WDPN31 PGTW 110900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W (SIX) WARNING NR 
002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 25.0N 140.0E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 72 NM WEST OF IWO TO
   MOVEMENT PAST 6 HOURS: WESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A
QUASI-STATIONARY, NEARLY FULLY EXPOSED LOW-LEVEL CIRCULATION CENTER
(LLCC) OF THE TROPICAL DEPRESSION (TD) 06W. RECENT FLARING
CONVECTION HAS BEEN IMMEDIATELY SHEARED OFF TO THE SOUTHEAST. A
110621Z F18 SSMIS MICROWAVE IMAGE SUITE REVEALS A CONSOLIDATING
STRUCTURE OF THE LOWER LEVELS, WITH ASYMMETRICAL CONVECTING BANDING
AND ASSOCIATED WIND FIELD, AS ALSO ANALYZED USING A 110332Z GCOMW1
AMSR2 WIND SPEED PRODUCT. LACK OF PERSISTENT CENTRAL CONVECTION CAN
BE ATTRIBUTED TO THE PRESENCE OF AN UPPER LEVEL TROUGH DIRECTLY
ABOVE THE SYSTEM. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON A NEARLY FULLY EXPOSED LLCC PRESENT IN THE
ANIMATED VISIBLE SATELLITE IMAGERY, WHILE THE INITIAL INTENSITY OF
30 KTS IS ALSO ASSESSED WITH HIGH CONFIDENCE BASED ON THE AGENCY
DVORAK FIXES, AUTOMATED AIDS LISTED BELOW, AS WELL AS A RECENT
SURFACE OBSERVATION FROM IWO TO REPORTING 15-20 KTS SOUTHERLY
WINDS. ADDITIONAL ENVIRONMENTAL ANALYSIS REVEALS MARGINALLY
FAVORABLE CONDITIONS WITH MODERATE TO HIGH DEEP-LAYER MOISTURE, LOW 
(10-15 KTS) VERTICAL WIND SHEAR (VWS), WARM (28-29 C) SEA SURFACE
TEMPERATURES, AND AN UPPER-LEVEL DIFFLUENCE REGION TO THE SOUTH
AMPLIFYING EQUATORWARD PORTION OF THE OUTFLOW.

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

CURRENT STEERING MECHANISM: COMPETING STEERING BETWEEN RIDGING TO
THE NORTHWEST AND A WEAK SUBTROPICAL RIDGE (STR) TO THE NORTHEAST 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T1.0 - 25 KTS
   KNES: T1.5 - 25 KTS
   CIMSS ADT: 30 KTS AT 110600Z
   CIMSS D-PRINT: 26 KTS AT 110610Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: UPPER LEVEL TROUGH LOCATED OVER THE SYSTEM

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   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: TD 06W HAS RECENTLY BECOME QUASI-STATIONARY IN
RESPONSE TO ITS LOCATION WITHIN A COL REGION, BETWEEN TWO AREAS OF
RIDGING TO THE NORTHWEST AND NORTHEAST. AS A RESULT, TRANSLATION
SPEEDS OVER THE NEXT 24-36 HOURS ARE EXPECTED TO BE LOW, WHILE THE
STEERING PATTERN DEVELOPS. WHILE THE SYSTEM IS HEADING NORTH AND
NORTHEASTWARD, AROUND TAU 36, RIDGING TO THE WEST IS EXPECTED TO
WEAKEN AND MOVE WESTWARD, WHILE THE STR EXTENSION TO THE EAST WILL
BUILD AND MOVE WESTWARD AS WELL. AS A RESULT, TD 06W IS FORECAST TO
BEGIN ACCELERATING AND TRACKING NORTHWARD AROUND TAU 36, WHILE 
SLIGHTLY INTENSIFYING, REACHING PEAK WIND SPEEDS OF AROUND 50 KTS BY 
TAU 48. AT THE SAME TIME, FURTHER DEVELOPMENT WILL BE HINDERED BY DRY 
AIR ENTRAINMENT, EXPECTED TO START SIGNIFICANTLY IMPACTING THE CORE OF 
THE VORTEX. AROUND TAU 78, TD 06W WILL BEGIN INTERACTING WITH A 
PASSING LONGWAVE TROUGH, AND EVENTUALLY BECOME EMBEDDED WITHIN THE 
ASSOCIATED BAROCLINIC FLOW. EXTRATROPICAL TRANSITION IS THEREFORE 
FORECAST TO BEGIN SHORTLY AFTER OR AROUND TAU 72 AND COMPLETE BY TAU 
96.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN FAIR
AGREEMENT OVERALL, WITH ALL CONSENSUS MEMBERS AGREEING ON SLOW
INITIAL SPEED OVER WATER AND A GENERALLY NORTHWARD TRACK, FOLLOWED
BY A NORTHEASTWARD TURN. CROSS-TRACK SPREAD AT TAU 48 IS HOWEVER
EXPANDING TO 165 NM, FROM 100 NM AT TAU 36. AFTER TAU 72, GALWEM
AND UKMET ENSEMBLE BECOME THE OUTLIERS, PREDICTING A NORTHWESTWARD
TURN, WHILE THE REMAINING MEMBERS OF THE MULTI-MODEL CONSENSUS
AGREE ON A NORTHWARD TRACK, WITH A NORTHEASTWARD TURN SHORTLY
THEREAFTER. JTWC FORECAST IS THEREFORE ASSESSED WITH MEDIUM
CONFIDENCE FOR THE SHORT TERM, FOLLOWED BY LOW CONFIDENCE TOWARDS
THE END OF THE CURRENT PERIOD, AND IS LAID SLIGHTLY ON THE WESTERN
SIDE OF THE MULTI-MODEL CONSENSUS. MEANWHILE, THE INTENSITY
GUIDANCE IS IN OVERALL FAIR AGREEMENT, WITH ALL MEMBERS PREDICTING
INITIAL GRADUAL INTENSIFICATION, FOLLOWED BY WEAKENING BEGINNING
AROUND TAU 60. PEAK INTENSITY SPREAD IS CURRENTLY AT 20 KTS, WITH
THE DETERMINISTIC GFS BEING THE LEAST AGGRESSIVE, AND HAFS
PROJECTING STRONGEST WINDS AROUND 55 KTS, NEAR TAU 60.

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