WTNT44 KNHC 030300 RRA

TCDAT4



TROPICAL STORM HERMINE DISCUSSION NUMBER  23

NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092016

1100 PM EDT FRI SEP 02 2016



RADAR IMAGERY AND SURFACE OBSERVATIONS INDICATE THAT THE

CIRCULATION OF HERMINE HAS BECOME ELONGATED FROM EAST-NORTHEAST TO

WEST-SOUTHWEST OVER THE PAST FEW HOURS.  THIS IS LIKELY IN RESPONSE

TO THE TROPICAL CYCLONE ENCROACHING ON A DEVELOPING FRONTAL

BOUNDARY THAT EXTENDS FROM EASTERN NORTH CAROLINA EASTWARD INTO THE

ATLANTIC.  HOWEVER, BUOY REPORTS FROM THE ATLANTIC SOUTHEAST OF THE

CENTER REMAIN IN THE 40-45 KT RANGE, SO THE INITIAL INTENSITY

REMAINS 45 KT.



DURING THE FORECAST PERIOD, HERMINE IS EXPECTED TO UNDERGO A COMPLEX

INTERACTION WITH A MID- TO UPPER-LEVEL BAROCLINIC TROUGH THAT IS

DEVELOPING OVER THE EASTERN UNITED STATES.  DURING THE FIRST 36-48

HOURS, THE CYCLONE IS LIKELY TO START EXTRATROPICAL TRANSITION AS IT

TRIES TO MERGE WITH THE FRONTAL BOUNDARY.  FROM 48-96 HOURS, THE

DYNAMICAL MODELS FORECAST THE UPPER TROUGH TO CUT OFF DIRECTLY OVER

THE SURFACE CYCLONE, AND AS THIS HAPPENS THEY FORECAST THE SURFACE

CYCLONE TO ACQUIRE A STRUCTURE THAT RESEMBLES A TROPICAL CYCLONE

WITH THE STRONGEST WINDS CLOSE TO THE CENTER.  THIS SUGGESTS THE

POSSIBILITY THAT HERMINE COULD REGAIN SOME TROPICAL CYCLONE

CHARACTERISTICS EVEN THOUGH IT WOULD BE UNDER THE UPPER-LEVEL LOW.

FOR ALL OF THIS COMPLEXITY, THE DYNAMICAL GUIDANCE FORECAST HERMINE

TO STRENGTHEN DURING THIS EVOLUTION REGARDLESS OF ITS FINAL

STRUCTURE, SO THE NEW INTENSITY FORECAST IS AN UPDATE OF THE

PREVIOUS FORECAST.  GIVEN THE UNCERTAINTY IN THE STRUCTURE AND

EVOLUTION, THE FORECAST KEEPS THE CYCLONE AS POST-TROPICAL AFTER 24=