Advisories

WDPN31 PGTW 160900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 24W (TWENTYFOUR) 
WARNING NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.4N 148.9E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 277 NM EAST-NORTHEAST OF NAVSTA GUAM
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) REVEALS TROPICAL 
DEPRESSION (TD) 24W EXHIBITING A MORE ORGANIZED AND INCREASINGLY 
SYMMETRIC LOW-LEVEL CIRCULATION CENTER (LLCC). SPIRAL BANDS OF DEEP 
CONVECTION CAN BE SEEN WRAPPING TIGHTLY INTO THE CORE, EVEN WITHIN THE 
DRIER, NORTHWESTERN PART OF THE CIRCULATION FIELD. THE INITIAL 
POSITION 
IS PLACED WITH HIGH CONFIDENCE BASED ON THE ANIMATED VISIBLE SATELLITE 
IMAGERY OF THE LLCC. ENVIRONMENTAL ANALYSIS REVEALS MARGINALLY 
FAVORABLE CONDITIONS - WARM (29-30 C) SEA SURFACE TEMPERATURES (SST), 
ROBUST POLEWARD AND EQUATORWARD OUTFLOW CHANNELS, AND LOW (0-5 KTS) 
VERTICAL WIND SHEAR (VWS), OFFSET BY THE CONTINUOUS ADVECTION OF DRIER 
TROPOSPHERIC AIR TO THE NORTHWEST. THE INITIAL INTENSITY OF 30 KTS IS 
ASSESSED WITH HIGH CONFIDENCE BASED ON A COMBINATION OF CONSISTENT 
DVORAK AND OBJECTIVE ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: NORTHWARD EXTENSION OF AN ELONGATED
NEAR EQUATORIAL RIDGE (NER) CENTERED TO THE SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   CIMSS SATCON: 37 KTS AT 160530Z
   CIMSS ADT: 33 KTS AT 160530Z
   CIMSS AIDT: 34 KTS AT 160530Z
   CIMSS D-MINT: 38 KTS AT 160326Z
   CIMSS D-PRINT: 43 KTS AT 160600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT FROM THE NORTHWEST

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TD 24W IS CURRENTLY TRACKING NORTH-NORTHEASTWARD 
UNDER THE INFLUENCE OF THE ELONGATED NEAR-EQUATORIAL RIDGE (NER) 
ANCHORED TO THE SOUTHEAST. THE CO-LOCATED SUBTROPICAL RIDGE (STR) TO 
THE NORTHEAST IS EXPECTED TO REORIENT EASTWARD AND WEAKEN UNDER THE 
INFLUENCE OF AN UPPER-LEVEL TROUGH APPROACHING FROM THE WEST. AS SUCH, 
THE SYSTEM IS FORECAST TO TRACK NORTH FOR THE NEXT 12-18 HOURS. AFTER 
THAT, THE SYSTEM WILL BE STEERED BY A BUILDING SOUTHWESTERN FLANK OF 
THE STR DEFLECTING THE TRAJECTORY NORTHWESTWARD THROUGH TAU 72. BEYOND 
TAU 72, TD 24W WILL SLOWLY ROUND THE WESTERN EXTENT OF THE RIDGE AXIS, 
FOLLOWED BY A NORTHEASTWARD ACCELERATION CLOSE TO THE EASTERN 
COASTLINE 
OF HONSHU, JAPAN. UNCERTAINTY IN THE TRACK REMAINS MODERATE, DRIVEN 
PRIMARILY BY THE TIMELINE OF THE RECURVATURE MOTION. IN TURN, THE 
TRACK 
OF THE SYSTEM AND ITS PROXIMITY TO MAINLAND JAPAN WILL BE HEAVILY 
INFLUENCED BY THE HAND OFF BETWEEN THE TWO STEERING MECHANISMS. IN 
TERMS OF INTENSITY, THE SYSTEM IS EXPECTED TO SLOWLY DEVELOP DRIVEN BY 
A GENERALLY FAVORABLE ENVIRONMENT. BETWEEN TAUS 24 AND 36, THE 
INTENSIFICATION IS EXPECTED TO BRIEFLY STALL, AS THE DRY AIR 
ENTRAINMENT BECOMES MORE SIGNIFICANT, THE OUTFLOW BECOMES LESS 
PRONOUNCED, AND THE STEERING TRANSITION OCCURS. AFTERWARDS, TD 24W IS 
EXPECTED TO REACH 65-70 KTS AROUND TAU 96. SOON AFTER, MODEL GUIDANCE 
INDICATES DRY AIR WRAPPING NEARLY FULLY AROUND THE SYSTEM, HALTING ANY 
SIGNIFICANT DEVELOPMENT. VWS IS ALSO EXPECTED TO BEGIN INCREASING 
AROUND TAU 72, QUICKLY REACHING 15-20 KTS. TD 24W WILL HOWEVER GAIN 
ACCESS TO A NEWLY OPENED POLEWARD CHANNEL AS IT APPROACHES THE JET 
STREAK OVER JAPAN, OFFSETTING THE OTHERWISE UNFAVORABLE CONDITIONS.

MODEL DISCUSSION: NUMERICAL WEATHER PREDICTION TRACK GUIDANCE REMAINS 
IN MODERATE AGREEMENT THROUGHOUT THE CURRENT FORECAST PERIOD AS 
WITNESSED BY A 180 NM CROSS-TRACK SPREAD AT TAU 24, EXPANDING TO A 260 
NM SPREAD AT THE AXIS OF RECURVATURE SHORTLY AFTER TAU 96. THE 
OFFICIAL 
JTWC TRACK IS POSITIONED ON THE EASTERN SIDE OF THE MULTI-MODEL 
CONSENSUS, LEANING TOWARDS THE EXPERIMENTAL AI GUIDANCE (GOOGLE 
DEEPMIND AND EC-AIFS). INTENSITY GUIDANCE EXHIBITS GENERALLY MODERATE 
CONSENSUS REGARDING STEADY CONSOLIDATION THROUGH TAU 72-96, 
TRANSITIONING TO AN INTENSITY PLATEAU AFTERWARDS. COAMPS-TC AND HWRF 
REMAIN THE PRIMARY OUTLIERS INDICATING 75-85 KTS PEAK INTENSITY, 
DRIVEN 
PRIMARILY BY A MUCH SLOWER ASSOCIATED TRACK PREDICTION AND MORE TIME 
OVER WARM WATERS. THE REMAINING MODELS INDICATE MAXIMUM WIND SPEEDS 
BETWEEN 55 AND 70 KTS. THE OFFICIAL JTWC INTENSITY FORECAST REMAINS 
ALIGNED CLOSELY WITH THE MULTI-MODEL DYNAMICAL CONSENSUS WITH MEDIUM 
CONFIDENCE.

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