[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 210857
TCDAT2
TROPICAL STORM BERYL DISCUSSION NUMBER  12
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022006
500 AM EDT FRI JUL 21 2006

SATELLITE IMAGERY INDICATES THAT BERYL IS A SHEARED TROPICAL CYCLONE
THIS MORNING...WITH THE REMAINING DEEP CONVECTION CONFINED TO A FEW
BANDS IN THE EASTERN QUADRANT.  AN AIR FORCE RESERVE HURRICANE
HUNTER AIRCRAFT MEASURED 67-KT WINDS AT 850 MB IN THE SOUTHEASTERN
QUADRANT.  HOWEVER...COMPARISON OF THE AIRCRAFT WINDS WITH SURFACE
DATA FROM NANTUCKET AND NEARBY NOAA BUOYS SUGGESTS THAT ONLY 50-60
PERCENT OF THE FLIGHT LEVEL WINDS ARE OCCURRING AT THE SURFACE.
THIS IS LIKELY DUE TO A STABLE BOUNDARY LAYER AND THE OVERALL LACK
OF CONVECTION.  THE INITIAL INTENSITY OF 45 KT IS BASED MAINLY ON A
42-KT DROPSONDE WIND JUST ABOVE THE SURFACE IN THE SOUTHEASTERN
QUADRANT.

THE INITIAL MOTION IS 040/16.  BERYL IS ACCELERATING NORTHEASTWARD
IN DEEP-LAYER SOUTHWESTERLY FLOW AHEAD OF A SHORTWAVE TROUGH MOVING
EASTWARD THROUGH THE EASTERN GREAT LAKES REGION.  THIS MOTION TREND
SHOULD CONTINUE FOR THE REMAINDER OF THE CYCLONE'S LIFE.  THE TRACK
GUIDANCE...PARTICULARLY THE CONSENSUS MODELS...HAS SHIFTED A LITTLE
TO THE LEFT OF THE PREVIOUS TRACK.  THEREFORE... THE NEW FORECAST
TRACK IS SHIFTED A LITTLE TO THE LEFT AS WELL...ABOUT HALFWAY
BETWEEN THE PREVIOUS TRACK AND THE CONSENSUS MODELS.

THE AIRCRAFT DATA SUGGESTS THAT BERYL IS STARTING EXTRATROPICAL
TRANSITION.  THE STORM SHOULD SLOWLY WEAKEN AS IT BECOMES
EXTRATROPICAL DURING THE NEXT 24-36 HR...THEN IT SHOULD GET
ABSORBED BY A FRONTAL SYSTEM OVER THE NORTH ATLANTIC.

FORECAST POSITIONS AND MAX WINDS

INITIAL      21/0900Z 41.7N  69.7W    45 KT
 12HR VT     21/1800Z 43.7N  66.6W    40 KT...BECOMING EXTRATROPICAL
 24HR VT     22/0600Z 46.7N  61.5W    35 KT...EXTRATROPICAL
 36HR VT     22/1800Z 49.5N  55.5W    35 KT...EXTRATROPICAL
 48HR VT     23/0600Z...ABSORBED BY FRONTAL SYSTEM

$$
FORECASTER BEVEN
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