WTPZ45 KNHC 192033 RRA

TCDEP5



TROPICAL STORM DARBY DISCUSSION NUMBER  33

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP052016

200 PM PDT TUE JUL 19 2016



ALTHOUGH DARBY CONTINUES TO EXHIBIT A WELL-DEFINED CIRCULATION, DEEP

CONVECTION, IN THE FORM OF RAGGED BANDS, CONTINUES TO GRADUALLY

DIMINISH IN COVERAGE.  THE INITIAL INTENSITY IS SUBSEQUENTLY LOWERED

TO 55 KT AND REFLECTS THE DVORAK INTENSITY ESTIMATES FROM BOTH TAFB

AND SAB.  THE CYCLONE IS FORECAST TO MOVE OVER MARGINAL SSTS AND

INTO A DRIER, MORE STABLE AIR MASS WITH INCREASING MODEST

SOUTHWESTERLY SHEAR DURING THE NEXT SEVERAL DAYS.  THE OFFICIAL

FORECAST INDICATES SLIGHT WEAKENING DURING THE NEXT DAY OR SO, WITH

VERY LITTLE CHANGE IN STRENGTH THROUGH 96 HOURS AS DARBY TRAVERSES

A SLIGHTLY WARMER OCEAN.  THEREAFTER, DARBY IS EXPECTED TO AGAIN

WEAKEN AS IT GAINS LATITUDE AND MOVES INTO A REGION OF STRONG

SOUTHWESTERLY SHEAR.  THE OFFICIAL FORECAST IS WEIGHED HEAVILY ON

THE IVCN CONSENSUS AND LIES ABOVE THE LGEM AND DECAY SHIPS.  IT

SHOULD BE NOTED THAT LONGER-RANGE, I.E. DAY 4 AND 5, INTENSITY

PREDICTIONS HAVE LITTLE SKILL.



A SERIES OF MICROWAVE IMAGES REVEAL AN APPARENT NORTHWARD

TILT WITH HEIGHT OF THE CYCLONE.  CONSEQUENTLY, THE CONVENTIONAL

SATELLITE POSITION ESTIMATES HAVE BEEN CONSISTENTLY A LITTLE NORTH

OF THE MICROWAVE FIXES.  USING A BLEND OF THESE FIXES, THE INITIAL

MOTION IS ESTIMATED AT 280/11 KT.  THE SYNOPTIC REASONING FOR THE

TRACK FORECAST HAS NOT CHANGED, AS DARBY WILL BE STEERED GENERALLY

WESTWARD DURING THE NEXT 4 DAYS.  THROUGH THE REMAINING PORTION OF

THE FORECAST, THE CYCLONE IS EXPECTED TO DECREASE ITS FORWARD SPEED

AND GRADUALLY BEGIN TO RECURVE NORTHWESTWARD INTO A GROWING WEAKNESS=