553
WTNT44 KNHC 062034
TCDAT4
TROPICAL STORM DEXTER DISCUSSION NUMBER 12
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042025
500 PM AST WED AUG 06 2025
SIMILAR TO THE PAST COUPLE OF DAYS, THE HIGH VERTICAL WIND SHEAR
OVER DEXTER CAUSED ITS LOW-LEVEL CIRCULATION TO BECOME EXPOSED TO
THE WEST OF THE THE DEEP CONVECTION EARLIER THIS AFTERNOON. A
SCATTEROMETER PASS RECEIVED AFTER THE PRIOR ADVISORY ALSO SUGGESTED
THAT DEXTER'S VORTEX IS BECOMING MORE ELONGATED, WITH SIGNS OF A
BAROCLINIC ZONE STARTING TO TAKE SHAPE TO THE NORTHEAST OF THE
CENTER. THESE SIGNATURES SUGGEST THAT DEXTER MAY SOON UNDERGO
EXTRATROPICAL TRANSITION. THE EARLIER SCATTEROMETER PASS HAD A PEAK
WIND RETRIEVAL OF 43 KT, AND THAT VALUE, COMBINED WITH SIMILAR
SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES, SUPPORT MAINTAINING 45
KT THIS ADVISORY.
DEXTER CONTINUES TO GRADUALLY ACCELERATE TO THE EAST-NORTHEAST,
WITH THE ESTIMATED MOTION NOW AT 070/14 KT. THE STORM REMAINS WELL
EMBEDDED IN THE MID-LATITUDE WESTERLY FLOW AS A SHORTWAVE TROUGH
DROPS SOUTHWARD TOWARDS DEXTER. THE SUBSEQUENT TROUGH INTERACTION IS
FORECAST TO KEEP DEXTER MOVING QUICKLY EAST-NORTHEASTWARD WITH JUST
A SUBTLE BEND NORTHEASTWARD FROM 24-48 H. COMPARED TO 24 H AGO, THE
TRACK GUIDANCE IS IN MUCH BETTER AGREEMENT WITH LESS ALONG-TRACK
SPREAD, AND THE LATEST NHC TRACK FORECAST IS VERY SIMILAR TO THE
PRIOR ADVISORY, NEAR THE SIMPLE AND CORRECTED CONSENSUS AIDS.
WITH VERTICAL WIND SHEAR NOW AROUND 40 KT AND THE CYCLONE ALSO
CROSSING THE NORTH EDGE OF THE GULF STREAM, MOST OF THE SUBSEQUENT
STRENGTHENING SHOWN IN THE INTENSITY FORECAST WILL BE DUE TO
BAROCLINIC PROCESSES AS DEXTER UNDERGOES EXTRATROPICAL TRANSITION.
THE GLOBAL AND REGIONAL HURRICANE MODEL FIELDS SHOWS DEXTER'S
METAMORPHOSIS, WITH TO DEVELOPMENT OF FRONTAL FEATURES AS THE WIND
FIELD BECOMES QUITE ASYMMETRIC. IN FACT, THE MAXIMUM SUSTAINED WINDS
IN 24-36 H ARE LIKELY RELATED TO A STING JET THAT CURVES
CYCLONICALLY AROUND THE CYCLONE'S WESTERN FLANK DURING THIS TIME
FRAME. THE HURRICANE-REGIONAL MODELS, AND EVEN THE MOST RECENT 12
UTC ECMWF RUN SHOW WINDS UP TO HURRICANE-FORCE IN THE SOUTHWEST
QUADRANT. THUS, THE LATEST NHC INTENSITY FORECAST WILL NOW
EXPLICITLY SHOW A 65-KT EXTRATROPICAL CYCLONE IN 36 H. AFTER
OCCLUSION, THE LOW WILL SLOWLY WEAKEN THROUGH THE REMAINDER OF THE
FORECAST PERIOD, ULTIMATELY DISSIPATING BY EARLY NEXT WEEK IN THE
FAR NORTHEASTERN ATLANTIC.
FORECAST POSITIONS AND MAX WINDS
INIT 06/2100Z 40.0N 56.3W 45 KT 50 MPH
12H 07/0600Z 40.6N 53.5W 50 KT 60 MPH
24H 07/1800Z 41.9N 49.3W 60 KT 70 MPH...POST-TROP/EXTRATROP
36H 08/0600Z 43.5N 45.3W 65 KT 75 MPH...POST-TROP/EXTRATROP
48H 08/1800Z 44.8N 41.5W 50 KT 60 MPH...POST-TROP/EXTRATROP
60H 09/0600Z 45.5N 37.1W 40 KT 45 MPH...POST-TROP/EXTRATROP
72H 09/1800Z 46.0N 32.5W 35 KT 40 MPH...POST-TROP/EXTRATROP
96H 10/1800Z 47.0N 24.5W 30 KT 35 MPH...POST-TROP/EXTRATROP
120H 11/1800Z...DISSIPATED
FORECASTER PAPIN
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page