WDPN31 PGTW 130300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 04W (SINLAKU) WARNING NR 
017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.2N 148.9E
   INITIAL INTENSITY: 155 KTS
   GEOGRAPHIC REFERENCE: 262 NM EAST-SOUTHEAST OF NAVSTA GUAM
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 43 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS SUPER
TYPHOON (STY) 04W WITH A CLEAR AND WELL-DEFINED EYE MEASURING 10 NM
IN DIAMETER, ACCOMPANIED BY SYMMETRICAL COLD CLOUD TOPS MEASURING
APPROXIMATELY -80 C. A PARTIAL GMI MICROWAVE IMAGE FROM 122338Z
REVEALS THAT STY 04W IS BEGINNING AN EYEWALL REPLACEMENT CYCLE
(ERC); AN OUTER EYEWALL HAS BEGUN TO FORM APPROXIMATELY 50 NM FROM
THE CENTER, THOUGH THE INNER EYEWALL REMAINS STRONG AT THIS TIME.
ENVIRONMENTAL ANALYSIS INDICATES A HIGHLY FAVORABLE ENVIRONMENT,
CHARACTERIZED BY LOW (0-5 KTS) VERTICAL WIND SHEAR, WARM (28-29 C)
SEA SURFACE TEMPERATURES, AND ROBUST OUTFLOW ALOFT. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE WELL-DEFINED
EYE IN ANIMATED MSI. THE INITIAL INTENSITY OF 155 KTS IS ASSESSED
WITH MEDIUM CONFIDENCE BASED ON THE AGENCY SUBJECTIVE DVORAK FIXES
AND CIMSS AUTOMATED INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: THE 121941Z RCM-3 SAR DATA WAS USED TO
ADJUST THE WESTERN 50 KT WIND RADII AND ALL 64KT WIND RADII.

CURRENT STEERING MECHANISM: COMPETING STEERING ENVIRONMENT, WITH AN
EXTENSION OF A NEAR-EQUATORIAL RIDGE (NER) POSITIONED DIRECTLY TO
THE EAST AND A DEEP-LAYER SUBTROPICAL RIDGE (STR) POSITIONED TO THE
NORTHWEST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T7.5 - 155 KTS
   RJTD: T7.5 - 155 KTS
   RCTP: T7.0 - 140 KTS 
   KNES: T7.5 - 155 KTS
   CIMSS SATCON: 164 KTS AT 122300Z
   CIMSS ADT: 161 KTS AT 130030Z
   CIMSS AIDT: 157 KTS AT 130030Z
   CIMSS D-MINT: 166 KTS AT 122126Z
   CIMSS D-PRINT: 155 KTS AT 130030Z

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: STY 04W (SINLAKU) IS EXPECTED TO TRACK ALONG
THE NORTHWESTWARD EXTENSION OF THE NER CENTERED TO ITS SOUTHEAST
FOR THE NEXT 12-36 HOURS. DURING THIS TIME, THE EXTENSION IS
EXPECTED TO CONTINUOUSLY BUILD WHILE THE NER SHIFTS NORTHWARD AND
THE STR CURRENTLY CENTERED TO THE NORTHWEST RETREATS WESTWARD.
BOTH OF THOSE ACTIONS OCCURRING AROUND THE SAME TIME WILL INDUCE A
NORTH-NORTHWEST WARD TRACK BY TAU 36. 04W WILL APPROACH THE RIDGE
AXIS AROUND TAU 48-72, AND TRACK NORTH-NORTHEASTWARD THROUGH THE END 
OF THE FORECAST PERIOD AS IT ROUND THE RIDGE. STY 04W IS CURRENTLY
UNDERGOING AN ERC, AND IS FORECASTED TO BEGIN THE INITIAL WEAKENING
PHASE IMMINENTLY AS SINLAKU ALSO CONTENDS WITH DRY AIR RESTRICTING
THE STORM'S MOISTURE SOURCE AND SLOWING ENTRAINING INTO THE CORE,
IN ADDITION TO THE LOSS OF THE ROBUST POLEWARD OUTFLOW CHANNEL DUE
TO THE PASSAGE OF THE UPPER-LEVEL TROUGH. STY 04W IS EXPECTED TO
GRADUALLY WEAKEN AS THE SYSTEM NEARS THE MARIANAS, AND IS FORECAST
TO BE 125 KTS WHILE IT MAKES ITS CLOSEST APPROACH TO TINIAN AND
SAIPAN AT TAU 36. THE RATE OF WEAKENING IN THE SHORT-TERM FORECAST
MAY BE EXACERBATED IF 04W FAILS TO COMPLETE THE ERC AND IS UNABLE
REINTENSIFY FOLLOWING THE COLLAPSE OF THE INNER EYEWALL. FROM TAU
36 ONWARD, SINLAKU WILL CONTINUE TO WEAKEN AT AN INCREASED RATE DUE
TO THE RELATIVELY DRY ENVIRONMENT IT WILL ENCOUNTER AS IT ROUNDS
THE RIDGE AXIS. 04W IS FORECAST TO CROSS THE 26C ISOTHERM BETWEEN
TAU 48-72, WHICH WILL EXACERBATE WEAKENING THROUGH TAU 120.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT IN A NORTHWESTWARD TRACK THROUGH TAU 36, WITH ALL
CONSENSUS MODELS (EXCLUDING NAVGEM) TIGHTLY CLUSTERED AROUND SAIPAN
AND TINIAN AT TAU 36. MODEL GUIDANCE DIVERGES SLIGHTLY AS 04W IS
EXPECTED TO ROUND THE RIDGE AXIS, THOUGH MOST MODELS REMAIN IN GOOD
AGREEMENT THROUGH FROM TAU 36-120 OUTSIDE OF A FEW OUTLIERS
(NAVGEM, GALWEM, AND GSM). EXPERIMENTAL AI-BASED MODEL GUIDANCE ARE
ALSO IN MODERATE AGREEMENT WITH THE PHYSICS-BASED MODELS, THOUGH
THE AI-MODELS TEND TO DEPICT 04W TAKING A TIGHTER CURVE AROUND THE
RIDGE AXIS. AS A RESULT, THE JTWC TRACK FORECAST IS PLACED CLOSE TO
THE MULTI-MODEL CONSENSUS WITH MEDIUM CONFIDENCE FROM TAU 0-72 AND
LOW CONFIDENCE FROM TAU 72-120. RELIABLE INTENSITY AIDS ARE IN
STRONG AGREEMENT THAT SINLAKU HAS REACHED ITS PEAK INTENSITY AND
WILL WEAKEN FROM TAU 0 THROUGH TAU 120. THE RATE OF INITIAL
WEAKENING VARIES AMONGST MODELS, BUT GUIDANCE COMES BACK INTO
AGREEMENT FOR A STEADY WEAKENING TREND FROM TAU 36-48 TO TAU 120.
THE JTWC INTENSITY GUIDANCE IS PLACED SLIGHTLY ABOVE THE
MULTI-MODEL CONSENSUS AND CLOSE TO THE HAFS-A INTENSITY OUTPUT WITH
OVERALL MEDIUM CONFIDENCE.

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