WDPN31 PGTW 180300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 18W (JELAWAT) 
WARNING NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 7.1N 126.6E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 60 NM EAST OF DAVAO CITY, PHILIPPINES
   MOVEMENT PAST 6 HOURS: WESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 17 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS FLARING DEEP
CONVECTION TO THE WEST OF THE CIRCULATION CENTER AS ONSHORE FLOW
RUNS UP AGAINST THE MOUNTAINOUS TERRAIN OF MINDANAO. THE INITIAL
POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON 172207Z SSMIS
IMAGERY SHOWING A COMPACT LOW LEVEL CIRCULATION CENTER. THE INITIAL
INTENSITY OF 30 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON A
CONSENSUS OF SUBJECTIVE DVORAK FINAL INTENSITY VALUES FROM PGTW AND 
RJTD AND NEARBY OBSERVATIONS.

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

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE WESTWARD
   OTHER FACTORS: LAND INTERACTION

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TD 18W WILL TRACK GENERALLY WESTWARD
THROUGHOUT THE FORECAST PERIOD UNDER THE CONTINUED INFLUENCE OF THE
WELL-ENTRENCHED STEERING RIDGE TO THE NORTH. THE SYSTEM IS EXPECTED
TO WEAKEN STEADILY THROUGH THE NEXT 36 HOURS, PRIMARILY DUE TO
PASSAGE OVER THE RUGGED TERRAIN OF MINDANAO AND MODERATE TO HIGH
EASTERLY VERTICAL WIND SHEAR.

MODEL DISCUSSION: TRACK FORECAST GUIDANCE DERIVED FROM THE
NUMERICAL MODEL SUITE IS IN GOOD AGREEMENT, WITH SPREAD CONFINED TO
THE ALONG-TRACK DIRECTION INDICATIVE OF MINOR TRACK SPEED
DIFFERENCES. MODEL INTENSITY FORECASTS SUGGEST A FAIRLY STEADY
TREND IN INTENSITY, BUT THAT TREND IS ASSESSED AS UNLIKELY GIVEN
THE UNFAVORABLE CONDITIONS ANNOTATED IN THE FORECAST DISCUSSION
SECTION ABOVE.

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