000
WTNT41 KNHC 192042
TCDAT1

TROPICAL STORM ALBERTO DISCUSSION NUMBER   1
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL012012
500 PM EDT SAT MAY 19 2012

SATELLITE...RADAR...AND SURFACE DATA INDICATE THAT THE SMALL SURFACE
LOW LOCATED OFF THE COAST OF SOUTH CAROLINA HAS ACQUIRED THE
CHARACTERISTICS OF A TROPICAL CYCLONE.  ORGANIZED DEEP CONVECTION
HAS BEEN PERSISTENT OVER THE CENTER FOR MORE THAN 18 HOURS...AND
THE CIRCULATION CENTER HAS BEEN MOVING SOUTH AWAY FROM AN AIRMASS
BOUNDARY THAT EXTENDS ROUGHLY ALONG 33N.  BASED ON AN ASCAT PASS
FROM AROUND 1530 UTC...THE INITIAL INTENSITY IS SET AT 40 KT.
ALBERTO IS SITUATED IN A MARGINAL THERMODYNAMIC ENVIRONMENT FOR
STRENGTHENING...WITH A MARKEDLY DRY CONTINENTAL AIRMASS TO ITS NORTH
AND WEST OVER THE EASTERN CAROLINAS.  GIVEN THIS...ONLY MODEST
INTENSIFICATION IS EXPECTED DESPITE THE CYCLONE BEING OVER
THE RELATIVELY WARM GULF STREAM.  ALBERTO IS EXPECTED TO BECOME
EXTRATROPICAL BY 96 HOURS...AND SHOULD DISSIPATE BY DAY 5.  THE NHC
INTENSITY FORECAST IS A BLEND OF THE MORE AGGRESSIVE STATISTICAL
GUIDANCE AND THE WEAKER DYNAMICAL MODELS.

THE LOW-LEVEL CIRCULATION IS A BIT TO THE EAST OF THE COLDEST CLOUD
TOPS AND THE CIRCULATION CENTER SEEN ON RADAR...AND THE INITIAL
MOTION ESTIMATE IS 220/03. THE SYNOPTIC ENVIRONMENT IS COMPLEX...AS
ALBERTO IS IN A REGION OF WEAK STEERING FLOW WITHIN A BROAD
MID/UPPER-LEVEL TROUGH. THE NHC FORECAST SHOWS A SLOW SOUTHWESTWARD
MOTION OVER THE NEXT DAY OR SO DUE TO THE STRONG NORTHEASTERLY FLOW
BETWEEN A SURFACE RIDGE EAST OF THE APPALACHIANS AND A LARGER
EXTRATROPICAL LOW CENTERED NEAR 36N/72W. AS THAT LOW MOVES WESTWARD
AND WEAKENS BY SUNDAY NIGHT...ALBERTO IS EXPECTED TO TURN NORTHWARD
AND THEN ACCELERATE NORTHEASTWARD AFTER 48 HOURS AS A SHORTWAVE
TROUGH MOVES INTO THE EASTERN UNITED STATES AND THE STEERING FLOW
BECOMES SOUTHWESTERLY. GIVEN THE SMALL SIZE OF ALBERTO AND THE
COMPLEX STEERING PATTERN...IT IS NOT SURPRISING THAT THE TRACK
MODEL GUIDANCE SHOWS A LARGE AMOUNT OF SPREAD...BOTH IN TERMS OF
HOW FAR SOUTH AND WEST ALBERTO WILL MOVE...AND HOW SHARP THE TURN
TOWARD THE NORTHEAST WILL BE. THE NHC TRACK FORECAST IS GENERALLY
CLOSE TO THE TVCA MULTI-MODEL CONSENSUS...AND IS OF VERY LOW
CONFIDENCE.

A TROPICAL STORM WATCH COULD BE REQUIRED FOR A PORTION OF THE COAST
OF THE CAROLINAS THIS EVENING.

ALBERTO IS EARLIEST-FORMING TROPICAL STORM IN THE ATLANTIC BASIN
SINCE ANA IN 2003.  THIS IS ALSO THE FIRST TIME THAT A TROPICAL
STORM HAS FORMED BEFORE THE OFFICIAL START OF THE HURRICANE SEASON
IN BOTH THE ATLANTIC AND EAST PACIFIC BASINS.


FORECAST POSITIONS AND MAX WINDS

INIT  19/2100Z 32.2N  77.7W   40 KT  45 MPH
 12H  20/0600Z 31.9N  78.1W   45 KT  50 MPH
 24H  20/1800Z 31.7N  78.5W   45 KT  50 MPH
 36H  21/0600Z 31.9N  78.9W   45 KT  50 MPH
 48H  21/1800Z 32.7N  78.5W   45 KT  50 MPH
 72H  22/1800Z 34.5N  75.5W   45 KT  50 MPH
 96H  23/1800Z 37.5N  72.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
120H  24/1800Z...DISSIPATED

$$
FORECASTER BRENNAN