WDPN31 PGTW 160300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 04W (SINLAKU) WARNING NR 029//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.1N 144.4E
   INITIAL INTENSITY: 100 KTS
   GEOGRAPHIC REFERENCE: 222 NM NORTH OF NAVSTA GUAM
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 35 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON (TY)
04W WITH A CLOUD-FILLED EYE AS THE OUTER EYEWALL THAT HAS FORMED
DURING THE EYEWALL REPLACEMENT CYCLE (ERC) WEAKENS THE INNER EYE. A
152032Z 37 GHZ IMAGE REVEALS THE INNER EYE HAS BECOME ELONGATED
WITH LIMITIED DEEP CONVECTION WHILE THE OUTER EYEWALL IS SYMMETRIC
AND WITH BUILDING DEEP CONVECTION. THE INITIAL WEAKENING PHASE IS
SUSPECTED TO BE OCCURRING CURRENTLY. ENVIRONMENTAL ANALYSIS REVEALS
A FAVORABLE ENVIRONMENT CHARACTERIZED BY LOW (0-5 KTS) VERTICAL
WIND SHEAR, MODERATE (27-28 C) SEA SURFACE TEMPERATURES, AND ROBUST
DIVERGENCE ALOFT. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE CLOUD-FILLED EYE PRESENT IN ANIMATED MSI.
THE INITIAL INTENSITY OF 100 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE AGENCY SUBJECTIVE DVORAK FIXES AND CIMSS AUTOMATED
INTENSITY ESTIMATES LISTED BELOW. UNCERTAINTY IN THE INITAL
INTENSITY ARISES REGARDING THE IMPACT THAT THE WEAKENING PHASE OF
THE ERC IS CURRENTLY CAUSING TO THE SYSTEM.

INITIAL WIND RADII BASIS: THE 152011Z RCM-3 SCATTEROMETER DATA WAS
USED TO ADJUST THE 64 KT WIND RADII

CURRENT STEERING MECHANISM: NORTHEASTERN EXTENSION OF A
NEAR-EQUATORIAL RIDGE (NER) TO THE SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T6.0 - 115 KTS
   KNES: T5.5 - 102 KTS
   CIMSS ADT: 92 KTS AT 160100Z
   CIMSS AIDT: 92 KTS AT 160100Z
   CIMSS D-PRINT: 102 KTS AT 160100Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG RADIAL
   OTHER FACTORS: STORM IS CURRENTLY UNDERGOING AN EYEWALL
REPLACEMENT CYCLE

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: FORECAST SHORTENED TO 72 HOURS IN
RESPONSE TO ALL AVAILABLE GUIDANCE INDICATING EXTRATROPICAL
TRANSITION WILL BEGIN NO LATER THAN TAU 48 AND BE COMPLETE BY TAU
72.

FORECAST DISCUSSION: TY 04W (SINLAKU) IS SLOWLY TRACKING NORTHWARD
AS IT APPROACHES THE AXIS OF THE STEERING NER CENTERED TO ITS
SOUTHEAST. PRIOR TO TAU 12, 04W IS EXPECTED TO ROUND THE AXIS AND
TRACK NORTHEASTWARD THROUGH TAU 72. BEGINNING AROUND TAU 36, THE
SURROUNDING ENVIRONMENT WILL BECOME INCREASINGLY HOSTILE. VERTICAL
WIND SHEAR IS FORECAST TO EXCEED 20KTS BY TAU 36 ALLOWING DRY AIR
TO BE FORCED INTO THE CORE. SINLAKU IS EXPECTED TO PASS NORTH OF
THE 26C ISOTHERM AROUND TAU 48, CAUSING SIGNIFICANT DECAY AND
INDUCING EXTRATROPICAL TRANSITION (ETT). BY TAU 60, THE SYSTEM IS
ANTICIPATED TO BE HIGHLY ASYMMETRICAL WITH LIMITED TROPICAL
CHARACTERISTICS. SINLAKU IS FORECAST TO BE COMPLETELY EMBEDDED IN
THE UPPER-LEVEL JET AND COMPLETE ETT NO LATER THAN TAU 72.
REGARDING INTENSITY, SINLAKU IS FORECAST TO CONTINUE ITS STEADY
WEAKENING TREND FOR THE DURATION OF THE FORECAST PERIOD. IF 04W
FAILS TO COMPLETE ERC AND REINTENSIFY BEFORE FURTHER SIGNIFICANT
DECAY, THE INITIAL WEAKENING PHASE OF THE ERC COULD EXACERBATE THE
STORM'S FORECASTED DETERIORATION.

MODEL DISCUSSION: DETERMINISTIC PHYSICS-BASED MODELS AND AI-BASED
MODELS ARE IN GOOD AGREEMENT FOR THE DURATION OF THE FORECAST
PERIOD. MOST MODELS ARE TIGHTLY CLUSTERED THROUGH TAU 72, BUT THE
CROSS-TRACK SPREAD IS LESS THAN 100 NM AT TAU 72 EVEN INCLUDING
MODELS THAT ARE NOT IN TIGHT AGREEMENT, LENDING HIGH CONFIDENCE IN
THE JTWC TRACK FORECAST FROM TAU 0-72. RELIABLE INTENSITY GUIDANCE
IS IN GOOD AGREEMENT IN STEADY WEAKENING FOR THE DURATION OF THE
FORECAST PERIOD. COAMPS-TC DEPICTS A RAPID WEAKENING THROUGH TAU
48, WHILE GFS, HAFS-A, AND HWRF DEPICT A MORE GRADUAL DECAY. THE
JTWC INTENSITY FORECAST LIES CLOSE TO THE MULTI-MODEL CONSENSUS
WITH OVERALL MEDIUM CONFIDENCE.

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