Dust Storm in Arizona, July 10, 2002

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
145 PM MST WED JUL 10 2002

.SYNOPSIS...STRONG HIGH PRESSURE OVER UTAH WILL KEEP DEEP EASTERLY
FLOW OVER THE REGION FOR THE REST OF THE WEEK. THIS WILL STEER A
SERIES OF DISTURBANCES OFF THE GULF OF MEXICO AND SOUTHERN PLAINS...
LEADING TO A DAILY RISK OF THUNDERSTORMS THROUGH EARLY NEXT WEEK.
ONE SUCH DISTURBANCE IS EXPECTED TO APPROACH THE AREA THIS
EVENING...WITH A SOMEWHAT STRONGER ONE EXPECTED THURSDAY NIGHT.

.DISCUSSION...YET ANOTHER DAY WHERE A SUBTLE MID LEVEL FEATURE COULD
CAUSE US PROBLEMS HEADING INTO THE EVENING. WATER VAPOR AND WHITE
SANDS WIND PROFILER SHOW ANOTHER WEAK RIPPLE HEADING W ACROSS NM
THIS AFTERNOON, WHICH IS APPARENTLY HELPING THE CONVECTION ALONG
OVER THE WHITES AND GILA MOUNTAINS OF NM. UNLIKE YESTERDAY WHERE OUR
CWA WAS WORKED OVER RELATIVELY EARLY IN THE AFTERNOON...SKIES ARE
STILL PRETTY CLEAR WITH JUST A FEW TSTMS BUILDING OVER THE
MOUNTAINS. DEWPOINTS HAVE SLIPPED INTO THE 40S-LOWER 50S WHICH MEANS
IF SOMETHING DOES ORGANIZE AND PUSH OFF THE RIM/WHITES/GILAS, WE
COULD FACE MORE STRONG WINDS AND BLOWING DUST -- ONLY THIS TIME OVER
LARGER PORTIONS OF THE CWA. HAVE COORDINATED WITH SPC ALREADY (SEE
LATEST DAY 1 OUTLOOK), AND WELL RETAIN WIND/DUST WORDING IN THE
EVENING FORECAST.

WE WERE ALREADY ADVERTISING SOMEWHAT OF A DOWN DAY ON THU AHEAD OF
THE NEXT EASTERLY WAVE. IT COULD BE EVEN MORE DOWN IF WE GET
WORKED OVER THIS EVENING, BUT WELL STICK WITH GOING POPS UNTIL WE
GET OUT OF THE EVENING AND SEE HOW WIDESPREAD ANY RAINS END UP. A
SIGNIFICANT UPSWING STILL LOOKS GOOD FOR THU EVENING AS THE NEXT
WAVE MOVE WNW TOWARD THE BIG BEND BEFORE TURNING E INTO CHIHUAHUA
AND SONORA. AS WAS THE CASE YESTERDAY, THE MODELS PICK IT UP BUT ARE
EITHER TOO WEAK, TOO SLOW, OR NOT MOIST ENOUGH. THE INTRODUCTION OF
DYNAMICS WITH RATHER DRY LOW LEVELS AND AN INCREASE IN E FLOW COULD
MEAN A BUSY THU NIGHT, ASSUMING WE DONT GET TOO DRY AND DROP OUR
CONVECTIVE AVAILABLE POTENTIAL ENERGY (CAPE) TOO LOW. WELL CONTINUE
WITH FAIRLY HIGH POPS THU NIGHT WITH A SOMEWHAT DOWN DAY FRI. WE
HAVE YET TO HAVE A SIGNIFICANT GULF SURGE SO FAR, BUT THIS WAVE
COULD DO IT IF IT MAINTAINS INTEGRITY AS IT CROSSES SONORA. IF IT
PASSES A LITTLE TOO FAR N, WE MAY HAVE TO WAIT FOR EITHER ANOTHER
WAVE TO PASS THROUGH THE SOUTHERN GULF, OR FOR THE ENTIRE UPPER HIGH
TO SHIFT E INTO THE PLAINS. EVEN WITH THE PRECIP WATERS HOVERING
NEAR OR EVEN A LITTLE BELOW CLIMO, THE OVERALL FLOW PATTERN IS IN
MID-HIGH GRADE MONSOON THROUGH DAY 7 WITH LOTS OF ROOM FOR EASTERLY
WAVES TO PERIODICALLY ENHANCE OUR CONVECTION. WELL EVENTUALLY HAVE
TO WATCH TO OUR S (PROBABLY AFTER DAY 6) SINCE TD-4E SW OF
MANZANILLO IS STRENGTHENING NICELY AND EXPECTED TO BECOME A
HURRICANE IN 48HRS. PYTLAK

.TWC...NONE.

AZZ019-029>035-110700-

SOUTHEAST ARIZONA HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1200 PM MST WED JUL 10 2002

.SYNOPSIS...ALTHOUGH AMPLE LOW TO MID-LEVEL MOISTURE RESIDES WEST OF
TUCSON...DRYING DRYING CONTINUES TO OCCUR AT LOW-LEVELS IN THE
EASTERN VALLEYS. WITH THE LACK OF ANY UPPER LEVEL FORCING MECHANISM
TO AID IN THUNDERSTORM DEVELOPMENT...SOUTHEAST ARIZONA WILL
EXPERIENCE GENERALLY BELOW CLIMATOLOGICAL PROBABILITIES FOR
PRECIPITATION IN EXCESS OF ONE INCH AND SEVERE THUNDERSTORMS. THERE
WILL BE A SLIGHTLY HIGHER PROBABILITY FOR SEVERE THUNDERSTORMS IN
THE EASTERN VALLEYS AND A SLIGHTLY HIGHER PROBABILITY FOR HEAVY
PRECIPITATION IN THE WESTERN DESERTS.

.DISCUSSION...SATELLITE IMAGERY INDICATES THAT THE DEEP LOW AND
MID-LEVEL MOISTURE RESIDES ACROSS CENTRAL AND WESTERN PIMA COUNTY
TODAY WITH DRY LOW-LEVEL AIR PUSHING INTO THE SOUTHEAST CORNER OF
THE STATE. WITH A LACK OF ANY UPPER LEVEL FORCING MECHANISM TO AID
THUNDERSTORM DEVELOPMENT TODAY...ANY THUNDERSTORMS THAT DO DEVELOP
WILL HAVE TO RELY ON THE AMPLE SOLAR HEATING OCCURRING ACROSS THE
REGION...AND WILL REMAIN DISORGANIZED.

THUNDERSTORMS WILL BEGIN TO DEVELOP OVER THE MOUNTAINS EARLY THIS
AFTERNOON AND WILL EVENTUALLY MOVE OFF THE HIGHER TERRAIN INTO THE
VALLEYS BY LATE IN THE AFTERNOON. ALTHOUGH THESE STORMS WILL HAVE
DIFFICULTY SUSTAINING THEMSELVES OVER THE VALLEYS WITH DRY AIR AT
LOW LEVELS...THIS DOES INCREASES THE POTENTIAL FOR THESE STORMS TO
PRODUCING STRONG...GUSTY AND ERRATIC THUNDERSTORM WINDS. THE RISK OF
A SEVERE THUNDERSTORM WILL BE SLIGHTLY BELOW CLIMATOLOGY TODAY
ACROSS MOST OF THE AREA WITH NEAR CLIMATOLOGICAL PROBABILITIES IN
THE EASTERN VALLEYS WHERE LOW-LEVEL DRY AIR RESIDES.

THUNDERSTORM MOTION WILL BE TOWARD THE WEST TODAY AT 15 MPH. THOSE
THUNDERSTORMS THAT PUSH INTO CENTRAL AND WESTERN PIMA COUNTY WILL BE
CAPABLE OF PRODUCING HEAVIER RAINFALL AMOUNTS DUE TO AMPLE MOISTURE.
THEREFORE...THE RISK OF RECEIVING PRECIPITATION IN EXCESS OF ONE
INCH IS GREATER IN THE WEST TODAY. THE REGION WILL SEE BELOW
CLIMATOLOGICAL ONE INCH PROBABILITIES FOR MOST OF THE AREA WITH
PROBABILITIES NEAR CLIMATOLOGY IN THE WESTERN DESERTS.