Flash Flood in Arizona, July 8, 2001

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
900 AM MST SUN JUL 8 2001

SYNOPSIS...AN ACTIVE MONSOON FLOW PATTERN WILL RESULT IN SCATTERED
SHOWERS AND THUNDERSTORMS THROUGH THE END OF THE UPCOMING WEEK. A
DISTURBANCE MOVING WEST FROM THE GULF OF MEXICO WILL HELP FOCUS THE
STORMS LATE TONIGHT AND INTO MONDAY. BY THE END OF THE WEEK...HIGH
PRESSURE CENTERED OVER THE CENTRAL PLAINS WILL SHIFT WEST INTO
ARIZONA. THIS WILL LEAD TO SLIGHTLY WARMER TEMPERATURES AND A SLIGHT
DECREASE IN THUNDERSTORM ACTIVITY.

DISCUSSION...TODAY IS A PERFECT EXAMPLE OF HAVING TOO MUCH MOISTURE,
A LITTLE TOO MUCH UPWARD MOTION, AND ROTTEN FLOW. STATIONARY UPPER
SHEAR AXIS EXTENDING FROM NW INTO SE AZ IS STUCK BETWEEN THE UPPER
LOW OFF THE CA COAST AND THE UPPER HIGH OVER KS. I HAVE LOST ALL
HOPE WITH THE ETA THIS MORNING SINCE FOR THE 4TH RUN IN A ROW, IT
INCORRECTLY TRIES TO PUSH DRYING SW FLOW ALL THE WAY INTO AZ. THAT
IS VERY UNLIKELY NOW THAT THE W COAST UPPER LOW IS LIFTING N AND NOT
NE AS PREVIOUSLY EXPECTED. THE AVN LOOKS A LOT BETTER IN TERMS OF
HOW IT HANDLES THE SHEAR AXIS AND THE 2 OR 3 WAVES MOVING W
UNDERNEATH THE RIDGE. HOWEVER, IT IS LITTERED WITH CONVECTIVE SHORT
WAVES WITH VERY LITTLE CORRESPONDENCE TO REALITY.

ALL OF THIS IS PROBABLY MOOT, THOUGH, SINCE AREA SOUNDINGS LOOK MORE
LIKE THE GULF COAST AND NOT AZ. PRECIP WATERS IN THE 1.4-1.6" RANGE
WERE REINFORCED WITH A TROPICAL TAP FROM THE SW LAST NIGHT. KTUS
CONVECTIVE TEMP IS ONLY 85F WITH NO CAP, WHICH MEANS JUST AN HOUR OR
TWO OF HEATING WILL FIRE CONVECTION OVER THE MOUNTAINS. WEAK
CIRCULATION CENTER OVER NE PIMA COUNTY IS ALREADY HELPING TO FIRE
LOW-TOPPED SHOWERS/ISOLATED TSTMS IN PARTS OF THE TUCSON METRO. LOW
LEVEL STEERING FLOW IS PRACTICALLY NIL WHILE 300MB FLOW IS STILL IN
THE 30-40KT RANGE. THAT MEANS IF THE STORMS CAN GET TALL, THEY'LL
PRODUCE LARGE ANVILS WHICH WILL THEN SPREAD INTO THE VALLEYS AND
CHOKE OFF ANY ADDITIONAL HEATING. THE ONE AREA WHERE TSTMS COULD GET
RATHER STRONG THIS AFTERNOON IS OVER GRAHAM/COCHISE COUNTIES WHERE
SLIGHTLY DRIER AIR HAS INTRUDED FROM THE E AND WILL SET UP A DECENT
THERMAL BOUNDARY DUE TO DIFFERENTIAL HEATING. THERE IS ALSO A WEAK
SPINNER OVER SW CHIHUAHUA THAT IS SHIFTING NNW UP THE SHEAR AXIS
TOWARD THE AZ BORDER. ANY STORMS ARE LIKELY TO PRODUCE SOME BIG
RAINS ONCE AGAIN (1-2"/HR NOT OUT OF THE QUESTION), BUT THEY'LL BE
TOO ISOLATED AND DISORGANIZED TO WARRANT A WATCH OR A HEAVY RAIN
MENTION IN THE ZONES. WE'LL LOWER TEMPS A LITTLE MORE DUE TO
EXPECTED CLOUD COVER, AND BUMP SOME POPS UPWARD TO ACCOUNT FOR
LATEST RADAR TRENDS.

OUR AWFUL FLOW PATTERN SHOULD GET A LITTLE BETTER TONIGHT AND MON.
LARGE SUBTROPICAL LOW CONTINUES TO MOVE W ACROSS MEXICO ALONG THE
22ND PARALLEL. THAT'S TOO FAR S TO AFFECT US DIRECTLY, BUT THE
CIRCULATION ENVELOPE EXTENDS ALL THE WAY TO THE RIO GRANDE, AND HAS
HELPED TO GENERATE ANOTHER RIPPLE NEAR KBRO. THIS WAVE IS PUSHING
THE SOUTHERN END OF THE SHEAR AXIS TO THE W AND WILL EVENTUALLY PUT
US INTO SLIGHTLY BETTER SE LOW LEVEL FLOW. THAT WON'T BE GREAT, BUT
15KTS IN SUCH A SOUPY AIRMASS MAY BE ENOUGH. UPPER LEVEL WINDS ALSO
FALL OFF BY 12Z MON WITH SE AZ GETTING INTO AN UPPER LEVEL COL. THAT
WON'T MEAN GREAT UPPER LEVEL DYNAMICS, BUT AT LEAST THE ANVILS WON'T
RUN WAY AHEAD OF THE STORM MOTIONS. GOING POPS THROUGH MON LOOK GOOD
AT THE MOMENT, BUT I MAY HAVE TO BACK HIGHS OFF MON'S HIGHS A LITTLE
IN THE AFTERNOON PACKAGE. PYTLAK

.TWC...NONE.

AZZ019-029>035-090700-

SOUTHEAST ARIZONA HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
12 NOON MST SUN JUL 8 2001

.SYNOPSIS...A STRIPE OF DEEP MONSOON MOISTURE EXTENDING FROM ARIZONA
INTO THE SIERRA MADRES WILL REMAIN IN PLACE THROUGH TONIGHT. THIS
WILL PROVIDE A WEAK FOCUSING MECHANISM FOR SHOWERS AND THUNDERSTORMS
THIS AFTERNOON. AN UPPER LEVEL DISTURBANCE OVER CENTRAL MEXICO WILL
CONTINUE TO MOVE WEST AND MAY ENHANCE ACTIVITY ALONG THE BORDER
TONIGHT.

.DISCUSSION...ATMOSPHERIC CONDITIONS ARE SIMILAR TO YESTERDAY.
PRECIPITABLE WATERS ARE NEAR 1.5 INCHES OVER THE WESTERN TWO-THIRDS
OF SOUTHEAST ARIZONA...WITH SLIGHTLY LOWER VALUES OVER GRAHAM AND
GREENLEE COUNTIES. ALTHOUGH IT IS QUITE UNSTABLE OVER SOUTHEAST
ARIZONA...THERE ARE NO INVERSIONS TO PREVENT DEVELOPMENT...SO STORMS
HAVE BEEN POPPING UP WITH VERY LITTLE HEATING. THESE STORMS HAVE IN
TURN PRODUCED CLOUD COVER WHICH HAS KEPT ADDITIONAL DEVELOPMENT WEAK
AND ISOLATED. MORE STORMS ARE STILL EXPECTED TO FORM OVER THE
MOUNTAINS THIS AFTERNOON...BUT THEY WILL ALSO SPREAD CLOUDS AHEAD OF
THEM INTO THE VALLEYS. BECAUSE OF THE LACK OF SOLAR HEATING...
ESPECIALLY FROM SOUTHEAST PINAL COUNTY INTO SANTA CRUZ AND WESTERN
COCHISE COUNTIES...THE THREAT OF SEVERE WEATHER IS LOW. THERE IS A
SLIGHTLY HIGHER RISK OF SEVERE STORMS OVER WESTERN PIMA COUNTY...
GRAHAM COUNTY...AND GREENLEE COUNTY WHERE THERE WILL BE A LITTLE
MORE SUNSHINE TODAY...BUT THE THREAT EVEN IN THOSE AREAS IS BELOW
CLIMATOLOGY.

THE PRIMARY THREAT IS FROM ISOLATED FLASH FLOODING DUE IN LARGE PART
TO THE SLOW STORM MOTION AND HIGH HUMIDITIES. THERE IS A WEAK
CIRCULATION CENTER NEAR TUCSON WHICH MAY FOCUS SOME STORM
DEVELOPMENT...BUT THUS SAME MECHANISM WILL ALSO TEND TO KEEP CLOUD
COVER OVER THE AREA. BY THIS EVENING...LOW LEVEL WINDS WILL INCREASE
SLIGHTLY OVER SANTA CRUZ AND COCHISE COUNTIES. ALTHOUGH THE STORMS
WILL STILL MOVE SLOWLY...THE SLIGHT INCREASE MAY CAUSE A FEW STORMS
TO TRAIN. THUS...THE RISK OF FLASH FLOODING IS SLIGHTLY ABOVE
CLIMATOLOGY IN THAT AREA....AND NEAR CLIMATOLOGY ELSEWHERE.

STORM MOTION WILL BE GENERALLY NORTHWEST AT 5 MPH TODAY...BUT
INCREASE TO 10 MPH TONIGHT.

PYTLAK