WTPZ41 KNHC 312034 RRA

TCDEP1



HURRICANE NORMAN DISCUSSION NUMBER  15

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP162018

200 PM PDT FRI AUG 31 2018



SATELLITE DERIVED MID AND UPPER TROPOSPHERIC WINDS AND THE UW-CIMSS

SHEAR ANALYSIS INDICATE THAT THE PERSISTENT NORTHEASTERLY VERTICAL

SHEAR HAS INCREASED TO 20-25 KT, AND HAS CONTINUED TO IMPEDE OUTER

DEEP CONVECTIVE BANDING DEVELOPMENT IN THE NORTHERN PORTION OF

NORMAN'S INNER CORE.  THE CLOUD PATTERN HAS ALSO BECOME SOMEWHAT

ASYMMETRIC (NORTHEAST TO SOUTHWEST).  A SERIES OF RECENT MICROWAVE

IMAGES, HOWEVER, SHOW THAT THE EYEWALL IS NOW CLOSED, ALTHOUGH THE

EYE TEMPERATURE HAS WARMED A BIT DURING THE PAST 6 HOURS.  THE

DVORAK SATELLITE INTENSITY CLASSIFICATIONS FROM TAFB AND SAB ALSO

SUPPORT THESE OBSERVATIONS, AND THE INITIAL INTENSITY IS REDUCED TO

110 KT.



ALTHOUGH THERE MAY STILL BE SOME FLUCTUATIONS IN INTENSITY, GRADUAL

WEAKENING IS FORECAST THROUGH DAY 5, PRIMARILY DUE TO THE SHEAR

PREDICTED BY THE GFS AND ECMWF DECAY-SHIPS INTENSITY MODELS.

INTRUSION OF STABLE AIR MASS, BEYOND DAY 3, NORTHEAST OF THE

HAWAIIAN ISLANDS WILL ALSO PROMOTE THIS WEAKENING TREND.  THE

OFFICIAL INTENSITY FORECAST HAS CHANGED LITTLE FROM THE PREVIOUS

ADVISORY, AND IS STILL BASED ON THE HFIP CORRECTED CONSENSUS

APPROACH AND IVCN INTENSITY MODELS.



THE INITIAL MOTION IS ESTIMATED TO BE WEST-SOUTHWEST, OR 255/7 KT.

AN ANCHORED MID- TO UPPER-LEVEL RIDGE THAT STRETCHES

WEST-SOUTHWESTWARD FROM THE BAJA CALIFORNIA PENINSULA SHOULD STEER

NORMAN WEST-SOUTHWESTWARD DURING THE NEXT 12 HOURS OR SO.

AFTERWARD, THE SOUTHWESTERN-MOST SEGMENT OF THE RIDGE AXIS BETWEEN

MIRIAM AND NORMAN WEAKENS AS MIRIAM CONTINUES ON A NORTHWARD TRACK.