WDPN31 PGTW 100900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (SINLAKU) WARNING NR 
006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 8.2N 151.0E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 488 NM SOUTHEAST OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: WESTWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A
CONSOLIDATING LOW-LEVEL CIRCULATION CENTER (LLCC) EMBEDDED WITHIN A
RAGGED CENTRAL DENSE OVERCAST (CDO), WITH EXTENSIVE SPIRAL BANDS
WRAPPING INTO THE CENTER. THE QUASI-STATIONARY LLCC REMAINS
PARTIALLY EXPOSED IN THE SOUTHEAST QUADRANT. THE ATMOSPHERIC
SOUNDING AT CHUUK, COURTESTY OF THE NATIONAL WEATHER SERVICE OFFICE
AT TIYAN, DEPICTS 10-15 KTS OF SOUTHEASTERLY FLOW AT 200-300 MB,
WHICH CONFIRMS THE PRESENCE OF SOME VERTICAL WIND SHEAR (VWS) AND
IS CONSISTENT WITH RESTRICTED UPPER-LEVEL OUTFLOW IN THE SOUTHEAST
QUADRANT OBSERVED IN THE SATELLITE IMAGERY. A 092213Z ASCAT-C PASS
DISPLAYED A SOMEWHAT ASYMMETRIC SURFACE CIRCULATION, WHICH HELPS TO
EXPLAIN SOME OF THE RECENT SATELLITE-DETECTED LIGHTNING STRIKES IN
THE MORE ROBUST BURSTS OF CONVECTION WITHIN THE CDO. HOWEVER, THE
ENVIRONMENT IS FAVORABLE FOR DEVELOPMENT, CHARACTERIZED BY WARM SEA
SURFACE TEMPERATURES (SST), ABUNDANT DEEP-LAYER MOISTURE, EXCEPT
FOR A DRY SLOT IMMEDIATELY SOUTHEAST OF THE LLCC, AND MODERATE
POLEWARD AND WESTWARD EXHAUST. THE INITIAL POSITION IS ASSESSED
WITH MEDIUM CONFIDENCE DUE TO OBSCURATION BY THE CDO. THE INITIAL
INTENSITY IS SET AT 45 KTS WITH HIGH CONFIDENCE BASED ON A BLEND OF
THE RISING MULTI-AGENCY DVORAK ESTIMATES RANGING FROM T2.5 TO T3.5
AND THE CIMSS OBJECTIVE ESTIMATES LARGELY SUPPORTING 45 KTS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WEAK STEERING ENVIRONMENT WITH A
NEAR-EQUATORIAL RIDGE (NER) TO THE EAST AND A STRONG SUBTROPICAL
RIDGE (STR) TO THE NORTHWEST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T3.5 - 55 KTS
   KNES: T3.5 - 55 KTS
   CIMSS SATCON: 45 KTS AT 100348Z
   CIMSS ADT: 43 KTS AT 100540Z
   CIMSS AIDT: 37 KTS AT 100540Z
   CIMSS D-MINT: 44 KTS AT 100603Z
   CIMSS D-PRINT: 46 KTS AT 1000610Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: THE FORECAST TRACK HAS CHANGED LITTLE FROM
THAT IN THE PREVIOUS WARNING, SHIFTING SLIGHTLY TO THE SOUTH AT TAU
96 AND TAU 120. THE STEERING ENVIRONMENT IS DICTATED BY A NER TO
THE EAST THAT WILL COMPETE WITH A STRONG STR TO THE NORTHWEST, WITH
A WEAKNESS IN THE RIDGE TO THE NORTH OF THE SYSTEM. THE INFLUENCE
OF THESE COMPETING FEATURES WILL YIELD A SLOW TRACK TOWARDS THE
NORTHWEST THROUGH TAU 36. TS 04W WILL GAIN FORWARD SPEED BY TAU 48
AS THE NER BUILDS TO THE EAST, AND THE FASTER MOVEMENT WILL
CONTINUE TO THE END OF THE FORECAST PERIOD. THE UNCERTAINTY IN THE
EVOLUTION OF THE RIDGES LENDS TO LOW CONFIDENCE IN THE FORECAST
TRACK. GIVEN THE LARGELY FAVORABLE ENVIRONMENTAL CONDITIONS, THE
SYSTEM WILL CONTINUE TO INTENSIFY AT NEAR THE CLIMATOLOGICAL RATE
THROUGH TAU 24. RAPID INTENSIFICATION IN THE SHORT TERM IS LESS
LIKELY BECAUSE THE LARGE SYSTEM IN THE FACE OF SOME VWS ALOFT WILL
NECESSITATE A PERIOD OF TIME TO WORK OUT THE ASYMMETRIES IN THE
NASCENT INNER CORE. HOWEVER, ONCE THE INNER CORE BECOMES SYMMETRIC,
TS 04W WILL UNDERGO A HIGHER RATE OF INTENSIFICATION. WHILE THE
CURRENT FORECAST SHOWS A 25 KT INCREASE IN 24 HOURS, WHICH IS JUST
SHY OF RAPID INTENSIFICATION (RI), AND A PEAK OF 110 KTS, IT IS NOT
OUT OF THE QUESTION THAT THE SYSTEM COULD INTENSIFY FASTER AND
REACH A HIGHER PEAK PRIOR TO REACHING GUAM. TOWARDS THE END OF
FORECAST PERIOD, A MODERATION OF INTENSITY IS INDICATED AS THE
SYSTEM COULD UNDERGO AN EYEWALL REPLACEMENT CYCLE AND APPROACH ITS
MAXIMUM POTENTIAL INTENSITY.

MODEL DISCUSSION: THE CROSS-TRACK SPREAD HAS NARROWED SLIGHTLY TO
300 NM AT TAU 96 AND 400 NM AT TAU 120, WITH THE GFS AND GEFS MEAN
TRACKERS SHIFTING NORTHWARD AND CLOSER TO GUAM BUT REMAINING ON THE 
SOUTHWESTERN EDGE OF THE GUIDANCE ENVELOPE. THE ECMWF HAS SHIFTED 
SLIGHTLY CLOSER TO GUAM AS WELL AND LIES VERY CLOSE TO THE CONSENSUS 
MEAN AND THE ECMWF ENSEMBLE MEAN. THE FORECAST TRACK IS PLACED ALONG 
THE GROUPING OF THESE MODELS AND IS VIRTUALLY UNCHANGED THROUGH TAU 
72. THE TRACK IS SHIFTED SLIGHTLY TO THE SOUTH AT TAU 96 AND TAU 120, 
PRIMARILY DUE TO THE HAFS-A AND HWRF MESOSCALE MODELS SHIFTING 
SOUTHWARD AND THE EXPERIMENTAL AI MODELS SHIFTING CLOSER TO GUAM. 
OVERALL, CONFIDENCE REMAINS LOW THROUGH THE FORECAST PERIOD. THE 
FORECAST INTENSITY FOLLOWS THE CONSENSUS THROUGH TAU 24 AT THE 
CLIMATOLOGICAL RATE AND THEN HEDGES CLOSER TO THE HAFS-A OUTPUT 
DEPICTING A FASTER RATE OF DEVELOPMENT. THE PEAK INTENSITY OF 110 KTS 
IS ON THE HIGHER END OF THE MODEL SUITE BUT STILL LOWER THAN
THE 125 KTS DEPICTED BY HAFS-A AT TAU 72.

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