2011 monsoon season arrives
Fifty-fifty chance of wet or dry year
VERDE VALLEY - This is the time of year when most of us look to the sky, hoping to see those billowing white clouds turn black and the summer monsoon begin.
On July 4 and 5, it came.
It was barely a tenth of an inch in Camp Verde, but the rain gauge at Tuzigoot National Monument showed nearly an inch.
According to Dave Vonderheide, spokesman for the National Weather Service in Flagstaff, there is a 50-50 chance that this year's monsoon will deliver above or below average monsoon rains.
"This summer we have close to normal Pacific Ocean surface temperatures, the factor that determines if we are having el Niño and la Niña year.
"Our climate predictions like to have those, because when el Niño or la Niña effects are in place they make the weather in the Southwest somewhat predictable," Vonderheide says.
Salt River Project is saying exactly the same thing this year.
"It seems to be one of those years where it looks like a toss up," says SRP spokesman Tim Skarupa, "It looks like an equal chance of above, below or normal rainfall."
The National Weather service is, however, predicting below average precipitation this year and above average temperatures for July, August and September.
"I think that is being based on the long term drought. However, the drought is improving. Pretty much from Prescott, Cottonwood and Flagstaff and west we're not showing any drought at all and to the east it is improving," Vonderheide says.
The Southwestern monsoon is the result of a change in the winds. In late May and early June we experience southwesterly winds. They are typically hot, dry and known to cause small wildfires to become big ones.
Then in late June, as the North American landmass heats up, the jet stream recedes north, the winds begin blowing from the south and southeast, bringing in subtropical moisture from the Gulf of Mexico.
Traditionally, the summer monsoon began on Fourth of July and went through Labor Day.
But statistical data shows that precipitation begins to steadily increase beginning in mid-June and not tapering off until the end of September.
According to the NWS 30-year average, the weather station at Tuzigoot National Monument, located between Clarkdale and Cottonwood, measures 3.76 inches of rain from July through September.
The station at Montezuma Castle, between Camp Verde and Beaver Creek, averages 5.39 inches of rain during the same period.
"There appears to be a dry spot between Cottonwood and Page Springs, but as you get closer to the rim the average monsoon rainfall reaches 7 to 10 inches," Vonderheide says.