WDPN31 PGTW 040300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (YINXING) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.1N 133.3E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 733 NM EAST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM 24W (YINXING) WITH IMPROVED CONVECTIVE BANDING TIGHTLY
WRAPPING INTO THE OBSCURED LOW-LEVEL CIRCULATION CENTER (LLCC).
OUTFLOW HAS ALSO MARKEDLY IMPROVED OVER THE PAST 6 HOURS WITH
CIRRUS FILAMENTS EXPANDING OUT FROM THE SYSTEM. ENVIRONMENTAL
ANALYSIS INDICATES A FAVORABLE ENVIRONMENT FOR FURTHER
INTENSIFICATION CHARACTERIZED BY MODERATE POLEWARD AND EQUATORWARD
OUTFLOW ALOFT, LOW (5-10 KTS) VERTICAL WIND SHEAR, AND WARM (29-30
C) SEA SURFACE TEMPERATURES. THE INITIAL POSITION IS PLACED WITH
LOW CONFIDENCE BASED ON THE OBSCURED LLCC IN THE ANIMATED MSI. THE
INITIAL INTENSITY OF 50 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON AGENCY DVORAK AND OBJECTIVE INTENSITY ESTIMATES LISTED
BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T3.5 - 55 KTS
   KNES: T3.0 - 45 KTS
   CIMSS ADT: 51 KTS AT 032350Z
   CIMSS AIDT: 43 KTS AT 032350z
   CIMSS DPRINT: 55 KTS AT 040000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: 24W IS FORECAST TO CONTINUE TRACKING
NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF THE STR
POSITIONED TO THE NORTHEAST THROUGH TAU 48. NEAR TAU 48, A TROUGH
IS EXPECTED TO PROPAGATE THROUGH AND BREAK DOWN THE RIDGE. THIS
WILL CAUSE 24W TO BE PLACED WITHIN A WEAK STEERING ENVIRONMENT AND
DRIFT SLOWLY WESTWARD THROUGH TAU 72. AFTER TAU 72, A RIDGE WILL
BUILD OVER SOUTHERN CHINA AND TAKE OVER AS THE PRIMARY STEERING
MECHANISM, PULLING THE SYSTEM FURTHER WESTWARD AT AN INCREASED
PACE. 24W IS FORECAST TO CONTINUE TRACKING WESTWARD INTO THE SOUTH
CHINA SEA, JUST NORTH OF LUZON, THROUGH THE REMAINDER OF THE
FORECAST PERIOD. REGARDING INTENSITY, 24W IS FORECAST TO CONTINUE
INTENSIFYING OVER THE NEXT 12 HOURS. THEN STARTING AT TAU 12, RAPID
INTENSIFICATION WILL ENSUE THROUGH TAU 36 IN RESPONSE TO THE
GREATLY INCREASED POLEWARD OUTFLOW AND LOW VERTICAL WIND SHEAR. A
PEAK INTENSITY OF 95 KTS IS FORECAST TO OCCUR AROUND TAU 48, BUT
THEN WILL HALT FURTHER INTENSIFICATION DUE TO A COLD POCKET OF SEA
SURFACE TEMPERATURES TO THE NORTHEAST OF LUZON. ADDITIONALLY,
STARTING AT TAU 72, 24W WILL INTERACT WITH A COLD SURGE FLOWING
PAST TAIWAN AND INTO THE SOUTH CHINA SEA. THE COLD SURGE WILL
INTRODUCE DRY AIR TO THE SYSTEM AND OVERALL DEGRADE THE
ENVIRONMENT. A WEAKENING TREND IS THEN FORECAST TO PERSIST THROUGH
THE REMAINDER OF THE FORECAST PERIOD AS THE SYSTEM TRACKS FURTHER
INTO THE SOUTH CHINA SEA.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
CONCERNING THE TRACK OF 24W THROUGH TAU 48 WITH A 125 NM
CROSS-TRACK SPREAD AT THAT TIME. AFTER TAU 48, MODELS BEGIN TO
DIVERGE DUE TO DIFFERENCES IN HOW AND WHEN THE RIDGE OVER SOUTHERN
CHINA EXTENDS EASTWARD. MODELS HAVE REDUCED SPREAD SINCE THE
PREVIOUS MODEL RUN THOUGH, AND THE MAJORITY OF MODELS EITHER TRACK
THE SYSTEM ALONG THE NORTHERN COAST OF LUZON OR THROUGH THE CENTRAL
LUZON STRAIT. HOWEVER, THE ECMWF ENSEMBLE CONTINUES TO SHOW MEMBERS
STALLING NORTHEAST OF LUZON AND THEN RECURVING POLEWARD, SO THAT
SOLUTION IS STILL NOT OUT OF THE QUESTION. NEVERTHELESS, THE JTWC
TRACK FORECAST IS PLACED CLOSE TO CONSENSUS WITH OVERALL MEDIUM
CONFIDENCE. INTENSITY GUIDANCE IS IN MODERATE AGREEMENT WITH RAPID
INTENSIFICATION AIDS CONTINUING TO TRIGGER. THE COAMPS-TC ENSEMBLE
GUIDANCE ALSO HAS OVER AN 80 PERCENT CHANCE OF RI FROM TAU 6 TO 36.
THE JTWC INTENSITY FORECAST FOLLOWS WHAT THE RI AIDS SUGGEST WITH
RI FROM TAU 12 TO 36 (60 TO 90 KTS). AS THE SYSTEM TRACKS PAST
LUZON, DEPENDING ON HOW CLOSE TO LAND THE SYSTEM TRACKS, THERE
COULD BE A LARGE CHANGE IN INTENSITIES AT THAT TIME. 

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