WDPN32 PGTW 230900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 10W (CEMPAKA) 
WARNING NR 020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.7N 107.6E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 97 NM EAST OF HANOI, VIETNAM
   MOVEMENT PAST 6 HOURS: SOUTHWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 7 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS FLARING,
DISORGANIZED CONVECTION OBSCURING A WEAKLY-DEFINED LOW-LEVEL
CIRCULATION, THEREFORE, THE INITIAL POSITION IS PLACED WITH LOW
CONFIDENCE. ANIMATED RADAR IMAGERY REVEALS BROAD TURNING WITH WEAK
CONVECTIVE BANDING, AND SUGGESTS THE CENTER MAY BE TRACKING CLOSE
TO THE NORTHEAST VIETNAM COAST. HOWEVER, SURFACE OBSERVATIONS
INDICATE WEAK WINDS LESS THAN 10 KNOTS. A 230300Z ASCAT-C IMAGE
SHOWS A BAND OF 20-25 KNOT WESTERLIES TO THE SOUTH WITH 10-15 KNOT
WINDS NEAR THE CENTER. THE INITIAL INTENSITY OF 25 KTS IS ASSESSED
WITH LOW CONFIDENCE BASED ON THE PGTW DVORAK ESTIMATE AND THE ASCAT
DATA.

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

CURRENT STEERING MECHANISM: COMPETING STEERING ENVIRONMENT WITH
WEAK LOW-LEVEL SUBTROPICAL RIDGE TO THE NORTH AND WESTERLIES TO THE 
SOUTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   CIMSS ADT: 32 KTS AT 230540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK EQUATORWARD
   OTHER FACTORS: INTERACTION WITH LAND

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TD 10W CONTINUES TO STRUGGLE UNDER MODERATE
NORTHEASTERLY VERTICAL WIND SHEAR (VWS) AND IS EXPECTED TO TRACK
SOUTHWESTWARD TO SOUTHWARD WITHIN THE WEAK STEERING ENVIRONMENT
THROUGH TAU 12. AFTER TAU 12, THE SYSTEM WILL TURN EASTWARD UNDER
THE STEERING INFLUENCE OF THE LOW-LEVEL WESTERLIES AND SHOULD
DISSIPATE BY TAU 36 UNDER MARGINALLY FAVORABLE CONDITIONS DUE
PRIMARILY TO THE PERSISTENT VWS AND LAND INTERACTION. THIS SYSTEM
IS CLEARLY A BORDERLINE TD, AND THERE IS POTENTIAL FOR DISSIPATION
WITHIN THE NEXT 24 HOURS.   

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE SUPPORTS THE EASTWARD
TRACK CHANGE BUT DIFFERS ON THE TIMING OF THE TURN AND TRACK SPEEDS
THUS LOW CONFIDENCE IN THE JTWC FORECAST TRACK. INTENSITY GUIDANCE
ALSO SHOWS SOME UNCERTAINTY WITH A HWRF INDICATING INTENSIFICATION
TO 40 KNOTS IN THE NEXT 24 HOURS, WHICH IS ASSESSED AS UNLIKELY DUE
TO THE VWS. THE REMAINDER OF THE INTENSITY GUIDANCE INDICATES A
FLAT TREND OR SLIGHT WEAKENING. OVERALL, THERE IS MEDIUM CONFIDENCE
IN THE JTWC INTENSITY FORECAST. 

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