554
WTNT44 KNHC 271450
TCDAT4
TROPICAL DEPRESSION NINE DISCUSSION NUMBER 4
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092025
1100 AM EDT SAT SEP 27 2025
DEEP CONVECTION HAS INCREASED OVER THE DISTURBANCE THIS MORNING, AND
DROPSONDE DATA FROM A NOAA HURRICANE HUNTER AIRCRAFT INDICATE
PRESSURES ARE GRADUALLY FALLING BETWEEN THE CENTRAL BAHAMAS AND
EASTERN CUBA. IN ADDITION, DROPSONDE AND FLIGHT-LEVEL WIND DATA FROM
THE AIRCRAFT SHOW THE LOW-LEVEL CIRCULATION HAS BECOME BETTER
DEFINED. BASED ON THESE DEVELOPMENTS, THE DISTURBANCE IS NOW
CLASSIFIED AS A 30-KT TROPICAL DEPRESSION FOR THIS ADVISORY. AN AIR
FORCE RESERVE HURRICANE HUNTER MISSION IS SCHEDULED TO INVESTIGATE
THE DISTURBANCE LATER TODAY.
THE INITIAL MOTION OF THE DEPRESSION IS AN UNCERTAIN 320/5 KT. A
NORTH-NORTHWESTWARD MOTION IS EXPECTED AS THE SYSTEM MOVES BETWEEN A
DEEP-LAYER TROUGH OVER THE SOUTHEASTERN U.S. AND A SUBTROPICAL RIDGE
OVER THE ATLANTIC. THE TRACK MODELS ARE IN GOOD AGREEMENT THROUGH
72 H, AND LITTLE CHANGE WAS MADE TO THIS PORTION OF THE NHC TRACK
FORECAST. THIS BRINGS THE CENTER OVER THE CENTRAL AND NORTHWESTERN
BAHAMAS THIS WEEKEND, MOVING ROUGHLY PARALLEL TO BUT OFFSHORE THE
EAST COAST OF FLORIDA. DURING THIS TIME, STRENGTHENING IS FORECAST
AS THE SYSTEM MOVES OVER WARM WATERS WITHIN A DIFFLUENT UPPER-LEVEL
ENVIRONMENT. HOWEVER, THE AFOREMENTIONED TROUGH SHOULD IMPART
MODERATE SOUTHERLY SHEAR OVER THE CYCLONE, LIKELY RESULTING IN AN
ASYMMETRIC STORM STRUCTURE. THE NEAR-TERM NHC INTENSITY FORECAST WAS
RAISED SLIGHTLY FROM THE PREVIOUS ONE AND STILL SHOWS A 65-KT
HURRICANE EARLY NEXT WEEK OFF THE SOUTHEASTERN U.S COAST.
THE TRACK FORECAST BEYOND 72 H IS STILL OF LOW CONFIDENCE, WITH A
BIFURCATION OF SOLUTIONS NOTED IN THE VARIOUS DETERMINISTIC MODELS
AND GFS, ECMWF, AND GOOGLE DEEPMIND ENSEMBLE MEMBERS. MUCH DEPENDS
ON THE FUTURE TRACK OF HURRICANE HUMBERTO, THE EXTENT TO WHICH IT
ERODES THE STEERING RIDGE OVER THE ATLANTIC, AND THE STRENGTH AND
TIMING OF AN UPPER TROUGH EXPECTED TO DIG OVER THE NORTHWESTERN
ATLANTIC NEXT WEEK. A MAJORITY OF THE DETERMINISTIC GUIDANCE
SUGGESTS THAT THE SYSTEM WILL SLOW DOWN OR BRIEFLY STALL OFFSHORE OF
THE SOUTHEAST U.S. COAST BEFORE TURNING SHARPLY EASTWARD. THERE
REMAINS CONSIDERABLE UNCERTAINTY IN HOW QUICKLY THIS MIGHT OCCUR,
AND IT MUST BE NOTED THAT SOME ENSEMBLE SOLUTIONS STILL SHOW THE
SYSTEM REACHING THE COAST. FOR NOW, THE NHC FORECAST CONTINUES TO
SHOW AN EASTWARD TURN AT DAYS 4-5, BUT AT A MUCH SLOWER FORWARD
SPEED THAN MOST OF THE MODELS.
GIVEN THE RISK OF TROPICAL-STORM-FORCE WINDS ALONG THE EAST COAST OF
FLORIDA, A TROPICAL STORM WATCH HAS BEEN ISSUED FROM THE PALM
BEACH/MARTIN COUNTY LINE NORTHWARD TO THE FLAGLER/VOLUSIA COUNTY
LINE. ALTHOUGH IT IS STILL TOO EARLY TO SPECIFY THE DETAILS OF
POTENTIAL IMPACTS ALONG THE REMAINDER OF THE SOUTHEAST U.S. COAST,
THERE REMAINS A RISK OF HEAVY RAINFALL, STORM SURGE, AND WIND
IMPACTS.
KEY MESSAGES:
1. THE DEPRESSION IS EXPECTED TO STRENGTHEN AND BRING TROPICAL STORM
CONDITIONS TO PORTIONS OF THE CENTRAL AND NORTHWESTERN BAHAMAS
THROUGH SUNDAY NIGHT. TROPICAL STORM CONDITIONS ARE ALSO POSSIBLE
ALONG PORTIONS OF THE EAST COAST OF CENTRAL FLORIDA BEGINNING
MONDAY, WHERE A TROPICAL STORM WATCH HAS BEEN ISSUED.
2. RAINFALL ASSOCIATED WITH THIS SYSTEM WILL CONTINUE TO IMPACT
EASTERN CUBA, HISPANIOLA, JAMAICA, AND THE BAHAMAS THROUGH THE
WEEKEND, WHICH WILL LIKELY PRODUCE FLASH AND URBAN FLOODING.
MUDSLIDES ARE POSSIBLE IN THE HIGHER TERRAIN.
3. THERE IS A SIGNIFICANT THREAT OF HEAVY RAINFALL EARLY NEXT WEEK
FROM COASTAL GEORGIA THROUGH THE CAROLINAS AND INTO THE SOUTHERN
MID-ATLANTIC STATES, WHICH COULD CAUSE FLASH, URBAN, AND RIVER
FLOODING.
4. THE DEPRESSION IS EXPECTED TO BE AT OR NEAR HURRICANE INTENSITY
WHEN IT APPROACHES THE SOUTHEAST U.S. COAST EARLY NEXT WEEK, WHERE
THERE IS A RISK OF STORM SURGE AND WIND IMPACTS. ALTHOUGH IT IS TOO
SOON TO SPECIFY THE EXACT LOCATION AND MAGNITUDE OF IMPACTS,
RESIDENTS SHOULD CLOSELY MONITOR THE LATEST FORECAST UPDATES AND
ENSURE THAT THEY HAVE THEIR HURRICANE PLAN IN PLACE.
FORECAST POSITIONS AND MAX WINDS
INIT 27/1500Z 22.0N 76.2W 30 KT 35 MPH
12H 28/0000Z 23.0N 76.7W 35 KT 40 MPH
24H 28/1200Z 24.4N 77.3W 40 KT 45 MPH
36H 29/0000Z 26.1N 77.7W 45 KT 50 MPH
48H 29/1200Z 27.9N 78.2W 55 KT 65 MPH
60H 30/0000Z 29.6N 78.6W 60 KT 70 MPH
72H 30/1200Z 30.7N 78.8W 65 KT 75 MPH
96H 01/1200Z 31.3N 77.5W 65 KT 75 MPH
120H 02/1200Z 31.5N 75.0W 60 KT 70 MPH
FORECASTER REINHART
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