|Published Tuesday, May 28, 2002 in the San
Jose Mercury News
Warm regions see hurricanes begin to churn
Special to the Mercury News
Now that tornado season is well under way in the Plains and Midwest, it's time to turn our attention to the tropics and the beginning of hurricane season. In the Atlantic, Caribbean and Gulf of Mexico, the official start of the season is June 1st and it continues through the end of November, peaking in early September. Along the coast of Mexico and in the Eastern Pacific the hurricane season began in mid-May and will end in mid-October with maximum activity at the end of August. Hurricanes are massive rotating bands of thunderstorms in the tropics around a deep area of low pressure. They derive their energy from the warmth of the tropical oceans and can have winds in excess of 150 miles per hour affecting hundreds of square miles. Hurricanes begin as tropical disturbances with light winds spiraling clockwise into a weak area of low pressure. When the wind speeds are from 23 to 39 miles per hour, the weather activity is classed as a ""tropical depression'' and then becomes a ""tropical storm'' when its winds are 40 to 73 miles per hour. And when the winds reach 74 mph or greater, it officially is a hurricane. Like tornadoes, hurricanes are classified by wind speed that is estimated by the amount of damage they produce. The Saffir-Simpson scale rates storms on a scale of 1 to 5 with a Category 1 storm having winds of 74 to 95 mph and a Category 5 has winds higher than 155 mph.
While most people relate hurricanes to their strong winds the greatest amount of damage and loss of life comes from the torrential rains and resultant flooding that accompanies these storms. In the United States, 82 percent of the nearly 500 deaths associated with tropical storms and hurricanes since 1970 are from flooding and most of these are inland in fresh water. This was illustrated by Tropical Storm Allison in June 2001, whose strongest winds were only 50 mph, flooding from this storm did over $5 billion in damage and killed 24, mostly in and around Houston where over 36 inches of rain fell.
These massive storms that we call hurricanes go by other names in different parts of the world. In the Western Pacific they are referred to as typhoons and in the Indian Ocean as tropical cyclones. Each of these regions has a different naming convention for individual storms. In the Atlantic the names alternate between male and female and include names from the Anglo, Spanish and French cultures of the area, while the Eastern Pacific Storms have names derived from English and Spanish.
To find out more about hurricanes and to
track this season's storms go to
WEATHER SURVEY: I have put
together a brief, albeit unscientific, survey to gauge of peoples'
perceptions of the weather and weather forecasting. Please take a
minute or two to complete it and share it with your friends, colleagues
and family members so we can get as big a sample as possible. I will
publish the results in mid-June. The survey is online at
A. This is actually one of the classic questions that meteorologists get asked and spent probably way too much time pondering. They struggle with whether you impact more droplet as you run faster even though you are exposed for a shorter period of time? Or do more drops hit the front of a person that their head and shoulders?
There have even been a number of studies to ""scientifically'' calculate whether it's better to run or walk to shelter. One of the simple studies had people wear a piece of cardboard over their heads and in front of them as they walked or ran through the rain and then the number of drops that marked the cardboard were counted. A more detailed effort from the National Climatic Data Center in Asheville, North Carolina had their experiment subjects wear identical moisture absorbing clothing as they walked 100 yards at 3 mph and run the same course at the same at 9 mph. They clothing was then weighed to find out how much water was absorbed. They found that speed helps ... the person who ran the course absorbed 40 percent less water than the walker!
And of course someone, with way too much time on their hands, has put up a website to calculate how wet you would get based upon your size, speed and the rate of rainfall. See http://www.dctech.com/physics/features/physics_0600a.html
Jan Null, founder of Golden Gate Weather Services, is a retired Lead Forecaster with the National Weather Service. Send questions to him c/o WeatherCorner, San Jose Mercury News, 750 Ridder Park Drive, San Jose, Calif. 95190. You also can telephone questions at (510) 657-2246, fax them to (510) 315-3015 or e-mail them to email@example.com. Please indicate in your e-mail what city you live in.