WTNT42 KNHC 190238 RRA

TCDAT2



TROPICAL STORM KARL DISCUSSION NUMBER  19

NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122016

1100 PM AST SUN SEP 18 2016



KARL IS A POORLY ORGANIZED TROPICAL STORM.  SATELLITE DATA INDICATE

THAT THE LOW-LEVEL CENTER IS EXPOSED TO THE SOUTHWEST OF A FEW

PATCHES OF DEEP CONVECTION.  THE INITIAL INTENSITY IS AGAIN HELD AT

35 KT, IN AGREEMENT WITH THE EARLIER SCATTEROMETER DATA AND A DVORAK

CLASSIFICATION FROM TAFB.  THE CYCLONE CONTINUES TO STRUGGLE IN AN

ENVIRONMENT OF SOUTHWESTERLY SHEAR AND DRY AIR.  IN FACT, TOTAL

PRECIPITABLE WATER IMAGERY SHOWS DRY AIR WRAPPING AROUND THE WEST

AND SOUTH SIDES OF THE CIRCULATION.  THE MODELS INDICATE THAT THE

SHEAR SHOULD LOWER ON MONDAY, AND REMAIN RELATIVELY LIGHT DURING THE

NEXT SEVERAL DAYS.  SINCE KARL IS EXPECTED TO TRACK OVER

PROGRESSIVELY WARMER WATERS, BETWEEN 28-30 DEG C, AND MOVE INTO A

MORE CONDUCIVE ATMOSPHERIC ENVIRONMENT, STRENGTHENING SEEMS LIKELY.

THE NHC INTENSITY FORECAST IS LARGELY AN UPDATE OF THE PREVIOUS ONE,

BUT IT IS A TOUCH LOWER AT THE 12-H POINT GIVEN THE CURRENT POOR

INITIAL STRUCTURE OF KARL. THIS FORECAST IS IN BEST AGREEMENT WITH

THE SHIPS MODEL.



THE SYSTEM IS MOVING WESTWARD AT 13 KT, AND THAT GENERAL MOTION

SHOULD CONTINUE FOR THE NEXT 12-24 HOURS AS KARL REMAINS ON THE

SOUTH SIDE OF A SUBTROPICAL RIDGE OVER THE CENTRAL ATLANTIC.  A

WEST-NORTHWESTWARD MOTION IS EXPECTED TO BEGIN BY MONDAY NIGHT,

FOLLOWED BY A TURN TO THE NORTHWEST BY MID-WEEK WHEN THE CYCLONE

MOVES TOWARD A WEAKNESS IN THE RIDGE.  ALTHOUGH THE MODELS

AGREE ON THE OVERALL SCENARIO, THERE IS A FAIR AMOUNT OF SPREAD BY

THE END OF THE FORECAST PERIOD.  THE NHC TRACK FORECAST IS SLIGHTLY=