WDPN31 PGTW 230300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W (MA-ON)       
WARNING NR 007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.0N 122.6E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 184 NM NORTHEAST OF SUBIC, PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI)  SHOWS A MEDIUM-SIZED 
SYSTEM WITH A FAIRLY SYMMETRICAL CENTRAL CONVECTION THAT HAS DEEPENED 
FURTHER OVER THE LAST SIX HOURS. FEEDER BANDS FROM THE WESTERN TO 
SOUTHERN PERIPHERIES HAVE WRAPPED TIGHTER INTO THE LOW LEVEL 
CIRCULATION CENTER. THE INITIAL POSITION IS PLACED WITH MEDIUM 
CONFIDENCE BASED ON LOW CLOUD TRACING USING THE MSI LOOP AND 
EXTRAPOLATION FROM SURFACE WIND OBSERVATIONS ALONG THE EAST AND NORTH 
COASTS OF LUZON. THE INITIAL INTENSITY IS INCREASED TO 60 KNOTS, 
SLIGHTLY ABOVE THE AGENCY FIXES AND REFLECTS THE 6-HR CONVECTIVE 
IMPROVEMENT. THE ENVIRONMENT REMAINS FAVORABLE OVER THE PHILIPPINE 
SEA WITH WARM SST AND STRONG EQUATORWARD OUTFLOW OFFSETTING THE 
MODERATE VWS.

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.5 - 55 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: TS MA-ON WILL MAKE LANDFALL NEAR PALANAN,
ISABELA, PHILIPPINES, DRAG ACROSS LUZON AND EXIT INTO THE SOUTH
CHINA SEA VIA LAOAG JUST AFTER TAU 12. SHORTLY AFTER TAU 48, TS 10W
WILL MAKE A SECONDARY AND FINAL LANDFALL SOUTHWEST OF HONG KONG AND
TRACK INLAND ALONG THE VIETNAM-CHINA BORDER. LAND INTERACTION WILL
WEAKEN THE SYSTEM SLIGHTLY; HOWEVER, AFTER EXITING INTO THE SOUTH
CHINA SEA, THE WARMER SSTS WILL HELP FUEL A SECONDARY INTENSIFICATION 
TO A PEAK OF 70KTS PRIOR TO LANDFALL INTO CHINA. THE RUGGED SOUTHERN 
CHINA TERRAIN WILL THEN RAPIDLY ERODE THE SYSTEM TO DISSIPATION 
BEFORE TAU 96. 

MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT WITH
GRADUAL AND EVEN SPREADING TO 180NM BY TAU 96. HOWEVER, DUE TO THE
VARIABILITY OF LAND CROSSINGS, THERE IS ONLY MEDIUM CONFIDENCE IN
THE JTWC TRACK FORECAST THAT IS LAID CLOSE TO THE MODEL CONSENSUS.
THERE IS ALSO MEDIUM CONFIDENCE IN THE INTENSITY FORECAST UP TO AU
48. AFTERWARD, LOW CONFIDENCE DUE TO THE UNCERTAINTY OF LAND
INTERACTION ON A DECAYING CYCLONE. 

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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