000
WTNT41 KNHC 282037
TCDAT1
TROPICAL STORM ALEX DISCUSSION NUMBER  13
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL012010
400 PM CDT MON JUN 28 2010
 
DATA FROM THE AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT SUGGEST
THAT THE INTENSITY OF ALEX HAS CHANGED LITTLE OVER THE PAST FEW
HOURS. THE LAST PRESSURE MEASURED WAS 990 MB...UP JUST A BIT FROM
THIS MORNING. DATA FROM THE SFMR ON THE AIRCRAFT SUPPORT
MAINTAINING THE INTENSITY AT 50 KT. ALEX IS EXPERIENCING NORTHERLY
WIND SHEAR OF ABOUT 10 TO 15 KNOTS ACCORDING TO THE SHIPS MODEL AND
ANALYSES FROM UW-CIMSS. THE SHEAR IN COMBINATION WITH SOME DRY AIR
IN THE NORTHERN PART OF THE CIRCULATION HAVE LIKELY BEEN
RESPONSIBLE FOR THE SPOTTY NATURE OF THE DEEP CONVECTION NEAR THE
CENTER OF ALEX TODAY. ALSO...SINCE ALEX HAS BEEN SITUATED OVER THE
SHALLOW SHELF WATERS WEST OF THE YUCATAN ALL DAY...SOME UPWELLING
OF COOL WATER COULD BE HINDERING DEVELOPMENT FOR THE TIME BEING.
 
ONCE THE MID TO UPPER-LEVEL TROUGH OVER THE NORTHERN GULF OF MEXICO
MOVES AWAY FROM ALEX...THE ENVIRONMENT SHOULD BECOME MORE FAVORABLE
FOR INTENSIFICATION AS THE SHEAR DECREASES AND ALEX MOVES TOWARD A
WARM EDDY IN THE SOUTHWESTERN GULF. THE OFFICIAL NHC INTENSITY
FORECAST IS SIMILAR TO THE PREVIOUS PACKAGE...AND IS CLOSE TO A
BLEND OF THE SHIPS AND LGEM MODELS...WHICH ARE THE STRONGEST OF THE
INTENSITY MODELS. ALSO...ALEX COULD STRENGTHEN A LITTLE MORE BEFORE
LANDFALL BEYOND WHAT IS SHOWN IN THE 48-HOUR FORECAST...BUT NONE OF
THE GUIDANCE SHOWS ALEX REACHING MAJOR HURRICANE INTENSITY AT THIS
TIME.
 
ALEX HAS MOVED LITTLE OVER THE PAST FEW HOURS...BUT THE BEST
LONG-TERM INITIAL MOTION ESTIMATE IS TOWARD THE NORTH-NORTHWEST...
330 DEGREES...AT 4 KNOTS. AFTER THE UPPER-LEVEL TROUGH OVER THE
NORTHERN GULF MOVES EAST...THE GLOBAL MODELS ARE NOW IN GENERALLY
GOOD AGREEMENT IN BUILDING A RIDGE TO THE NORTH OF ALEX. THIS
SHOULD RESULT IN A TURN TOWARD THE NORTHWEST AND THEN TOWARD THE
WEST-NORTHWEST OVER THE NEXT COUPLE OF DAYS...WITH AN INCREASE IN
FORWARD SPEED. COMPARED TO YESTERDAY...THE TRACK GUIDANCE IS IN
BETTER AGREEMENT ON THIS SCENARIO AND HAS GENERALLY TRENDED
SOUTHWARD AND FASTER WITH THE FORWARD SPEED. ACCORDINGLY...THE
OFFICIAL FORECAST HAS BEEN ADJUSTED TO THE LEFT AND SHOWS AN
INCREASE IN FORWARD SPEED...BUT NOW LIES TO THE RIGHT OF MOST OF
THE DYNAMICAL MODELS.
 
A HURRICANE WARNING MAY BE REQUIRED FOR A PORTION OF THE HURRICANE
WATCH AREA TONIGHT.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      28/2100Z 20.5N  91.8W    50 KT
 12HR VT     29/0600Z 21.5N  92.4W    60 KT
 24HR VT     29/1800Z 22.9N  93.7W    65 KT
 36HR VT     30/0600Z 23.8N  95.1W    75 KT
 48HR VT     30/1800Z 24.5N  96.4W    80 KT
 72HR VT     01/1800Z 25.5N  99.5W    60 KT...INLAND
 96HR VT     02/1800Z 26.0N 101.0W    25 KT...INLAND
120HR VT     03/1800Z...DISSIPATED
 
$$
FORECASTER BRENNAN