WDPN31 PGTW 190900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 15W (PULASAN)      
WARNING NR 011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 29.6N 123.1E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 127 NM SOUTHEAST OF SHANGHAI, CHINA
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 22 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
EARLIER TODAY, TS 15W EXHIBITED A BRIEF, MISLEADING HISTORY OF A
TC-LIKE APPEARANCE ON ANIMATED MULTISPECTRAL SATELLITE IMAGERY DUE
TO FLARING CONVECTION AND DISPERSED OUTFLOW POLEWARD AND TO THE
EAST. HOWEVER, THE SYSTEM CONTINUES TO PREDOMINANTLY MEET THE
CHARACTERISTICS OF A MONSOON DEPRESSION, WHICH INCLUDE THE FOLLOWING 
ATTRIBUTES. ANIMATED ENHANCED INFRARED (EIR) AND MICROWAVE SATELLITE 
IMAGERY SHOWS A LOOSELY ORGANIZED BAND OF WEAK CONVECTIVE ELEMENTS ON 
THE EASTERN SEMICIRCLE AND A CLUSTER OF PULSING CONVECTION OVER A 
SHARP WAVE THAT EXTENDS NORTHEASTWARD FROM THE LOW PRESSURE CENTER. 
SCATTEROMETRY SHOWS A LOW-LEVEL WIND DISTRIBUTION OF LIGHT WINDS IN 
THE CORE AND A RADIUS OF MAXIMUM WINDS DISPLACED GREATER THAN 150 NM 
FROM THE PRESSURE CENTER. DUE TO THE EXPANSIVE CYCLONIC CIRCULATION, 
THE SYSTEM'S CENTER POSITION WAS RELOCATED FURTHER SOUTH IN THE AXIS 
OF SHARPEST TROUGHING. THIS SHARP WAVE EXTENDS BETWEEN THE PRESSURE 
CENTER AND A REGION OF GRADIENT-DRIVEN WIND MAXIMA APPROXIMATELY 150 
NM TO THE NORTHEAST, AS DEPICTED BY A 190346Z ASCAT IMAGE. 
ADDITIONALLY, EIR IMAGERY REVEALS A HALLMARK ABSENCE OF A CLOUD SYSTEM 
CENTER OVER THE SYSTEM'S CENTER POSITION. MOST NOTABLY, BECAUSE THERE 
IS NO EVIDENCE OF A CLOSED SURFACE CIRCULATION, THE SYSTEM IS 
DIFFICULT TO TRACK AND THE CURRENT POSITION IS PLACED WITH SIGNIFICANT
UNCERTAINTIES AND LOW CONFIDENCE. THE INITIAL INTENSITY IS ANALYZED
WITH MEDIUM CONFIDENCE DUE TO THE MAXIMUM WINDS DEPICTED ON
SCATTEROMETRY BEING LOCATED UNDERNEATH THE DEEP CONVECTION, AND THE
ASSESSED VALUE IS SUPPORTED BY A BLEND OF SUBJECTIVE AND OBJECTIVE 
INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: SHARP, DEEP-LAYERED SUBTROPICAL RIDGE
TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.0 - 30 KTS
   DEMS: T2.0 - 30 KTS
   CIMSS SATCON: 46 KTS AT 190530Z
   CIMSS ADT: 43 KTS AT 190600Z
   CIMSS AIDT: 43 KTS AT 190600Z
   CIMSS DPRINT: 30 KTS AT 190600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK EASTWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: SIGNIFICANT RELOCATION

FORECAST DISCUSSION: THE SYSTEM IS EXPECTED TO MAKE LANDFALL IN 
COASTAL CHINA NEAR SHANGHAI, WHILE THE ILL-DEFINED PATCH OF WIND 
MAXIMA WILL REMAIN JUST OFFSHORE. THE WEAK TD WILL SLOW DRASTICALLY OR 
STALL OVER LAND UNTIL GETTING PICKED UP BY AN APPROACHING TROUGH. THE 
WINDS ASSOCIATED WITH THE SYSTEM WILL DECREASE SLIGHTLY IN INTENSITY 
WHILE THE SYSTEM IS OVER LAND AT TAU 24, AND SUBSEQUENTLY RETURN TO A 
SIMILAR MAGNITUDE (35 KTS) DUE TO THE TIGHT PRESSURE GRADIENT BETWEEN 
THE TROUGH AND THE SHARP SUBTROPICAL STEERING RIDGE TO THE EAST. THE 
APPROACHING TROUGH IS ASSOCIATED WITH A COMBINED 150-KT JET MAXIMUM 
AND A TIGHT THERMAL GRADIENT THAT WILL INTRODUCE A BAROCLINIC ZONE 
BETWEEN TAU 24 AND TAU 36. AS THE TROUGH PICKS UP THE SYSTEM REMNANTS, 
IT WILL RE-EMERGE AND DEEPEN OVER THE EAST CHINA SEA AS A DEVELOPING 
STABLE WAVE, TO INCLUDE FRONTOGENESIS. AS THE PRESSURE CENTER TRACKS
QUICKLY EASTWARD, EXTRATROPICAL TRANSITION WILL OCCUR. THE DEVELOPING 
STABLE WAVE WILL TRACK THROUGH THE KOREA STRAIT, POSSIBLY MAKING 
LANDFALL NEAR JAPAN. THE LOCATION OF THE JETSTREAM OVER THE REPUBLIC 
OF KOREA WILL PREVENT THE SYSTEM FROM VENTURING NORTH; IF BY SLIM 
CHANCE IT DOES, IT CAN ONLY DO SO AS AN EXTRATROPICAL LOW. 
EXTRATROPICAL TRANSITION WILL BECOME COMPLETE BY TAU 72.

MODEL DISCUSSION: THE TRACK GUIDANCE IS IN GOOD AGREEMENT CONCERNING 
THE NORTHWESTWARD TRACK TOWARDS SHANGHAI AND THE SYSTEM MAKING 
LANDFALL OR REMAINING OFFSHORE. THE MODEL CONSENSUS DEPICTS A SHARPLY 
PIVOTING SYSTEM AS TD 15W IS PICKED UP AS A STABLE WAVE IN THE MID-
LATITUDES. THE UKMET ENSEMBLE MEAN TRACK TAKES THE SYSTEM OVER THE 
SOUTHERN REPUBLIC OF KOREA AS THE ONLY OUTLIER, WITH THE BULK OF THE 
RELIABLE GUIDANCE CARRYING THE TRACK FURTHER SOUTH OVER THE KOREA 
STRAIT OR SOUTHERN JAPAN. INTENSITY GUIDANCE HAS A 33-40 KT SPREAD AT 
TAU 48 DUE TO GRADIENT-DRIVEN WINDS ASSOCIATED WITH THE FRONTAL ZONE. 
INTENSITY GUIDANCE IS IN GOOD AGREEMENT THAT THE WINDS AROUND THE LOW 
WILL REMAIN AT 30-40 KNOTS THROUGHOUT THE TRANSITION PERIOD TO AN 
EXTRATROPICAL LOW BETWEEN TAU 48 AND TAU 72. BECAUSE OF THE 
SIGNIFICANT INITIAL UNCERTAINTIES WITH PLACEMENT, THE JTWC TRACK
FORECAST CARRIES A LOW CONFIDENCE, AND LARGE CHANGES IN BOTH CPA 
DISTANCE AND TIMING ARE POSSIBLE. FURTHERMORE, AS A RESULT OF THE
POSITIONING AND TRACK UNCERTAINTIES, THE INTENSITY FORECAST IS
PREDICTED WITH MEDIUM CONFIDENCE BECAUSE THE DURATION OVER LAND IS
NOT WELL-RESOLVED.

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