WDPN32 PGTW 240900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (NORU) WARNING NR 
010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.0N 126.8E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 346 NM EAST-NORTHEAST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A DEEP
CONVECTIVE CORE WITH A CENTRAL DENSE OVERCAST (CDO) FEATURE
OBSCURING THE LOW-LEVEL CIRCULATION CENTER (LLCC). THE ANIMATED
ENHANCED INFRARED IMAGERY (EIR) SHOWS INTENSE CONVECTIVE BURSTS ON
THE SOUTHERN SIDE OF THE LLCC WITH CLOUD TOP TEMPERATURES AS COLD
AS -82C (APPROXIMATELY 54,800 FEET). A 240700Z SSMIS 91GHZ IMAGE
REVEALS A 60NM DIAMETER CONVECTIVE CORE WITH THE LLCC POSITIONED
ALONG THE SOUTHERN SIDE OF THE CORE. BASED ON THIS IMAGE AND THE
MSI LOOP, THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE.
THE INITIAL INTENSITY IS ASSESSED AT 55 KNOTS BASED MULTIPLE AGENCY
DVORAK INTENSITY ESTIMATES AND THE ADVANCED DVORAK TECHNIQUE (ADT)
RAW OF T3.5-55KTS, LENDING HIGH CONFIDENCE. ENVIRONMENTAL
CONDITIONS ARE VERY FAVORABLE WITH MODERATE RADIAL OUTFLOW,
ENHANCED BY AN UPPER-LOW OVER THE CONTINUES MIGRATING WEST OVER THE
SOUTH CHINA SEA, AND LOW VERTICAL WIND SHEAR (VWS).

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF THE DEEP-LAYERED
SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.5 - 55 KTS
   KNES: T4.0 - 65 KTS
   CIMSS SATCON: 50 KTS AT 240428Z
   CIMSS ADT: 49 KTS AT 240540Z

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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 WILL CONTINUE TRACKING TO THE
WEST-SOUTHWEST ALONG THE SOUTHWEST PERIPHERY OF THE STR THROUGH TAU
12, THEREAFTER, IT WILL TURN MORE WESTWARD, AFTER IT MAKES INITIAL
LANDFALL ON LUZON SHORTLY AFTER TAU 24. THE FAVORABLE CONDITIONS
AND IMPROVED RADIAL OUTFLOW ARE ALLOWING FURTHER DEVELOPMENT TO A
PEAK INTENSITY OF 75 KNOTS JUST BEFORE MAKING LANDFALL. AFTER THE
SYSTEM TRANSITS ACROSS LUZON, IT WILL DECREASE IN INTENSITY ONLY
SLIGHTLY BEFORE IT REEMERGES OVER THE VERY WARM WATERS OF THE SOUTH
CHINA SEA. SHORTLY AFTER MOVING OVER THE HIGH OCEAN HEAT CONTENT
REGION, TS 18W WILL QUICKLY INTENSIFY BACK TO TYPHOON STRENGTH
ALONG ITS WESTWARD TRACK TOWARDS VIETNAM AND SOUTHEAST ASIA. BY TAU
60, THERE EXISTS A HIGH LIKELIHOOD FOR RAPID INTENSIFICATION WITH
TS NORU. HOWEVER, PEAK INTENSITY IS EXPECTED TO REACH 90 KNOTS
BEFORE MAKING SECONDARY LANDFALL, NEAR DA NANG, VIETNAM. RAPID
WEAKENING WILL OCCUR AS THE SYSTEM TRACKS OVER SOUTHEAST ASIA.    

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT
THROUGH THE FORECAST PERIOD WITH A MERE 60NM TO 80NM SPREAD IN
SOLUTIONS FROM TAU 48 TO TAU 96 LENDING HIGH CONFIDENCE TO THE JTWC
FORECAST TRACK. RAPID INTENSIFICATION REMAINS A POSSIBILITY NEAR
TAU 72 THROUGH 96, JUST PRIOR TO LANDFALL. COAMPS-TC SHOWS A 20 TO
25 PERCENT PROBABILITY OF RI IN THE SOUTH CHINA SEA, WHICH IS MOST
LIKELY TO OCCUR BETWEEN 260600Z TO 270600Z PERIOD. HWRF SHOWS AN RI
POSSIBILITY OCCURRING BY TAU 72 REACHING A PEAK INTENSITY OF 100
KNOTS AT TAU 96, JUST AFTER THE SYSTEM MAKES LANDFALL, LIMITING THE
BELIEF IN THE HWRF RI. THEREFORE, THERE IS ONLY MEDIUM CONFIDENCE
WITH THE JTWC INTENSITY FORECAST. 

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