991
WTNT44 KNHC 071454
TCDAT4
TROPICAL STORM ISAIAS DISCUSSION NUMBER 4
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092026
1000 AM CDT WED OCT 07 2026
ISAIAS HAS GOTTEN BETTER ORGANIZED DURING THE PAST SEVERAL HOURS
WITH A LARGE AREA OF DEEP CONVECTION NEAR AND NORTHEAST OF THE
CENTER. RECENT AIR FORCE HURRICANE HUNTER DATA INDICATE THAT THE
CENTER IS RE-FORMING A BIT TO THE NORTH OF THE PREVIOUS ADVISORY
NEARER TO THE MID-LEVEL CENTER, WITH AN ESTIMATED PRESSURE OF
1000 MB DERIVED FROM DROPSONDE DATA. THE INITIAL WIND SPEED IS SET
TO 40 KT IN CONSIDERATION OF INCREASE IN SATELLITE ORGANIZATION AND
THE 4-MB DROPSONDE PRESSURE FALL, CLOSE TO THE UW-CIMSS SATCON
VALUES AND MANY OF THE OTHER OBJECTIVE ESTIMATES.
THE STORM IS MOVING EAST-NORTHEAST AT 7 KT. THE MOTION SHOULD
GRADUALLY BEND NORTHWARD AND INCREASE DURING THE NEXT FEW
DAYS AS A TROUGH ALONG THE NORTHWESTERN GULF COAST AMPLIFIES AND THE
SUBTROPICAL RIDGE EAST OF FLORIDA BUILDS WESTWARD. THIS PATTERN
SHOULD CAUSE A FAST-MOVING ISAIAS TO APPROACH THE NORTHERN GULF
COAST BY FRIDAY AFTERNOON. MODEL GUIDANCE CONTINUES TO BE
SOMEWHAT SPLIT, WITH THE AI-BASED MODELS GENERALLY ON THE RIGHT
SIDE OF THE MODEL ENVELOPE, AND THE PHYSICS BASED MODELS ON THE
LEFT SIDE. THE NEW NHC FORECAST IS NUDGED A BIT EASTWARD, BUT
ISN'T AS FAR EAST AS THE LATEST HFIP CORRECTED CONSENSUS APPROACH
(HCCA) OR GOOGLE DEEPMIND ENSEMBLE MEAN (GDMI). IT IS WORTH NOTING
THAT MANY OF THE STRONGER SOLUTIONS TEND TO BE ON THE EASTERN HALF
OF THE GUIDANCE AND FASTER, WHICH NECESSITATES A VARIETY OF WATCHES
AT THIS TIME.
WITH THE CENTER RE-FORMATION, THE LOW- AND MID-LEVEL CENTERS APPEAR
TO BE COMING INTO BETTER ALIGNMENT. THIS STRUCTURAL CHANGE COULD
FACILITATE RAPID INTENSIFICATION DURING THE NEXT DAY OR TWO GIVEN
LIGHT-TO-MODERATE SHEAR ALONG THE FORECAST TRACK, NEAR-RECORD SSTS
FOR THIS TIME OF THE YEAR AND A VERY MOIST ENVIRONMENT. NEAR
LANDFALL, INCREASING SHEAR COULD CAUSE SOME WEAKENING, BUT IT ISN'T
CERTAIN HOW FAST THE WINDS WILL DIMINISH. REGARDLESS, ISAIAS
SHOULD BE GROWING IN SIZE AS IT APPROACHES THE NORTHERN GULF COAST
DUE TO A TROUGH INTERACTION. THE LATEST GUIDANCE IS VERY CLOSE TO
THE LAST NHC INTENSITY FORECAST, SO LITTLE CHANGES WERE MADE, AND
THE NHC PREDICTION IS JUST BELOW THE CORRECTED-CONSENSUS HCCA.
KEY MESSAGES:
1. ISAIAS IS EXPECTED TO STRENGTHEN INTO A STRONG HURRICANE BEFORE
APPROACHING THE NORTHERN GULF COAST ON FRIDAY. THERE IS AN
INCREASING RISK OF LIFE-THREATENING STORM SURGE ALONG PORTIONS OF
THE NORTHERN GULF COAST, AND A STORM SURGE WATCH HAS BEEN ISSUED
FROM THE MOUTH OF THE MISSISSIPPI RIVER TO YANKEETOWN FLORIDA.
RESIDENTS IN THE WATCH AREA SHOULD FOLLOW ADVICE GIVEN BY LOCAL
OFFICIALS AND EVACUATE IF TOLD TO DO SO.
2. THE RISK OF DAMAGING HURRICANE FORCE-WINDS IS INCREASING OVER
PORTIONS OF THE FLORIDA PANHANDLE, SOUTHERN ALABAMA, AND
MISSISSIPPI. A HURRICANE WATCH HAS BEEN ISSUED FROM BAY ST. LOUIS,
MISSISSIPPI, TO INDIAN PASS, FLORIDA. RESIDENTS IN THESE AREAS
SHOULD PREPARE FOR THE POSSIBILITY OF LONG-DURATION POWER OUTAGES.
3. ISAIAS WILL BRING AREAS OF HEAVY RAINFALL TO THE CENTRAL U.S.
GULF COAST AND MUCH OF THE SOUTHEAST FRIDAY INTO THE WEEKEND. FLASH
AND URBAN FLOODING, ALONG WITH ISOLATED RIVER FLOODING, WILL BE
POSSIBLE.
4. ISAIAS COULD BRING GUSTY WINDS AND AREAS OF HEAVY RAIN TO THE
WESTERN PORTION OF THE YUCATAN PENINSULA OVER THE NEXT DAY OR SO.
FORECAST POSITIONS AND MAX WINDS
INIT 07/1500Z 22.4N 93.6W 40 KT 45 MPH
12H 08/0000Z 22.7N 92.4W 50 KT 60 MPH
24H 08/1200Z 23.4N 90.8W 65 KT 75 MPH
36H 09/0000Z 24.6N 89.2W 80 KT 90 MPH
48H 09/1200Z 26.6N 88.1W 95 KT 110 MPH
60H 10/0000Z 29.2N 87.5W 90 KT 105 MPH
72H 10/1200Z 32.2N 87.6W 45 KT 50 MPH...INLAND
96H 11/1200Z 38.0N 87.5W 20 KT 25 MPH...POST-TROP/INLAND
120H 12/1200Z...DISSIPATED
FORECASTER BLAKE
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