WTPZ44 KNHC 261435 RRA

TCDEP4



HURRICANE HILARY DISCUSSION NUMBER  21

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP092017

900 AM MDT WED JUL 26 2017



SATELLITE IMAGES INDICATE THAT HILARY REMAINS A POWERFUL HURRICANE.

THE CENTRAL DENSE OVERCAST HAS BECOME MORE SYMMETRIC, ALTHOUGH

CONVECTION IS STILL PREFERENTIALLY FORMING IN THE EASTERN EYEWALL.

ANY EYE FEATURE, HOWEVER, IS SOMEWHAT LESS DISTINCT THAN A FEW HOURS

AGO, AND THE LATEST MICROWAVE PASSES ARE AGAIN SHOWING AN OPEN

EYEWALL ON THE WEST SIDE. INTENSITY ESTIMATES RANGE FROM 82 TO 99

KT, SO THE INITIAL WIND SPEED WILL STAY AT 90 KT.



THERE ARE STILL HINTS OF NORTHERLY SHEAR IN CIRRUS CLOUD MOTIONS

FROM THE 1-MIN GOES-16 DATA, ALTHOUGH THE CYCLONE'S CLOUD CANOPY

LOOKS LESS DISTORTED THAN YESTERDAY.  THIS SHEAR IS FORECAST TO

PERSIST FOR THE NEXT DAY OR TWO WHILE THE HURRICANE MOVES OVER

WARM WATERS.  AFTER THAT TIME, WHILE THE SHEAR COULD DECREASE,

HILARY WILL BE TRAVERSING MARGINALLY WARM WATERS, WITH SOME INCREASE

IN DRIER, MORE STABLE AIR IN THE ENVIRONMENT.  MOST OF THE GUIDANCE

IS IN GOOD AGREEMENT ON LITTLE CHANGE IN THE SHORT-TERM, WITH A

GRADUAL DECREASE IN WIND SPEED THROUGH 3 DAYS.  BEYOND THEN, MUCH

COLDER WATERS SHOULD CAUSE A MORE RAPID WEAKENING, ALONG WITH SOME

INTERACTION WITH IRWIN. THE NEW NHC FORECAST IS BASICALLY AN UPDATE

OF THE PREVIOUS ONE AND LIES CLOSE TO IVCN, THE VARIABLE INTENSITY

MODEL CONSENSUS. IT SHOULD BE NOTED THAT THE ECMWF IS ON ITS OWN BY

INTENSIFYING HILARY TO A MAJOR HURRICANE IN 2 TO 3 DAYS.



THE INITIAL MOTION IS 280/11.  THE TRACK FORECAST IS ESSENTIALLY

UNCHANGED FOR THE NEXT 48 H, WHILE HILARY IS EXPECTED TO BE STEERED