WTNT42 KNHC 282041 RRA

TCDAT2



TROPICAL STORM BONNIE DISCUSSION NUMBER   5

NWS NATIONAL HURRICANE CENTER MIAMI FL       AL022016

500 PM EDT SAT MAY 28 2016



A 1431Z ASCAT-B OVERPASS INDICATED TWO 34-KT WIND VECTORS EXISTED IN

THE NORTHWEST QUADRANT OF THE TROPICAL CYCLONE IN A REGION OF DEEP

CONVECTION THAT WAS NOT SAMPLED DURING THE EARLIER RECONNAISSANCE

MISSION. CONVECTION BRIEFLY WEAKENED, BUT HAS REDEVELOPED AND

PERSISTED IN THAT SAME PART OF THE STORM CIRCULATION FOR THE PAST 5

HOURS. FURTHERMORE, NOAA DOPPLER VELOCITY RADAR DATA FROM CHARLESTON

AND JACKSONVILLE HAVE INDICATED WINDS RANGING FROM 50-55 KT BETWEEN

15,000 AND 20,000 FEET IN THE SAME AREA OF THE 34-KT ASCAT WIND

VECTORS. BASED ON THESE DATA, THE DEPRESSION HAS BEEN UPGRADED

TO TROPICAL STORM BONNIE.



THE INITIAL MOTION ESTIMATE IS 320/09 KT. THE EXPOSED LOW-LEVEL

CENTER NEAR THE SOUTHEASTERN EDGE OF THE DEEP CONVECTIVE CLOUD

CANOPY HAS BEEN EASY TO TRACK OVER THE PAST SEVERAL HOURS, AND HAS

ESSENTIALLY BEEN MOVING ALONG THE PREVIOUS FORECAST TRACK. THE NHC

MODEL GUIDANCE REMAINS IN GOOD AGREEMENT ON BONNIE GRADUALLY TURNING

TOWARD THE NORTH-NORTHWEST AS IT MOVES AROUND THE WEST SIDE OF A

DEEP-LAYER RIDGE, AND MOVING ONSHORE BETWEEN CHARLESTON AND

BEAUFORT, SOUTH CAROLINA, IN ABOUT 18-24 HOURS. AFTER LANDFALL A

MID-LEVEL SHORTWAVE TROUGH MOVING NORTHEASTWARD OUT OF THE

MISSISSIPPI VALLEY REGION IS EXPECTED TO SIGNIFICANTLY WEAKEN THE

RIDGE, CAUSING THE STEERING TO COLLAPSE. THE RESULT IS THAT BONNIE

IS FORECAST TO STALL OR MEANDER ALONG THE COASTAL REGION OF SOUTH

CAROLINA IN 24-36 HOURS BEFORE DRIFTING OFF TO THE EAST OR NORTHEAST

BY 48 HOURS. THE NHC FORECAST TRACK IS SIMILAR TO THE PREVIOUS=