WDPN31 PGTW 202100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (SANVU) WARNING NR 006// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 9.8N 156.3E INITIAL INTENSITY: 45 KTS GEOGRAPHIC REFERENCE: 721 NM EAST-SOUTHEAST OF NAVSTA GUAM MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 06 KTS SIGNIFICANT WAVE HEIGHT: 20 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: AT FIX TIME TROPICAL STORM SANVU (01W) WAS AMIDST THE HOURS OF DIURNAL MAXIMUM CONVECTION. TWO BROAD LOBES OF DEEP AND VIGOROUS CONVECTION SURROUND A LOW LEVEL CIRCULATION CENTER (LLCC) INDICATED ON A 201126Z ASCAT PASS. THE SCATTEROMETRY ALSO REVEALS AN ASYMMETRIC SYSTEM WITH MUCH STRONGER WINDFIELDS OVER THE POLEWARD SEMICIRCLE. THERE IS HOWEVER A STREAM OF WELL-ESTABLISHED SOUTHERLY INFLOW IN THE SOUTHEAST QUADRANT. A 201841Z SSMIS SERIES SHOWS WIDESPREAD DEEP CONVECTION SCATTERED SO WIDELY OVER THE POLEWARD SEMICIRCLE THAT THE NORTHEASTERNMOST CONVECTIVE COMPLEXES MAY BE ROBBING THE CORE OF ENERGY. THE MICROWAVE ALSO SHOWS A GENERAL LACK OF TIGHT ORGANIZATION WITH THE SYSTEM. THE INTENSITY IS ASSESSED BASED ON CONSISTENT SUBJECTIVE DVORAKS FROM ALL THREE AGENCIES FIXING ON THE STORM (RJTD, PGTW, AND KNEWS), AND ALTHOUGH AUTOMATED ASSESSMENTS ARE RUNNING AT OR JUST A LITTLE BIT HIGHER THAN SUBJECTIVE ASSESSMENTS THEY STILL SUPPORT THEM. ADT CI IS THE FURTHEST OUTLIER AT T3.5 BUT RAW VALUES ARE FALLING. CIMMS NEW OPEN-AIIR AUTOMATED INTENSITY ESTIMATOR HAS BEEN TRACKING THE SYSTEM SOLIDLY THUS FAR AND CAME UP TO 50KTS ON ITS MOST RECENT MEASUREMENT. NOT A HUGE CONCERN HOWEVER CONSIDERING THE DIURNAL PEAK. ANIMATED WATER VAPOR IMAGERY SHOWS A SHARP DRY LINE TO THE NORTHWEST OF THE SYSTEM AND THE BEGINNINGS OF IMPINGEMENT ON OUTFLOW OVER THAT QUADRANT. OTHERWISE OUTFLOW IS VIGOROUS. INITIAL WIND RADII BASIS: A 201126Z ASCAT PASS. CURRENT STEERING MECHANISM: SANVU IS LEAVING THE STEERING FROM THE NEAR EQUATORIAL RIDGE AND TRANSITIONING TOWARDS AN AREA WHERE THE SUBTROPICAL RIDGE WILL BE THE DOMINANT STEERING FORCE. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS RJTD: T2.5 - 35 KTS KNES: T3.0 - 45 KTS CIMSS SATCON: 50 KTS AT 201521Z CIMSS ADT: 55 KTS AT 201730Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE VWS: 5-10 KTS SST: 28-29 CELSIUS OUTFLOW: STRONG RADIAL OTHER FACTORS: THE STRONG RADIAL RATING IS COMING TO A CLOSE AS OUTFLOW WILL BE DEGRADED OVER THE NORTHWEST SEMICIRCLE. ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: HIGH INITIAL WIND RADII: HIGH 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TS 01W IS ENTERING THE HOURS OF TRUTH. DURING THE NEXT FEW HOURS AS THE SYSTEM TRACKS NORTH OF THE 10TH LATITUDE AND ENTERS THE DIRURNAL DOWNTREND, IT WILL REVEAL THE ACCURACY OF THE DISSIPATION SCENARIO. THE SYSTEM SHOULD ENCOUNTER INCREASING VERTICAL WIND SHEAR (VWS) AND SIGNIFICANTLY DRIER AIR AND BEGIN ITS DOWNTREND. VWS VALUES EXCEED 20KTS NORTH OF THE 11TH LATITUDE 25KTS NORTH OF THE 12TH LATITUDE AND 30KTS OF VWS OVER APRA HARBOR. ALONG TRACK MODELED SOUNDINGS REVEAL AN AVERAGE MID-LEVEL MOSITRE RH OF ONLY FORTY SEVEN PER CENT. ALTHOUGH IT IS INTUITIVELY ODD TO SEE TROPICAL STORMS DISSIPATING UPSTREAM OF THE MARIANAS, IT IS APRIL AND BOTH WATER VAPOR AND TOTAL PRECIPITABLE WATER LOOPS ARE EMPHATIC IN REPRESENTING A HOSTILE ENVIRONMENT BETWEEN SANVU AND GUAM. MODEL GUIDANCE HAS BEEN STEADFAST ABOUT DEPICTING THE SAME SCENARIO...THE SAME MODEL GUIDANCE THAT FAILED TO PREDICT GENESIS. GENESIS HOWEVER WAS LARGELY AN EFFECT OF AN MJO PULSE AND AFTER THAT ROUGH START GUIDANCE HAS CONGEALED WELL. THE FORECAST REMAINS CONSISTENT WITH PREVIOUS ITERATIONS AND THE OVERALL SCENARIO REMAINS STEADY. MODEL DISCUSSION: STATISTICAL DYNAMICAL INTENSITY GUIDANCE (SHIPS) REMAINS INEXPLICABLY HIGH AND IS DISMISSED IN THE INTENSITY FORECAST. THE CAUSE IS A FAILURE TO PREDICT VWS VALUES GREATER THAN 20KT THROUGH TAU 60. NONETHELESS THE BULK OF INTENSITY GUIDANCE IS LOCKED INTO A DECLINING INTENSITY SCENARIO BEGINNING NOW. COAMPS-TC HAS BEEN PERFORMING PARTICULARLY WELL THUS FAR AND MATCHES THE JTWC FORECAST. TRACK GUIDANCE HAS GOOD QUALITATIVE AGREEMENT BUT THE SPREAD IS WIDER THAN NORMAL DUE MOSTLY TO A PRONOUNCED POLEWARD DEVIATION FROM NAVGEM. THERE IS A WEAKNESS BETWEEN THE EASTERN EXTENSION OF THE SUBTROPICAL RIDGE AND THE NEAR EQUATORIAL RIDGE TS 01W IS CURRENTLY LEAVING BUT NO OTHER GUIDANCE INDICATES THAT WEAKNESS IS DEEP ENOUGH TO DRAW THE SYSTEM POLEWARD. THE JTWC TRACK FORECAST STAYS CLOSE TO THE MULTI-MODEL CONSENSUS AND PREVIOUS FORECASTS WHILE THE INTENSITY FORECAST STAYS BELOW THE CONSENSUS AND CLOSER TO THE COAMPS-TC HWRF AND GFS VALUES. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN