WDPN32 PGTW 080300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 14W (MUIFA) WARNING NR 007// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 17.1N 133.0E INITIAL INTENSITY: 40 KTS GEOGRAPHIC REFERENCE: 634 NM SOUTH-SOUTHEAST OF KADENA AB MOVEMENT PAST 6 HOURS: WESTWARD AT 07 KTS SIGNIFICANT WAVE HEIGHT: 15 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN ASYMMETRIC SYSTEM WITH PERSISTENT DEEP CONVECTION DISPLACED TO THE SOUTH OF A PARTIALLY OBSCURED LOW LEVEL CIRCULATION CENTER (LLCC). ANIMATED WATER VAPOR IMAGERY, CIMSS ATMOSPHERIC MOTION VECTORS (AMVS) AND JTWC HAND ANALYSIS REVEALS AN ELONGATED TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) POSITIONED TO THE NORTH OF THE LLCC, IMPARTING A WEST-NORTHWEST SHEAR VECTOR OVER TOP OF THE SYSTEM, AND SOME CONVERGENCE ALOFT TO THE NORTHWEST, LEADING TO THE CURRENT ASYMMETRIC STRUCTURE OF THE SYSTEM. A EARLIER 072124Z SSMIS 91GHZ MICROWAVE IMAGE DEPICTED THE LLCC FULLY EXPOSED TO THE NORTH OF SLIGHTLY CURVED DEEP CONVECTION, AND EXTRAPOLATION OF THIS FEATURE AND ANALYSIS OF LOW-LEVEL SPIRAL BANDS LENT MEDIUM CONFIDENCE TO THE INITIAL POSITION. REANALYSIS OF PREVIOUS POSITIONS BASED ON EARLIER SCATTEROMETER DATA WITH WINDS LESS THAN 35 KNOTS RESULTED IN A DOWNWARD ADJUSTMENT IN THE PREVIOUS ANALYSES. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A BLEND OF AGENCY DVORAK CURRENT INTENSITY ESTIMATES, THE ADT AND THE SATELLITE CONSENSUS. OVERALL THE CURRENT ENVIRONMENT IS GENERALLY FAVORABLE WITH THE EXCEPTION OF THE SIGNIFICANT TILT AND ASYMMETRIC CORE STRUCTURE. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: SOUTHERN SIDE OF MID-LEVEL SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS RJTD: T2.0 - 30 KTS KNES: T3.5 - 55 KTS CIMSS SATCON: 44 KTS AT 072125Z CIMSS ADT: 37 KTS AT 072350Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 30-31 CELSIUS OUTFLOW: STRONG EQUATORWARD OTHER FACTORS: WEAK POLEWARD OUTFLOW INTO A TUTT CELL FAR TO THE NORTHEAST ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM 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. HOWEVER, THE PREVIOUS INTENSITY ESTIMATES HAVE BEEN LOWERED FIVE KNOTS BASED ON REANALYSIS. FORECAST DISCUSSION: TS MUIFA HAS TRACKED WESTWARD OVER THE PAST 12 HOURS OR SO ALONG THE SOUTHERN SIDE OF AN ELONGATED LOW TO MID-LEVEL SUBTROPICAL RIDGE (STR) TO THE NORTH. THIS GENERAL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT 12 HOURS BUT THEN THE SYSTEM IS EXPECTED TO TURN SHARPLY NORTHWESTWARD AS THE STR BUILDS SOUTH OF HONSHU AND REORIENTS TO A MORE SOUTHEAST TO NORTHWEST AXIS. TRACK MOTION SLOWS AFTER TAU 72 AS THE STEERING PATTERN WEAKENS SLIGHTLY, THEN THE SYSTEM TURNS SHARPLY POLEWARD AND ACCELERATES INTO THE EAST CHINA SEA AS THE STEERING RIDGE ERODES TO THE EAST AHEAD OF A VERY DEEP UPPER-LEVEL TROUGH MOVING IN FROM THE WEST. IN THE SHORT-TERM, THE CONVERGENCE ALOFT TO THE NORTHWEST AND PERSISTENT MID-LEVEL SHEAR (15 KNOTS) MEANS THE SYSTEM WILL BE SLOW TO CONSOLIDATE AND INTENSIFICATION IS EXPECTED TO BE RATHER SLOW FOR THE NEXT 12 HOURS. BUT THEN THE GLOVES COME OFF, AS THE TUTT-CELL SLIDES TO A POSITION TO THE NORTHWEST OF THE LLCC, ALLOWING FOR ESTABLISHMENT OF A ROBUST POLEWARD OUTFLOW CHANNEL, WHICH WILL AMPLIFY AND COMPLEMENT THE EXISTING STRONG EQUATORWARD CHANNEL. AT THE SAME TIME, HIGH RESOLUTION MODELS SUGGEST CONVECTIVE HOT TOWERS FIRING OFF AND ROTATING UPSHEAR, LEADING TO AXISYMMETRIZATION BY TAU 18, MARKING THE ONSET OF RAPID INTENSIFICATION (RI). ANIMATED VISIBLE IMAGERY FROM THE 0200Z HOURS SUGGEST THIS PROCESS MAY HAVE ALREADY BEGUN, WITH HOT TOWERS FORMING AROUND THE ASSESSED CENTER. THE SYSTEM WILL PASS OVER A POOL OF RELATIVELY LOWER OHC (BUT STILL AT OR ABOVE 75 JOULES PER KG) AROUND TAU 24, BUT DUE TO THE RELATIVELY QUICK FORWARD SPEED, THIS SHOULD HAVE LITTLE IMPACT OVERALL. THE SYSTEM REALLY TAKES OFF AROUND TAU 36 AS IT MOVES AN AREA WITH OHC VALUES EXCEEDING 125 JOULES PER KG, AND THE SYSTEM IS EXPECTED TO PEAK AT 120 KNOTS OR POSSIBLY SLIGHTLY HIGHER BY TAU 72. AT THIS POINT, THE SYSTEM WILL MOVE INTO THE AREA PREVIOUSLY VISITED BY STY 12W, WHICH LEFT A MINEFIELD OF COOL, VERY LOW OHC WATER IN ITS WAKE. AS TS 14W ENTERS THIS REGION, IT WILL WEAKEN FAIRLY QUICKLY, EVEN AS SHEAR REMAINS MODERATE AND POLEWARD OUTFLOW REMAINS ROBUST INTO THE DIVERGENT REGION AHEAD OF A SHARP 200MB TROUGH TO THE WEST. THE COMBINATION OF THESE FEATURES HOWEVER MEANS THAT TS 14W WILL REMAIN A STRONG TYPHOON ENTERING THE EAST CHINA SEA. MODEL DISCUSSION: TRACK GUIDANCE IS IN OVERALL GOOD AGREEMENT ON THE OVERALL SCENARIO, WITH DETERMINISTIC GUIDANCE TRACKERS GRADUALLY SPREADING TO A MODEST 135NM BT TAU 72. ENSEMBLE GUIDANCE SHOWS A BIT MORE SPREAD DURING THE FIRST 72 HOURS, WITH THE ECMWF ENSEMBLE IN PARTICULAR SHOWING A FAIRLY LARGE FAN OF POTENTIAL TRACKS. THE DETERMINISTIC ENVELOPE IS CONSTRAINED BY JGSM ON THE RIGHT AND UKMET AND NAVGEM ON THE LEFT. IN THE EXTENDED FORECAST PERIOD, THE GUIDANCE SHOWS INCREASED UNCERTAINTY, WITH ACROSS AND ALONG-TRACK SPREAD BOTH INCREASING TO NEARLY 300NM BY TAU 120. THE JTWC FORECAST LIES A BIT TO THE LEFT OF THE CONSENSUS MEAN, CLOSELY TRACKING THE ECMWF THROUGH THE FIRST 72 HOURS WITH HIGH CONFIDENCE, THOUGH CONFIDENCE DECREASES THROUGH TAU 120 DUE TO LARGE SPREAD IN THE GUIDANCE. INTENSITY GUIDANCE IS IN MARGINAL AGREEMENT, WITH THE NON-COUPLED GUIDANCE SUCH AS THE DECAY-SHIPS INDICATING A MAXIMUM NEAR 90 KNOTS, WHILE THE HWRF AND COAMPS-TC COUPLED MODELS SUGGEST A MUCH HIGHER PEAK, AT 120 KNOTS. MULTIPLE RI AIDS ARE BEING TRIGGERED WITH THIS RUN AS WELL, PROVIDING INCREASED CONFIDENCE IN THE FORECAST ONSET OF RI. THE JTWC FORECAST CALLS FOR A SLIGHTLY SLOWER RATE OF INTENSIFICATION THROUGH TAU 12 THAN MOST OF THE RI GUIDANCE AS THE SYSTEM NEEDS SOME TIME TO CONSOLIDATE. FOR THERE ON OUT THE JTWC FORECAST TRACKS THE RI GUIDANCE AND MATCHES THE PEAK INTENSITY OF THE HWRF AND COAMPS-TC. CONFIDENCE IN THE INTENSITY FORECAST IS MEDIUM THROUGH TAU 72, THEN LOW DUE TO UNCERTAINTY IN THE AMOUNT OF WEAKENING THE SYSTEM WILL EXPERIENCE NEAR AFTER TAU 72 DUE TO INTERACTION WITH THE COLD POOL. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN