392
WTNT44 KNHC 042130
TCDAT4
TROPICAL STORM DEXTER DISCUSSION NUMBER 4
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042025
500 PM AST MON AUG 04 2025
THERE IS NOT A LOT NEW TO REPORT WITH DEXTER THIS AFTERNOON. THE
CENTER REMAINS PARTIALLY EXPOSED, WITH PERIODIC BURSTS OF DEEP
CONVECTION FIRING OFF ALONG THE DOWNSHEAR-RIGHT SIDE OF THE STORM.
THIS ACTIVITY CONTINUES TO STRUGGLE ROTATING UPSHEAR DUE TO WESTERLY
VERTICAL WIND SHEAR WHICH HAS NOW INCREASED ABOVE 20 KT. THE 18 UTC
DVORAK ESTIMATES FROM TAFB AND SAB WERE T3.0/45 KT AND T2.0/30 KT
RESPECTIVELY. OBJECTIVE INTENSITY ESTIMATES ALSO RANGE FROM 35 TO 45
KT. EARLIER SCATTEROMETER DATA RECEIVED AFTER THE PRIOR ADVISORY
ONLY HAD A PEAK VALUE OF 33 KT. THE INITIAL INTENSITY REMAINS 40 KT
FOR THIS ADVISORY, A BLEND OF ALL THE VARIOUS INTENSITY ESTIMATES.
THERE ARE SEVERAL MESOVORTICIES ROTATING AROUND THE MEAN CENTER, BUT
DEXTER IN GENERAL REMAINS ON A NORTHEASTWARD HEADING AT 050/13 KT. A
NARROW MID-LEVEL RIDGE ORIENTED NORTHEAST TO SOUTHWEST FROM THE
AZORES TO BERMUDA SHOULD ENABLE DEXTER TO CONTINUE MOVING
NORTHEASTWARD TO EAST-NORTHEASTWARD, AS LONG AS IT REMAINS
VERTICALLY COHERENT. THE VERTICAL DEPTH LIKELY PLAYS A ROLE IN
DEXTER'S FUTURE FORWARD MOTION, WITH SIGNIFICANT ALONG-TRACK SPREAD
PERSISTING IN THE TRACK GUIDANCE THIS AFTERNOON. THE NHC TRACK
FORECAST IS ON THE FASTER SIDE OF THE GUIDANCE ENVELOPE, CLOSE TO
THE MOST RECENT 12 UTC ECMWF FORECAST TRACK. HOWEVER, IT REMAINS
POSSIBLE THAT DEXTER COMPLETELY DECOUPLES FROM ITS MID-LEVEL
CIRCULATION AND MISSES PHASING WITH THE TROUGH DIGGING SOUTHWARD
FROM ATLANTIC CANADA. INSTEAD OF ACCELERATING NORTHEASTWARD, THIS
LATTER SCENARIO COULD RESULT IN THE STORM SLOWING DOWN AS IT BECOMES
A SHALLOW CYCLONE. FOR NOW, THE LATEST NHC TRACK FORECAST IS CLOSE
TO THE PRIOR ONE.
AS SHEAR CONTINUE TO INCREASE OVER THE TROPICAL CYCLONE, FORECASTED
TO BE ABOVE 30 KT IN 12 H, ITS WINDOW FOR FURTHER TROPICAL
INTENSIFICATION IS CLOSING. THE INTENSITY GUIDANCE IS A BIT LOWER
THIS AFTERNOON. IN RESPONSE, THE NHC INTENSITY FORECAST NOW HOLDS
DEXTER AT 40 KT UNTIL IT UNDERGOES EXTRATROPICAL TRANSITION SOMETIME
BETWEEN 60-72 H, WHERE A SLIGHT AMOUNT OF INTENSIFICATION IS STILL
SHOWN. THE INTENSITY FORECAST IS IN THE MIDDLE OF THE GUIDANCE
ENVELOPE. AS MENTIONED PREVIOUSLY, DEXTER'S FINAL STRUCTURE REMAINS
QUITE UNCERTAIN NEAR THE END OF THE FORECAST PERIOD, AND IT IS
ENTIRELY POSSIBLE THE STORM COULD BECOME A REMNANT LOW INSTEAD OF AN
EXTRATROPICAL CYCLONE BY THE LATTER HALF OF THIS WEEK.
FORECAST POSITIONS AND MAX WINDS
INIT 04/2100Z 36.1N 66.2W 40 KT 45 MPH
12H 05/0600Z 37.1N 64.5W 40 KT 45 MPH
24H 05/1800Z 38.2N 62.5W 40 KT 45 MPH
36H 06/0600Z 39.2N 60.3W 40 KT 45 MPH
48H 06/1800Z 39.8N 57.5W 40 KT 45 MPH
60H 07/0600Z 40.7N 53.2W 40 KT 45 MPH
72H 07/1800Z 42.5N 48.2W 45 KT 50 MPH...POST-TROP/EXTRATROP
96H 08/1800Z 45.0N 41.4W 45 KT 50 MPH...POST-TROP/EXTRATROP
120H 09/1800Z 48.2N 29.9W 40 KT 45 MPH...POST-TROP/EXTRATROP
FORECASTER PAPIN
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