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Tropical Storm ALEX (Text)

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TROPICAL STORM ALEX DISCUSSION NUMBER  10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL012010
1000 PM CDT SUN JUN 27 2010
 
AN AIR FORCE RESERVE UNIT AIRCRAFT HAS BEEN INVESTIGATING ALEX THIS
EVENING AND MEASURED A MINIMUM PRESSURE OF 991 MB AND PEAK
FLIGHT-LEVEL WINDS OF 42 KT NORTH OF THE CENTER. THE PLANE ALSO
MEASURED PEAK SFMR WINDS OF 41 KT TO THE NORTH OF THE CENTER.
SATELLITE IMAGES INDICATE THAT CENTRAL CONVECTION IS REFORMING...
BANDING FEATURES ARE GRADUALLY INCREASING...AND UPPER-LEVEL OUTFLOW
IS WELL-ESTABLISHED IN ALL QUADRANTS EXCEPT THE NORTHWEST.  BASED
UPON THE AIRCRAFT MEASUREMENTS AND THE INCREASED ORGANIZATION ON
SATELLITE IMAGES...ALEX IS ONCE AGAIN UPGRADED TO A TROPICAL
STORM...AND THE ADVISORY INTENSITY IS SET AT 40 KT.
 
ALTHOUGH THE 12-HR AVERAGE INITIAL MOTION ESTIMATE IS 300/6...
SHORTER-TERM FIXES SUGGEST THAT ALEX MAY BE MOVING EVEN SLOWER.
DURING THE FORECAST PERIOD...GLOBAL MODELS FORECAST AN UNUSUALLY
DEEP LONGWAVE TROUGH TO DEVELOP OVER THE NORTHEASTERN UNITED STATES
WHICH SHOULD RESULT IN A TEMPORARY WEAKENING OF MID-LEVEL RIDGING
ALONG THE NORTHERN GULF COAST. THE GFS/CANADIAN MODELS CONTINUE TO
INDICATE A WEAKER VERSION OF THE MID-LEVEL RIDGE AND HENCE A MORE
NORTHWESTERLY OR NORTH-NORTHWESTERLY MOTION...WHILE THE ECMWF/
UKMET/NOGAPS HAVE CONSISTENTLY PREDICTED A STRONGER RIDGE AND MOVE
ALEX ON A MORE WEST-NORTHWESTERLY COURSE. THE OFFICIAL NEW FORECAST
IS QUITE SIMILAR TO THE PREVIOUS ADVISORY...AND CLOSELY FOLLOWS A
CONSENSUS OF THE DYNAMICAL MODELS THAT EXCLUDES THE GFS...SINCE THE
LATTER MODEL APPEARS TO BE SOMEWHAT OF A NORTHERN OUTLIER AT THIS
TIME.
 
NOW THAT THE CENTER OF ALEX HAS EMERGED OVER THE GULF OF
MEXICO...GLOBAL MODELS PREDICT AN ENVIRONMENT CHARACTERIZED BY
LIGHT VERTICAL WIND SHEAR AS ALEX MOVES OVER WARM WATERS. BOTH OF
THESE INGREDIENTS SHOULD FAVOR STEADY INTENSIFICATION
UNTIL LANDFALL.  PERHAPS THE ONE NEGATIVE FACTOR IS THE LARGE SIZE
OF THE CIRCULATION...AS IT MAY TAKE SOME TIME FOR THE CYCLONE TO
CONSOLIDATE FURTHER. GIVEN THE FAVORABLE LARGE-SCALE CONDITIONS...
IT IS STILL PUZZLING THAT THE GFDL/HWRF DO NOT SHOW ALEX
STRENGTHENING TO MORE THAN A TROPICAL STORM DURING THE NEXT SEVERAL
DAYS.  STATISTICAL GUIDANCE...ON THE OTHER HAND...CONTINUES TO
FORECAST A STRONGER TROPICAL CYCLONE AND THE NHC INTENSITY FORECAST
REMAINS CLOSE TO SHIPS/LGEM MODEL OUTPUT.  IN ANY EVENT...IT SHOULD
BE NOTED THAT THE SKILL OF 2 TO 3-DAY INTENSITY FORECASTS IS VERY
LOW.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      28/0300Z 19.4N  91.3W    40 KT
 12HR VT     28/1200Z 20.1N  92.0W    45 KT
 24HR VT     29/0000Z 21.0N  92.7W    50 KT
 36HR VT     29/1200Z 21.9N  93.5W    55 KT
 48HR VT     30/0000Z 22.6N  94.6W    65 KT
 72HR VT     01/0000Z 23.5N  96.7W    85 KT
 96HR VT     02/0000Z 24.3N  98.8W    50 KT...INLAND
120HR VT     03/0000Z 25.0N 101.0W    20 KT...DISSIPATING INLAND
 
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FORECASTER KIMBERLAIN/PASCH
 
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