Severe Thunderstorm Warning 47, NWS Tucson, AZ

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
900 AM MST MON AUG 28 2000

SYNOPSIS...AN ACTIVE MONSOON PATTERN WILL CONTINUE FOR THE NEXT FEW
DAYS. MOISTURE WILL REMAIN OVER THE AREA AS A SERIES OF DISTURBANCES
MOVES NORTHWEST OUT OF MEXICO. LOCALLY HEAVY RAINS WILL BE THE
PRIMARY THREAT. BY THE END OF THE WEEK...A SIGNIFICANT CHANGE IN THE
PATTERN WILL OCCUR AS A TROUGH OF LOW PRESSURE DEVELOPS ALONG THE
WEST COAST. THIS WILL SWITCH OUR FLOW TO THE SOUTHWEST AND PUSH THE
MONSOON EAST OF THE REGION.

DISCUSSION...THE DOGS OF WAR ARE BARKING LOUDLY AS UPPER LEVEL
DYNAMICS BECOME EVEN MORE FAVORABLE FOR WIDESPREAD HEAVY RAIN LATE
THIS AFTERNOON/TONIGHT. UPPER LOW JUST S OF THE BAJA SPUR HAS TAKEN
ON A NEGATIVE TILT. CENTRAL AZ REMAINS IN THE RIGHT-REAR QUAD OF AN
ANTICYCLONICALLY-CURVED UPPER JET EXTENDING UP THE COLORADO RIVER
AND INTO UT. PRECIP WATERS ARE 1.5-1.7". 12Z SOUNDING WAS HEAVILY
CONTAMINATED (MODIFYING IT GAVE ME AN AFTERNOON CAPE OF 2500J/KG),
SO WE'RE SENDING UP AN 18Z BALLOON TO SEE NOT ONLY OUR POTENTIAL
INSTABILITY, BUT ALSO SEE HOW OUR STEERING FLOW IS DOING. THAT MAY
BE THE KEY TO OUR FLASH FLOOD POTENTIAL TONIGHT SINCE 12Z ETA
INCREASES OUR 500MB FLOW TO 30KTS. WITH SUCH WEAK TEMP GRADIENTS,
THAT KIND OF FLOW INCREASE IMPLIES SIGNIFICANT AGEOSTROPHIC
ADJUSTMENT (TRANSLATED: A LOT OF UPWARD MOTION). IF THAT WERE TO
OCCUR, THOUGH, WE'D END UP WITH THE SAME SITUATION WE HAD LAST
NIGHT: HEAVY RAINERS, BUT NOTHING WORTHY OF A WATCH SINCE STORMS
WON'T STICK AROUND IN ANY ONE PLACE. IF THINGS DO HANG, THOUGH, OUR
SOILS ARE NOW PRETTY SATURATED. BASED ON THE RAPID REACTION ON THE
SAN PEDRO RIVER THIS MORNING, A 2-3" RAIN COULD CAUSE A LOT OF
PROBLEMS. FOR NOW, MY INCLINATION IS TO WAIT AND SEE NOT ONLY THE
18Z SOUNDING, BUT THE COMPLETE SUITE OF MODEL PRODUCTS INCLUDING THE
18Z MESOETA. WE'LL MAKE SOME TWEAKS TO AFTERNOON WORDING, BUT THAT'S
ABOUT IT UNTIL THE AFTERNOON PACKAGE.

UPPER LEVEL ANTICYCLONIC SHEAR DIMINISHES SOMEWHAT ON TUE, BUT
PIECES OF ENERGY WILL CONTINUE TO LIFT THIS WAY AS THE UPPER LOW
ALONG 130W GETS A KICK E BY THE ENERGY TOPPING THE CENTRAL PACIFIC
UPPER RIDGE. BY THU, MODELS ARE AGAIN UNANIMOUS IN SHOVING THE
MONSOON OUT OF HERE, WITH THE POSSIBILITY OF A TRANSITIONAL SEVERE
WEATHER EPISODE ON WED. BY DAY 7-8, THE MEAN TROUGH ACTUALLY SETS UP
OVERHEAD, WHIC3H COULD GIVE US SOME PRETTY PLEASANT WEATHER FOR EARLY
SEP. PYTLAK

.TWC...NONE.

AZZ019-029>035-290600-

HAZARDOUS WEATHER OUTLOOK...SOUTHEAST ARIZONA CONVECTIVE OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1045 AM MST MON AUG 28 2000

                           *CONDITIONAL*   *CONDITIONAL*
COUNTY             AREAL    PROBABILITY  RAIN GREATER THAN   STORM
                  COVERAGE   OF SEVERE     1.00      2.00    MOTION

COCHISE              70          10         40        20     NNW 10
GRAHAM               65          10         30        15     NNW 10
GREENLEE             80          10         50        20     NNW 10
TUCSON/ERN PIMA      60          10         30        15     NNW 10
TOHONO OODHAM       55          10         30        15     NNW 10
SOUTHEAST PINAL      55          10         30        15     NNW 10
WESTERN PIMA         50          10         30        15     NNW 10
SANTA CRUZ           70          10         40        20     NNW 10

SYNOPSIS...THERE HAS BEEN LITTLE CHANGE IN THE VERY MOIST ATMOSPHERE
IN PLACE OVER SOUTHERN ARIZONA. WEAK DISTURBANCES ARE LINED UP FROM
ARIZONA INTO THE SOUTHERN GULF OF CALIFORNIA...ALL OF WHICH ARE
HEADING IN OUR GENERAL DIRECTION. STORM MOTION WILL BE THE KEY TO
HOW HEAVY THE RAIN WILL BE THIS AFTERNOON AND TONIGHT. THE STORMS
LAST NIGHT MOVED FAST ENOUGH TO PREVENT SIGNIFICANT PROBLEMS SINCE
THEY WERE UNABLE TO STAY IN ANY ONE PLACE. AN ADDITIONAL WEATHER
BALLOON HAS BEEN SENT UP TO ASCERTAIN HOW MUCH THE MID LEVEL
STEERING FLOW HAS CHANGED. IF IT APPEARS THE STORMS THIS EVENING
WILL MOVE MORE SLOWLY...A FLASH FLOOD WATCH MAY HAVE TO BE ISSUED
LATER TODAY. BECAUSE THE ATMOSPHERE IS SO MOIST AND UNSTABLE...
STORMS ARE LIKELY TO CONTINUE WELL INTO THE NIGHT.

*****************************************************************
KEY...
AREAL COVERAGE - PERCENT OF COUNTY OR AREA THAT WILL EXPERIENCE
                 THUNDERSTORMS
PROB OF SEVERE - THE PROBABILITY THAT ANY ONE OF THE STORMS WILL
                 REACH SEVERE LEVELS (DAMAGING WIND AND/OR
                 LARGE HAIL)
RAIN GRTR THAN - THE PROBABILITY THAT ANY ONE OF THE STORMS WILL
                 PRODUCE RAIN EXCEEDING 1 INCH OR 2 INCHES IN
                 ANY LOCATION
STORM MOTION   - GENERAL DIRECTION TO WHICH THE STORMS WILL
                 LIKELY MOVE AND SPEED IN MPH

NOTE...
VALID TIME IS FROM 12:45 PM TO 12 MIDNIGHT OF THE DAY OF ISSUANCE.
THIS PRODUCT IS NOT TO BE USED IN PLACE OF SEVERE THUNDERSTORM OR
FLASH FLOOD WARNINGS OR WATCHES. THIS PRODUCT IS ONLY USED FOR
OUTLOOK PURPOSES. CORRESPONDING GRAPHICS MAY BE FOUND ON THE NWS
TUCSON INTERNET PAGE AT
HTTP://WWW.WRH.NOAA.GOV/TUCSON/THUNDER/SWO.SHTML

END/PYTLAK