WDPN31 PGTW 290900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (SURIGAE) WARNING NR 
025//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 29.0N 135.0E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 447 NM SOUTHWEST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY
EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) DISPLACED WEST OF
FLARING DEEP CONVECTION ANCHORED ALONG LOW-LEVEL CONVERGENT 
ASYMPTOTES IN THE EASTERN SEMICIRCLE. A 290245Z AMSR3 COLOR-ENHANCED 
89GHZ MICROWAVE PASS REVEALS THE VORTEX IS SHALLOW AND STRONGLY 
DECOUPLED, WITH DEEP CONVECTIVE CORES RESTRICTED TO THE DOWN-SHEAR 
EASTERN FLANK. SYNOPTICALLY, THE SOUTHWESTERN EXTENT OF A STATIONARY 
FRONTAL BOUNDARY IS LOCATED APPROXIMATELY 175 NM NORTH OF THE LLCC. 
ANIMATED WATER VAPOR IMAGERY AND ATMOSPHERIC MOTION VECTORS (AMVS) 
INDICATE AN UPPER-TROPOSPHERIC JET AXIS OVER HONSHU ORIENTED PARALLEL 
TO THE SURFACE BOUNDARY, IMPOSING MODERATE-TO-STRONG NORTHWESTERLY 
SHEAR DIRECTLY ACROSS TS 25W. THE INITIAL POSITION IS ASSESSED WITH 
HIGH CONFIDENCE BASED ON THE FULLY EXPOSED LLCC IN MSI. THE INITIAL 
INTENSITY IS HELD AT 50 KNOTS, BIASED SLIGHTLY ABOVE OBJECTIVE 
SATELLITE ESTIMATES (ADT/SATCON), BASED ON A BLEND OF DVORAK CURRENT 
INTENSITY (CI) ASSESSMENTS AND RECENT SCATTEROMETER WINDS OF 45 KNOTS 
ACCOUNTING. ENVIRONMENTAL CONDITIONS ARE UNFAVORABLE, CHARACTERIZED 
BY HIGH VWS (20-25 KTS), RESTRICTED UPPER-LEVEL OUTFLOW, AND MID-
LEVEL DRY AIR INTRUSION, MARGINALLY OFFSET BY WARM SEA SURFACE 
TEMPERATURES (SSTS).

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: WESTERN FLANK OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED TO THE EAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T4.5 - 77 KTS
   RCTP: T3.0 - 45 KTS
   CIMSS SATCON: 41 KTS AT 290426Z
   CIMSS ADT: 45 KTS AT 290540Z
   CIMSS AIDT: 43 KTS AT 290540Z
   CIMSS D-MINT: 30 KTS AT 290427Z
   CIMSS D-PRINT: 35 KTS AT 290540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 20-25 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: MID-LEVEL DRY AIR INTRUSION ALONG THE
NORTHWESTERN FLANK OF THE VORTEX. 

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM (TS) 25W WILL CONTINUE TO TRACK
NORTHEASTWARD ALONG THE NORTHWESTERN SIDE OF THE STR TO THE EAST,
RIDING POLEWARD JUST AHEAD OF THE STATIONARY FRONTAL BOUNDARY JUST
OFFSHORE OF HONSHU, THROUGH TAU 48. BETWEEN TAU 36 AND TAU 48, AS THE 
CYCLONE APPROACHES THE LATITUDE OF YOKOSUKA, 25W WILL INTERACT 
DIRECTLY WITH THE BAROCLINIC FRONTAL ZONE, PHASE WITH AN APPROACHING 
POLAR SHORTWAVE TROUGH, AND COMMENCE EXTRATROPICAL TRANSITION (ETT)
ETT IS PROJECTED TO COMPLETE BY TAU 60, AT WHICH POINT THE SYSTEM 
WILL BE RESTRUCTURED AS A COLD-CORE, ASYMMETRIC EXTRATROPICAL CYCLONE 
COUPLED WITHIN THE FAVORABLE DIVERGENT RIGHT-ENTRANCE QUADRANT OF A 
140-KNOT UPPER-LEVEL JET STREAK EAST OF HOKKAIDO. REGARDING 
INTENSITY, 25W WILL SLOWLY WEAKEN OVER THE NEXT 12 HOURS, BUT 
PERIODIC PULSES OF DEEP CONVECTION, FUELED BY THE WARM WATERS OF THE 
KUROSHIO CURRENT, WILL PROVIDE ENOUGH ENERGY TO MAINTAIN THE 
INTENSITY AT 40-45 KNOTS FROM TAU 12 THROUGH TAU 36. AS ETT ENSUES, 
BAROCLINIC CYCLOGENESIS AND UPPER-LEVEL JET DIVERGENCE WILL ARREST 
THE WEAKENING TREND AND INDUCE SECONDARY RE-INTENSIFICATION AS A 
HYBRID/EXTRATROPICAL GALE BY TAU 60.

MODEL DISCUSSION: TRACK GUIDANCE EXHIBITS EXCELLENT CROSS-MODEL
CONSISTENCY. CROSS-TRACK SPREAD REMAINS CONFINED TO LESS THAN 50 NM
THROUGH TAU 48, WIDENING MARGINALLY TO 110 NM BY TAU 60. ECMWF
OCCUPIES THE WESTERN (INNER) PERIPHERY OF THE GUIDANCE ENVELOPE, 
WHILE THE DETERMINISTIC GOOGLE DEEPMIND ANCHORS THE EASTERN EDGE. 
ALONG-TRACK DISPERSION REMAINS MINIMAL THROUGH TAU 24 BEFORE 
INCREASING TO A MAXIMUM OF 250 NM BY TAU 60. IN TERMS OF FORWARD 
ACCELERATION, ECMWF, ECEPS MEAN, AND GALWEM REPRESENT THE FAST 
BOUNDARY, WHEREAS NAVGEM AND GEFS MEAN ARE THE SLOWER OUTLIERS. THE 
JTWC FORECAST IS POSITIONED ALONG THE SOUTHEASTERN BOUNDARY OF THE 
ENVELOPE, CLOSELY ALIGNED WITH THE DEEPMIND ENSEMBLE MEAN WITH HIGH 
CONFIDENCE. INTENSITY GUIDANCE IS IN GOOD AGREEMENT REGARDING A 
GRADUAL DECAY THROUGH TAU 36-48, FOLLOWED BY DYNAMICAL RE-
INTENSIFICATION DRIVEN BY BAROCLINIC CONVERSION DURING ETT. 
STATISTICAL DECAY-SHIPS GUIDANCE (BOTH VERSIONS) DEPICTS UNREALISTIC 
PERSISTENT DISSIPATION DOWN TO 15 KNOTS BY TAU 48, DISCOUNTED AS 
UNLIKELY GIVEN ITS INABILITY TO RESOLVE MID-LATITUDE BAROCLINIC RE-
DEVELOPMENT. MESOSCALE DYNAMICAL AND AI AIDS (HAFS-A, CTCX, AND 
DEEPMIND) CONCUR ON AN INTENSITY MINIMUM OF 35-40 KNOTS NEAR TAU 36, 
FOLLOWED BY A SECONDARY EXTRATROPICAL PEAK OF 40-55 KNOTS BY TAU 60. 
THE JTWC FORECAST TRACKS THE HAFS-A/CTCX CONSENSUS CLOSELY WITH HIGH 
CONFIDENCE. 

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