WDPN32 PGTW 210900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 10W (CEMPAKA) 
WARNING NR 012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.1N 110.9E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 184 NM WEST OF HONG KONG
   MOVEMENT PAST 6 HOURS: WESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 0 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS THE LOW-LEVEL CENTER
(LLC) MOVING WESTWARD OVER SOUTHERN CHINA. CONVECTIVE COVERAGE HAS
DECLINED OVER THE PAST SIX HOURS, BUT THE SURFACE WIND FIELD
REMAINS WELL-DEFINED. THE INITIAL INTENSITY IS LOWERED TO 25 KT
BASED ON CONTINUED DEGRADATION OF SATELLITE PRESENTATION OVER LAND
AND A LACK OF SIGNIFICANT WIND REPORTS FROM GROUND STATIONS.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: WEAK MID-LEVEL RIDGING TO THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: OVER LAND
   OUTFLOW: WEAK EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: DISSIPATION BY 96 HOURS IS NOW
FORECAST AS 10W LOOPS EASTWARD ACROSS HAINAN AND INTO THE SOUTH
CHINA SEA.

FORECAST DISCUSSION: TROPICAL DEPRESSION (TD) 10W (CEMPAKA) IS
EXPECTED TO TRACK WESTWARD FOR THE NEXT 24 HOURS OVER SOUTHERN
CHINA, THEN TURN SOUTHWARD INTO THE GULF OF TONKIN BY 36-48 HOURS
AS NORTHERLY FLOW ON THE WESTERN SIDE OF TYPHOON 09W BEGINS TO
ALTER THE DEEP-LAYER STEERING FLOW. A LOOPING TRACK SOUTHEASTWARD
AND THEN EASTWARD NEAR HAINAN IS EXPECTED DURING THE 48-96 HOUR
PERIOD AS CEMPAKA BECOMES EMBEDDED IN THE MONSOONAL WESTERLIES
ACROSS THE SOUTH CHINA SEA. SOME HIGH-RESOLUTION NUMERICAL MODEL
GUIDANCE, SUCH AS HWRF, COAMPS-TC, AND A FRACTION OF ECMWF ENSEMBLE
MEMBERS SUGGESTS THAT TD 10W WILL REMAIN A COHERENT CIRCULATION
OVER THE GULF OF TONKIN AND REGAIN SOME STRENGTH. THE JTWC
INTENSITY FORECAST RETAINS THIS SCENARIO AND FORECASTS
REINTENSIFICATION TO 35 KT BY 48 HOURS. THEREAFTER, AS CEMPAKA
BECOMES EMBEDDED IN THE BRISK MONSOONAL WESTERLIES, HIGH VERTICAL
SHEAR IS EXPECTED TO QUICKLY CAUSE DISSIPATION AS THE CIRCULATION
OPENS UP IN MOST MODEL GUIDANCE. IT IS ALSO POSSIBLE THAT TD 10W
DISSIPATES EARLIER IF IT IS UNABLE TO REINTENSIFY OVER THE GULF OF
TONKIN, A SCENARIO SHOWN BY THE GFS AND ECMWF. THE INTENSITY
FORECAST IS THUS OF ONLY MEDIUM CONFIDENCE. THE TRACK FORECAST
CONFIDENCE BECOMES LOW AFTER 72 HOURS, AS ALONG-TRACK SPREAD
INCREASES MARKEDLY DEPENDING ON WHEN THE SYSTEM BECOMES EMBEDDED IN
THE BRISK LOW-LEVEL WESTERLIES.

MODEL DISCUSSION: THE JTWC TRACK FORECAST GENERALLY FOLLOWS A BLEND
OF THE ECMWF ENSEMBLE, HWRF, COAMPS-TC AND THE GFS ENSEMBLE. THE
INTENSITY FORECAST IS BASED ON HWRF, COAMPS-TC, AND THE ECMWF
ENSEMBLE.

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