Rita upgraded to hurricane

Rita was upgraded to a hurricane with a special 9:15 am advisory. The 9:15am EDT hurricane hunter mission found winds at 5000 feet of 78 knots (90 mph), which corresponds to surface winds of minimal hurricane force (74 mph).The central pressure was 982 mb, down 3 mb in the past 1 1/2 hours. The Key West radar loop is most impressive the past three hours, showing a transformation from a disorganized, elliptical system to a more circular storm with much more intense spiral banding. An large eye with a 35 mile diameter has formed, but is still organizing and has gaps. Infrared sateliite images now show a warm spot where the eye is forming.



Here are the peak wind gusts as of 11:00 am EDT from Rita:

53 mph at Marathon Airport
50 mph at Key West International Airport
58 mph at Molasses Reef light
48 mph at Long Key light
72 mph at Sombrero Key light
47 mph at Sand Key light
38 mph at Dry Tortugas light

Sustained tropical force winds of 40 mph or higher will spread over the entire Keys chain this morning, extending as far north as Miami. The eye of Rita is shrinking, and the northern eyewall will pass over or just south of the lower Keys and Key West between noon and 3 pm today. Sustained winds of 70 - 80 mph and gusts of 100 mph will accompany passage of the northern eyewall. If the eyewall misses to the south, the lower Keys will escape with sustained winds of 50 - 60 mph and gusts to 85 mph. A storm surge of 5 - 7 feet will accompany the arrival of the eyewall, flooding parts of the coastal highway and low-lying areas. Moderate roof damage and extensive damage to mobile homes is also expected in the lower Keys.

Rita in the Gulf
Once Rita emerges into the Gulf of Mexico this afternoon, continued strengthening is expected--but not explosive deepening. The center of the upper-level high that Rita needs to carry away all the air her eyewall convection is injecting into the upper atmosphere is located to the east of her, and thus the outflow over Rita is poor in some areas, particularly the south side. This situation is predicted to improve some and allow Rita to strengthen to a Category 3 hurricane by Thursday. Water temperatures over the middle of the Gulf of Mexico are 1 - 2C cooler than those near Key West, thanks to all the cold water stirred up by Katrina. This may keep Rita as a strong Category 2 hurricane. Once Rita approaches the coast of Texas, the cold water wake of Katrina ends and water temperatures warm up again, which may allow some more intensification. Rita is not expected to reach Category 4 status.


Figure 2.Sea Surface temperatures for Sunday, September 18. Note the cooler wake in the center of the Gulf left by Katrina.

Threat to Louisiana fades
Last night, the NOAA jet flew its first mission into Rita, and collected high-density data used to initialize last night's computer model runs. The models are more tightly clustered than before, and now all the models point to a landfall in Texas Saturday, somewhere between Brownsville and Galveston. She is expected to be a Category 2 or 3 at landfall. Western Louisiana is still at high risk, but New Orleans will miss this hurricane. However, if Rita makes landfall in western Louisiana, she may push 1 - 2 feet of storm surge into Lake Pontchartrain. This could cause problems with the weakened New Orleans levee system and possibly destroy the temporary patches that were installed, allowing the areas of the city that are starting to drain to flood once more.

Philippe
Philippe is slowly strengthening but heading northward out to sea. Philippe will continue to strengthen and head north, and is not expected to affect any land areas, including Bermuda.

Wave between Africa and the Antilles
A large low pressure system is halfway between Africa and the Antilles islands. While this system does have a surface circulation and considerable deep convection, 15-20 knots of upper-level wind shear will keep this system from developing into a tropical depression. Later in the week, the shear over the central Atlantic is expected to decrease, and we could see another tropical storm form in this region, but probably not from the current area of disturbed weather mentioned above.

Jeff Masters