WDXS31 PGTW 250900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 14S (VERNON) WARNING NR 001// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 13.8S 94.4E INITIAL INTENSITY: 45 KTS GEOGRAPHIC REFERENCE: 176 NM SOUTHWEST OF COCOS ISLANDS, AUSTRALIA MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 08 KTS SIGNIFICANT WAVE HEIGHT: 16 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A VERY COMPACT SYSTEM, WHICH OVER THE PREVIOUS FEW HOURS HAS RAPIDLY CONSOLIDATED AND INTENSIFIED INTO A TROPICAL CYCLONE. THE PREVIOUS SIX-HOUR INTENSITY FROM 250000Z HAS BEEN REANALYZED AND IS NOW ASSESSED TO HAVE BEEN 35 KNOTS, INDICATING A 10 KNOT INTENSIFICATION IN THE LAST SIX HOURS. IN THE PAST COUPLE OF HOURS, ANIMATED MSI AND EIR SUGGEST THE DEVELOPMENT OF A DIMPLE AND WARM SPOT, SUGGESTIVE OF THE POSSIBILITY OF A NASCENT EYE FEATURE. HOWEVER, THE LACK OF ANY RECENT MICROWAVE IMAGERY PRECLUDES AND FULL UNDERSTANDING OF THE STORM STRUCTURE. THE INITIAL POSITION IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON AN EXTRAPOLATION OF THE WELL DEFINED LOW LEVEL CIRCULATION CENTER (LLCC) IN A 250320Z ASCAT-C BULLSEYE PASS. THE INITIAL INTENSITY IS ASSESSED AT 45 KNOTS WITH MEDIUM CONFIDENCE, WELL ABOVE THE PGTW T2.5 ESTIMATE, BUT WELL BELOW THE T4.0 FROM APRF. CONSIDERABLE WEIGHT WAS GIVEN TO THE PREVIOUSLY MENTIONED ASCAT-C DATA WHICH INDICATED A FEW 45 KNOT WIND BARBS VERY NEAR THE CORE, THOUGH WITH SUCH A COMPACT CORE, ITS POSSIBLE THERE ARE HIGHER WINDS PRESENT THAT THE SCATTEROMETER RESOLUTION CAN'T PICK UP. ANALYSIS REVEALS A FAVORABLE ENVIRONMENT OF LOW VERTICAL WIND SHEAR, WARM SSTS, AND GOOD EQUATORWARD OUTFLOW ALOFT. INITIAL WIND RADII BASIS: SCATTEROMETER DATA CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) TO THE SOUTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS APRF: T4.0 - 65 KTS FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 0-5 KTS SST: 27-28 CELSIUS OUTFLOW: MODERATE EQUATORWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: HIGH 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY. FORECAST DISCUSSION: THROUGH THE FIRST 24 HOURS OF THE FORECAST, THERE IS GOOD CERTAINTY, AS THE PRIMARY DRIVER OF THE TRACK WILL BE THE STR CENTERED TO THE SOUTH. HOWEVER, THE PRESENCE OF INVEST 93S, CURRENTLY APPROXIMATELY 300NM TO THE NORTHWEST, WILL HAVE A SIGNIFICANT AND HIGHLY UNCERTAIN IMPACT ON THE FORECAST AFTER TAU 24. CURRENT DETERMINISTIC AND ENSEMBLE GLOBAL MODELS SUGGEST THAT INVEST 93S WILL TRACK TO THE NORTH SIDE OF TC 14S, AND BEGIN BINARY INTERACTION IN THE NEXT 12 HOURS, SLOWLY STARTING TO WRAP IN CLOSER AND CLOSER TO TC 14S. ONCE 93S PASSES TO THE EAST OF DUE NORTH AROUND TAU 36, TC 14S IS EXPECTED TO TURN EQUATORWARD AS THE TWO SYSTEMS APPROACH CPA AND BEGIN TO FUJIWARA AROUND ONE ANOTHER. TC 14S WILL LIKELY PERFORM A CLOCKWISE LOOP THROUGH TAU 48, AND AGAIN TURN POLEWARD AFTER THIS POINT AS IT STARTS TO MERGE WITH INVEST 93S. MERGER IS EXPECTED TO BE COMPLETE BY AROUND TAU 60, AND TC 14S WILL VASTLY INCREASE IN SIZE. A PASSING MID-LATITUDE TROUGH WILL BREAK THE STEERING RIDGE AROUND THE SAME TIME, AND BY TAU 72, TC 14S WILL START MOVING POLEWARD ALONG THE WESTERN SIDE OF THE STR NOW CENTERED TO THE EAST. DUE THE VERY SMALL NATURE OF THE SYSTEM, SMALL-SCALE CHANGES IN THE ENVIRONMENT WILL HAVE OUTSIZED EFFECTS AND THUS THE INTENSITY FORECAST IS VERY UNCERTAIN. THE OVERALL ENVIRONMENT IS FAVORABLE INTENSIFICATION AND THE RECENT EVOLUTION OF THE SYSTEM SUGGESTS THAT WITHOUT SIGNIFICANT ENVIRONMENTAL CHANGES EXPECTED, IT SHOULD CONTINUE TO STEADILY INTENSIFY. ALL RAPID INTENSIFICATION AIDS WERE TRIGGERED WITH THIS CYCLE, AND THE FORECAST CALLS FOR A RAPID INTENSIFICATION TO 80 KNOTS WITHIN THE NEXT 36 HOURS. EVEN THOUGH THE ENVIRONMENT REMAINS FAVORABLE, THE DISRUPTION CAUSED BY THE BINARY INTERACTION WITH INVEST 93S WILL PUT THE BRAKES ON THE INTENSIFICATION TREND FROM TAU 36 TO 48 AS THE SYSTEMS MERGE. ONCE MERGED INTO ONE LARGER SYSTEM, TC 14S WILL RESUME INTENSIFYING AS IT MOVES POLEWARD AND TAPS INTO ROBUST POLEWARD OUTFLOW INTO THE BASE OF A PASSING MID-LATITUDE TROUGH, REACHING A SECOND PEAK OF 95 KNOTS BY TAU 96, BEFORE WEAKENING SLIGHTLY AT THE END OF THE FORECAST PERIOD DUE TO STEADILY INCREASING SHEAR. MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE DEPICTS A LARGE AMOUNT OF UNCERTAINTY, PARTICULARLY AFTER TAU 36 WHEN THE BINARY INTERACTION BEGINS. MOST OF THE GUIDANCE SUPPORTS THE QUASI-STATIONARY OR LOOPING MOTION BETWEEN ROUGHLY TAU 36 TO 48, BUT DIFFER ON HOW THE SYSTEM EMERGES OUT OF THE MERGER, RESULTING IN A VERY LARGE SPREAD IN THE GUIDANCE ENVELOPE AFTER TAU 72. THE UKMET MARKS THE EASTERN EDGE OF THE ENVELOPE, WHILE GFS MARKS THE WESTERN. THE JTWC FORECAST TRACKS THE GFS SOLUTION THROUGH TAU 36, THEN CLOSER TO THE HWRF THEREAFTER THOUGH HEDGES TOWARDS THE WESTERN SIDE OF THE ENVELOPE AFTER TAU 48. CONFIDENCE IS HIGH IN THE FIRST 24 HOURS, THEN LOW THEREAFTER DUE TO THE UNCERTAINTY SURROUNDING THE BINARY INTERACTION. THE INTENSITY GUIDANCE IS SIMILARLY UNCERTAIN, WITH A WIDE RANGE IN PEAK INTENSITIES BETWEEN 50 KNOTS AND 115 KNOTS. THE JTWC FORECAST TRACKS THE RI35 LINE THROUGH 36 HOURS, THEN FLATTENS OUT CLOSER TO THE DECAY SHIPS THROUGH TAU 48, BUT THEN ABOVE ALL THE GUIDANCE THROUGH THE REMAINDER OF THE FORECAST PERIOD. CONFIDENCE IS LOW THROUGH THE FORECAST AGAIN DUE TO UNCERTAINTY ASSOCIATED WITH THE SMALL SIZE OF THE SYSTEM AND THE IMPACTS OF THE BINARY INTERACTION. FORECAST CONFIDENCE: TRACK 0 - 72 HR: LOW TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: LOW INTENSITY 72-120 HR: LOW// NNNN