WTPA41 PHFO 210240 RRA

TCDCP1



TROPICAL STORM FERNANDA DISCUSSION NUMBER  37

NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP062017

500 PM HST THU JUL 20 2017



MOST OF THE DEEP CONVECTION NEAR THE CENTER OF FERNANDA HAS

DISSIPATED LEAVING AN EXPOSED LOW LEVEL CIRCULATION CENTER

SURROUNDED BY MOSTLY LOW- AND MID-LEVEL CLOUDS. THE REMAINING

THUNDERSTORMS ARE CONFINED TO AN OUTER RAINBAND MORE THAN 60 NM

NORTH OF THE CENTER. THE INITIAL INTENSITY IS 45 KT WHICH IS

SLIGHTLY WEAKER THAN THE PREVIOUS ADVISORY. THIS MAY BE CONSERVATIVE

BUT AN ASCAT PASS FROM 1936 UTC SAMPLED THE NORTHWESTERN PORTION OF

THE CIRCULATION AND FOUND 40 KT. SUBJECTIVE DVORAK ESTIMATES FROM

PHFO AND SAB CAME IN AT 35 KT BUT THIS MAY BE TOO AGGRESSIVE A DROP

AT THIS TIME.



THE INITIAL MOTION FOR THIS PACKAGE IS 280/10 KT WITH STEERING

INCREASINGLY DICTATED BY THE LOW LEVEL FLOW. THE MAIN DYNAMICAL

AIDS SHOW A FAIR AMOUNT OF SPREAD. THE GFS, AND TO A LESSER

DEGREE HWRF, CONTINUE TO HOLD ON TO A STRONGER AND DEEPER SYSTEM

WHICH RESULTS IN A MORE NORTHWESTWARD TRACK. THIS DOESN'T APPEAR

TO BE REASONABLE GIVEN THE ENVIRONMENTAL CIRCUMSTANCES. THUS, THE

FORECAST TRACK LEANS MORE TOWARD THE ECMWF SOLUTION AND IS CLOSE TO

THE PREVIOUS FORECAST, KEEPING FERNANDA ON A GENERAL WESTWARD TO

WEST-NORTHWESTWARD MOTION THROUGH THE FORECAST PERIOD.



FERNANDA IS TRACKING OVER WATERS NEAR 25C. ALONG THE FORECAST TRACK,

SEA SURFACE TEMPERATURE ARE TO REMAIN IN THE 25C TO 26C RANGE. THE

CYCLONE IS ALSO EXPECTED TO STAY WITHIN STRONG VERTICAL SHEAR

CONDITIONS OF ABOUT 25 TO 35 KT THROUGH THE NEXT 3 DAYS.

ALTHOUGH SOME DEEP CONVECTION MAY OCCASIONALLY FLARE UP NEAR