923
WTNT44 KNHC 040242
TCDAT4
TROPICAL STORM DEXTER DISCUSSION NUMBER 1
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042025
1100 PM AST SUN AUG 03 2025
THE AREA OF LOW PRESSURE LOCATED SEVERAL HUNDRED MILES OFF THE COAST
OF NORTH CAROLINA HAS BEEN PRODUCING PERSISTENT DEEP CONVECTION FOR
MUCH OF THE DAY, AND IT APPEARS TO HAVE SEPARATED FROM THE FRONTAL
ZONE FROM WHICH IT FORMED. ALTHOUGH SURFACE TROUGHING STILL EXTENDS
NORTHEAST AND SOUTHWEST OF THE LOW ITSELF, MODEL ANALYSES SHOW
THAT THE LOW IS NOW LOCATED SOUTHEAST OF THE STRONGEST TEMPERATURE
AND MOISTURE GRADIENTS, INDICATING THAT IT IS NO LONGER FRONTAL AND
HAS MADE THE TRANSITION TO A TROPICAL STORM. THE LOW-LEVEL CENTER
IS LOCATED ON THE SOUTHWESTERN EDGE OF THE DEEP CONVECTION DUE TO
MODERATE SOUTHWESTERLY SHEAR. MAXIMUM WINDS ARE ESTIMATED TO BE 40
KT BASED ON A VERY RECENT ASCAT PASS, AND THE CYCLONE IS THEREFORE
BEING DESIGNATED AS TROPICAL STORM DEXTER.
THE INITIAL MOTION IS EAST-NORTHEASTWARD, OR 070/10 KT, WITH DEXTER
EMBEDDED WITHIN MID-LATITUDE WESTERLY FLOW ON THE NORTHWESTERN SIDE
OF THE SUBTROPICAL RIDGE. REMAINING NORTH OF THE RIDGE, DEXTER IS
EXPECTED TO MOVE ON A NORTHEASTERLY OR EAST-NORTHEASTERLY TRAJECTORY
FOR THE NEXT 3-4 DAYS. WHILE THERE IS NOT MUCH CROSS-TRACK SPREAD
AMONG THE GUIDANCE, THERE ARE SOME SPEED DIFFERENCES, MOST NOTABLY
WITH THE GFS SHOWING DEXTER GETTING TRAPPED BENEATH THE RIDGE AND
MEANDERING FOR A COUPLE OF DAYS. THE NHC TRACK FORECAST GOES WITH
THE MORE PROGRESSIVE SOLUTION, AND IS CLOSEST TO THE HCCA AND GDM
ENSEMBLE MEAN.
THE MODERATE SHEAR CURRENTLY AFFECTING DEXTER IS EXPECTED TO
INCREASE TO OVER 20 KT IN 12-24 HOURS, AND THEN TO ABOUT 30 KT IN
36-48 HOURS. AS A RESULT, NOT MUCH STRENGTHENING IS ANTICIPATED.
MUCH OF THE INTENSITY GUIDANCE SHOWS A FAIRLY STEADY INTENSITY
BETWEEN 40-50 KT THROUGH 72 HOURS, AND THE NHC FORECAST THEREFORE
TAKES THE MIDDLE OF THE ROAD AND SHOWS A PEAK OF 45 KT. DEXTER IS
LIKELY TO BE POST-TROPICAL BY 60 HOURS, IF NOT SOONER, AS THE
STRONGER SHEAR STRIPS THE STORM'S CONVECTION AWAY. THE BULK OF THE
GLOBAL MODELS SUGGEST IT COULD THEN BECOME EXTRATROPICAL AGAIN BY
DAY 4 AND THEN BE ABSORBED BY A FRONT BY DAY 5, BUT THERE IS A LOT
OF UNCERTAINTY IN THAT FORECAST.
FORECAST POSITIONS AND MAX WINDS
INIT 04/0300Z 34.3N 69.4W 40 KT 45 MPH
12H 04/1200Z 35.1N 67.7W 45 KT 50 MPH
24H 05/0000Z 36.4N 65.3W 45 KT 50 MPH
36H 05/1200Z 37.7N 63.1W 45 KT 50 MPH
48H 06/0000Z 38.5N 61.3W 45 KT 50 MPH
60H 06/1200Z 39.0N 59.3W 45 KT 50 MPH...POST-TROPICAL
72H 07/0000Z 39.3N 56.9W 40 KT 45 MPH...POST-TROPICAL
96H 08/0000Z 40.5N 50.8W 35 KT 40 MPH...POST-TROP/EXTRATROP
120H 09/0000Z...DISSIPATED
FORECASTER BERG
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