Hurricane Isidore was the ninth named storm, the seventh hurricane, and the fifth major hurricane of the 1996 Atlantic hurricane season. Isidore developed at a low latitude, then it moved west-northwest, eventually turning to the north out to sea, strengthening to a major hurricane as it did so. Isidore dissipated on October 1.
Isidore caused no damage, and no fatalities were reported in association with the hurricane.
|Formation||September 24, 1996|
|Dissipation||October 2, 1996|
|Highest winds||115 mph|
|Lowest pressure||960 mbar|
Isidore developed from a tropical wave that had a well-defined cyclonic circulation of clouds, that was also clearly marked at mid-levels in the Dakar sounding data, after it had emerged from the west coast of Africa on September 22. When deep convection increased, Dvorak classifications began on the wave on September 23, with the circulation passing well to the south of the Cape Verde Islands. Convection continued to increase, and it is estimated that by September 24, a closed surface circulation formed within the wave at 1200 UTC, and the system became a tropical depression. The depression was initially located to the south of a deep-layer anticyclone. It moved to the west-northwest, intensifying as it did so. On September 25, the depression became Tropical Storm Isidore. Further intensification then took place, and an eye began to appear intermittently. On September 26, Isidore became a hurricane.
At this point, both the mature stages and dissipating stages of Isidore were influenced by a well-defined mid to upper-level low that was quasi-stationary near 25°N 45-50°W through September 25. Soon after, the low weakened, and then moved north to near 35°N, but the low was re-energized when it reached that location, thanks to a mid-latitude shortwave trough which passed to the north on September 27 and September 28. The steering currents on the east side of the low gradually turned Isidore in a northerly direction. On September 28, Isidore's foward speed slowed to about 10 knots, but on October 1, its motion increased to 20 knots. During this period, Isidore intensified to reach its peak intensity of 115 mph winds and a pressure of 960 mb, a Category 3 hurricane. On September 29, the eye disappeared, and upper-level westerly to southwesterly wind shear started to weaken Isidore. On September 29, Isidore weakened to a tropical storm, and on October 1, Isidore weakened further to a tropical depression. Deep convection disappeared, and Isidore became extratropical on October 2.
Because it never came close to land, no watches or warnings were issued. Isidore had no affect on land whatsoever, except maybe some rough surf in Cape Verde.
Lack of Retirement
Because no damage occured, the name Isidore was not retired in the Spring of 1997 by the World Meteorological Organization. However, it was retired in the 2002 Atlantic hurricane season, and was replaced with the name Ike for the 2008 Atlantic hurricane season.