WDPN32 PGTW 240300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (NORU)        
WARNING NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.4N 128.0E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 419 NM EAST-NORTHEAST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 19 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS AN IMPROVED
CONVECTIVE CORE WITH A CENTRAL DENSE OVERCAST (CDO) FEATURE
OBSCURING THE LOW-LEVEL CIRCULATION CENTER (LLCC). EIR SHOWS
INTENSE CONVECTIVE BURSTS (VORTICAL HOT TOWERS) WITH CLOUD TOP
TEMPERATURES AS COLD AS -85C (APPROXIMATELY 55,000 FEET). A 240108Z
MHS 89GHZ IMAGE REVEALS AN 80NM DIAMETER CONVECTIVE CORE WITH THE
LLCC POSITIONED UNDER THE NORTHEAST EDGE OF THE CORE. BASED ON THIS
IMAGE, THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE. THE
INITIAL INTENSITY IS ASSESSED AT 50 KNOTS BASED ON AN AVERAGE OF
THE DVORAK INTENSITY ESTIMATES. ENVIRONMENTAL CONDITIONS ARE VERY
FAVORABLE WITH MODERATE RADIAL OUTFLOW, ENHANCED BY AN UPPER-LOW
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: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   CIMSS ADT: 41 KTS AT 232340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   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 FORECAST TO TRACK WEST-SOUTHWESTWARD
ALONG THE SOUTHWEST PERIPHERY OF THE STR THROUGH TAU 12 THEN TURN
MORE WESTWARD AS IT APPROACHES LUZON WITH LANDFALL NEAR TAU 30. DUE
TO THE FAVORABLE CONDITIONS AND IMPROVED RADIAL OUTFLOW, TS 18W IS
EXPECTED TO INTENSIFY QUICKLY PRIOR TO LANDFALL TO AN INTENSITY OF
75 KNOTS. AFTER TRANSITING ACROSS LUZON, TS 18W WILL RE-EMERGE OVER
THE SOUTH CHINA SEA AND WILL COMMENCE A RE-INTENSIFICATION PHASE AS 
IT TRACKS WESTWARD TOWARD AND OVER VIETNAM AND SOUTHEAST ASIA. PEAK 
INTENSITY IS EXPECTED BETWEEN TAU 60 AND TAU 84, WHEN LANDFALL 
OCCURS. RAPID WEAKENING WILL OCCUR AS THE SYSTEM TRACKS INLAND.     

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
THROUGH THE FORECAST PERIOD WITH A 60NM TO 80NM SPREAD IN SOLUTIONS
FROM TAU 48 TO TAU 96 LENDING HIGH CONFIDENCE TO THE JTWC FORECAST
TRACK. RAPID INTENSIFICATION IS POSSIBLE PRIOR TO LANDFALL WITH THE
TRIGGERING OF RAPID INTENSIFICATION (RI) GUIDANCE AND UP TO 70
PERCENT PROBABILITY OF RI INDICATED IN THE 231800Z COAMPS-TC
ENSEMBLE GUIDANCE. COAMPS-TC ALSO SHOWS A 20 TO 30 PERCENT
PROBABILITY OF RI IN THE SOUTH CHINA SEA, WHICH IS LIKELY DURING
THE 261200Z TO 270600Z PERIOD. HWRF INDICATES A PEAK OF 100 KNOTS
AT TAU 84 (271200Z) AS WELL.  

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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