WDPN32 PGTW 182100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (RAGASA) WARNING NR 
002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.2N 132.3E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 526 NM NORTHWEST OF YAP
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A BROAD
AREA OF CONVECTION POSITIONED WITHIN THE SOUTHERN SEMICIRCLE OF
CIRCULATION ASSOCIATED WITH TROPICAL STORM (TS) 24W (RAGASA). THE
LOW-LEVEL CIRCULATION CENTER (LLCC) IS PARTIALLY EXPOSED TO THE
NORTH, MAINLY DUE TO PRESENCE OF DRY AIR LIMITING CONVECTIVE
BUILDUP. THE INITIAL POSITION IS THEREFORE PLACED WITH MEDIUM
CONFIDENCE BASED ON ANIMATED SATELLITE IMAGERY, CONSISTENT WITH
AREA OF CALM WINDS PRESENT IN A 181447Z OCEANSAT-3 OSCAT PASS. THE
INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED
ON THE AFOREMENTIONED OSCAT PASS, AS WELL AS A COMBINATION OF
AGENCY DVORAK AND OBJECTIVE ESTIMATES LISTED BELOW. ENVIRONMENTAL
ANALYSIS REVEALS CONDITIONS FAVORABLE FOR DEVELOPMENT WITH WARM
(29-30 C) SEA SURFACE TEMPERATURES, LOW (10-15 KTS) VERTICAL WIND
SHEAR AND STRONG EQUATORWARD OUTFLOW ALOFT.

INITIAL WIND RADII BASIS: A 181447Z OCEANSAT-3 OSCAT PASS

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE
NORTHWEST 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS SATCON: 32 KTS AT 181648Z
   CIMSS ADT: 32 KTS AT 181730Z
   CIMSS AIDT: 31 KTS AT 181730Z
   CIMSS D-MINT: 31 KTS AT 181648Z
   CIMSS D-PRINT: 29 KTS AT 181810Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG EQUATORWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT FROM THE NORTH

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 24W IS FORECAST TO SLOWLY TRACK
WEST-NORTHWESTWARD OVER THE NEXT 24 HOURS, WHILE POSITIONED IN A
WEAK STEERING ENVIRONMENT. AROUND TAU 24, THE STR WILL BUILD TO THE
NORTHEAST OF THE SYSTEM RESULTING IN SLIGHT ACCELERATION AS WELL AS
A MORE NORTHWESTWARD TRACK FOR A PERIOD OF ANOTHER 24 HOURS.
AFTERWARDS, THE RIDGE WILL CONTINUE TO BUILD AND EXTEND EASTWARD,
RESULTING IN A RETURN TO A GENERALLY WEST-NORTHWESTWARD TRACK,
WHICH IS EXPECTED TO LAST THROUGHOUT THE CURRENT FORECAST PERIOD.
IN TERMS OF INTENSITY, TS 24W IS EXPECTED TO UTILIZE THE
OVERWHELMINGLY FAVORABLE ENVIRONMENT AND INTENSIFY CONTINUOUSLY
THROUGH AROUND TAU 96, WITH POTENTIAL PERIODS OF RAPID
INTENSIFICATION (RI). PEAK INTENSITY IS EXPECTED TO REACH 115-125
KTS BETWEEN TAUS 72 AND 96. THE ONLY HINDRANCE TO DEVELOPMENT IS
PRESENCE OF DRY AIR TO THE NORTH, BUT CURRENTLY AVAILABLE MODEL
GUIDANCE INDICATES THAT THE SYSTEM WILL BE ABLE TO OVERCOME THOSE
IMPACTS WITHIN THE NEXT 36 TO 42 HOURS. BETWEEN TAU 96 AND 120, TS
RAGASA IS FORECAST TO BEGIN WEAKENING, AS ITS WIND FIELD STARTS
INTERACTING WITH THE TERRAIN OF NORTHERN LUZON, SOUTHERN TAIWAN AND
EVENTUALLY AS THE SYSTEM APPROACHES THE SOUTHEASTERN COAST OF
CHINA. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN FAIR
AGREEMENT THROUGHOUT THE FORECAST, WITH ALL AVAILABLE GUIDANCE
PREDICTING A GENERALLY NORTHWESTWARD TRACK THROUGHOUT THE FORECAST
PERIOD. JTWC OFFICIAL TRACK IS LAID CLOSE TO THE MULTI-MODEL
CONSENSUS WITH MEDIUM CONFIDENCE, WHICH REFLECTS THE UNCERTAINTY
ASSOCIATED WITH THE INITIALLY WEAK STEERING ENVIRONMENT. THIS IS
EVIDENT THROUGH A 40 NM CROSS-TRACK SPREAD AT TAU 12, OPENING TO
140 NM BY TAU 48 AND EVENTUALLY NEARLY 300 NM AS THE SYSTEM
APPROACHES LANDFALL. ALL CURRENTLY AVAILABLE GUIDANCE HOWEVER
INDICATES TRACK WITHIN THE LUZON STRAIT, WITH MAJORITY OF THE
MODELS POINTING TOWARDS CENTERED PLACEMENT. JTWC INTENSITY FORECAST
IS ASSESSED ON THE HIGHER END OF THE MULTI-MODEL CONSENSUS WITH
MEDIUM CONFIDENCE THROUGH TAU 72. ALL MODELS SHOW GOOD AGREEMENT
WITH MULTIPLE RI AIDS TRIGGERED (RICN, RIPA, FRIA, RIDE). AFTER TAU
72 THE GUIDANCE IS MORE SPREAD, WITH MOST CONSERVATIVE
NAVGEM-DRIVEN COAMPS-TC (SHOWING PEAK OF 90-95 KTS) AND MOST
AGGRESSIVE HAFS-A (INDICATING 130-135 KTS MAXIMUM WINDS AROUND TAU
84. OVERALL INTENSITY SPREAD AT PEAK IS CURRENTLY 55 KTS,
REFLECTIVE THE LOW FORECAST CONFIDENCE BEYOND TAU 72. 

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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