WTPZ42 KNHC 160257 RRA

TCDEP2



HURRICANE NORMA DISCUSSION NUMBER   7

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP172017

900 PM MDT FRI SEP 15 2017



INFRARED SATELLITE IMAGERY INDICATES THAT BANDING ASSOCIATED WITH

NORMA HAS INCREASED DURING THE PAST FEW HOURS.  THE CONVECTIVE CLOUD

TOPS HAVE COOLED AND THE BAND SURROUNDING THE CENTER HAS BECOME A

LITTLE MORE SOLID WITH THE FORMATION OF A RAGGED BANDING EYE. DVORAK

DATA T-NUMBERS FROM BOTH TAFB AND SAB ARE 4.0, AND WITH THE RECENT

INCREASE IN ORGANIZATION THE INITIAL WIND SPEED IS INCREASED TO 65

KT. NORMA BECOMES THE EIGHTH HURRICANE IN THE EASTERN PACIFIC THIS

SEASON.



NORMA SHOULD REMAIN OVER WARM WATER AND WITHIN A LOW SHEAR

ENVIRONMENT DURING THE NEXT 24 TO 36 H.  THESE CONDITIONS FAVOR

STRENGTHENING, BUT THE LARGE SIZE OF NORMA IS LIKELY TO KEEP THE

INTENSIFICATION RATE IN CHECK.  INCREASING VERTICAL SHEAR AND COOLER

WATERS ARE EXPECTED TO IMPART GRADUAL WEAKENING AFTER 48 HOURS.  THE

LATEST NHC INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY

AND IS CLOSE TO THE SHIPS GUIDANCE.



NORMA HAS BEEN MOVING SLOWLY NORTH-NORTHWESTWARD, WITH AN INITIAL

MOTION ESTIMATE OF 335/2 KT.  THE HURRICANE IS FORECAST TO MOVE

SLOWLY NORTHWARD DURING THE NEXT COUPLE OF DAYS, WHILE IT REMAINS

ALONG THE WESTERN SIDE OF A MID-LEVEL RIDGE.  AFTER THAT TIME, THE

ECMWF DEVELOPS A NARROW RIDGE TO THE NORTH OF NORMA WHICH CAUSES THE

HURRICANE TO TURN NORTHWESTWARD.  MEANWHILE, THE GFS KEEPS NORMA ON

A NORTH TRACK OVER THE BAJA CALIFORNIA PENINSULA. THE TREND OF THE

TRACK GUIDANCE HAS BEEN WESTWARD DURING THE PAST SEVERAL CYCLES, SO

THE NHC FORECAST LIES SLIGHTLY WEST OF THE CONSENSUS, AND CLOSER TO