WDPS33 PGTW 100300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 12P (TWELVE)     
WARNING NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.1S 168.4E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 36 NM NORTH OF PORT VILA, VANUATU
   MOVEMENT PAST 6 HOURS: EASTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
AS INDICATED IN ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI),
TROPICAL CYCLONE (TC) 12P CONTINUES TO STRUGGLE TO CONSOLIDATE, WITH 
FLARING DEEP CONVECTION OVER AN EXPOSED LOW-LEVEL CIRCULATION (LLC). 
ADDITIONALLY, MSI REVEALS FAIRLY SLOPPY LOW-LEVEL CLOUD BANDS WRAPPING 
AROUND THE BROAD LLC WITH A WEAK CENTER EXPOSED TO THE NORTH. THE 
INITIAL POSITION IS BASED ON A 092222Z ASCAT-C PARTIAL IMAGE, WHICH 
PLACES THE CENTER NEAR THE ISLAND OF EPI, JUST NORTH OF THE ISLAND OF 
EFATE. SURFACE OBSERVATIONS FROM PORT VILA ON EFATE ISLAND ARE 
CURRENTLY SOUTHEASTERLY AT 08 KNOTS WITH A SLP VALUE OF 999 MB. 
MAXIMUM WINDS OBSERVED IN THIS ASCAT IMAGE WERE 35 KNOTS, WHICH 
SUPPORTS THE INITIAL INTENSITY WITH HIGH CONFIDENCE. SUBJECTIVE DVORAK 
INTENSITY ESTIMATES RANGE FROM 30 TO 45 KNOTS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: LOW- TO MID-LEVEL NEAR-EQUATORIAL RIDGE
(NER) ENTRENCHED TO THE NORTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T2.0 - 30 KTS
   NFFN: T2.5 - 35 KTS
   CIMSS AIDT: 34 KTS AT 092330Z
   CIMSS DPRINT: 36 KTS AT 100100Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD
   OTHER FACTORS: FRICTIONAL IMPACTS INFLUENCED BY VANUATU AND WEAK
                  UPPER-LEVEL DRY-AIR ENTRAINMENT.

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 12P IS FORECASTED TO CONTINUE TRACKING
EAST-SOUTHEASTWARD ALONG THE SOUTHERN PERIPHERY OF THE NER THROUGH TAU 
48. AS A WEAK STEERING RIDGE BEGINS TO BUILD TO THE EAST NEAR
TAU 48, THE GENERAL EASTWARD PROGRESSION IS EXPECTED TO STEADILY SLOW 
DOWN AND POSSIBLY BECOME QUASI-STATIONARY. AFTER TC 12P TRACKS EAST OF 
THE VANUATU ARCHIPELAGO, A SLIGHT INCREASE TO A PEAK INTENSITY OF 40 
KNOTS IS ANTICIPATED BY TAU 12. SIGNIFICANT INTENSIFICATION IS NOT 
EXPECTED THROUGH THE REMAINDER OF THE FORECAST PERIOD AS THE SYSTEM 
WILL CONTINUE TO INTERACT WITH MODERATE TO HIGH NORTH-NORTHWESTERLY 
VWS AT 20-25 KNOTS AND INCREASING DRY-AIR ENTRAINMENT. THE SYSTEM IS 
EXPECTED TO DISSIPATE BY TAU 48.

MODEL DISCUSSION: WITH THE EXCEPTION OF NAVGEM, WHICH TRACKS THE 
SYSTEM DIRECTLY INTO THE AFOREMENTIONED BUILDING RIDGE, THE NUMERICAL 
MODEL GUIDANCE IS IN GOOD AGREEMENT WITH A CROSS-TRACK SPREAD OF 45 NM 
AT TAU 48. AFTER THE FORECAST PERIOD, NUMERICAL GUIDANCE DIVERGES WITH 
INCREASING UNCERTAINTY DUE TO THE EVOLVING STEERING RIDGE EXPECTED TO 
BUILD TO THE EAST. INTENSITY GUIDANCE REMAINS IN FAIR AGREEMENT WITH 
THE MESOSCALE MODELS (HAFS-A AND COAMPS-TC (GFS)) SUPPORTING THE JTWC 
INTENSITY FORECAST.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM//
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