Moisture crept into southern moisture ahead of a weak upper level trough. Hail and landspout tornadoes occurred with thunderstorms near the Mexican border.
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.
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.
Moisture crept into southern moisture ahead of a weak upper level trough. Hail and landspout tornadoes occurred with thunderstorms near the Mexican border. The cold downrush of wind from these storms generated an outflow boundary that progressed northwest across Pima and Pinal Counties resulting in strong winds and reduced visibility in blowing dust. Visibilities were reduced to a quarter mile or less for several minutes.
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 May 9, 8:36 AM MST, 4 hours 24 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TUCSON AZ 836 AM MST WED MAY 9 2012 .SYNOPSIS...A LOW PRESSURE SYSTEM TRACKING THROUGH NORTHERN MEXICO WILL BRING SHOWERS AND THUNDERSTORMS TO THE AREA THIS AFTERNOON AND EVENING. A FEW RESIDUAL SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE NEAR THE NEW MEXICO BORDER THURSDAY. OTHERWISE...DRY CONDITIONS AND WARMING TEMPERATURES ARE THEN EXPECTED INTO THIS WEEKEND. && .DISCUSSION...LATEST WV SATELLITE IMAGERY SHOWS THE UPPER LOW ACROSS NORTHERN MEXICO. MEANWHILE...DEEP LAYER EASTERLY FLOW HAS BROUGHT IN CONSIDERABLY MORE MOISTURE INTO SOUTHEAST ARIZONA WITH SURFACE DEWPOINTS NOW IN THE LOWER TO MIDDLE 40S FOR MUCH OF THE FORECAST AREA. MOISTURE WAS JUST ON ITS WAY IN DURING THE RELEASE OF THE 12Z KTWC SOUNDING WHICH DEPICTED 0.35 INCHES OF PWAT. MEANWHILE...WE'RE ALREADY SEEING A FEW CONVECTIVE SHOWERS THIS MORNING MAINLY OVER COCHISE COUNTY WITH A FEW CG STRIKES. IT SHOULD EVOLVE INTO A VERY INTERESTING LATE MORNING THROUGH AFTERNOON AS MLCAPE VALUES INCREASE TO ABOUT 1000 J/KG WITH INVERTED V SOUNDINGS AS SURFACE DEWPOINT DEPRESSIONS WILL BE ABOUT 45 TO 50 DEGREES F. AS STORMS DEVELOP EAST OF TUCSON...THEY WILL PUSH TO THE WEST-NORTHWEST WITH 20 KTS OF STEERING FLOW. SOME OF THESE STORMS ARE EXPECTED TO BE STRONG AND OUR MAIN CONCERN CONTINUES TO BE STRONG AND GUSTY WINDS WITH RESULTING BLOWING DUST. CURRENT FORECAST DOES HANDLE THIS WELL WITH NO CHANGES EXPECTED AT THIS TIME. A SPECIAL NOTE TO OUR DATA CUSTOMERS...WE DO PLAN ON RELEASING A SPECIAL 18Z KTWC SOUNDING TO BETTER CAPTURE THE PROFILE AND MOISTURE INCREASE. THE UPPER LOW WILL CONTINUE TO PUSH EAST THURSDAY WITH ENOUGH RESIDUAL MOISTURE FOR A SLIGHT CHANCE TO LOW END CHANCE POPS MAINLY NEAR THE NEW MEXICO BORDER. THEREAFTER...GENERALLY DRY CONDITIONS ARE EXPECTED INTO EARLY NEXT WEEK WITH MUCH WARMER TEMPERATURES THIS WEEKEND INTO EARLY NEXT WEEK. && .AVIATION...EASTERLY FLOW ASSOCIATED WITH LOW PRESSURE MOVING THROUGH SONORA MEXICO WILL CONTINUE TO INCREASE MOISTURE ACROSS THE AREA. THUS EXPECT BETTER AREAL COVERAGE OF SHOWERS AND THUNDERSTORMS TODAY. THRU 19Z...FEW-SCT100 SCT-BKN150-200 WITH ISOLD -SHRA OR -TSRA DVLPG...MAINLY EAST OF KTUS. BTWN 09/19Z AND 10/04Z SCT080-100 BKN150 SCT SHRA/TSRA. LCL CIGS BKN040 WITH MTNS OBSCD. WIND GUSTS UP TO 45 KTS NEAR TSTMS. AFT 10/04Z SCT100 BKN150 ISOLD SHRA. SURFACE WIND EASTERLY 10-20 KTS WITH LOCAL GUSTS UP TO 30 KTS. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS. && .FIRE WEATHER...A LOW PRESSURE SYSTEM PUSHING THROUGH SONORA MEXICO TODAY WILL BRING A SUSTAINED EASTERLY FLOW IMPORTING MOISTURE INTO THE AREA. SCATTERED SHOWERS AND THUNDERSTORMS ACROSS MOST OF THE AREA THIS AFTERNOON AND EVENING...WITH STRONG GUSTY OUTFLOWS ASSOCIATED WITH SOME STORMS. SHOWER ACTIVITY WILL RETREAT AS LOW EXITS...TAKING MOISTURE WITH IT. HOWEVER...MAY STILL SEE ISOLATED ACTIVITY NEAR THE NEW MEXICO BORDER THURSDAY. DRY CONDITIONS AND ABOVE NORMAL TEMPERATURES WILL RETURN FRIDAY THROUGH SUNDAY. && .TWC WATCHES/WARNINGS/ADVISORIES...NONE. WEATHER.GOV/TUCSON
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE TUCSON AZ 500 AM MST WED MAY 9 2012 AZZ503>514-100600- UPPER SANTA CRUZ RIVER VALLEY/ALTAR VALLEY-TUCSON METRO AREA- SOUTH CENTRAL PINAL COUNTY-SOUTHEAST PINAL COUNTY- UPPER SAN PEDRO RIVER VALLEY- EASTERN COCHISE COUNTY BELOW 5000 FEET-UPPER GILA RIVER VALLEY- WHITE MOUNTAINS OF GRAHAM AND GREENLEE COUNTIES- GALIURO AND PINALENO MOUNTAINS-CHIRICAHUA MOUNTAINS- DRAGOON AND MULE AND HUACHUCA AND SANTA RITA MOUNTAINS- CATALINA AND RINCON MOUNTAINS- 500 AM MST WED MAY 9 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST ARIZONA. .DAY ONE...TODAY AND TONIGHT MOISTURE WILL CONTINUE TO INCREASE TODAY AS LOW PRESSURE MOVES ACROSS SONORA MEXICO. EXPECT MORE WIDESPREAD SHOWER AND THUNDERSTORM DEVELOPMENT THIS AFTERNOON AND EVENING. DRY LIGHTING WILL BE POSSIBLE...ESPECIALLY WITH THE EARLY THUNDERSTORM DEVELOPMENT. HOWEVER BRIEF LOCALLY HEAVY RAINFALL WILL BE POSSIBLE BY THE MID TO LATE AFTERNOON HOURS INTO EARLY THIS EVENING. THUNDERSTORM OUTFLOWS UP TO 50 MPH ARE POSSIBLE WITH THE STRONGEST CELLS WHICH MAY PRODUCE AREAS OF BLOWING DUST...WHERE VISIBILITIES MAY BRIEFLY DROP BELOW A HALF OF A MILE. ALL ACTIVITY WILL COME TO AN END BY MIDNIGHT. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. A FEW SHOWERS AND THUNDERSTORMS ARE POSSIBLE THURSDAY ACROSS GRAHAM...COCHISE AND GREENLEE COUNTIES. ELSEWHERE ON THURSDAY IT WILL BE DRY. MUCH WARMER TEMPERATURES ARE IN THE FORECAST FOR THIS WEEKEND INTO EARLY NEXT WEEK. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. WEATHER.GOV/TUCSON
The Tucson radar (KEMX), 61 km away, was scanning. The volume nearest the first event began at 20:01 UTC.
2 hail, 1 tornado, 1 strong wind. Local standard time, as filed.
A dust devil briefly spun up into a landspout tornado just south of Rio Rico.
Hail up to the size of pennies covered the ground in Rio Rico.
Several four inch diameter tree limbs were broken in eastern sections of Tucson. The Tucson ASOS measured a peak gust of 52 mph.
Hail up to the size of pennies covered the ground in Douglas. Heavy rain and minor street flooding accompanied the hail.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Arizona in 2012Every state in 2012This day in weather historyThe tornado archive for Arizona, 2012Warnings in Arizona, May 2012
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: 374733, 374734, 374722, 374735.