Preliminary Report
Tropical Storm Ana
29 June - 05 July 1991

1991 PRELIMINARY REPORTS

Tropical Storm Ana (TS)
Hurricane Bob (3)
Hurricane Claudette (3)
Tropical Storm Danny (TS)
Tropical Storm Erika (TS)
Tropical Storm Fabian (TS)
Hurricane Grace (2)

a. Synoptic History

Ana, the first tropical cyclone of the 1991 hurricane season, formed from a low to mid-level cyclone that developed downward to the surface in the vicinity of the Bahamas.

A post-analysis of upper-air data, surface charts, and satellite imagery revealed that the incipient stages of Ana may have begun as early as 1200 UTC 25 June 1991. At that time, there was a low at 850 mb and 700 mb about 275 nautical miles east of Jacksonville, Florida; a stationary front at the surface oriented east-west near 30°N; and an anticyclone over north Florida at upper levels. During the next several days, the low took an anticylonically curving path toward the Bahamas. By 1200 UTC on 29 June, a small surface low was present embedded in a trough over the northern Bahamas.

The trough with the embedded low continued moving westward across south Florida, curving northward along Florida's west coast, and then northeastward toward the St. Augustine area by 0000 UTC 2 July 1991. The low pressure area was considered to weak to be classified (using the Dvorak technique) as it emerged into the Atlantic by 1200 UTC, but by 1800 UTC the convection was becoming better organized. It is estimated that Tropical Depression One formed in this low pressure area when centered about 85 nautical miles south of Charleston, South Carolina.

Within 12 hours, Tropical Depression One began accelerating toward the northeast while maintaining a course offshore and parrallel to the coasts of South and North Carolina. An Air Force Reserve reconnaissance plane reached the system center at 1600 UTC 3 July but found only a weak circulation with 35 mile winds at the 1500 feet flight level and a central pressure of 1008 mb at the surface. However, NOAA buoy 41001 (34.9°N 72.9°W) at 1900 UTC 3 July, reported an 8.5 minute sustained wind of 38 miles and a pressure of 1006. Thus, the maximum 1-minute sustained wind was deemed to be of tropical storm force and a special statement was issued by the National Hurricane Center at 2000 UTC indicating that a tropical storm had formed, and the first advisory on Tropical Storm Ana was issued at 2200 UTC.

Tropical Storm Ana began moving east northeastward near 29 miles while approaching a quasi-stationary east-west frontal zone.
An unidentified ship located 20 nautical miles south of the center at 0900 UTC on the 4th estimated sustained winds of 52 miles. This was the highest, sustained, surface wind speed reported for Ana.

Ana continued moving generally eastward, just south of the frontal zone and lost its tropical characteristics by 1800 UTC 5 July 1991 over the cold waters of the North Atlantic.

b. Meteorological Statistics

After becoming a tropical depression, Ana was primarily of concern to the marine community. By the time it became a tropical storm, the center was heading away from the east coast of the United States.

c. Casualty and Damage Statistics

There were no reports of damage, injuries, or deaths related to Ana.