WDPS32 PGTW 222100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 19P (NINETEEN) WARNING 
NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.4S 177.6W
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 401 NM WEST OF PAGO PAGO
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHEASTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A STILL
RATHER DISORGANIZED SYSTEM, WITH TWO AREAS OF DEEP CONVECTION
DISPLACED AROUND THE CENTER. THE LARGEST AREA OF CONVECTIVE
ACTIVITY IS LOCATED ABOUT 100NM WEST OF THE ASSESSED LOW LEVEL
CIRCULATION CENTER (LLCC). THE SECOND AREA OF DEEP CONVECTION, WITH
VERY COLD CLOUD TOPS EXCEEDING -90C AND FREQUENT LIGHTNING
ACTIVITY, IS LOCATED OVER OR VERY NEAR THE LLCC. A 221757Z SSMIS
91GHZ MICROWAVE IMAGE DEPICTED THE LOW-LEVEL INFLOW BANDS TO THE
SOUTH VERY WELL, ALLOWING FOR A HIGHER CONFIDENCE INITIAL POSITION.
HOWEVER, THE IMAGE ALSO DEPICTED A VERY DISORGANIZED CONVECTIVE
STRUCTURE WITH POCKETS OF DEEP CONVECTION EXTENDING IN BANDS IN A
BROAD ARC ACROSS THE NORTHERN PORTION OF THE CIRCULATION. EVEN WITH
THE MICROWAVE IMAGE, THE INITIAL POSITION IS ASSESSED WITH LOW
CONFIDENCE DUE TO THE HIGHLY DISORGANIZED STRUCTURE OF THE LLCC AT
PRESENT. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE,
AT ROUGHLY THE AVERAGE OF THE AVAILABLE SUBJECTIVE AND OBJECTIVE
INTENSITY ESTIMATES. OF NOTE IS THE FACT THAT IN THE SUBSEQUENT
HOURS, THE ADT AND RAW ADT HAVE SHOT UP TO T3.2 AND T3.8
RESPECTIVELY, INDICATIVE OF THE ONSET OF POSSIBLE RAPID
INTENSIFICATION (RI). THE ENVIRONMENT IS HIGHLY FAVORABLE FOR RI,
WITH LOW VWS, VERY WARM SSTS AND GOOD POLEWARD AND EQUATORWARD
OUTFLOW, ENHANCED BY A DEVELOPING POLEWARD OUTFLOW CHANNEL.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF AN EXTENSION OF
THE SUBTROPICAL RIDGE (STR) CENTERED FAR TO THE SOUTHEAST.
ADDITIONALLY, THERE IS A SMALL RIDGE LOCATED SOUTH OF TONGA, MOVING
QUICKLY TO THE NORTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   KNES: T1.0 - 25 KTS
   PHFO: T2.5 - 35 KTS
   CIMSS ADT: 43 KTS AT 221730Z
   CIMSS AIDT: 31 KTS AT 221730Z
   CIMSS D-MINT: 30 KTS AT 221757Z
   CIMSS D-PRINT: 34 KTS AT 221800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD
   OTHER FACTORS: ASYMMETRIC NATURE OF THE VORTEX CURRENTLY. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   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: TC 19P WILL CONTINUE TO STEADILY TURN
SOUTHWARD OVER THE NEXT 12 HOURS AS THE RIDGE TO THE EAST
STRENGTHENS AND THE RIDGE TO THE SOUTH SIMULTANEOUSLY WEAKENS AND
SHIFTS NORTHEASTWARD. WITHIN THE NEXT 24 HOURS, THE RIDGE TO THE
SOUTH WILL MERGE WITH THE BUILDING STR TO THE EAST, FORMING A NEW
STR CENTERED NEAR 20S 170W. TC 19P WILL ACCELERATE
SOUTH-SOUTHWESTWARD ALONG THE WEST SIDE OF THE STR THROUGH TAU 36,
THEN REACH THE RIDGE AXIS AROUND TAU 48. TC 19P WILL ROUND THE
RIDGE AXIS SHORTLY AFTER TAU 48, AND ACCELERATE SOUTHEASTWARD
THROUGH THE REMAINDER OF THE FORECAST PERIOD ALONG THE SOUTHERN
PERIPHERY OF THE STR. IN TERMS OF INTENSITY, THE ENVIRONMENT IS
VERY FAVORABLE FOR THE ONSET OF RAPID INTENSIFICATION (RI), WITH NO
SIGNIFICANT CHANGES EXPECTED FOR THE NEXT 36 HOURS OR SO. THE
FORECAST EXPLICITLY CALLS FOR RI, WITH THE SYSTEM REACHING A PEAK OF
AT LEAST 80 KNOTS BY TAU 36, WITH SOME RI GUIDANCE INDICATING A
POTENTIAL FOR A PEAK OVER 20 KNOTS HIGHER. AFTER REACHING PEAK
INTENSITY AROUND TAU 36, TC 19P WILL LINGER AT THE PEAK AND BEGIN
TO SLIGHTLY WEAKEN BY TAU 48 AS IT STARTS TO FEEL THE IMPACT OF
SHARPLY AND RAPIDLY INCREASING SHEAR. SUBTROPICAL TRANSITION (STT)
IS EXPECTED TO BEGIN AROUND TAU 60, WHEN SHEAR IS FORECAST TO
INCREASE TO OVER 35 KNOTS, THE SYSTEM CROSSES THE 26C ISOTHERM AND
MID-LEVEL DRY AIR WILL QUICKLY MOVE IN TO SMOTHER THE VORTEX. RAPID
WEAKENING WILL ACCOMPANY THE STT PHASE, WITH THE SYSTEM WEAKENING
TO 45 KNOTS AS IT COMPLETES STT SOMETIME BETWEEN TAU 72 AND TAU 96
FAR TO THE SOUTHEAST OF TONGA. 

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE IS IN
GOOD AGREEMENT THROUGH THE ENTIRE FORECAST PERIOD. CROSS-TRACK
SPREAD INCREASES GRADUALLY TO 135NM AT TAU 48 WHEN THE SYSTEM
ROUNDS THE RIDGE AXIS, ONLY INCREASING SLIGHTLY THEREAFTER TO 175NM
BY THE END OF THE FORECAST PERIOD. ALONG-TRACK SPREAD IS
SURPRISINGLY LOW THROUGHOUT THE FORECAST. THE JTWC FORECAST TRACK
IS PLACED JUST WEST OF THE CONSENSUS MEAN THROUGH THE FORECAST
PERIOD WITH HIGH CONFIDENCE. ALL MEMBERS OF THE INTENSITY CONSENSUS
AGREE ON THE FACT THAT THE SYSTEM WILL INTENSIFY TO A PEAK BETWEEN
TAU 36 AND TAU 48 BUT DISAGREE ON THE ACTUAL PEAK INTENSITY. THE
SHIPS GUIDANCE IS ON THE LOW END OF THE ENVELOPE, SHOWING PEAKS
BETWEEN 55-65 KNOTS, WHILE THE HAFS-A, HWRF, COAMPS-TC AND
CONSENSUS MEAN PEAK BETWEEN 70-80 KNOTS. ADDITIONALLY, THE CTR1,
RICN, AND DTOP RI AIDS ARE ALL TRIPPED ON THIS CYCLE, SHOWING PEAKS
AS HIGH AS 100 KNOTS. THE JTWC FORECAST GENERALLY FOLLOWS THE RI
GUIDANCE BUT AT A SLIGHTLY SLOWER RATE OF INTENSIFICATION, MOST
CLOSELY FOLLOWING THE HAFS-A GUIDANCE. AFTER THE PEAK, ALL OF THE
GUIDANCE AGREES ON A STEADY AND RAPID WEAKENING AND THE JTWC
FORECAST FOLLOWS THE CONSENSUS MEAN AFTER TAU 48.  

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