WDPN31 PGTW 110300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 04W (SINLAKU) WARNING NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 8.5N 151.5E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 502 NM SOUTHEAST OF NAVSTA GUAM
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON (TY)
04W AS A QUICKLY DEVELOPING STORM WITH SPIRAL BANDS OF DEEP
CONVECTION WRAPPING INTO THE CENTRAL DENSE OVERCAST. ENVIRONMENTAL
ANALYSIS REVEALS A HIGHLY FAVORABLE ENVIRONMENT CHARACTERIZED BY
LOW (5-10 KTS) VERTICAL WIND SHEAR, WARM (28-29 C) SEA SURFACE
TEMPERATURES, AND ROBUST RADIAL OUTFLOW, WITH A PARTICULARLY STRONG
POLEWARD OUTFLOW CHANNEL SUPPORTED BY A DEEP LAYER TROUGH TO THE
NORTH AND THE NEAR EQUATORIAL RIDGE CENTERED TO THE SOUTHEAST. TY
04W REMAINS QUASI-STATIONARY APPROXIMATELY 70 NM NORTH-NORTHEAST OF
CHUUK, BUT ANY UPWELLING IS NOT ANTICIPATED TO HAVE A TANGIBLE
IMPACT TO THE STORM'S INTENSITY. THE INITIAL POSITION IS PLACED
WITH LOW CONFIDENCE BASED ON THE AGENCY POSITION FIXES AND LOW
LEVEL CLOUD TRACING IN ANIMATED EIR. THE INITIAL INTENSITY OF 75
KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY
SUBJECTIVE DVORAK FIXES LISTED BELOW AND THE CIMSS AUTOMATED
INTENSITY ESTIMATES, BUT LACK OF SATELLITE WINDSPEED DATA HAS MADE
DEFINITIVELY DETERMINING WINDSPEED DIFFICULT.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T4.5 - 77 KTS
   RCTP: T4.5 - 77 KTS
   KNES: T4.5 - 77 KTS
   CIMSS ADT: 77 KTS AT 110100Z
   CIMSS AIDT: 78 KTS AT 110100Z
   CIMSS D-PRINT: 78 KTS AT 110100Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 04W (SINLAKU) REMAINS IN A WEAK STEERING
ENVIRONMENT, TRAPPED BETWEEN THE NER TO ITS SOUTHEAST AND THE STR
CENTERED TO THE NORTHWEST.  THE RESULTING QUASI-STATIONARY PERIOD
MAY INDUCE ERRATIC MOTION WHICH IS UNABLE TO BE REFLECTED ON THE
JTWC TRACK FORECAST. OVER THE PAST 6 HOURS, 04W APPEARS TO HAVE
LOOPED AROUND TO MEANDER NORTH-NORTHWESTWARD FOR THE NEXT 12 HOURS
AS EXPECTED. BY TAU 12, 04W IS EXPECTED TO ASSUME A NORTHWESTWARD
TRACK AS THE NER CENTERED TO THE STORM'S SOUTHEAST BUILDS A
NORTHWESTWARD-ORIENTED EXTENSION AND THE STR CENTERED TO THE
NORTHEAST RETREATS OVER THE SOUTH CHINA SEA. TY 04W WILL ACCELERATE
AND TRACK GENERALLY NORTHWESTWARD ALONG THE EXTENSION FROM TAU 12
TO TAU 120. 04W IS FORECAST TO IMPACT GUAM NEAR TAU 72 AT AN
INTENSITY OF APPROXIMATELY 115 KTS, WITH THE JTWC TRACK FORECAST
CONSISTENTLY REMAINING DIRECTLY OVER OR JUST SOUTH OF THE ISLAND.
THE STORM IS PHYSICALLY LARGE, WITH AN EXPANSIVE ELEVATED WINDFIELD
THAT IS EXPECTED TO PERSIST FOR THE DURATION OF THE FORECAST. TY
04W IS ASSESSED TO BE UNDERGOING RAPID INTENSIFICATION (RI), WHICH
IS FORECAST TO OCCUR BETWEEN TAU 0 AND TAU 36 BEFORE SINLAKU PEAKS
AT AN INTENSITY OF 120 KTS AT TAU 36-48. A PEAK INTENSITY HIGHER
THAN 115 KTS MAY OCCUR AROUND TAU 60 AND IS UNABLE TO BE REFLECTED
IN THE JTWC INTENSITY FORECAST. FOLLOWING THE PEAK INTENSITY, 04W
IS FORECAST TO WEAKEN SLIGHTLY THROUGH THE END OF THE FORECAST
PERIOD AS THE STORM BEGINS TO FEEL A SLIGHT INCREASE IN MID-LEVEL
VERTICAL WIND SHEAR. 

MODEL DISCUSSION: DETERMINISTIC TRACK MODEL GUIDANCE IS IN MODERATE
AGREEMENT IN TRACK THROUGH TAU 72, WITH ALL MODELS IN AGREEMENT
THAT 04W WILL TRACK GENERALLY NORTHWESTWARD ALONG THE NER
EXTENSION. UNCERTAINTY ARISES IN THE LATE-TERM FORECAST, WITH A 350
NM CROSS-TRACK SPREAD AT TAU 72 (APPROXIMATE CPA TO GUAM) AND
APPROXIMATELY 575 NM CROSS-TRACK SPREAD OCCURRING BY TAU 120.
OUTLIERS ARE UKMET AND GALWEM FAR TO THE NORTH, CONTRIBUTING TO THE
SIGNIFICANT CROSS-TRACK SPREAD. THE EXPERIMENTAL AI-BASED MODELS
CONTINUE TO DEPICT A TRACK NORTH OF GUAM, BUT HAVE SHIFTED SOUTH TO
SHRINK THE DISTANCE TO THE PHYSICS-BASED MODELS AND NOW DEPICT A
TRACK OVER ROTA. THE JTWC TRACK FORECAST LIES CLOSE TO THE
MULTI-MODEL CONSENSUS MEAN WITH OVERALL LOW CONFIDENCE. RELIABLE
INTENSITY GUIDANCE IS IN GOOD AGREEMENT IN THE RATE OF
INTENSIFICATION THROUGH TAU 36 AND THE PEAK INTENSITY OCCURRING
AROUND TAU 48-60, BUT THE PEAK RANGES FROM 100 KTS TO 135 KTS.
MODELS DISAGREE THE RATE OF WEAKENING IN THE LATE-TERM FORECAST,
LENDING UNCERTAINTY TO THE JTWC INTENSITY FORECAST. THE AS A
RESULT, THE JTWC INTENSITY FORECAST LIES CLOSE TO THE MULTIMODEL
CONSENSUS, AND IS ASSESSED WITH MEDIUM CONFIDENCE FROM TAU 0-72 AND
LOW FROM TAU 72-10. 

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