WDPN33 PGTW 271500 AMD
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (CO-MAY) WARNING NR 
019A AMENDED//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.7N 127.9E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 13 NM NORTH-NORTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WESTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS
PERSISTENT DEEP CONVECTION BUILDING OVER A DISORGANIZED LOW-LEVEL
CIRCULATION CENTER (LLCC). TROPICAL STORM (TS) 11W HAS BEEN
RELOCATED BASED ON A 271221Z METOP-C IMAGE REVEALING AN ELONGATED
LLCC WITH THE CIRCULATION POSITIONED 86NM TO THE EAST OF THE
PREVIOUS POSITION. WATER VAPOR IMAGERY REVEALS EQUATORWARD OUTFLOW
AND DRY AIR APPROACHING FROM THE NORTH. AN UPPER-LEVEL CYCLONE TO
THE NORTHWEST APPLIES PRESSURE ON THE NORTHWESTERN QUADRANT OF THE
SYSTEM, SLIGHTLY SHEARING THE DEEP CONVECTION TO THE EAST.

INITIAL WIND RADII BASIS: 271221Z METOP-C SCATTEROMETRY

CURRENT STEERING MECHANISM: A WEAK AND COMPETING STEERING
ENVIRONMENT BETWEEN A SUBTROPICAL RIDGE TO THE NORTH AND A NEAR
EQUATORIAL RIDGE TO THE SOUTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RCTP: T2.0 - 30 KTS
   KNES: T1.5 - 25 KTS
   CIMSS SATCON: 44 KTS AT 271012Z
   CIMSS ADT: 35 KTS AT 271420Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: TROPICAL STORM (TS) 11W IS SHOWING
INDICATIONS OF UNDERGOING RAPID INTENSIFICATION OVER THE NEXT 24
HOURS. AS SUCH, THE FORECAST INTENSITY WILL REACH A PEAK OF 55KTS
WITHIN THE NEXT 24 HOURS.

FORECAST DISCUSSION: TS 11W WILL REMAIN IN A COMPETING AND
CONFUSED STEERING ENVIRONMENT BETWEEN TWO RIDGES TO THE NORTH AND 
SOUTH FOR THE NEXT 12 HOURS. THE TRACK WILL REMAIN WEAK AND IRREGULAR 
BEFORE THE RIDGE TO THE SOUTH WEAKENS AT TAU 24, ALLOWING THE SYSTEM 
TO ASSUME A WEST-NORTHWESTWARD TRACK. HOWEVER, SMALL DEVIATIONS IN
THE TRACK MOVEMENT MAY NOT BE CAPTURED WITHIN THE WARNING GRAPHIC. IF
THE RIDGE EXTENDS FARTHER SOUTH, TS 11W MAY TRACK CLOSER TO
OKINAWA OR SOUTH OF THE ISLAND. THE SYSTEM WILL CONTINUE TO ROUND THE
SOUTHWESTERN QUADRANT OF THE SUBTROPICAL RIDGE CURVING TO THE
NORTHWEST. LANDFALL WILL OCCUR IMMEDIATELY FOLLOWING TAU 72,
LEADING TO DISSIPATION BY TAU 120. RAPID INTENSIFICATION IS
POSSIBLE DURING THE NEXT 24 HOURS AS THE UPPER-LEVEL CYCLONE TO
THE NORTHWEST FILLS. THE UPPER-LEVEL ENVIRONMENT WILL BECOME HIGHLY
FAVORABLE WITH DUAL-CHANNEL OUTFLOW. THE VERTICAL WIND SHEAR WILL
REMAIN FAVORABLE AND SEA SURFACE TEMPERATURES WILL CONTINUE TO BE
WARM THROUGH TAU 48. AFTER TAU 48, VERTICAL WIND SHEAR WILL
INCREASE UNFAVORABLY TO 15-20 KTS, AND INITIATE A WEAKENING PHASE.
THE SYSTEM WILL WEAKEN GRADUALLY PRIOR TO LANDFALL BEFORE TAU 72.
AFTER TAU 72, TOPOGRAPHIC INTERACTION WILL WEAKEN THE SYSTEM TO
DISSIPATION BY TAU 120. 

MODEL DISCUSSION: THERE IS SIGNIFICANT UNCERTAINTY IN THE LONG
TERM TRACK GUIDANCE WITH A CROSS-TRACK SPREAD OF 320NM BY THE END OF
THE FORECAST PERIOD. THE JTWC MULTI-MODEL CONSENSUS TRACKERS
CONSISTENTLY INDICATE A TRACK NORTH OF OKINAWA, BUT BIFURCATE
AFTER TAU 72. THE WESTERNMOST MEMBERS OF THE BIFURCATION ARE ECMWF,
GALWEM, AND NAVGEM. THE EASTERNMOST, KEEPING THE SYSTEM OFFSHORE
ARE UKMET, NAVGEM, GFS, GEFS, AND ECENS. THE ENSEMBLE GUIDANCE
SOLUTIONS OF GEFS AND ECENS BOTH INDICATE A POSSIBLE TRACK
WESTWARD OVER OR SOUTH OF OKINAWA. AFTER TAU 72, THE BOTH ENSEMBLES 
ARE SPLIT WHETHER OR NOT THE SYSTEM WILL MAKE LANDFALL IN MAINLAND
CHINA. IF THE SYSTEM REMAINS OVER WATER, THERE IS AN INCREASED
LIKELIHOOD THAT TS 11W REACHES HIGHER INTENSITIES. RAPID
INTENSIFICATION AIDS WITHIN THE JTWC SHIPS GUIDANCE INDICATE A
SIGNIFICANT POSSIBILITY OF RAPID INTENSIFICATION WITHIN THE NEXT
24 HOURS.

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

4. JUSTIFICATION FOR AMENDMENT: RELOCATED POSITION APPROXIMATELY
86NM TO THE WEST BASED ON A 271221Z METOP-C IMAGE.//
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