Severe Thunderstorm Warning 51, NWS Tucson, AZ

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
200 PM MST TUE AUG 13 2002

.SYNOPSIS...A DRY NORTHWEST FLOW ALOFT WILL REDUCE THE RISK OF
THUNDERSTORMS ACROSS SOUTHEAST ARIZONA FOR THE REST OF THE WEEK.
CONTINUED MOISTURE SEEPAGE FROM THE SOUTH IN ADDITION TO NEAR RECORD
HIGHS WILL MAKE IT FEEL QUITE UNCOMFORTABLE. HIGH PRESSURE OVER
CALIFORNIA WILL EVENTUALLY SHIFT BACK INTO ARIZONA...AS ANOTHER AREA
OF HIGH PRESSURE DEVELOPS OVER THE SOUTHERN PLAINS. THIS SHOULD LEAD
TO A SOMEWHAT BETTER CHANCE OF THUNDERSTORMS EARLY NEXT WEEK.

.DISCUSSION...NOT MUCH CHANGE TO EARLIER THINKING. GULF OF CA SURGE
CONTINUES, AND BASED ON THE 6-7MB PRESSURE DIFFERENTIAL BETWEEN N
AND S ENDS OF THE GULF OF CA, WE SEE NO REASON FOR THIS TO ABATE IN
THE NEAR TERM. THE PROBLEM IS THAT ITS SHALLOW, SO ITS MERELY
TURNING OUR NORMAL DESERT HEAT INTO SOMETHING MORE TYPICAL FOR S TX
OR THE MIDWEST. WILL ISSUE AN SPS HIGHLIGHTING THE SOMEWHAT UNUSUAL
HEAT/HUMIDITY COMBINATION, BUT AGAIN, IT APPEARS THE HEAT INDEX
VALUES WILL STAY JUST BELOW WARNING CRITERIA. SEVERAL RECORDS ARE IN
TROUBLE THROUGH FRI, EXCEPT THE 109F THAT STICKS OUT ON THU AT KTUS.
WE ARE IN A CATCH-22 WITH THIS PATTERN BECAUSE IF LOW LEVEL MOISTURE
MANAGES TO MIX OUT DURING THE AFTERNOON, TEMPS WILL MERELY GO
HIGHER. IF THE SURGE STRENGTHENS, WELL END UP A BIT COOLER BUT EVEN
MORE HUMID. WILL LEAN HEAVILY ON 850-700MB THICKNESSES SINCE MOS
GUIDANCE IS TENDING TOWARD CLIMO. ONLY THREAT OF TSTMS TONIGHT IS
ALONG THE NM AND MEXICAN BORDERS AS THE COLD FRONT OVER NM CONTINUES
TO MOVE S AND BRUSHES THE AZ/NM BORDER. ISOLATED TSTMS HAVE FIRED ON
THE RIM, BUT BASED ON SATELLITE AND SURFACE DEWPOINTS, THEY ARE
MAINLY DRY ONES. I ALSO WOULDNT BE SURPRISED TO SEE A STRONG
OUTFLOW AND/OR BLOWING DUST PUSH W FROM NM OVERNIGHT, BUT ITS NOT
CLEAR HOW MUCH TSTM COVERAGE THEYLL HAVE SINCE THAT AREA IS ON THE
EDGE OF THE BETTER DYNAMICS. WELL KEEP THE WORDING PROBABALISTIC IN
COCHISE COUNTY, BUT WE WILL NOT RESTRICT THE TIMING TO JUST THE
EVENING HOURS SINCE FRONTAL TIMING ALONG THE BORDER ISNT UNTIL
AROUND 06Z OR PERHAPS A LITTLE AFTER.

ALTHOUGH MODELS ARE GROSSLY UNDERDOING THE AMOUNT OF MOISTURE
LURKING ALONG THE BORDER, ITS GOING TO BE DIFFICULT TO GET
DEVELOPMENT UNTIL THE PATTERN RESHUFFLES. THAT TRENDS STARTS FRI AS
A WEAK COLD FRONT GRAZES US TO THE N, FOLLOWED BY THE MEAN RIDGE
RECENTERING NEARBY. IF THE OPERATIONAL AVN IS RIGHT AND IT ENDS UP
IN SONORA, WELL STAY DRY RIGHT ON THROUGH DAY 7. HOWEVER, THE
OPERATIONAL AVN HAS DEVELOPED A RIDGE TO OUR S TWICE IN THE PAST
MONTH, AND BOTH TIMES IT ENDED UP TO OUR N WITH TSTM OUTBREAKS
ACROSS THE SE 2/3 OF OUR CWA. ENSEMBLE MEAN, ECMWF AND UKMET INSIST
ON DEAMPLIFYING THE PATTERN AFTER FRI AND KEEPING THE NEXT NORTHERN
BRANCH SYSTEM CLOSE TO THE CANADIAN BORDER. THAT SOLUTION HAS MORE
TELECONNECTIVE SUPPORT AND WOULD ALLOW PLENTY OF ROOM FOR NOT ONLY
THE BERMUDA HIGH TO BUILD WEST INTO TX, BUT ALSO FOR THE DESERT
SOUTHWEST HIGH TO END UP JUST TO OUR N. THATS STILL A CHANCEY
LOW-MID GRADE PATTERN, BUT ITS NOT AS UNFAVORABLE AS THE PATTERN
WERE IN NOW, AND ITS HARD TO IGNORE THE 2+ PRECIP WATERS JUST
60-80MI AWAY. WELL CONTINUE THE TREND OF EXPANDING THE TSTM RISK NW
LATER THIS WEEKEND. PYTLAK

.TWC...NONE.

AZZ019-029>035-140700-

SOUTHEAST ARIZONA HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1145 AM MST TUE AUG 13 2002

.SYNOPSIS...LOW LEVEL MOISTURE CONTINUES TO MOVE INTO THE ARIZONA
FROM THE GULF OF CALIFORNIA BUT UPPER LEVEL NORTHERLY FLOW IS
UNFAVORABLE FOR THUNDERSTORM DEVELOPMENT EVERYWHERE EXCEPT THE FAR
SOUTHEAST.

.DISCUSSION...BOTH SEVERE AND PROBABILITY OF ONE INCH ARE NEAR OR AT
ZERO DUE TO UNFAVORABLE UPPER LEVEL WINDS. AT NIGHT THE LOWER
LEVELS MOISTEN WITH FLOW OF MOISTURE FROM THE SOUTH BUT DURING THE
DAY THE UPPER LEVEL WINDS TRANSPORT IN DRY AIR...AND THROUGH MIXING
THE ENTIRE LAYER MOISTURE CONTENT IS NOT HIGH ENOUGH TO SUPPORT
THUNDERSTORMS. THERE IS SOME LIMITED POTENTIAL FOR THUNDERSTORMS IN
THE FAR SOUTHEAST THIS EVENING FROM STORMS THAT DEVELOP IN NEW
MEXICO AND MOVE INTO FAR SOUTHEAST ARIZONA.

MOTION OF THE STORMS WILL BE TO THE SOUTHWEST AT 10 MPH.

AZZ029>035-151000-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE TUCSON AZ
200 PM MST TUE AUG 13 2002

...NEAR RECORD HEAT AND RATHER HIGH HUMIDITY EXPECTED FOR THE REST
OF THE WEEK...

HIGH PRESSURE EXTENDING FROM CALIFORNIA INTO ARIZONA WILL KEEP THE
AREA UNUSUALLY WARM FOR MID AUGUST THROUGH FRIDAY. VALLEY AND DESERT
HIGH TEMPERATURES ARE EXPECTED TO HOVER NEAR RECORDS RANGING FROM
THE MID 90S TO NEAR 110. ALTHOUGH SUCH HOT TEMPERATURES ARE COMMON
DURING THE SUMMER IN SOUTHEAST ARIZONA...IT IS SOMEWHAT UNUSUAL FOR
BUILDING HEAT IN MID AUGUST TO BE ACCOMPANIED BY RATHER HIGH
HUMIDITY. CONTINUED MOISTURE SEEPAGE OUT OF THE GULF OF CALIFORNIA
WILL KEEP DEWPOINTS IN THE 50S AND 60S THROUGH AT LEAST FRIDAY...
WHICH WILL MAKE IT FEEL QUITE UNCOMFORTABLE. THE HIGHER DEWPOINTS
WILL ALSO KEEP LOW TEMPERATURES FROM COOLING OFF MUCH AT NIGHT...AND
GENERALLY LIGHT WINDS WILL PROVIDE LITTLE RELIEF.

THE COMBINATION OF HEAT AND HUMIDITY WILL MAKE IT MORE HAZARDOUS
THAN USUAL TO BE OUTDOORS DURING THE AFTERNOON HOURS. IF YOU MUST BE
OUTDOORS DURING THE HOTTEST TIME OF DAY...IT WOULD BE WISE TO CARRY
PLENTY OF ADDITIONAL WATER...WEAR LIGHT AND LOOSE-FITTING
CLOTHING...AND STAY OUT OF THE SUN. IT MAY ALSO A GOOD IDEA TO SHIFT
ANY STRENUOUS OUTDOOR ACTIVITIES TO THE COOLEST TIME OF DAY JUST
BEFORE SUNRISE.

PYTLAK

AZZ029>035-151000-

SPECIAL WEATHER STATEMENT...CORRECTION
NATIONAL WEATHER SERVICE TUCSON AZ
200 PM MST TUE AUG 13 2002

...NEAR RECORD HEAT AND RATHER HIGH HUMIDITY EXPECTED FOR THE REST
OF THE WEEK...

HIGH PRESSURE EXTENDING FROM CALIFORNIA INTO ARIZONA WILL KEEP THE
AREA UNUSUALLY WARM FOR MID AUGUST THROUGH FRIDAY. VALLEY AND DESERT
HIGH TEMPERATURES ARE EXPECTED TO HOVER NEAR RECORDS RANGING FROM
THE MID 90S TO NEAR 110. ALTHOUGH SUCH HOT TEMPERATURES ARE COMMON
DURING THE SUMMER IN SOUTHEAST ARIZONA...IT IS SOMEWHAT UNUSUAL FOR
BUILDING HEAT IN MID AUGUST TO BE ACCOMPANIED BY RATHER HIGH
HUMIDITY. CONTINUED MOISTURE SEEPAGE OUT OF THE GULF OF CALIFORNIA
WILL KEEP DEWPOINTS IN THE 50S AND 60S THROUGH AT LEAST FRIDAY...
WHICH WILL MAKE IT FEEL QUITE UNCOMFORTABLE. THE HIGHER DEWPOINTS
WILL ALSO KEEP LOW TEMPERATURES FROM COOLING OFF MUCH AT NIGHT...AND
GENERALLY LIGHT WINDS WILL PROVIDE LITTLE RELIEF.

THE COMBINATION OF HEAT AND HUMIDITY WILL MAKE IT MORE HAZARDOUS
THAN USUAL TO BE OUTDOORS DURING THE AFTERNOON HOURS. IF YOU MUST BE
OUTDOORS DURING THE HOTTEST TIME OF DAY...IT WOULD BE WISE TO CARRY
PLENTY OF ADDITIONAL WATER...WEAR LIGHT AND LOOSE-FITTING
CLOTHING...AND STAY OUT OF THE SUN. IT MAY ALSO BE A GOOD IDEA TO
SHIFT STRENUOUS OUTDOOR ACTIVITIES TO THE COOLEST TIME OF DAY JUST
BEFORE SUNRISE.

PYTLAK
CORRECTED TYPO IN LAST PARAGRAPH