682
WTPZ45 KNHC 020850
TCDEP5
TROPICAL STORM OCTAVE DISCUSSION NUMBER 9
NWS NATIONAL HURRICANE CENTER MIAMI FL EP152025
200 AM PDT THU OCT 02 2025
THE OVERALL SATELLITE PRESENTATION OF OCTAVE HAS CHANGED LITTLE
SINCE THE PREVIOUS ADVISORY, THOUGH THE PREVIOUSLY WELL-DEFINED
CURVED BANDING TO THE SOUTH AND WEST OF THE CENTER HAS BECOME MORE
RAGGED IN RECENT HOURS. THE CYCLONE CONTINUES TO BE AFFECTED BY
MODERATE EASTERLY SHEAR, ANALYZED AT AROUND 17 KT BY UW-CIMSS. THIS
SHEAR IS RESTRICTING OUTFLOW IN THE EASTERN SEMICIRCLE AND KEEPING
THE LOW-LEVEL CENTER NEAR THE EASTERN EDGE OF THE DEEP CONVECTION.
RECENT SUBJECTIVE DVORAK ESTIMATES FROM TAFB AND SAB WERE 3.5/55 KT
AND 4.0/65 KT, RESPECTIVELY, WHILE UW-CIMSS OBJECTIVE ESTIMATES HAVE
RANGED FROM 48 TO 59 KT OVER THE PAST FEW HOURS. BASED ON A BLEND OF
THESE DATA, AND WITH LITTLE CHANGE IN THE OVERALL STRUCTURE, THE
INITIAL INTENSITY IS HELD AT 55 KT.
OCTAVE IS MOVING SLIGHTLY NORTH OF DUE WEST, OR 280 DEGREES AT 7 KT.
A WEST TO WEST-NORTHWEST MOTION IS EXPECTED DURING THE NEXT FEW DAYS
AS THE CYCLONE IS STEERED ALONG THE SOUTHERN FLANK OF A SUBTROPICAL
RIDGE TO ITS NORTH. AFTER DAY 3, OCTAVE SHOULD SLOW AS A LONGWAVE
TROUGH APPROACHES FROM THE NORTHWEST, WEAKENING THE RIDGE AND
OVERALL STEERING FLOW. A DEVELOPING DISTURBANCE OR TROPICAL
CYCLONE OFFSHORE OF THE SOUTHWESTERN OR WEST-CENTRAL COAST OF
MEXICO IS THEN FORECAST TO ERODE THE SUBTROPICAL RIDGE TO THE EAST
OF OCTAVE, CAUSING THE CYCLONE TO TURN EASTWARD BY DAYS 4 AND 5.
THE UPDATED NHC FORECAST HAS BEEN ADJUSTED SLIGHTLY SOUTHWARD TO
ACCOUNT FOR OCTAVE’S MORE WESTWARD RECENT MOTION AND THE LATEST
MODEL TRENDS. CONSIDERABLE ALONG- AND CROSS-TRACK SPREAD REMAINS
IN THE EXTENDED RANGE, AND THE FORECAST TRACK REPRESENTS A BLEND OF
THE MULTI-MODEL CONSENSUS AND AI-BASED GUIDANCE.
OCTAVE WILL REMAIN OVER WARM WATER AND WITHIN A MOIST ENVIRONMENT
DURING THE NEXT FEW DAYS. HOWEVER, VERTICAL WIND SHEAR IS EXPECTED
TO FLUCTUATE BETWEEN MODERATE AND STRONG LEVELS DURING THE NEXT 36
HOURS, WHICH SHOULD PREVENT SIGNIFICANT INTENSIFICATION. AS A
RESULT, LITTLE CHANGE IN STRENGTH IS FORECAST DURING THIS PERIOD.
SOME MODEST STRENGTHENING IS POSSIBLE BETWEEN 48 AND 96 HOURS AS
SHEAR DECREASES, THOUGH COOLING SEA SURFACE TEMPERATURES AND
GRADUALLY DRIER MID-LEVEL AIR SHOULD LIMIT INTENSIFICATION. OCTAVE
IS STILL FORECAST TO REACH HURRICANE STRENGTH BY DAYS 3 AND 4,
REMAINING BELOW SOME OF THE MORE AGGRESSIVE HURRICANE REGIONAL MODEL
SOLUTIONS. BY DAY 5, WEAKENING IS LIKELY AS OCTAVE MOVES INTO A
MORE STABLE, DRIER AIR MASS AND ENCOUNTERS INCREASING SOUTHEASTERLY
SHEAR. THE FORECAST REMAINS CLOSE TO THE PREVIOUS ONE AND LIES NEAR
THE HIGHER END OF THE GUIDANCE ENVELOPE.
FORECAST POSITIONS AND MAX WINDS
INIT 02/0900Z 12.1N 117.9W 55 KT 65 MPH
12H 02/1800Z 12.3N 118.6W 55 KT 65 MPH
24H 03/0600Z 12.8N 119.8W 55 KT 65 MPH
36H 03/1800Z 13.3N 121.1W 55 KT 65 MPH
48H 04/0600Z 13.9N 122.4W 55 KT 65 MPH
60H 04/1800Z 14.4N 123.5W 60 KT 70 MPH
72H 05/0600Z 14.9N 124.0W 65 KT 75 MPH
96H 06/0600Z 15.6N 123.4W 65 KT 75 MPH
120H 07/0600Z 15.6N 121.1W 50 KT 60 MPH
FORECASTER JELSEMA (CPHC)
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