WTNT42 KNHC 162046 RRA

TCDAT2



TROPICAL STORM KARL DISCUSSION NUMBER  10

NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122016

500 PM AST FRI SEP 16 2016



CONVECTION IS QUITE STRONG IN THE NORTHEASTWARD QUADRANT OF KARL,

ALTHOUGH THE CENTER HAS RECENTLY BECOME EXPOSED DUE TO

MODERATE-TO-STRONG WESTERLY SHEAR.  THERE HAS BEEN LITTLE

CHANGE TO THE OVERALL SATELLITE PRESENTATION IN THE PAST SEVERAL

HOURS, AND THE INITIAL WIND SPEED IS KEPT AT 40 KT.  A CONTINUATION

OF THE SHEAR IS FORECAST TO KEEP KARL FROM STRENGTHENING MUCH OVER

THE NEXT DAY OR TWO. THIS SHEAR IS FORECAST TO RELAX BY ALL OF THE

MODELS BY EARLY NEXT WEEK, AND SOME STRENGTHENING SHOULD THEN TAKE

PLACE WHILE KARL MOVES OVER WARMER WATERS.  THE AMOUNT OF

INTENSIFICATION IS A BIG QUESTION MARK, WITH THE GFS/ECMWF NOW

SHOWING ONLY A WEAKER TROPICAL STORM, WHILE THE REST OF THE STANDARD

INTENSITY GUIDANCE (HWRF, GFDL, SHIPS AND LGEM MODELS) HAVE KARL AS

A HURRICANE BY THE END OF THE PERIOD.  BECAUSE OF THE UNCERTAINTY,

THE INTENSITY FORECAST IS KEPT THE SAME AS THE PREVIOUS ONE, NOT TOO

FAR FROM THE MODEL CONSENSUS.



THE INITIAL MOTION ESTIMATE IS ABOUT THE SAME AS BEFORE, 280/12.

MODEL GUIDANCE HAS MADE A LARGE NORTHWARD SHIFT TODAY DUE TO THE

FORECASTED INTERACTION OF A MID/UPPER-LEVEL TROUGH WITH KARL OVER

THE NEXT FEW DAYS.  INITIALLY, THE TROPICAL CYCLONE WAS EXPECTED TO

BE ON THE WESTERN SIDE OF THE TROUGH, WHICH WOULD HAVE HELPED STEER

THE CYCLONE MORE TO THE WEST-SOUTHWEST OVER THE NEXT COUPLE OF

DAYS.  HOWEVER, ALMOST ALL OF THE GUIDANCE NOW SHOW THE TROUGH

STAYING TO THE WEST OF KARL, WHICH WOULD IMPART A WEST OR

WEST-NORTHWEST MOTION DURING THAT TIME.  THE LACK OF A=