WTPZ41 KNHC 162033 RRA

TCDEP1



HURRICANE FERNANDA DISCUSSION NUMBER  20

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP062017

200 PM PDT SUN JUL 16 2017



SATELLITE IMAGES INDICATE THAT THE EYE OF FERNANDA, WHICH IS ABOUT

10 N MI IN DIAMETER, IS NOT QUITE AS DISTINCT AS IT WAS EARLIER

TODAY.  THE DEEP CONVECTION SURROUNDING THE EYE IS ALSO A LITTLE

LESS SYMMETRIC WITH A FEW DRY SLOTS NOTED IN INFRARED PICTURES.  THE

INITIAL WIND SPEED IS LOWERED SLIGHTLY TO 110 KT, BASED ON AN

AVERAGE OF DVORAK T- AND CI-NUMBERS FROM TAFB, SAB, AND ADT VALUES

FROM CIMSS AT THE UNIVERSITY OF WISCONSIN.  THE HURRICANE IS STILL

OVER WARM WATER AND IN A FAVORABLE ATMOSPHERIC ENVIRONMENT, AND IT

IS FORECAST TO REMAIN IN THOSE CONDITIONS FOR ANOTHER DAY OR SO.

THEREFORE, LITTLE CHANGE IN STRENGTH IS EXPECTED IN THE SHORT TERM.

AFTER THAT TIME, HOWEVER, COOLER WATERS, DRIER AIR, AND AN INCREASE

IN WIND SHEAR SHOULD CAUSE FERNANDA TO STEADILY WEAKEN.  THE NHC

INTENSITY FORECAST IS AN UPDATE OF THE PREVIOUS ONE, AND IS IN

GENERAL AGREEMENT WITH THE CONSENSUS MODELS.



FERNANDA CONTINUES TO MOVE WEST-NORTHWESTWARD AT 10 KT NEAR THE

SOUTHWESTERN PERIPHERY OF A MID-LEVEL HIGH PRESSURE SYSTEM

CENTERED OVER THE SOUTHWESTERN UNITED STATES.  THE TRACK FORECAST

PHILOSOPHY REMAINS UNCHANGED FROM THE PAST SEVERAL ADVISORIES.  A

TROUGH TO THE NORTHEAST OF THE HAWAIIAN ISLANDS IS EXPECTED TO ERODE

THE WESTERN PORTION OF THE RIDGE DURING THE NEXT FEW DAYS.  THIS

PATTERN CHANGE SHOULD CAUSE FERNANDA TO SLOW DOWN AND GAIN MORE

LATITUDE THAN IT HAS IN PREVIOUS DAYS.  THE TROUGH IS EXPECTED

TO LIFT OUT LATER IN THE WEEK ALLOWING THE RIDGE TO REBUILD TO THE