Preliminary Report
Hurricane Diana
04 - 09 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

Diana formed from a classical tropical wave which moved off Africa on 27 July and represented a typical example of developing disturbances over the Atlantic basin. The wave moved through the southern Windward Islands with a marked wind shift and a concentrated area of about 3.5 mb 24-hour pressure change. The wave had its maximum amplitude at the mid-levels and was accompanied by a strong upper level anticyclone reflected in the upper air data from the Lesser Antilles.

The first Air Force reconnaissance plane flew into the area when the wave was in the extreme southeastern Carribean and found squalls but no low-level circulation. Satellite pictures suggested that the system continued to be accompanied by a large area of thunderstorms. Surface and satellite observations indicated that the most active area was moving along the South American coast directly over the Netherland Antilles. On 4 August, high resolution satellite images indicated cyclonic rotation in the low clouds and deep convection covering a large portion of the western Caribbean, suggesting that a tropical depression was forming near the eastern tip of Honduras. That was confirmed by limited surface observations and by an Air Force plane which indeed found an incipient 1008 mb center later that day.

The depression rapidly reached tropical storm intensity while moving northwestward, under the influence of a middle level pressure trough in the Gulf of Mexico. Diana crossed the Yucutan peninsula and then took a more westerly track as the trough of low pressure in the Gulf weakened. Diana continued to intensify and reached category two hurricane status on 7 August near 95°W prior to landfall near Tuxpan, Mexico. After moving inland, Diana was declared dissipated by 1200 UTC on 8 August over western Mexico. However, a post-storm analysis indicated that a low pressure area with some convection persisted until 1200 UTC 9 August over the Eastern Pacific northwest near Puerto Vallarta.

b. Meteorological Statistics

In addition to the constant satellite surveillance, there were 4 Air Force reconnaissance missions after the system was declared a tropical depression. Daily checks were performed while the system traveled over the Caribbean as a strong tropical wave. The first Air Force plane center fix was on 5 August when the system was in the Gulf of Honduras. The plane reported 1003 mb and a maximum flight level wind of 53 mph northeast of the center. Ship observations over the northwest Caribbean indicated that Diana was becoming better organized and that the storm had a large circulation. Ship H9UM traveling from Puerto Cortes, Honduras to Las Minas, Panama reported 35 to 40 mph, 8-feet swells from the east-southeast and numerous showers and thunderstorms on 5 August when Diana was in developing stage. Merida, on the northwest tip of Yucutan, reported sustained winds of 35 mph with gusts to 40 mph, and heavy rain for several hours on 6 August, as the storm passed south of that location.

Diana strengthened rapidly after moving away from the Yucutan peninsula into the Bay of Campeche. Reports from the reconnaissance aircraft indicated that the surface pressure dropped to 986 mb at 1905 UTC 7 August and there were various reports of flight level winds reaching 128 mph over open waters. Those winds were stronger than would be expected for a system with such minimum pressure. Those winds were probably related to the surrounding orography and the funneling effect which occurs in that area. Tuxpan, near the point of landfall, reported a minimum pressure of 994.5 mb and heavy rain.

c. Casualty and Damage Statistics

There were 96 deaths attributed to Diana; 96 in Mexico.

According to an unofficial report from an amateur radio operator, the total number of deaths associated with Diana is estimated at 96. There were more than 100 people missing and 100,000 affected. The hurricane caused extensive damage to property, agriculture and roads in mountainous areas in the states of Hidalgo and northern Veracruz. The coastal town of Tamiahua was directly hit by the hurricane. Most of the damage was produced by torrential rains which triggered mudslides and flooding.