Preliminary Report
Tropical Storm Marco
09 - 13 October 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

Early on 9 October, Tropical Storm Klaus was located east of the Bahamas, moving northwest, and becoming poorly organized. At the same time, a cold low aloft was developing over Cuba. By 1200 UTC on 9 October, Klaus had dissipated and the new low had developed downward to the surface over central Cuba. This new low was designated Tropical Depression Fifteen near Caibarien, Cuba.

The depression moved west-northwest along the north coast of Cuba, and then turned toward the northwest over the Florida Straits. The system became Tropical Storm Marco at 0600 UTC on 10 October while centered about 30 nautical miles south-southwest of Key West, Florida. After passing midway between the Dry Torugas and Key West, Marco moved generally toward the north at 6 to 12 mph just off the Florida west coast. The storm reached its peak intensity near 0600 UTC on 11 October with 63-mph sustained winds and a 989-mb central pressure. The center moved to just a few nautical miles west of Bradenton Beach by 1200 UTC on 11 October and continued hugging the coast, with much of its circulation over land in the St. Petersburg area, to near Clearwater around 1500 UTC.

Marco was downgraded to a tropical depression at 0000 UTC on 12 October just offshore of Cedar Key, Florida. The central pressure rose as the depression continued moving inland, and the system was declared extratropical at 1200 UTC over central Georgia. The low could be followed in surface pressure and wind reports for another 24 hours, moving through Georgia and into South Carolina. The weakening low was finally absorbed by a frontal system in the vicinity of Columbia, South Carolina, near 1200 UTC on 13 October.

Although Marco brough sustained tropical storm force winds to several areas on the Gulf of Mexico side of the Florida peninsula and to the Florida Keys, the storm and its remnants will also be remembered for contributing to heavy rains previously initiated by the remnants of Klaus over Georgia and the Carolinas.

b. Meteorological Statistics

There were five aircraft reconnaissance missions into Marco with a total of 27 center fixes during a 42-hour period from the time Marco was in the Florida Straits until moving onshore near Cedar Key. The best track wind of 63 mph on the 11th is based on an aircraft measurement of 71 mph at 1500 feet. The highest intensity estimate from satellite imagery during this time was also 63 mph.

The lowest central pressure reported by U.S. Air Force reconnaissance aircraft was 989 mb at 0816 UTC on 11 October, while the lowest pressure reported over land was 992.4 mb at 0857 UTC. The land report came from an observer on Lido Key, just west of Sarasota, with a barometer that had been calibrated at the Atlantic Oceanographic and Meteorological Laboratory's Hurricane Research Division a week earlier.

Official records of the National Hurricane Center indicate the last year the United States went without a "hit" from a tropical storm or hurricane was 1890. Although Marco was downgraded to a tropical depression just prior to making final landfall in the vicinity of Cedar Key, and although all the aircraft reconnaissance center fixes of Marco during the tropical storm stage reported the actual center remaining over water, Marco will be counted as a U.S. "hit" since much of the inner circulation was actually over the St. Petersburg area at one time.This is consistent with an adaptation of the definition of a direct hit found in Hebert and Case (1990). Using "R" as the radius of maximum winds in a tropical cyclone (the distance in miles from the storm's center to the circle of maximum winds around the center), all or parts of counties falling within approximately 2R to the right and R to the left of a storm's center were considered to have received a direct hit. (This assumes an observer at sea looking toward the direction of motion.) In addition, the Air Reconnaissance Weather Officer onboad one of the Air Force missions flying Marco reported she could see land while in the center making a fix just offshore Sarasota.

Several reports of sustained tropical storm force winds were noted along the west coast of the Florida peninsula and the Florida Keys, while the highest reported gusts reached 85 mph at the Sunshine Skyway Bridge across Tampa Bay and also at Bradenton located just south of Tampa Bay.

1. Rainfall Data

2. Tornadoes

c. Casualty and Damage Statistics

Damage and Deaths associated with Marco are unknown at this stage.