WTPZ45 KNHC 240240 RRA

TCDEP5



TROPICAL STORM SEYMOUR DISCUSSION NUMBER   4

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP202016

900 PM MDT SUN OCT 23 2016



SEYMOUR'S CONVECTIVE PATTERN HAS CONTINUED TO IMPROVE SINCE THE

PREVIOUS ADVISORY, WITH THE DEVELOPMENT OF A MID-LEVEL EYE FEATURE

NOTED IN 23/2250Z AND 24/0107Z SSMI/S MICROWAVE IMAGES. DVORAK

CLASSIFICATIONS FROM TAFB AND SAB ARE T3.0/45 KT AND T3.5/55 KT,

RESPECTIVELY, AND T3.6/57 KT FROM UW-CIMSS ADT. THE INITIAL

INTENSITY IS SET ON THE LOW SIDE OF THESE ESTIMATES AT 45 KT FOR

THIS ADVISORY, WHICH COULD BE CONSERVATIVE.



THE INITIAL MOTION ESTIMATE IS 290/13 KT. FOR THE NEXT 72 H, THE

GLOBAL MODELS REMAIN IN EXCELLENT AGREEMENT ON SEYMOUR MOVING

WEST-NORTHWESTWARD ALONG THE SOUTHERN PERIPHERY OF A DEEP-LAYER

RIDGE LOCATED OVER MEXICO. AFTER THAT, THE CYCLONE IS EXPECTED TO

TURN NORTHWARD AROUND THE WESTERN PORTION OF THE RIDGE AND AHEAD OF

A SHORTWAVE TROUGH FORECAST TO APPROACH SEYMOUR FROM THE NORTHWEST

BY LATE WEDNESDAY. THE OFFICIAL FORECAST TRACK LIES BASICALLY DOWN

THE MIDDLE OF THE GUIDANCE ENVELOPE, CLOSE TO THE MULTI-MODEL

CONSENSUS TVCN.



THE GLOBAL AND REGIONAL MODELS INDICATE ENVIRONMENTAL CONDITIONS ARE

FORECAST TO BE QUITE FAVORABLE FOR ADDITIONAL STRENGTHENING TO OCCUR

DURING THE NEXT 3 DAYS. IN FACT, DUE TO A COMBINATION OF THE

VERTICAL SHEAR BEING LOW AT AROUND 5 KT, MID-LEVEL HUMIDITY VALUES

BEING NEAR 70 PERCENT, SEA-SURFACE TEMPERATURES EXPECTED TO BE AT

LEAST 29 DEG C, AND THE RECENT DEVELOPMENT OF A MID-LEVEL EYE, A

PERIOD OF RAPID INTENSIFICATION IS FORECAST TO OCCUR FOR THE NEXT

24 HOURS. THIS TREND IS SUPPORTED BY THE SHIPS AND LGEM STATISTICAL=