WDPN32 PGTW 200900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 10W (CEMPAKA) WARNING NR 008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.4N 112.3E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 119 NM WEST-SOUTHWEST OF HONG KONG
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 01 KTS
   SIGNIFICANT WAVE HEIGHT: 26 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS SPIRAL BANDS
OF DEEP CONVECTION THAT WRAP INTO AN OBSCURED LOW LEVEL CIRCULATION
CENTER (LLCC). ALTHOUGH THE STORM EYE FILLED IN THE MSI LOOP OVER
THE PAST 6 HOURS, AN EYE FEATURE IS STILL EVIDENT IN THE RAIN BANDS
DEPICTED IN THE COMPOSITE RADAR LOOP THAT LENDS HIGH CONFIDENCE IN
THE INITIAL POSITION. THE INITIAL INTENSITY IS ASSESSED AT 70 KTS
AND HEDGED BETWEEN MULTIAGENCY DVORAK CURRENT INTENSITY ESTIMATES OF
T4.0 (65 KTS, RJTD) AND T4.5 (77 KTS, PGTW AND KNES) THAT ARE ALL
LOWER THAN OBJECTIVE DVORAK AND SATCON ESTIMATES.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF DEEP LAYER STR
POSITIONED TO THE NORTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T4.0 - 65 KTS
   KNES: T4.5 - 77 KTS
   CIMSS SATCON: 84 KTS AT 192318Z
   CIMSS ADT: 97 KTS AT 200540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: TY CEMPAKA WILL MAKE LANDFALL BY TAU 12
APPROXIMATELY 130 NM WEST-SOUTHWEST OF HONG KONG. AFTER LANDFALL,
THE SYSTEM WILL BEGIN TO WEAKEN RAPIDLY DUE TO INTERACTION WITH THE
UNDERLYING TERRAIN. AN INCOMING, MIDLATITUDE TROUGH WILL BEGIN TO
WEAKEN THE STEERING RIDGE AFTER THIS TIME AND THE WEAKENED TY
CEMPAKA WILL BEGIN AN EQUATORWARD TRACK AS A RESULT AFTER TAU 36
ALONG AN EXTENSION OF A RIDGE TO THE WEST. TY CEMPAKA WILL THEN
RENTER THE WARM WATERS OF THE SOUTH CHINA SEA WHEREUPON IT WILL
GRADUALLY INTENSIFY TO 35 KTS BY TAU 72. THEREAFTER THE SYSTEM WILL
BEGIN TO TRACK INITIALLY EASTWARD AND THEN EAST-NORTHEASTWARD
THROUGH THE REMAINDER OF THE FORECAST PERIOD AS THE NEAR EQUATORIAL
RIDGE POSITIONED TO THE SOUTH BECOMES THE DOMINANT STEERING
MECHANISM. DESPITE CONTINUE WARM SST, TY CEMPAKE WILL STRUGGLE TO
INTENSIFY FURTHER DUE TO TERRAIN INTERACTION WITH HAINAN AND
UNFAVORABLE (GREATER THAN 25 KTS) VERTICAL WIND SHEAR. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK AND INTENSITY GUIDANCE IS
IN TIGHT AGREEMENT THROUGH TAU 36, HOWEVER THEY DIVERGE THEREAFTER
DUE TO THE TIMING OF THE INTERACTION BETWEEN THE INCOMING
MIDLATITUDE TROUGH AND THE STEERING RIDGE. DESPITE THIS DIVERGENCE
IN MODEL TRACKS, ALL MEMBER OF THE JTWC MULTI-MODEL CONSENSUS AGREE
ON THE SOUTHWARD RECURVE SCENARIO WITH SUBSEQUENT RE-ENTRY INTO THE
SOUTH CHINA SEA AND FINAL EAST TO EAST-NORTHEASTWARD TRACK. THE
JTWC FORECAST TRACK IS PLACED ALONG THE MULT-MODEL CONSENSUS DUE TO
THE OVERALL AGREEMENT IN TRACK GUIDANCE. 

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