541
WTNT44 KNHC 091454
TCDAT4
HURRICANE ISAIAS DISCUSSION NUMBER 12
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092026
1000 AM CDT FRI OCT 09 2026
AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT CURRENTLY
INVESTIGATING ISAIAS MEASURED A PEAK 700-MB FLIGHT-LEVEL WIND OF
120 KT WITHIN THE EASTERN EYEWALL A FEW HOURS AGO, PROMPTING AN
UPGRADE OF THE HURRICANE TO MAJOR HURRICANE STATUS WITH ESTIMATED
SURFACE WINDS OF 105 KT. BASED ON THE LAST SEVERAL DROPSONDES
RELEASED IN THE EYE, THE CENTRAL PRESSURE APPEARS TO HAVE LEVELED
OFF AROUND 959 MB. ON THE LAST PASS THROUGH THE EASTERN EYEWALL,
JUST ABOUT A HALF HOUR AGO, THE PLANE MEASURED A FLIGHT-LEVEL
WIND OF 111 KT, SUGGESTING THAT THE PEAK WINDS MAY HAVE ALSO
LEVELED OFF. THE EYE ITSELF HAS BECOME CLOUD FILLED IN VISIBLE
SATELLITE IMAGERY, BUT IT IS NOW MOVING INTO RANGE OF SEVERAL
WSR-88D RADARS ALONG THE NORTHERN GULF COAST.
STRONG DEEP-LAYER SHEAR HAS DEFINITELY INCREASED AS FORECAST, WITH
VARIOUS ANALYSES NOW SHOWING 30-40 KT OUT OF THE SOUTHWEST.
HOWEVER, THE SHEAR VECTOR IS NEARLY ALIGNED WITH THE STORM'S
MOTION, WHICH LIMITS ITS ADVERSE EFFECTS, AND UPPER-LEVEL
DIVERGENCE IS ALSO INCREASING OVER THE HURRICANE. THIS SETUP HAS
LIKELY ALLOWED THE HURRICANE TO INTENSIFY THIS MORNING, AND THE
HURRICANE REGIONAL MODELS (HAFS-A, HAFS-B, AND HWRF), AS WELL AS
THE STATISTICAL-DYNAMICAL MODELS (SHIPS AND LGEM), ALL SUGGEST THAT
ISAIAS COULD MAINTAIN MAJOR HURRICANE INTENSITY UP UNTIL ITS
LANDFALL THIS EVENING. THEREFORE, THE NHC OFFICIAL FORECAST DEPICTS
ISAIAS WITH 100-KT WINDS JUST OFFSHORE THE WESTERN FLORIDA
PANHANDLE THIS EVENING. WEAKENING WILL OCCUR AFTER LANDFALL, BUT
SUSTAINED HURRICANE-FORCE WINDS WILL LIKELY OCCUR NEAR AND ALONG
ISAIAS'S TRACK UP TO 100 MILES INLAND FROM THE COAST INTO SOUTHERN
ALABAMA, AND GUSTS TO HURRICANE FORCE COULD EXTEND EVEN FARTHER
NORTH INTO CENTRAL ALABAMA. ISAIAS IS LIKELY TO LOSE ITS TROPICAL
CHARACTERISTICS BY 36 HOURS WHEN IT IS OVER NORTHERN ALABAMA.
AIRCRAFT FIXES INDICATE THAT ISAIAS HAS DRIFTED A BIT EAST OF THE
PREVIOUS FORECAST TRACK. NHC'S TRACK FORECAST LEANS ON THE EASTERN
SIDE OF THE GUIDANCE ENVELOPE, CLOSEST TO THE LATEST HCCA AND GDMI
GUIDANCE, AND IMPLIES A POTENTIAL LANDFALL ALONG THE EXTREME
WESTERN FLORIDA PANHANDLE COAST THIS EVENING. AFTER MOVING INLAND,
THE CENTER OF ISAIAS IS EXPECTED TO CONTINUE NORTHWARD THROUGH
ALABAMA, BEFORE TURNING NORTHEASTWARD OVER THE TENNESSEE AND OHIO
VALLEYS (AS A POST-TROPICAL REMNANT LOW) ON SUNDAY.
NOW THAT THE EYE HAS BECOME VISIBLE IN WSR-88D COASTAL RADARS,
HOURLY TROPICAL CYCLONE UPDATES WILL BE ISSUED BEGINNING AT 11 AM
CDT (1600 UTC).
KEY MESSAGES:
1. A LIFE-THREATENING STORM SURGE IS EXPECTED FROM THE MOUTH OF THE
MISSISSIPPI RIVER TO SUWANNEE, FLORIDA. RESIDENTS UNDER EVACUATION
ORDERS SHOULD LEAVE IMMEDIATELY AND FOLLOW ADVICE FROM LOCAL
OFFICIALS.
2. EXTREMELY DANGEROUS AND DAMAGING HURRICANE FORCE-WINDS ARE
EXPECTED OVER PORTIONS OF THE FLORIDA PANHANDLE, SOUTHERN ALABAMA,
AND SOUTHERN MISSISSIPPI WHERE A HURRICANE WARNING IS IN EFFECT.
RESIDENTS IN THESE AREAS SHOULD HAVE A SAFE ROOM TO RIDE OUT THE
STORM AND PREPARE FOR LONG-DURATION POWER OUTAGES.
3. DAMAGING WIND GUSTS ARE LIKELY OVER A LARGE PORTION OF THE
SOUTHEASTERN UNITED STATES FROM WESTERN AND NORTHERN GEORGIA
WESTWARD OVER MUCH OF CENTRAL AND NORTHERN ALABAMA, SOUTHERN MIDDLE
TENNESSEE, AND MISSISSIPPI, ESPECIALLY IN AREAS OF HIGHER TERRAIN.
RESIDENTS SHOULD SECURE LOOSE OUTDOOR ITEMS, AVOID DRIVING
HIGH-PROFILE VEHICLES, PREPARE FOR POWER OUTAGES, AND BE AWARE OF
THE POTENTIAL FOR FALLING TREES.
4. ISAIAS WILL BRING AREAS OF HEAVY RAINFALL TO THE CENTRAL U.S.
GULF COAST AND MUCH OF THE SOUTHEAST THROUGH THE WEEKEND.
CONSIDERABLE FLASH AND URBAN FLOODING, AND SIGNIFICANT RIVER
FLOODING, ARE POSSIBLE.
5. THE TORNADO POTENTIAL WILL INCREASE THIS AFTERNOON AND CONTINUE
THROUGH TONIGHT. THE GREATEST RISK WILL BE EAST OF THE CENTER,
PARTICULARLY ACROSS THE FLORIDA PANHANDLE INTO SOUTHERN GEORGIA.
THIS RISK WILL CONTINUE SPREADING NORTH-NORTHEAST ACROSS
PARTS OF THE SOUTHEAST ON SATURDAY.
FORECAST POSITIONS AND MAX WINDS
INIT 09/1500Z 27.7N 87.3W 105 KT 120 MPH
12H 10/0000Z 29.7N 86.8W 100 KT 115 MPH
24H 10/1200Z 32.1N 87.1W 55 KT 65 MPH...INLAND
36H 11/0000Z 34.2N 87.2W 35 KT 40 MPH...POST-TROP/INLAND
48H 11/1200Z 36.5N 85.0W 25 KT 30 MPH...POST-TROP/INLAND
60H 12/0000Z 39.1N 81.0W 20 KT 25 MPH...POST-TROP/INLAND
72H 12/1200Z...DISSIPATED
FORECASTER BERG
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page