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Hurricane Forecast
11/04/2002
Listen in RealAudio 
Hi, I'm Bryan Yeaton for The Weather Notebook.
Residents of the coastal southeast breathed a small sigh of relief when hurricane guru William
Gray announced early in August that he had changed his mind; instead of the 11 named storms -
including 2 major hurricanes - he had predicted earlier in the year, Gray now called for a
total of nine named storms, only one of which was likely to develop into a major hurricane.
Why the new numbers? Blame it on the El Nino that's now gaining strength in the tropical
Pacific.
El Nino stirs up all kinds of havoc with the world's weather - drought in Australia, winter
warmth in Minnesota, storms along the California coast. One rather subtle, but ultimately
potent, side-effect of El Nino is a shift in the location of a kind of atmospheric turbulence
known as vertical wind shear which refers to winds blowing at different speeds or directions
at different altitudes. In a normal year, massive thunderstorms associated with deep
convection spin up vertical wind shear in the western Pacific. But during an El Nino, this
atmospheric kink shifts eastward to roil the air over South America and the Atlantic basin.
When developing hurricanes encounter vertical wind shear they fizzle since westerlies aloft
knock the tops off the thunderstorms that pump in their energy. Not all Atlantic hurricanes
succumb, but enough should opt out that Dr. Gray decided to revise his seasonal
outlook.
But it may not be such a slow season at the National Hurricane Center after all. The same
pattern that suppresses Atlantic hurricanes tends to whip them up in the eastern Pacific. Once
again, we can blame it on El Nino.
Today's writer was David Laskin. For links on Dr. Gray and the 2002 hurricane season, go to
our website at www.weathernotebook.org. Thanks to Subaru and The National Science Foundation.
Today's Links
World Wide Tropical Cyclone Names
http://www.nhc.noaa.gov/aboutnames.shtml
Dr. Gray Lowers '02 Forecast
http://www.pbrla.com/HURRNEWS-02/053102.html
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