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Tropical Storm ALEX


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TROPICAL STORM ALEX DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL012010
500 AM EDT SAT JUN 26 2010

AN AIR FORCE RESERVE HURRICANE HUNTER INVESTIGATING TROPICAL
DEPRESSION ONE REPORTED 925 MB FLIGHT-LEVEL WINDS OF 46 KT ABOUT 90
NM EAST OF THE CENTER...WHICH SUGGEST SURFACE WINDS OF NEAR 35 KT. 
THE STEPPED FREQUENCY MICROWAVE RADIOMETER ON THE AIRCRAFT SHOWED A
LARGE AREA OF WINDS NEAR 35 KT THAT DID NOT APPEAR TO BE RAIN-
CONTAMINATED.  BASED ON THIS...THE DEPRESSION IS UPGRADED TO
TROPICAL STORM ALEX WITH AN INITIAL INTENSITY OF 35 KT.  THE
AIRCRAFT DATA SUGGESTS THAT THE CIRCULATION OF ALEX REMAINS
BROAD...AND THAT THE RECENTLY REPORTED CENTRAL PRESSURE OF 1004 MB
MAY HAVE BEEN MEASURED IN A MESOSCALE LOW PRESSURE AREA.  IT SHOULD
BE NOTED THAT THE AIRCRAFT REPORTED SFMR WINDS IN EXCESS OF 40 KT
WHICH APPEAR SUSPECT DUE TO RAIN CONTAMINATION.

THE INITIAL MOTION REMAINS UNCERTAIN...WITH THE BEST ESTIMATE OF
285/7.  FOR THE NEXT 24 TO 48 HOURS ALEX IS EXPECTED TO MOVE
WEST-NORTHWESTWARD OR NORTHWESTWARD TO THE SOUTH OF A LOW/MID-LEVEL
RIDGE CENTERED OVER THE EASTERN UNITED STATES.  AFTER THAT...THE
LARGE-SCALE MODELS FORECAST THE RIDGE TO WEAKEN AS A DEEP-LAYER
TROUGH MOVES INTO THE EASTERN U. S.  THERE REMAINS A SIGNIFICANT
SPREAD IN THE MODEL GUIDANCE ON HOW THIS EVOLUTION WILL AFFECT
ALEX.  THE GFS...GFS ENSEMBLE MEAN...AND THE GFDL SHOW ENOUGH OF A
BREAK IN THE RIDGE TO STEER ALEX NORTHWARD TOWARD THE NORTHWESTERN
GULF COAST.  THE ECMWF...NOGAPS...AND UKMET SHOW THE RIDGE REMAINING
STRONG ENOUGH TO STEER ALEX GENERALLY WESTWARD INTO NORTHEASTERN
MEXICO.  THE HWRF AND THE CANADIAN MODELS ARE BETWEEN THESE
EXTREMES.  OVERALL...THE GUIDANCE ENVELOPE HAS SHIFTED WESTWARD
SINCE THE LAST ADVISORY...SO THE NEW FORECAST TRACK WILL BE NUDGED
WESTWARD AS WELL.  HOWEVER...THE NEW TRACK IS STILL A LITTLE TO THE
RIGHT OF THE CENTER OF THE GUIDANCE ENVELOPE AND THE VARIOUS
CONSENSUS MODELS.  IT IS IN BEST OVERALL AGREEMENT WITH THE HWRF.

THE LARGE-SCALE MODELS FORECAST ALEX TO BE NEAR OR UNDER A LARGE
UPPER-LEVEL ANTICYCLONE THROUGH THE FORECAST PERIOD...WHICH SHOULD
CAUSE AN ENVIRONMENT OF LIGHT VERTICAL WIND SHEAR.  AS A RESULT...
ALEX IS FORECAST TO INTENSIFY AS LONG AS IT REMAINS OVER WATER. 
THE NEW INTENSITY FORECAST CALLS FOR A 50 KT INTENSITY AS THE
CENTER REACHES THE COAST OF BELIZE OR THE YUCATAN PENINSULA...
FOLLOWED BY WEAKENING OVER LAND.  THE GFDL...SHIPS...AND LGEM
MODELS FORECAST ALEX TO BE A HURRICANE OVER THE GULF OF MEXICO. 
THE INTENSITY FORECAST WILL NOT YET DO THAT...BUT WILL CALL FOR
MORE STRENGTHENING OVER THE GULF THAN THE PREVIOUS FORECAST.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      26/0900Z 16.9N  84.9W    35 KT
 12HR VT     26/1800Z 17.4N  86.3W    45 KT
 24HR VT     27/0600Z 18.4N  88.0W    50 KT
 36HR VT     27/1800Z 19.4N  89.5W    35 KT...INLAND
 48HR VT     28/0600Z 20.5N  90.5W    30 KT...OVER WATER
 72HR VT     29/0600Z 22.5N  92.5W    35 KT
 96HR VT     30/0600Z 24.0N  94.0W    45 KT
120HR VT     01/0600Z 24.5N  95.5W    60 KT
 
$$
FORECASTER BEVEN
 
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