WDPS31 PGTW 142100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 08P (EIGHT) WARNING NR 
002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.4S 169.4E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 266 NM NORTH-NORTHEAST OF PORT VILA,
VANUATU
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE 08P WITH VIGOROUS BURSTS OF DEEP CONVECTION OFFSET SLIGHTLY
TO THE EAST OF THE LOW-LEVEL CIRCULATION CENTER (LLCC). ANIMATED
WATER VAPOR IMAGERY SHOWS DEFINED CIRRUS FILAMENTS EXPANDING
OUTWARD IN THE POLEWARD DIRECTION, INDICATIVE OF A STRONG OUTFLOW
CHANNEL. FURTHER ENVIRONMENTAL ANALYSIS INDICATES THAT 08P IS IN A
FAVORABLE ENVIRONMENT DUE TO LOW (10-15 KTS) WESTERLY VERTICAL WIND
SHEAR AND WARM (28-29 C) SEA SURFACE TEMPERATURES. THE INITIAL
POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE ANIMATED
MSI. THE INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE AGENCY DVORAK FIXES AND CIMSS OBJECTIVE
INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER
NEAR EQUATORIAL RIDGE (NER) CENTERED NEAR SAMOA

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 43 KTS AT 141500Z
   CIMSS ADT: 41 KTS AT 141800Z
   CIMSS AIDT: 34 KTS AT 141800Z
   CIMSS D-MINT: 35 KTS AT 141352Z
   CIMSS D-PRINT: 37 KTS AT 141800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: SLIGHT DRY AIR ENTRAINMENT FROM THE WEST

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: 08P IS FORECAST TO TRACK SOUTHEASTWARD OVER
THE NEXT 12 HOURS AS IT CONTINUES TO ROUND THE NER TO THE EAST.
AFTER TAU 12, THE RIDGE IS EXPECTED TO DRIFT NORTHWARD, CAUSING THE
TRAJECTORY TO BE MORE EASTWARD. 08P WILL THEN TRACK ALONG THE
SOUTHERN EXTENT OF THE NER THROUGH TAU 72, WITH A TRACK NORTH OF
FIJI. AROUND TAU 72, A SECOND NER IS EXPECTED TO BUILD IN NEAR 10S
170W WITH A MORE NORTHWEST-SOUTHEAST ORIENTATION. INTERACTION WITH
THIS SECOND NER IS FORECAST TO CAUSE 08P TO TRACK MORE
SOUTHEASTWARD THROUGH TAU 96. REGARDING INTENSITY, 08P IS FORECAST
TO INTENSIFY THROUGH TAU 24 AS SHEAR REMAINS LOW. AFTER TAU 24,
WESTERLY SHEAR IS EXPECTED TO INCREASE TO AROUND 20 KTS, CAUSING
THE SYSTEM TO BEGIN GRADUALLY WEAKENING. NEAR TAU 84, SHEAR WILL
INCREASE FURTHER, TO AROUND 30 KTS. AS A RESULT, 08P IS FORECAST TO
DISSIPATE NEAR TAU 96, EAST OF FIJI. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN MODERATE
AGREEMENT THROUGH TAU 48. CROSS-TRACK SPREAD REMAINS RELATIVELY
LOW, HOWEVER, ALONG-TRACK SPREAD IS EXTREMELY HIGH. GFS IS THE
FASTEST MODEL, ALREADY NORTH-NORTHEAST OF FIJI AT TAU 48 WHILE UKMET
IS MUCH SLOWER, BACK NEAR THE 172E LONGITUDE. THE LARGE ALONG-TRACK
SPREAD PERSISTS THROUGH THE END OF THE FORECAST PERIOD, MEASURING
AROUND 900 NM AT TAU 96. THE JTWC TRACK FORECAST IS PLACED SLIGHTLY
FASTER THAN THE MULTI-MODEL CONSENSUS THROUGH TAU 72 WITH MEDIUM
CONFIDENCE. AFTER TAU 72, THE TRACK FORECAST HEDGES CLOSER TO THE
GFS ENSEMBLE MEAN WITH LOW CONFIDENCE. INTENSITY GUIDANCE IS IN
SLIGHTLY WORSE AGREEMENT THIS RUN. A FEW RAPID INTENSIFICATION AIDS
ARE TRIGGERING, SUGGESTING AN INTENSITY OF AROUND 70 KTS AT TAU 24.
ON THE OTHER HAND, HAFS-A AND HWRF ARE CLOSER TO 45-50 KTS AT THE
SAME TIME. MODELS AGREE ON GRADUAL WEAKENING FROM TAU 36 ONWARD.
THE JTWC INTENSITY FORECAST IS PLACED SLIGHTLY LOWER THAN THE
CONSENSUS THROUGHOUT THE FORECAST PERIOD WITH OVERALL MEDIUM
CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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