WDPN31 PGTW 130900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 04W (SINLAKU) WARNING NR 
018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.7N 148.0E
   INITIAL INTENSITY: 150 KTS
   GEOGRAPHIC REFERENCE: 203 NM EAST-SOUTHEAST OF NAVSTA GUAM
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 43 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A HIGHLY
ORGANIZED SUPER TYPHOON (STY) 04W (SINLAKU) EXHIBITING A
NEAR-PERFECTLY AXISYMMETRIC STRUCTURE. A WELL-DEFINED, WARM (18 C)
15 NM DIAMETER EYE IS ENCASED WITHIN A COHESIVE CENTRAL DENSE
OVERCAST (CDO). THE SIZE OF THE CDO HAS SLIGHTLY DECREASED OVER THE 
LAST 6 HOURS, WHICH COMBINED WITH A 3-5 DEGREE COOLING OF THE EYE,
INDICATES A VERY SLIGHT OVERALL WEAKENING, RESULTING FROM AN
ONGOING EYEWALL REPLACEMENT CYCLE (ERC) AND DRY AIR ENTRAINMENT. ON
THE OTHER HAND, THE AMBIENT ENVIRONMENT REMAINS LARGELY FAVORABLE AND 
IS CHARACTERIZED BY WARM (28-29 C) SEA SURFACE TEMPERATURES (SST), LOW
(5-10 KTS) VERTICAL WIND SHEAR (VWS) AND A ROBUST RADIAL OUTFLOW.
BASED ON THE CLEARLY DISCERNIBLE EYE IN THE VISIBLE SATELLITE
IMAGERY, THE INITIAL POSITION IS FIXED WITH HIGH CONFIDENCE. THE
INITIAL INTENSITY OF 150 KTS IS SIMILARLY ASSESSED WITH HIGH
CONFIDENCE, A VALUE SUPPORTED BY A CONSENSUS OF ALL AGENCY DVORAK
ESTIMATES AND OBJECTIVE INTENSITY AIDS, WHICH ALL HAVE BEEN VERY
SLOWLY DECREASING OVER THE LAST 6 HOURS.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T7.5 - 155 KTS
   RJTD: T7.5 - 155 KTS
   RCTP: T7.5 - 155 KTS
   KNES: T7.5 - 155 KTS
   CIMSS SATCON: 139 KTS AT 130600Z
   CIMSS ADT: 152 KTS AT 130530Z
   CIMSS AIDT: 151 KTS AT 130530Z
   CIMSS D-MINT: 149 KTS AT 130346Z
   CIMSS D-PRINT: 151 KTS AT 130700Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG RADIAL
   OTHER FACTORS: SLIGHT DRY AIR ENTRAINMENT

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: THE NEAR-TERM INTENSITY FORECAST SUGGESTS THAT
STY 04W HAS ALREADY ATTAINED ITS MAXIMUM INTENSITY AND IS BEGINNING
TO VERY SLOWLY WEAKEN AS IT APPROACHES THE NORTHERN MARIANA
ISLANDS. INCREASING INFLUENCE OF MID-LEVEL DRY AIR ENTRAINMENT,
ONGOING ERC AND REDUCED NORTHEASTWARD OUTFLOW CHANNEL WILL ALL
CONTRIBUTE TOWARD THIS TREND. SOME TEMPORARY INCREASE IN INTENSITY IS 
POSSIBLE, HOWEVER, ONLY IF THE SYSTEM SUCCESSFULLY COMPLETES THE ERC. 
STY 04W IS EXPECTED TO MAINTAIN AN INTENSITY OF AROUND 135 KTS AT ITS 
CLOSEST POINT OF APPROACH TO THE NORTHERN MARIANAS. AFTERWARDS, A 
CONTINUOUS AND GRADUAL WEAKENING IS FORECAST THROUGHOUT THE REMAINDER 
OF THE CURRENT PERIOD. IN REGARD TO THE TRACK PREDICTION, THE SYSTEM 
IS STILL POSITIONED WITHIN A COMPETING STEERING ENVIRONMENT, WITH AN
EXTENSION OF A NER CENTERED TO THE EAST AND A DEEP-LAYER STR CENTERED 
TO THE NORTHWEST, WITH THE FORMER ASSUMING THE PRIMARY STEERING ROLE. 
THE CPA TO THE MARIANA ISLANDS IS EXPECTED TO OCCUR WITHIN THE NEXT 24 
HOURS, WITH THE TRACK POSITIONED BETWEEN THE ISLANDS OF TINIAN AND 
SAIPAN. AFTER THA, STY 04W WILL BEGIN ITS RECURVATURE ALONG THE AXIS 
OF THE RIDGE BETWEEN TAUS 48 AND 72. BEYOND TAU 72, THE SYSTEM WILL 
CONTINUE TO BE STEERED NORTHEASTWARD BY THE NORTHWARD-BUILDING NEAR-
EQUATORIAL RIDGE, WHICH WILL COINCIDE WITH A MORE PRONOUNCED WEAKENING 
TREND DUE TO INCREASINGLY HOSTILE SHEAR, COOLING SEA SURFACE 
TEMPERATURES, AND DRY AIR ENTRAINMENT.

MODEL DISCUSSION: NUMERICAL TRACK MODEL GUIDANCE IN THE SHORT TERM
IS ASSESSED WITH MEDIUM CONFIDENCE, AS THE CROSS-TRACK SPREAD
DURING THE CPA TO THE MARIANAS IS CURRENTLY 46 NM, INCLUDING THE
PRIMARY OUTLIER NAVGEM, WHICH POSITIONS THE TRACK BETWEEN ROTA AND
TINIAN. EXCLUDING NAVGEM WOULD RESULT IN A 26 NM SPREAD. OFFICIAL JTWC
TRACK FORECAST IS THEREFORE LAID CLOSE TO THE MULTI-MODEL CONSENSUS
WITH MEDIUM CONFIDENCE, OFFSET SLIGHTLY TO THE NORTHEAST. LONG-TERM
TRACK FORECAST IS ASSESSED WITH LOW CONFIDENCE. WHILE ALL MODELS
CONTINUE TO FAVOR THE RECURVATURE SCENARIO, THE CROSS-TRACK AND
ALONG-TRACK SPREAD ARE VERY HIGH, DUE TO DIFFERENT DEPICTION OF THE
TIMELINE OF THE SYSTEM ROUNDING THE AXIS OF THE RIDGE. IN REGARD TO
INTENSITY, JTWC OFFICIAL FORECAST IS LAID WITH MEDIUM CONFIDENCE
AND CLOSE TO THE HAFS INTENSITY PREDICTION. ALL AVAILABLE CONSENSUS
MEMBERS INDICATE GRADUAL WEAKENING, BUT SOME MODELS (COAMPS-TC AND
GFS PRIMARILY) PREDICT A RAPID WEAKENING OVER THE NEXT 24-36 HOURS,
WHICH DOES NOT HAVE STRONG SUPPORT IN THE ANALYSIS OF THE
ENVIRONMENT. 

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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