471
WTNT43 KNHC 281437
TCDAT3
HURRICANE HUMBERTO DISCUSSION NUMBER 16
NWS NATIONAL HURRICANE CENTER MIAMI FL AL082025
1100 AM AST SUN SEP 28 2025
HUMBERTO HAS WEAKENED SLIGHTLY, LIKELY THE RESULT OF AN ONGOING
EYEWALL REPLACEMENT CYCLE, BUT IT REMAINS A POWERFUL HURRICANE. THE
INITIAL INTENSITY OF 130 KT IS BASED PRIMARILY ON A BLEND OF FINAL-T
AND CI DVORAK VALUES FROM TAFB. THAT VALUE IS ON THE HIGH END OF THE
VARIOUS OBJECTIVE ESTIMATES, BUT THE 1210 UTC UW-CIMSS DPRINT VMAX
VALUE WAS ALSO 130 KT. FOR THE NEXT DAY OR TWO, HUMBERTO'S INTENSITY
WILL LIKELY BE DETERMINED LARGELY BY INTERNAL DYNAMICS LIKE
ADDITIONAL EYEWALL REPLACEMENT CYCLES, AND BY HOW LARGE OF AN EYE IT
DEVELOPS. GPM MICROWAVE DATA FROM EARLIER THIS MORNING SHOWED THE
PRESENCE OF A VERY LARGE OUTER RING OF DEEP CONVECTION AROUND
HUMBERTO'S CENTER. IF THAT LARGER RING ULTIMATELY REPLACES
HUMBERTO'S EYEWALL, IT COULD RESULT IN THE HURRICANE HAVING A LOWER
INTENSITY IN THE SHORT TERM THAN CURRENTLY FORECAST, BUT A RAPIDLY
LARGER EXTENT OF HURRICANE-FORCE WINDS.
CONSEQUENTLY, THE MAIN CONCERN FOR HUMBERTO GOING FORWARD IS NOT HOW
STRONG IT WILL BE, BUT HOW LARGE. IN ADDITION TO THE EXPECTED
EXPANSION OF HUMBERTO'S HURRICANE-FORCE INNER CORE, THE
TROPICAL-STORM-FORCE WIND RADII ARE ALSO EXPECTED TO EXPAND QUICKLY
IN THE NEXT FEW DAYS. AS A RESULT OF THIS, EVEN THOUGH THE CORE OF
HUMBERTO IS FORECAST TO MOVE WEST AND THEN NORTH OF BERMUDA,
TROPICAL-STORM-FORCE IMPACTS APPEAR INCREASINGLY LIKELY AND TROPICAL
STORM WATCHES COULD BE REQUIRED THERE LATER TODAY. HUMBERTO IS ALSO
EXPECTED TO PRODUCE SWELLS THAT AFFECT MOST OF THE WESTERN ATLANTIC,
WITH DANGEROUS SURF CONDITIONS STARTING ALONG THE U.S. EAST COAST ON
MONDAY.
HUMBERTO'S INITIAL MOTION HASN'T CHANGED, AND THE TRACK FORECAST
REASONING IS VERY SIMILAR TO PREVIOUS FORECASTS. HUMBERTO SHOULD
MOVE AROUND THE SOUTHWEST PERIPHERY OF THE SUBTROPICAL RIDGE FOR
THE NEXT COUPLE OF DAYS, MOVING WEST OF BERMUDA ON TUESDAY. THE
HURRICANE SHOULD THEN ACCELERATE EAST-NORTHEASTWARD AS IT BECOMES
POST-TROPICAL. HUMBERTO'S WINDS SHOULD EXPAND FURTHER AS ITS
INTENSITY GRADUALLY DECREASES THROUGH THE MIDDLE OF THE WEEK, BUT IT
IS FORECAST TO REMAIN A VERY POWERFUL HURRICANE-FORCE LOW, EVEN
AFTER IT BECOMES POST-TROPICAL.
KEY MESSAGES:
1. THERE IS AN INCREASING RISK OF TROPICAL-STORM-FORCE WINDS
AFFECTING BERMUDA BY LATE TUESDAY. INTERESTS THERE SHOULD MONITOR
THE PROGRESS OF HUMBERTO AND WATCHES COULD BE ISSUED LATER TODAY.
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 THE U.S. EAST COAST ON MONDAY.
FORECAST POSITIONS AND MAX WINDS
INIT 28/1500Z 24.6N 64.3W 130 KT 150 MPH
12H 29/0000Z 25.7N 65.7W 125 KT 145 MPH
24H 29/1200Z 27.3N 67.2W 120 KT 140 MPH
36H 30/0000Z 29.3N 68.4W 110 KT 125 MPH
48H 30/1200Z 31.6N 69.0W 100 KT 115 MPH
60H 01/0000Z 33.7N 68.3W 95 KT 110 MPH
72H 01/1200Z 35.6N 65.0W 90 KT 105 MPH
96H 02/1200Z 39.7N 51.0W 80 KT 90 MPH...POST-TROP/EXTRATROP
120H 03/1200Z...DISSIPATED
FORECASTER D. ZELINSKY
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