WDPN31 PGTW 051500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 07W (SEVEN) 
WARNING NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.2N 121.8E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 294 NM SOUTH OF TAIPEI, TAIWAN
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 17 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS FLARING 
CONVECTION OVER THE WESTERN SEMICIRCLE OF A PARTIALLY EXPOSED LOW 
LEVEL CIRCULATION CENTER (LLCC). A 051029Z SSMIS 91GHZ MICROWAVE 
IMAGE REVEALS A WEAKLY-DEFINED LLCC WITH A LINEAR AREA OF DEEP 
CONVECTION. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE 
BASED ON THE AFOREMENTIONED IMAGERY, HOWEVER, A 051250Z ASCAT-B 
BULLSEYE IMAGE RECEIVED JUST RECENTLY SHOWS A WELL-DEFINED, 
SYMMETRIC CIRCULATION WITH 25 TO 30 KNOT WINDS OVER ALL QUADRANTS 
EXCEPT THE SOUTH QUADRANT. THIS REPRESENTS THE BEST SURFACE WIND 
FIELD STRUCTURE THUS FAR IN THE SYSTEM'S LIFECYCLE. THE INITIAL 
INTENSITY OF 30 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE 
ASCAT DATA, THE KNES DVORAK ESTIMATE AND THE ADT ESTIMATE. THE 
ENVIRONMENT REMAINS FAVORABLE WITH MODERATE EQUATORWARD OUTFLOW, 
WARM SST AND LOW VERTICAL WIND SHEAR. POLEWARD OUTFLOW IS WEAK DUE 
TO A LACK OF A POLEWARD OUTFLOW MECHANISM.

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

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
ENTRENCHED TO THE NORTH AND NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 32 KTS AT 051140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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 07W IS FORECAST TO TRACK QUICKLY
NORTHWESTWARD THROUGH THE FORECAST PERIOD ALONG THE SOUTHWESTERN
PERIPHERY OF THE STRONG STR WITH LANDFALL OVER SOUTHEAST CHINA
NEAR TAU 24. TD 07W CONTINUES TO STRUGGLE GENERATING AND
MAINTAINING ORGANIZED DEEP CONVECTION DUE TO THE QUICK TRACK
SPEEDS AND WEAK NATURE OF THE LLCC. THE SYSTEM IS EXPECTED TO 
MAINTAIN INTENSITY AT 30 KNOTS THROUGH TAU 12. AFTER TAU 12, 
FAVORABLE CONDITIONS SHOULD DEGRADE WITH INCREASING VWS OF 25 KNOTS 
LEADING TO STEADY WEAKENING AND DISSIPATION OVER LAND BY TAU 36.  

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT 
THROUGH THE FORECAST PERIOD WITH A 40NM SPREAD IN SOLUTIONS AT TAU 
12 AND A 40NM SPREAD IN SOLUTIONS AT TAU 24 SO OVERALL HIGH 
CONFIDENCE IN THE TRACK FORECAST. THERE IS MEDIUM CONFIDENCE IN THE 
INTENSITY FORECAST WITH SOME UNCERTAINTY IN THE FORECAST INTENSITY 
NEAR TAU 12 AS THE SYSTEM TRANSITS SOUTH OF TAIWAN. HOWEVER, THIS 
FORECAST IS IN LINE WITH HWRF AND THE JTWC INTENSITY CONSENSUS 
GUIDANCE. 

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