Severe Thunderstorm Warning 58, NWS Tucson, AZ

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
916 AM MST WED AUG 29 2001

.SYNOPSIS...MOISTURE SURGING NORTH FROM THE GULF OF CALIFORNIA WILL
LEAD TO AN UPSWING IN THUNDERSTORMS THIS AFTERNOON AND EVENING.
SLIGHTLY DRIER AIR MAY WORK IN FROM THE NORTHWEST THURSDAY AND
FRIDAY...BUT A DEEP SOUTHERLY FLOW WILL DEVELOP BY SATURDAY. THIS
WILL COMBINE WITH DAYTIME HEATING TO GENERATE SCATTERED  AFTERNOON
AND EVENING THUNDERSTORMS THROUGH THE UPCOMING HOLIDAY WEEKEND.

.DISCUSSION...DAY 3 OF OUR ONGOING GULF SURGE HAS BEEN THE BEST SO
FAR. SURFACE WINDS GUSTED OVER 40 MPH IN SW AZ OVERNIGHT, WITH MINOR
GRADIENT WIND DAMAGE REPORTED IN AJO JUST BEFORE DAYBREAK. LATEST
KYUX PROFILER SHOWS 35KTS UP TO 4KFT, WHICH IS WEAKER COMPARED TO
40-45KTS OVERNIGHT. SURFACE WINDS ARE WEAKENING, BUT THATS BECAUSE
THE SURGE IS DEEPENING WITH THE BOUNDARY LAYER AND MIXING OUT A BIT.
THIS MAJOR GULF SURGE IS OCCURRING IN TANDEM WITH OUTFLOW MOISTURE
MOVING NORTH FROM AND MCS OVER SONORA LAST NIGHT. SURFACE DEWPOINTS
ARE WELL INTO THE 50S AND 60S THIS MORNING WITH THE 850MB KTUS
DEWPOINT AT 17C. WE ARE DEFINITELY BACK INTO MONSOON MOISTURE. MID
SHIFT VERY WISELY RAISED POPS AND LOWERED TEMPS ACROSS THE BOARD
AFTER RECEIVING THE 12Z SOUNDINGS.

WHATS GOING TO HAPPEN WHEN WE GET INTO THE LEFT-FRONT QUAD OF THE
60KT UPPER JET APPROACHING S CA? IF WE WERE TO TAKE THE 12Z KTUS
SOUNDING AT FACE VALUE (PRECIP WATER 1.53, MODIFIED CAPE OVER 2000
J/KG), WE ARE AT RISK FOR HAVING OUR BIGGEST SEVERE WEATHER AND
FLASH FLOOD OUTBREAK OF THE YEAR. HOWEVER, I HAVE MY DOUBTS THAT THE
ATMOSPHERE IS AS UNSTABLE AS INDICATED AT 12Z. SE AZ IS CURRENTLY IN
THE LEFT-REAR QUAD OF A 50KT UPPER JETLET NEAR KELP. GOES-10 PRECIP
WATER IMAGERY HAS SHOWED A FAIR AMOUNT OF DRYING OVER SE AZ SINCE
12Z, AND SINCE OUR FLOW IS WEAK, THE DRYING MUST BE COMING FROM THE
JET-INDUCED SUBSIDENCE. THAT SUBSIDENCE MAY BE ENOUGH TO EITHER CAP
US OFF OR AT LEAST KEEP TSTMS ISOLATED. HAVE REQUESTED AN 18Z
SOUNDING TO DETERMINE HOW STRONG THIS SUBSIDENCE REALLY IS. IF IT
LOOKS LIKE IT CAN BE OVERCOME BY THE EXPECTED 300-200MB DIVERGENCE
AND WEAKENING INERTIAL STABILITY,  WELL UPDATE TO ADD HEIGHTENED
WORDING, RAISE POPS EVEN HIGHER, AND MAY EVEN CONSIDER A FLASH FLOOD
WATCH IF THE LOW LEVEL FLOW DOESNT PICK UP FROM THE 10KTS WERE AT
NOW. IM HESITANT ABOUT RAISING THE ANTE FOR ANOTHER REASON: THIS IS
THE NONSOON OF 2001. WE HAVE HAD CLASSIC SOUNDINGS LIKE THIS
SEVERAL TIMES THIS YEAR CANCELED OUT BY A COOL, WORKED-OVER BOUNDARY
LAYER WHICH REFUSED TO HEAT UP. THE MID SHIFTS ADJUSTMENT IS
EXACTLY WHAT THE DOCTOR ORDERED UNTIL WE SEE HOW MUCH STAYING POWER
THE SURGE HAS, WHAT OUR 18Z SOUNDING LOOKS LIKE, AND HOW THE MODELS
RESPOND TO ALL THIS INFO. PYTLAK

.TWC...NONE.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TUCSON ARIZONA
0849 AM MST WED AUG 29 2001

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

0400 AM    AJO                       AZ   NON TSTM WND DAMAGE
08/29/01   PIMA                           SEVERAL SMALL...RECENTLY PLANTED
                                          STARTER TREES UPROOTED. TIME
                                          APPROXIMATE.

AZZ019-029>035-300700-

SOUTHEAST ARIZONA HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1230 PM MST WED AUG 29 2001

.SYNOPSIS...FOR THE THIRD DAY IN A ROW...CONSIDERABLE MOISTURE HAS
SURGED OUT OF THE GULF OF CALIFORNIA. SOUTH WINDS GUSTED UP TO 45
MPH OVER SOUTHWEST ARIZONA EARLIER THIS MORNING. IN ADDITION...AN
UPPER LEVEL DISTURBANCE OVER SOUTHERN CALIFORNIA IS EXPECTED TO PASS
ACROSS ARIZONA THIS EVENING. THE COMBINATION OF THE TWO IS EXPECTED
TO PRODUCE SCATTERED STRONG THUNDERSTORMS ACROSS THE REGION THIS
AFTERNOON AND EVENING.

.DISCUSSION...SOUTH WINDS UP TO 45 MPH POURED MOISTURE OFF THE GULF
OF CALIFORNIA LAST NIGHT. DEWPOINTS HAVE RISEN TO NEAR 60...WITH
PRECIPITABLE WATERS UP NEAR 1.4 INCHES ACCORDING TO A SPECIAL
WEATHER BALLOON SENT UP BEFORE 1100 AM. AN UPPER LEVEL JET STREAK IS
MOVING INTO SOUTHERN CALIFORNIA AND IS ALREADY STARTING TO INDUCE
DIVERGENCE ALOFT. TEMPERATURES IN THE MID AND UPPER LEVELS OF THE
ATMOSPHERE HAVE COOLED CONSIDERABLY SINCE MONDAY WITH LITTLE IF ANY
CAPPING INVERSION TO IMPEDE THUNDERSTORM DEVELOPMENT. THE ONLY THING
WHICH MAY PREVENT AN OUTBREAK OF SEVERE THUNDERSTORMS AND FLASH
FLOODING IS THE FACT THAT STEERING WINDS ARE VERY WEAK THIS
AFTERNOON. THESE WEAK WINDS WILL MAKE IT DIFFICULT FOR THUNDERSTORMS
OR ORGANIZED OUTFLOWS TO MOVE OFF THE MOUNTAINS. THOSE SAME WEAK
WINDS...HOWEVER...INCREASE THE THREAT OF FLASH FLOODING IN THE
MOUNTAINS. IF THE STORMS GROW LARGER AND BECOME MORE NUMEROUS
THROUGH MID AFTERNOON...A FLASH FLOOD WATCH MAY BECOME NECESSARY FOR
PARTS OF SOUTHEAST ARIZONA.

THERE WILL BE A SHARP WESTERN EDGE TO THUNDERSTORM DEVELOPMENT AND
STRENGTH THIS AFTERNOON AND EVENING. UPPER LEVEL TEMPERATURES ARE
SEVERAL DEGREES WARMER OVER THE WESTERN DESERTS. THAT SHOULD BE
ENOUGH TO CAP DEVELOPMENT WEST OF SELLS. THE RISK OF SEVERE
THUNDERSTORMS AND FLASH FLOODING INCREASES AS ONE LOOKS FURTHER
EAST...ESPECIALLY EAST AND SOUTH OF TUCSON.

STORM MOTION WILL BE TO THE SOUTH AT 5 TO 10 MPH.

PYTLAK