WDPN31 PGTW 162100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (TWENTYTHREE) 
WARNING NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.1N 122.2E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 114 NM NORTHEAST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) AND RADAR IMAGERY FROM THE 
PHILIPPINES SHOWS CLASSIC SIGNATURES OF A RAPIDLY ORGANIZING AND 
INTENSIFYING STORM. THE CENTRAL DENSE OVERCAST HAS BECOME COLDER AND 
MORE SYMMETRIC OVER THE LLCC IN EIR IMAGERY, WITH COILING
STRUCTURES OBSERVED WITHIN THE UPDRAFT TOPS. RADAR IMAGERY REVEALS
TIGHTLY WRAPPED CONVECTIVE BANDS FORMING A COMPACT INNER CONVECTIVE
CORE AND A FORMATIVE EYEWALL. GIVEN THE RAPID STORM EVOLUTION,
SATELLITE-BASED INTENSITY ESTIMATES ARE LAGGING IN THE 25 TO 35 KT
RANGE, WHICH IS ALMOST CERTAINTLY TOO LOW. BASED ON THE OBSERVED
STORM STRUCTURE AND A 7 MB PRESSURE FALL IN THE PAST 4 HOURS AT
CASIGURAN, LUZON JUST NORTHWEST OF THE LLCC, THE INITIAL INTENSITY
IS RAISED TO 45 KT, ALBEIT WITH LOW CONFIDENCE DUE TO THE LACK OF
HARD WIND DATA.

INITIAL WIND RADII BASIS: INITIAL ESTIMATE BASED ON SIZE OF STORM
INNER CORE

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T2.0 - 30 KTS
   CIMSS SATCON: 36 KTS AT 161725Z
   CIMSS ADT: 33 KTS AT 161730Z
   CIMSS AIDT: 33 KTS AT 161730Z
   CIMSS D-MINT: 31 KTS AT 161725Z
   CIMSS D-PRINT: 31 KTS AT 161830Z

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

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM 23W IS MAKING LANDFALL IN THE
VICINITY OF CASIGURAN, LUZON AS IT RESUMES A GENERALLY
NORTHWESTWARD MOTION TOWARD THE AXIS OF THE SUBTROPICAL RIDGE
CURRENTLY DRAPED ACROSS EASTERN CHINA AND THE EAST CHINA SEA. A
TRACK ACROSS LUZON WITH REEMERGENCE OVER THE LUZON STRAIT OR SOUTH
CHINA SEA BETWEEN 12 AND 24 HOURS FROM NOW IS EXPECTED. THE HIGH
TERRAIN OF LUZON WILL ALL BUT DESTROY THE COMPACT INNER CORE OF
23W, LIKELY RESULTING IN AN ILL-DEFINED SYSTEM INITIALLY UPON
REEMERGENCE OVER WATER. THIS INTRODUCES SOME TRACK UNCERTAINTY
UNTIL IT BECOMES CLEAR IN WHICH SPOT 23W WILL RECONSTITUTE
NORTHWEST OF LUZON IN 24 TO 48 HOURS. HOWEVER, NUMERICAL AND
AI-BASED MODELS ARE IN AGREEMENT ON A GENERAL NORTHWESTWARD TRACK
TOWARDS GUANGDONG PROVINCE, CHINA AND HONG KONG, GUIDED BY THE
SUBTROPICAL RIDGE CENTERED SOUTH OF SHANGHAI. DURING THE 48 TO 72
HOUR PERIOD, THIS RIDGE IS FORECAST TO WEAKEN DUE TO A PASSING
LONGWAVE TROUGH IN NORTHEASTERN CHINA, LIKELY SLOWING 23W'S FORWARD 
MOTION AS IT APPROACHES THE GUANGDONG AND HONG KONG COASTLINE. MODELS 
EXPECT THE RIDGE TO RESTRENGTHEN DURING THE 72 TO 96 HOUR PERIOD ONCE 
THE LONGWAVE TROUGH MOVES ON, LIKELY TURNING 23W WESTWARD OR EVEN 
WEST-SOUTHWESTWARD. A MINORITY OF MODELS DEPICT THIS TURN OCCURRING 
JUST OFFSHORE, PARALLEL TO THE COASTLINE AND PREVENTING AN IMMEDIATE 
TRACK INLAND. THIS INJECTS UNCERTAINTY IN THE LONG-RANGE INTENSITY 
FORECAST, AS THIS MINORITY SOLUTION WOULD RESULT IN A STRONGER STORM 
DUE TO ADDED TIME OVER WATER. ENVIRONMENTAL CONDITIONS ARE EXPECTED 
TO BE GENERALLY FAVORABLE THROUGHOUT THE FORECAST PERIOD, WITH 
DIFFLUENT FLOW ALOFT AND LIGHT WESTERLY VERTICAL SHEAR. THE LIMITING 
FACTOR WILL BE THE TIME REQUIRED FOR THE STORM TO REORGANIZE AFTER 
CROSSING LUZON. THE JTWC FORECAST SHOWS A PEAK INTENSITY OF 50 KT AT 
72 HOURS PRIOR TO MOVING INLAND OVER CHINA, BUT THIS PEAK COULD BE 
HIGHER IF 23W EITHER RECONSTITUTES MORE QUICKLY POST-LUZON OR REMAINS 
OFFSHORE OF CHINA FOR LONGER.

MODEL DISCUSSION: THE JTWC TRACK FORECAST IS A BIT NORTHEAST OF THE
MULTI-MODEL CONSENSUS, LEANING TOWARDS A BLEND OF THE GFS, ECMWF,
HAFS-A, AIFS, AND OTHER AI-BASED GUIDANCE. MODEL INTENSITY
FORECASTS CURRENTLY HAVE A LARGE SPREAD DUE TO DIFFERING
DEPICTIONS OF INTERACTION WITH LUZON AND TIME SPENT OVER THE SOUTH
CHINA SEA. THE JTWC INTENSITY FORECAST IS CLOSE TO A BLEND OF
HAFS-A, COAMPS-TC, ECMWF, GFS, AND AI-BASED GUIDANCE. CONFIDENCE IN
THE INTENSITY FORECAST IS LOWER THAN AVERAGE AFTER 72 HOURS.

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