[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT42 KNHC 050236
TCDAT2

TROPICAL STORM KAREN DISCUSSION NUMBER   8
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122013
1000 PM CDT FRI OCT 04 2013

KAREN HAS BEEN DECAPITATED BY STRONG SOUTHWESTERLY SHEAR AND NOW
CONSISTS OF A VERY TIGHT SWIRL OF LOW CLOUDS WITH SOME LINEAR
CONVECTION TO THE EAST OF THE CENTER. DATA FROM RECONNAISSANCE
PLANES INDICATE THAT THERE IS A WELL-DEFINED CIRCULATION...BUT THE
WINDS ARE GRADUALLY DECREASING. ON THIS BASIS...THE INITIAL
INTENSITY HAS BEEN LOWERED TO 40 KNOTS IN THIS ADVISORY. TROPICAL
STORMS RARELY RECOVER AFTER BEING STRONGLY DAMAGED BY
SHEAR...ESPECIALLY IF THE ENVIRONMENT IS AS DRY AS IT IS OVER THE
WESTERN GULF OF MEXICO. GIVEN THE VIGOROUS CIRCULATION...AND THE
LOW PRESSURE...THE NHC FORECAST KEEPS KAREN WITH 40 KNOTS THROUGH
24 HOURS. AFTER THAT...WHEN THE CYCLONE TURNS TO THE NORTHEAST...
THERE IS A SMALL WINDOW OF OPPORTUNITY FOR KAREN TO STRENGTHEN
SLIGHTLY IF THE SHEAR RELAXES AS INDICATED BY THE SHIPS MODEL. AS
PREVIOUSLY INDICATED...AN ALTERNATIVE SCENARIO IS THAT KAREN
REMAINS DECOUPLED FROM THE DEEP CONVECTION AND WEAKENS AT A FASTER
PACE. THE LATTER SCENARIO IS BECOMING MORE REALISTIC GIVEN THE
CURRENT ORGANIZATION OF THE CYCLONE. FOR NOW...THE NHC FORECAST
OPTED TO FOLLOW THE SLIGHT STRENGTHENING INDICATED BY THE INTENSITY
CONSENSUS. KAREN IS EXPECTED TO BECOME EXTRATROPICAL IN 72 HOURS
AND THEN ABSORBED BY A FRONTAL SYSTEM.

KAREN HESITATED A FEW HOURS AGO...BUT NOW IT HAS BEGUN TO MOVE
TOWARD THE NORTH-NORTHWEST OR 340 DEGREES AT ABOUT 6 KNOTS. KAREN
IS ABOUT TO BE INFLUENCED BY THE FLOW AHEAD OF AN APPROACHING
MID-LEVEL TROUGH AND MOST LIKELY THE CYCLONE WILL MAKE A SHARP TURN
TO THE NORTHEAST ON SATURDAY WITH AN INCREASE IN FORWARD SPEED.
THERE IS CONFIDENCE IN THE TRACK FORECAST SINCE MOST OF THE MODELS
AGREE WITH THIS TURN TO THE NORTHEAST ON SATURDAY.


FORECAST POSITIONS AND MAX WINDS

INIT  05/0300Z 26.4N  90.5W   40 KT  45 MPH
 12H  05/1200Z 27.1N  90.6W   40 KT  45 MPH
 24H  06/0000Z 28.1N  90.0W   40 KT  45 MPH
 36H  06/1200Z 29.0N  88.7W   45 KT  50 MPH
 48H  07/0000Z 30.5N  86.5W   45 KT  50 MPH
 72H  08/0000Z 34.5N  80.5W   25 KT  30 MPH...POST-TROP/EXTRATROP
 96H  09/0000Z...ABSORBED

$$
FORECASTER AVILA



This weather bulletin was brought to you by:
www.nashvilleweather.net