Advisories

WDPN31 PGTW 170300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (DUJUAN) WARNING NR 
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.0N 150.4E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 449 NM NORTHEAST OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A RAPIDLY
CONSOLIDATING TROPICAL STORM (TS) 24W, WITH VORTICAL HOT TOWERS
EMBEDDED WITHIN A COMPACT CENTRAL DENSE OVERCAST AND SPIRAL BANDING
DEVELOPING ALONG THE NORTHERN AND SOUTHEASTERN PERIPHERIES. THE
COLDEST CLOUD TOP TEMPERATURES MEASURED NEAR -88 DEGREES CELSIUS.
UPPER-LEVEL OUTFLOW HAS IMPROVED SIGNIFICANTLY, VENTING RADIALLY
OUTWARD. TS 24W IS LOCATED NEAR THE SOUTHERN END OF A MERIDIONALLY
ORIENTED SURFACE TROUGH, WHILE AN UPPER-LEVEL TROUGH POSITIONED
NEAR THE FAR NORTHERN MARIANA ISLANDS SUPPRESSES CONVECTION ALONG
THE WESTERN PERIPHERY. THE SYSTEM REMAINS IN A FAVORABLE
ENVIRONMENT OF VERY WARM SEA SURFACE TEMPERATURES (SST), LOW
VERTICAL WIND SHEAR (VWS), AND IMPROVING OUTFLOW ALOFT. A TIMELY
162235Z ASCAT-B PASS REVEALED AN ASYMMETRIC, COMPACT STORM-FORCE
WIND CORE, WITH GALE-FORCE WINDS EXTENDING UP TO 150 NM OUTWARD.
THE SCATTEROMETER DATA AND THE CONTINUED IMPROVEMENT IN THE
CONVECTIVE STRUCTURE SUPPORT RAISING THE INITIAL INTENSITY TO 50
KTS WITH HIGH CONFIDENCE. THIS ASSESSMENT IS HIGHER THAN THE
SUBJECTIVE AND OBJECTIVE ESTIMATES, WHICH MAY TEND TO
UNDERREPRESENT THE INTENSITY OF A RAPIDLY CONSOLIDATING, COMPACT
INNER CORE. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE
BASED ON THE ROTATING MOTION OF THE HOT TOWERS IN MSI AND THE
ASCAT-B WIND FIELD.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: SOUTHERN EXTENSION OF A SUBTROPICAL
RIDGE (STR) CENTERED NEAR 38N 165E

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T2.5 - 35 KTS
   CIMSS SATCON: 41 KTS AT 162011Z
   CIMSS ADT: 39 KTS AT 162330Z
   CIMSS AIDT: 44 KTS AT 170030Z
   CIMSS D-MINT: 41 KTS AT 162010Z
   CIMSS D-PRINT: 38 KTS AT 162300Z

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

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 24W IS ACCELERATING POLEWARD ALONG THE
WESTERN PERIPHERY OF A STR CENTERED EAST OF HONSHU. FROM TAU 24 TO
TAU 48, THE RIDGE WILL BUILD WESTWARD, RESULTING IN A SLOWER, MORE
WESTWARD TRAJECTORY. FROM TAU 48 TO TAU 72, THE SYSTEM WILL TURN
POLEWARD AS IT ROUNDS THE STR, CROSS THE RIDGE AXIS, AND ACCELERATE
NORTHEASTWARD AS IT COMES UNDER THE INFLUENCE OF DEEP-LAYER
MID-LATITUDE WESTERLY FLOW. TS 24W WILL REMAIN IN A FAVORABLE
ENVIRONMENT CHARACTERIZED BY LOW VWS, VERY WARM SST, AND MODERATE
DIVERGENCE ALOFT. HOWEVER, AFTER A 20-KT INCREASE IN INTENSITY OVER
THE PAST 18 HOURS, RECENT SATELLITE IMAGERY INDICATES THAT
DEVELOPMENT MAY BE SLOWING AS THE ASYMMETRIC STRUCTURE TEMPORARILY
CONSTRAINS FURTHER INTENSIFICATION. THEREFORE, THE FORECAST CALLS
FOR A SLOWER RATE OF INTENSIFICATION OVER THE NEXT 24 HOURS. FROM
TAU 24 TO TAU 48, MODERATE VWS WILL LIMIT ADDITIONAL
INTENSIFICATION. BY TAU 48, A POLEWARD OUTFLOW CHANNEL WILL OPEN AS
THE SYSTEM APPROACHES THE STR AXIS, SUPPORTING A SECOND ROUND OF
MODEST INTENSIFICATION. ONCE THE VORTEX ROUNDS THE AXIS AT TAU 72,
GRADUAL WEAKENING WILL COMMENCE AS INCREASING VWS MORE THAN OFFSETS
THE DEVELOPMENTAL BENEFITS OF ENHANCED POLEWARD OUTFLOW. TS 24W
WILL UNDERGO EXTRATROPICAL TRANSITION TOWARD THE END OF THE
FORECAST PERIOD AS IT ENCOUNTERS A STRONGER BAROCLINIC ENVIRONMENT.

MODEL DISCUSSION: THE TRACK GUIDANCE REMAINS IN GOOD AGREEMENT
THROUGH TAU 120, THOUGH ALONG-TRACK SPREAD BEGINS TO INCREASE AFTER
TAU 72. THE AI MODELS LIE FARTHER WEST THAN THE PHYSICS-BASED
MODELS. THE JTWC FORECAST TRACK IS POSITIONED NEAR THE MULTI-MODEL
CONSENSUS (CONW) WITH HIGH CONFIDENCE THROUGH TAU 72. AFTER TAU 72,
TRACK CONFIDENCE DECREASES TO MEDIUM AS THE AI MODELS DIVERGE
SLIGHTLY FROM THE CONSENSUS, WITH THE FORECAST TRACK FAVORING A
BLEND OF THE AI SOLUTIONS AND THE CONSENSUS. HAFS-A, GFS, AND ECMWF
ARE THE EASTERNMOST SOLUTIONS AT TAU 96 AND TAU 120. THE INTENSITY
AIDS HAVE BECOME HIGHLY DIVERGENT THIS CYCLE. MULTIPLE RAPID
INTENSIFICATION (RI) AIDS HAVE AGAIN TRIGGERED. HOWEVER, GIVEN THE
SLOWING IMPROVEMENT IN THE SATELLITE PRESENTATION, THESE AIDS ARE
DISCOUNTED. THE DYNAMICAL MODELS ARE MIXED, WITH GFS AND HAFS-A
SHOWING A NEAR-STEADY INTENSITY THROUGH TAU 120 AND COAMPS-TC
DEPICTING MODEST INTENSIFICATION TO TYPHOON INTENSITY. GIVEN THAT
THESE AID SOLUTIONS REPRESENT A SIGNIFICANT DEPARTURE FROM THE
PRIOR CYCLE, ONLY MINIMAL CHANGES WERE MADE TO THE JTWC INTENSITY
FORECAST. TWO DISTINCT SCENARIOS ARE POSSIBLE. IF THE SYSTEM
MAINTAINS A COMPACT CORE THROUGH THE NEXT 72 HOURS, IT COULD ATTAIN
A MUCH HIGHER PEAK INTENSITY THAN CURRENTLY FORECAST. THIS PATHWAY
WAS DEPICTED IN THE PRIOR HAFS-A SOLUTION. THE ALTERNATE SCENARIO,
TOWARD WHICH THIS FORECAST LEANS, IS THAT THE COMPACT CORE BROADENS
INTO THE LARGER PRE-EXISTING CIRCULATION. THIS EVOLUTION WOULD
LIMIT THE SYSTEM'S PEAK INTENSITY.

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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