WDPN31 PGTW 180900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 18W (JELAWAT)
WARNING NR 006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 7.2N 125.9E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 393 NM WEST-NORTHWEST OF SONSOROL
   MOVEMENT PAST 6 HOURS: WESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 0 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS CONTINUED
DEEP, ALBEIT FRAGMENTED, CONVECTION AS TD JELAWAT MADE LANDFALL
INTO THE RUGGED MOUNTAINOUS TERRAIN OF MINDANAO, OBSCURING THE
LOW-LEVEL CIRCULATION (LLC). THE INITIAL POSITION IS PLACED WITH
MEDIUM CONFIDENCE USING EXTRAPOLATED AND SLOWED DOWN STORM MOTION
AND REFERENCED FROM THE WIND OBSERVATION FROM DAVAO, 17NM TO THE
WEST. THE INITIAL INTENSITY OF 25 KTS IS ALSO ASSESSED WITH MEDIUM
CONFIDENCE BASED ON RATE OF DECAY DUE TO THE INTERACTION OF JELAWAT
WITH SURROUNDING RUGGED TERRAIN, AND REFLECTS THE 6-HR DEGRADED
CONVECTIVE STRUCTURE. ANALYSIS INDICATES A HIGHLY UNFAVORABLE
ENVIRONMENT MOSTLY DUE TO THE FRICTIONAL EFFECTS OF THE RUGGED
TERRAIN AND THE LACK OF MOISTURE.

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: NO CURRENT ESTIMATE

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 5-10 KTS
   SST: OVER LAND
   OUTFLOW: MODERATE WESTWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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 18W WILL CONTINUE TO PROGRESS
WEST-NORTHWESTWARD THROUGHOUT THE REMAINDER OF THE FORECAST PERIOD
UNDER THE CONTINUED INFLUENCE OF THE WELL-ESTABLISHED STEERING
RIDGE TO THE NORTH. THE SYSTEM IS FORECAST TO MAINTAIN ITS CURRENT
INTENSITY, AT BEST, UP TO TAU 12 THEN DISSIPATE BY TAU 24, VERY
LIKELY SOONER, DUE TO PERSISTENT FRICTIONAL EFFECT OF THE TERRAIN
AND THE INCREASE OF VERTICAL WIND SHEAR.

MODEL DISCUSSION: TRACK FORECAST GUIDANCE DERIVED FROM THE
NUMERICAL MODEL SUITE IS IN TIGHT AGREEMENT OVER THE NEXT 24 HOURS
BUT GIVEN THE UNCERTAINTY AND THE WEAKENED STATE OF THE LLC, THERE
IS ONLY MEDIUM CONFIDENCE IN THE JTWC TRACK AND INTENSITY
FORECASTS.

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