“Monsoon” rages in Arizona; “Stupid motorist law” means you may pay for your own rescue

Arizona Flash Floods: Monsoon rages

Around the world and herein the USA, different "storm seasons" cause local meteorologists and newsrooms to ramp up coverage.

In Florida and the Gulf Coast it's hurricane season. In Minnesota it may be spring severe weather season, or winter storm season.

In Arizona, it's all about the "Summer Monsoon" this time of year.

Summer Monsoon in full swing in Arizona. Image KTVK

On Monday, torrential rains flooded the town of Eloy about halfway between Phoenix and Tucson. That was after storms caused severe flooding in the Phoenix area last weekend.

What's a "monsoon" anyway?

When I arrived in Tucson as the chief weather guy for the ABC TV affiliate in 1997, I learned about this crazy weather phenomenon called "The North American Monsoon."

Each July, upper level winds shift in Arizona and pump in tropical moisture from the Gulfs of Mexico and California. Intense heat causes huge storms to billow over the mountains, and roll into the valleys with heavy rain...and flash flooding.

Monsoon moisture sources. Image: Tucson NWS

The hard ground just can't soak up the intense downpours, so normally "dry washes" quickly fill with raging water creating instant rivers. It's a dangerous trap for unsuspecting...even "stupid motorists." "Can I make it through the flood?"

In the 90s Arizona passed the so called "Stupid Motorist Law." Bypass warning signs and intentionally drive into a flooded wash and need to be rescued? Not only does your life flash before your eyes, you get a ticket and have to pay the cost of the rescue...up to $2,000! Even with the law, hundreds of Arizona motorists drive into flooded washes each summer.

Monsoon rocking in 2013:

This has been a banner year for monsoon storms in Arizona so far. Several locations have picked up anywhere from 2" to 7" of rainfall in the past couple of weeks.

Image: Tucson NWS

One of the best measures for the strength of the monsoon is the dew point reading in places like Phoenix and Tucson. A dew point over 54 degrees is considered the threshold for an active monsoon. Take a look at the chart below and you can see dew points have been running well into the 60s this month.

Image: Tucson NWS

Much of Arizona receives more than half of their annual rainfall during the summer monsoon. The cooling rains are a welcome part of life in summer, and bring the parched brown desert back to life with some amazing shades of green and flowering trees and shrubs like the beautiful ocotillo.

Ocotillo in bloom. Image: Arizona Sonora Desert Museum via Warren Lynn

Theres' an old saying when an unexpected visitor arrives in Arizona. "You're as welcome as rain." It's a compliment. Rains from the summer monsoon are a welcome, and sometimes unexpected visitor in the desert.