Monday, August 30, 2004
Hurricane Frances: A Detailed Analysis
Josh Larson @ 7:51 PM
Hurricane Frances, at present a strong category 3 hurricane, with sustained winds of 125mph and a central pressure of 945mb, is currently 190 miles northeast of the Northern Leeward Islands.
Most models indicate that it will make landfall sometime late Saturday or early Sunday over the southeastern United States. "Southeastern United States...isn't that a bit vague?," you might wonder. While the following is only my personal meteorological opinion, here are some assumptions I have developed:
(1) Hurricane Frances will not turn back out to sea (or re-curve); instead, it is likely to make landfall over the continental United States.
In the first image, you will see a 24-hour 850mb-vorticity graphic from the GFS. As you can see, a prominent Bermuda high is visible over the northern Atlantic. The results is a strong west-to-east flow or steering current near and just north of Frances. From this fact alone, it is quite unlikely that Frances will curve back out to sea. In addition, the lack of a trough over the eastern US will further dissuade any tropical cyclone from being shunted away from the US east coast.
(2) I believe it is unlikely that Frances will take a southerly track and enter the Gulf of Mexico south of Florida. Instead, it is likely to make landfall over eastern FLA, GA, or SC. Why?
The second image is a 96-hour hour 200mb-vorticity graphic from the GFS. At this very high level of the atmosphere, the flow over the Gulf of Mexico is southwest to northeast, which, in my opinion, is likely prevent Frances from taking a southerly track into the Gulf of Mexico. Instead, I feel Frances will take a more northerly track -- reducing the chances of it hitting southern Florida head on.
(3) It seems probable that the impacts of Frances on the DC area, though awfully far away to say with much confidence, may be minimal. Why?
This image is a 144-hour 200mb-vorticity image again from the GFS. Note the very conspicuous lack of a trough over the east coast. Instead, the core of the strong southerly flow is futher west, over Mississippi Valley, and the Tennessee River Valley. I believe that Frances is not likely to take an easterly path up the eastern seaboard and, instead, take a much more westerly path, which may keep much of the impact of Frances to our west.
A few more final comments. I do not believe that Frances will weaken appreciably before making landfall due to relatively "favorable" surface weather patterns over its projected track; however, I do not believe that Frances will strengthen much more either.
In my humble meteorological estimation, I here is my nearly week-out tentative call: Hurricane Frances will make landfall as a strong CAT 3 or CAT 4 hurricane late Saturday or early Sunday most likely somewhere north of West Palm Beach, Fla. and south of Myrtle Beach, SC.
I must also relay this important caveat from a forecaster at the Tropical Prediction Center:
"IT IS EXTREMELY IMPORTANT NOT TO FOCUS ON THE EXACT TRACK...ESPECIALLY AT 96 AND 120 HOURS...BECAUSE THE HURRICANE IS NOT A POINT...ESPECIALLY A HURRICANE AS LARGE AS FRANCES...AND FORECASTS AT THESE EXTENDED TIME RANGES CAN EASILY HAVE ERRORS OF SEVERAL HUNDRED MILES."
So take what I've opined with a grain of salt, but know that I have spent considerable time today analyzing computer models and various atmospheric factors to come up with the above forecast, and that I have spent months researching tropical cyclones over the past four years.
And, follow the TPC's own timely updates and information on Hurricane Frances.
Most models indicate that it will make landfall sometime late Saturday or early Sunday over the southeastern United States. "Southeastern United States...isn't that a bit vague?," you might wonder. While the following is only my personal meteorological opinion, here are some assumptions I have developed:
(1) Hurricane Frances will not turn back out to sea (or re-curve); instead, it is likely to make landfall over the continental United States.
In the first image, you will see a 24-hour 850mb-vorticity graphic from the GFS. As you can see, a prominent Bermuda high is visible over the northern Atlantic. The results is a strong west-to-east flow or steering current near and just north of Frances. From this fact alone, it is quite unlikely that Frances will curve back out to sea. In addition, the lack of a trough over the eastern US will further dissuade any tropical cyclone from being shunted away from the US east coast.
(2) I believe it is unlikely that Frances will take a southerly track and enter the Gulf of Mexico south of Florida. Instead, it is likely to make landfall over eastern FLA, GA, or SC. Why?
The second image is a 96-hour hour 200mb-vorticity graphic from the GFS. At this very high level of the atmosphere, the flow over the Gulf of Mexico is southwest to northeast, which, in my opinion, is likely prevent Frances from taking a southerly track into the Gulf of Mexico. Instead, I feel Frances will take a more northerly track -- reducing the chances of it hitting southern Florida head on.
(3) It seems probable that the impacts of Frances on the DC area, though awfully far away to say with much confidence, may be minimal. Why?
This image is a 144-hour 200mb-vorticity image again from the GFS. Note the very conspicuous lack of a trough over the east coast. Instead, the core of the strong southerly flow is futher west, over Mississippi Valley, and the Tennessee River Valley. I believe that Frances is not likely to take an easterly path up the eastern seaboard and, instead, take a much more westerly path, which may keep much of the impact of Frances to our west.
A few more final comments. I do not believe that Frances will weaken appreciably before making landfall due to relatively "favorable" surface weather patterns over its projected track; however, I do not believe that Frances will strengthen much more either.
In my humble meteorological estimation, I here is my nearly week-out tentative call: Hurricane Frances will make landfall as a strong CAT 3 or CAT 4 hurricane late Saturday or early Sunday most likely somewhere north of West Palm Beach, Fla. and south of Myrtle Beach, SC.
I must also relay this important caveat from a forecaster at the Tropical Prediction Center:
"IT IS EXTREMELY IMPORTANT NOT TO FOCUS ON THE EXACT TRACK...ESPECIALLY AT 96 AND 120 HOURS...BECAUSE THE HURRICANE IS NOT A POINT...ESPECIALLY A HURRICANE AS LARGE AS FRANCES...AND FORECASTS AT THESE EXTENDED TIME RANGES CAN EASILY HAVE ERRORS OF SEVERAL HUNDRED MILES."
So take what I've opined with a grain of salt, but know that I have spent considerable time today analyzing computer models and various atmospheric factors to come up with the above forecast, and that I have spent months researching tropical cyclones over the past four years.
And, follow the TPC's own timely updates and information on Hurricane Frances.
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