WDPS31 PGTW 202100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 10P (TEN) WARNING NR 
001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.2S 161.8E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 246 NM WEST-NORTHWEST OF NOUMEA, NEW
CALEDONIA
   MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 17 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
AS THE SUN IS RISING OVER 10P NOW, ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY WAS USED, WHICH DEPICTS A PARTIALLY EXPOSED LOW
LEVEL CIRCULATION CENTER (LLCC) WITH DEEP CONVECTION LIMITED TO THE
EASTERN SEMICIRCLE AND DISPLACED TO THE NORTH. A FORTUITOUS SUITE
OF SSMIS MICROWAVE IMAGERY, SPECIFICALLY THE 201815Z 89GHZ COLOR
COMPOSITE INDICATE THE SYSTEM IS BEING INFILTRATED BY DRY AIR FROM
THE WEST WHICH HAS ERODED MUCH OF ITS CORE CONVECTION. A BULLSEYE
201128Z ASCAT-B SCATTEROMETERY IMAGE INDICATES A SLIGHT NORTH-SOUTH
ELONGATION ALONG WITH AN ASYMMETRIC WIND FIELD OF 35-40 KTS TO THE
SOUTH OF THE LLCC. BASED ON THIS IMAGE AND A MORE RECENT 201407Z
AMSR2 RADIOMETERY IMAGE, IT IS BELIEVED THE PEAK INTENSITY OF 10P
OCCURRED NEAR 201200Z. THE INITIAL POSITION IS PLACED WITH MEDIUM
CONFIDENCE BASED ON EIR AND SSMIS IMAGERY. THE INITIAL INTENSITY OF
35 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON ASCAT, AMSR2 AND
PGTW DVORAK INTENSITY ESTIMATES ALL OF WHICH INDICATE 35KTS.

INITIAL WIND RADII BASIS: 201128Z ASCAT-B SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: NEAR EQUATORIAL RIDGE (NER) TO THE
NORTH

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

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 30+ KTS
   SST: 26-27 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 10P IS FORECAST TO TRACK SOUTHEASTWARD
UNDER THE FADING INFLUENCE OF A NER TO THE NORTH. THE MARGINAL
ENVIRONMENT AROUND 10P IS CHARACTERIZED BY HIGH VERTICAL WIND SHEAR
(VWS) AND DRY AIR ENTRAINMENT, COMPETING WITH WARM SEA SURFACE
TEMPERATURES (SST) AND MODERATE UPPER LEVEL OUTFLOW. OVER THE NEXT
12 HOURS, THIS ENVIRONMENT COULD RESULT IN BRIEF INTENSIFICATION,
BUT WILL LIKELY RESULT IN STAGNATION. AFTER TAU 12, 10P BEGINS TO
TRANSITION TO THE STEERING INFLUENCE OF A SUBTROPICAL RIDGE (STR)
BUILDING TO THE EAST, BY TAU 24 THE SYSTEM WILL BE NEAR THE 23RD
PARALLEL AND WILL TAKE A SHARP POLEWARD TURN. AS 10P BEGINS TO
TRACK GENERALLY SOUTHWARD, DRY AIR ENTRAINMENT AND VWS WILL
OVERWHELM THE SYSTEM RESULTING IN A GRADUAL WEAKENING TREND AND
EVENTUAL DISSIPATION BY TAU 36, THROUGH TAU 48 THE SYSTEM WILL
CONTINUE WEAKENING AS IT PROGRESSES POLEWARD.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN GOOD AGREEMENT THAT 10P
WILL TRACK SOUTHEASTWARD THROUGH TAU 24 UNTIL A CHANGE IN STEERING
INFLUENCE OCCURS AFTER WHICH, THE SYSTEM TAKES A SHARP POLEWARD
TURN THROUGH THE FORECAST PERIOD. THERE IS SLIGHT CROSS TRACK
SPREADING AFTER THE POLEWARD TURN THAT IS BOTH UNSURPRISING AND
MINIMAL IN MAGNITUDE, SHOWING 112NM AT TAU 48. RELIABLE MODEL
INTENSITY GUIDANCE IS IN FAIR AGREEMENT THROUGH TAU 24 WITH MEMBERS
CENTERING ON 35KTS WITH GFS AND HWRF INDICATING MINIMAL
INTENSIFICATION THROUGH TAU 12 AND COAMPS-TC (GFS VERSION)
INDICATING WEAKENING. AFTER TAU 24, ALL MEMBERS INDICATE A
WEAKENING TREND THROUGH THE FORECAST PERIOD. FOR THESE REASONS BOTH
THE JTWC TRACK AND INTENSITY FORECAST ARE PLACED WITH MEDIUM
CONFIDENCE.

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