THE FIRST HABOOB OF THE SUMMER SEASON

Saturday, July 30, 1030pm:

A massive haboob moved west across the deserts of Arizona Friday night, finally striking the Coachella Valley around 2:30-3:00am early Saturday. Visibility dropped to less than a half mile for several hours, as the massive cloud of dust and sand moved across our area. A thin layer of dirt was left on streets, trees, cars and rooftops, and hazy skies stuck around the rest the day, as the dust slowly thinned and clouds moved overhead.

This was a particularly large haboob. It affected a huge area, originating in the Phoenix area, then spreading to the west into California, as well as north into the Las Vegas area and south into northern Mexico near Mexicali. Here's how things progressed yesterday:

1. Between noon - 3pm Friday, large thunderstorms formed in the mountains to the north and east of Phoenix and Tuscon, Arizona. The storms began moving to the west/southwest toward the lower deserts and populated areas.

Notice the hailstones covering the ground along this stretch of I-17 in the deserts north of Phoenix.

Notice the hailstones covering the ground along this stretch of I-17 in the deserts north of Phoenix.

2. Between about 4:00-8:00pm, the storms intensified and began to combine into larger cells as they continued to move west and approach Phoenix from the northeast, east and southeast. Observations indicated outflows of 40-60 mph were beginning to descend into the Phoenix area, out ahead of the major thunderstorms also heading to the west. Dust storm warnings were issued for Phoenix and the surrounding cities and deserts to the west.

As the storms began moving to the west, the National Weather Service issued Dust Storm Warnings, as observations began to indicate severe wind gusts beginning an organized haboob across the Phoenix area.

As the storms began moving to the west, the National Weather Service issued Dust Storm Warnings, as observations began to indicate severe wind gusts beginning an organized haboob across the Phoenix area.

Zero visibility along I-10 northwest of Tucson. Hazardous driving conditions.

Zero visibility along I-10 northwest of Tucson. Hazardous driving conditions.

3. Between 8:00-9:00pm, the storm envelops the Phoenix area. Winds gust to to 70 mph at Sky Harbor airport, and nearly a half inch of rain falls in less than an hour. Temperatures drop from 108 to 78 degrees in 60 minutes, and the humidity rises from 18% to 84% in 30 minutes. Visibility drops to 3.5 miles in blowing dust just ahead of the heavy rains, indicating the leading edge of the haboob that is gaining strength and heading west. Check out the observations from Phoenix during this time frame.

4. Between 8:00-9:00pm, the storm continues to gather strength, and additional reports of zero visibility are coming in from area web cams and on Twitter.

5. Between 9:30-10:00, the storms slam cities and communities to the west of Phoenix and Tucson. Gila Bend reports dense dust and wind gusts to 89mph, followed by torrential thunderstorms and 3/4 of an inch of rain that falls in less than 60 minutes. Visibility drops to only 0.25 mile. Check out the observations from Gila Bend that show the impressive ENE winds that helped fuel the haboob.

6. A photo of the dense wall of dirt appears on social media, looking east as the massive haboob moves toward the photographer, not far from Gila Bend, at the height of the storm. The height of this haboob is impressive, nearly reaching the bottom of the storm clouds following rapidly behind.

7. Between 10:00pm - midnight, with winds gusting as high as 90 mph, a massive haboob has formed a wall of dust and dirt nearly 100 miles long, that continues west toward the Colorado River and California.

Between midnight - 3:00am, the thunderstorms are beginning to weaken, but the haboob marches west between 40-60 mph, reaching Blythe and Yuma close to midnight. At this point, the massive dust storm is over 150 miles long, and eventually some of the higher terrain splits the haboob into two sections. Section one heads west along I-10 and I-8 toward the Salton Sea and into the Coachella Valley around 2:30-3:00am with winds gusting to about 25-30mph, and visibility down to 0.5 mi or less. Section two heads northwest up the Colorado River Valley from near Lake Havasu, north into the Las Vegas area by about 2:45am, with winds around 35 mph and visibility less than 1 mile.

The map below shows the approximate progression of the massive haboob every hour or so.

8. Palm Springs officially gets hit with the haboob about 2:55am. The visibility drops from 10 miles to only 1.25 miles in about ten minutes. Winds gust from the east to about 25 mph - far less than the original gusts to 90 mph that helped fuel this dust storm about 6 hours earlier in the Phoenix area. Here are the early morning observations from Palm Springs Airport, with visibility as low as 0.50 mile between 3:53 - 4:15am.

9. Most of Saturday remains dusty, with visibility below 5 miles most of the afternoon. The shallow layer of dusty air left over is banked up against our local mountains. With easterly winds blowing most of the day, the dust doesn't have much of anywhere to go, except to be pushed up and trapped against the mountains. Therefore, the air remains quite unhealthful through sunset.

IN SUMMARY

This haboob was fueled by exceptionally strong winds in Arizona, as well as exceptionally well organized thunderstorms with large downdrafts that remained intact for several hours. It was a classic haboob, with cooler, dense air sinking out ahead of the storms into a hot and humid airmass... providing the perfect conditions.

Additional strong storms are possible again late Sunday, Monday and Tuesday, along with the possibility of flooding rains or additional haboobs over the deserts of California and Arizona. Humidity will likely finally decrease around Thursday of next week.