WDPN31 PGTW 062100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (CONSON) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.5N 124.9E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 294 NM SOUTHEAST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TS 18W HAS CONTINUED TO CONSOLIDATE WHILE TRACKING OVER THE
1500-2000 FOOT MOUNTAINS OF SOUTHERN SAMAR ISLAND. ANIMATED
ENHANCED INFRARED SATELLITE IMAGERY AND A 061659Z AMSR2 89GHZ
MICROWAVE IMAGE REVEAL SPIRAL BANDING OVER THE SOUTHERN SEMICIRCLE
WRAPPING INTO A COMPACT CORE. THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE BASED ON A SMALL MICROWAVE EYE FEATURE IN THE AMSR2
IMAGE. THE INITIAL INTENSITY OF 60 KTS IS ASSESSED WITH HIGH
CONFIDENCE BASED ON A PGTW 061430Z PRE-LANDFALL DVORAK ESTIMATE OF
T3.5 (55 KNOTS) AS WELL AS THE IMPROVED CONVECTIVE STRUCTURE. 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: NO CURRENT ESTIMATE
   RJTD: T3.0 - 45 KTS
   CIMSS SATCON: 62 KTS AT 0953Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: OVER LAND
   OUTFLOW: MODERATE RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   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 65
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 60, 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 60NM TO 80NM THROUGH THE
FORECAST PERIOD 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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