Flash Flood in Arizona, July 29, 2003

Name: Flash Flood in Arizona, July 29, 2003
Start: 2003-07-29T19:55
End: 2003-07-29T20:45
Location: Arizona

July 29, 2003 · NWS TWC · 1 event in 1 county or zone

A thunderstorm moved through the town of Ajo around 800 pm MST, producing heavy rain which resulted in a flash flood. 75 inches of precipitation after the event occurred.

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.

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Wind
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The toll

Deaths: 0
Injuries: 0
Property damage: $25,000
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.

A thunderstorm moved through the town of Ajo around 800 pm MST, producing heavy rain which resulted in a flash flood. Ajo police reported 2.75 inches of precipitation after the event occurred. It was estimated that near 4.0 inches of precipitation feel in 45 minutes over the Phelps Dodge area. Most damage occurred near Gibson Wash, with 2nd Avenue bridge overtopped by 3 feet of water. The railroad was also overtopped. Fences were downed due to rushing water and several road were washed out. In all 673 land parcels were flooded and one swift water rescue performed.

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 Jul 29, 1:37 PM MST, 6 hours 18 minutes earlier.

Area forecast discussion, Jul 29, 1:37 PM MST, 6 hours 18 minutes before

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
137 PM MST TUE JUL 29 2003

.SYNOPSIS...ARIZONA IS CURRENTLY BETWEEN AN AREA OF HIGH PRESSURE
CENTERED OVER NEVADA AND A LOW PRESSURE SYSTEM OVER BAJA. THE BAJA
LOW WILL MOVE WESTWARD A BIT TONIGHT AND WEDNESDAY...ALLOWING THE
STEERING FLOW TO BECOME MORE SOUTHERLY. THIS MORE SOUTHERLY FLOW
WILL KEEP THE AIRMASS VERY MOIST OVER SOUTHEAST ARIZONA THE NEXT FEW
DAYS. THIS MOISTURE COMBINED WITH DAYTIME HEATING WILL LEAD TO MORE
SCATTERED AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS. HIGH
PRESSURE CENTERED OVER NEVADA WILL EVENTUALLY SHIFT OVER NEW MEXICO
AND SOUTHWEST TEXAS BY THE WEEKEND. THIS MAY LEAD TO A GRADUAL
DECREASE IN AREAL COVERAGE TO THUNDERSTORMS OVER THE WESTERN DESERTS
BY THE END OF THE WEEK AS DRIER AIR TRIES TO FILTER INTO THE REGION
FROM THE WEST...BUT CONFIDENCE IN THIS IS LOW.

.DISCUSSION...WATER VAPOR IMAGERY AND LIGHTNING DATA SHOWS
CONVECTION DEVELOPING IN FAVORED AREAS AS ANTICIPATED...GENERALLY
OVER EXTREME SOUTHEAST ARIZONA BUT ALSO EXTENDING SOUTHEAST INTO
SONORA AND CHIHUAHUA. RADARS DETECTING SCATTERED TO NUMEROUS SHOWERS
AND THUNDERSTORMS IN THIS AREA AND WILL CONTINUE TO DEVELOP AND/OR
MOVE INTO THE REGION. AS SUSPECTED THE 12Z TUCSON SOUNDING WAS NOT
REPRESENTATIVE AND 18Z SOUNDING REVEALED A SIGNIFICANTLY WARMER
AIRMASS ABOVE 500MB. ABOVE THE VALLEY BOUNDARY LAYER...750MB OR
SO...FLOW IS NEARLY UNIDIRECTIONAL WITH NOT MUCH SPEED SHEAR.

IN THE 300-500MB LAYER MODELS ARE PROGGING THE LOW OVER THE BAJA
PENINSULA TO MOVE WEST THROUGH WEDNESDAY AS THE HIGH SHIFTS POSITION
FROM NORTHERN CALIFORNIA AND NEVADA INTO UTAH/NRN ARIZONA WITH THE
RIDGE NOSING INTO NEW MEXICO AND WEST TEXAS BY THURSDAY. MODELS PROG
THE DEFORMATION ZONE OVER TEXAS TO DRIFT WEST THROUGH WEDNESDAY BUT
AS THE RIDGE BUILDS SOUTH THIS FEATURE ALSO GETS PUSHED MUCH FARTHER
SOUTH. AT 300MB...AVN IS ADVERTISING SOME DECENT OMEGA AND
DIVERGENCE FIELDS MOVING INTO ARIZONA BEGINNING WEDNESDAY NIGHT AND
CONTINUING THROUGH FRIDAY...BUT ESPECIALLY ON FRIDAY NEAR THE GULF
OF CALIFORNIA.

AIRMASS WILL REMAIN RATHER JUICY THROUGH THE END OF THE WEEK...BUT
THE GFS IS HINTING AT SOME DRYING FROM THE WEST DURING THE WEEKEND
AS A TROUGH DEVELOPS ALONG THE WEST COAST...BUT I AM NOT CONFIDENT
IN THIS OCCURRING...SO UNTIL I SEE SOME CONSISTENCY BETWEEN MODEL
RUNS...WILL KEEP A STANDARD MONSOON FORECAST OF SCATTERED AFTERNOON
AND EVENING THUNDERSTORMS GOING THROUGH EARLY NEXT WEEK.

AVN MOS TEMP GUIDANCE SEEMS TO COOL...SO USED A BLEND OF PREVIOUS
FORECAST NUMBERS AND ETA/NGM. FOR THE EXTENDED PERIOD WENT SLIGHTLY
ABOVE MRF MOS.

MOLLERE

.TWC...FLOOD WARNING FOR CENTRAL PIMA COUNTY/ZONE 32 UNTIL 5 PM MST.

Hazardous weather outlook, Jul 29, 12:20 PM MST, 7 hours 35 minutes before

AZZ019-029>035-301400-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1220 PM MST TUE JUL 29 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST ARIZONA

.DAY ONE...TODAY

SYNOPSIS...A COOL START TO THE DAY WILL BE OVERCOME THIS AFTERNOON
AS TEMPERATURES CLIMB INTO THE NINETIES OVER THE VALLEYS. SOUTHERN
COCHISE COUNTY AND AREAS SOUTH AND WEST OF TUCSON SEEM THE LIKELY
AREA FOR THE STRONGEST STORMS TODAY.

DISCUSSION...

CONVECTION HAS ALREADY BEGUN THIS AFTERNOON AS MOISTURE CONTINUES TO
BE ADVECTED INTO THE AREA FROM THE SOUTHEAST. UPPER LEVEL HIGH
PRESSURE TO THE NORTHWEST WILL SLOWLY EXPAND TO THE EAST ALLOWING
ADDITIONAL MOISTURE TO BE PULLED INTO THE REGION. ALSO...SOME
COOLING HAS TAKEN PLACE AT THE UPPER LEVELS RESULTING IN ADDITIONAL
CAPE. HOWEVER...AN ELEVATED INVERSION IN THE MID LEVELS WILL NEED TO
BE OVERCOME...WHICH SHOULD NOT BE A PROBLEM DUE TO THE CONVECTIVE
TEMPERATURE BEING 92. ONLY A DELAY TO THE CONVECTION COMPARED TO
YESTERDAY IS EXPECTED. THEREFORE...WITH THE MOISTURE REMAINING OVER
SOUTHERN ARIZONA THE BEST CHANCE OF HEAVY RAIN AND STRONG WINDS WILL
BE WITHIN THE SOUTHERN PORTION OF THE COUNTY WARNING AREA. THIS
WOULD INCLUDE SANTA CRUZ...SOUTHERN COCHISE AND SOUTHERN PIMA
COUNTIES. THE STORMS ARE EXPECTED TO MOVE GENERALLY TOWARD THE WEST
OR NORTHWEST.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

SEASONAL SCATTERED THUNDERSTORMS WITH THE NORMAL IMPLIED THREAT OF
HEAVY RAIN AND STRONG WINDS WILL CONTINUE THROUGH THE WEEK.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

EVANS

In the hours before

Special weather statement, Jul 29, 4:20 PM MST, 3 hours 35 minutes before

AZZ029>034-300500-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE TUCSON AZ
420 PM MST TUE JUL 29 2003

...SEVERE THUNDERSTORM WATCH NUMBER 815 UNTIL 1000 PM...

THE STORM PREDICTION CENTER HAS ISSUED SEVERE THUNDERSTORM WATCH
NUMBER 815 FOR MOST OF SOUTHERN ARIZONA UNTIL 1000 PM MST. THIS
INCLUDES THE FOLLOWING COUNTIES...

PIMA...PINAL...GRAHAM...AND SANTA CRUZ

THUNDERSTORMS CAPABLE OF PRODUCING WIND GUSTS OVER 60 MPH...LARGE
HAIL...AND VERY HEAVY RAIN ARE POSSIBLE ACROSS MOST OF SOUTHERN
ARIZONA THIS EVENING. PAY CLOSE ATTENTION TO LOCAL MEDIA OUTLETS FOR
ADDITIONAL STATEMENTS AND POSSIBLE WARNINGS.

PYTLAK

Local storm report, Jul 29, 5:19 PM MST, 2 hours 36 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TUCSON AZ
0519 PM MST TUE JUL 29 2003

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

0250 PM    FT. HUACHUCA              AZ   85 MPH TSTORM WIND
07/29/03   COCHISE                        MEASURED AT LIBBY FIELD

0338 PM    SONOITA                   AZ   0.75 IN HAIL
07/29/03   SANTA CRUZ                     REPORTED BY SPOTTER

0420 PM    TUCSON                    AZ   WIND DAMAGE
07/29/03   PIMA                           TREE DOWNED AT RITA RD.
                                          AND OLD VAIL RD.

0435 PM    TUCSON                    AZ   WIND DAMAGE
07/29/03   PIMA                           POWER LINES DOWNED AT
                                          GRANT RD. AND PARK AVE.

0506 PM    TUCSON                    AZ   FLASH FLOOD
07/29/03   PIMA                           STREET FLOODING IN SOUTH
                                          AND CENTRAL PARTS OF THE
                                          CITY.

ESP

Local storm report, Jul 29, 5:41 PM MST, 2 hours 14 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TUCSON AZ
0541 PM MST TUE JUL 29 2003

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

0455 PM    RYAN FIELD                AZ   65 MPH WIND GUST
07/29/03   PIMA

0529 PM    TUCSON                    AZ   FLASH FLOOD
07/29/03   PIMA                           HEAVY STREET FLOODING NEAR
                                          SWAN AND 29TH ST. 2 1/2
                                          FEET OF WATER IN AN ALLEY
                                          DITCH. REPORTED BY STORM
                                          SPOTTER.

PYTLAK

Local storm report, Jul 29, 5:41 PM MST, 2 hours 14 minutes before

PRELIMINARY LOCAL STORM REPORT...CORRECTED FORMAT
NATIONAL WEATHER SERVICE TUCSON AZ
0541 PM MST TUE JUL 29 2003

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

0455 PM    RYAN FIELD                AZ   65 MPH TSTORM WIND GUST
07/29/03   PIMA                           MEASURED AT RYAN FIELD

0529 PM    TUCSON                    AZ   FLASH FLOOD
07/29/03   PIMA                           HEAVY STREET FLOODING NEAR
                                          SWAN AND 29TH ST. 2 1/2
                                          FEET OF WATER IN AN ALLEY
                                          DITCH. REPORTED BY STORM
                                          SPOTTER.

PYTLAK

Special weather statement, Jul 29, 6:30 PM MST, 1 hour 25 minutes before

AZZ029>034-300500-

SPECIAL WEATHER STATEMENT...UPDATE
NATIONAL WEATHER SERVICE TUCSON AZ
630 PM MST TUE JUL 29 2003

UPDATED TO REMOVE GRAHAM...SANTA CRUZ AND EASTERN PIMA COUNTIES FROM
THE SEVERE THUNDERSTORM WATCH

...SEVERE THUNDERSTORM WATCH NUMBER 815 UNTIL 1000 PM...

SEVERE THUNDERSTORM WATCH NUMBER 815 CONTINUES IN EFFECT FOR
PORTIONS OF SOUTHERN ARIZONA UNTIL 1000 PM MST. THE PORTIONS OF THE
WATCH THAT ARE STILL IN EFFECT INCLUDE...

CENTRAL AND WESTERN PIMA COUNTY...AND SOUTHEAST PINAL COUNTY

THUNDERSTORMS CAPABLE OF PRODUCING WIND GUSTS OVER 60 MPH...LARGE
HAIL...AND VERY HEAVY RAIN ARE POSSIBLE OVER PORTIONS OF SOUTHERN
ARIZONA THIS EVENING. PAY CLOSE ATTENTION TO LOCAL MEDIA OUTLETS FOR
ADDITIONAL STATEMENTS AND POSSIBLE WARNINGS.

The radar

The Tucson radar (KEMX), 112 km away, was scanning. The volume nearest the first event began at 02:55 UTC.

Open the radar archive at this moment

Event by event

1 flash flood. Local standard time, as filed.

Flash Flood, Pima

When: July 29, 7:55 PM MST to 8:45 PM MST
Where: Pima County, Ajo
Property damage: $25,000
Reported by: LAW ENFORCEMENT
Coordinates: 32.097, -111.790 (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

Every storm in Arizona in 2003 Every state in 2003 This day in weather history Warnings in Arizona, July 2003

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: 5330430.