Thunderstorms may cool heat wave

KINGMAN ­ Today marks the eighth consecutive day Kingman is under an excessive heat warning issued by the National Weather Service office in Las Vegas.

But relief may be on the horizon. Weather experts say the area has a chance of isolated thunderstorms Friday through Sunday.

A high-pressure system has remained stationary over Utah since July 10 at a time of year when it usually parks itself over the Four Corners region, according to Jim Harrison, a staff meteorologist with the NWS.

"High pressure in the upper atmosphere was sitting over southwest Utah last week and continues to control our weather," said Ken Clark, a meteorologist in Rancho Cucamonga, Calif., with AccuWeather. "It has been over 100 degrees every day since July 11.

"The heat will abate somewhat Thursday, Friday and Saturday. But the humidity will rise and increase the likelihood of thunderstorms, especially Friday and Saturday."

Mortality statistics derived from heat-related deaths prompted the NWS to issue heat warnings. The criteria changes during different seasons, but a daytime temperature of 110 or higher at McCarran Airport in Las Vegas is the threshold number for issuance of a heat warning in July, Harrison said.

"Hurricane Emily just went through the Yucatan (peninsula of Mexico)," Harrison said Monday. "It will continue tracking westward across northern Mexico and we'll get some of its moisture (by the weekend).

"We're still looking at a temperature (in Kingman) of 102 on Friday and then dropping into the mid-90s for the weekend. Signs are we will not return to excessive heat levels (next week), and probably will rebound closer to normal temperatures."

The average maximum high temperature for July in Kingman is 95.9 degrees, according to data supplied by the Arizona State University Office of Climatology. Rainfall for the month averages 1.08 inches.

Temperatures in northwest Arizona are expected to remain at or above normal for the next 90 days, Clark said.

Average maximum and minimum temperatures here are 93.9 and 67.4 in August, and 88.1 and 60.8 in September. Rainfall averages 1.44 inches in August and about half that amount at .73 inches for September.

Dew points, the temperature at which dew begins to form or water vapor condenses into liquid, have been in the mid-30s in recent days. Clark said that by Thursday they will climb into the mid-50s or low-60s.

"Those figures are typical for the monsoon," Clark said. "But it doesn't mean there will be thunderstorms every day.

"The amount of moisture for them ebbs and flows. But later this week and into the weekend there is reason to believe you'll get scattered thunderstorms and a day or two may have more than that."

Forecasters in Phoenix define the start of the monsoon as the time when dew points reach or surpass 55 degrees for three straight days. The average start date for the monsoon in Phoenix is July 7 and between July 10-14 for Kingman.

"It's hard to say when the monsoon may start in your area," Harrison said.

"Much of it depends on what happens after the remnants of Emily pass through and if we trust the models out that far.

"It looks like the moisture influx from Emily will cut off and we'll get into a westerly wind flow. The flow normally is south or southeast during the monsoon."

The models Harrison spoke of are computer mathematical simulations of the atmosphere based on available data. One model projects a westerly air flow beginning July 27 and another indicates a southeast flow will be experienced.