000
WTNT41 KNHC 201450
TCDAT1
 
TROPICAL STORM ALBERTO DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL012012
1100 AM EDT SUN MAY 20 2012
 
THE CENTER OF ALBERTO HAS BECOME MORE EXPOSED THIS MORNING...AND THE
DEEPEST CONVECTION APPEARS TO BE MOVING WESTWARD AWAY FROM THE
SYSTEM.  OBJECTIVE AND SUBJECTIVE INTENSITY ESTIMATES ARE ALL
SUGGESTING AN INTENSITY AROUND 35 KT...BUT THE ADVISORY INTENSITY
IS ONLY BEING LOWERED TO 40 KT FOR NOW.  AN AIR FORCE HURRICANE
HUNTER IS SCHEDULED TO INVESTIGATE THE SYSTEM THIS AFTERNOON...AT
WHICH TIME ADDITIONAL ADJUSTMENTS CAN BE MADE.
 
ALBERTO APPEARS TO HAVE AT LEAST THREE STRIKES AGAINST ANY
RE-INTENSIFICATION.  FIRST...DEWPOINTS OVER SOUTHEASTERN U.S. ARE
ROUGHLY 50 DEGREES FAHRENHEIT...AND THE CYCLONE IS LIKELY INGESTING
SOME OF THIS DRY AIR.  SECOND...THE CENTER IS MOVING WEST OF THE
GULF STREAM OVER COOLER SHELF WATERS NEAR THE SOUTH CAROLINA/
GEORGIA COAST.  AND THIRD...UPPER-LEVEL WESTERLY WINDS ARE EXPECTED
TO INCREASE OVER THE SYSTEM DURING THE NEXT 24 HOURS.  THE OFFICIAL
FORECAST THEREFORE KEEPS ALBERTO AT LOW-END TROPICAL-STORM STRENGTH
THROUGH WEDNESDAY WITH WEAKENING AND DISSIPATION OCCURRING ON
THURSDAY.  THIS SCENARIO IS SUPPORTED BY VIRTUALLY ALL OF THE
INTENSITY GUIDANCE.  ALBERTO IS FORECAST TO BECOME POST-TROPICAL BY
72 HOURS...ALTHOUGH THERE IS CONSIDERABLE UNCERTAINTY ON THE EXACT
TIMING OF THAT TRANSITION.
 
A BLOCKING PATTERN OVER THE EASTERN UNITED STATES HAS CAUSED ALBERTO
TO MOVE SLOWLY WEST-SOUTHWESTWARD SINCE YESTERDAY...AND THE CURRENT
MOTION IS 250/5 KT.  THE BLOCKING ANTICYCLONE CURRENTLY POSITIONED
OVER WESTERN NEW ENGLAND IS EXPECTED TO BEGIN SLIDING EASTWARD
TODAY WITH A PROGRESSIVE MID-LATITUDE TROUGH APPROACHING FROM THE
UPPER MIDWEST.  ALBERTO SHOULD CONTINUE TO MOVE LITTLE THROUGH
TONIGHT...BUT THE EVOLVING STEERING PATTERN IS EXPECTED TO
ACCELERATE THE STORM NORTHEASTWARD BEGINNING ON MONDAY.  THERE IS
VERY LITTLE SPREAD IN THE TRACK GUIDANCE THROUGH THE NEXT 48 HOURS.
THEREAFTER...THE ECMWF DIVERGES FROM THE CLUSTER OF OTHER MODELS
AND SHOWS A SLOWER...MORE SOUTHERN SOLUTION.  THE OFFICIAL FORECAST
IS THEREFORE A LITTLE SLOWER AND FARTHER SOUTH THAN THE MULTI-MODEL
CONSENSUS ON DAYS 3 AND 4.
  
FORECAST POSITIONS AND MAX WINDS
 
INIT  20/1500Z 31.5N  79.7W   40 KT  45 MPH
 12H  21/0000Z 31.2N  79.7W   35 KT  40 MPH
 24H  21/1200Z 31.4N  79.1W   35 KT  40 MPH
 36H  22/0000Z 32.3N  77.6W   35 KT  40 MPH
 48H  22/1200Z 34.2N  75.4W   35 KT  40 MPH
 72H  23/1200Z 38.0N  70.5W   35 KT  40 MPH...POST-TROPICAL
 96H  24/1200Z 39.5N  66.5W   30 KT  35 MPH...POST-TROPICAL
120H  25/1200Z...DISSIPATED
 
$$
FORECASTER BERG/PASCH