When Is a Monsoon Not A Monsoon?
Arizona's monsoon season is the worst named weather related event in history. The name is so misleading, conjuring up images of torrential rain, high winds and massive flooding, that the National Weather Service has proposed changing the name of the annual weather pattern to "summer thunderstorm season". Even that name may not be entirely accurate since dust storms, accompanied by thunder, lightening and high winds but not always rain, are the most common weather event of the summer.
Technically, a monsoon is any seasonal reversal of wind direction. The best examples of this phenomena can be found on the Indian sub-continent, however, it also occurs in Mexico. Arizona lies on the northern fringe of the Mexican monsoon area and our winds aloft, which come from the west and northwest most of the year become more southerly and southwesterly during the summer. This change in wind direction brings moisture from the Gulfs of Mexico and California as well as the Pacific Ocean to the area causing upper level disturbances and thunderstorms. Unfortunately, one of the factors contributing to Arizona's decade-long drought is that these thunderstorms don't bring much rain and what rain does make it to the Valley often falls in microbursts with severe, even damaging wind gusts.
In Phoenix, the annual monsoon season begins when the dew point average 55+ degrees Fahrenheit for three consecutive days. This usually happens sometime in early July. Despite several thunderstorms moving through the area, the 2007 monsoon season has not yet started officially. Monday and Tuesday's dew point climbed above 55 but Wednesday's only reached 51 and Thursday's is forecast at 54.
Whether it's officially the monsoon or not, summer storms are quite an experience. Curtains of blowing sand and dust can envelope outlying areas with little warning. Microbursts and thunderstorms can create flash floods that course through areas that have not had any rain. Visitors are advised not to drive into dust storms or flooded roads. Locals will, but what do you expect from people who will allow you to carry a gun into a bar but not a cigarette? Golfers and swimmers are also advised to take cover when they see lightening.
Do you have a summer monsoon story to tell? Please share it, since the only way to understand this unique weather condition is to experience it!
