WDPN31 PGTW 070300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (CONSON) WARNING NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.9N 124.3E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 252 NM SOUTHEAST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TS 18W WEAKENED SLIGHTLY OVER THE PAST SIX HOURS AS IT TRACKED OVER 
MASBATE ISLAND. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY AND A 
062230Z SSMIS 91GHZ MICROWAVE IMAGE REVEALS SPIRAL BANDING WRAPPING 
INTO A RAGGED LOW-LEVEL CIRCULATION CENTER. THE INITIAL POSITION IS 
PLACED WITH MEDIUM CONFIDENCE BASED THIS SSMIS IMAGE. THE INITIAL 
INTENSITY OF 55 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED THE 
PGTW AND KNES DVORAK ESTIMATES AND THE CIMSS ADT ESTIMATE. THE UPPER-
LEVEL ENVIRONMENT IS FAVORABLE WITH RADIAL OUTFLOW ENHANCED BY THE 
TUTT TO THE NORTHEAST AND ROBUST EQUATORWARD OUTFLOW AS WELL AS LOW 
VERTICAL WIND SHEAR.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
POSITIONED OVER SOUTHEASTERN CHINA AND THE EAST CHINA SEA. WEAK STR
TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   CIMSS ADT: 57 KTS AT 062340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE RADIAL

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: TS 18W IS EXPECTED TO INTENSIFY SLIGHTLY TO
60 KNOTS AS IT TRACKS NORTHWESTWARD OVER THE WARM WATERS OF THE INNER
SEAS, HOWEVER, INTERACTION WITH LAND WILL LIKELY LIMIT DEVELOPMENT.
AFTER TAU 36, THE SYSTEM SHOULD TURN WEST-NORTHWESTWARD AS THE STR
TO THE NORTH BECOMES THE DOMINANT STEERING MECHANISM AND WEAKEN
DUE TO LAND INTERACTION. AFTER EMERGING OVER THE SOUTH CHINA SEA NEAR
TAU 48, TS 18W IS EXPECTED TO INTENSIFY STEADILY TO A PEAK OF 80
KNOTS UNDER GENERALLY FAVORABLE CONDITIONS AS IT TRACKS WEST-
NORTHWESTWARD TOWARD HAINAN ISLAND.

MODEL DISCUSSION: NUMERICAL TRACK GUIDANCE REMAINS IN GOOD AGREEMENT 
WITH A SPREAD RANGING FROM 100NM TO 150NM AFTER TAU 48 LENDING HIGH 
CONFIDENCE TO THE JTWC FORECAST TRACK. THE 061200Z ECMWF ENSEMBLE 
INDICATES A HIGH PROBABILITY OF THIS SCENARIO WITH A TRACK LIKELY 
OVER HAINAN ISLAND. THERE IS MEDIUM CONFIDENCE IN THE INTENSITY 
FORECAST THROUGH TAU 72 DUE TO THE EARLY TRACK OVER THE INNER SEAS, 
WHICH MAY ALLOW A MODEST INCREASE IN INTENSITY, AND LOW CONFIDENCE 
AFTER THE SYSTEM EMERGES BACK OVER WATER WITH SIGNIFICANT SPREAD IN 
THE INTENSITY GUIDANCE. THE JTWC INTENSITY FORECAST IS ALIGNED 
CLOSELY WITH THE INTENSITY CONSENSUS (ICNW) THROUGH THE FORECAST 
PERIOD.  

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: HIGH
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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