WTPZ45 KNHC 140233 RRA

TCDEP5



TROPICAL DEPRESSION FIFTEEN-E DISCUSSION NUMBER  10

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP152017

800 PM PDT WED SEP 13 2017



DURING THE AFTERNOON HOURS, THE MID-LEVEL CENTER OF THE DEPRESSION

BECAME COMPLETELY REMOVED FROM THE NOW EXPOSED LOW-LEVEL CENTER.  A

SMALL TIGHT SWIRL EMBEDDED WITHIN A BROADER, ELONGATED, LOW-LEVEL

CIRCULATION IS STILL EVIDENT, BUT DEEP CONVECTION IS LIMITED TO A

BAND DISPLACED ABOUT 60 N MI TO THE WEST OF THE CENTER.  THE INITIAL

INTENSITY HAS BEEN HELD AT 30 KT, BASED ON EARLIER ASCAT DATA. GIVEN

THE POOR CONVECTIVE STRUCTURE OF THE DEPRESSION, LITTLE CHANGE IN

INTENSITY IS EXPECTED FOR THE NEXT DAY OR SO. AFTER THAT TIME, THE

GFS AND ECMWF BOTH FORECAST THAT THE UPPER-LEVEL WIND PATTERN WILL

BECOME MORE FAVORABLE FOR INTENSIFICATION.  ONCE THAT HAPPENS, MOST

OF THE INTENSITY GUIDANCE FORECASTS THAT THE CYCLONE WILL BEGIN TO

STEADILY STRENGTHEN, ESPECIALLY AFTER ABOUT 72 H.  MY FORECAST IS A

LITTLE HIGHER THAN THE PREVIOUS NHC FORECAST AT 96 H AND 120 H, AND

IS VERY CLOSE TO IVCN.



THE DEPRESSION HAS BEEN NEARLY STATIONARY FOR THE PAST 6 HOURS. THE

INITIAL MOTION ESTIMATE ASSUMES AT LEAST SOME MOVEMENT, AND IS A

RATHER UNCERTAIN 270/02 KT.  THE GLOBAL MODELS AGREE THAT THE

CYCLONE WILL REMAIN TRAPPED IN WEAK STEERING FLOW THROUGHOUT THE

FORECAST PERIOD, BUT VARY GREATLY ON HOW MUCH IT WILL MOVE.  A

COMPLICATING FACTOR IS THAT THE GFS SUGGESTS THAT THE LOW-LEVEL

CENTER MAY REFORM UNDERNEATH THE MID-LEVEL CENTER TO THE SOUTH. MY

FORECAST ASSUMES THAT THE CURRENT CENTER OF CIRCULATION WILL

PERSIST, BUT A LARGER CHANGE MAY BE REQUIRED IF SUCH A REFORMATION