Rita: another Katrina?

It's been a long time since Texas had a severe hurricane. Hurricane Bret hit the state in 1999 as a Category 4 hurricane, but was small and hit the relatively unpopulated Padre Island National Seashore. Bret gave Texas the unique distinction of being the only state to get hit by a Category 4 hurricane that didn't get its name retired. In 1988, Hurricane Gilbert, the strongest hurricane of all time, just missed Texas, hitting south of the border. The last hurricane to do serious damage to Texas was Hurricane Alica of 1983, which hit Galveston as a weak Category 3 storm, pushing a 10 - 12 foot storm surge into Galveston Bay. Alica killed 21 people, and its $2 billion price tag was the highest in Texas hurricane history.

Texas's luck is about to change. Rita, looking more and more like a nightmare copy of Katrina somehow displaced in time, will make sure of that. The forecast models we so heavily rely on did not anticipate another Katrina-like storm when Rita first formed and plowed through the Florida Straits. But now, the forecasts mirror the reality unfolding today in the Gulf of Mexico. Rita will be another huge destructive hurricane for the Gulf Coast. This time, it is Texas's turn. Every other state on the Gulf Coast has borne the burden of the immense destruction created by our unprecedented onslaught of intense hurricanes the past two hurricane seasons. No state will be left out.

Rita's impact on the Florida Keys
The residents of the Keys returning to their homes today are the lucky ones, for the Keys escaped serious damage. A 4 - 6 foot storm surge did hit the Lower Keys and flood the Coastal Highway, but this quickly subsided and the highway is now open to traffic again. Some minor to moderate wind damage occurred, but winds in Marathon only reached 38 mph, gusting to 53 mph, while the winds at Key West Airport reached 56 mph, gusting to 73 mph. There was an unofficial report of sustained winds of 75 mph gusting to 102 mph in Key West. Rainfall amounts of up to 12 inches occurred in the Keys, causing minor flooding problems.


Figure 1. Estimated rainfall from Hurricane Rita.


Figure 2. Wind and pressure plot from a coastal weather station in the Lower Keys. Note how the pressure after Rita's passage remains lower than that before her passage--Rita has depressed pressure values over an area hundreds of miles wide.

Rita now
Rita's presentation on satellite imagery is classic; she has a well-formed eye, large Central Dense Overcast (CDO) of cirrus clouds surrounding the eye, and well developed outflow on all sides, particularly to the north. This is the look of a solid, intensifying Category 4 hurricane. Intensification will continue until the eye shrinks to 10 miles or so in diameter and grows unstable, when the eyewall will collapse and an eyewall replacement cycle will begin. This may take another 24 hours or so, at which point Rita could be a Category 5 hurricane. Rita is currently smaller than Katrina, though. Katrina at her peak had hurricane force winds that extended outward 120 miles from the center; Rita's hurricane force winds only extend out 45 miles from the center. This will change as Rita continues to intensify and expand in size over the next day or two. There is little shear over Rita at present, nor is there expected to be the next three days. Water temperatures are 1 - 2C cooler over the central Gulf than they were for Katrina, which may keep Rita from attaining quite the intensity Katrina did. However, once Rita crosses the Gulf and arrives in the western Gulf on Friday, water temperatures warm back up to 30 - 31C, about the same temperatures as the waters Katrina had to work with. I doubt Rita will match Katrina's size or ferocity, but she might come to within 90% of the storm that Katrina was.

Rita at landfall
Rita's future intensity will largely be controlled by impossible-to-predict eyewall replacement cycles. Rita is growing large enough that she is creating her own upper level environment that will be relatively impervious to any external shearing winds that try to weaken her. I expect Rita to be a Category 4 hurricane at landfall.

The landfall location forecast has increased in confidence since yesterday, as the computer models have started to converge on a landfall location on the middle Texas coast. Western Louisiana still needs to be concerned, as does Corpus Christi, but New Orleans should escape Rita with nothing more than some fairly ordinary thunderstorms in some of the outermost spiral bands. A significant storm surge capable of flooding New Orleans is very unlikely.

A very significant storm surge is expected along and to the right of where Rita makes landfall on the Texas coast. Surge heights may reach 18 feet or higher, breaking the record 18.5 foot storm surge seen in 1961 during the Category 4 Hurricane Carla.

Elsewhere in the tropics
Tropical Storm Philippe continues northward away from land, and is not not expected to be a threat. Strong shearing winds will likely tear Philippe apart by Saturday. The remainder of the tropics are quiet and expected to remain so through Friday. By Saturday, the chances of tropical storm development off the coast of Africa begin to increase.

Jeff Masters