Arizona, 2001

Flash Flood in Arizona, August 4, 2001

August 4, 2001 · NWS TWC · 1 event in 1 county or zone

At 1800 MST, Highway 77 near Mammoth was closed due to excessive runoff. 06 inches in San Manual just south of Mammoth.

Where it happened

Every event with a place to put it; 1 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.

  • Tornadoes
  • Tropical storms and surge
  • Floods
  • Wind
  • Hail
  • Winter weather
  • Heat and drought
  • Cold
  • Fire, smoke and dust
  • Marine and coastal
  • Other

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The toll

Deaths
0
Injuries
0
Property damage
None recorded
Crop damage
None recorded
Events
1

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS TWC wrote it up.

At 1800 MST, Highway 77 near Mammoth was closed due to excessive runoff. A spotter reported a storm total precipitation of 1.06 inches in San Manual just south of Mammoth.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Tucson, AZ wrote its last area forecast discussion before the first event at Aug 4, 5:50 PM MST, 0 minutes earlier.

Area forecast discussion, Aug 4, 5:50 PM MST, 0 minutes before
SOUTHEAST ARIZONA FORECAST DISCUSSION...MESOSCALE UPDATE
NATIONAL WEATHER SERVICE TUCSON AZ
550 PM MST SAT AUG 4 2001

.SYNOPSIS...A SUBTROPICAL DISTURBANCE WILL MOVE ACROSS SOUTHERN
ARIZONA TONIGHT AND INTO NORTHERN BAJA ON SUNDAY. IN ITS WAKE...THE
ATMOSPHERE SHOULD STABILIZE AND LEAD TO LESS THUNDERSTORM COVERAGE
ON SUNDAY AND POSSIBLY INTO MONDAY. MEANWHILE...HIGH PRESSURE WILL
REMAIN OVER THE GREAT BASIN...WHICH MAY ALLOW ANOTHER DISTURBANCE TO
MOVE WEST INTO THE REGION BY MID WEEK.

.DISCUSSION...THE STRONGER STORMS HAVE BEEN ISOLATED THIS AFTERNOON,
BUT WHERE THEY'VE BEEN ABLE TO FIRE, THEY'VE GONE SEVERE VERY
QUICKLY. CURRENT CONCERN IS THE CELL MERGER OVER EXTREME SE PINAL
WHERE AN OUTFLOW BOUNDARY MOVING NE OUT OF STORMS W OF KTUS HAVE
HELPED FOCUS THE MERGERS. OTHER STRONG STORM CLUSTERS WERE OVER
EXTREME SW PINAL AND EXTREME SW COCHISE, BOTH OF WHICH ALSO FIRED ON
OUTFLOW BOUNDARIES.

CONCERN NOW WILL TURN TO WHAT ELEVATED CONVECTION WILL DEVELOP OVER
THE NEXT 2-3 HRS. 00Z KTUS SOUNDING SHOWS ABOUT 100J/KG OF
CONVECTIVE INHIBITION FROM SURFACE-BASED PARCELS. LIFT OFF THE 700MB
LAYER, THOUGH, AND YOU'RE OFF TO THE RACES. WITH NUMEROUS OUTFLOW
BOUNDARIES NOW MOVING AROUND AND THE UPPER DIVERGENCE AXIS RIGHT
OVER THE TOP OF THE CWA, WE SHOULD SEE ISOLATED NEW DEVELOPMENT,
MUCH LIKE WE'RE SEEING TO THE W, S AND E OF THE KTUS METRO. THESE
ELEVATED STORMS ARE MORE LIKELY TO BE HEAVY RAINERS WITH PRECIP
WATERS UP NEAR 1.5". THE SEVERE THREAT IS STILL THERE, BUT WILL
DIMINISH AS THE BOUNDARY LAYER BEGINS TO COOL WITH THE SUNSET. PYTLAK

.TWC...NONE.

In the hours before

Local storm report, Aug 4, 3:53 PM MST, 1 hour 57 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TUCSON ARIZONA
0353 PM MST SAT AUG 4 2001

TIME (MST) .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0352 PM    5N RIO RICO               AZ   1 3/4 INCH HAIL
08/04/01   SANTA CRUZ                     DPS REPORTED DAMAGE TO VEHICLE
Local storm report, Aug 4, 3:58 PM MST, 1 hour 52 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TUCSON ARIZONA
0358 PM MST SAT AUG 4 2001

TIME (MST) .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0352 PM    5N RIO RICO               AZ   1.75 INCH HAIL
08/04/01   SANTA CRUZ                     DPS REPORTED DAMAGE TO VEHICLE

The radar

The Phoenix radar (KIWA), 52 km away, was scanning. The volume nearest the first event began at 00:47 UTC.

Open the radar archive at this moment

Event by event

1 flash flood. Local standard time, as filed.

Flash Flood, Pinal

When
August 4, 5:50 PM MST to 9:00 PM MST
Where
Pinal County, Mammoth
Reported by
DEPT OF HIGHWAYS
Coordinates
32.904, -111.345 (the zone’s center; the record gives no point)

What these are

Flash Flood
Flooding that begins within six hours of the rain that causes it, or of a dam or levee failure or ice jam release, often with deadly speed.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

More

Every storm in Arizona in 2001Every state in 2001This day in weather historyWarnings in Arizona, August 2001

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 5259902.