WTNT43 KNHC 192053 RRA

TCDAT3



TROPICAL DEPRESSION THIRTEEN DISCUSSION NUMBER   1

NWS NATIONAL HURRICANE CENTER MIAMI FL       AL132016

500 PM AST MON SEP 19 2016



SATELLITE IMAGERY, SCATTEROMETER DATA, AND SHIP OBSERVATIONS

INDICATE THAT THE LARGE LOW PRESSURE SYSTEM LOCATED SOUTHWEST OF THE

CABO VERDE ISLANDS HAS MAINTAINED A WELL-DEFINED CIRCULATION AND HAS

DEVELOPED SUFFICIENT ORGANIZED CONVECTION TO BE CONSIDERED A

TROPICAL DEPRESSION. THE INITIAL INTENSITY IS SET AT 30 KT BASED ON

SCATTEROMETER WIND DATA OF NEAR 30 KT ALONG WITH DVORAK SATELLITE

INTENSITY ESTIMATES T2.5/35 KT AND T2.0/30 KT FROM TAFB AND SAB,

RESPECTIVELY. THE CENTRAL PRESSURE IS BASED ON REPORTS FROM SHIP

D5ET2 DURING IS TRAVERSAL THROUGH THE CENTER OF THE CYCLONE OVER THE

PAST 12 HOURS. THE DEPRESSION IS A LARGE TROPICAL CYCLONE WITH A

WIND FIELD THAT IS MORE THAN 400 N MI IN DIAMETER.



THE INITIAL MOTION ESTIMATE IS AN UNCERTAIN 280/10 KT, BASED

PRIMARILY ON SCATTEROMETER AND MICROWAVE SATELLITE DATA.  THE

DEPRESSION IS LOCATED ALONG THE SOUTHERN PERIPHERY OF A LARGE

DEEP-LAYER RIDGE THAT IS FOREAST TO STEER THE CYCLONE WESTWARD FOR

THE NEXT 24 HOURS OR SO, FOLLOWED BY WEST-NORTHWESTWARD MOTION

THROUGH 120 HOURS. THE OFFICIAL FORECAST TRACK LIES CLOSE TO THE

CONSENSUS MODEL TVCN THROUGH 96 HOURS, AND THEN LEANS TOWARD A BLEND

OF THE ECMWF, UKMET, AND CMC MODELS SINCE THE GFS DISSIPATES

THE CYCLONE BY 120 HOURS, A SCENARIO THAT SEEMS PREMATURE GIVEN THE

CURRENT LARGE SIZE OF THE CYCLONE.



VERTICAL WIND SHEAR IS FORECAST TO REMAIN LOW AT LESS THAN 10 KT

OVER THE CYCLONE FOR THE NEXT 48 HOURS, WHICH FAVORS STEADY

INTENSIFICATION. HOWEVER, THE MID-LEVEL MOISTURE IS ONLY EXPECTED TO=