WDPN31 PGTW 140300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 28W (RAI) WARNING NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 7.4N 136.9E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 149 NM EAST OF KOROR
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 18 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A CENTRAL
COLD COVER (CCC) WITH A SINGLE, NON-ROTATING UPDRAFT AND
OVERSHOOTING TOPS WITH CLOUD TOP TEMPERATURE NEAR -100C. THE
HORIZONTAL EXTENT OF THE CIRRUS SHIELD HAS DECREASED AND BECOME
ELONGATED NORTH TO SOUTH OVER THE PAST FEW HOURS. UNFORTUNATELY,
THERE HAS BEEN ONLY ONE GOOD MICROWAVE PASS IN THE PAST 18 HOURS,
FROM 131946Z AND THUS THERE IS LITTLE IN THE WAY TO REFINE THE
INITIAL POSITION, WHICH IS CURRENTLY PLACED UNDER THE CENTER OF THE
MAIN UPDRAFT AS SEEN IN VISIBLE IMAGERY, WITH LOW CONFIDENCE.
FORWARD TRACK SPEED HAS INCREASED AS WELL, BUT THIS IS ALSO VERY
LOW CONFIDENCE DUE TO THE UNCERTAINTY IN THE INITIAL POSITION. ALL
AGENCIES ARE USING THE CCC SCENE TYPE IN THEIR DVORAK ANALYSIS,
THUS THE CURRENT INTENSITIES ARE BEING HELD AT T3.0 OR T3.5 DUE TO
THE ASSOCIATED CONSTRAINTS. THE INITIAL INTENSITY HAS BEEN
INCREASED TO 50 KNOTS, RIGHT AT THE MEAN BETWEEN T3.0 AND T3.5.
ADDITIONALLY, A PARTIAL SCATTEROMETER PASS FROM 132236Z SHOWED
40-45 KNOT WIND BARBS ON THE WESTERN SIDE OF THE CIRCULATION,
PROVIDING ADDITIONAL SUPPORT TO AN BUMP UP IN THE INTENSITY.

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T3.5 - 55 KTS
   KNES: T3.0 - 45 KTS
   CIMSS ADT: 55 KTS AT 132340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   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: TS 28W CONTINUES TO TRACK WEST-NORTHWEST ALONG
THE SOUTHERN SIDE OF THE DEEP STR ENTRENCHED TO THE NORTH. THE
SYSTEM IS EXPECTED TO CONTINUE THIS TRACK MOTION THROUGH THE
DURATION OF THE FORECAST PERIOD, WITH A SLIGHT POLEWARD TURN BY TAU
120. TS 28W IS FORECAST TO ENTER THE SURIGAO STRAIT REGION AROUND
TAU 60, THEN TRACK ACROSS THE VISAYAN ISLANDS, INTO THE SULU SEA
AND ULTIMATELY INTO THE SOUTH CHINA SEA BY TAU 96. AS DISCUSSED IN
THE PREVIOUS FORECAST DISCUSSION, HWRF AND GFS MODEL CROSS-SECTIONS
CONTINUE TO DEPICT TWO DISTINCT POTENTIAL VORTICITY (PV) MAXIMA,
ALONG AN EAST-WEST AXIS. BASED ON THESE CROSS-SECTIONS, THE WESTERN
PV MAX IS ASSOCIATED WITH THE STRONG UPDRAFT, WITH THE OTHER
SLIGHTLY OFFSET TO THE EAST. THE MODELS SHOW THESE TWO PV MAXES
CLOSER THAN THEY WERE SIX HOURS AGO AND DO INDICATE A MERGER INTO
ONE SINGULAR CORE WITHIN THE NEXT SIX TO TWELVE HOURS. THUS THE
INTENSITY FORECAST, WHILE STILL INCREASING TO 60 KNOTS IN TWELVE
HOURS, IS RELATIVELY SLOW UNTIL THE CORE CONSOLIDATES FURTHER. ONCE
THIS OCCURS HOWEVER, THE INTENSITY GUIDANCE SUGGESTS RAPID
INTENSIFICATION BETWEEN TAU 12 AND TAU 48. THE PEAK CURRENTLY IS
SET AT 95 KNOTS AT TAU 48, HOWEVER FORECAST LIMITATIONS PRECLUDE A
SETTING A TAU 60 FORECAST POINT, BUT THE ACTUAL PEAK IS EXPECTED TO
REACH 100 KNOTS NEAR TAU 60, AS THE SYSTEM NEARS THE SURIGAO
STRAIT. THE SYSTEM WILL WEAKEN SLIGHTLY AS IT CROSSES THE VISAYANS,
THEN REINTENSIFY AS IT MOVES OVER THE OPEN WATERS OF THE SOUTH
CHINA SEA AFTER TAU 96.  

MODEL DISCUSSION: TRACK GUIDANCE REMAINS IN GOOD AGREEMENT WITH A
100NM SPREAD AT TAU 72, INCREASING TO 220NM AT TAU 120. THERE IS
SOME ALONG-TRACK SPREAD THROUGH TAU 72, PARTICULARLY BETWEEN THE
HWRF AND THE REMAINDER OF THE GUIDANCE, WITH THE HWRF BEING A FEW
KNOTS SLOWER. THE JTWC FORECAST REMAINS CONSISTENT WITH THE
PREVIOUS FORECAST AND LIES ON THE NORTHERN EDGE OF THE PREDOMINANT
GUIDANCE ENVELOPE THROUGH THE FORECAST PERIOD WITH HIGH CONFIDENCE
THROUGH TAU 72 AND MEDIUM CONFIDENCE THEREAFTER. INTENSITY GUIDANCE
IS STILL MIXED, THOUGH IN BETTER AGREEMENT THAN THE PREVIOUS RUN.
THE RAPID INTENSIFICATION AIDS CONTINUE TO BE TRIGGERED, WITH RIPA
PEAKING AT 105 KNOTS AT TAU 48. THE REMAINDER OF THE GUIDANCE PEAKS
NEAR TAU 60 BETWEEN 65 AND 90 KNOTS. ALL GUIDANCE SHOWS A WEAKENING
WHILE CROSSING THE PHILIPPINES, FOLLOWED BY STRENGTHENING IN THE
SOUTH CHINA SEA. THE JTWC INTENSITY FORECAST IS SLOWER THAN THE RI
GUIDANCE THROUGH TAU 12, THEN TRACKS THE RIPA GUIDANCE THROUGH TAU
48 AND THE CONSENSUS MEAN THEREAFTER. CONFIDENCE IS MEDIUM THROUGH
TAU 72, AND LOW THEREAFTER. 

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