Gulf Warm-water Eddies Intensify Hurricane Changes

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Scientists monitoring ocean heat and circulation in the Gulf of Mexico during Hurricanes Katrina and Rita have a new understanding of how these tropical storms can gain intensity so quickly: The Gulf of Mexico's "Loop Current" is likely intensifying hurricanes that pass over eddies of warm water that spin off the main current.

Two days before Hurricane Rita, Black and Rick Lumpkin of AOML, and Peter Niiler of the Scripps Institution of Oceanography, deployed surface drifters that measure surface and subsurface thermal conditions while traveling clockwise around a Loop Current warm eddy just south of La. The eddy was lying in the path of Rita.

"This represents one of the most comprehensive ocean-data sets where two major hurricanes passed through the same region," said Frank Marks, director of NOAA's Hurricane Research Division. "This series of observations is a testament to how new ocean observations are helping us understand hurricane intensity changes."

Hurricanes Katrina and Rita also have much in common with Hurricane Opal, a category 4 storm that occurred a decade ago, on Oct. 4. During Opal, meteorologists first recognized the pivotal role that deep, warm eddies play in quickly building hurricane intensity. Opal encountered a warm- water eddy in the Gulf of Mexico and strengthened in intensity from Category 1 to Category 4 in just 14 hours.

http://www.sciencedaily.com/releases/2005/10/051004083920.htm