 mph. However sustained winds of 52 mph with a gust to 71 mph were recorded on a 417-foot tower.

c. Casualty and Damage Statistics

There were no casualties and damage in the Azores was minimal.