Threat of Hurricane Season Isn't Over Yet

(Oct. 3) -- August and September are the most active months for hurricanes in the Atlantic basin, but it's too early for coastal residents of the United States to assume that the danger has passed. This might be especially true this year since the season is expected to remain active for a longer period of time than normal.

From the start of October through the end of November, the official end of hurricane season, three named storms (tropical storms and hurricanes) typically occur, roughly one-quarter of a typical season.

The most likely locations for storm development in October are the Caribbean, Gulf of Mexico and western Atlantic. During the heart of the season, many storms form in the central or eastern Atlantic. Formation close to land increases the likelihood of the storms making landfall, and the most common track is for storms to form in the Caribbean and head northward toward Florida and along the East Coast.


(Image courtesy of NOAA)

As Tropical Storm Nicole exemplified last week when it took such a track, a tropical system does not need to be intense in order to produce life-threatening weather conditions.

Forecasters point to warmer-than-normal sea-surface temperatures and the presence of a La Nina, which is a cooling of sea-surface temperatures in the tropical Pacific, as reasons for a potentially active late part of the season.

The warm water, of course, provides potential fuel for hurricanes, and La Nina alters global weather patterns in such a way that the Atlantic basin often experiences less vertical wind shear during the latter part of the season. Vertical wind shear, which is an increase in wind with elevation, is not conducive to tropical development. Tropical systems gain their energy from the warm water below, not instability high in the atmosphere as winter storms do, and wind aloft inhibits storm development or weakens existing storms.

For the past couple of days, National Hurricane Center forecasters have been monitoring a couple of areas of disturbed weather in and near the Caribbean for potential development. Fortunately, though, no development appears imminent.

When conditions are favorable, storms during the latter part of the season can be every bit as strong as storms during the heart of the season. Hurricane Wilma -- with a maximum sustained wind of 175 mph -- established a record for the lowest pressure of any Atlantic basin hurricane on October 19, 2005. Wilma, which killed 35 people and caused an estimated $16 billion in damages, was more intense than the two other Category 5 hurricanes of the record-breaking 2005 season: Katrina and Rita.

Hurricane Kate, which formed in mid-November 1985, was the latest major hurricane (Category 3 or higher) in the Atlantic basin. The storm's sustained winds peaked at 120 mph, and the storm made landfall in northwestern Florida as a Category 2 storm on November 22. The hurricane killed five people in Florida and caused an estimated $300 million dollars (1985 value) in damage.