An upper level disturbance passing through Southeast Arizona allowed for some loosely organized storms to develop. Strong steering winds and low level shear allowed the storms to move rather quickly.
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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.
The episode as NWS TWC wrote it up.
An upper level disturbance passing through Southeast Arizona allowed for some loosely organized storms to develop. Strong steering winds and low level shear allowed the storms to move rather quickly. The storms had begun developing just after 10 a.m. MST for an unusually early start. A spotter in Sierra Vista reported 1.44 inches of rainfall.
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 16, 9:40 AM MST, 3 hours 20 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TUCSON AZ 940 AM MST MON AUG 16 2004 SOUTHEAST ARIZONA FORECAST DISCUSSION .SYNOPSIS...AN UPPER LEVEL DISTURBANCE WILL ENHANCE THUNDERSTORM ACTIVITY TODAY. RELATIVELY DRIER CONDITIONS ARE EXPECTED LATER IN THE WEEK AS THE UPPER HIGH SHIFTS INTO A LESS FAVORABLE POSITION. HOWEVER... THERE WILL STILL BE ENOUGH MOISTURE FOR ISOLATED THUNDERSTORMS OVER MAINLY HIGHER TERRAIN. && .DISCUSSION...A WEAK DISTURBANCE ALOFT HAS ALLOW SCATTERED SHOWERS AND THUNDERSTORMS TO CONTINUE THIS MORNING WITH RAINFALL AMOUNTS REPORTED UP TO 1/4 INCH WITHIN THE LAST SIX HOURS. LOW PRESSURE TROUGH CENTERED AT THE CENTRAL CALIFORNIA/NEVADA STATE LINE EXTENDS INTO ARIZONA WITH AN EMBEDDED SHORT WAVE LOCATED OVER GILA COUNTY. OVER THE NEXT 24 HOURS THE SHORT WAVE IS EXPECTED TO WEAKEN AND SLIDE TO THE SOUTHEAST AS ITS PARENT LOW SHIFTS NORTHWARD DUE TO FORCING FROM BUILDING HIGH PRESSURE SOUTH OF CALIFORNIA. AS THE RIDGE BUILDS MOISTURE WILL BE FORCED OUT OF ARIZONA AS THE WEEK PROGRESSES. HOWEVER... AMPLE MOISTURE WILL REMAIN OVERHEAD FOR THE POTENTIAL OF THUNDERSTORMS. THE 12Z TUCSON SOUNDING WAS BAD. SO A 14Z SOUNDING WAS RELEASED AND DISPLAYS GOOD DATA. PLENTY OF MOISTURE REMAINS OVER SOUTHEAST ARIZONA WITH PRECIPITABLE WATER VALUES AROUND 1.5 INCHES. ALSO... WEAK SHEAR WAS REPORTED IN THE LOWER LEVELS AND WITH THE PHOENIX SOUNDING REPORTING A HELICITY NEAR 60 WILL NEED TO WATCH FOR ROTATION IN THIS AFTERNOON/S THUNDERSTORMS. OTHERWISE... DYNAMICS ARE LACKING TODAY AS FLOW ALOFT IS FAIRLY WEAK AND THE JET HAS WEAKENED AND SAGGED TO THE SOUTH. SO CONVECTION WILL NEED TO RELY ON THE DISTURBANCE FOR ANY ENHANCEMENT. && .TWC WATCHES/WARNINGS/ADVISORIES...NONE. EVANS
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE TUCSON AZ 1146 AM MST MON AUG 16 2004 AZZ019-029>035-170700- NORTHERN GREENLEE COUNTY-UPPER GILA RIVER VALLEY-COCHISE COUNTY- SOUTHEAST PINAL COUNTY-TUCSON METRO/MARANA/GREEN VALLEY- SANTA CRUZ COUNTY-TOHONO OODHAM NATION-WESTERN PIMA COUNTY- 1146 AM MST MON AUG 16 2004 THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST ARIZONA .DAY ONE...TODAY SYNOPSIS...ANOTHER ROUND OF STRONG TO SEVERE THUNDERSTORMS HAS ALREADY DEVELOPED OVER PORTIONS OF SOUTHEAST ARIZONA. THE RISK OF BOTH SEVERE THUNDERSTORMS AND FLASH FLOODING IS ABOVE CLIMATOLOGY TODAY. THE HIGHEST RISK WILL BE GENERALLY SOUTHEAST OF A HANNAGAN MEADOW-TUCSON-SELLS LINE THROUGH 6 PM...WITH THE HIGHEST RISK SHIFTING NORTHWEST OF THIS LINE BETWEEN 2 PM AND 9 PM. DISCUSSION...A PERSISTENT AND STATIONARY UPPER LEVEL DISTURBANCE REMAINED ALONG THE ARIZONA-NEW MEXICO BORDER...WITH ANOTHER UPPER LEVEL DISTURBANCE MOVING ACROSS NEVADA. THESE TWO FEATURES WERE ACTING ON RESIDUAL MONSOON MOISTURE TO PRODUCE ORGANIZED AND STRONG THUNDERSTORMS. AS HAS BEEN THE CASE THE PAST SEVERAL DAYS...THE STORMS HAVE HAD RAINFALL RATES OF WELL OVER AN INCH PER HOUR. THE MAIN DIFFERENCE TODAY IS THAT STEERING WINDS ARE STRONGER AND THERE IS EVEN SOME LOW LEVEL WIND SHEAR. THIS HAS CAUSED THE STORMS TO MOVE RATHER QUICKLY...BUT THEY HAVE ALSO BEEN MORE ORGANIZED AND HAVE BEEN OCCASIONALLY FORMING INTO SHORT LINES WITH WEAK ROTATIONAL SIGNATURES. THERE HAS ALSO BEEN SOME CELL TRAINING. THE INITIAL ROUND OF THUNDERSTORMS WILL MOVE SOUTHEAST INTO THE NEW MEXICO BOOTHEEL AND NORTHEAST SONORA BY LATE AFTERNOON. HOWEVER NEW THUNDERSTORMS ARE EXPECTED TO DEVELOP OVER THE WESTERN HALF OF THE MOGOLLON RIM AND COULD DROP SOUTH INTO THE REGION BY LATE AFTERNOON OR EARLY EVENING. SINCE THIS SECOND ROUND OF STORMS WILL HAVE MORE SUNSHINE AND HEAT TO WORK WITH...THEY COULD ALSO BE QUITE STRONG IF THE SURVIVE THE TRIP THROUGH CENTRAL ARIZONA DESERTS AND ARRIVE BEFORE DAYTIME HEATING DIMINISHES. IF THIS OCCURS...WATCHES MAY BE REQUIRED FOR EITHER SEVERE THUNDERSTORMS...FLASH FLOODS...OR BOTH LATER THIS AFTERNOON. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY. THE UPPER LEVEL DISTURBANCES OVER THE DESERT SOUTHWEST WILL GRADUALLY SHIFT EAST ON TUESDAY AND WEDNESDAY WHICH WILL ALLOW A DRIER WESTERLY FLOW TO OVERTAKE THE REGION. THE RISK OF THUNDERSTORMS WILL GRADUALLY DIMINISH STARTING ON TUESDAY...WITH THE STORMS BECOMING ISOLATED AND CONFINED NEAR THE MOUNTAINS BY FRIDAY. THERE ARE MORE SIGNS TODAY THAT A SOMEWHAT MORE ACTIVE PATTERN WILL DEVELOP NEXT WEEKEND. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. PYTLAK
The Tucson radar (KEMX), 83 km away, was scanning. The volume nearest the first event began at 19:57 UTC.
1 flash flood. Local standard time, as filed.
The Sierra Vista Sheriff dispatch reported that 5 roads were closed due to high water. The roads were all impassable.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Arizona in 2004Every state in 2004This day in weather historyWarnings in Arizona, August 2004
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: 5418621.