WDPN32 PGTW 241500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 08W (HIGOS) WARNING 
NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.3N 139.7E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 903 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
DEPRESSION 08W (HIGOS) WITH DISORGANIZED FLARING CONVECTION
OBSCURING A COMPACT LOW-LEVEL CIRCULATION CENTER (LLCC). THE
INITIAL POSITION IS PLACED WITH LOW CONFIDENCE DUE TO THE LACK OF
RECENT OCEAN SURFACE VECTOR WIND DATA AND THE OBSCURED NATURE OF
THE LLCC. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE AGENCY DVORAK ESTIMATES OF T2.0-T2.5. THE
CIMSS ADT AND AIDT ARE ANALYZED TO BE CURRENTLY OVERESTIMATING THE
INTENSITY OF THE SYSTEM. ENVIRONMENTAL ANALYSIS INDICATES THAT 08W
IS IN A MARGINAL ENVIRONMENT CHARACTERIZED BY WEAK OUTFLOW ALOFT,
DRY AIR OVER THE WESTERN PERIPHERY, LOW (10-15 KTS) SOUTHEASTERLY
VERTICAL WIND SHEAR, AND WARM (29-30 C) SEA SURFACE TEMPERATURES.

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

CURRENT STEERING MECHANISM: THE SOUTHWESTERN PERIPHERY OF A
SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 45 KTS AT 241200Z
   CIMSS AIDT: 40 KTS AT 241200Z
   CIMSS D-MINT: 26 KTS AT 240808Z
   CIMSS D-PRINT: 32 KTS AT 241200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT FROM THE WEST

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   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: TD 08W IS FORECAST TO TRACK NORTHWESTWARD,
ALONG THE SOUTHWESTERN PERIPHERY OF THE STR THROUGH TAU 24. NEAR
TAU 24, THE SYSTEM WILL TURN NORTHWARD AS IT BEGINS TO ROUND THE
WESTERN EXTENT OF THE STR. 08W WILL THEN BEGIN TO INTERACT WITH THE
WIND FIELD OF THE MUCH LARGER TY 07W (MEKKHALA) AROUND TAU 36. AS
08W CONTINUES ON A POLEWARD TRACK, THE TWO SYSTEMS WILL CLOSE IN ON
EACH OTHER. IT IS NOT CLEAR WHETHER THE BINARY INTERACTION WILL
RESULT IN A MERGE, OR SIMPLY A DISSIPATION OF 08W WITHIN THE OUTER
EDGE OF THE WIND FIELD OF 07W. THE DISTANCE OF THE TWO VORTICIES
WILL LIKELY BE THE PRIMARY FACTOR IN DETERMINING THE FATE OF 08W.
IF THE DISTANCE IS CLOSER, A COMPLETE MERGE IS MORE LIKELY. EVEN IF
A MERGE DOES NOT OCCUR, 08W IS EXPECTED TO OPEN UP INTO A WAVE AND
BECOME UNTRACKABLE. THE TIMING OF THE INTERACTION AND POTENTIAL
MERGE REMAINS UNCERTAIN DUE TO THE RELIANCE ON THE TRANSLATION
SPEED OF BOTH 08W AND 07W. AS IT STANDS, THE DISSIPATION OF 08W IS
FORECAST TO OCCUR NEAR TAU 60, SOUTH OF HONSHU. THERE STILL REMAINS
A POSSIBILITY THAT 08W OUTRUNS 07W AND RECURVES BEFORE ENOUGH
INTERACTION WITH 07W OCCURS, BUT THAT SCENARIO IS NOW ANALYZED TO
BE LESS LIKELY. IN TERMS OF INTENSITY, 08W IS FORECAST TO MAINTAIN
A STEADY INTENSITY OR MARGINALLY INTENSIFY OVER THE NEXT 48 HOURS
AS THE VORTEX ATTEMPTS TO AXISYMMETRIZE. THE INTERACTION WITH 07W
WILL ALSO INHIBIT ANY SIGNIFICANT DEVELOPMENT.  

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN MODERATE
AGREEMENT THROUGH TAU 36 WITH MODELS GENERALLY AGREEING ON A
NORTHWESTWARD TRACK FOLLOWED BY A NORTHWARD TURN. HOWEVER, AFTER
TAU 36, THERE IS SIGNIFICANT VARIATION BETWEEN MODELS. SOME MODELS
LOSE THE VORTEX AT TAU 48 FURTHER TO THE WEST, NEAR MINAMI DAITO
JIMA, WHILE OTHERS ATTEMPT TO TURN THE SYSTEM NORTHEASTWARD. THE JTWC 
TRACK FORECAST IS PLACED NEAR THE CONSENSUS THROUGH TAU 36, THEN 
CLOSER TO THE GFS THROUGH TU 60 WITH LOW CONFIDENCE. INTENSITY 
GUIDANCE IS POOR AGREEMENT WITH HWRF AND COAMPS-TC BEING THE TWO 
AGGRESSIVE OUTLIERS, SUGGESTING A PEAK OF AROUND 55 KTS. ON THE OTHER 
HAND, THE HAFS-A AND GFS BOTH SHOW BORDERLINE TROPICAL STORM STRENGTH 
THROUGH TAU 60. THE JTWC INTENSITY FORECAST IS PLACED CLOSER TO THE 
LATTER GROUPING WITH LOW CONFIDENCE DUE TO THE INHERENT UNCERTAINTY 
REVOLVING AROUND THE MERGE WITH 07W.

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