WDPN31 PGTW 300300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 27W (TWENTYSEVEN) 
WARNING 
NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.8N 139.1E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 323 NM WEST OF NAVSTA GUAM
   MOVEMENT PAST 6 HOURS: WESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) AND HIGH RESOLUTION
VISIBLE IMAGERY VERIFY THAT ORGANIZATION IS TIGHTENING AROUND THE
LOW LEVEL CIRCULATION CENTER (LLCC) AND CONVECTION IS DEEPENING IN
ALL QUADRANTS. THE INTENSITY ASSESSMENT IS BASED ON DVORAK
ESITMATES OF T2.5 FROM BOTH KNES AND JTWC. ADT CONTINUES TO RUN
AHEAD OF OTHER ESTIMATES AND IS NOW ESTIMATING 45KTS, BUT THE
SCATTEROMETRY AND A 292106Z PARTIAL SMAP PASS DO NOT SUPPORT SUCH
HIGH ESTIMATES. IT IS CLEAR, HOWEVER, THAT THE SYSTEM IS BEGINNING
TO RAMP UP. PEAK INTENSITY ESTIMATES HAVE BEEN REVISED UPWARD DUE
TO THE PRONOUNCED DEVELOPMENT AND IMPROVING OUTFLOW OBSERVED OVER
THE PAST SIX HOURS. ANIMATED WATER VAPOR IMAGERY ALREADY REVEALED
AMPLE RADIAL OUTFLOW, BUT RECENTLY NOTICABLE IMPROVEMENT IN BOTH
POLEWARD AND EQUATORWARD OUTFLOW HAS OCCURRED. TROPICAL STORM 27W
IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL
RIDGE THROUGH AN AREA OF LOW VERTICAL WINDSHEAR (VWS) AND HIGH
OCEAN HEAT CONTENT.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: THE DEEP LAYERED SUBTROPICAL RIDGE TO
THE NORTHWEST.


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T2.5 - 35 KTS
   CIMSS ADT: 43 KTS AT 292340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM 27W WILL SUSTAIN A
WEST-NORTHWESTERLY BEARING AT A STEADY SPEED OF ADVANCE OVER THE
NEXT 24 HOURS, THEN BEND MORE POLEWARD IN RESPONSE TO AN EXTREMELY
DEEP MID-LATITUDE TROUGH THAT IS APPROACHING FROM THE WEST. AS IT
ROUNDS THE RIDGE, A JOLT OF POLEWARD OUTFLOW WILL ENABLE A SHARP
INCREASE IN INTENSITY, WITH THE STEAM REACHING ITS PEAK NEAR THE
19TH LATITUDE NEAR TAU 72. FOLLOWING THAT, AN INFLUX COOLER AND 
DRIER AIR ASSOCIATED WITH THE WPAC COLD SURGE WILL COMBINE WITH THE 
STRETCHING AND INCREASING VWS ASSOSCIATED WITH THE MID-LATITDUE 
TROUGH TO INITIATE THE DECOUPLING PROCESS. THE DEEP TROUGH IS 
EXPECTED TO REMAIN PROGRESSIVE AND NOT QUITE PICK UP THE LLCC, AND 
NEAR TAU 120, THE LLCC WILL BECOME COMPLETELY SEPARATED AND BE 
DRIVEN WESTWARD INTO THE PHILIPPINE SEA. 



MODEL DISCUSSION: ALTHOUGH TRACK GUIDANCE REMAINS BIFURCATED
BETWEEN CARRYING THE SYSTEM INTO THE MID-LATITUDES IN A
STEREOTYPICAL RECRUVATURE SCENARIO AND A SOLUTION WHERE THE UPPER
LEVEL ENERGY SHOOTS INTO THE TROUGH BUT THE LOW LEVEL DECOUPLES AND
LOOPS BACK INTO A WESTERLY TRACK, ENSEMBLE GUIDANCE IS WEIGHTING
MORE AND MORE HEAVILY TOWARDS THE LATTER SCENARIO. ECMWF REMAINS
THE FIRMEST IN DEPICTING A RECURVATURE SCENARIO, BUT THE ECMWF
ENSEMBLE DOES NOT. BOTH THE GFS DETERMINISTIC AND ENSEMBLE OPT FOR
THE DECOUPLEING SCENARIO. IN SPITE OF THE WEIGHT OF EVIDENCE,
CONFIDENCE IN THE OUT HOURS REMAINS LOW, AND A GREAT DEAL OF
UNCERTAINTY WILL REMAIN UNTIL THE APPROACHING TROUGH TRACKS INTO THE
EAST CHINA SEA AND THE STORM ROUNDS THE AXIS OF THE SUBTROPICAL
RIDGE. 

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