102
WTPZ45 KNHC 302044
TCDEP5
TROPICAL STORM OCTAVE DISCUSSION NUMBER 3
NWS NATIONAL HURRICANE CENTER MIAMI FL EP152025
200 PM MST TUE SEP 30 2025
OCTAVE CONTINUES TO BECOME A LITTLE BETTER ORGANIZED THIS AFTERNOON,
WITH CURVED BANDS FORMING PRIMARILY ALONG THE SOUTHWESTERN SIDE OF
THE SMALL CYCLONE. THE WIND FIELD APPEARS SO SMALL THAT
SCATTEROMETER DATA LARGELY MISSED THE SMALL CIRCULATION IN THE
NARROW 100 N MI GAP BETWEEN PASSES. THE LATEST SUBJECTIVE DVORAK
INTENSITY ESTIMATES WERE T3.0/45 KT FROM SAB, AND T2.5/35 KT FROM
TAFB. THE INITIAL INTENSITY IS RAISED TO 40 KT THIS ADVISORY, A
BLEND OF THE TWO ESTIMATES, AND NEAR THE LATEST ADT ESTIMATE OF
T2.8/41 KT AND D-PRINT ESTIMATE OF 40 KT.
OCTAVE IS STILL MOVING NORTHWESTWARD, WITH THE LATEST MOTION
ESTIMATED AT 320/4 KT. A TURN MORE TO THE NORTH-NORTHWEST IS
ANTICIPATED OVER THE NEXT DAY OR SO AS OCTAVE INTERACTS WITH THE
REMNANT LOW-LEVEL VORTICITY OF ANOTHER SMALL DISTURBANCE THAT IS
PASSING THE SYSTEM BY TO THE NORTH. MOST OF THE GUIDANCE SHOWS
OCTAVE QUICKLY ABSORBING THE WEAKER SYSTEM, AND AFTER THAT IS
COMPLETE, LOW TO MID-LEVEL RIDGING BUILDS BACK IN, RESULTING IN THE
CYCLONE TURNING BACK WEST-NORTHWESTWARD FROM 36-72 H. TOWARDS THE
END OF THE FORECAST, STEERING CURRENTS ARE EXPECTED TO COLLAPSE AS A
LONGWAVE TROUGH ERODES THE MID-LEVEL RIDGING AND LOW-LEVEL MONSOONAL
FLOW BECOMES MORE ESTABLISHED TO THE EAST OF OCTAVE. COMPARED TO THE
PREVIOUS CYCLE, THE TRACK GUIDANCE HAS TRENDED WESTWARD, AND THE NHC
TRACK FORECAST HAS BEEN SHIFTED A LITTLE FARTHER WEST EARLY ON, BUT
MORE SUBSTANTIALLY BY THE END OF THE FORECAST PERIOD, THOUGH IT
REMAINS EAST OF THE LATEST HCCA AND GOOGLE DEEPMIND ENSEMBLE MEAN
(GDMI).
THE TROPICAL STORM HAS BEEN ABLE TO INTENSIFY A LITTLE TODAY DESPITE
BEING UNDER 20-25 KT OF EAST-NORTHEASTERLY VERTICAL WIND SHEAR. THIS
SHEAR IS EXPECTED TO PERSIST FOR THE NEXT 36-48 HOURS, AND THUS ONLY
A SLIGHT BIT OF ADDITIONAL INTENSIFICATION IS EXPECTED TONIGHT
FOLLOWED BY A PAUSE IN STRENGTHENING. AFTER 60 H, SHEAR IS EXPECTED
TO DECREASE TO 10-15 KT, AND HOW MUCH THE STORM IS ABLE TO INTENSIFY
WILL BE RELATED TO ITS STRUCTURAL CHARACTERISTICS. OCTAVE IS
EXPECTED TO REMAIN A SMALL TROPICAL CYCLONE, SO ITS POSSIBLE IT
COULD BE PRONE TO MORE RAPID INTENSITY CHANGES (BOTH UP OR DOWN)
THAN SHOWN HERE. FOR NOW, THE INTENSITY WAS BUMPED UP A LITTLE
TOWARDS THE END OF THE FORECAST PERIOD, BUT REMAINS MUCH LOWER THAN
SOME OF THE MORE AGGRESSIVE HURRICANE-REGIONAL MODEL GUIDANCE (HWRF,
HAFS-A) WHICH DEVELOP AN INNER CORE WITH OCTAVE MUCH SOONER THAN THE
REMAINDER OF THE GUIDANCE. THE NHC INTENSITY FORECAST IS CLOSEST TO
THE HFIP CORRECTED CONSENSUS APPROACH (HCCA).
FORECAST POSITIONS AND MAX WINDS
INIT 30/2100Z 10.2N 113.9W 40 KT 45 MPH
12H 01/0600Z 10.8N 114.0W 45 KT 50 MPH
24H 01/1800Z 12.0N 114.5W 45 KT 50 MPH
36H 02/0600Z 12.6N 115.3W 45 KT 50 MPH
48H 02/1800Z 13.0N 116.6W 45 KT 50 MPH
60H 03/0600Z 13.6N 117.9W 45 KT 50 MPH
72H 03/1800Z 14.0N 119.3W 50 KT 60 MPH
96H 04/1800Z 14.5N 120.7W 55 KT 65 MPH
120H 05/1800Z 15.5N 121.0W 55 KT 65 MPH
FORECASTER PAPIN
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