WDPN31 PGTW 141500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (SIXTEEN) WARNING 
NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.3N 160.3E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 904 NM EAST OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: WESTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THAT THE
CONVECTIVE STRUCTURE OBSERVED EARLIER HAS DISSIPATED, WITH REMNANT
CIRRUS OBSCURING THE LOW LEVEL CIRCULATION CENTER (LLCC). MODERATE
CONVECTION IS FLARING TO THE EAST AND WEST OF THE ASSESSED LLCC,
BUT IS AT PRESENT VERY DISORGANIZED AND FAILING TO CONSOLIDATE INTO
SPIRAL BANDS. IN LIGHT OF THE OBSCURED LLCC AND THE LACK OF RECENT
MICROWAVE OR SCATTEROMETER PASSES, THE INITIAL POSITION IS HIGHLY
UNCERTAIN, AND IS POSITIONED OUT FRONT OF AGENCY FIX POSITIONS WITH
LOW CONFIDENCE. THE INITIAL INTENSITY OF 35 KNOTS IS ASSESSED WITH
LOW CONFIDENCE BASED ON THE PGTW AND KNES DVORAK CURRENT INTENSITY
ESTIMATES, DISCARDING THE UNREALISTICALLY HIGH ADT AND SATCON
ESTIMATES. WATER VAPOR IMAGERY AND CIMSS AMV ANALYSIS REVEALS A
SHARP NORTH-SOUTH ORIENTED UPPER-LEVEL RIDGE JUST EAST OF TS 16W,
WHILE THERE REMAINS A VERY WEAK POINT SOURCE DIRECTLY OVER THE
SYSTEM. THE SMALL POINT SOURCE APPEARS TO BE WEAKENING IN THE FACE
OF MODERATE TO STRONG (25-35 KNOTS) NORTHEASTERLY FLOW ON THE EAST
SIDE OF THE RIDGE. THUS WHILE SHEAR IS CURRENTLY LOW IN CLOSE
VICINITY TO THE SYSTEM ITSELF, THE EFFECTS OF THE NORTHEASTERLY
FLOW CAN BE SEEN IN THE ERODED CLOUD PATTERN ON THE EASTERN SIDE OF
THE SYSTEM. CONVERSELY, A SMALL TUTT CELL REMAINS ABOUT 800 NM TO
THE NORTHWEST AND CIMSS AMV ANALYSIS REVEALS WEAK TO MODERATE
POLEWARD OUTFLOW ON THE SOUTHEAST SIDE OF THE TUTT.

INITIAL WIND RADII BASIS: PERSISTENCE. 

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF THE DEEP
SUBTROPICAL RIDGE (STR) TO THE NORTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T1.0 - 25 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 50 KTS AT 140830Z
   CIMSS ADT: 57 KTS AT 141140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: CONFIDENCE IN THE INITIAL POSITION IS LOW,
BUT BASED ON ANIMATED EIR, IT APPEARS THAT TROPICAL STORM 16W HAS
RESUMED A MORE WESTWARD TRACK, CONFIRMED BY THE CLUSTERING OF
MULTI-AGENCY FIX POSITIONS OVER THE PREVIOUS SIX HOURS. TROPICAL
STORM 16W IS CURRENTLY TRACKING WESTWARD ALONG THE SOUTHERN
PERIPHERY OF A DEEP-LAYER STR TO THE NORTH. NO CHANGE IN THE
STEERING PATTERN IS EXPECTED THROUGH TAU 48. AFTER PASSING JUST
SOUTH OF GUAM AROUND TAU 60, THE SYSTEM IS EXPECTED TO BEGIN
TURNING ONTO A WEST-NORTHWEST TRACK AS THE STR MOVES EAST AND
REORIENTS. THE ENVIRONMENT SURROUNDING TS 16W REMAINS GENERALLY
FAVORABLE FOR DEVELOPMENT, WITH VERY WARM WATERS HIGH OHC VALUES.
THE UPPER-LEVEL, NORTH-SOUTH ORIENTED RIDGE MENTIONED IN THE
ANALYSIS IS FORECASTED TO MOVE ROUGHLY IN PHASE WITH TS 16W OVER
THE NEXT 36 TO 48 HOURS, AND WILL INDUCE CONVERGENCE AND ENHANCED
VWS ON THE EASTERN SIDE OF TS 16W, INHIBITING DEVELOPMENT. THE
FORECAST CALLS FOR A SLIGHT WEAKENING, BELOW TS STRENGTH OVER THE
NEXT 24 HOURS AS THE RIDGE PUSHES SLIGHTLY AHEAD OF THE LLCC. THE
RIDGE WILL FALL BEHIND THE LLCC AROUND TAU 36, ALLOWING FOR SLOW
INTENSIFICATION THROUGH TAU 72. AFTER PASSING GUAM, THE UPPER-LEVEL
PATTERN SHIFTS ENOUGH TO ALLOW FOR THE DEVELOPMENT OF A ROBUST
POINT SOURCE OVER TS 16W, ALLOWING FOR A PERIOD OF MORE RAPID
INTENSIFICATION, PEAKING AT 75 KNOTS BY TAU 120.     

MODEL DISCUSSION: WHILE CONFIDENCE IN THE INITIAL POSITION AND
SUBSEQUENT NEAR-TERM TRACK MOTION REMAINS LOW, NUMERICAL MODEL
GUIDANCE REMAINS IN GOOD AGREEMENT ON OVERALL TRACK. DISCOUNTING
THE ECMWF AND HWRF MODELS WHICH ARE DISPLACED TO THE SOUTH, ALL
REMAINING TRACKERS ARE WELL CLUSTERED WITH A 75 NM AT TAU 48,
INCREASING TO 210 NM AT TAU 120. THE JTWC FORECAST FAVORS THE
SOUTHERN EDGE OF THE GUIDANCE ENVELOPE THROUGH TAU 48, THEN MOVES
CLOSER, BUT STILL SOUTH, OF THE CONSENSUS MEAN THROUGH TAU 120,
WITH MEDIUM CONFIDENCE. THE INTENSITY GUIDANCE REMAINS HIGHLY
UNCERTAIN, WITH LOW OVERALL CONFIDENCE. THE RAPID INTENSITY
PREDICTION AID (RIPA) CONTINUES TO BE TRIGGERED, CONTINUING TO
INDICATE A 100 KNOT SYSTEM BY TAU 72. SHIPS-GFS ALSO REMAINS
BULLISH ON STEADY INTENSIFICATION FROM TAU 00. THE REMAINDER OF THE
GUIDANCE, PARTICULARLY THE HWRF AND COAMPS-TC, REMAINS FLAT OR
SLIGHTLY WEAKENS THE SYSTEM THROUGH TAU 48, THEN SHOWS STEADY
INTENSIFICATION THEREAFTER. THE CURRENT FORECAST CONTINUES TO
DISCOUNT THE RIPA AS AN UNREALISTIC SOLUTION, AND CLOSELY TRACKS
THE COAMPS-TC SOLUTION THROUGH TAU 48, THEN MORE CLOSELY THE
CONSENSUS MEAN THEREAFTER. DUE TO THE VERY LARGE SPREAD OF THE
INTENSITY GUIDANCE, THERE IS OVERALL LOW CONFIDENCE IN THE JTWC
FORECAST.     

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: LOW
   INTENSITY 72-120 HR: LOW//
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