Hurricane forecasting techniquesimprove
MIAMI, (UPI) -- Hurricane forecasters cantell where a giant storm is going with more accuracy than everbefore. The problem is figuring out how bad the news is goingto be when it gets there.
Predicting a storm's direction and speed,known as the track forecast, has improved by about 1-2 percenta year since Hurricane Andrew mauled south Miami-Dade County,Fla., on Aug. 24, 1992, forecasters at the National HurricaneCenter in Miami said.
"We have a success story here,"said Max Mayfield, director of the center. "As we look backover the last 10 years, we have really had significant improvements.There isn't any one thing, but there have been a lot of littlethings giving us a better track forecast."
Among them are 16-inch-long radar probesknown as dropwindsondes. They are dropped into storms to measurepressure, wind speed, direction and temperature to provide a technologicalpicture of a hurricane at various altitudes.
The data is fed to computer program thattries to predict what a storm will do. The most promising softwareis a more powerful version of the Geophysical Fluid Dynamics Laboratorymodel, but there are several others that forecasters use. Andthey are run on faster and faster computers.
Part of forecasting has become figuringout where the computer programs agree and why or why not.
But Mayfield said the models still aren'tvery good at predicting rapid intensification.
"One of the biggest limitations isthe intensity forecasting. On average, we do pretty good, butwhat we don't do a very good job with is rapidly intensifyinghurricanes."
He said that is critical. Although Category3-5 hurricanes, which have winds of 115 mph or more, amount toabout 20 percent of the total, they cause 80 percent of the damage.
"Most of them go through rapid intensification,which we don't understand very well," he said.
He said research on the phenomena has beenstepped up, and he is optimistic there will be improvements.
The hurricane center also has added sophisticatedaircraft including an ER 2 which can investigate hurricanes athigh altitude, a Gulfstream IV Jet and a DC-8. In addition thecenter has the use of hurricane hunter aircraft belonging to theAir Force Reserve and the National Oceanic and Atmospheric Administration.
The aircraft and even more sophisticatedinstrumentation could be the answer to the intensification problem,Mayfield said.
In addition, improved Doppler radar cangive forecasters more detail and the winds, rain and track ofa storm and improved imagery from satellites now provide moredetailed information.
For the last two years, the center has beenexperimenting with longer range forecasts of up to five days ratherthan the customary three. They will go public as soon as nextyear.
That would give residents a little moretime to prepare and even evacuate.
Forecaster Lixion Avila told the "AndrewPlus 10" meeting at Florida International University thissummer, that last year was the best for accuracy over the last10 years.
"In fact, in 2001 the errors were significantlyless than over the last 10-year period," he said.
The hurricane center uses Hurricane Michellelast year as an example. It was the best of the season.
"When Michelle was 36 hours off Florida,forecasters predicted the path within 86 miles of its actual course.The average error is 115 for that time period.
Forecasters said it is still possible fora hurricane to swerve by as far as 100 miles in the 24 hours beforelandfall.
Once again they were caught by surprisewhen Michelle exploded from a Category 1, with winds under 96mph, to a Category 4, with winds of more than 131 mph, in the30 hours before it hit Cuba.
Andrew was also believed to be a Category4 at the time, but it had intensified well before it made landfall,giving forecasters a cushion.
"The track forecast wasn't that bad,and the intensity forecast wasn't that bad," Mayfield said.
But with that kind of power and fury, therewasn't much that could be done. Now there is solid evidence --much of it supplied by the dropwindsondes -- that Andrew's topsustained winds were more than 165 mph when it hit land. WithSaturday's 10th anniversary approaching, it was reclassified asa Category 5 storm Wednesday.
Mayfield warns that improved forecastingnotwithstanding, if individual residents of an area that is hitby a hurricane are not prepared, all can be lost.
"We are not totally prepared,"he said. "The message from the National Hurricane Centeris consistent. We urge every individual to have a plan beforea hurricane hits."