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Hurricanes 'stun experts'
20/10/2005 10:35 - (SA)
Miami - Hurricane Wilma already has broken a record, becoming the strongest such storm in the Atlantic, but what is even more stunning is how it surged to monster-system strength in just a few hours, a nightmare for scientists still not clear on how hurricanes grow.
National Hurricane Centre director Max Mayfield has said: "My worst fear is to go to bed preparing for a Category One or Two hurricane and waking up to find a Category Four or Five."
And that is precisely what happened with Wilma overnight on Tuesday into Wednesday.
When many went to bed in Miami late on Tuesday, Wilma was already a Category Two system packing winds of 175 kilometres per hour.
Six hours later, it was a menacing top-level Category Five storm with sustained winds of 280 kilometres per hour, able to inflict massive destruction.
Its barometric pressure sank from 945 millibars to 882, breaking a record that dated back to Gilbert in 1988 which had hit 888 millibars.
And though exceptional, it is not the first time this has happened.
In 1995 Opal surged from a Category One to a Category Four on the Saffir-Simpson scale in just one day.
In 1995 Bret rose from a tropical storm to a Category Four hurricane in a fairly fast three days.
Delicate balance can be swayed dramatically
Predicting just how much a hurricane will grow, and over how much time, for now is an impossible task given the huge number of factors that affect it: ocean temperature, humidity and wind currents, to mention just a few.
The delicate balance can be swayed dramatically by just tiny shifts in the factors in question.
"We understand the main ingredients, we just don't know how they interact at the same time. You could have one or two things that are not favourable, yet the other three or four are favourable and you could still get rapid intensification," said Nick Shea, professor of Meteorology and Oceanography at the University of Miami.
US researchers have been trying to decipher how specific variables play into storm intensification but it has been slow going.
"What is difficult is to judge when to go out and make the measurements, because once you get out the storm can rapidly develop...you may miss the opportunity," Shea explained.
Another scenario researchers are giving greater attention to is the so-called "Loop Current" of warm water which circulates from the Yucatan strait to the Gulf of Mexico to the Florida strait.
A hurricane normally cools water as it passes but in the Loop Current scenario, the more the storm churns up the sea, more warm water is driven up to the surface, which fuels the storm like a sort of high octane gas.
Forecasts are "always getting better but there's always going to be an element of surprise, you have to plan for these things" said Kevin Trenberth, of the National Centre for Atmospheric Research in Boulder, Colorado.
"We are hoping to improve intensity forecasts during the next 10 to 20 years much like they did in hurricane track forecasting, which in the 1980s and early 90s significantly improved."
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