WDPN31 PGTW 240300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 28W (PABUK) WARNING 
NR 007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.4N 112.3E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 332 NM EAST OF HO CHI MINH CITY, VIETNAM
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY
EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH FLARING CONVECTION 
THROUGHOUT THE NORTHWESTERN QUADRANT. DESPITE THE OVERALL SIX-HOUR 
SOUTH-SOUTHWESTWARD TRACK MOTION, THE SYSTEM TEMPORARILY TURNED BACK 
TOWARDS THE NORTHEAST BEFORE BECOMING QUASI-STATIONARY OVER THE PAST 
FEW HOURS DUE TO COMPETING STEERING INFLUENCES IN THE MEAN LOW-LEVEL 
FLOW. ENVIRONMENTAL CONDITIONS REMAIN MARGINALLY SUPPORTIVE FOR 
MAINTAINING THE CURRENT INTENSITY OVER THE NEXT 24 HOURS, AFTER WHICH 
DRY AIR, COLDER SEA SURFACE TEMPERATURES AND INCREASING VERTICAL WIND 
SHEAR WILL CONTRIBUTE TOWARDS STEADY WEAKENING. THE INITIAL POSITION 
IS PLACED WITH HIGH CONFIDENCE BASED ON FULLY EXPOSED LLCC PRESENT IN 
THE MSI. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH HIGH 
CONFIDENCE BASED ON A COMBINATION OF AGENCY DVORAK ESTIMATES, AS WELL 
AS AUTOMATED INTENSITY AIDS LISTED BELOW.

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

CURRENT STEERING MECHANISM: COMPETING INFLUENCES OF THE 700 TO 850
MB MEAN LAYER FLOW AND THE NORTHEASTERLY SURGE 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T1.0 - 25 KTS
   KNES: T1.5 - 25 KTS
   CIMSS ADT: 31 KTS AT 232330Z
   CIMSS AIDT: 32 KTS AT 240030Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   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 PABUK IS FORECAST TO RESUME HEADING
WEST-SOUTHWESTWARD FOLLOWING A BRIEF PERIOD OF ERRATIC MOTION. NO 
FURTHER INTENSIFICATION IS FORECAST GIVEN THE MARGINAL ENVIRONMENTAL 
CONDITIONS, HOWEVER, ISOLATED AREAS OF 35 KT WINDS MAY BE EMBEDDED 
WITHIN THE COLD SURGE FLOW ALONG THE COAST OF VIETNAM. AS TD 28W 
CONTINUES TRACKING WEST AND THE ENVIRONMENTAL CONDITIONS BECOME LESS 
FAVORABLE, TD PABUK WILL START WEAKENING AND EVENTUALLY FULLY 
DISSIPATE SHORTLY AFTER MAKING LANDFALL, BY THE END OF THE CURRENT 
FORECAST PERIOD. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT IN
REGARDS TO THE TRACK FORECAST THROUGHOUT TAU 24, WITH THE CROSS-TRACK 
SPREAD OF 31 NM, EXPANDING TO 168 NM BY TAU 48. INCREASED UNCERTAINTY 
PAST THE INITIAL DAY IS ALSO EXHIBITED BY THE ALONG-TRACK SPREAD OF 
170 NM BY THE END OF THE FORECAST PERIOD. JTWC TRACK FORECAST IS LAID 
WITH MEDIUM CONFIDENCE, SLIGHTLY TO THE RIGHT OF THE MULTI-MODEL 
CONSENSUS HEDGING TOWARDS THE GFS AND ECMWF ENSEMBLE MODEL MEAN 
SOLUTIONS. INTENSITY GUIDANCE REMAINS CONSISTENT ACROSS THE MODELS, IN 
AGREEMENT WITH THE FORECAST.

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