WDPN32 PGTW 190900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W (CEMPAKA) WARNING 
NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.0N 113.0E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 103 NM SOUTHWEST OF HONG KONG
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 17 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A COMPACT,
CONSOLIDATING SYSTEM WITH TIGHTLY-CURVED BANDING WRAPPING INTO A
WELL-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC). A 190542Z AMSR2
MICROWAVE IMAGE REVEALS A MICROWAVE EYE FEATURE, WHICH SUPPORTS THE
THE INITIAL POSITION WITH HIGH CONFIDENCE. THE INITIAL INTENSITY OF
50 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE KNES AND PGTW
DVORAK ESTIMATES AS WELL AS THE ADT ESTIMATE OF 47 KNOTS (190810Z
ADT ESTIMATE NOW 49 KNOTS WITH WEAK EYE DEVELOPING IN VISIBLE
IMAGERY). ENVIRONMENTAL ANALYSIS INDICATES FAVORABLE CONDITIONS
WITH MODERATE POLEWARD AND EQUATORWARD OUTFLOW, LOW VERTICAL WIND
SHEAR AND WARM SST VALUES.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: LOW- TO MID-LEVEL SUBTROPICAL RIDGE
(STR) POSITIONED TO THE NORTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.5 - 35 KTS
   KNES: T3.0 - 45 KTS
   CIMSS ADT: 47 KTS AT 190550Z

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

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 10W IS FORECAST TO TRACK SLOWLY
WEST-NORTHWESTWARD THROUGH TAU 36 UNDER THE STEERING INFLUENCE OF
THE WEAK STR TO THE NORTH. AFTER TAU 36, THE SYSTEM WILL TRACK
WITHIN COMPETING STEERING INFLUENCES AND TURN SOUTHWESTWARD THROUGH
TAU 72. IN THE EXTENDED PERIOD, TS 10W WILL TURN SOUTHEASTWARD TO
EASTWARD UNDER THE STEERING INFLUENCE OF STRENGTHENING LOW-LEVEL
WESTERLY FLOW. IN GENERAL, THE NUMERICAL MODEL GUIDANCE SUPPORTS
THE FORECAST TRACK, HOWEVER, THERE IS A LARGE DEGREE OF SPREAD DUE
TO THE COMPLEX, EVOLVING SYNOPTIC STEERING ENVIRONMENT. TS 10W
SHOULD INTENSIFY QUICKLY TO A PEAK OF 65 KNOTS BY TAU 12 JUST
PRIOR TO LANDFALL WITH STEADY WEAKENING AS THE SYSTEM TRACKS OVER 
LAND. TS 10W WILL LIKELY RE-INTENSIFY NEAR TAU 120 AFTER REEMERGING 
BACK OVER WATER.  

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE SUPPORTS THE JTWC TRACK
FORECAST WITH LOW CONFIDENCE. CONFIDENCE IN THE JTWC INTENSITY
FORECAST IS MEDIUM WITH SOME UNCERTAINTY IN THE PEAK INTENSITY,
WHICH COULD BE SLIGHTLY HIGHER CONSIDERING THE COMPACT NATURE OF
THE SYSTEM AND THE TENDENCY FOR THESE TYPES OF SYSTEMS TO RAPIDLY
INTENSIFY. ADDITIONALLY, THERE IS ENOUGH UNCERTAINTY IN THE TRACK
AND THE POTENTIAL FOR A MORE PROLONGED TRACK OVER THE VERY WARM
WATER.   

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