WDPN31 PGTW 181500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 17W (SEVENTEEN) 
WARNING NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.1N 107.3E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 95 NM SOUTHEAST OF HANOI, VIETNAM
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED PROXY VISIBLE (PROXYVIS) DEPICTS A RELATIVELY COMPACT LOW
LEVEL CIRCULATION CENTER (LLCC), NOW DEVOID OF SIGNIFICANT
CONVECTION, AS THE EARLIER BURST IN CONVECTIVE ACTIVITY HAS
COMPLETELY COLLAPSED OVER THE LAST COUPLE OF HOURS. A 181131Z GMI
89GHZ MICROWAVE IMAGE REVEALED SHALLOW BANDING FEATURES WRAPPING
INTO A WEAKLY DEFINED LLCC AND SPOTTY DEEP CONVECTION IN A LINEAR
NORTH-SOUTH BAND ALONG THE COAST OF VIETNAM. ANIMATED RADAR DATA
FROM VIETNAM SHOWS AN ARC OF MODERATE CONVECTION EXTENDING ALONG
THE COASTLINE FROM THE VIETNAM-CHINA BORDER TO NEAR HAIPHONG WHERE
IT CURVES OUT TO SEA TO THE SOUTHWEST OF THE LLCC. SURFACE WINDS
FROM BACH LONG VY REMAIN LIGHT (10 KTS) FROM THE SOUTH-SOUTHEAST
BUT THE STATION IS POSITIONED INSIDE THE CORE OF THE SYSTEM AND
HIGHER WINDS ARE LIKELY LOCATED BETWEEN THE STATION AND HAINAN
ISLAND. ANIMATED WATER VAPOR IMAGERY SHOW AN UPPER-LEVEL
ANTICYCLONE OVER SOUTHERN CHINA WHICH IS IMPARTING EASTERLY WINDS
ALOFT OVER TD 17W AND PUSHING THE CONVECTION OFF TO THE WEST. THE
INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE GMI
IMAGE AND THE RADAR DATA. THE INITIAL INTENSITY IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON THE GENERAL AGREEMENT BETWEEN THE
SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES NOTED BELOW.
ENVIRONMENTAL CONDITIONS ARE MARGINAL, WITH VERY WARM SSTS AND
MODERATE OUTFLOW ALOFT OFFSET BY THE PERSISTENT EASTERLY SHEAR AS
WELL AS PROXIMITY TO LAND.

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

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST NEAR SHANGHAI. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T1.5 - 25 KTS
   DEMS: T1.5 - 25 KTS
   CIMSS ADT: 28 KTS AT 181130Z
   CIMSS AIDT: 30 KTS AT 181130Z
   CIMSS D-MINT: 29 KTS AT 181128Z
   CIMSS D-PRINT: 29 KTS AT 181200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE WESTWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 17W IS FORECAST TO CONTINUE TRACKING
NORTHWARD ALONG THE SOUTHWESTERN PERIPHERY OF THE STR TO THE
NORTHEAST THROUGH THE FORECAST PERIOD. THE SYSTEM IS NOT EXPECTED
TO INTENSIFY PRIOR TO MAKE LANDFALL, WHICH IS EXPECTED TO OCCUR IN
THE VICINITY OF HA LONG, VIETNAM WITHIN THE NEXT 6 HOURS. TD 17W
WILL STEADILY WEAKEN AFTER MAKING LANDFALL AND ULTIMATELY DISSIPATE
WITH THE NEXT 24 HOURS OVER FAR-SOUTHERN CHINA.  

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN STRONG
AGREEMENT THAT TD 17W WILL FOLLOW A NORTHWARD TRACK THROUGH THE
FORECAST PERIOD AND THE JTWC FORECAST IS POSITIONED NEAR THE
CONSENSUS MEAN WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS ALSO IN
GOOD AGREEMENT, WITH ALL MODELS SHOWING A FLAT INTENSITY TREND TO
TAU 12, FOLLOWED BY RAPID WEAKENING THROUGH DISSIPATION BY TAU 24. 


FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: HIGH//
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