WDPN31 PGTW 220300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (WIPHA) WARNING NR 
015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.5N 106.8E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 59 NM EAST-SOUTHEAST OF HANOI, VIETNAM
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DEEP 
CONVECTION SHEARING TO THE SOUTHWEST, WITH A PARTIALLY-EXPOSED LOW-
LEVEL CIRCULATION. ANIMATED RADAR IMAGERY REVEALS A RAGGED BUT DEFINED 
LOW-LEVEL CIRCULATION CENTER (LLCC) LOCATED JUST OFF THE COAST OF 
VIETNAM, WITH CURVED DEEP CONVECTIVE BANDING PRIMARILY OVER THE 
SOUTHERN SEMICIRCLE. A 212243Z WSFM 37GHZ COLOR COMPOSITE MICROWAVE 
IMAGE DEPICTS A DEFINED LLCC, WITH SHALLOW BANDING WRAPPING AROUND THE 
CENTER. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON 
THE WSFM IMAGE AND ANIMATED RADAR IMAGERY. SEVERAL SURROUNDING SURFACE 
OBSERVATIONS ALSO SUPPORT THE INITIAL POSITION. ENVIRONMENTAL 
CONDITIONS ARE MARGINALLY UNFAVORABLE, WITH FRICTIONAL EFFECTS DUE TO 
LAND INTERACTION AND PERSISTENT NORTHEASTERLY VERTICAL WIND SHEAR OF 
30-35 KNOTS OFFSET BY MODERATE EQUATORWARD OUTFLOW AND WARM (30C) SST 
VALUES. THE INITIAL INTENSITY OF 45 KTS IS ASSESSED WITH MEDIUM 
CONFIDENCE BASED ON THE PGTW DVORAK ESTIMATES AND CIMSS OBJECTIVE 
ESTIMATES.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: LOW- TO MID-LEVEL SUBTROPICAL RIDGE
POSITIONED TO THE NORTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.5 - 55 KTS
   KNES: T3.5 - 55 KTS
   DEMS: T3.0 - 45 KTS
   CIMSS ADT: 45 KTS AT 220000Z
   CIMSS AIDT: 44 KTS AT 220000Z
   CIMSS D-PRINT: 44 KTS AT 220030Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 25-30 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: INTERACTION WITH LAND

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM (TS) 09W IS TRACKING WEST-
SOUTHWESTWARD ALONG THE SOUTHERN PERIPHERY OF THE SUBTROPICAL RIDGE 
AND IS FORECAST TO MAKE LANDFALL IN ABOUT 03 HOURS. AFTER MAKING 
LANDFALL, THE SYSTEM WILL TRACK INLAND ON A WESTWARD TRAJECTORY AND 
DISSIPATE RAPIDLY BY TAU 36.   

MODEL DISCUSSION: DETERMINISTIC GUIDANCE IN FAIR AGREEMENT, WITH A
75NM CROSS-TRACK SPREAD AT TAU 36. THE 211800Z GEFS AND 211200Z ECENS 
RUNS SUPPORT THE JTWC TRACK FORECAST BUT INDICATE A WIDER SPREAD OF
SOLUTIONS. GEFS SHOWS SOME SOLUTIONS TRACKING THE REMNANTS BACK OVER 
WATER WHILE ECENS SOLUTIONS ARE PREDOMINANTLY TRACKING THE SYSTEM 
WESTWARD. THEREFORE, THERE IS MEDIUM CONFIDENCE IN THE JTWC TRACK 
FORECAST. RELIABLE INTENSITY GUIDANCE IS IN GOOD AGREEMENT SUPPORTING 
THE STEADY WEAKENING TREND AS THE SYSTEM TRACKS INLAND. 

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