WDPN34 PGTW 131500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 27W (USAGI) WARNING NR 011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.2N 125.3E
   INITIAL INTENSITY: 115 KTS
   GEOGRAPHIC REFERENCE: 267 NM EAST-NORTHEAST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 45 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
WELL, THAT ESCALATED QUICKLY AS THE SAYING GOES. FROM A VERY COMPACT
CDO AND NO EYE AT 130830Z, TO A 5NM PINHOLE EYE JUST AN HOUR AND
HALF LATER. THE LATEST ANIMATED ENHANCED INFRARED (EIR) SATELLITE
IMAGERY SHOWS THE PINHOLE EYE HAS GOTTEN EVEN SMALLER IF THATS
POSSIBLE, BUT IT IS COOLING AT THE SAME TIME SUGGESTING THAT IT MAY
BE ABOUT TO CLOSE UP. REGARDLESS, TY 27W JUST PUT ON AN AMAZING
SHOW OF EXTREMELY RAPID INTENSIFICATION (ERI), INCREASING
APPROXIMATELY 40 KNOTS IS JUST SIX HOURS. THERE HAVE BEEN NO RECENT
MICROWAVE PASSES TO REVEAL WHATS GOING ON UNDER THE HOOD BUT THE
ASYMMETRIC NATURE OF THE CDO AND A 0604Z GMI 89GHZ IMAGER SUGGESTS
THAT A RAPID ONSET EYEWALL REPLACEMENT CYCLE (ERC) COULD BE IN THE
OFFING AND THAT COULD BE WHY THE EYE IS FILLING IN. THE INITIAL
POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE PINHOLE EYE
IN THE EIR. THE INITIAL INTENSITY IS A BIT MORE CHALLENGING, WITH A
WIDE RANGE IN THE AVAILABLE INTENSITY ESTIMATES. PGTW IS THE MOST
AGGRESSIVE, WITH A T6.0, WHILE THE OTHER AGENCIES RANGE BETWEEN
T5.0 TO T5.5. WITH THE PINHOLE BEING SO SMALL, THE OBJECTIVE
ESTIMATES ARE STRUGGLING TO HOLD ONTO THE EYE, THOUGH AT ONE POINT
THE RAW ADT WAS UP TO T6.3. THE INITIAL INTENSITY IS SET AT 115
KNOTS, WHICH IS LIKELY A BIT ON THE LOW SIDE BUT ON THE HIGHER END
OF THE AVAILABLE DATA. CLEARLY THE ENVIRONMENT IS HIGHLY FAVORABLE,
NEARLY IDEAL IN FACT, WITH WARM SSTS, HIGH OHC, LOW VWS AND STRONG
RADIAL OUTFLOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T5.5 - 102 KTS
   KNES: T5.5 - 102 KTS
   CIMSS ADT: 63 KTS AT 131200Z
   CIMSS AIDT: 67 KTS AT 131200Z
   CIMSS D-PRINT: 83 KTS AT 131200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 0-5 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG RADIAL

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE PEAK INTENSITY HAS BEEN INCREASED
FROM 95 KNOTS TO 130 KNOTS DUE TO THE ONSET OF ERI. 

FORECAST DISCUSSION: TYPHOON 27W (USAGI) WILL CONTINUE TO TRACK
TOWARDS THE NORTHWEST FOR THE NEXT 24 TO 36 HOURS, ALONG THE
SOUTHWESTERN SIDE OF THE STR TO THE NORTHEAST. THE CURRENT FORECAST
DOES NOT EXPLICITLY CALL FOR LANDFALL, BUT THE SYSTEM IS EXPECTED TO
BRUSH THE FAR NORTHEASTERN TIP OF LUZON, NEAR SANTA ANA AROUND TAU
18. ONCE THE SYSTEM MOVES INTO THE LUZON STRAIT, TRACK SPEEDS WILL
SLOW DOWN RAPIDLY AS THE STR MOVES QUICKLY EASTWARD AND A BREAK IN
THE RIDGE PATTERN OPENS UP OVER TAIWAN. AT THIS POINT, THE FORECAST
UNCERTAINTY INCREASES RAPIDLY AND MASSIVELY. THE GFS CONTINUES TO
SHOW THE SYSTEM TRACKING OVER NORTHERN LUZON, RESULTING IN A WEAKER
SYSTEM MOVING INTO THE LUZON STRAIT. BEING ALREADY WEAKER AND
SMALLER THAN THE ECMWF AT THIS POINT IN THE FORECAST, THE VORTEX IS
MORE SUSCEPTIBLE TO THE RAPID INCREASE IN SHEAR AND MID-LEVEL DRY
AIR WHICH IS FORECAST TO PUSH IN FROM THE WEST. THE GFS EFFECTIVELY
SHOWS A DECAPITATION EVENT, AND THEN PUSHES THE REMNANT LOW-LEVEL
VORTEX SOUTHWESTWARD AFTER TAU 60, ALONG THE LOW-LEVEL FLOW LINES.
THE ECMWF, ON THE OTHER HAND, CONTINUES TO SHOW A STRONGER SYSTEM
THROUGH THE FORECAST PERIOD, KEEPS THE CENTER OFFSHORE OF LUZON AND
ACTUALLY INDICATES SOME STRENGTHENING IN THE LUZON STRAIT. THE
ECMWF ALSO SHOWS A SHARP INCREASE IN SHEAR AROUND TAU 48, BUT WITH
A STRONGER AND LARGER VORTEX, THE SYSTEM IS MORE RESISTANT TO THE
INFLUENCE OF THE SHEAR AND DRY AIR. THE ECMWF PUSHES THE SYSTEM
NORTHWARD INTO THE BREAK IN THE RIDGE, ON A RECURVE TRACK AHEAD OF
A MID-LATITUDE TROF PUSHING ACROSS TO THE NORTH. WITH SUCH A HIGH
DEGREE OF UNCERTAINTY, THE JTWC FORECAST, WHILE GENERALLY HEDGED
TOWARDS THE RECURVE SCENARIO, SLOWS DOWN TO JUST TWO OR THREE KNOTS
WHILE WAITING TO SEE WHICH SCENARIO MAY WIN OUT. IN TERMS OF
INTENSITY, WITH THE EXCEPTION OF A POSSIBLE ERC, THE ENVIRONMENT
WILL REMAIN VERY FAVORABLE FOR THE NEXT 12 TO 24 HOURS, AND THE
SYSTEM IS EXPECTED TO CONTINUE TO INTENSIFY, UP TO A PEAK OF 130
KNOTS BY TAU 12. ONCE IN THE LUZON STRAIT THE SYSTEM WILL BEGIN TO
WEAKEN AS IT MOVES INTO AN AREA OF COOLER SSTS, DECREASED OHC,
BEGINS TO UPWELL EVEN COOLER WATERS AND IS IMPACTED BY TERRAIN
INTERACTIONS WITH TAIWAN, AND INCREASED SHEAR. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE CONTINUES TO DEPICT
AND EXTREMELY HIGH AMOUNT OF UNCERTAINTY, WITH THE DISTANCE BETWEEN
OUTLIERS ACTUALLY INCREASING SINCE THE PREVIOUS RUN. THE GFS, GEFS,
NAVGEM, ALONG WITH THE HAFS-A AND HWRF CONSTITUTE THE GROUP OF
MODELS TAKING THE SYSTEM INTO THE SOUTH CHINA SEA AFTER TAU 72. ALL
BUT THE NAVGEM ARE ACTUALLY INLAND OVER CAMBODIA BY TAU 120. THE
REMAINDER OF THE CONSENSUS MEMBERS INCLUDING ECMWF, ECENS, EGRR,
GALWEM, JGSM AND UKMET ENSEMBLE TAKE THE SYSTEM ON A RECURVE TRACK.
HOWEVER, THE GALWEM AND JGSM STALL THE SYSTEM SOUTH OF 24N WHILE
THE ECENS AND UKMET ENSEMBLE RACE THE SYSTEM ALL THE WAY TO A POINT
EAST OF TOKYO BY TAU 120. THIS GENERATES A SPREAD OF 2400NM, OR IN
OTHER WORDS, GREATER THAN THE WIDTH OF THE CONTINENTAL UNITED
STATES. THE SUPER ENSEMBLE CONSISTING OF THE GEFS, ECENS, CMC AND
UKMET ENSEMBLES ALSO DEPICTS A 180DEG DIFFERENCE IN SOLUTIONS,
THOUGH THE GEFS IS THE ONLY MEMBER OF THE SUPER ENSEMBLE WHICH
SHOWS A TRACK INTO THE SOUTH CHINA SEA. THE JTWC FORECAST FOLLOWS
THE MULTI-MODEL CONSENSUS MEAN IN GENERAL BUT REMAINS MUCH SLOWER
AFTER TAU 48. CONFIDENCE IS EXTREMELY LOW IN LIGHT OF THE VERY
LARGE AND INCREASING UNCERTAINTY IN THE GUIDANCE. INTENSITY
GUIDANCE IS VERY MIXED AS WELL, WITH NONE OF THE MODELS EXCEPT FOR
THE HWRF PICKING UP ON THE ERI. HWRF AND DTOPS SHOW A PEAK OF
135-150 KNOTS BY TAU 24, WHILE THE CTCX SHOWS WEAKENING FROM TAU
00. THE JTWC FORECAST IS SET CLOSE TO THE HWRF TO TAU 24, THEN
DROPS CLOSER TO THE HAFS-A THEREAFTER.

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