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Hurricane MARTY (Text)

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TROPICAL DEPRESSION MARTY DISCUSSION NUMBER  21
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
8 PM PDT TUE SEP 23 2003
 
SATELLITE IMAGERY AND WSR-88D RADAR DATA FROM YUMA ARIZONA INDICATE
THAT MARTY HAS BECOME A LITTLE BETTER ORGANIZED THIS EVENING...EVEN
THOUGH CONVECTIVE CLOUD TOPS HAVE WARMED SIGNIFICANTLY. THE YUMA
RADAR INDICATES A NEW BAND HAS DEVELOPED TO THE SOUTHWEST AND IS
WRAPPING EASTWARD AROUND THE SOUTHERN SEMICIRCLE...WITH CELL MOTION
APPROACHING 40 KT. OTHER NEW CONVECTION OF 40-45 DBZ HAS DEVELOPED
NEAR THE CENTER...WITH A LARGE FIELD OF 30-40DBZ ECHOES LOCATED IN
THE NORTHERN SEMICIRCLE. IN ADDITION... DOPPLER VELOCITIES OF 35-40
KT BETWEEN 9000 AND 11000 FT ARE INDICATED JUST NORTHEAST OF THE
CENTER...WHICH SUGGESTS THAT THERE IS PROBABLY AT LEAST 30 KT AT
THE SURFACE. SATELLITE INTENSITY ESTIMATES OF 35/30/30 FROM
TAFB/SAB/AFWA ALSO SUPPORT AN INTENSITY OF 30 KT...ALBEIT LIKELY
OVER JUST A VERY SMALL AREA IN THE NORTHEAST QUADRANT.

THE INITIAL MOTION ESTIMATE IS 345/06. MARTY HAS ACTUALLY BEEN
MOVING AT 8-9 KT DURING THE PAST 6 HOURS...BUT THE LAST COUPLE OF
HOURS OF YUMA RADAR DATA SUGGESTS THAT MARTY IS MOVING A LITTLE
SLOWER. THE NHC MODEL GUIDANCE IS ALL OVER THE COMPASS...WHICH
USUALLY SUGGESTS SLOW OR NO FORWARD SPEED. THE BIG QUESTION IS WILL
THE SURFACE CENTER MOVE INLAND. MOST OF THE MODEL GUIDANCE SAYS NO
AND THEY KEEP THE REMNANT CIRCULATION OVER THE GULF OF CALIFORNIA.
HOWEVER...THIS MAY BE AN ARTIFACT OF THE VORTEX TRACKER SINCE SOME
OF THE GLOBAL MODELS BRING THE 850 MB CENTER JUST INLAND OVER
EXTREME NORTHWESTERN MAINLAND MEXICO IN ABOUT 12 HOURS. MOST OF THE
NHC MODELS ALSO TAKE THE 500 MB CENTER INLAND NEAR EXTREME
SOUTHWESTERN ARIZONA AND THEN TURN IT WESTWARD. THE OFFICIAL
FORECAST MOVES MARTY SLOWLY NORTHWARD AND INLAND IN ABOUT 12 HOURS
OR SO BEFORE TURNING IT SLOWLY NORTHWESTWARD. THIS IS BASED ON THE
PREMISE THAT THE CIRCULATION WILL REMAIN DEEP ENOUGH...AS SUGGESTED
BY RADAR IMAGERY...AND GET PUSHED NORTHWARD BY THE DEEP SOUTHERLY
FLOW ON THE EAST SIDE OF LOW PRESSURE SYSTEM LOCATED IN WATER VAPOR
IMAGERY ABOUT 650 NMI WEST OF SAN DIEGO. AFTER MOVING INLAND...
MARTY SHOULD RAPIDLY WEAKEN INTO A REMNANT LOW...IF NOT SOONER.
 
LOCALLY HEAVY RAINFALL APPEARS LIKELY OVER NORTHWESTERN MAINLAND
MEXICO...THE NORTHEASTERN BAJA PENINSULA...AND EXTREME SOUTHERN
ARIZONA APPEARS LIKELY GIVEN THE RELATIVELY SLOW FORWARD SPEED AND
INCREASING UPPER-LEVEL DIFLUENCE. COORDINATION WITH WFO PHOENIX
INDICATES THAT RAINFALL TOTALS OF 2 TO 4 INCHES OVER SOUTHWESTERN
ARIZONA TONIGHT AND TOMORROW MORNING MAY APPROACH FLASH FLOOD
GUIDANCE VALUES.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      24/0300Z 30.9N 113.9W    30 KT
 12HR VT     24/1200Z 31.4N 114.0W    25 KT...DISSIPATING
 24HR VT     25/0000Z 31.8N 114.2W    20 KT...DISSIPATING INLAND
 36HR VT     25/1200Z 32.3N 114.4W    20 KT...REMNANT LOW INLAND
 48HR VT     26/0000Z...DISSIPATED INLAND
 
 
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