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WTNT44 KNHC 011455
TCDAT4
HURRICANE IMELDA DISCUSSION NUMBER 20
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092025
1100 AM EDT WED OCT 01 2025
THE AIR FORCE HURRICANE HUNTERS INVESTIGATING IMELDA THIS MORNING
HAVE FOUND THAT THE HURRICANE IS STRENGTHENING. THEY REPORTED A
CLOSED, CIRCULAR EYEWALL DURING THEIR TWO PASSES THROUGH THE STORM,
AND DROPSONDE DATA INDICATE THE CENTRAL PRESSURE HAS FALLEN TO
AROUND 966 MB. THE AIRCRAFT MEASURED PEAK 700-MB FLIGHT-LEVEL WINDS
OF 97 KT IN THE SOUTHEASTERN QUADRANT OF IMELDA, WHICH SUPPORTS
RAISING THE INITIAL INTENSITY TO 85 KT FOR THIS ADVISORY.
IMELDA IS MOVING QUICKLY EAST-NORTHEASTWARD (065/17 KT) WITHIN THE
FLOW AHEAD OF A WESTERN ATLANTIC DEEP-LAYER TROUGH. IN THE NEAR
TERM, THE TRACK MODELS AGREE THAT THE CORE OF IMELDA WILL MOVE NEAR
OR OVER BERMUDA TONIGHT INTO EARLY THURSDAY, WITH CONDITIONS THERE
EXPECTED TO DETERIORATE LATER TODAY. ONCE IMELDA PASSES BERMUDA AND
BECOMES EXTRATROPICAL, THE FORECAST BECOMES MUCH MORE UNCERTAIN
GIVEN THE SIGNIFICANT SPREAD IN THE TRACK GUIDANCE AND ENSEMBLES. IN
GENERAL, MOST GLOBAL MODELS SHOW THE EXTRATROPICAL LOW BECOMING
CAPTURED BY THE UPPER TROUGH, WHICH RESULTS IN A NORTHEASTWARD
MOTION ACROSS THE NORTH ATLANTIC THROUGH THE 5-DAY PERIOD. THE
OUTLYING GFS SOLUTION SHOWS THE TROUGH MISSING THE LOW, AND AS A
RESULT THE GFS IS ALMOST 1500 MILES AWAY FROM THE ECMWF AT DAY 5.
ONCE AGAIN, THE LONG-RANGE NHC FORECAST IS WEIGHTED MORE HEAVILY
TOWARD A CONSENSUS OF THE ECMWF AND GOOGLE DEEP MIND SOLUTIONS.
THE IMPROVED INNER CORE STRUCTURE OF THE HURRICANE AND THE POTENTIAL
FOR POSITIVE TROUGH INTERACTION COULD SUPPORT SOME ADDITIONAL
STRENGTHENING BEFORE IMELDA REACHES BERMUDA, DESPITE INCREASING
SOUTHWESTERLY SHEAR EXPECTED OVER THE HURRICANE. THIS IS REFLECTED
IN THE UPDATED NHC INTENSITY FORECAST, WHICH LIES ON THE HIGH END OF
THE GUIDANCE ENVELOPE. EXTRATROPICAL TRANSITION IS NOW FORECAST IN
24 H, AFTER WHICH SOME GRADUAL WEAKENING IS PREDICTED. HOWEVER,
IMELDA WILL REMAIN A POWERFUL EXTRATROPICAL CYCLONE FOR MUCH OF THE
FORECAST PERIOD AS ITS WIND FIELD EXPANDS WHILE THE CYCLONE MOVES
DEEPER INTO THE MID-LATITUDES. AS A RESULT, LARGE SWELL AND
DANGEROUS MARINE AND RIP CURRENT CONDITIONS WILL CONTINUE TO AFFECT
MUCH OF THE CENTRAL AND WESTERN ATLANTIC FOR THE NEXT SEVERAL DAYS.
KEY MESSAGES:
1. IMELDA IS EXPECTED TO BRING DAMAGING HURRICANE-FORCE WINDS AND
LARGE AND DAMAGING WAVES TO BERMUDA WHEN IT PASSES NEAR OR OVER THE
ISLAND TONIGHT. PREPARATIONS TO PROTECT LIFE AND PROPERTY SHOULD BE
RUSHED TO COMPLETION, AS TROPICAL STORM CONDITIONS ARE EXPECTED TO
SPREAD ACROSS THE REGION BEGINNING LATER TODAY.
2. HEAVY RAINFALL COULD CAUSE FLASH FLOODING ACROSS BERMUDA LATER
TODAY INTO THURSDAY.
3. SWELLS AND HIGH SURF FROM IMELDA ARE EXPECTED TO PRODUCE
DANGEROUS MARINE CONDITIONS AND RIP CURRENTS ALONG MUCH OF THE EAST
COAST OF THE UNITED STATES DURING THE NEXT SEVERAL DAYS.
FORECAST POSITIONS AND MAX WINDS
INIT 01/1500Z 31.0N 70.4W 85 KT 100 MPH
12H 02/0000Z 31.9N 66.7W 90 KT 105 MPH
24H 02/1200Z 32.6N 61.5W 85 KT 100 MPH...POST-TROP/EXTRATROP
36H 03/0000Z 33.8N 56.2W 75 KT 85 MPH...POST-TROP/EXTRATROP
48H 03/1200Z 35.8N 52.4W 65 KT 75 MPH...POST-TROP/EXTRATROP
60H 04/0000Z 38.0N 50.0W 60 KT 70 MPH...POST-TROP/EXTRATROP
72H 04/1200Z 40.7N 48.2W 55 KT 65 MPH...POST-TROP/EXTRATROP
96H 05/1200Z 45.9N 40.4W 50 KT 60 MPH...POST-TROP/EXTRATROP
120H 06/1200Z 50.0N 32.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
FORECASTER REINHART
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