WDPS33 PGTW 090300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 12P (TWELVE)
WARNING NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.3S 165.1E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 202 NM WEST-NORTHWEST OF PORT VILA,
VANUATU
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE (TC) 12P (TWELVE) EXHIBITING A MOSTLY EXPOSED LOW-LEVEL
CIRCULATION CENTER (LLCC) WITH PERSISTENT DEEP CONVECTION OFFSET EAST 
OF THE LLCC OVER THE PAST SIX HOURS. A 082243Z METOP-C SCATTEROMETRY
IMAGE CAPTURED A VERY ELONGATED CIRCULATION CENTER OF NORTHWEST TO
SOUTHEAST ORIENTATION WITH A SEMI-MAJOR AXIS OF APPROXIMATELY
124NM. THE HIGHEST WINDS OBSERVED (35KTS) APPEARED IN THE
SOUTHEASTERN QUADRANT UP TO 140 NM OUTWARD FROM THE LLCC. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
AFORMENTIONED SCATTEROMETRY DATA. THE INITIAL INTENSITY OF 35 KTS
IS ASSESSED WITH HIGH CONFIDENCE BASED ON SCATTEROMETRY DATA AND
THE INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: NER TO THE NORTH OF THE LLCC

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   CIMSS SATCON: 38 KTS AT 090000Z
   CIMSS ADT: 35 KTS AT 090100Z
   CIMSS AIDT: 34 KTS AT 090130Z
   CIMSS DPRINT: 36KTS AT 090200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 FORECAST TO CONTINUE TRACKING
EAST-SOUTHEASTWARD TO SOUTHEASTWARD THROUGH TAU 72 FOLLOWING THE
STEERING INFLUENCE OF THE NEAR EQUATORIAL RIDGE TO THE NORTH OF THE
LLCC. THOUGH VERTICAL WIND SHEAR (VWS) IS LOW TO MODERATE (10-15
KTS) AND SEA SURFACE TEMPERATURES (SST) REMAIN WARM (29-30C), A
VERY TILTED VORTEX (EAST-SOUTHEASTWARD WITH HEIGHT) RESTRAINS ANY
SIGNIFICANT OUTFLOW ALOFT. HOWEVER, UPPER LEVEL DIVERGENCE IS
EXPECTED TO IMPROVE THROUGH TAU 18, POTENTIALLY ALLOWING FOR A
PERIOD OF GRADUAL INTENSIFICATION TO OCCUR TO TAU 72. NEAR TAU 72,
A BUILDING STR AHEAD OF TRACK IS ANTICIPATED TO TURN THE SYSTEM
SOUTHWARD AND ONTO A NEAR RECIPROCAL HEADING (WEST-NORTHWESTWARD)
BY TAU 96. ADDITIONALLY, DRY AIR (RELATIVE HUMIDITY LESS THAN 50
PCT) IS EXPECTED TO BECOME A FACTOR NEAR TAU 72 WITH ENTRAINMENT
INTO THE SYSTEM THROUGH TAU 120; LOW MOISTURE AND POOR DIVERGENCE
ALOFT AFTER TAU 72 ARE THE PRIMARY FACTORS LEADING TO THE FORECASTED 
COMPLETE DISSIPATION PRIOR TO TAU 120.

MODEL DISCUSSION: GLOBAL NUMERICAL MODEL GUIDANCE IS IN OVERALL
GOOD AGREEMENT REGARDING THE PATTERN OF THE FORECAST TRACK AND
MODERATE AGREEMENT REGARDING TRACK SPEED AND DIRECTION. BY TAU 72, 
MODEL GUIDANCE HAS AN ALONG-TRACK SPREAD OF 350NM AND A CROSS-TRACK
SPREAD OF 151NM. BOTH SPREADS DIVERGE FURTHER BY TAU 120, LENDING LOW 
CONFIDENCE TO IN FORECAST TRACK FROM TAU 72 TO TAU 120. WITH THE 
EXCEPTION OF GFS EXHIBITING A CONTINUOUS WEAKENING TREND, INTENSITY 
GUIDANCE IS MODERATELY UNIFORM TO TAU 72 (15 KTS SPREAD), AND THEN 
DIVERGES THEREAFTER TO TAU 120 (35 KTS SPREAD).

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