955  
WTNT42 KNHC 251434  
TCDAT2  
 
POST-TROPICAL CYCLONE KARL DISCUSSION NUMBER 45  
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122016  
1100 AM AST SUN SEP 25 2016  
 
WHILE KARL WAS PRODUCING A LARGE SHIELD OF DEEP CONVECTION EARLIER,  
THE CONVECTIVE TOPS HAVE SINCE WARMED SUBSTANTIALLY AND DECREASED IN  
COVERAGE. THE CYCLONE'S CLOUD PATTERN RESEMBLES A BAROCLINIC LEAF,  
WHICH IS THE TYPICAL SATELLITE SIGNATURE OF A SYSTEM THAT HAS BECOME  
A FRONTAL WAVE. THE LEADING EDGE OF A STRATOCUMULUS CLOUD DECK,  
INDICATIVE OF COLD-AIR ADVECTION, IS ALSO ENCROACHING ON THE  
LOW-LEVEL CENTER. BASED ON THESE DEVELOPMENTS AND FSU PHASE SPACE  
DIAGRAMS THAT ALREADY SHOW THE CYCLONE AS COLD CORE, KARL IS BEING  
DECLARED AN EXTRATROPICAL CYCLONE. THE INITIAL INTENSITY ESTIMATE IS  
HELD AT 60 KT IN AGREEMENT WITH EARLIER GLOBAL HAWK SONDE DATA AND  
THE CYCLONE'S RAPID TRANSLATIONAL SPEED. GLOBAL MODELS SHOW POST-  
TROPICAL KARL BEING ABSORBED BY A LARGER EXTRATROPICAL STORM OVER  
THE NORTH ATLANTIC AFTER ABOUT 24 HOURS.  
 
A SERIES OF EARLIER MICROWAVE IMAGES SHOWED THAT THE CENTER WAS  
RAPIDLY BECOMING DEFORMED DUE TO NEARLY 50 KT OF SOUTHWESTERLY  
SHEAR. SINCE THIS HAS MADE FINDING THE LOCATION OF THE LOW-LEVEL  
CENTER DIFFICULT, THE INITIAL MOTION ESTIMATE IS A RATHER UNCERTAIN  
055/42. THE POST-TROPICAL CYCLONE IS EXPECTED TO ACCELERATE A BIT  
FURTHER TOWARD THE NORTHEAST AND THEN TURN NORTH-NORTHEAST BEFORE  
LOSING ITS IDENTITY.  
 
FORECAST POSITIONS AND MAX WINDS  
 
INIT 25/1500Z 39.9N 47.9W 60 KT 70 MPH...POST-TROP/EXTRATROP  
12H 26/0000Z 45.0N 39.7W 55 KT 65 MPH...POST-TROP/EXTRATROP  
24H 26/1200Z 52.5N 31.5W 50 KT 60 MPH...POST-TROP/EXTRATROP  
36H 27/0000Z...ABSORBED  
 

 
FORECASTER KIMBERLAIN  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab TPC Page Main Text Page