Tropical Storm ALEX

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TROPICAL STORM ALEX DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL012010
400 AM CDT SUN JUN 27 2010
 
RATHER THAN BECOMING DISORGANIZED AFTER MOVING INLAND...RADAR AND
SATELLITE DATA INDICATE THAT ALEX HAS ACTUALLY BECOME MUCH BETTER
DEFINED. AN EYE FEATURE HAS BEEN NOTED IN BELIZE RADAR DATA AND
SATELLITE IMAGERY INDICATES THAT CLOUD TOPS HAVE COOLED
SIGNIFICANTLY WITH A NEARLY CLOSED RING OF -80C AND COLDER TOPS
ENCIRCLING THE RADAR CENTER. THE UPPER-LEVEL OUTFLOW PATTERN
REMAINS IMPRESSIVE AND ADDITIONAL CONVECTIVE BANDING FEATURES HAVE
DEVELOPED IN ALL QUADRANTS. THE RADAR AND SATELLITE DEPICTIONS OF
ALEX LOOKS MORE LIKE A HURRICANE THAN A LOW-END TROPICAL STORM.

THE MOTION ESTIMATE IS 300/10. THE SHORT TERM MOTION IS THE ONLY
THING STRAIGHT-FORWARD ABOUT THE FORECAST TRACK. ALL OF THE MODELS
AGREE ON AN UPPER-LEVEL LOW CURRENTLY JUST EAST OF HUDSON BAY
CANADA TO DIG SOUTHWARD AND CARVE OUT A DEEP TROUGH OVER MUCH OF
THE EASTERN U.S. DURING THE NEXT 5 DAYS. AS THE TROUGH AMPLIFIES
...THE SUBTROPICAL RIDGE CURRENTLY SITUATED ACROSS FLORIDA AND THE
NORTHERN GULF OF MEXICO ERODES IN THE 36-72 HOUR TIME FRAME LEAVING
A LARGE WEAKNESS IN THE RIDGE OVER THE CENTRAL AND WESTERN GULF.
THIS WEAK FLOW PATTERN IS EXPECTED TO CAUSE ALEX TO SLOW DOWN AND
ALLOW THE CYCLONE TO GAIN SOME LATITUDE. AFTER THAT...HOWEVER...THE
MODELS DIVERGE SIGNIFICANTLY WITH THE GFS AND CANADIAN MODELS
TAKING ALEX NORTHWARD THROUGH THE WEAKNESS IN THE RIDGE TO THE
TEXAS-LOUISIANA BORDER AREA...WHEREAS THE ECMWF...NOGAPS...GFDL...
HWRF...UKMET...AND GFS-PARALLEL MODELS MOVE ALEX WESTWARD INTO
NORTHEASTERN MEXICO. THE MAIN DIFFERENCE IN THE MODELS IS HOW THEY
HANDLE THE MID-LATITUDE TROUGH-RIDGE PATTERN. THE GFS AND CANADIAN
MODELS ARE MORE PROGRESSIVE AND LESS AMPLIFIED WITH THE FLOW
PATTERN ACROSS THE NORTHERN U.S. DURING THE FORECAST PERIOD...
WHEREAS THE OTHER MODELS PRODUCE A STRONGER...MORE HIGHLY AMPLIFIED
...AND SLOWER PATTERN. THE CURRENT PROGRESSIVE 5-WAVE NORTHERN
HEMISPHERIC FLOW PATTERN WOULD TEND TO FAVOR THE THE GFS-CANADIAN
SOLUTION...BUT AT LEAST ONE MORE MODEL CYCLE WILL BE REQUIRED TO
CONFIRM THAT TREND. THE OFFICIAL FORECAST TRACK IS TO THE RIGHT OF
AND SLOWER THAN THE PREVIOUS ADVISORY...AND IS SIMILAR TO THE
CONSENSUS MODEL...TVCN. NOTE...IF THE RECENT NORTHWARD SHIFT IN THE
MODELS CONTINUES...THEN ALEX COULD REMAIN OVER WATER FOR THE NEXT 5
DAYS RESULTING IN A VERY POWERFUL HURRICANE.

BASED ON THE MUCH IMPROVED STRUCTURE OF ALEX WHILE IT IS HAS BEEN
OVER LAND...THE INTENSITY FORECAST HAS BEEN ADJUSTED UPWARD FROM
THE PREVIOUS ADVISORY. WITH VERTICAL SHEAR FORECAST TO BE 5 KT OR
LESS DURING MOST OF THE FORECAST PERIOD AND SSTS OF 28C AND WARMER
EXPECTED ALONG THE TRACK...THERE IS AT LEAST A MODERATE LIKELIHOOD
THAT ALEX COULD BECOME A MAJOR HURRICANE. THE OFFICIAL INTENSITY
FORECAST IS NEARLY IDENTICAL TO THE SHIPS AND DECAY-SHIPS INTENSITY
MODELS...AND HIGHER THAN BOTH THE GFDL AND HWRF MODELS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      27/0900Z 18.3N  89.4W    35 KT
 12HR VT     27/1800Z 19.1N  90.6W    30 KT...INLAND
 24HR VT     28/0600Z 20.2N  91.9W    40 KT...OVER WATER
 36HR VT     28/1800Z 20.9N  92.8W    55 KT
 48HR VT     29/0600Z 21.5N  93.6W    65 KT
 72HR VT     30/0600Z 22.6N  95.5W    75 KT
 96HR VT     01/0600Z 23.2N  97.4W    85 KT
120HR VT     02/0600Z 23.5N  99.7W    30 KT...INLAND
 
$$
FORECASTER STEWART
 
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