Tuesday, March 11, 2008

Monsoon Season -- Now It's Defined

Well if you have any knowledge about the climate of the desert southwest and the southern Rockies, you know about the annual monsoon season.

Yes, there really is a monsoon -- just like the one each year in India and vicinity.

A monsoon has nothing to do with rain or thunderstorms, although it creates both.

The definition of a monsoon is a seasonal shift in the wind pattern, plain and simlpe.

Here in the US, this season wind shift brings southwesterly winds up from the Pacific Coast of Mexico, with moisture sometimes reaching as far north as southern Idaho and Wyoming -- maybe further north on a good day.

The North American Monsoon, or Mexican Monsoon, is declared active each year once Phoenix records a daily dewpoint of 55 degrees or higher on 3 consecutive days, and Tucson sees a 54 degree dewpoint or higher on 3 consecutive days.

The average start date is right around July 3. The earliest start was on June 17, 2000 and the latest was July 25, 1987.

Well that is all history starting this year. The National Weather Service has decided it is in the best interest of safety for all who live in the monsoon region to define a "season" for the weather activity, much like we have a defined hurricane season.

Which if you think about it, really isn't a bad idea. It gives those who live in the area a little time to prepare before the season gets underway.

Thunderstorms that form during the monsoon are often short-lived but intense, and because they form over areas that are typically dry, the result is a lot of unexpected flash floods.

Lightning is also a huge hazard. These aren't the type of thunderstorms that typically produce tornadoes, although it can happen, esp. the further away you get from the actual core of the monsoon, such as in eastern Colorado.

Beginning this summer, the annual monsoon season will start on June 15 and run through September 30.

1 comment:

  1. Hey Chris, thanks for visiting the team blog.

    I met Tim Samaras, while I was chasing in SD last year. He was doing some sort of hail experiment. Very smart man. I passed Roger Hill in Iowa, chasing a stubborn wall cloud that wouldn't produce. He and his crew stayed on it while we decided to enjoy some DQ and quit chasing our tails. I talk to Tony from time to time, love how he just flies to wherever the storm is. I talked to Verne a while back... haven't really caught up with him in a while. Sounds like we have some common acquaintances. Cool.

    My personal weather blog is updated more frequently than the Weather Brigade blog you visited. You can check out my blog at www.dewdropweather.com. I talk a lot about CoCoRaHS on there, since I will be the volunteer county coordinator when Georgia goes live in May.