370
WTNT43 KNHC 292053
TCDAT3
HURRICANE HUMBERTO DISCUSSION NUMBER 21
NWS NATIONAL HURRICANE CENTER MIAMI FL AL082025
500 PM AST MON SEP 29 2025
AFTER SOME BRIEF RE-INTENSIFICATION THIS MORNING, SATELLITE IMAGERY
DEPICTS THAT HUMBERTO HAS STARTED TO FEEL THE IMPACTS OF WIND SHEAR.
THE RING OF DEEP CONVECTION HAS BECOME A LITTLE MORE BROKEN ON
INFRARED IMAGERY, PARTICULARLY ON THE WESTERN SIDE OF THE SYSTEM.
EARLIER HURRICANE HUNTER AIRCRAFT DATA DEPICTED THAT THE EYEWALL WAS
OPEN ON THE SOUTHWEST SIDE, AND RECENT MICROWAVE IMAGERY SHOWS THAT
THE EYEWALL MAY BE COMPLETELY OPEN ON THE WESTERN SIDE. AS THE
PREVIOUS AIRCRAFT WAS DEPARTING, THE PRESSURE HAD COME UP A COUPLE
MILLIBARS WHICH ALSO SUGGESTS THE SYSTEM MAY HAVE BEGUN TO WEAKEN,
AND THUS THAT TREND IS FOLLOWED IN THIS ADVISORY. USING THE LATEST
SATELLITE TRENDS, AND A COMBINATION OF INTENSITY ESTIMATES WITH
PREVIOUS AIRCRAFT DATA, THE INTENSITY IS LOWERED TO 120 KT FOR THIS
ADVISORY. ANOTHER AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS
SCHEDULED TO INVESTIGATE THE SYSTEM LATE THIS EVENING TO HELP
EVALUATE THE INTENSITY AND STRUCTURE OF THE SYSTEM.
HUMBERTO IS MOVING NORTH-NORTHWESTWARD AT AN ESTIMATED MOTION OF
330/11 KT. THE SYSTEM SHOULD CONTINUE TO ROUND THE WESTERN
PERIPHERY OF THE MID-LEVEL RIDGE AND GRADUALLY TURN TO THE NORTH
THEN NORTHEAST OVER THE NEXT DAY OR SO. A TROUGH MOVING INTO THE
NORTHERN ATLANTIC WILL THEN PICK UP THE SYSTEM, AND CAUSE HUMBERTO
TO ACCELERATE TO THE NORTHEAST TO EAST-NORTHEAST OVER THE NEXT
SEVERAL DAYS. THERE IS SLIGHTLY MORE ALONG-TRACK SPREAD WITH THE
FORWARD SPEED TOWARDS THE END OF THE FORECAST PERIOD IN THE LATEST
GUIDANCE ENVELOPE. THE NHC TRACK FORECAST IS NEAR THE PREVIOUS ONE,
HOWEVER SLIGHTLY SLOWER AT LONG RANGE, AND LIES NEAR THE CONSENSUS
TRACK AIDS.
A WEAKENING TREND HAS STARTED WITH HUMBERTO, AS WIND SHEAR APPEARS
TO HAVE STARTED TO DISRUPT THE CIRCULATION. WIND SHEAR IS FORECAST
TO CONTINUE INCREASING OVER THE SYSTEM, AND SEA SURFACE TEMPERATURES
WILL ALSO COOL ALONG THE FORECAST TRACK. MODEL SIMULATED IR IMAGES
DEPICTS THAT HUMBERTO WILL BECOME MORE ASYMMETRIC WITH MOST OF THE
CONVECTION DISPLACED TO THE EASTERN SIDE OF THE CIRCULATION DUE TO
THE SHEAR. IN ABOUT 60 H, BOTH THE GFS AND ECMWF GUIDANCE 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, GUSTY WINDS AND HEAVY RAINFALL ARE POSSIBLE
WITHIN OUTER RAINBANDS LATE TUESDAY AND WEDNESDAY.
KEY MESSAGES:
1. GUSTY WINDS AND HEAVY RAINFALL ARE POSSIBLE WITHIN OUTER
RAINBANDS OF HUMBERTO. THE TROPICAL STORM WATCH HAS BEEN REPLACED
WITH A HURRICANE WATCH, DUE TO THE FORECAST OF IMELDA. PLEASE FOLLOW
LOCAL UPDATES FROM BERMUDA WEATHER SERVICE FOR IMPACTS FROM
HUMBERTO.
2. DANGEROUS MARINE CONDITIONS, INCLUDING HIGH SURF AND
LIFE-THREATENING RIP CURRENTS, ARE AFFECTING BEACHES OF THE NORTHERN
CARIBBEAN, BAHAMAS, BERMUDA, AND MUCH OF THE EAST COAST OF THE
UNITED STATES.
FORECAST POSITIONS AND MAX WINDS
INIT 29/2100Z 29.1N 68.1W 120 KT 140 MPH
12H 30/0600Z 30.8N 68.8W 105 KT 120 MPH
24H 30/1800Z 33.4N 68.6W 90 KT 105 MPH
36H 01/0600Z 35.4N 66.4W 85 KT 100 MPH
48H 01/1800Z 36.8N 61.8W 75 KT 85 MPH
60H 02/0600Z 38.4N 54.9W 65 KT 75 MPH...POST-TROP/EXTRATROP
72H 02/1800Z 41.5N 46.0W 60 KT 70 MPH...POST-TROP/EXTRATROP
96H 03/1800Z...DISSIPATED
FORECASTER KELLY
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