WDPN31 PGTW 230900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 11W (ELEVEN) WARNING 
NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.4N 128.4E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 459 NM EAST-NORTHEAST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 19 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
DEPRESSION (TD) 11W AS A CONSOLIDATING AND PARTIALLY EXPOSED LOW
LEVEL CIRCULATION CENTER (LLCC) WITH A RECENTLY DEVELOPED PLUME OF
CENTRAL DEEP CONVECTION. ADDITIONAL BANDS OF DEEP CONVECTION
DISPLACED FAR TO THE NORTH AND SOUTH ARE BEGINNING TO WRAP AROUND
THE SYSTEM; HOWEVER, THE SYSTEM REMAINS MOSTLY DEVOID OF DEEP
CONVECTION DESPITE THE AMPLE AVAILABLE ATMOSPHERIC MOISTURE. THE
230504Z AMSR2 MICROWAVE IMAGE CONFIRMS THE LIMITED DEEP
CONVECTION AND REVEALS THE SYMMETRICAL LOWER LEVEL STRUCTURE.
ENVIRONMENTAL ANALYSIS REVEALS A FAVORABLE ENVIRONMENT
CHARACTERIZED BY LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS), GOOD
DIVERGENCE ALOFT SUPPORTING MODERATE WESTWARD OUTFLOW, AND WARM (29-30
C) SEA SURFACE TEMPERATURES (SST), OFFSET BY THE SYSTEM'S SLIGHT 
SOUTHWESTWARD VERTICAL TILT. THE INITIAL POSITION IS PLACED WITH HIGH 
CONFIDENCE BASED ON THE PARTIALLY EXPOSED LLCC AND THE 230504Z AMSR2 
MICROWAVE IMAGE. THE INITIAL INTENSITY OF 25 KTS IS ASSESSED WITH 
MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES LISTED BELOW, 
SUPPORTED BY THE 230336Z OSCAT IMAGE REVEALING 25-30 KTS IN THE 
SOUTHEASTERN SEMICIRCLE.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED TO THE
NORTH-NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T1.0 - 25 KTS
   KNES: T1.5 - 25 KTS
   CIMSS D-PRINT: 20 KTS AT 230600Z

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TD 11W WILL TRACK GENERALLY NORTHWESTWARD
THROUGH TAU 60, WHILE IT REMAINS ON THE SOUTHWESTERN PERIPHERY OF
THE STEERING RIDGE. 11W IS ANTICIPATED TO REMAIN ON A STEADY TRACK
AS IT APPROACHES LANDFALL NORTHEAST OF HONG KONG, WITH TERMINAL
LANDFALL EXPECTED JUST BEFORE TAU 60. REGARDING INTENSITY, 11W IS
EXPECTED TO STEADILY INTENSIFY UP UNTIL LANDFALL, FOLLOWED BY DRASTIC 
WEAKENING CAUSED BY TERRAIN INTERACTION. AS THE STORM TRANSITS THE 
LUZON STRAIT, THE MOUNTAINOUS TERRAIN OF LUZON MAY DISRUPT INFLOW FROM 
THE SOUTH, CONTRIBUTING TO AN ASYMMETRIC WINDFIELD WHERE THE STRONGEST 
WINDS ARE LOCATED IN THE NORTHERN SEMICIRCLE (AS DEPICTED IN BOTH GFS 
AND ECMWF DETERMINISTIC MODELS). WHEN 11W ENTERS THE SOUTH CHINA SEA 
BETWEEN TAU 24-36, IT WILL ENCOUNTER AN INCREASINGLY FAVORABLE 
ENVIRONMENT, OPENING THE POTENTIAL FOR RAPID INTENSIFICATION (RI) AND 
A PEAK GREATER THAN CURRENTLY FORECASTED. THE PEAK INTENSITY IS 
FORECAST TO OCCUR AT TAU 60 AT 75 KTS, THOUGH THE ACTUAL PEAK WILL 
LIKELY OCCUR BETWEEN TAU 48-60 BEFORE LAND INTERACTION BEGINS TO 
WEAKEN THE STORM. ULTIMATELY, LAND INTERACTION WILL COMPLETELY 
DISSIPATE 11W BY TAU 120.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN STRONG
AGREEMENT THROUGH TAU 60, SUPPORTING THE NEAR-TERM JTWC TRACK
FORECAST WITH HIGH CONFIDENCE. GUIDANCE DIVERGES THEREAFTER, AS
MODELS DISAGREE ON 11W'S TRACK WHILE OVER LAND. DUE TO THE
UNCERTAINTY IN TRACK AFTER LANDFALL, THE JTWC TRACK FORECAST IS
PLACED WITH LOW CONFIDENCE FROM TAU 72-120. RELIABLE INTENSITY AIDS
ARE IN POOR AGREEMENT IN BOTH RATE OF INTENSIFICATION AND PEAK
INTENSITY. HAFS-A AND COAMPS-TC (NAVGEM BOUNDARY CONDITIONS) SHOW
VERY GRADUAL INTENSIFICATION AND A PEAK BELOW TYPHOON STRENGTH,
WHILE COAMPS-TC (GFS BOUNDARY CONDITIONS), HWRF, AND EXPERIMENTAL
AI GOOGLE DEEPMIND DEPICT A NEAR-RI OR RI TREND WITH A PEAK
INTENSITY ABOVE 75 KTS. AS A RESULT, THE JTWC INTENSITY FORECAST IS
PLACED NEAR THE MULTI-MODEL CONSENSUS WITH MEDIUM CONFIDENCE FROM
TAU 0-72 AND LOW CONFIDENCE FROM TAU 72-120. UNCERTAINTY IN THE
LATE-TERM FORECAST STEMS FROM THE LACK OF CONFIDENCE IN WEAKENING
TREND AFTER 11W MAKES LANDFALL.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: LOW
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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