Monsoon season gets earliest start in valley

Friday, June 23, 2000 | 11:19 a.m.

S. Nevada floods

The National Climatic Data Center in North Carolina recorded 49 floods from January 1993 through February 2000 in Southern Nevada. Four people died and nine were injured in that time period. The floods caused an estimated total of $34.8 million in damages.

Major floods in the Las Vegas Valley recorded by the National Weather Service:

As Southern Nevada's mountains lit up from flashes of lightning Thursday night, the National Weather Service declared the Southwest monsoon season had officially started, the earliest one on record.

The shift in summer winds moving north through Mexico came a month early, according to weather experts.

The weather forecasters in Las Vegas confirmed a gust of 32 mph about 8 p.m. Thursday as a towering thunderhead disintegrated south of the Las Vegas Valley.

Although no thunderstorms erupted in the valley Thursday, it was a different scene in Lee Canyon, northwest of Las Vegas.

U.S. Forest Service rangers reported golf ball-sized hail stones that forced them to take cover about 2:30 p.m. Thursday afternoon, Forest Service spokeswoman Betty Blodgett said.

The rangers in Lee Canyon also reported numerous lightning strikes and some rain, she said.

Hot, humid winds fired up thunderstorms on June 1 in New Mexico, according to the weather service.

Then the summer weather action moved to Tucson, Ariz., on June 17.

Las Vegas weather forecasters called for a chance of showers or thunderstorms through this evening before the moisture retreats for a few days.

The early appearance of the monsoons did not surprise David Mitchell, an atmospheric scientist who studies the worldwide climate at the Desert Research Institute, the University of Nevada, Reno's research arm. The institute also has a research center in Las Vegas.

Mitchell has been watching the Pacific Ocean's surface temperature south of Baja, Calif., a spot no one else has tracked. And the ocean tells a consistent tale of stormier weather. Unlike the erratic weather patterns from El Nino, the hot water patch in the Pacific and its counterpart La Nina, with attending cold water, the ocean's surface temperature appears to predict stormier summers more accurately.

"I told them it was going to be an early year, but I didn't think it was going to be this early," Mitchell said of the Southwest monsoons.

Last year the surface temperatures reached about 82 degrees in early July and the monsoon began roughly on schedule in mid-July, Mitchell said. This year, he said, the ocean temperature has been that high for the past two weeks.

Mitchell tracked the temperature record of the ocean's surface over 20 years, relating stronger southwestern monsoons with the higher temperatures.

Remnants of Hurricane Carlotta also fed the moist flow from the Gulf of California this week. The Pacific's second hurricane of the season killed six people in Mexico on roads damaged by mudslides and forced authorities to evacuate both coasts earlier this week.

Carlotta was downgraded to a tropical storm late Monday.