643
WTNT43 KNHC 291441
TCDAT3
HURRICANE HUMBERTO DISCUSSION NUMBER 20
NWS NATIONAL HURRICANE CENTER MIAMI FL AL082025
1100 AM AST MON SEP 29 2025
AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT FOUND HUMBERTO HAS
STRENGTHENED THIS MORNING. THE AIRCRAFT DEPICTED THAT THE SYSTEM HAS
COMPLETED AN EYEWALL REPLACEMENT CYCLE, WITH THE OUTER EYEWALL AS
DEPICTED ON EARLIER MICROWAVE IMAGERY NOW DOMINANT, AND THE OLD
INNER EYEWALL HAS COLLAPSED. THE AIRCRAFT HOWEVER DID DEPICT THAT
THE EYEWALL IS OPEN ON THE SOUTHWEST SIDE WHICH IS LIKELY DUE TO THE
IMPACTS OF INCREASING WIND SHEAR. MAXIMUM FLIGHT LEVEL WINDS IN THE
NORTHEAST QUADRANT WERE 138 KT, WHICH SUPPORTED THE INCREASED
INTENSITY TO 125 KT AT THE INTERMEDIATE ADVISORY. USING THE LATEST
HURRICANE HUNTER AND SCATTEROMETER WIND DATA, THE WIND RADII HAVE
BEEN SLIGHTLY ADJUSTED AND THE INTENSITY IS HELD AT 125 KT FOR THIS
ADVISORY.
HUMBERTO IS MOVING NORTHWESTWARD AT AN ESTIMATED MOTION OF 325/ 11
KT, ALONG THE SOUTHWESTERN PERIPHERY OF A MID-LEVEL SUBTROPICAL
RIDGE. A GRADUAL TURN TO THE NORTH THEN NORTHEAST OVER THE NEXT DAY
OR SO IS ANTICIPATED AS THE SYSTEM ROUNDS THE WESTERN PERIPHERY OF
THE RIDGE, AND THE NHC FORECAST HAS BEEN SHIFTED SLIGHTLY TO THE
LEFT CLOSER TO THE CONSENSUS AIDS IN THE SHORT TERM. THE SYSTEM WILL
THEN BEGIN TO MOVE NORTHEAST TO EAST-NORTHEASTWARD AS THE SYSTEM IS
PICKED UP BY A TROUGH MOVING INTO THE NORTH ATLANTIC. THE NHC
FORECAST IS SIMILAR TO THE PREVIOUS THROUGH THE END OF THE FORECAST
PERIOD, WITH A SLIGHT NUDGE TOWARDS THE LATEST CONSENSUS AIDS.
SOME FLUCTUATIONS IN INTENSITY ARE POSSIBLE OVER THE NEXT 12 H OR
SO. THEREAFTER, INCREASING WIND SHEAR AND COOLING SEA SURFACE
TEMPERATURES SHOULD INDUCE A WEAKENING TREND. THE WIND SHEAR WILL
ALSO CAUSE HUMBERTO BECOME QUITE ASYMMETRIC WITH MOST OF THE
CONVECTION DISPLACED TO THE EASTERN SIDE OF THE CIRCULATION. IN
ABOUT 60 H, GLOBAL MODELS DEPICT THAT THE SYSTEM SHOULD MERGE WITH
THE PREVIOUSLY MENTIONED TROUGH DIGGING ACROSS THE NORTH ATLANTIC
AND DEVELOP FRONTAL FEATURES. AS THE SYSTEM BECOMES EXTRATROPICAL
ACROSS THE NORTH ATLANTIC, THE WIND FIELD IS ANTICIPATED TO GROW IN
SIZE. THE LATEST NHC INTENSITY FORECAST LIES ON THE HIGHER END OF
THE GUIDANCE ENVELOPE GIVEN THE LATEST INCREASE IN INTENSITY, AND
THEN SHOWS WEAKENING THROUGHOUT THE PERIOD. BY 96H, THE SYSTEM IS
EXPECTED TO DISSIPATE AND MERGE WITHIN THE LARGER TROUGH.
ALONG THE FORECAST TRACK, HUMBERTO IS EXPECTED TO MOVE TO THE WEST
AND NORTH OF BERMUDA, ALTHOUGH THERE IS A POSSIBILITY OF
TROPICAL-STORM-FORCE WINDS OCCURING OVER THE ISLAND LATE TUESDAY AND
WEDNESDAY WITHIN OUTER RAINBANDS.
KEY MESSAGES:
1. TROPICAL-STORM-FORCE WINDS COULD BEGIN TO AFFECT BERMUDA BY LATE
TUESDAY, AND A TROPICAL STORM WATCH IS IN EFFECT FOR THE ISLAND.
INTERESTS THERE SHOULD CONTINUE TO MONITOR THE PROGRESS OF HUMBERTO.
2. DANGEROUS MARINE CONDITIONS, INCLUDING HIGH SURF AND
LIFE-THREATENING RIP CURRENTS, ARE AFFECTING BEACHES OF THE NORTHERN
CARIBBEAN, BAHAMAS, AND BERMUDA. THE DANGEROUS SURF CONDITIONS ARE
EXPECTED TO BEGIN AFFECTING MUCH OF THE EAST COAST OF THE U.S.
TODAY.
FORECAST POSITIONS AND MAX WINDS
INIT 29/1500Z 28.0N 67.6W 125 KT 145 MPH
12H 30/0000Z 29.6N 68.5W 115 KT 130 MPH
24H 30/1200Z 32.1N 69.0W 105 KT 120 MPH
36H 01/0000Z 34.4N 67.9W 95 KT 110 MPH
48H 01/1200Z 36.1N 64.5W 90 KT 105 MPH
60H 02/0000Z 37.4N 58.5W 80 KT 90 MPH...POST-TROP/EXTRATROP
72H 02/1200Z 40.6N 49.0W 75 KT 85 MPH...POST-TROP/EXTRATROP
96H 03/1200Z...DISSIPATED
FORECASTER KELLY
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