WDPN31 PGTW 112100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 04W (SINLAKU) WARNING NR 012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 9.3N 151.5E
   INITIAL INTENSITY: 95 KTS
   GEOGRAPHIC REFERENCE: 475 NM EAST-SOUTHEAST OF NAVSTA GUAM
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 35 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TYPHOON
(TY) 04W (SINLAKU) STRUGGLING TO FORM A RAGGED EYE WHILE RAPIDLY
INTENSIFYING. ENVIRONMENTAL ANALYSIS INDICATES HIGHLY FAVORABLE
CONDITIONS FOR CONTINUED INTENSIFICATION, 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 NORTH AND THE NER TO THE SOUTHEAST. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON BASED ON THE FORMING EYE AND
SUPPORTED BY THE 111828Z SSMIS MICROWAVE IMAGE. THE INITIAL
INTENSITY OF 95 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE
AGENCY DVORAK FIXES AND CIMSS AUTOMATED INTENSITY ESTIMATES LISTED
BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

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: T5.0 - 90 KTS
   RJTD: T5.5 - 102 KTS
   RCTP: T5.5 - 102 KTS
   KNES: T5.0 - 90 KTS
   CIMSS SATCON: 91 KTS AT 111600Z
   CIMSS ADT: 82 KTS AT 111900Z
   CIMSS AIDT: 84 KTS AT 111900Z
   CIMSS D-MINT: 93 KTS AT 111828Z
   CIMSS D-PRINT: 88 KTS AT 111900Z

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: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TY 04W HAS MOSEYED NORTHWARD AS THE STEERING
ENVIRONMENT REMAINS WEAK, BUT IS BEGINNING TO BECOME MORE DOMINANT
AS NER BUILDS THE NORTHEAST EXTENSION. 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 EXIT
ITS QUASI-STATIONARY ENVIRONMENT AND ACCELERATE ALONG A
NORTHWESTWARD TRACK THROUGH TAU 48. 04W IS EXPECTED TO TRACK
GENERALLY NORTHWARD FROM TAU 48 THROUGH THE END OF THE FORECAST
PERIOD AS THE NER EXTENSION STRENGTHENS AND REORIENTS. 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 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 24 AND FOLLOWED BY
ADDITIONAL INTENSIFICATION AT A SLIGHTLY SLOWER RATE. 04W IS
FORECAST TO PEAK AT 130 KTS AT AROUND TAU 48. AS 04W TRACKS
NORTHWESTWARD, THE MID-LEVEL SHEAR WILL BEGIN TO INCREASE, LEADING
TO A GRADUAL WEAKENING TREND BEGINNING AROUND TAU 48 THROUGH THE
REMAINDER OF THE FORECAST. 

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.
CURRENTLY, ALL MODELS FAVOR THE NER REMAINING THE DOMINANT
STEERING RIDGE FOR THE DURATION OF THE FORECAST, HOWEVER, IF THE
STR TO THE WEST-NORTHWEST FAILS TO RETREAT WESTWARD, 04W MAY TRACK
FARTHER WESTWARD THAN CURRENTLY FORECAST. THE STR WOULD PROVIDE A
WESTWARD COMPONENT, WHILE THE EXTENSION OF THE NER TO THE SOUTHEAST
WOULD STEER THE SYSTEM NORTHWARD, CONTRIBUTING TO THE HIGH TRACK
FORECAST UNCERTAINTY. TRACK SPEED ALSO CONTINUES TO BE AN ISSUE,
WITH MODELS DISAGREEING ON TRANSLATION SPEED WHILE 04W GRADUALLY
ACCELERATES, COMPOUNDING INTO ADDITIONAL TRACK SPEED DISAGREEMENTS
AS 04W TURNS NORTHWARD AROUND TAU 48. AS A RESULT, THE JTWC TRACK
FORECAST IS PLACED WITH OVERALL LOW CONFIDENCE. RELIABLE INTENSITY
GUIDANCE IS IN GOOD AGREEMENT IN THE RATE OF INTENSIFICATION
THROUGH TAU 24, WITH MOST JTWC RAPID INTENSIFICATION AIDS REACHING
CRITERIA. GUIDANCE AGREES ON A PEAK INTENSITY BETWEEN TAUS 36-48,
BUT RANGES FROM 115 KTS TO 135 KTS. MODELS ALSO AGREE ON THE RATE
OF WEAKENING IN THE LATE-TERM FORECAST, BUT THE DISCREPANCY IN PEAK
INTENSITY LEADS TO A LARGE SPREAD BY THE END OF THE FORECAST. 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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