WTPA41 PHFO 211452 RRA

TCDCP1



TROPICAL STORM FERNANDA DISCUSSION NUMBER  39

NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP062017

500 AM HST FRI JUL 21 2017



DEEP CONVECTION PERSISTED TO THE NORTHEAST OF FERNANDA OVERNIGHT,

BUT SEPARATED FURTHER FROM THE LOW LEVEL CIRCULATION CENTER (LLCC)

DUE TO INCREASING SOUTHWESTERLY SHEAR. THE LATEST SUBJECTIVE DVORAK

INTENSITY ESTIMATES FROM PHFO AND SAB CAME IN AT 35 AND 25 KNOTS

RESPECTIVELY, WITH THE ADVANCED DVORAK TECHNIQUE (ADT) FROM

UW-CIMSS COMING IN WITH 33 KNOTS. THESE VALUES ARE LIKELY STILL A

BIT TOO LOW GIVEN THE SLOW SPIN DOWN TIME OF THESE SYSTEMS. GIVEN

THE INCREASING SHEAR AND RESULTANT SEPARATION OF THE DEEP CONVECTION

FROM THE LLCC HOWEVER, THE INITIAL INTENSITY HAS BEEN LOWERED TO 40

KNOTS FOR THIS ADVISORY PACKAGE.



THE INITIAL MOTION FOR THIS ADVISORY IS 280/10 KT. THE SPREAD

BETWEEN THE RELIABLE GUIDANCE REMAINS LARGE. THE GFS CONTINUES TO

SHOW A STRONGER AND DEEPER SYSTEM TRACKING OFF TOWARD THE NORTHWEST

FOR THE NEXT SEVERAL DAYS AROUND THE SOUTHWESTERN PERIPHERY OF A

STRONG SUB-TROPICAL RIDGE. THE ECMWF AND TO A LESSER EXTENT THE

HWRF AND FSSE OBJECTIVE AIDS, SHOW A MORE SHALLOW SYSTEM STEERED

ALONG PRIMARILY BY THE LOW LEVEL TRADE WIND FLOW. THE GFEX AND TVCN

CONSENSUS GUIDANCE APPEAR TO BE INFLUENCED TOO FAR TO THE NORTH DUE

TO THE OUTLIER GFS SOLUTION. GIVEN THE UNFAVORABLE ENVIRONMENTAL

CONDITIONS, THE FORECAST TRACK IS VERY CLOSE TO THE PREVIOUS

OFFICIAL FORECAST, CLOSELY IN LINE WITH THE ECMWF SOLUTION, AND TO

THE SOUTH OF THE CONSENSUS GUIDANCE. AS A RESULT, THE FORECAST TRACK

TAKES FERNANDA OFF TO THE WEST-NORTHWEST THROUGH THE FORECAST