WTPZ41 KNHC 191440 RRA

TCDEP1



HURRICANE FERNANDA DISCUSSION NUMBER  31

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP062017

800 AM PDT WED JUL 19 2017



WHILE THERE ARE STILL OCCASIONAL GLIMPSES OF THE EYE IN INFRARED

IMAGERY, THE CONVECTIVE CLOUD PATTERN OF FERNANDA CONTINUES TO

SLOWLY DECAY. THE INITIAL INTENSITY IS THUS REDUCED A LITTLE MORE,

TO 75 KT, BASED ON A BLEND OF VARIOUS SATELLITE INTENSITY

ESTIMATES.  WATER VAPOR IMAGERY SHOWS THAT THE OUTFLOW IS BECOMING

RESTRICTED IN THE SOUTHWESTERN QUADRANT, WHICH IS A REFLECTION OF

10-15 KT OF SOUTHWESTERLY VERTICAL SHEAR AFFECTING THE CYCLONE.



THE INITIAL MOTION IS 310/7.  FERNANDA IS EXPECTED TO TURN

WEST-NORTHWEST LATER TODAY AND CONTINUE THIS MOTION THROUGH 72 H AS

IT IS STEERED BY A STRONG LOW- TO MID-LEVEL RIDGE TO THE NORTH.

THIS RIDGE IS FORECAST TO PERSIST AFTER 72 H.  HOWEVER, THE

GUIDANCE BECOMES MORE DIVERGENT DURING THAT TIME, LIKELY DUE TO HOW

QUICKLY THE VARIOUS LARGE-SCALE MODELS WEAKEN FERNANDA.  THE NAVGEM

AND CANADIAN MODELS, WHICH WEAKEN THE CYCLONE QUICKLY, SHOW A

GENERALLY WESTWARD MOTION OF THE REMNANTS.  THE GFS AND THE HWRF,

WHICH MAINTAIN A STRONGER VORTEX, SHOW A MORE NORTHERLY MOTION ON

THE RIGHT SIDE OF THE GUIDANCE ENVELOPE.  THE ECMWF IS BETWEEN THESE

EXTREMES, AND THIS PART OF NEW TRACK FORECAST IS A LITTLE TO THE

NORTH OF THE ECMWF AND A LITTLE SOUTH OF THE MODEL CONSENSUS.

OVERALL, THE NEW FORECAST IS LITTLE CHANGED THROUGH 72 H, THEN

NUDGED NORTH OF THE PREVIOUS FORECAST THEREAFTER.



FERNANDA IS EXPECTED TO STEADILY WEAKEN THROUGH THE FORECAST PERIOD

DUE TO VARIOUS COMBINATIONS OF COOL SEA SURFACE TEMPERATURES,

SOUTHWESTERLY TO SOUTHERLY SHEAR, AND DRY AIR ENTRAINMENT.  THUS,