Hurricane Series: Forecasting
by: Rod Rice, June 4, 2007 5:06:00 am
There are two types of hurricane forecasts, one that predicts the kind of hurricane season to expect and the other the development of specific cyclonic events. The former is done, among others, by Colorado State University Hurricane researcher Dr. William Grey. One of his main tools is historical data.
"We go back about 60 years and on some things a hundred, a hundred and twenty years, and just see when certain conditions occurred were these active or inactive years."
Water temperatures in the Atlantic and Pacific Oceans play an important role too. A warm Atlantic and a cool Pacific can mean an active hurricane season. When El Nino occurs and warms the Pacific Ocean it tends to mean there will be fewer hurricanes in the Atlantic Ocean and the Gulf of Mexico.
Joe Bastardi is a hurricane specialist with Accu-Weather, a private forecasting company. He thinks there may be some natural phenomenon that can affect the number of hurricanes. For example he says that in 2004 there was an El Nino and still Florida got hammered.
"There are probably pulses that go on in the atmosphere that try to balance out things, where if you had so much activity one year chances are nature tries to counter that some way or another. To produce all those hurricanes you need a tremendous amount of upward motion. The following year there may be compensating sinking air in the very same place the upward motion was. We don't know the affects of the winter season may have affect the over all circulation in the tropics."
So what is known and what is not known can sometimes combine to make seasonal forecasts way off the mark as they were last year.
Hurricane forecasting becomes more important to most of us after a storm has formed and is moving toward land. That's when forecasters start gathering and sifting through data, all kinds of data, in fact when asked what tools they wish they had they all basically say anything that will give them more data. That's because for all that is known about hurricanes there is a lot that is not.
"One frontier we don't know about is how a tropical cyclone forms."
Eric Blake is a hurricane specialist with the National Hurricane Center. He says forecasts will improve with more reconnaissance flights and better computers and computers models.
Chris Hebert is a hurricane specialist with Impact Weather, a private firm based in Houston that forecasts the weather for businesses and provides the daily forecasts for Houston Public Radio. He says meteorologists are getting better at predicting the tracks of a storms but intensity is still difficult because there is not enough data about what is happening in the center of the storm.
"Predicting the inner core of a hurricane and how it's fluctuating over time requires a lot more detail data from around the core of a hurricane. We can't get that without a lot more instrumentation inside the hurricane."
There will be an effort this year to use exiting Doppler radar signals along the Gulf and Atlantic coasts to gather more information about storm intensity thanks to some new math models. Radar is a straight beam while the earth is curved so the farther the storm is from the radar the higher above the surface the data is collected. The plan is that the math will accurately extrapolate what I happening at the surface from the data collected higher up. The downside Hebert says is that but radar only travels about 150 miles.
"So were talking about 8-12 hours before the hurricane makes landfall, so you're not going to be able to use that data in terms of helping with evacuations, evacuations would have been done days in advance, but it will help the coastal residents know that as the storm is beginning to make landfall, how strong it is around the core."
Better computers, more reconnaissance flights and the next generation of satellites will funnel more, and it is hoped better, data to meteorologists as they work to tell us where storms are headed and how strong they'll be when they get there.
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