WTPZ41 KNHC 130844 RRA

TCDEP1



TROPICAL STORM FERNANDA DISCUSSION NUMBER   6

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP062017

300 AM MDT THU JUL 13 2017



FIXES OFF OF RECENT ASCAT DATA INDICATE THAT FERNANDA'S CENTER IS

NOW FULLY EMBEDDED BENEATH THE CONVECTIVE CANOPY, AND CLOUD TOPS

ARE AS COLD AS -85 DEG C.  THE IMPROVED STRUCTURE IS TRANSLATING

INTO STRONGER SURFACE WINDS, WITH THE ASCAT PASSES SHOWING THAT THE

INITIAL INTENSITY IS NOW 45 KT.



THE ASCAT DATA SHOWED THAT FERNANDA'S CENTER IS MOVING SOUTH OF DUE

WEST, AND THE MOTION ESTIMATE IS 265/9 KT.  DEEP-LAYER RIDGING TO

THE NORTH OF THE CYCLONE IS EXPECTED TO STRENGTHEN AND BUILD

WESTWARD, WHICH SHOULD KEEP FERNANDA ON A WEST TO SOUTH-OF-DUE-WEST

TRAJECTORY FOR THE NEXT 3 DAYS.  THE RIDGE THEN NARROWS AND WEAKENS

A BIT ON DAYS 4 AND 5, WHICH SHOULD ALLOW FERNANDA TO GRADUALLY GAIN

SOME LATITUDE BY THE END OF THE FORECAST PERIOD.  THE RECENT TREND

OF THE TRACK GUIDANCE SHIFTING SOUTH HAS CONTINUED, AND THE UPDATED

NHC TRACK FORECAST HAS THEREFORE BEEN SHIFTED SOUTH OF THE PREVIOUS

FORECAST DURING THE FIRST 48 HOURS.  AFTER THAT TIME, THE MODELS ARE

THEN SUGGESTING THAT FERNANDA'S TRACK MAY TAKE A MORE PRONOUNCED

POLEWARD BEND, AND THE NEW NHC FORECAST IS THEREFORE A LITTLE

NORTHEAST OF THE PREVIOUS FORECAST ON DAYS 4 AND 5.



NORTHEASTERLY SHEAR AFFECTING FERNANDA HAS WEAKENED AS EXPECTED,

AND IT'S NOW ANALYZED TO BE ABOUT 10 KT.  THE SHEAR IS FORECAST TO

DIMINISH FURTHER, AND IT SHOULD GENERALLY BE BELOW 10 KT FOR THE

REMAINDER OF THE FORECAST PERIOD.  IN ADDITION, FERNANDA IS

CURRENTLY MOVING OVER A WARM POOL WHERE SEA SURFACE TEMPERATURES