Tropical Storm ALEX

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TROPICAL STORM ALEX DISCUSSION NUMBER  15
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL012010
400 AM CDT TUE JUN 29 2010
 
A 0525Z AIR FORCE RESERVE RECON FLIGHT FOUND TWO PEAK 925 MB
FLIGHT-LEVEL WINDS OF 73 KT LOCATED ABOUT 20 AND 45 NMI NORTHEAST
OF THE CENTER. RELIABLE SFMR SURFACE WINDS ALONG THAT LEG WERE
AROUND 57 KT...AND THE CENTRAL PRESSURE WAS 985 MB. SINCE THAT
RECON FLIGHT...DEEP CONVECTION IN THE EASTERN SEMICIRCLE OF THE
SMALL DEVELOPING EYE HAS ALSO INCREASED. SATELLITE INTENSITY
ESTIMATES AT 06Z WERE T4.0/65 KT FROM TAFB AND T3.5/55 KT FROM SAB.
BASED ON A BLEND OF THESE DATA...THE INITIAL INTENSITY IS SET
AT 60 KT FOR THIS ADVISORY.
 
THE INITIAL MOTION ESTIMATE IS 340/07 BASED ON RECON AND MICROWAVE
SATELLITE FIX POSITIONS OVER THE PAST 8 HOURS. THE LATEST MODEL
GUIDANCE SUITE...INCLUDING THE CONSENSUS MODELS...HAS SHIFTED
SOUTHWARD. HOWEVER...ALEX HAS SHOWN NO SIGNS OF MAKING ANY
SIGNIFICANT WESTWARD PROGRESS LIKE THE ECMWF...NOGAPS...GFS...AND
GFDL MODELS HAVE BEEN AND ARE STILL FORECASTING TO OCCUR. THE
MODELS ARE CONSISTENT...HOWEVER...ON BUILDING A SUBTROPICAL RIDGE
TO THE NORTH AND EAST OF ALEX OVER THE NEXT 3 DAYS...WHICH IS
EXPECTED TO GRADUALLY STEER THE CYCLONE ON A WEST-NORTHWESTWARD OR
WESTWARD TRACK WITH TIME. HOWEVER...WATER VAPOR IMAGERY INDICATES
THE UPPER-LEVEL OUTFLOW PATTERN IS STRONGLY ELONGATED IN A
NORTH-SOUTH ORIENTATION. THIS IS A GOOD SHORT-TERM MOTION INDICATOR
...WHICH WOULD SUGGEST THAT ALEX SHOULD MAINTAIN ITS CURRENT
NORTH-NORTHWESTWARD MOTION FOR ANOTHER 6-12 HOURS BEFORE TURNING
TOWARD THE NORTHWEST. THIS MOTION VECTOR WOULD KEEP ALEX ALONG OR
JUST OUTSIDE THE RIGHT SIDE OF THE GUIDANCE ENVELOPE. SINCE THERE
IS NO OBVIOUS PHYSICAL JUSTIFICATION TO SHIFT THE TRACK SOUTHWARD
AT THIS TIME...THE OFFICIAL FORECAST IS JUST AN UPDATE OF THE
PREVIOUS TRACK AND IS WELL TO THE RIGHT OF THE MODEL CONSENSUS.

MICROWAVE DATA FROM 0114Z SSMIS AND 0243Z AMSU OVERPASSES INDICATED
A SMALL MID-LEVEL EYE FEATURE VERY NEAR THE LOW-LEVEL RECON CENTER
POSITION. THIS INDICATES THAT ALEX HAS A NEARLY VERTICALLY ALIGNED
INNER CORE CIRCULATION...WHICH WOULD FAVOR STEADY INTENSIFICATION
GIVEN THE VERY CONDUCIVE UPPER-LEVEL AND OCEANIC ENVIRONMENTS THAT
THE CYCLONE IS FORECAST TO INTERACT WITH RIGHT UP UNTIL LANDFALL IN
ABOUT 48 HOURS. THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE
PREVIOUS ADVISORY AND IS A BLEND OF THE SHIPS AND LGEM MODELS. 

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      29/0900Z 21.7N  91.9W    60 KT
 12HR VT     29/1800Z 22.8N  92.7W    65 KT
 24HR VT     30/0600Z 24.0N  94.2W    75 KT
 36HR VT     30/1800Z 24.8N  95.9W    80 KT
 48HR VT     01/0600Z 25.3N  97.4W    85 KT...NEAR NE MEXICAN COAST
 72HR VT     02/0600Z 26.0N 100.0W    35 KT...INLAND
 96HR VT     03/0600Z 27.5N 102.5W    20 KT...DISSIPATING INLAND
120HR VT     04/0600Z...DISSIPATED INLAND
 
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FORECASTER STEWART
 
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