September 2, 2004
By JESSIE-LYNNE KERR
The Times-Union

In the world of forecasters, Florida-pounding Hurricane Charley was a pencil-thin line on the map -- but Hurricane Frances is a thick black line and a monster storm that promises to ravage the state.

The question no one can answer yet is what part.

Late Wednesday, the National Hurricane Center issued a hurricane watch for about 280 miles of Florida coast from Florida City to Flagler Beach. A hurricane watch means that those areas could start feeling hurricane conditions within 36 hours.

Nearly half a million coastal residents, from Daytona Beach south to Vero Beach, were urged to evacuate. Gov. Jeb Bush declared a state of emergency, which orders the activation of the Florida National Guard and other preparations. He also warned more evacuations may be ordered.

''I can't emphasize enough how powerful this is," National Hurricane Center director Max Mayfield said. "If there's something out there that's going to weaken it, we haven't seen it.''

A ridge of high-pressure in the atmosphere off the U.S. East Coast will determine Frances' path, Mayfield said. If it stays strong, it will push Frances south toward Florida. If it weakens, it will steer the hurricane north to Georgia or South Carolina.

At 11 p.m. Wednesday, the latest projection from the National Hurricane Center had Frances hitting the east coast of Florida Saturday evening in the vicinity of Melbourne/Cocoa Beach and heading northwest up the state.

Frances was a dangerous Category 4 hurricane Wednesday night and forecasters said it could strengthen to a Category 5 storm with winds more than 155 mph, which would cause catastrophic damage as it hit the Florida coast.

"Remember, it is important that people don't focus on the exact forecast track because there is a lot of uncertainty with that," said Steve Letro, chief meteorologist at the National Weather Service office in Jacksonville. "I am sure that was a problem with some people who got caught in Charley because they were focusing on the specific track of the forecast and not on the fact that hurricane warnings were in effect for their area.

"People should listen for the watches and warnings," Letro emphasized. "Those watches and warnings should determine what their actions should be, not that skinny line on the hurricane map."

Changing that habit is critical, Letro said, "because this one is especially big."

When Charley stomped across Florida on Aug. 13 from the Gulf of Mexico to the Atlantic with sustained winds that reached 145 mph, it was blamed for 27 deaths.

Hurricane Charley heavily damaged or destroyed more than 30,000 homes and caused an estimated $7.4 billion in insured losses, making it the worst natural disaster to hit Florida in 12 years. Then, Hurricane Andrew killed 15 people and did $15.5 billion in insured damage.

"Charley was intense," Letro said, "but it was a relatively small system. Charley's destructive winds were no more than 50 miles in diameter. Frances has hurricane-force winds over a diameter of more than 150 miles, three times the size of Charley."

Letro said he was not trying to terrify anybody at this point, "but even if the storm doesn't come directly over us, you can still have a significant impact from it."

Hurricanes are normally difficult to forecast when they get near the Jacksonville area's latitude and longitude, Letro said.

"In this area, we are at the western edge of the Atlantic or Bermuda high. Through most of the Atlantic that Bermuda high steers storms nicely westward toward us across the ocean," Letro said. "But in the western Atlantic, the influence of that high pressure lessens and the storm can respond to other weather systems."

That makes the challenge in hurricane forecasting identifying what those other weather systems will be, where they will be, how strong they will be and how they are going to interact with the hurricane.

By this morning, Letro said, Frances will be entering that area where the effect of the Bermuda high will be lessening, but another high pressure system will be moving off the eastern United States. Until that second system begins to exert its influence, Frances could start moving more northwesterly, he added.

"That second high pressure system could be strong enough to steer the storm westward into South Florida," Letro said, "or it could be weak enough that the storm just blasts right through it and heads up to Georgia. The more likely scenario is something in between, which covers a lot of area."

Some of the tools National Hurricane Center forecasters use in predicting where storms will head are computer models prepared by different meteorological sources and known by their initials. For instance, the GFDL model is prepared by a federal agency, the Geophysical Fluid Dynamics Laboratory. UKMET stands for the United Kingdom Meteorology service. GFS (AVN) is the Navy, Letro said.

Forecasts and storm updates issued by the National Weather Service frequently make reference to these computer models and how they change, or flip-flop, from update to update.

"The fact is that how a hurricane interacts with the environment around it is a very delicate balance of forces," Letro said. "The slightest change in those forces, whether weaker, stronger, faster or slower, can have a great deal of effect on how the computer model handles a hurricane and our data network is simply not dense enough to capture all the information that a computer model would need to make a really specific forecast."

He said that a computer model is a simulation of the atmosphere.

"We can simulate the atmosphere of a hurricane inside a computer but we cannot duplicate it," he said.

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