373
WTNT43 KNHC 300855
TCDAT3
HURRICANE HUMBERTO DISCUSSION NUMBER 23
NWS NATIONAL HURRICANE CENTER MIAMI FL AL082025
500 AM AST TUE SEP 30 2025
HUMBERTO IS A HIGHLY SHEARED HURRICANE. STRONG WESTERLY VERTICAL
WIND SHEAR HAS CAUSED THE CYCLONE TO CONTINUE ITS WEAKENING TREND.
THIS IS WELL-DEMONSTRATED BY A RECENT AMSR2 MICROWAVE IMAGE, WHICH
SHOWS THAT THE CONVECTION HAS BEEN SHEARED OFF FROM THE WESTERN HALF
OF HUMBERTO'S CIRCULATION. ALTHOUGH THE LOW-LEVEL CENTER IS STILL
UNDERNEATH THE CONVECTIVE AREA IN GOES-19 IMAGERY, IT'S CLOSE TO THE
WESTERN EDGE OF THE CONVECTION. THE CYCLONE HAS TAKEN ON AN
ELONGATED COMMA SHAPE, WITH DEEP CONVECTION EXTENDING WELL OFF TO
THE SOUTHEAST. SUBJECTIVE INTENSITY ESTIMATES RANGE FROM 77-90 KT,
AND OBJECTIVE INTENSITY ESTIMATES FROM UW-CIMSS RANGE FROM 70-85 KT.
THE ADVISORY INTENSITY IS ADJUSTED DOWNWARD TO 85 KT BASED PRIMARILY
ON THIS DATA, AND ALSO TAKING INTO ACCOUNT ASCAT AND AIR FORCE
HURRICANE HUNTER DATA FROM 8-9 HOURS AGO.
HUMBERTO IS MOVING TOWARD THE NORTH-NORTHWEST, OR 340 DEGREES AT 15
KT, IN BETWEEN A SUBTROPICAL RIDGE TO ITS EAST AND TROPICAL STORM
IMELDA TO ITS WEST. HUMBERTO HAS TRACKED FARTHER WEST THAN THE
PREVIOUS NHC TRACK FORECAST. A NORTHWARD TURN IS EXPECTED OVER THE
NEXT FEW HOURS AS THE RIDGE SHIFTS EAST AND WEAKENS. ON WEDNESDAY,
A VERY LARGE MID- TO UPPER-LEVEL TROUGH IS EXPECTED TO AMPLIFY OVER
THE NORTH ATLANTIC, CAUSING HUMBERTO TO TURN SHARPLY TO THE
EAST-NORTHEAST AND ACCELERATE. THE NHC TRACK FORECAST HAS BEEN
ADJUSTED WELL TO THE LEFT OF THE PREVIOUS FORECAST AT THE 12 AND 24
HOUR POINTS, AND IS A BIT SLOWER THAN THE PREVIOUS FORECAST AT 36-48
HOURS. THE NEW NHC FORECAST IS VERY NEAR THE VARIOUS CONSENSUS
AIDS. THIS TRACK TAKES THE CORE OF HUMBERTO WELL WEST AND THEN
NORTH OF BERMUDA.
STEADY WEAKENING IS EXPECTED OVER THE NEXT 12 H AS NORTHWESTERLY
VERTICAL WIND SHEAR AND INTRUSIONS OF DRY AIR PERSIST, FOLLOWED BY
MORE GRADUAL WEAKENING OVER THE NEXT DAY OR TWO. BY LATE WEDNESDAY,
HUMBERTO IS EXPECTED TO MERGE WITH A MID-TO UPPER-LEVEL TROUGH, AND
THAT SHOULD CAUSE THE SYSTEM TO QUICKLY DEVELOP FRONTAL FEATURES AND
COMPLETE EXTRATROPICAL TRANSITION. THE GLOBAL MODELS AGREE THAT
HUMBERTO WILL THEN BECOME EXTREMELY ELONGATED ALONG THE FRONT AND
WILL LIKELY NO LONGER HAVE A CLOSED CIRCULATION BY THURSDAY
AFTERNOON, SO THE NEW NHC FORECAST HAS MOVED FORWARD THE TIME OF
DISSIPATION. IT IS IMPORTANT TO CONVEY THAT HUMBERTO IS FORECAST TO
BE A LARGE AND POWERFUL CYCLONE UNTIL IT DISSIPATES ON THURSDAY.
THE LARGE EXTRATROPICAL LOW IN COMBINATION WITH IMELDA WILL CAUSE
ROUGH MARINE CONDITIONS OVER A LARGE PORTION OF THE WESTERN AND
CENTRAL ATLANTIC. SEE KEY MESSAGES BELOW FOR MORE INFORMATION.
KEY MESSAGES:
1. HUMBERTO'S OUTER RAINBANDS COULD PRODUCE GUSTY WINDS AND HEAVY
RAINFALL OVER BERMUDA TODAY AND WEDNESDAY. PLEASE FOLLOW LOCAL
UPDATES FROM THE BERMUDA WEATHER SERVICE FOR IMPACTS FROM BOTH
HUMBERTO AND IMELDA.
2. DANGEROUS MARINE CONDITIONS, INCLUDING HIGH SURF AND
LIFE-THREATENING RIP CURRENTS, WILL CONTINUE TO AFFECT BEACHES OF
THE NORTHERN CARIBBEAN, BAHAMAS, BERMUDA, AND MUCH OF THE EAST COAST
OF THE UNITED STATES THROUGH THE WEEK.
FORECAST POSITIONS AND MAX WINDS
INIT 30/0900Z 31.6N 69.4W 85 KT 100 MPH
12H 30/1800Z 33.5N 69.4W 75 KT 85 MPH
24H 01/0600Z 35.5N 67.7W 75 KT 85 MPH
36H 01/1800Z 36.5N 63.8W 70 KT 80 MPH...POST-TROP/EXTRATROP
48H 02/0600Z 37.3N 57.9W 60 KT 70 MPH...POST-TROP/EXTRATROP
60H 02/1800Z...DISSIPATED
FORECASTER HAGEN
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