WDPN31 PGTW 240900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (NOUL) WARNING NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.8N 121.8E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 476 NM EAST-SOUTHEAST OF HONG KONG
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 18 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM (TS) 11W (NOUL) TRACKING ALONG THE NORTHERN COAST OF LUZON.
THE STORM HAS WESTWARDLY EXPANDING DEEP CONVECTION THAT HAS
DEVELOPED THE DISTINCT 'COMMA' SHAPE, WITH THE NORTHERNMOST EXTENT
OF THE CONVECTION BEGINNING TO WRAP AROUND TO THE UPSHEAR SIDE OF
THE SYSTEM. THE SURFACE OBSERVATION REPORTED BY THE STATIONS AT
APARRI, PHILIPPINES FROM 240700Z INDICATED SUSTAINED SOUTHERLY
WINDS AT 27 KTS, GUSTING TO 39 KTS. ENVIRONMENTAL ANALYSIS
INDICATES A FAVORABLE ENVIRONMENT CHARACTERIZED BY LOW (10-15 KTS)
VERTICAL WIND SHEAR (VWS), VERY WARM (30-31 C) SEA SURFACE
TERMPERATURES (SST), AND DECENT DIVERGENCE ALOFT, OFFSET BY TERRAIN
INTERACTION WITH LUZON. THE INITIAL POSITION IS PLACED WITH MEDIUM
CONFIDENCE BASED ON SURFACE OBSERVATIONS IN NORTHERN LUZON (APARRI,
CALAYAN, AND LAOAG), AGENCY POSITION FIXES, AND EXTRAPOLATION FROM
THE 240517Z NOAA ATMS MICROWAVE IMAGE AND THE EARLIER 240114Z
METOP-C MICROWAVE IMAGE. THE INITIAL INTENSITY OF 45 KTS IS
ASSESSED WITH HIGH CONFIDENCE BASED ON THE 240430Z OSCAT DATA
REVEALING 45 KTS WITHIN THE NORTHERN SEMICIRCLE, SUPPORTED BY THE
AGENCY DVORAK FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: ADJUSTED WIND RADII BASED ON THE 240430Z
OSCAT DATA

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR) CENTERED TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   CIMSS D-PRINT: 43 KTS AT 240500Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE WESTWARD
   OTHER FACTORS: LAND INTERACTION WITH NORTHERN LUZON

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: HIGH

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TS 11W WILL CONTINUE TRACKING NORHTWESTWARD
WHILE IT REMAINS STEERED BY THE SOUTHWESTERN PERIPHERY OF THE
STEERING RIDGE UNTIL ABOUT TAU 36. AROUND TAU 36, AND NEARLY
CONCURRENT WITH LANDFALL, 11W WILL ASSUME A MORE
NORTH-NORTHWESTERWARD TRACK AS IT ROUNDS THE SOUTHWESTERN PERIPHERY
OF THE RIDGE. LANDFALL IS EXPECTED JUST AFTER TAU 36, AT WHICH
POINT, STORM MOTION MAY BECOME MORE ERRATIC THAN REFLECTED IN THE
FORECAST, AS LAND INTERACTION CAN UNPREDICATABLY IMPACT TRACK SPEED
AND TRAJECTORY. REGARDING INTENSITY, NOUL IS FORECAST TO STEADILY
INTENSIFY FOR THE NEXT 12 HOURS, INHIBITED SLIGHTLY BY INTERACTION
WITH LUZON. FROM TAU 12-36, 11W IS FORECAST TO UNDERGO A PERIOD OF
RAPID INTENSIFICATION (RI) AS IT ENTERS INTO A HIGHLY FAVORABLE
ENVIRONMENT IN THE SOUTH CHINA SEA AND TRACKS AWAY FROM LUZON. NOUL
IS FORECAST TO REACH ITS PEAK INTENSITY AT TAU 36 AT 80 KTS, JUST
PRIOR TO MAKING LANDFALL TO THE NORTHEAST OF HONG KONG. 11W IS
FORECAST TO RAPIDLY WEAKEN POST-LANDFALL, WITH DISSIPATION EXPECTED
NO LATER THAN TAU 72.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE REMAINS IN
STRONG AGREEMENT THROUGH THE FORECAST PERIOD, SUPPORTING THE JTWC
FORECAST WITH HIGH CONFIDENCE. RELIABLE INTENSITY AIDS ARE IN
MODERATE AGREEMENT; THOUGH, THE INTENSITY SPREAD FOR THE PEAK
INTENSITY HAS STRUNK TO 15 KTS, WITH RELIABLE MODELS DEPICTING A
RANGE OF 65-80 KTS AT PEAK. SEVERAL RI AIDS HAVE MET CRITERIA,
SUPPORTING THE JTWC RI FORECAST. OVERALL, THE JTWC INTENSITY
FORECAST IS PLACED WITH MEDIUM CONFIDENCE, WITH UNCERTAINTY
STEMMING FROM THE MAGNITUDE OF THE FORECAST RI AND THE WEAKENING
TREND AFTER 11W MAKES LANDFALL.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: MEDIUM//
NNNN