090
WTPZ45 KNHC 010853
TCDEP5
TROPICAL STORM OCTAVE DISCUSSION NUMBER 5
NWS NATIONAL HURRICANE CENTER MIAMI FL EP152025
200 AM MST WED OCT 01 2025
THE SATELLITE PRESENTATION OF OCTAVE HAS IMPROVED DURING THE PAST
SEVERAL HOURS, WITH A WELL-DEFINED CURVED BAND NOW WRAPPING MORE
THAN HALFWAY AROUND THE LOW-LEVEL CENTER. THIS IMPROVEMENT IN
STRUCTURE APPEARS TO BE DUE TO A DECREASE IN VERTICAL WIND SHEAR,
WHICH HAS LESSENED TO AROUND 16 KT ACCORDING TO THE LATEST UW-CIMSS
ANALYSIS. THE MOST RECENT SUBJECTIVE DVORAK INTENSITY ESTIMATES
FROM TAFB AND SAB ALSO INDICATE A STRONGER SYSTEM, BOTH COMING IN
AT 3.5/55 KT, WHILE THE UW-CIMSS OBJECTIVE ESTIMATES ARE LOWER,
RANGING BETWEEN 33 AND 40 KT SINCE THE PREVIOUS ADVISORY. BASED ON
A BLEND OF THESE DATA, AND CONSIDERING THE IMPROVED SATELLITE
PRESENTATION, THE INITIAL INTENSITY HAS BEEN RAISED TO 50 KT FOR
THIS ADVISORY, WHICH MAY BE CONSERVATIVE.
OCTAVE IS ESTIMATED TO BE MOVING NORTH-NORTHWESTWARD, OR 335 DEGREES
AT 6 KT. THIS GENERAL MOTION IS EXPECTED TO CONTINUE TODAY AS THE
CYCLONE MOVES INTO A WEAKNESS IN THE SUBTROPICAL RIDGE CREATED BY A
DISTURBANCE TO ITS NORTH. ONCE THAT DISTURBANCE IS ABSORBED BY
OCTAVE’S CIRCULATION, A MID-LEVEL RIDGE IS FORECAST TO BECOME
RE-ESTABLISHED TO THE NORTH OF THE CYCLONE, STEERING IT WESTWARD TO
WEST-NORTHWESTWARD FROM TONIGHT THROUGH SATURDAY. BY 120 HOURS,
OCTAVE IS EXPECTED TO SLOW CONSIDERABLY AND TURN EASTWARD AS A
LONGWAVE TROUGH APPROACHES FROM THE NORTHWEST AND THE SUBTROPICAL
RIDGE TO ITS EAST IS ERODED BY A DEVELOPING TROPICAL CYCLONE
OFFSHORE OF SOUTHWESTERN MEXICO. THE NEW NHC TRACK FORECAST HAS
BEEN SHIFTED WEST OF THE PREVIOUS ONE TO ACCOUNT FOR THE DELAY IN
THE CYCLONE TURNING TOWARD THE NORTH-NORTHWEST AND TO BETTER MATCH
THE LATEST GUIDANCE TRENDS. THE FORECAST LIES NEAR THE MIDDLE OF
THE GUIDANCE ENVELOPE AND IS CLOSE TO A BLEND OF THE GDMI, FSSE,
TVCE, AND HCCA TRACK AIDS.
OCTAVE WILL REMAIN OVER WARM WATER AND WITHIN A MOIST ENVIRONMENT
FOR THE NEXT SEVERAL DAYS. HOWEVER, VERTICAL WIND SHEAR IS FORECAST
TO FLUCTUATE BETWEEN MODERATE AND STRONG LEVELS, WHICH SHOULD HINDER
SIGNIFICANT INTENSIFICATION. SOME ADDITIONAL STRENGTHENING IS
POSSIBLE TODAY, FOLLOWED BY LITTLE CHANGE IN INTENSITY OVER THE NEXT
FEW DAYS. MODEST INTENSIFICATION COULD OCCUR BY DAYS 4 AND 5 AS THE
SHEAR RELAXES, ALTHOUGH SEA SURFACE TEMPERATURES WILL BE SLIGHTLY
COOLER AND THE MID-LEVEL ENVIRONMENT LESS MOIST BY THAT TIME.
CONFIDENCE IN THE INTENSITY FORECAST REMAINS LOW DUE TO CONSIDERABLE
SPREAD AMONG THE GUIDANCE. THE OFFICIAL FORECAST HAS BEEN ADJUSTED
HIGHER TO ACCOUNT FOR THE CYCLONE’S IMPROVED STRUCTURE AND IS MOST
CLOSELY ALIGNED WITH THE SHIPS AND LGEM INTENSITY AIDS.
FORECAST POSITIONS AND MAX WINDS
INIT 01/0900Z 11.1N 114.8W 50 KT 60 MPH
12H 01/1800Z 11.8N 115.2W 55 KT 65 MPH
24H 02/0600Z 12.5N 116.2W 55 KT 65 MPH
36H 02/1800Z 13.0N 117.4W 55 KT 65 MPH
48H 03/0600Z 13.4N 118.6W 55 KT 65 MPH
60H 03/1800Z 13.8N 120.1W 55 KT 65 MPH
72H 04/0600Z 14.3N 121.2W 55 KT 65 MPH
96H 05/0600Z 15.3N 122.4W 60 KT 70 MPH
120H 06/0600Z 16.0N 121.4W 60 KT 70 MPH
FORECASTER JELSEMA (CPHC)
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