819
WTPZ45 KNHC 301444
TCDEP5
TROPICAL STORM OCTAVE DISCUSSION NUMBER 2
NWS NATIONAL HURRICANE CENTER MIAMI FL EP152025
800 AM MST TUE SEP 30 2025
THE CONVECTIVE STRUCTURE OF THE DEPRESSION HAS CONTINUED TO IMPROVE
THIS MORNING, WITH COLD CLOUD TOPS (-80C CMG) DEVELOPING OVER THE
SURFACE CENTER, AND A DEEP CONVECTIVE CURVED BAND LOCATED IN THE
EAST SEMICIRCLE OF THE CYCLONE. SUBJECTIVE DVORAK INTENSITY
ESTIMATES FROM TAFB AND SAB ARE T2.0 AND T3.0, AND THE UW-CIMSS
OBJECTIVE INTENSITY ANALYSES RANGE FROM 34-39 KT. BASED ON A BLEND
OF THESE DATA AND THE CYCLONE'S IMPROVED SATELLITE PRESENTATION, THE
INITIAL INTENSITY IS RAISED TO 35 KT, UPGRADING TROPICAL DEPRESSION
FIFTEEN-E TO TROPICAL STORM OCTAVE.
ALTHOUGH OCTAVE SHOULD REMAIN OVER WARM OCEANIC SURFACE
TEMPERATURES, AND MOVE WITHIN A SURROUNDING ENVIRONMENT WITH AMPLE
LOW- TO MID-LEVEL MOISTURE, MODERATE DEEP-LAYER EAST-NORTHEASTERLY
SHEAR IS EXPECTED TO HAMPER SIGNIFICANT DEVELOPMENT. ACCORDINGLY,
THE FORECAST REFLECTS LITTLE CHANGE IN STRENGTH THROUGH THURSDAY.
AFTERWARD, THE STATISTICAL DECAY-SHIPS INTENSITY GUIDANCE AND THE
GLOBAL MODELS INDICATE THAT THE SHEAR WILL DIMINISH SOME, ALLOWING
FOR SOME ADDITIONAL INTENSIFICATION THROUGH DAY 5, AND THE INTENSITY
FORECAST FOLLOWS SUIT.
OCTAVE'S INITIAL MOTION IS ESTIMATED TO BE NORTHWESTWARD, OR
325/4 KT. THE CYCLONE IS FORECAST TO TURN NORTH-NORTHWESTWARD TO
NORTHWARD LATER TODAY IN RESPONSE TO A MID-TROPOSPHERIC CUT-OFF
LOW DRIFTING SOUTHWARD TOWARD OCTAVE. BEYOND THE 60 HOUR PERIOD,
MODEL GUIDANCE INDICATES THAT A SUBTROPICAL RIDGE WILL BUILD TO THE
NORTH OF THE CYCLONE AND INDUCE A WEST-NORTHWESTWARD MOTION THROUGH
SATURDAY, WHILE THE CUT-OFF MENTIONED ABOVE WEAKENS AND ULTIMATELY
DISSIPATES. BY DAY 5, THE GLOBAL MODELS AGREE THAT OCTAVE WILL
SLOW IN FORWARD SPEED AND GRADUALLY TURN TOWARD THE NORTHWEST AND
NORTH-NORTHWEST, WHILE THE RIDGE TO THE NORTH OF THE CYCLONE ERODES.
THE NHC FORECAST LIES CLOSE TO THE VARIOUS CONSENSUS AIDS AND HAS
BEEN SHIFTED A BIT TO THE RIGHT OF THE PREVIOUS FORECAST AFTER 36
HOURS.
FORECAST POSITIONS AND MAX WINDS
INIT 30/1500Z 9.9N 113.5W 35 KT 40 MPH
12H 01/0000Z 10.4N 113.7W 35 KT 40 MPH
24H 01/1200Z 11.3N 114.0W 40 KT 45 MPH
36H 02/0000Z 12.3N 114.3W 40 KT 45 MPH
48H 02/1200Z 12.9N 115.2W 40 KT 45 MPH
60H 03/0000Z 13.4N 116.3W 40 KT 45 MPH
72H 03/1200Z 13.8N 117.5W 45 KT 50 MPH
96H 04/1200Z 14.6N 119.5W 45 KT 50 MPH
120H 05/1200Z 15.6N 119.8W 50 KT 60 MPH
FORECASTER ROBERTS
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