Advisories

WDPN31 PGTW 240300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (SURIGAE) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.2N 134.3E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 556 NM SOUTHWEST OF IWO TO
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM (TS) 25W HAS STRUGGLED TO BECOME BETTER ORGANIZED
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
(MSI) DEPICTS A PARTIALLY EXPOSED, ASYMMETRIC LOW-LEVEL CIRCULATION
CENTER (LLCC) WITH DEEP CONVECTION AND THE ASSOCIATED MID-LEVEL
CIRCULATION DISPLACED TO THE NORTHWEST. A 232220Z SSMIS PASS
CONFIRMS THE ASYMMETRIC, TILTED NATURE OF THE VORTEX. THE RECENT
LACK OF DEVELOPMENT IS THE RESULT OF MODERATE MID-LEVEL SHEAR,
WHICH IS ENTRAINING DRY AIR FROM THE SOUTHWEST INTO THE
CIRCULATION. DESPITE THIS INHIBITING FACTOR, THE ENVIRONMENT IS
FAVORABLE FOR CONTINUED DEVELOPMENT, CHARACTERIZED BY VERY WARM SEA
SURFACE TEMPERATURES (SST) AND MODERATE POLEWARD OUTFLOW ALOFT. THE
INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE
SSMIS MICROWAVE DATA. THE INITIAL INTENSITY HAS BEEN HELD AT 35 KTS
WITH MEDIUM CONFIDENCE BASED ON THE SUBJECTIVE AND OBJECTIVE
SATELLITE ESTIMATES RANGING FROM 33 KTS TO 41 KTS.

INITIAL WIND RADII BASIS: PERSISTENCE

CURRENT STEERING MECHANISM: SOUTHWESTERN FLANK OF A LOW- TO
MID-LEVEL SUBTROPICAL RIDGE (STR) CENTERED SOUTH OF HONSHU

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.5 - 35 KTS
   CIMSS ADT: 41 KTS AT 232340Z
   CIMSS AIDT: 37 KTS AT 232340Z
   CIMSS D-MINT: 33 KTS AT 232220Z
   CIMSS D-PRINT: 33 KTS AT 232340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE FORECAST RECURVATURE HAS BEEN
ADJUSTED TO OCCUR MUCH MORE QUICKLY, WITH THE CPA FOR THE SOUTHERN
RYUKYU ISLANDS, INCLUDING OKINAWA, NOW TAKING PLACE BETWEEN TAU 96
AND TAU 120.

FORECAST DISCUSSION: TS 25W WILL CONTINUE ON A NORTHWESTWARD
TRAJECTORY ON THE SOUTHWESTERN PERIPHERY OF THE STR TO THE NORTH.
THIS MOTION WILL CONTINUE UNTIL TAU 48, WHEN THE VORTEX WILL BEGIN
TO ROUND THE STR. AFTER TAU 72, THE SYSTEM WILL ACCELERATE TO THE
NORTHEAST ALONG THE NORTHWESTERN FLANK OF THE DEEP-LAYER RIDGE.
INTENSIFICATION WILL BE SLOW FOR THE FIRST 24 HOURS, IN LARGE PART
DUE TO THE HIGHLY ASYMMETRIC NATURE OF THE CIRCULATION. ONCE TS 25W
ESTABLISHES AN INNER CORE, IT WILL INTENSIFY MORE RAPIDLY. THE
SYSTEM WILL TRAVEL THROUGH FAVORABLE ENVIRONMENTAL CONDITIONS
THROUGH TAU 60, CONSISTING OF VERY WARM SST, MODERATE POLEWARD
DIVERGENCE ALOFT, AND LOW TO MODERATE MID-LEVEL SHEAR. DEEP-LAYER
SHEAR WILL BEGIN TO INCREASE MARKEDLY AS THE SYSTEM ROUNDS THE
RIDGE AXIS AT TAU 72, WHICH WILL CAUSE THE SYSTEM TO STEADILY
WEAKEN AS IT MAKES A CLOSE APPROACH TO OKINAWA AND ACCELERATES
NORTHEASTWARD.

MODEL DISCUSSION: WHILE THE CROSS-TRACK SPREAD AMONG THE TRACKER
GUIDANCE IS LOW THROUGH TAU 48, THE ALONG-TRACK SPREAD THEN
INCREASES SIGNIFICANTLY. THE ALONG-TRACK SPREAD INCREASES FROM 180
NM AT TAU 60 TO 300 NM AT TAU 96. THIS SUBSTANTIAL SPREAD IS
GOVERNED BY MAJOR DIFFERENCES BETWEEN THE DYNAMICAL SOLUTIONS AND
THE AI-BASED MODEL OUTPUT. WHILE THE GREAT MAJORITY OF THE
PHYSICS-BASED MODELS HAVE SHIFTED FROM A STRAIGHT TRACK INTO TAIWAN
TO A RECURVATURE SCENARIO, THEY REMAIN MUCH SLOWER THAN THE
AI-BASED MODELS. THE AI MODELS ARE ALSO IN GOOD AGREEMENT AMONG
EACH OTHER IN DEPICTING A STRONGER AND FASTER RECURVATURE, WHILE
THE PHYSICS-BASED MODELS ARE MORE SPREAD OUT. THE JTWC FORECAST
TRACK HAS BEEN SIGNIFICANTLY ADJUSTED TO INCLUDE THE INCREASING
PROBABILITY THAT THE AI-BASED SOLUTIONS VERIFY. THEREFORE, THE JTWC
FORECAST TRACK IS NOW BASED ON A BLEND OF THE JTWC CONSENSUS
(CONW), WHICH INCORPORATES STATISTICAL AND DYNAMICAL MODELS, AND
THE CONSENSUS OF AI MODELS. THIS BLEND RESULTS IN A MUCH FASTER
TRACK THAN DEPICTED IN PREVIOUS FORECASTS. IT IS QUITE POSSIBLE
THAT FUTURE FORECASTS MAY NEED TO SHOW AN EVEN FASTER STORM MOTION,
WHICH WOULD ADVANCE THE TIME OF CLOSEST APPROACH TO OKINAWA. IN THE
PAST SEVERAL MODEL RUNS, THE AI SOLUTIONS HAVE GRADUALLY SHIFTED
WESTWARD. THEREFORE, THE JTWC FORECAST TRACK POSITIONS AT TAU 96
AND TAU 120 ARE PLACED WEST OF THE AI CONSENSUS. THE VARIANCE BETWEEN 
THE AI- AND PHYSICS-BASED SOLUTIONS IS EVIDENT IN THE INTENSITY 
GUIDANCE. THE RELIABLE PHYSICS-BASED AIDS, SUCH AS HAFS-A AND COAMPS-
TC, DEPICT A MUCH LATER AND HIGHER PEAK INTENSITY OF UP TO 135 KTS 
BETWEEN TAU 72 AND TAU 96, BECAUSE THEY DEPICT A SLOWER-MOVING SYSTEM 
ABLE TO TAP INTO THE FAVORABLE ENVIRONMENT FOR A LONGER PERIOD OF TIME. 
THE EXPERIMENTAL GOOGLE DEEPMIND SOLUTION PREDICTS A MUCH EARLIER, 
LOWER PEAK INTENSITY OF 90 KTS AT TAU 60. THE JTWC FORECAST, WHICH IS A 
BLEND OF THE DYNAMICAL AND AI-BASED SOLUTIONS, DEPICTS A PEAK INTENSITY 
OF 95 KTS AT TAU 72. GIVEN THE LARGE DISCREPANCIES AMONG THE GUIDANCE 
SUITE, BOTH THE TRACK AND INTENSITY FORECASTS ARE SET WITH LOW 
CONFIDENCE AFTER TAU 72.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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