Experts left puzzled as Katrina picks own path
August 30, 2005
Katrina has been a puzzle from the beginning.
For starters, the storm grew out of the remnants of a tropical depression that never got its act together.
Now, after speeding along when it was supposed to slow down and jogging south when it was supposed to head west, Katrina could be poised to develop into a menacing Category 4 hurricane.
The storm's unlikely genesis is a classic reminder that for all the advanced science used in predicting the path and intensity of these violent storms, hurricanes can still confound the most sophisticated weather experts.
"The unique features of this storm are that first of all it went from nothing, a disturbance, not even a depression to a hurricane in two-and-a-half days," said David Nolan, an assistant professor of meteorology at the University of Miami.
"Then it moved southwest, which is unusual in that part of the world. And even though it was a Category 1, it did a lot of damage and the reason for that was that storm started to intensify pretty quickly as it approached shore. And a storm that intensifies as it hits land will do more damage than a storm that is stronger."
The question now is whether Katrina, which already has killed seven people and left about 1-million customers without power, will continue its rebellious streak.
It started out nearly two weeks ago as Tropical Depression 10, located hundreds of miles east of Antigua. Then it fizzled.
Near the Bahamas, the system joined with another disturbance and gained strength. Hurricane forecasters debated whether it was still Tropical Depression 10 or a new storm.
On Aug. 23, it became Tropical Depression 12.
Air Force Reserve squadron planes began flying through the eye every three hours, moving 105 miles from one end of the storm to the other, dropping cylinders that took snapshots of the storm as they fell 2,000 feet per minute.
By Wednesday, Katrina's winds had reached 45 mph, and the storm was predicted to hit somewhere between the Florida Keys and Vero Beach. Forecasters predicted as much as 15 inches of rain in spots.
"At first it was pretty ragged and then it built up quick," said Maj. Chad Gibson, an aerial reconnaissance weather officer with the 53rd Weather Reconnaissance Squadron in Biloxi, Miss.
Water around the Bahamas is typically no deeper than 35 feet. But once a storm moves west and hits the Gulf Stream, things can change quickly.
The ocean can be 14,000 feet deep in places, giving the storm enough warm water to fuel it, said Jack Parrish, a flight meteorologist with the NOAA Aircraft Operations Center at MacDill Air Force Base.
Forecasters thought Katrina would slow down considerably once it reached the Gulf Stream. It didn't. It kept moving at 6 to 8 mph.
One of the NOAA reconnaissance planes flew through the eye about 3:30 p.m. Thursday and measured winds of 75 mph.
Forecasters upgraded Katrina to a Category 1 hurricane.
It had gone from a tropical depression to a hurricane in two-and-a-half days.
What's more, a storm that on Wednesday was forecast to hit Florida early Friday morning arrived just after dinnertime Thursday, bearing winds of 80 mph.
Hurricanes rarely move south. They are drawn to the north like metal to a magnet.
But in an unusual event, a system of high pressure known as the Bermuda High pushed Katrina to the south.
Forecast to move west, Katrina instead moved southwest through Miami-Dade and into the Everglades, about 80 miles off the original track.
Along the way, the storm dumped anywhere from 2 to 12 inches of rain on areas of Miami-Dade and Broward counties.
Usually the northern edge of hurricanes get the severe thunderstorms. Again, Katrina had a surprise. It was the southern edge that suffered most.
"As the storm came into Miami-Dade, one large rain band formed on the south and southeast side and as the storm moved slowly to the west, it didn't have time to wrap all the way around the north side of the storm," said Tom Warner, senior meteorologist with the National Weather Service in Miami-Dade.
"It was concentrated over the southern part of Miami-Dade County. That's why so much rain fell there."
Since Katrina jogged south, it re-entered the gulf at the southern tip of the Florida peninsula. Rather than getting worn down by a long westerly trek over the peninsula, the storm took a shortcut, heading into the gulf's 90-degree waters - exactly what the storm needed to re-energize into a major hurricane
"Actually it did exactly what it was forecast to do," said Lt. Jennifer Pralgo, a meteorologist with the National Hurricane Center in Miami. "It came in between Miami-Dade County and Palm Beach County."
Of the 12 different computers models the National Hurricane Center uses to predict storms, only one predicted Katrina would move south, said Nolan, the University of Miami assistant professor.
That model had been wrong earlier in Katrina's progress, so forecasters were apt to discount it.
"The result was quite a bit different than what hurricane forecasters
were saying was expected to happen even within the last six hours, but everybody
was warned," Nolan said. "All of Miami-Dade was under a hurricane
warning, so you can't fault the Hurricane Center for that."