WDPN33 PGTW 272100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (CO-MAY)       
WARNING NR 020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.5N 128.8E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 54 NM EAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM (TS) 11W IS EMBEDDED WITHIN A VERY LARGE AREA OF LOW
PRESSURE (MONSOON DEPRESSION CHARACTERISTICS), WITH PERIPHERAL WINDS 
OF 35-40 KNOTS WITHIN THE TIGHT GRADIENT ON THE EASTERN PERIPHERY OF 
THE SYSTEM. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS 
AN ELONGATED, PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) 
WITH CONVECTIVE BANDING DISPLACED OVER THE EASTERN SEMICIRCLE. 
HOWEVER, EIR IMAGERY FROM 271800-1930Z SHOWS AN EXPOSED, DEFINED LLCC 
TRACKING TOWARD THE NORTHERN TIP OF OKINAWA. THIS UPDATED CENTER AT 
271930Z IS LOCATED ABOUT 26.81N 128.44E. THIS 271930Z POSITION IS 
SUPPORTED BY MULTIPLE SURFACE OBSERVATIONS FROM THE JMA WEBSITE, WHICH 
SHOW NORTHERLY TO NORTHWESTERLY WINDS OVER OKINAWA. MAXIMUM WINDS 
REPORTED ARE FROM BOTH OKINOERABU AND ISEN (ISLANDS NORTH-NORTHEAST OF 
OKINAWA), WITH 26-27 KNOT EASTERLY WINDS (10-MINUTE AVERAGE). SURFACE 
WINDS ACROSS OKINAWA ARE LESS THAN 20 KNOTS. AS INDICATED IN ANIMATED 
RADAR IMAGERY, TS 11W HAS BECOME BETTER ORGANIZED, WITH CONVECTIVE
BANDING OVER THE SOUTHERN AND EASTERN QUADRANTS AND AN ILL-DEFINED
LLCC AT 271800Z. ANIMATED WATER VAPOR IMAGERY REVEALS AN UPPER LOW
POSITIONED TO THE WEST, WHICH IS HINDERING CONVECTIVE DEVELOPMENT
OVER THE WESTERN SEMICIRCLE, WITH ROBUST EASTWARD AND EQUATORWARD
OUTFLOW FUELING THE PERSISTENT DEEP CONVECTION OVER THE EASTERN
SEMICIRCLE. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE
BASED ON THE ANIMATED EIR IMAGERY, SURFACE OBSERVATIONS AND RADAR
IMAGERY. THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE AGENCY DVORAK ESTIMATES AS WELL AS THE
CIMSS ADT AND AIDT OBJECTIVE ESTIMATES. AS MENTIONED EARLIER, THERE
ARE STRONG GALE FORCE WINDS DISPLACED ABOUT 100 NM EAST OF THE
CENTER. THESE PERIPHERAL WINDS WERE REFLECTED IN THE MINAMIDAITO-JIMA 
OBSERVATIONS BUT HAVE SINCE DECREASED TO ABOUT 20 KNOTS.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: COMPETING STEERING ENVIRONMENT, WITH A 
LOW- TO MID-LEVEL SUBTROPICAL RIDGE POSITIONED TO THE NORTH AND
NEAR-EQUATORIAL RIDGE TO THE SOUTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS SATCON: 42 KTS AT 271639Z
   CIMSS ADT: 35 KTS AT 271800Z
   CIMSS AIDT: 37 KTS AT 271800Z
   CIMSS D-PRINT: 33 KTS AT 271800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG EASTWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: TS 11W APPEARS TO BE TRACKING WESTWARD AS OF
271930Z AS ANTICIPATED AND IS FORECAST TO CONTINUE TRACKING WESTWARD 
TO WEST-NORTHWESTWARD THROUGH TAU 48 ALONG THE SOUTHERN PERIPHERY OF 
THE DOMINANT STEERING INFLUENCE TO THE NORTH. GRADUAL INTENSIFICATION 
IS EXPECTED AS THE SYSTEM MOISTENS AND DRY AIR ENTRAINMENT DECREASES. 
ADDITIONALLY, THE UPPER LOW TO THE WEST IS EXPECTED TO WEAKEN AND 
SHIFT SOUTHWESTWARD OVER TAIWAN, WHICH WILL ENHANCE POLEWARD OUTFLOW. 
AS THE SYSTEM TRACKS WESTWARD OVER THE NEXT 12 TO 24 HOURS, THE GALE 
FORCE WINDS ALONG THE EASTERN FLANK MAY SHIFT WESTWARD AND IMPACT 
OKINAWA. AFTER TAU 48, THE SYSTEM WILL RECURVE POLEWARD OVERLAND, WITH 
STEADY WEAKENING AND DISSIPATION BY TAU 120.   

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT
THROUGH TAU 24, WITH A 30-40 NM CROSS-TRACK SPREAD IN THE GUIDANCE
FROM TAU 12 TO TAU 24. THE 270600Z GEFS AND ECENS RUNS INDICATE
CONSIDERABLE UNCERTAINTY IN THE POSITIONING AND TRACK OVER THE NEXT
48 HOURS, WITH MEDIUM OVERALL CONFIDENCE IN THE JTWC FORECAST
TRACK. DUE TO THE BROAD NATURE OF THE CENTER AND POSITIONAL
UNCERTAINTY, THERE MAY BE SHIFTS IN THE FORECAST TRACK AND INITIAL
POSITIONING UNTIL THE SYSTEM CONSOLIDATES. THERE IS MEDIUM
CONFIDENCE IN THE JTWC INTENSITY FORECAST, WITH RELIABLE INTENSITY
GUIDANCE SHOWING A LARGE SPREAD, RANGING FROM 28 TO 45 KNOTS
THROUGH TAU 24. AFTER THE FORECAST PERIOD, THERE IS LOW PROBABILITY
THAT THE REMNANTS MAY TRACK BACK OVER THE WEST SEA. HOWEVER,
UPPER-LEVEL WESTERLIES OVER THE WEST SEA AND THE KOREAN PENINSULA
WILL LIMIT RE-DEVELOPMENT.       

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