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Finance Department (Login Finance_Department)
Veteran Member
Posted Jun 16, 2009 3:13 AM
http://ktar.com/?nid=388&sid=1179639
Updated 17 hours, 21 minutes ago.
The annual monsoon has officially started, although it will be days before the dust storms, thunderstorms, rain and lightning blast into the Valley.
The summer rainy season used to start and end, based on dew point readings, but last year it was decided to do it by dates -- from June 15 to Sept. 15.
Forecasters say this year's monsoon could kick into high gear at the end of June and be more powerful that normal. The key ingredient, said Arizona State University climatologist Randy Cerveny, is heat.
"You usually have to have a lot of hot weather to fire up the moisture, fire up the monsoon thunderstorms," said Cerveny.
One of the strongest storms in years packed a big punch last August when a microburst hit, tearing roofs off homes, uprooting trees and downing power lines acorss the Valley.
Cerveny said a microburst "is in essence a little air bomb that blows up out of a storm, then blasts down and hits the ground like a bomb blast."
It's not clear how this monsoon will shape up. Doug Green with the National Weather Service said early indications were that it would be a good rain producer, but now he's not sure.
"The confidence in the summer forecast for the Phoenix area is probably not as high as it was a month ago, and, even if it was confident, there's a typical variability in the amount of precipitation that occurs over the Phoenix metropolitan area, across Maricopa County," Green said.
"Last summer was a good example -- when Sky Harbor was a lot wetter than it usually is, but other sites in the Valley, not more than 5 or 10 miles to the west or to the north, were well below normal."
Green said it's important to remember that wind storms and lightning, along with extreme heat, can be deadly.
"Just be careful out there because thunderstorms -- no matter what you call them and whether it's a wet monsoon or dry monsoon -- can be very hazardous."
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