WDPN32 PGTW 241500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (SAOLA) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.4N 124.2E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 416 NM SOUTH-SOUTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH A BULK
OF THE DEEP CONVECTION LIMITED TO THE EASTERN AND SOUTHERN QUADRANTS. 
THIS EXPOSED WESTERN QUADRANT IS DUE TO PERSISTENT NORTHERLY FLOW 
ADVECTING COOL DRY AIR INTO THE SYSTEM. A 240846Z SSMIS 91GHZ 
MICROWAVE IMAGE REVEALS A CLAW SHAPED DEEP CONVECTIVE BAND STRUGGLING 
TO WRAP THE CORE OF THE CIRCULATION. A 240921Z SOIL MOISTURE ACTIVE-
PASSIVE (SMAP) PASS SHOWS THE LEADING EDGE OF THE CIRCULATION HOLDS 
THE STRONGEST WINDS (38-43KTS WHEN CONVERTED TO 1-MIN AVG WINDS). THE 
INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON EIR AND 
SSMIS IMAGERY. THE INITIAL INTENSITY OF 45 KTS IS ASSESSED WITH HIGH 
CONFIDENCE BASED ON RECENT SMAP DATA WHICH CONFIRMS RECENT SPIKES IN 
DVORAK INTENSITY ESTIMATES, DESPITE MOST AUTOMATED ESTIMATES 
REMAINING 
SLIGHTLY LOWER AT 34-40KTS.

INITIAL WIND RADII BASIS: SMAP DATA 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T3.5 - 55 KTS
   CIMSS ADT: 34 KTS AT 241130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE EASTWARD

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 09W (SAOLA) IS FORECAST TO BEGIN A POLEWARD
COURSE CHANGE WITHIN THE COMING HOURS. AS THE STR TO THE EAST
BREAKS DOWN AND THE STR TO THE WEST BUILDS UP, THE SYSTEM WILL BE
FORCED TO ALTER COURSE. AS THIS TRANSFER HAPPENS, THE SYSTEM WILL
MAKE A SHARP EQUATORWARD TURN AND MAINTAIN THAT COURSE UNTIL
ROUGHLY TAU 72. AFTER PASSING EQUATORWARD OF 18N, A NEAR EQUATORIAL
RIDGE (NER) BUILDS DUE SOUTH OF THE SYSTEM, HALTING ALL FORWARD
PROGRESS AND SHARPLY TURNING THE SYSTEM POLEWARD. BY TAU 96 AND
THROUGH TAU 120, THIS NER FORCES 09W NORTHWARD AND EVENTUALLY
NORTH-NORTHWESTWARD TOWARDS THE LUZON STRAITS. IN TERMS OF INTENSITY, 
09W IS FORECAST TO BEGIN TO RAPID INTENSIFY (RI) WITHIN THE NEXT 12 
HOURS. NORTHERLY SHEAR IS THE PRIMARY LIMITING FACTOR, SO AS 09W 
INTENSIFIES, ITS ABILITY TO COCOON ITSELF AND GENERALLY SHIELD ITS 
CORE FROM THIS NORTHERLY PRESSURE WILL GREATLY AID THE SYSTEMS 
ABILITY TO INTENSIFY. BY TAU 24, FUELED BY SOUP-LIKE SEA SURFACE 
TEMPERATURES, HIGH OHC VALUES AND HIGHLY FAVORABLE ATMOSPHERIC 
CONDITIONS, 09W WILL QUICKLY ACHIEVE TYPHOON STRENGTH AND CONTINUE TO 
INTENSITY TO AN ESTIMATED 105KTS BY TAU 72. AS THE SYSTEM EXECUTES 
THE COMPLICATED BARREL ROLE THAT WILL TRACK IT TOWARDS THE LUZON 
STRAIGHTS, THERE IS A CHANCE FOR A DURATION OF NEAR QUASI-STATIONARY 
(QS) MOVEMENT NEAR TAU 72. A QS PERIOD MAY LIMIT FURTHER 
INTENSIFICATION DUE TO UPWELLING OF COOLER WATERS, BUT THIS EFFECT 
WOULD QUICKLY BE NEGATED ONCE POLEWARD MOTION IS ONCE AGAIN ACHIEVED. 
AS IT STANDS, JTWC IS FORECASTING A PEAK INTENSITY NEAR 120KTS BY TAU 
120.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN FAIR AGREEMENT CONSIDERING 
THE COMPLICATED NATURE OF THE STEERING PATTERN THROUGHOUT THE 
FORECAST PERIOD. WITH THE EXCEPTION OF NVGM, COAMPS-TC (NVGM VERSION) 
AND UK-MET ENSEMBLE, MEMBER GUIDANCE IS BEST THROUGH TAU 72, WITH ALL 
MEMBERS TAKING THE SAME GENERAL TRACK THAT JTWC HAS FORECAST. THE 
THREE AFOREMENTIONED MODELS, TAKE A SLOW AND DIRECT TRACK TOWARDS THE 
SOUTHERN PORTION OF THE LUZON STRAIT, WITH UK-MET ACTUALLY MAKING 
LANDFALL OVER THE NORTHERN PHILIPPINES. FOR THE BULK OF THE GUIDANCE 
THAT TRAVELS EQUATORWARD, AFTER TAU 72, MEMBER GUIDANCE QUICKLY 
DIVERGES AS MODELS EXECUTE THEIR TURNS AT DIFFERENT TIMES AND IN SOME 
CASES DIFFERENT DIRECTIONS TOWARDS THE LUZON STRAITS. FOR THESE 
REASONS THE JTWC TRACK FORECAST IS PLACED INITIALLY WITH MEDIUM 
CONFIDENCE AND WITH LOW CONFIDENCE THEREAFTER. RELIABLE MODEL 
INTENSITY GUIDANCE IS IN INITIALLY GOOD AGREEMENT WITH ALL MEMBER 
INDICATING RI THROUGH TAU 48, AFTER WHICH SEVERAL MEMBERS BRIEFLY 
WEAKEN THE SYSTEM BEFORE ONCE AGAIN INTENSIFYING THROUGH THE FORECAST 
PERIOD. THERE IS A ROUGHLY 35KT SPREAD IN THE GUIDANCE BY TAU 120. 
FOR THIS REASON THE JTWC INTENSITY FORECAST IS PLACED INITIALLY WITH 
HIGH CONFIDENCE AND WITH MEDIUM CONFIDENCE THEREAFTER.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: HIGH
   INTENSITY 72-120 HR: MEDIUM//
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