WDPN31 PGTW 011500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (JANGMI) WARNING NR 
022//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.7N 127.5E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 20 NM NORTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 32 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A BROAD,
IRREGULAR LOW LEVEL CIRCULATION (LLC), WITH A RAPIDLY DETERIORATING
CONVECTIVE STRUCTURE. THE UPPER-LEVEL ROTATION IS BEGINNING TO
DECOUPLE UNDER PRESSURE FROM INCREASING WESTERLY SHEAR (NOW
ESTIMATED AT 15 KNOTS), AND ENTRAINMENT OF DRY, SUBSIDENT AIR 
IMPINGING UPON THE SOUTHWESTERN QUADRANT OF THE LLC. ANIMATED JMA 
RADAR DATA INDICATES MINIMAL CONVECTIVE ACTIVITY ACROSS THE WESTERN
SEMICIRCLE OF THE SYSTEM, WHILE A WELL-DEFINED RAIN SHIELD AND 
EMBEDDED CONVECTION IS FOCUSED IN THE NORTHEAST AND EASTERN 
QUADRANTS. A 011227Z METOP-C ASCAT PASS DELINEATED A SYMMETRICAL EYE 
FEATURE CENTERED JUST WEST OF IEJIMA ISLAND, AND THE EASTERN EDGE OF 
THE LLCC EXTENDING OVER THE CENTRAL REGION OF OKINAWA PROPER. SURFACE
OBSERVATIONS INDICATE LIGHT AND VARIABLE WINDS AT SITES WITHIN THE
CIRCULATION CENTER (EYE), AND WINDS QUICKLY INCREASING AT NAHA AS THE 
SOUTHERN EDGE OF THE EYE MOVES NORTHWARD. SURFACE PRESSURES AT IEJIMA 
AUXILIARY LANDING FIELD REACHED A MINIMUM OF 982MB NEAR 1200Z, 
SUPPORTING THE INITIAL MSLP ASSESSMENT WITH HIGH CONFIDENCE. THE 
INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE 
AFOREMENTIONED ASCAT DATA. THE INITIAL INTENSITY IS ASSESSED WITH 
HIGH CONFIDENCE, BASED ON THE ASCAT DATA, AND THE D-PRINT AND AIDT 
ESTIMATES. ENVIRONMENTAL CONDITIONS ARE BEGINNING TO DETERIORATE, 
WITH A RECENT INCREASE IN VERTICAL WIND SHEAR (VWS) EVIDENT IN THE 
LATEST CIMSS ESTIMATES, RAPIDLY DECREASING SEA SURFACE TEMPERATURES 
(SSTS), AND DRY, SUBSIDENT AIR ENTRAINING INTO THE CORE OF THE 
SYSTEM. HOWEVER, POLEWARD OUTFLOW REMAINS ROBUST, FLOWING INTO THE 
RIGHT REAR ENTRANCE REGION OF A STRONG JET MAXIMUM OVER CENTRAL 
HONSHU. 

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) POSITIONED NEAR IWO TO. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.5 - 55 KTS
   RCTP: T3.5 - 55 KTS
   KNES: T4.0 - 65 KTS
   CIMSS AIDT: 55 KTS AT 011230Z
   CIMSS D-MINT: 60 KTS AT 010910Z
   CIMSS D-PRINT: 55 KTS AT 011230Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 15-20 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY MID-LEVEL SUBSIDENT AIR ENTRAINING INTO THE
SOUTHWESTERN FLANK OF THE CIRCULATION. 

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: OWING TO A LATE-STAGE TROCHOIDAL OSCILLATION, THE 
CENTER OF TS 06W BYPASSED A DIRECT LANDFALL ON OKINAWA; HOWEVER, DUE 
TO THE EXPANSIVE SCALE OF THE LLCC, THE MAJORITY OF OKINAWA 
EXPERIENCED CONDITIONS CONSISTENT WITH EYE PASSAGE IN THE SURFACE 
WIND FIELD. HAVING ROUNDED THE AXIS OF THE STR TO THE EAST, TROPICAL 
STORM (TS) 06W WILL NOW ACCELERATE NORTHEASTWARD ALONG THE 
NORTHWESTERN FLANK OF THE RIDGE, TRACKING WEST OF BUT PARALLEL TO THE 
NORTHERN RYUKYU ISLANDS FOR THE NEXT 12-18 HOURS, BEFORE PASSING 
ADJACENT TO THE SOUTHERN TIP OF KYUSHU. THE SYSTEM WILL TRACK IN 
CLOSE PROXIMITY TO OR POTENTIALLY MAKE A BRIEF LANDFALL ALONG THE 
SOUTHERN TIP OF HONSHU SOUTH OF KYOTO AROUND TAU 30. A LANDFALL ON 
THE SOUTHERN PORTION OF THE IZU PENINSULA IS EXPLICITLY FORECAST TO
OCCUR AROUND TAU 40, AFTER WHICH TS 06W WILL RAPIDLY TRANSIT THE 
SOUTHERN SAGAMI BAY AND THE SOUTHERN APPROACHES TO TOKYO BAY. BY TAU 
48, THE SYSTEM WILL BEGIN TO DECELERATE AS IT MOVES BACK OVER OPEN 
WATERS EAST OF CHOSI. FORWARD PROPAGATION SPEED WILL DECELERATE 
SIGNIFICANTLY BY THE END OF THE FORECAST AS THE CYCLONE VEERS 
EASTWARD IN RESPONSE TO THE STR RETREATING SOUTHWARD TO A POSITION 
NEAR GUAM. REGARDING INTENSITY, THE SYSTEM IS ALREADY EXHIBITING 
SIGNS OF SIGNIFICANT VORTEX TILT, AND THE INCREASING SHEAR AND DRY 
AIR ENTRAINMENT WILL LEAD TO A COMPLETE DECOUPLING OF THE VERTICAL 
VORTEX WITHIN THE NEXT 24 HOURS. HOWEVER, WHILE THE REMAINING VORTEX 
WILL BE SHALLOW, THE SURFACE WIND FIELD WILL REMAIN RELATIVELY 
ROBUST, AND WILL GRADUALLY DECAY DUE TO CONSERVATION OF MOMENTUM AS 
WELL AS THE INFLUENCE OF BAROCLINIC FORCING. TS 06W WILL GRADUALLY 
WEAKEN IN A STEP-WISE MANNER BUT REMAIN A STORM-FORCE SYSTEM UNTIL 
THE END OF THE FORECAST PERIOD. 

MODEL DISCUSSION: THE CONSENSUS TRACK PACKAGE IS IN EXTREMELY
STRONG AGREEMENT THROUGH THE FORECAST PERIOD. CROSS-TRACK SPREAD IS
CONSISTENTLY LESS THAN 40NM THROUGH TAU 48, AND ONLY MARGINALLY
INCREASES TO 90-100NM AT TAU 72. THE JTWC FORECAST IS POSITIONED
NEAR THE MULTI-MODEL CONSENSUS MEAN WITH HIGH CONFIDENCE. INTENSITY
GUIDANCE IS ALSO IN STRONG AGREEMENT, WITH THE EXCEPTION OF THE
SHIPS-GFS WHICH DEPICTS A RAPID DISSIPATION OF THE SYSTEM WITHIN 36
HOURS. THE JTWC FORECAST IS PLACED NEAR THE ADJUSTED CONSENSUS MEAN
WITH HIGH CONFIDENCE. 

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: HIGH//
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