WDXS31 PGTW 140900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 20S (TWENTY) WARNING NR 
002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.3S 100.6E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 285 NM SOUTHEAST OF COCOS ISLANDS
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 18 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS DEEP CENTRAL
CONVECTION WITH FORMATIVE BANDING WRAPPING INTO AN OBSCURED
LOW-LEVEL CIRCULATION (LLC). THE MAJORITY OF CONVECTION REMAINS
POLEWARD, AS A NEW TOWER BUILDS ON THE WESTERN SIDE AND WRAPS
AROUND THE LLC AS INDICATED ON A 140642Z ATMS 88.2GHZ IMAGE. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE USING THE MICROWAVE
EYE PRESENTED IN BOTH THE 140425Z GMI 37GHZ AND 89GHZ IMAGES AND
THE PREVIOUSLY MENTIONED ATMS IMAGE. THE INITIAL INTENSITY IS SET
WITH MEDIUM CONFIDENCE BASED UPON PGTW FIX AND SATCON, AS ADT AND
APRF FIXES REMAIN SLIGHTLY LOWER. ANALYSIS INDICATES A CONTINUED
FAVORABLE ENVIRONMENT WITH LOW (5-10KTS) VWS, WARM SST, AND
MODERATE RADIAL OUTFLOW ALOFT. TC 20S IS TRACKING ALONG THE
NORTHWEST PERIPHERY OF THE STR TO THE SOUTHEAST.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) ANCHORED TO THE
SOUTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   APRF: T2.0 - 30 KTS
   CIMSS SATCON: 50 KTS AT 140639Z
   CIMSS ADT: 34 KTS AT 140540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   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 20S REMAINS ON A WEST-SOUTHWESTWARD TRACK
AS IT CONTINUES TO BE STEERED BY THE STR TO THE SOUTHEAST FOR THE
REMAINDER OF THE FORECAST. THE FAVORABLE ENVIRONMENT WILL HELP THE
SYSTEM INTENSIFY SLIGHTLY THROUGH TAU 36 TO A PEAK OF 50KTS IN THE
NEAR FORECAST TAUS. AFTERWARD, INCREASING VWS WILL BEGIN OFFSETTING
THE OTHER DYNAMICS AND BEGIN ERODING THE SYSTEM DOWN TO 30KTS
BETWEEN TAUS 72 AND 96.  

MODEL DISCUSSION: NUMERICAL MODELS HAVE BEEN IN LOOSE AGREEMENT FOR
SEVERAL MODEL RUNS, WITH NAVGEM NOW TURNING CLOSER TOWARDS THE
OVERALL MAIN MODEL SOLUTIONS, WHEREAS BEFORE, IT WAS AN EXTREME
LEFT OUTLIER WITH AFUM SETTING UP A NEAR BIFURCATION. AFUM IS NOW
THE SOLE LEFT OUTLIER THROUGH TAU 48. AFTERWARDS, AFUM MAKES A
SHARP TURN POLEWARD AND THEN QUICKLY TRIES TO TURN EQUATORWARD BY
TAU 96, WHICH IS SKEWING THE CONW TRACK. A MAJORITY OF THE MODEL
MEMBERS CONTINUE INDICATING TC 20S WILL REMAIN ON A
WEST-SOUTHWESTWARD TRACK WITH GFS AND ECMF PAIRING CLOSELY
TOGETHER. BECAUSE OF THIS, THE JTWC TRACK FORECAST IS LAID WITH
MEDIUM CONFIDENCE, WHICH FOLLOWS CLOSELY ALONG WITH THESE
SOLUTIONS. THESE SOLUTIONS REMAIN JUST NORTH OF THE MODEL
CONSENSUS, OFFSETTING THE SOUTHWARD OUTLIERS OF NAVGEM, AFUM, AND
THE UKMET DETERMINISTIC AND ENSEMBLE MODELS. THERE IS LOW
CONFIDENCE IN THE TRACK AND INTENSITY FORECAST BEYOND TAU 72, WHERE
THE ALONG-TRACK SPREAD DIVERGES RAPIDLY AS THE SHEAR INCREASES AND
THE SYSTEM BEGINS WEAKENING. 

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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