Flash Flood and Hail in Arizona, August 28, 2002

Name: Flash Flood and Hail in Arizona, August 28, 2002
Start: 2002-08-28T12:55
End: 2002-08-28T18:00
Location: Arizona

August 28, 2002 · NWS TWC · 3 events in 1 county or zone

A significant increase in moisture moved over southeast Arizona from Tucson east. 81 inches from the 00Z sounding.

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

Open the live radar over this ground

The toll

Deaths: 0
Injuries: 0
Property damage: $10,000
Crop damage: None recorded
Events: 3

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 significant increase in moisture moved over southeast Arizona from Tucson east. The 12Z KTUS sounding indicated a precipitable water value of 1.75 inches, which increased from .81 inches from the 00Z sounding. The cape was also very impressive, with the sounding indicating 5900 J/kg at 12Z. Combining the extremely unstable atmosphere with significant moisture increase and a 90 knot jet streak moving over the area between 18Z and 00Z, severe weather exploded over the greater Tucson area by 100 pm MST. The first weather report of the day was a 58 mph peak wind gust from a thunderstorm over Ryan Field Airport. By 150 pm MST, the first reports of one inch diameter in size hail was reported in central Tucson. Reports then started flowing into the office of hail ranging from .75 to 3.0 inches in diameter. Several cars were damaged due to the large hail. One spotter reported 3.0 inch in diameter size hail broke the car windshield at 230 pm MST. Flash flooding also occurred on the northwest side of Tucson and also in Marana. Several thunderstorms were developing one right after the other over the same area between 400 and 600 pm MST. Tangerine Road was barricaded at 600 pm through 700 pm MST due to the rapidly flowing water across several of the low lying dips in the road. After 800 pm MST, road graders had to removed sand a debris from several roads on the northwest side of Tucson. Spotters and National Weather Service employees reported 2.5 to 2.75 inches of rain had fallen in the Dove Mountain residential area. There were also road closures in Oro Valley including North La Cholla Blvd, W Naranja Drive, and W Canada Hills Drive.

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 28, 9:45 AM MST, 3 hours 10 minutes earlier.

Area forecast discussion, Aug 28, 9:45 AM MST, 3 hours 10 minutes before

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
945 AM MST WED AUG 28 2002

.SYNOPSIS...AN INCREASE IN MOISTURE ACROSS SOUTHEAST ARIZONA WILL
BRING A SLOW INCREASE IN AFTERNOON AND EVENING THUNDERSTORM ACTIVITY
THE REST OF THE WEEK AND INTO THE COMING WEEKEND. AS A
RESULT...AFTERNOON HIGH TEMPERATURES WILL FALL A FEW DEGREES.

.DISCUSSION...LOOKING AT IR IMAGERY...WE STILL HAVE SOME CLOUD
DEBRIS ACROSS SOUTHEAST ARIZONA FROM LAST NIGHTS THUNDERSTORM
COMPLEX THAT DEVELOPED IN MEXICO.  A FEW LIGHTNING STRIKES HIT IN
COCHISE AND SANTA CRUZ AROUND MIDNIGHT...HOWEVER MOST ACTIVITY WAS
ALONG AND SOUTH OF THE U.S. AND MEXICAN BORDER.  WITH LOWER LEVEL
WINDS FROM SOUTH AND SOUTHWEST...SIGNIFICANT MOISTURE WAS PULLED UP
FROM THE COMPLEX INTO EXTREME SOUTHEAST ARIZONA...FROM TUCSON EAST.
AS A RESULT OF MOISTURE INCREASE AND CLOUD COVER...LOW TEMPERATURES
ACROSS THE AREA WERE 10 DEGREES ABOVE THE PREVIOUS NIGHTS LOW TEMPS.
WITH THE HIGHER HUMIDITIES ACROSS THE AREA (CURRENTLY 47 PERCENT
FROM YESTERDAYS 20 PERCENT)....TEMPERATURES MAY NOT BE AS HIGH AS
THE LAST COUPLE OF DAYS. PREVIOUS SHIFT DROPPED TEMPERATURES BACK
ABOUT 5 DEGREES ACROSS THE AREA FOR TODAY AND THIS LOOKS PRETTY
GOOD. CAN SEE THE SIGNIFICANT INCREASE IN MOISTURE BEST FROM THE 12Z
KTUS SOUNDING...WITH PWAT VALUES OF 1.75 INCHES (THE PREVIOUS
SOUNDING ONLY HAD .8 INCHES).  IN THE LOWEST LEVELS WE HAD 10 TO 20
KNOT SOUTHERLY WINDS HELPING PULL THE MOISTURE NORTHWARDS.
HOWEVER...THE YUMA AND PHOENIX SOUNDINGS WERE RATHER DRY.  THE PWAT
VALUES AT YUMA ONLY INCREASED FROM .62 TO .78 INCHES AND THE KPSR
ONLY INCREASED FROM .68 TO .81 INCHES...AND BOTH DRY IN THE LOWEST
LEVELS.  TAKING A LOOK AT YUMA VAD WIND PROFILER...THE WINDS WERE
PREDOMINATELY FROM THE WEST OR NORTHWEST FROM 2000 FEET AND UPWARD
WITH ONLY 10 TO 15 KNOTS FROM THE SOUTH BELOW 2000 FEET.  A RECENT
VAD WIND PROFILE INDICATED SLIGHT SURGING...WITH WINDS FROM THE
SOUTH AT 10 TO 20 KNOTS UP TO 3000 FEET.  SO THE BIG QUESTION FOR
THE DAY...ARE WE GOING TO GET SOME THUNDERSTORM DEVELOPMENT TODAY?
WITH THE JET MAX MOVING ACROSS THE AREA TODAY AND TOMORROW THERE
SHOULD BE SOME WEAK UPPER LEVEL FORCING. PLUS THERE IS ENOUGH
MOISTURE IN EXTREME PORTIONS OF SOUTHEAST ARIZONA...THAT MAY BE ABLE
TO FIRE SOME SORT OF CONVECTION.  THE ETA MODEL INDICATES THAT THE
UPPER LEVEL DIVERGENCE FIELD WOULD BE OVER CENTRAL ARIZONA AND SHOWS
PRECIP OVER EASTERN ARIZONA.   HOWEVER...THE AVN MODEL INDICATES A
MORE ISOLATED TO SCATTERED TYPE EVENT FOR THIS AFTERNOON...WITH THE
UPPER LEVEL DIVERGENCE FIELD OVER NEW MEXICO AREA WHERE IT IS
PREDICTING THE BEST AREA FOR THUNDERSTORM DEVELOPMENT.  CURRENTLY A
FEW THUNDERSTORMS HAVE ALREADY FIRED OVER WESTERN NEW MEXICO. FOR
NOW...CURRENTLY THINK THAT BEST CHANCES OF DEVELOPMENT WILL BE IN
THE WHITES AND EASTERN MOUNTAINS FOR THIS AFTERNOON AND EVENING. NOT
TOO CONFIDENT ABOUT THE 30 AND 40 POPS IN TUCSON AREA...MAY HAVE TO
MAKE AN UPDATE TO LOWER BY 10 PERCENT OR SO...BUT WOULD LIKE TO SEE
HOW THINGS DEVELOP. MG

.TWC...NONE.

In the hours before

Special weather statement, Aug 28, 11:30 AM MST, 1 hour 25 minutes before

AZZ019-029>035-290700-

SOUTHEAST ARIZONA HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1130 AM MST WED AUG 28 2002

.SYNOPSIS...THE AIRMASS HAS MOISTENED SIGNIFICANTLY OVER NEARLY ALL
OF SOUTHEAST ARIZONA. EXTREME WESTERN SECTIONS OF THE AREA REMAIN
FAIRLY DRY UNDER THE INFLUENCE OF SOUTHWEST WINDS ALOFT. AN UPPER
HIGH PRESSURE CENTER WILL REMAIN OVER WEST TEXAS OR SOUTHERN NEW
MEXICO FOR THE NEXT SEVERAL DAYS. AN UPPER TROF HAS SETTLED INTO THE
INTERMOUNTAIN AREA AND THIS HAS CAUSED AN INCREASE IN THE SOUTHWEST
WINDS ALOFT OVER THE WESTERN SECTIONS OF THE STATE.

.DISCUSSION...THE LARGE INCREASE IN MOISTURE IS DUE TO A
THUNDERSTORM COMPLEX THAT DEVELOPED SOUTH OF COCHISE COUNTY LATE
TUESDAY. THE COMBINATION OF THE UPPER HIGH AND THE TROF IS CAUSING
FAIRLY BRISK SOUTHWEST WINDS ALOFT OVER THE AREA. THE AMOUNT OF
MOISTURE IN THE AIR WILL HELP TO PRODUCE VERY HEAVY RAIN FROM THESE
STORMS. HOWEVER THE STRONG SOUTHWEST WINDS WILL PUSH THE STORMS AT
GOOD CLIP TO THE NORTHEAST. THUS THE THREAT FOR HEAVY RAIN IS NEAR
CLIMATOLOGY VALUES. THE AMOUNT OF MOISTURE IN THE AIR WILL ALSO
CAUSE SKIES TO CLOUD OVER THUS PREVENTING STRONG HEATING. THIS WILL
HELP TO REDUCE THE LIKELIHOOD OF SEVERE WINDS FROM THESE STORMS.
HOWEVER COLD AIR ALOFT COULD INCREASE THE THREAT OF HAIL.

Special weather statement, Aug 28, 12:02 PM MST, 53 minutes before

AZZ019-029>035-290700-

SOUTHEAST ARIZONA HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1130 AM MST WED AUG 28 2002

.SYNOPSIS...THE AIRMASS HAS MOISTENED SIGNIFICANTLY OVER NEARLY ALL
OF SOUTHEAST ARIZONA. EXTREME WESTERN SECTIONS OF THE AREA REMAIN
FAIRLY DRY UNDER THE INFLUENCE OF SOUTHWEST WINDS ALOFT. AN UPPER
HIGH PRESSURE CENTER WILL REMAIN OVER WEST TEXAS OR SOUTHERN NEW
MEXICO FOR THE NEXT SEVERAL DAYS. AN UPPER TROF HAS SETTLED INTO THE
INTERMOUNTAIN AREA AND THIS HAS CAUSED AN INCREASE IN THE SOUTHWEST
WINDS ALOFT OVER THE WESTERN SECTIONS OF THE STATE.

.DISCUSSION...THE LARGE INCREASE IN MOISTURE IS DUE TO A
THUNDERSTORM COMPLEX THAT DEVELOPED SOUTH OF COCHISE COUNTY LATE
TUESDAY. THE COMBINATION OF THE UPPER HIGH AND THE TROF IS CAUSING
FAIRLY BRISK SOUTHWEST WINDS ALOFT OVER THE AREA. THE AMOUNT OF
MOISTURE IN THE AIR WILL HELP TO PRODUCE VERY HEAVY RAIN FROM THESE
STORMS. HOWEVER THE STRONG SOUTHWEST WINDS WILL PUSH THE STORMS AT
GOOD CLIP TO THE NORTHEAST. THUS THE THREAT FOR HEAVY RAIN IS NEAR
CLIMATOLOGY VALUES. THE AMOUNT OF MOISTURE IN THE AIR WILL ALSO
CAUSE SKIES TO CLOUD OVER THUS PREVENTING STRONG HEATING. THIS WILL
HELP TO REDUCE THE LIKELIHOOD OF SEVERE WINDS FROM THESE STORMS.
HOWEVER COLD AIR ALOFT COULD INCREASE THE THREAT OF HAIL.

The radar

The Tucson radar (KEMX), 47 km away, was scanning. The volume nearest the first event began at 19:55 UTC.

Open the radar archive at this moment

Event by event

1 hail, 1 thunderstorm wind, 1 flash flood. Local standard time, as filed.

Hail, Pima

When: August 28, 12:55 PM MST to 5:00 PM MST
Where: Pima County, Tucson
Measured: 3 in hail
Property damage: $10,000
Reported by: LAW ENFORCEMENT
Coordinates: 32.233, -110.933

Thunderstorm Wind, Pima

When: August 28, 12:55 PM MST to 1:15 PM MST
Where: Pima County, Tuscon Ryan Fld Arpt
Measured: 58 kt (67 mph)
Reported by: AWOS,ASOS,MESONET,ETC
Coordinates: 32.133, -111.167

Flash Flood, Pima

When: August 28, 4:30 PM MST to 6:00 PM MST
Where: Pima County, Tucson
Reported by: METEOROLOGIST(NON NWS)
Coordinates: 32.097, -111.790 (the zone’s center; the record gives no point)

What these are

Hail: Hail three-quarters of an inch or larger, or smaller hail that caused damage, filed with the largest stone measured.
Thunderstorm Wind: Winds from a thunderstorm of 50 knots (58 mph) or more, or lower winds that caused damage or casualties. Measured gusts are marked MG, estimated EG.
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 2002 Every state in 2002 This day in weather history Warnings in Arizona, August 2002

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: 5312820, 5312821, 5312822.