Monsoon Deluge Swamps Phoenix, Summer Heat Finally Showing Further East

Written by Mark Vogan on August 20, 2014 in United States of America with 0 Comments

While the hottest air of summer builds over the South and eventually north up into the Midwest, the Western monsoon has really meant business over the past 36 hours with major flooding causing havoc across the West and Greater Phoenix area in particular.

Courtesy of Damon Lane/ABC Phoenix

Courtesy/Credit: ABC 15 Phoenix

Impressive 24-hour rain totals

Courtesy/Credit: NWS Phoenix

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Here’s the write-up from the NWS of Phoenix.

Very heavy rainfall occurred over portions of the Phoenix metropolitan area during the day on Tuesday August 19. The heaviest rainfall began early Tuesday morning around 6 am around Carefree, Cave Creek, Anthem, and New River. Conditions deteriorated quickly as storms expanded and intensified, with numerous reports of flooded streets and underpasses by 7 am. Numerous swift-water rescues occurred later in the morning around New River, and portions of Interstate 17 were closed for a time as the northbound lanes were inundated by Skunk Creek. Additional storms and heavy rainfall moved through the metro area later in the afternoon. By the time showers had tapered off Tuesday evening, some locations had seen more than 4 inches of rainfall.

An upper level trough off the California coast, along with a strong northwest-southeast oriented moisture gradient, provided the necessary ingredients for an active day. Atmospheric moisture across southeast California and southwest Arizona was at or slightly below normal for mid-August. However, moisture from Maricopa County eastward was substantially above normal (approximately 1.75 times higher than normal for mid-August). The abundant moisture, combined with the approaching trough and mid -level southwesterly winds, provided an ideal setup for storm development and training (storms continuously re-developing over the same area). The southwesterly winds also provided substantial orographic lift as the moist atmosphere was forced to ascend the higher terrain north of Phoenix.

NWS Phoenix

Nearly every wash in the area saw substantial flow on Tuesday, with very rapid rises around New River and Cave Creek. A sampling of stream gages from the Maricopa County Flood Control District reveals a peak flow of 15181 cubic feet per second (cfs) at the New River Fire gage, 12927 cfs along Skunk Creek where it crosses I-17, 14974 cfs along Cave Creek a few miles south of Cave Creek, and over 26000 cfs along Cave Creek in the town of Cave Creek. A river gage along the Agua Fria River at Rock Springs reported a peak flow around 40000 cfs, which equates to a depth of approximately 24.84 feet at that location.

afra3_hg

The Agua Fria River at Rock Springs crested at 24.84 feet Tuesday morning, which is classified as a “Major flood”. This is the 4th highest crest on record at this site.
#1: 28.05ft – 1/21/2010
#2: 27.20ft – 12/18/1978
#3: 25.28ft – 1/8/1993
#4: 24.84ft – 8/19/2014

Hottest Air Of Summer & In 2 Years?

Here’s the upper pattern supporting the Big Western rains and Southern heat which will expand north through the rest of this week. Expect major storms and rains to break out on the northern rim of the hot dome.

Check out the 594dm height line extending from Louisiana to Alabama. The GFS has low 100s beneath the core late this week into the weekend. The hottest air in 2 to 3 years.