WDPS31 PGTW 210300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 16P (SIXTEEN) WARNING 
NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.5S 159.1E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 482 NM NORTHWEST OF NOUMEA, NEW CALEDONIA
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 24 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) 16P HAS UNDERGONE RAPID CONSOLIDATION OVER THE 
COURSE OF THE LAST 12 TO 24 HOURS. ANIMATED MULTISPECTRAL SATELLITE 
IMAGERY (MSI) INDICATES THAT BY 210000Z, THE COMPACT LOW-LEVEL 
CIRCULATION CENTER (LLCC) DECOUPLED FROM UNDER A CANOPY OF DEEP 
CONVECTION. AN ACCOMPANYING 202113Z ASCAT PASS REVEALED 35-37 KNOT 
WINDS ALONG THE NORTHEASTERN FLANK OF THE LLCC, WHICH IS EMBEDDED 
WITHIN A TROUGH THAT EXTENDS SOUTHEAST TO INVEST 94P AND NORTHWEST TO 
INVEST 90P. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE 
BASED ON THE EXPOSED LLCC IN THE MSI. THE INITIAL INTENSITY IS 
ASSESSED WITH HIGH CONFIDENCE BASED ON THE ASCAT PASS NOTED ABOVE AND 
CONSISTENT WITH THE PGTW CURRENT INTENSITY ESTIMATE. ENVIRONMENTAL 
CONDITIONS ARE MARGINALLY FAVORABLE, CHARACTERIZED BY LOW 
SOUTHEASTERLY VWS, WARM SSTS AND GOOD POLEWARD OUTFLOW ALOFT.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED NEAR FIJI. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T1.0 - 25 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 16P IS FORECAST TO TRACK
SOUTHEASTWARD ALONG THE SOUTHWESTERN PERIPHERY OF THE DEEP STR OVER
THE 24 TO 36 HOURS, BEFORE STARTING A GRADUAL TURN EASTWARD AS IT
ROUNDS THE RIDGE. THE SYSTEM IS EXPECTED TO PASS IN CLOSE PROXIMITY 
TO THE WESTERN COAST OF NEW CALEDONIA. MESOSCALE VARIATIONS IN THE
FORECASTED POSITION OF THE RIDGE COULD RESULT IN A DIRECT STRIKE ON
THE NORTHWEST TIP OF THE ISLAND WITHIN THE NEXT 12 HOURS. IN TERMS
OF INTENSITY, THE SYSTEM IS EXPECTED TO ATTAIN A PEAK OF 40 KNOTS 
WITHIN THE NEXT 12 HOURS BEFORE LEVELING OFF AND THEN WEAKENING 
THROUGH THE REMAINDER OF THE FORECAST PERIOD. IF TC 16P DOES IN FACT 
MAKE LANDFALL OVER NEW CALEDONIA, THE STORM WILL WEAKEN MORE RAPIDLY 
THAN CURRENTLY FORECAST DUE TO OROGRAPHIC INTERACTION. ASSUMING A 
CLOSE APPROACH BUT NO LANDFALL, THE SYSTEM WILL STEADILY WEAKEN DUE 
TO INCREASING SHEAR AND DRY AIR ENTRAINMENT, ULTIMATELY DISSIPATING 
BY TAU 72 AS IT MOVES SOUTHWEST OF TONGA. 

MODEL DISCUSSION: DETERMINISTIC, ENSEMBLE AND ARTIFICIAL INTELLIGENCE 
(AI) GUIDANCE ARE IN TIGHT AGREEMENT ON THE TRACK FORECAST,
WITH MINIMAL CROSS-TRACK SPREAD UNTIL TAU 72, WHEN THE GUIDANCE 
DIVERGES AS THE VORTEX SHALLOWS OUT AND DISSIPATES. CONSISTENT
WITH AN ACCELERATING POLEWARD TRACK, ALONG-TRACK SPREAD INCREASES
EARLY-ON IN THE FORECAST, GROWING TO 220NM BY THE END OF THE
FORECAST, BETWEEN THE FAST GFS AND GEFS AND THE SLOWER ECMWF. THE
JTWC FORECAST IS POSITIONED CLOSE TO THE GFS-GEFS TRACKERS THROUGH
THE FORECAST PERIOD WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS IN
GOOD AGREEMENT THAT THE SYSTEM WILL INTENSIFY SLIGHTLY BEFORE
LEVELING OFF AND SLOWLY WEAKENING, WITH THE EXCEPTION OF THE SHIPS
(BOTH NAVGEM AND GFS) WHICH STEADILY INCREASE THE INTENSITY ALL THE
WAY THROUGH TAU 96. THE JTWC FORECAST IS PLACED NEAR THE HWRF AND
COAMPS-TC TRACKERS WITH HIGH CONFIDENCE. 

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: HIGH//
NNNN