WDPN32 PGTW 280900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 19W (JEBI)    
WARNING NR 008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.7N 142.9E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 892 NM SOUTH-SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
AS INDICATED IN ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI),
TROPICAL DEPRESSION (TD) 19W CONTINUES TO STRUGGLE, WITH DEEP
CONVECTION FLARING OVER THE EASTERN SEMICIRCLE OF A PARTIALLY-EXPOSED 
LOW-LEVEL CIRCULATION. UPPER-LEVEL CONDITIONS REMAIN MARGINALLY 
FAVORABLE DUE TO THE PRESENCE OF AN UPPER-LOW OVER AND TO THE WEST OF 
THE SYSTEM, WHICH IS PRODUCING UPPER-LEVEL CONVERGENCE AND SUBSIDENCE 
OVER THE WESTERN SEMICIRCLE THUS INHIBITING CONVECTIVE DEVELOPMENT. 
UPPER-LEVEL DIFFLUENCE IS CONFINED TO THE EASTWARD AND EQUATORWARD 
REGIONS OF THE SYSTEM, AIDING IN SUSTAINMENT OF DEEP CONVECTION OVER 
THOSE REGIONS. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE 
BASED ON THE MSI. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH 
MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK ESTIMATES AND THE CIMSS 
ADT ESTIMATE, CONSISTENT WITH THE WEAKENED STRUCTURE EVIDENT IN MSI.

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

CURRENT STEERING MECHANISM: LOW-LEVEL SUBTROPICAL RIDGE (STR)
POSITIONED TO THE NORTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 28 KTS AT 280530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE EASTWARD
   OTHER FACTORS: EXTENSIVE DRY AIR ASSOCIATED WITH THE UPPER-LEVEL
                  LOW 

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 19W IS FORECAST TO TRACK POLEWARD ALONG THE
SOUTHWESTERN AND WESTERN PERIPHERY OF THE STR THROUGH TAU 48, WITH
STEADY DEVELOPMENT AS THE UPPER-LOW GRADUALLY WEAKENS. AFTER TAU
48, THE SYSTEM WILL ROUND THE STR AND INTENSIFY TO TYPHOON
STRENGTH, DUE TO IMPROVING POLEWARD OUTFLOW ASSOCIATED WITH A
DEEPENING MAJOR SHORTWAVE TROUGH EXPECTED TO DIG OVER WESTERN
JAPAN. THE SYSTEM WILL EVENTUALLY TRACK INTO THE MIDLATITUDE
WESTERLIES NORTH OF THE STR AND COMMENCE EXTRA-TROPICAL TRANSITION
(ETT). TD 19W WILL COMPLETE ETT BY TAU 96 AS IT ACCELERATES
POLEWARD AND GAINS FRONTAL CHARACTERISTICS.     

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT
THROUGH THE FORECAST PERIOD, WITH GUIDANCE DIVERGING SIGNIFICANTLY
AFTER TAU 72 AS THE SYSTEM UNDERGOES EXTRA-TROPICAL TRANSITION. THE
280000Z ECMWF (EPS) AND GFS (GEFS) ENSEMBLES SHOW A SIMILAR SPREAD
AND MEDIUM UNCERTAINTY AS THE SYSTEM TRACKS EAST OF THE KANTO
PLAIN, WITH SOME POTENTIAL FOR THE SYSTEM TO TRACK CLOSER TO HONSHU
AS IT ROUNDS THE STR. GEFS SUPPORTS THE JTWC INTENSITY FORECAST,
SHOWING A STRONG TROPICAL STORM STRENGTH TO MINIMAL TYPHOON
STRENGTH SYSTEM IN THE MAJORITY OF ITS SOLUTIONS AFTER TAU 48.
ADDITIONALLY, THE 271200Z COAMPS-TC (GFS) ENSEMBLE SHOWS A HIGH
PROBABILITY (80-90 PERCENT) OF A WEAK TYPHOON DEVELOPING IN THE TAU
48 TO TAU 72 PERIOD AS REFLECTED IN THE JTWC INTENSITY FORECAST.   
 
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: LOW
   INTENSITY 72-120 HR: LOW//
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