WTNT42 KNHC 181454 RRA

TCDAT2



TROPICAL STORM KARL DISCUSSION NUMBER  17

NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122016

1100 AM AST SUN SEP 18 2016



THE OVERALL APPEARANCE OF KARL HAS CHANGED LITTLE IN SATELLITE

IMAGERY SINCE THE PREVIOUS ADVISORY.  HOWEVER, RECENT WATER VAPOR

IMAGERY SUGGEST THAT THE STRONG SOUTHWESTERLY SHEAR THAT HAS BEEN

PLAGUING THE CYCLONE FOR THE PAST FEW DAYS IS BEGINNING TO RELAX.

THE INITIAL WIND SPEED IS HELD AT 35 KT BASED ON A TAFB SATELLITE

ESTIMATE OF T2.5/35 KT.  SHIP BATFR18, WHICH HAS BEEN SKIRTING THE

EASTERN PORTION OF KARL'S CIRCULATION THE PAST 12 HOURS, HAS

REPORTED WINDS AS HIGH AS 32 KT.  THAT DATA HAS BEEN HELPFUL IN

DETERMINING THE EXTENT OF THE 34-KT WIND RADIUS IN THE NORTHEASTERN

QUADRANT.



KARL HAS TRENDED WESTWARD AND THE INITIAL MOTION ESTIMATE IS NOW

270/11 KT.  A DEEP-LAYER SUBTROPICAL RIDGE OVER THE CENTRAL ATLANTIC

TO THE NORTH OF KARL IS EXPECTED TO KEEP THE CYCLONE MOVING IN A

GENERAL WESTWARD DIRECTION FOR THE NEXT 48 HOURS OR SO, FOLLOWED BY

WEST-NORTHWESTWARD MOTION DURING THE REMAINDER OF THE FORECAST

PERIOD.  THE NEW NHC TRACK FORECAST IS SIMILAR TO THE PREVIOUS

ADVISORY, AND LIES CLOSE TO THE VARIOUS CONSENSUS MODEL SOLUTIONS.



ALTHOUGH KARL'S CONVECTIVE PATTERN IS CURRENTLY SOMEWHAT DISHEVELED

DUE TO THE HOSTILE SHEAR AND DRY MID-LEVEL CONDITIONS THAT THE

CYCLONE HAS BEEN ENCOUNTERING THE PAST SEVERAL DAYS, THE SURFACE

WIND FIELD HAS REMAINED REMARKABLY ROBUST, INCLUDING A TIGHT

INNER-CORE.  THE GFS AND ECMWF MODELS ARE FORECASTING THE VERTICAL

WIND SHEAR TO DECREASE TO LESS THAN 5 KT FROM 24-120 HOURS, WHICH

FAVORS A STRENGTHENING TREND, ESPECIALLY SINCE KARL WILL BE MOVING=