Subtropical Storm LAURA

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SUBTROPICAL STORM LAURA DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL122008
1100 AM EDT MON SEP 29 2008
 
AN 0852 UTC QUIKSCAT PASS OVER LAURA CONFIRMED THAT THE MAXIMUM
WINDS ARE NEAR 50 KT WITHIN A SWATH LOCATED ABOUT 75 NM EAST OF THE
CENTER.  SUBTROPICAL CLASSIFICATIONS OF ST3.0 FROM TAFB AND SAB
ALSO SUPPORT THIS INITIAL INTENSITY.  A PRONOUNCED CONVECTIVE BAND
NOW CURLS ABOUT THREE QUARTERS OF THE WAY AROUND THE EAST AND NORTH
OF THE LARGE CIRCULATION BUT THE LOW-LEVEL CENTER REMAINS BROAD AND
ILL-DEFINED WITH SEVERAL INTERNAL SMALLER SWIRLS.  WITH THE
IMPROVED CONVECTIVE SIGNATURE...A CASE COULD BE MADE THAT THE
CYCLONE IS BEGINNING TO ACQUIRE MORE TROPICAL CHARACTERISTICS.

LAURA IS BEGINNING TO MAKE A MORE PRONOUNCED POLEWARD TURN AS IT
MOVES BETWEEN HIGH PRESSURE NORTH OF THE AZORES AND THE
EXTRATROPICAL REMNANTS OF HURRICANE KYLE OVER THE CANADIAN
MARITIMES.  A NORTHWESTWARD TO NORTHWARD MOTION WILL CONTINUE FOR
THE NEXT 36 HOURS OR SO BUT THE LATEST TRACK GUIDANCE HAS SHIFTED
TO THE RIGHT OF THE PREVIOUS OFFICIAL FORECAST.  THE NEW FORECAST
DOES NOT GO AS FAR TO THE RIGHT AS THE MODEL CONSENSUS AND INSTEAD
LIES ON THE LEFT SIDE OF THE GUIDANCE...CLOSE TO THE GFS AND
GFDL.  LAURA WILL LIKELY BE PICKED UP BY THE MID-LATITUDE TROUGH
CURRENTLY OVER THE CANADIAN MARITIMES BY DAY 3 AND THEN ACCELERATE
EASTWARD WITHIN THE MID-LATITUDE FLOW...POSSIBLY APPROACHING THE
BRITISH ISLES AS A POWERFUL EXTRATROPICAL LOW.

OCEAN WATERS ARE MARGINALLY WARM NEAR LAURA...BUT APPEAR TO BE JUST
WARM ENOUGH TO SUPPORT INCREASED CONVECTION.  IF THE CONVECTION CAN
WRAP CLOSER TO THE CENTER...THERE IS A CHANCE THAT THE CYCLONE
COULD BECOME A TROPICAL CYCLONE BEFORE TRANSITIONING INTO AN
EXTRATROPICAL LOW.  THEREFORE...SOME STRENGTHENING IS INDICATED
OVER THE NEXT 24 HOURS JUST BEFORE LAURA MOVES OVER INCREASINGLY
LOWER SEA SURFACE TEMPERATURES.  MOST OF THE DYNAMICAL GUIDANCE IS
RATHER UNIMPRESSED WITH THE POTENTIAL FOR INTENSIFICATION WHEREAS
THE SHIPS MODEL SHOWS LAURA STRENGTHENING TO 80 KT BY DAY 4 OR
5...PRIMARILY DUE TO A STRONG CONTRIBUTION FROM COLD UPPER LEVEL
TEMPERATURES.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      29/1500Z 37.4N  47.8W    50 KT
 12HR VT     30/0000Z 38.1N  48.3W    55 KT
 24HR VT     30/1200Z 39.8N  48.3W    60 KT
 36HR VT     01/0000Z 41.8N  47.7W    60 KT
 48HR VT     01/1200Z 44.4N  46.6W    55 KT...EXTRATROPICAL
 72HR VT     02/1200Z 51.5N  41.5W    50 KT...EXTRATROPICAL
 96HR VT     03/1200Z 55.5N  30.5W    45 KT...EXTRATROPICAL
120HR VT     04/1200Z 55.0N  15.0W    45 KT...EXTRATROPICAL
 
$$
FORECASTER BERG/PASCH
 
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