Hurricane Isidore - Meteorological History

Meteorological History

On September 9, a tropical wave moved off the coast of Africa. Despite moving through a dry environment, its convection became organized as an anticyclone developed over the wave. On September 14, convection was well-organized enough around a small closed wind circulation to classify the system as Tropical Depression Ten near Trinidad and Tobago. Land interaction from Venezuela later weakened the depression back to a tropical wave. The wave continued west-northwestward through the Caribbean, and redeveloped into a tropical depression on September 17 while 140 miles (230 km) south of Jamaica.

Embedded within a weak steering current, it drifted to the northwest, and strengthened into Tropical Storm Isidore on September 18 near Jamaica. After grazing the island, it quickly intensified to a hurricane late on September 19 while south of Cuba. Isidore's maximum sustained winds reached 100 miles per hour (160 km/h) near the Isle of Youth, and weakened slightly to an 85 miles per hour (137 km/h) hurricane as it made landfall on Cabo Frances late on September 20. The hurricane crossed the island, then slowed as it moved westward across the Gulf of Mexico. Favorable conditions aloft with warm water temperatures allowed Isidore to quickly intensify to a peak of 125 miles per hour (201 km/h) winds on September 21.

Despite Dvorak satellite estimates of 145 miles per hour (233 km/h), reconnaissance aircraft indicated Isidore remained a 125 miles per hour (201 km/h) Category 3 hurricane, with pressures dropping to 934 mbar (27.6 inHg), typical of a Category 4 hurricane. It is the lowest minimum pressure ever observed for an Atlantic hurricane which did not exceed Category 3 intensity. With nearly ideal conditions for development, Isidore was forecast to reach winds of 150 miles per hour (240 km/h) over the northern Gulf of Mexico. High pressures to its north forced it southward, and Isidore made landfall at Telchac Puerto in Yucatán as a major hurricane on September 22. It weakened rapidly as it nearly stalled over Yucatán, and was only a minimal tropical storm after being inland for 30 hours.

The inner core of convection collapsed while over southeast Mexico, and upon moving northward and reaching the Gulf of Mexico again, it was a large but weak tropical storm. Conditions favored significant strengthening, but Isidore did not redevelop central convection until reaching the northern Gulf of Mexico. The strengthening system hit Grand Isle, Louisiana on September 26 as a 65 miles per hour (105 km/h) tropical storm, but weakened quickly into a tropical depression after moving inland. The system raced to the northeast, and became an extratropical cyclone on September 27 before becoming absorbed in a frontal zone over Pennsylvania that night.