Advisories

WDPN31 PGTW 300300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (SURIGAE) WARNING NR 
028//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 30.2N 137.3E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 329 NM SOUTH-SOUTHWEST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A
WELL-DEFINED SWIRL OF LOW- TO MID-LEVEL CLOUDS AND CONVECTION
CONFINED TO THE SOUTHEAST QUADRANT. A JET STREAM POSITIONED OVER
THE SEA OF JAPAN IS GENERATING MODERATE TO HIGH VERTICAL WIND SHEAR
(VWS), WHICH IS ENTRAINING DRY AIR INTO THE CIRCULATION AND
RESTRICTING CONVECTIVE ACTIVITY. THEREFORE, THESE CONDITIONS
REPRESENT AN ENVIRONMENT UNFAVORABLE FOR INTENSIFICATION. AS THE
SHALLOW CIRCULATION PASSES SOUTH OF HONSHU, A BELT OF EASTERLY
WINDS OF 25-30 KTS HAS DEVELOPED PARALLEL TO THE SOUTHERN COAST OF
HONSHU AND OFFSHORE, IN RESPONSE TO A TIGHTENED PRESSURE GRADIENT.
A 291949Z SSMIS 37 GHZ IMAGE INDICATES THAT THE HIGHEST BRIGHTNESS
TEMPERATURES ARE ALONG THE SOUTHEASTERN PORTION OF THE LOW-LEVEL
CIRCULATION, WHICH MAY CORRESPOND TO THE STRONGEST NEAR-SURFACE
WINDS. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON
THE EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC). THE INITIAL
INTENSITY HAS BEEN LOWERED TO 35 KTS WITH MEDIUM CONFIDENCE BASED
ON FALLING SUBJECTIVE AND OBJECTIVE ESTIMATES, REFLECTING THE
CONTINUED SPIN-DOWN OF TS 25W.

INITIAL WIND RADII BASIS: PERSISTENCE

CURRENT STEERING MECHANISM: NORTHWESTERN FLANK OF A LOW- TO
MID-LEVEL SUBTROPICAL RIDGE (STR) POSITIONED EAST OF HONSHU

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T2.5 - 35 KTS
   CIMSS SATCON: 33 KTS AT 300040Z
   CIMSS ADT: 29 KTS AT 292340Z
   CIMSS AIDT: 35 KTS AT 292340Z
   CIMSS D-MINT: 28 KTS AT 291949Z
   CIMSS D-PRINT: 28 KTS AT 292340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 20-25 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TS 25W HAS MADE THE ANTICIPATED TURN FROM THE
EAST-NORTHEAST TO THE NORTHEAST WITH A FORWARD SPEED OF 7-8 KTS,
STEERED ALONG THE NORTHWESTERN PERIPHERY OF A LOW- TO MID-LEVEL STR
CENTERED NEAR 33N 165E. THIS MOTION WILL PERSIST FOR THE NEXT 12
HOURS. AFTER THAT TIME, THE SYSTEM WILL BECOME INCREASINGLY
EMBEDDED WITHIN DEEP-LAYER WESTERLY FLOW, GRADUALLY TURNING TOWARD
THE EAST-NORTHEAST AND ACCELERATING. THE INTENSITY FORECAST HOLDS
TS 25W NEAR 35 KTS THROUGH TAU 24. THE WEAK CONVECTION WITHIN THE
SOUTHERN SEMICIRCLE MAY BE SUFFICIENT TO SUSTAIN THIS INTENSITY.
HOWEVER, A LOWER-END SCENARIO IN WHICH TS 25W WEAKENS INTO A
TROPICAL DEPRESSION DURING THIS PERIOD REMAINS POSSIBLE. AFTER TAU
12, THE SYSTEM WILL BEGIN EXTRATROPICAL TRANSITION AS THERMAL
ADVECTION INCREASES AND THE SYSTEM INTERACTS WITH A MID-LEVEL
TROUGH PASSING OVER HONSHU. THE FORECAST CALLS FOR SLIGHT
BAROCLINIC REINTENSIFICATION TO 40 KTS AT TAU 36 DUE TO STRONGER
BAROCLINIC FORCING AND PARTIAL PHASING WITH A JET STREAK.

MODEL DISCUSSION: MODEL GUIDANCE IS IN TIGHT AGREEMENT THROUGH TAU
36. THE CROSS-TRACK SPREAD AT TAU 24 IS 50 NM, AND THE ALONG-TRACK
SPREAD CONTINUES TO NARROW. GFS AND THE GEFS ENSEMBLE MEAN ARE THE
MOST POLEWARD TRACK SOLUTIONS, WHILE ECMWF AND THE AI MODELS MAKE
UP THE EQUATORWARD SIDE OF THE GUIDANCE ENVELOPE. THE JTWC FORECAST
TRACK IS PLACED NEAR THE AI CONSENSUS WITH HIGH CONFIDENCE. THE
RELIABLE INTENSITY AIDS GENERALLY DEPICT A STEADY INTENSITY THROUGH
TAU 24, FOLLOWED BY SLIGHT INTENSIFICATION AT TAU 36. THE JTWC
INTENSITY FORECAST IS UNCHANGED FROM THE PREVIOUS CYCLE, SHOWING
SLIGHT REINTENSIFICATION TO 40 KTS AT TAU 36.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: HIGH//
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