WDPN34 PGTW 141500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 27W (USAGI) WARNING NR 015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.8N 121.6E
   INITIAL INTENSITY: 95 KTS
   GEOGRAPHIC REFERENCE: 254 NM NORTH OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 40 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
AFTER QUICKLY CROSSING OVER NORTHEAST LUZON, TYPHOON (TY) 27W HAS
EMERGED BACK OVER WATER JUST NORTH OF LUZON. THE SYSTEM TRACKED
JUST EAST OF APARRI (98232), WHICH REPORTED SUSTAINED SURFACE WINDS 
OF ONLY 20-25 KNOTS WITH MINIMUM SLP NEAR 993.6MB AT 140900Z. AS OF
141200Z, THE SYSTEM'S CENTER IS LOCATED ABOUT 30NM SOUTH-SOUTHEAST
OF CALAYAN (98133), WHICH IS REPORTING (STOPPED REPORTING AFTER
141000Z) EAST-SOUTHEASTERLY WINDS OF 20 KNOTS WITH SLP NEAR
1002.7MB. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY INDICATES
RAPID DETERIORATION OF CORE CONVECTION AROUND A WEAKLY DEFINED
LOW-LEVEL CIRCULATION CENTER (LLCC). A 141010Z SSMIS 91GHZ COLOR
COMPOSITE MICROWAVE IMAGE, WHICH SHOWED A PARTIALLY-EXPOSED LLCC
POSITIONED ALONG THE WESTERN EDGE OF THE CORE CONVECTION, SUPPORTS
THE INITIAL POSITION WITH MEDIUM CONFIDENCE. A RECENT ASCAT PASS
SHOWS GALE-FORCE WINDS AROUND A BROAD CIRCULATION CENTER JUST NORTH
OF LUZON. ENVIRONMENTAL CONDITIONS HAVE RAPIDLY DEGRADED PRIMARILY
DUE TO THE LAND INTERACTION AND INCREASING VERTICAL WIND SHEAR. THE
INITIAL INTENSITY OF 95 KTS IS CONSERVATIVELY ASSESSED WITH LOW 
CONFIDENCE HEDGED ABOVE THE AGENCY CURRENT INTENSITY ESTIMATES.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T5.0 - 90 KTS
   CIMSS SATCON: 80 KTS AT 141105Z
   CIMSS ADT: 69 KTS AT 141130Z
   CIMSS AIDT: 72 KTS AT 141130Z
   CIMSS D-MINT: 88 KTS AT 141012Z
   CIMSS D-PRINT: 75 KTS AT 141200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: 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 140000Z 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 OVER SOUTHERN TAIWAN 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. HOWEVER, THE 140600Z EPS (ECMWF)
ENSEMBLE HAS BACKED OFF ON THE RECURVE SCENARIO. ABOUT 80 PERCENT OF 
THE EPS SOLUTIONS NOW INDICATE EITHER DISSIPATION NEAR TAIWAN OR A 
SOUTHWESTWARD TRACK. ONLY 20 PERCENT OF THE EPS SOLUTIONS TRACK THE 
SYSTEM OVER THE OKINAWA REGION AND INTO THE STRONG VERTICAL WIND 
SHEAR AND JET STRENGTH WINDS OVER THE OKINAWA REGION. THE 140600Z 
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 NOW SHOWS ONLY ONE 
SOLUTION 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 EPS ENSEMBLE MEAN AND UKMET ENSEMBLE MEAN TRACK THE SYSTEM 
NORTHEAST OF TAIWAN. THE ECMWF TRACKER NOW RAPIDLY DISSIPATES THE 
SYSTEM OVER TAIWAN. THE JTWC TRACK AND INTENSITY FORECAST CONTINUES 
TO FAVOR THE GEFS ENSEMBLE AND BULK OF DETERMINISTIC TRACKERS FOR THE 
FOLLOWING REASONS. THE 140600Z ECMWF TRACKER NOW PRESENTS A MORE 
REASONABLE SOLUTION AND HAS TRENDED CONSISTENTLY TOWARD A RAPID 
WEAKENING FORECAST VICE AN UNREALISTIC RECURVE SCENARIO. 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 MIDLATITUDE 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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