WDPN32 PGTW 240900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 08W (HIGOS) WARNING 
NR 008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.7N 140.8E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 266 NM WEST-NORTHWEST OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
DEPRESSION 08W (HIGOS) WITH A SMALL, WEAKLY-DEFINED LOW-LEVEL
CIRCULATION CENTER (LLCC) THAT HAS RECENTLY TUCKED BACK UNDER THE
FLARING CONVECTION. THERE CONTINUES TO BE A NORTHWARD TILT IN THE
VORTEX WITH HEIGHT AND THE ASSOCIATED CONVECTION REMAINS CONFINED
TO THE NORTHERN SEMICIRCLE OF THE SYSTEM. A 240356Z AMSR2 89 GHZ
MICROWAVE IMAGE REVEALED RAGGED LOW-LEVEL CLOUD LINES WRAPPING INTO
THE COMPACT CENTER. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON TRACKING THE EXPOSED LLCC BEFORE THE
OBSCURATION OF THE CENTER. THE INITIAL INTENSITY OF 30 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES
AND CIMSS OBJECTIVE INTENSITY ESTIMATES LISTED BELOW. ENVIRONMENTAL
ANALYSIS INDICATES THAT 08W IS IN A MARGINAL ENVIRONMENT
CHARACTERIZED BY WEAK OUTFLOW ALOFT, 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: 41 KTS AT 240610Z
   CIMSS AIDT: 38 KTS AT 240610Z
   CIMSS D-MINT: 29 KTS AT 240439Z
   CIMSS D-PRINT: 25 KTS AT 240610Z

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: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: TRUNCATED THE FORECAST TO 60 HOURS,
NOW SHOWING DISSIPATION DUE TO INTERACTION WITH 07W

FORECAST DISCUSSION: 08W IS FORECAST TO CONTINUE ROUNDING THE
WESTERN EXTENT OF THE SUBTROPICAL RIDGE THROUGH TAU 48. AFTER TAU
48, THE FORECAST PHILOSOPHY FOR THE SYSTEM HAS CHANGED
SIGNIFICANTLY. THE SYSTEM IS NOW FORECAST TO BECOME ABSORBED AND
MERGE WITH THE WIND FIELD OF TY 07W (MEKKHALA). THE TIMING OF THE
MERGE IS UNCERTAIN DUE TO THE RELIANCE ON THE FORWARD TRACK SPEED
OF BOTH 08W AND 07W. AS IT STANDS, A MERGE IS FORECAST TO OCCUR
NEAR TAU 60, SOUTH OF HONSHU. REGARDING INTENSITY, 08W IS NOW
FORECAST TO ONLY MAINTAIN ITS CURRENT INTENSITY THROUGH THE TIMING
OF THE INTERACTION WITH 07W RATHER THAN HAVING A PERIOD OF
INTENSIFICATION. THIS IS MOSTLY ATTRIBUTED TO A PERSISTENT
ASYMMETRY IN THE WIND FIELD AND VORTEX TILT. ONCE THE MERGE OCCURS,
08W IS EXPECTED TO OPEN UP INTO A WAVE AND BECOME UNTRACKABLE,
HOWEVER, THERE WILL LIKELY BE AN ISOLATED AREA OF NEAR-GALE FORCE
WINDS ASSOCIATED WITH THE REMNANT VORTICITY OF THE SYSTEM AS THE
CIRCULATION UNRAVELS. 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.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN MODERATE
AGREEMENT THROUGH TAU 48 WITH A GENERAL AGREEMENT ON A
NORTHWESTWARD TRACK THROUGH TAU 24 FOLLOWED BY A NORTHWARD TURN.
HOWEVER, AFTER TAU 48, 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 CLOSE TO THE
CONSENSUS THROUGH TAU 48, THEN CLOSER TO THE GFS THROUGH TAU 60
WITH LOW CONFIDENCE. THE AVAILABLE INTENSITY GUIDANCE HAS MARKEDLY
DROPPED COMPARED TO THE PREVIOUS MODEL RUN. THE JTWC INTENSITY
FORECAST IS IN LINE WITH THE GFS AND ECMWF DEPICTION 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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