WDPN32 PGTW 030300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 13W (BAILU) WARNING NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 33.3N 141.8E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 159 NM SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 25 KTS
   SIGNIFICANT WAVE HEIGHT: 19 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS THE
LOW-LEVEL CIRCULATION CENTER (LLCC) OF TROPICAL STORM (TS) 13W
(BAILU) STILL STRUGGLING TO CONSOLIDATE. THE SYSTEM EXHIBITS A
MARKEDLY ASYMMETRIC STRUCTURE, WITH MULTIPLE MESOVORTICES
IDENTIFIED WITHIN THE BROADER CIRCULATION. A 022330 METOP-B ASCAT
PASS INDICATES THAT THE STRUCTURE IS PHASING TOWARD A PRIMARY
VORTEX, SUPPORTED BY INTERMITTENT DEEP CONVECTIVE BURSTS ALONG THE
OUTER CORE, HOWEVER WITH THE SYSTEM APPROACHING MORE HOSTILE
ENVIRONMENT THE TIME AVAILABLE FOR INTENSIFICATION IS LIMITED. AT THE
MOMENT, TS 13W IS SITUATED WITHIN A MARGINALLY CONDUCIVE SYNOPTIC
ENVIRONMENT, CHARACTERIZED BY AVAILABLE ATMOSPHERIC MOISTURE, SEA
SURFACE TEMPERATURES (SST) RANGING FROM 27 TO 28 C, ASSOCIATED WITH
THE KUROSHIO CURRENT, LOW (5-10 KTS) VERTICAL WIND SHEAR (VWS), AND
MODERATE POLEWARD OUTFLOW ALOFT. KEY INHIBITING FACTORS INCLUDE
PERSISTENT LOW-LEVEL VORTEX TILT AND EXTENSIVE DRY MID- TO
UPPER-TROPOSPHERIC AIR ADVECTING FROM THE WEST. THE INITIAL
POSITION IS ESTABLISHED WITH HIGH CONFIDENCE VIA ANIMATED SHORTWAVE
INFRARED AND VISIBLE IMAGERY LOOPS, CORROBORATED BY THE
AFOREMENTIONED ASCAT PASS. THE INITIAL INTENSITY ESTIMATE OF 35 KTS
IS ALSO ASSIGNED WITH HIGH CONFIDENCE, BASED ON THE SAME
SCATTEROMETER PASS, AS WELL AS AGENCY DVORAK FIXES AND AUTOMATED
INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: A 022330 METOP-B ASCAT PASS

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR) TO
THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T1.5 - 25 KTS
   RCTP: T1.5 - 25 KTS
   KNES: T2.0 - 30 KTS
   CIMSS SATCON: 44 KTS AT 030000Z
   CIMSS ADT: 31 KTS AT 022040Z
   CIMSS AIDT: 40 KTS AT 022040Z
   CIMSS D-PRINT: 29 KTS AT 030140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 5-10 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: DRY AIR TO THE WEST

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 13W IS ANTICIPATED TO TRACK GENERALLY
NORTHWESTWARD ALONG THE NORTHWESTERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR) ANCHORED TO THE EAST THROUGH THE NEXT 36 HOURS. DURING
THIS TIMEFRAME, THE ENVIRONMENT IS FORECAST TO REMAIN MARGINAL,
SUPPORTING SLIGHT INTENSIFICATION OR MAINTAINED INTENSITY. VERTICAL
ALIGNMENT AND CORE CONSOLIDATION HOWEVER WILL REMAIN CHALLENGING.
BETWEEN TAUS 36 AND 48, THE FORWARD MOTION IS EXPECTED TO
DECELERATE SLIGHTLY AS THE STEERING RIDGE WEAKENS. BEYOND TAU 48,
TS BAILU IS LIKELY TO BEGIN A POLEWARD RECURVATURE IN RESPONSE TO A
SECONDARY STR BUILDING AND EXPANDING FROM THE SOUTHEAST. DURING
THIS PERIOD, THE COMBINATION OF COOLER SSTS AND INCREASING
MID-LEVEL DRY AIR ADVECTION WILL INITIATE A WEAKENING TREND,
COINCIDING WITH THE ONSET OF EXTRATROPICAL TRANSITION (ETT). TS 13W
IS EXPECTED TO COMPLETE ETT BY TAU 96.

MODEL DISCUSSION: NUMERICAL TRACK GUIDANCE EXHIBITS GOOD
CONSISTENCY THROUGH TAU 72, WITH ALL CONSENSUS MEMBERS AGREEING ON
THE SYNOPTIC STEERING SCENARIO. THE CROSS-TRACK SPREAD AT TAU 24 IS
APPROXIMATED AT 55 NM, INCREASING TO NEARLY 140 NM BY TAU 72 DUE TO
A BRIEF BREAK IN STEERING INFLUENCES. THE JTWC INTENSITY FORECAST
IS ASSESSED WITH HIGH INITIAL CONFIDENCE, AS ALL CONSENSUS MEMBERS
INDICATE MAINTAINED INTENSITY THROUGH TAU 60. THE ONLY CONTRASTING
EXCEPTION IS NAVGEM-DRIVEN COAMPS-TC WHICH PROJECTS EARLY
WEAKENING. LONG TERM INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE
GIVEN THE DIVERGENCE IN MODEL OUTPUTS. DETERMINISTIC GFS MAINTAINS
A FLAT INTENSITY PROFILE, WITH AN INCREASE TO 45 KTS AROUND TAU 72.
MEANWHILE ALL OTHER MODELS, INCLUDING THE CONSENSUS MEMBER MEAN
INDICATE CONTINUOUS WEAKENING THROUGH THE END OF THE FORECAST
PERIOD. OFFICIAL JTWC INTENSITY FORECAST TRACKS CLOSELY TO THE
MULTI-MODEL CONSENSUS MEAN AND AIMS TO STRIKE A BALANCE BETWEEN THE
DIVERGENT SOLUTIONS.

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