Advisories

WDPN31 PGTW 162100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (DUJUAN) WARNING NR 
006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.6N 149.7E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 363 NM NORTHEAST OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM (TS) 24W IS STEADILY INTENSIFYING. ANIMATED ENHANCED
INFRARED (EIR) SATELLITE IMAGERY DEPICTS A CONSOLIDATING CONVECTIVE
STRUCTURE CHARACTERIZED BY A SMALL CENTRAL DENSE OVERCAST,
INCREASED OUTER BANDING, AND EXPANDING OUTFLOW ALOFT. OVERSHOOTING
CLOUD TOPS AS COLD AS -90 DEGREES CELSIUS HAVE BEEN ESTIMATED NEAR
THE CENTER. A 161442Z GMI 89 GHZ MICROWAVE IMAGE DEPICTS A COMPACT,
NASCENT INNER CORE, WITH A PARTIAL RING OF DEEP CONVECTION THAT IS
MOST DEVELOPED IN THE SOUTHWEST QUADRANT. WHILE CONVECTION AND
OUTFLOW ALONG THE NORTHWESTERN PERIPHERY HAVE BEEN SUPPRESSED DUE
TO AN UPPER-LEVEL TROUGH NEAR THE FAR NORTHERN MARIANA ISLANDS, THE
OVERALL ENVIRONMENT IS FAVORABLE, WITH VERY WARM SEA SURFACE
TEMPERATURES (SST) OF 29-30 DEGREES CELSIUS AND LOW VERTICAL WIND
SHEAR (VWS). THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE
NEAR THE FORMATIVE MID-LEVEL CIRCULATION CENTER. THE FIVE MOST
RECENT D-MINT ESTIMATES BETWEEN 1253Z AND 1557Z SPANNED 40-47 KTS,
AND ADT, AIDT, AND D-PRINT ARE APPROACHING 40 KTS. BASED ON THE
INCREASING OBJECTIVE ESTIMATES FROM CIMSS AND THE IMPROVED
CONVECTIVE SIGNATURE, THE INITIAL INTENSITY HAS BEEN RAISED TO 40
KTS WITH MEDIUM CONFIDENCE. THIS ASSESSMENT MAY BE CONSERVATIVE,
GIVEN THAT SUBJECTIVE AND OBJECTIVE ESTIMATES ARE PRONE TO BIAS LOW
FOR COMPACT SYSTEMS.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: SOUTHERN EXTENSION OF THE LOW- TO
MID-LEVEL SUBTROPICAL RIDGE CENTERED NEAR 37N 165E

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.5 - 35 KTS
   CIMSS SATCON: 38 KTS AT 161556Z
   CIMSS ADT: 39 KTS AT 161730Z
   CIMSS AIDT: 36 KTS AT 161730Z
   CIMSS D-MINT: 40 KTS AT 161557Z
   CIMSS D-PRINT: 40 KTS AT 161730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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 24W IS TRAVELING POLEWARD ALONG THE
SOUTHWESTERN PERIPHERY OF THE STR CENTERED EAST OF HONSHU. THE
POLEWARD MOTION FOLLOWS A TURN DURING THE PAST 18 HOURS UNDER THE
STEERING INFLUENCE OF A NEAR-EQUATORIAL RIDGE POSITIONED SOUTHEAST
OF THE SYSTEM. THE VORTEX WILL GRADUALLY TURN NORTHWESTWARD AT TAU
12 AS THE STR MIGRATES WESTWARD. FROM TAU 60 TO TAU 96, TS 24W WILL
TURN POLEWARD, CROSS THE AXIS OF THE DEEP-LAYER STR, AND ACCELERATE
NORTHEASTWARD AS THE MID-LATITUDE WESTERLY FLOW BECOMES THE
DOMINANT STEERING MECHANISM. FAVORABLE ENVIRONMENTAL CONDITIONS,
INCLUDING VERY WARM SST AND LOW VWS, WILL SUPPORT STEADY TO RAPID
INTENSIFICATION (RI) OVER THE NEXT 12 HOURS. FROM TAU 12 TO TAU 36,
VWS WILL INCREASE TO AROUND 20 KTS, CAUSING THE INTENSITY TREND TO
LEVEL OFF. AFTER TAU 36, TS 24W WILL TAP INTO A POLEWARD OUTFLOW
CHANNEL, ALLOWING FOR RENEWED INTENSIFICATION DESPITE THE MODERATE
VWS. AFTER TAU 72, A WEAKENING TREND WILL COMMENCE AS THE
UNFAVORABLE EFFECTS OF INCREASING VWS MORE THAN OFFSET THE
DEVELOPMENTAL BENEFITS OF STRONG POLEWARD OUTFLOW. INCREASING
BAROCLINIC FORCING WILL SUPPORT EXTRATROPICAL TRANSITION, WHICH
WILL BE WELL UNDERWAY BY TAU 120.

MODEL DISCUSSION: THE OVERALL GUIDANCE ENVELOPE HAS TIGHTENED
MODESTLY SINCE THE LAST CYCLE, WITH THE CROSS-TRACK SPREAD AT TAU
96 DECREASING FROM 180 NM TO 165 NM. A NOTABLE CHANGE HAS BEEN A
GENERAL WESTWARD SHIFT IN THE AI MODEL SOLUTIONS TOWARD THE JTWC
MULTI-MODEL CONSENSUS (CONW). THE JTWC FORECAST TRACK IS PLACED
NEAR THE CONSENSUS THROUGH TAU 48. THEREAFTER, THE FORECAST HAS
BEEN SHIFTED WESTWARD RELATIVE TO THE PREVIOUS FORECAST, TOWARD BUT
NOT QUITE AS FAR WEST AS THE CONSENSUS.  AS A RESULT, THE JTWC
TRACK LIES ALONG THE EASTERN SIDE OF THE CORE MODEL GROUPING AFTER
TAU 48. MULTIPLE RI AIDS HAVE ONCE AGAIN TRIGGERED. GIVEN THE RECENT 
IMPROVEMENT IN THE SATELLITE PRESENTATION OF THE SYSTEM AND THE 
FAVORABLE ENVIRONMENTAL CONDITIONS, THE JTWC FORECAST INTENSITY CALLS 
FOR A 15-KT INCREASE IN THE NEXT 12 HOURS, FOLLOWED BY A SLOWING OF 
THE INTENSIFICATION TREND AT TAU 24. COAMPS-TC AND GFS AGGRESSIVELY 
INTENSIFY THE SYSTEM TO TYPHOON INTENSITY WITHIN 24 HOURS. THE JTWC 
FORECAST REMAINS JUST BELOW THESE MORE AGGRESSIVE SOLUTIONS AND IS 
PLACED CLOSER TO THE EXPERIMENTAL GOOGLE DEEPMIND SOLUTION. MOST AIDS
DEPICT A NEAR-STEADY INTENSITY FROM TAU 24 TO TAU 36, FOLLOWED BY
VARYING DEGREES OF INTENSIFICATION. HAFS-A, WHICH MAINTAINS A
COMPACT INNER CORE, IS THE STRONGEST SOLUTION, REACHING AROUND 100
KTS AT TAU 60. THE JTWC INTENSITY FORECAST IS NEAR THE CENTER OF
THE GUIDANCE ENVELOPE AT TAU 60 AND TAU 72, CLOSEST TO THE
STATISTICAL-DYNAMICAL SHIPS GUIDANCE BUT SLIGHTLY HIGHER THAN
DEEPMIND. AFTER TAU 72, THE FORECAST IS CLOSELY ALIGNED WITH
DEEPMIND AND GFS.

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