WDPN34 PGTW 140900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 27W (USAGI) WARNING NR 014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.9N 122.1E
   INITIAL INTENSITY: 115 KTS
   GEOGRAPHIC REFERENCE: 208 NM NORTH-NORTHEAST OF MANILA,
                         PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 12 KTS

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TYPHOON (TY) 27W MADE LANDFALL AT 140500Z ALONG THE NORTHEAST COAST
OF LUZON, AS INDICATED IN ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY, WITH THE EYE QUICKLY FILLING AND A MORE ASYMMETRIC CENTRAL
DENSE OVERCAST. A 140743Z SSMIS 91GHZ MICROWAVE IMAGE SHOWS A
WEAKLY DEFINED LOW-LEVEL CIRCULATION CENTER POSITIONED ALONG THE
WESTERN EDGE OF A CLUSTER OF DEEP CONVECTION, WITH BANDING
EXTENDING SOUTHWARD. ENVIRONMENTAL CONDITIONS HAVE DEGRADED DUE TO
THE LAND INTERACTION. HOWEVER, INCREASING VERTICAL WIND SHEAR IS
EVIDENT AS WELL WITH PRESSURE EVIDENT ALONG THE WESTERN PERIPHERY
OF THE SYSTEM. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON MULTISPECTRAL SATELLITE IMAGERY. RADAR IMAGERY WAS
UNAVAILABLE OVER LUZON. THE INITIAL INTENSITY OF 115 KTS IS
CONSERVATIVELY ASSESSED WITH MEDIUM CONFIDENCE HEDGED ABOVE THE
OBJECTIVE AND SUBJECTIVE INTENSITY ESTIMATES.

INITIAL WIND RADII BASIS: SAR DATA 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
POSITIONED TO THE NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   RJTD: T5.0 - 90 KTS
   CIMSS SATCON: 93 KTS AT 140241Z
   CIMSS AIDT: 98 KTS AT 140220Z
   CIMSS D-PRINT: 95 KTS AT 140630Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: OVER LAND
   OUTFLOW: MODERATE EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TYPHOON (TY) 27W IS FORECAST TO TRACK 
NORTHWESTWARD TO NORTH-NORTHWESTWARD THROUGH TAU 24 AS IT TRACKS
ALONG THE SOUTHWEST PERIPHERY OF THE STR. THE SYSTEM WILL WEAKEN
SIGNIFICANTLY DUE PRIMARILY TO INTERACTION WITH LAND. AFTER TAU 24,
THE SYSTEM WILL ENCOUNTER INCREASING VERTICAL WIND SHEAR ASSOCIATED
WITH SUBTROPICAL WESTERLIES EXPECTED TO SHIFT OVER SOUTHEAST CHINA.
IMPORTANTLY, THE ECMWF 131800Z RUN INDICATES A SIMILAR SCENARIO AS
GFS WITH STRENGTHENING UPPER-LEVEL WESTERLIES ACROSS SOUTHEAST CHINA 
AND JET STRENGTH WINDS OVER OKINAWA. AFTER TAU 24, THE SYSTEM WILL 
TRACK POLEWARD UNTIL IT WEAKENS SUFFICIENTLY THEN IT SHOULD STALL AND
EVENTUALLY TRACK EQUATORWARD WITHIN THE LOW-LEVEL STEERING FLOW.    

MODEL DISCUSSION: BOTH THE DETERMINISTIC AND PROBABILISTIC GUIDANCE
(EPS AND GEFS ENSEMBLES) CONTINUES TO INDICATE A MAJOR BIFURCATION
IN THE TRACK AND INTENSITY GUIDANCE. THE 140000Z EPS (ECMWF)
ENSEMBLE FAVORS A RECURVE SCENARIO, WITH A HIGH PROBABILITY OF THE
SYSTEM TRACKING NORTHEASTWARD TOWARD ISHIGAKI-JIMA, AND A LOW
PROBABILITY FOR A RAPIDLY WEAKENING SYSTEM TRACKING BACK TO THE
SOUTHWEST WITHIN THE LOW-LEVEL NORTHEASTERLY FLOW. IT IS IMPORTANT
TO NOTE THAT THE EPS ENSEMBLE ONLY SHOWS 20-30 PERCENT OF SOLUTIONS
SURVIVING THE STRONG VERTICAL WIND SHEAR AND JET STRENGTH WINDS
OVER THE OKINAWA REGION. THE 140000Z GEFS (GFS) ENSEMBLE FAVORS A
DISSIPATION SCENARIO, WITH THE LARGE MAJORITY OF SOLUTIONS EITHER
TRACKING THE SYSTEM SOUTHWESTWARD OR DISSIPATING THE VORTEX SOUTH
OF TAIWAN. GEFS SHOWS ONLY 5 SOLUTIONS (15 PERCENT) RECURVING THE
SYSTEM TOWARD ISHIGAKI-JIMA AND STALLING IT AS A WEAK TROPICAL
STORM OR TROPICAL DEPRESSION. DETERMINISTIC GUIDANCE ALSO REMAINS
BIFURCATED, WITH THE BULK OF THE GUIDANCE FAVORING A GEFS-TYPE
SOLUTION, WITH RAPID WEAKENING AND A SOUTHWESTWARD TRACK. ONLY THE
ECMWF, EPS ENSEMBLE MEAN AND UKMET ENSEMBLE MEAN TRACK THE SYSTEM
NORTHEAST OF TAIWAN. THE JTWC TRACK AND INTENSITY FORECAST FAVORS THE 
GEFS ENSEMBLE AND BULK OF DETERMINISTIC TRACKERS FOR THE FOLLOWING 
REASONS. THE 131800Z ECMWF TRACKER HAD INDICATED A MINIMAL TYPHOON 
TRACKING CLOSE TO OKINAWA DESPITE THE PRESENCE OF A JET OVER THE 
OKINAWA REGION. HOWEVER, THE 140000Z ECMWF TRACKER NOW SHOWS RAPID
WEAKENING SOUTH OF OKINAWA, WITH A 34 KNOT INTENSITY AT TAU 48 OVER
SOUTHERN TAIWAN. THE PRESENCE OF A LOW- TO MID-LEVEL SUBTROPICAL
RIDGE TO THE NORTH WILL BLOCK POLEWARD PROGRESSION AND THERE IS NO
SIGNIFICANT SHORTWAVE TROUGH INDICATED AT 500MB. IN FACT, THE 500MB
FLOW IS EITHER HIGH ZONAL OR ANTICYCLONIC, WHICH DOESN'T FAVOR A
RECURVE SCENARIO. THERE IS STILL A SIGNIFICANT DEGREE OF UNCERTAINTY 
IN WHERE THE SYSTEM WILL STALL, WHICH DEPENDS ON THE STRENGTH OF THE 
SYSTEM. A STRONGER SYSTEM WILL BE ABLE TO TRACK FURTHER POLEWARD 
WHILE A WEAKER SYSTEM WILL STALL QUICKER.   

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