WTPZ41 KNHC 152034 RRA

TCDEP1



HURRICANE FERNANDA DISCUSSION NUMBER  16

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP062017

200 PM PDT SAT JUL 15 2017



A RECENT AMSU PASS INDICATES THAT FERNANDA CONTINUES TO HAVE A

DOUBLE EYEWALL STRUCTURE, WITH THE INNER EYE ABOUT 20 N MI IN

DIAMETER AND THE OUTER EYE ABOUT 60 N MI ACROSS.  THE APPEARANCE OF

FERNANDA IN GEOSTATIONARY SATELLITE IMAGES REMAINS IMPRESSIVE WITH A

SMALL DISTINCT EYE SURROUNDING BY A RING OF COLD CLOUD TOPS.

THE COLD CLOUD TOPS, HOWEVER, ARE NOT QUITE AS EXPANSIVE AS THEY

WERE EARLIER.  ACCORDINGLY, THE LATEST SATELLITE INTENSITY ESTIMATES

HAVE DECREASED SLIGHTLY AND RANGE FROM 105 TO 125 KT, AND BASED ON

THESE DATA, THE INITIAL WIND SPEED IS LOWERED A LITTLE TO 115 KT.

IT SHOULD BE NOTED THAT IT IS COMMON FOR HURRICANES THAT UNDERGO

EYEWALL REPLACEMENT CYCLES (ERC) TO WEAKEN DURING THE BEGINNING OF

THE PROCESS.



ASSUMING THE ERC COMPLETES, FERNANDA HAS AN OPPORTUNITY TO

RESTRENGTHEN DURING THE NEXT DAY OR SO WHILE IT REMAINS IN

FAVORABLE ATMOSPHERIC CONDITIONS AND OVER WARM WATER.  AFTER THAT

TIME, STEADY, OR EVEN RAPID, WEAKENING IS EXPECTED AS THE HURRICANE

MOVES OVER COOLER WATER AND INTO A DRIER AND MORE STABLE AIR MASS.

AN INCREASE IN SOUTHWESTERLY SHEAR SHOULD AID IN THE WEAKENING

PROCESS TOWARD THE END OF THE FORECAST PERIOD. THE NHC INTENSITY

FORECAST IS AT THE HIGH END, OR SLIGHTLY ABOVE, THE GUIDANCE IN THE

SHORT TERM, BUT THEN FALLS IN LINE WITH THE INTENSITY MODEL

CONSENSUS AFTER THAT.  THIS FORECAST IS A TAD LOWER THAN THE

PREVIOUS ONE.



A MID-LEVEL RIDGE LOCATED OVER THE WESTERN UNITED STATES IS STEERING

FERNANDA WESTWARD, OR 280 DEGREES, AT 11 KT. A WEST-NORTHWESTWARD