WDPN31 PGTW 120300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 04W (SINLAKU) WARNING NR 013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 9.9N 151.2E
   INITIAL INTENSITY: 110 KTS
   GEOGRAPHIC REFERENCE: 440 NM EAST-SOUTHEAST OF NAVSTA GUAM
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 35 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON (TY)
04W WITH A WELL-DEFINED AND SYMMETRICAL EYE APPROXIMATELY 15 NM IN
DIAMETER. 04W CONTINUES TO RAPIDLY INTENSIFY, STRENGTHENING FROM 75 
KTS AT 110000Z TO 110 KTS ASSESSED AT 120000Z. ADDITIONALLY, THE EYE 
TEMPERATURE WAS MEASURED TO BE -40C AT 120000Z AND HAS WARMED TO +11C 
BY 120300Z. THE STORM HAS STARTED TO ACCELERATE NORTHWESTWARD OVER THE 
PAST 6 HOURS, INDICATING THE STEERING NER IS BUILDING THE NORTHWEST-
ORIENTED EXTENSION. THE ENVIRONMENT REMAINS HIGHLY FAVORABLE, 
CHARACTERIZED BY LOW (0-5 KTS) VERTICAL WIND SHEAR, WARM (28-29 C) SEA 
SURFACE TEMPERATURES, AND STRONG DIVERGENCE ALOFT SUPPORTED BY AN 
UPPER-LEVEL TROUGH TO THE NORTHEAST AND THE STEERING NER. THE INITIAL 
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE CLEARLY DEFINED 
EYE IN ANIMATED MSI. THE INITIAL INTENSITY OF 110 KTS IS ASSESSED WITH 
HIGH CONFIDENCE BASED ON THE 111941Z RCM-3 SAR DATA AND THE CONSENSUS 
OF AGENCY DVORAK FIXES AND CIMSS AUTOMATED INTENSITY ESTIMATES LISTED 
BELOW.

INITIAL WIND RADII BASIS: 111941Z RCM-3 SAR DATA 

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: T6.0 - 115 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T6.0 - 115 KTS
   KNES: T6.5 - 127 KTS
   CIMSS ADT: 115 KTS AT 120100Z
   CIMSS AIDT: 112 KTS AT 120100Z
   CIMSS D-PRINT: 124 KTS AT 120100Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 0-5 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG 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: TY 04W (SINLAKU) IS SLOWLY DRIFTING
NORTH-NORTHWESTWARD UNDER THE WEAK STEERING INFLUENCE OF THE NER
EXTENSION BUILDING TO THE NORTHWEST. THE EXTENSION WILL CONTINUE TO
BUILD WHILE THE STR CURRENTLY CENTERED OVER THE PHILIPPINES WILL
SHIFT WESTWARD OVER THE SOUTH CHINA SEA, ALLOWING SINLAKU TO
CONTINUE TO ACCELERATE AND TRACK NORTHWESTWARD THROUGH TAU 48.
LEADING UP TO TAU 72, 04W WILL CURVE NORTHWARD AS THE NER EXTENSION
STRENGTHENS AND SHIFTS NORTHWARD, INDUCING A NORTHWARD TRACK FOR
THE REMAINDER OF THE FORECAST PERIOD. SINLAKU IS FORECAST TO IMPACT
THE SOUTHERN MARIANAS ISLANDS AT NEAR PEAK INTENSITY AT AROUND TAU
60, PASSING CLOSE TO ROTA. THE STORM IS PHYSICALLY VERY LARGE, WITH
AN EXPANSIVE ELEVATED WINDFIELD THAT IS EXPECTED TO ENCOMPASS THE
SOUTHERN MARIANAS ISLANDS FOR SEVERAL TAUS. REGARDING INTENSITY,
SINLAKU IS FORECAST TO CONTINUE RAPIDLY INTENSIFYING FOR THE NEXT
12 HOURS, FOLLOWED BY ADDITIONAL INTENSIFICATION AT A SLIGHTLY
SLOWER RATE THROUGH TAU 24-36. BETWEEN TAUS 24-36, 04W IS FORECAST
TO REACH ITS PEAK INTENSITY OF 130 KTS. FOLLOWING THE PEAK AT TAU
36, 04W WILL WEAKEN SLIGHTLY THROUGH TAU 72. AT THAT POINT, THE
MID-LEVEL SHEAR WILL  INCREASE AND THE STORM WILL BEGIN TO ENTRAIN
DRIER AIR INTO ITS CORE, LEADING TO THE MORE DRASTIC WEAKENING
TREND AT THE END OF THE FORECAST PERIOD.

MODEL DISCUSSION:  NUMERICAL MODEL PREDICTION GUIDANCE IS IN FAIR
AGREEMENT ON THE GENERAL STEERING PATTERN AND NORTHWESTWARD TRACK
WITH A NORTHWARD CURVE BY THE END OF THE FORECAST PERIOD. TRACK
GUIDANCE HAS BEEN CONSISTENTLY SHIFTING NORTH WHILE THE CROSS-TRACK
SPREAD IS DECREASING, TO PLACE THE MULTIMODEL CONSENSUS AND MOST
RELIABLE INDIVIDUAL MEMBERS OVER ROTA AND TINIAN. CONSEQUENTLY, THE
JTWC FORECAST TRACK HAS BEEN CONTINUOUSLY SHIFTING NORTHWARD TO
REFLECT THE INCREASING CONFIDENCE IN THE DATA. AS A RESULT, THE
JTWC TRACK FORECAST IS PLACED WITH MEDIUM CONFIDENCE FROM TAU 0-72
AND LOW CONFIDENCE FROM TAU 72-120. RELIABLE INTENSITY GUIDANCE IS
IN GOOD AGREEMENT IN THE RATE OF INTENSIFICATION THROUGH TAU 12,
WITH MULTIPLE JTWC RAPID INTENSIFICATION AIDS REACHING CRITERIA.
RELIABLE GUIDANCE AGREES ON A PEAK INTENSITY BETWEEN TAUS 12-36 AND
RANGES FROM 120 KTS TO 135 KTS, LENDING CONFIDENCE TO THE
SHORT-TERM JTWC INTENSITY FORECAST. MODELS ALSO AGREE ON THE RATE
OF WEAKENING IN THE LATE-TERM FORECAST WITH GENERAL AGREEMENT IN
THE INTENSITY AT TAU 120, DESPITE SLIGHT DISCREPANCIES IN BOTH
INITIAL AND PEAK INTENSITIES AMONGST MODELS. THE JTWC INTENSITY
FORECAST LIES CLOSE TO THE MULTIMODEL CONSENSUS, AND IS ASSESSED
WITH HIGH CONFIDENCE FROM TAU 0-72 AND MEDIUM CONFIDENCE FROM TAU
72-120. 

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