WTPZ43 KNHC 181441 RRA

TCDEP3



TROPICAL DEPRESSION THIRTEEN-E DISCUSSION NUMBER   1

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP132017

800 AM PDT FRI AUG 18 2017



DEEP CONVECTION ASSOCIATED WITH THE DISTURBANCE LOCATED OVER THE

OPEN EASTERN PACIFIC OCEAN HAS BECOME BETTER ORGANIZED EARLY THIS

MORNING, AND A PRIMARY CONVECTIVE BAND NOW WRAPS AROUND THE WESTERN

HALF OF THE CIRCULATION.  SHORTWAVE-IR AND FIRST-LIGHT VISIBLE

IMAGERY SUGGEST THAT A COMPLEX, BUT CLOSED SURFACE CIRCULATION

EXISTS. NHC IS THEREFORE INITIATING ADVISORIES ON TROPICAL

DEPRESSION THIRTEEN-E.



THE INITIAL INTENSITY IS SET AT 30 KT, IN AGREEMENT WITH THE MAX

WINDS MEASURED IN AN EARLIER ASCAT PASS AND THE LATEST DVORAK

CLASSIFICATION FROM TAFB.  LIGHT EASTERLY VERTICAL WIND SHEAR HAS

THUS FAR LIMITED CONVECTION TO THE WESTERN HALF OF THE CIRCULATION,

BUT THE GFS AND ECMWF AGREE THAT THE SHEAR WILL LESSEN AS THE SYSTEM

MOVES FARTHER WEST.  OVERALL, THE ENVIRONMENT APPEARS CONDUCIVE FOR

INTENSIFICATION FOR THE NEXT 3 DAYS OR SO, AND THE NHC FORECAST

INDICATES THAT THE CYCLONE WILL BECOME A HURRICANE BY THE END OF

THIS WEEKEND.  AFTER THAT TIME, THE CYCLONE WILL BEGIN TO WEAKEN

OVER MUCH COOLER WATERS.  THE NHC FORECAST IS VERY CLOSE TO THE

MULTI-MODEL CONSENSUS, IVCN.



SINCE THE CENTER HAS ONLY RECENTLY FORMED, THE INITIAL MOTION

ESTIMATE IS A FAIRLY UNCERTAIN 285/13 KT.  THERE IS FAIRLY GOOD

AGREEMENT AMONG THE GLOBAL MODELS THAT THE TROPICAL CYCLONE WILL

MOVE GENERALLY WESTWARD TO WEST-NORTHWESTWARD FOR THE NEXT 72 H

ALONG THE SOUTHERN BOUNDARY OF A MID-LEVEL RIDGE THAT EXTENDS

WESTWARD WELL INTO THE EASTERN PACIFIC BASIN.  A WEAKNESS IN THE