WDPN31 PGTW 271500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W (JANGMI) WARNING NR 002// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 10.3N 137.2E INITIAL INTENSITY: 25 KTS GEOGRAPHIC REFERENCE: 72 NM NORTHWEST OF YAP MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 07 KTS SIGNIFICANT WAVE HEIGHT: 11 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: TROPICAL DEPRESSION (TD) 06W (JANGMI) CONTINUES TO PRESENT AS A BROAD, ASYMMETRIC SYSTEM WITH AN ILL-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC). DEEP CONVECTIVE CELLS CONTINUE TO FLARE INTERMITTENTLY, PRIMARILY RESTRICTED TO THE WESTERN SEMICIRCLE OF THE CIRCULATION. THE CONVECTIVE SUPPRESSION ALONG THE EASTERN FLANK IS ATTRIBUTABLE TO MID-LEVEL DRY AIR AS INDICATED BY THE YAP 1200Z SOUNDING, WHICH DEPICTED TWO DISTINCT LAYERS OF SUBSIDED DRY AIR IN THE MID-LEVELS, AS WELL AS SOUTH-SOUTHWESTERLY WINDS OF 60-70 KNOTS BETWEEN 600-450MB. IN COMPARISON WITH THE SOUNDING, THE HWRF APPEARS TO BE THE ONLY MODEL INITIALIZING THE VERTICAL WIND PROFILE ACCURATELY. SO, WHILE THE LOW-LEVEL VORTEX IS ILL-DEFINED, BROAD AND RELATIVELY WEAK, THE MID-LEVEL VORTEX IS MUCH STRONGER, PARTICULARLY ON THE EASTERN SIDE, WHICH IS GENERATING STRONG RELATIVE VORTICITY, HELPING TO ALIGN AND CONSOLIDATE THE VORTEX. A RECENT SCATTEROMETER PASS REVEALED THE LLCC TO BE NORTHWEST OF YAP AND PROVIDED MEDIUM CONFIDENCE IN THE INITIAL POSITION. THE INITIAL INTENSITY IS MAINTAINED AT 25 KNOTS WITH MEDIUM CONFIDENCE, BASED ON A BLEND OF THE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES NOTED BELOW, VALIDATED BY THE SCATTEROMETER DATA WHICH INDICATED MAXIMUM, NON- FLAGGED WINDS OF 25 KNOTS. ENVIRONMENTAL CONDITIONS CONTINUE TO BE FAVORABLE, CHARACTERIZED BY WARM SEA SURFACE TEMPERATURES (SSTS), LOW DEEP-LAYER VERTICAL WIND SHEAR (VWS), AND MODERATE POLEWARD AND EQUATORWARD OUTFLOW ALOFT, OFFSET BY DRY MID-LEVEL AIR INTRUSION ALONG THE EASTERN FLANK, THE BROAD NATURE OF THE LLCC, AND THE VERTICALLY TILTED VORTEX. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: WESTERN FLANK OF A LOW- TO MID-LEVEL MESOSCALE RIDGE TO THE SOUTH OF GUAM. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T1.0 - 25 KTS RJTD: T2.5 - 35 KTS RCTP: T2.0 - 30 KTS KNES: T1.0 - 25 KTS CIMSS ADT: 30 KTS AT 271200Z CIMSS AIDT: 30 KTS AT 271200Z CIMSS D-MINT: 23 KTS AT 270905Z CIMSS D-PRINT: 24 KTS AT 271230Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE POLEWARD AND EQUATORWARD OTHER FACTORS: VORTEX IS BROAD AND VERTICALLY ASYMMETRIC. ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: NOT APPLICABLE 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TD 06W IS CURRENTLY BEING DRIVEN NORTH-NORTHWESTWARD ALONG THE WESTERN BOUNDARY OF A LOW- TO MID-LEVEL SUBTROPICAL RIDGE (STR) CENTERED TO THE SOUTH OF GUAM. AS TD 06W CONTINUES TO INTENSIFY, THE STR WILL BUILD AND EXPAND NORTHWARD IN RESPONSE, DEVELOPING INTO A NORTH-SOUTH ORIENTED RIDGE WITH AN AXIS ALONG THE MARIANAS ISLAND CHAIN. BY TAU 36, THE STR TO THE EAST IS FORECAST TO REORIENT TO A MORE NORTHWEST-SOUTHEAST AXIS AND CONTINUES TO BUILD, WHILE A SECOND STR OVER SOUTHEASTERN CHINA RECEDES WESTWARD, INDUCING A WEAKNESS IN THE STEERING PATTERN IN THE VICINITY OF OKINAWA. TD 06W WILL TURN ONTO A NORTHWESTWARD TRAJECTORY FROM TAU 36 TO TAU 72, DRIVEN ALONG THE WESTERN FLANK OF THE STR TO THE EAST AND TOWARDS THE OROGRAPHICALLY ASSISTED WEAKNESS IN THE RIDGING PATTERN. BY TAU 72, A MID-LATITUDE TROUGH WILL MOVE EASTWARD ACROSS KOREA, DEEPENING THE WEAKNESS IN THE RIDGE NEAR OKINAWA WHILE SIMULTANEOUSLY SHIFTING THE STR FURTHER EAST. THIS WILL ALLOW TD 06W TO BEGIN TO RECURVE, APPROACHING THE RIDGE AXIS BY TAU 120. THE PRIMARY DRIVER OF TRACK VARIANCE DURING THIS PHASE OF THE FORECAST IS THE TIMING AND AMPLITUDE OF THE TROUGH PASSAGE. THE ECMWF DEPICTS A STRONGER, DEEPER TROUGH, WHICH RESULTS IN ACCELERATED RECURVATURE AND TRACK SPEED AFTER TAU 96. CONVERSELY, THE GFS DEPICTS A WEAKER TROUGH, WITH A RESULTING SLOWER TRACK THAT DELAYS RECURVATURE BY APPROXIMATELY 12 HOURS AND EXTENDS FURTHER WEST, RESULTING IN A DIRECT IMPACT ON OKINAWA. REGARDING INTENSITY, THE SYSTEM REMAINS DISORGANIZED WITH A VERTICALLY MISALIGNED VORTEX. THE MESOSCALE MODELS SUGGEST IT WILL TAKE 24-36 HOURS FOR THE VORTEX TO ACHIEVE VERTICAL ALIGNMENT. DURING THIS WINDOW, THE SYSTEM IS EXPECTED TO INTENSIFY AT THE CLIMATOLOGICAL RATE OF ONE T-NUMBER PER DAY, FORECAST TO REACH 35 KNOTS IN 24 HOURS. THEN AFTER TAU 36, THE SYSTEM WILL INTENSIFY MORE RAPIDLY, WITH RAPID INTENSIFICATION (RI) EXPLICITLY FORECAST BETWEEN TAU 48 AND TAU 72, AS THE SYSTEM PASSES OVER WARM, HIGH OCEAN HEAT CONTENT (OHC) WATERS. AFTER TAU 72, THE SYSTEM WILL BEGIN MOVING OVER A TONGUE OF COOL SSTS EAST OF OKINAWA, WHICH ACCOMPANIED BY A MARGINAL INCREASE IN SHEAR WILL RESULT IN A GENERAL WEAKENING TREND AFTER TAU 96 AS THE SYSTEM APPROACHES CPA TO OKINAWA. AT THE SAME TIME HOWEVER, THE WIND RADII ARE FORECAST TO EXPAND SIGNIFICANTLY AFTER TAU 96, PARTICULARLY ON THE NORTH AND WESTERN PERIPHERY. MODEL DISCUSSION: THE CONSENSUS PACKAGE REMAINS CONSISTENT WITH THE PREVIOUS MODEL RUN, DEPICTING THREE GROUPINGS OF MODELS. THE FIRST GROUP, CONSISTING OF NAVGEM, GALWEM, AND UKMET ENSEMBLE IS CLUSTERED APPROXIMATELY 150NM WEST OF THE CENTER GROUP, WHICH HAS SHIFTED EASTWARD BY APPROXIMATELY 20NM SINCE THE 06Z MODEL RUN. THE CENTER GROUP OF MODELS CONSISTS OF THE GFS, ECMWF, ECEPS, EC-AIFS, EC-AIFS ENSEMBLE, AND THE CONSENSUS MEAN. THE EASTERN GROUP LIES APPROXIMATELY 75NM EAST OF THE CENTER GROUP AND CONSISTS OF GEFS, FGNI, JGSM AND JENI. CROSS-TRACK SPREAD BETWEEN THE OUTLIER GROUPS IS 215NM AT TAU 72 AND 450NM AT TAU 120. CROSS-TRACK UNCERTAINTY IS MUCH LESS IN THE CENTER GROUPING, MAINTAINING APPROXIMATELY 100NM FROM TAU 72 THROUGH TAU 120. THE JTWC FORECAST IS POSITIONED ON THE EASTERN EDGE OF THE INNER GROUPING ENVELOPE, CLOSELY ALIGNED WITH THE ECMWF AND EC-AIFS TRACKERS. CONFIDENCE IN THE TRACK FORECAST IS HIGH THROUGH TAU 72, AND MEDIUM THEREAFTER. INTENSITY GUIDANCE IS IN GENERAL AGREEMENT ON THE OVERALL SCENARIO BUT DEPICTS INCREASING UNCERTAINTY IN THE PEAK INTENSITY. HAFS-A IS A LOW-SIDE OUTLIER, DEPICTING AN EARLY PEAK OF 55 KTS AT TAU 60 FOLLOWED BY GENERAL WEAKENING THEREAFTER, WHILE THE HWRF AND CTCX ARE MUCH MORE AGGRESSIVE IN THE NEAR-TERM, DEPICTING RI THROUGH TAU 48, THEN A SLOWER PACE OF INTENSIFICATION THROUGH TAU 84, WHERE THEY BOTH SHOW A 90 KNOT PEAK. THE BULK OF THE GUIDANCE DEPICTS GENERAL WEAKENING AFTER TAU 96. THE JTWC FORECAST IS PLACED ON THE LOWER SIDE OF THE ENVELOPE THROUGH TAU 24 THEN SHIFTS TO TRACK THE HWRF TRACKER THROUGH TAU 96. CONFIDENCE IS MEDIUM THROUGH THE FORECAST PERIOD. FORECAST CONFIDENCE: TRACK 00-72 HR: HIGH TRACK 72-120 HR: MEDIUM INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN