MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W (MAYSAK) WARNING NR 02// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION (TD) 10W (MAYSAK), LOCATED APPROXIMATELY 610 NM SOUTH OF KADENA AB, HAS TRACKED WEST-SOUTHWESTWARD AT 08 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A DEVELOPING LOW LEVEL CIRCULATION CENTER (LLCC) PARTIALLY OBSCURED BY DEEP CONVECTION OVER THE WESTERN SEMICIRCLE, AND FLARING CONVECTION OVER THE EASTERN SEMICIRCLE. THE INITIAL POSITION IS PLACED WITH FAIR CONFIDENCE BASED ON THE PARTIALLY OBSCURED LLCC IN THE MSI LOOP AND THE LOW LEVEL FEATURES PRESENT IN THE MICROWAVE IMAGERY FROM A 280513Z ATMS PASS. THE INITIAL INTENSITY OF 30 KTS IS PLACED WITH HIGH CONFIDENCE BASED ON MULTIAGENCY DVORAK CURRENT INTENSITY ESTIMATES OF T2.0 (30 KTS, PGTW AND RJTD) AND THE 30 KTS WINDS DEPICTED IN BOTH A 280033Z ASCAT-B AND 280125Z ASCAT-C PASS THAT ARE POSITIONED TO THE SOUTHWEST OF THE LOW LEVEL CIRCULATION FEATURE. THE WINDFIELD IN THE SCATTEROMETRY DATA ALSO CONSTRAINS THE INITIAL POSITION, HOWEVER THE LOW LEVEL CIRCULATION IN THE DATA REMAINS ELONGATED ALONG THE WEST TO EAST AXIS. ENVIRONMENTAL CONDITIONS ARE CONDUCIVE FOR FURTHER DEVELOPMENT WITH DIVERGENT EQUATORWARD OUTFLOW AND VERY WARM (30-31 CELSIUS) SEA SURFACE TEMPERATURES (SST) OFFSET SLIGHTLY BY MODERATE (15-20 KTS) VERTICAL WIND SHEAR (VWS) AND CONVERGENT FLOW ALOFT TO THE NORTH OF THE SYSTEM STEMMING FROM AN INCOMING TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) CELL TO THE EAST. OCEAN HEAT CONTENT IS VERY HIGH (GREATER THAN 125 JOULES PER SQUARE CENTIMETER). THE SYSTEM IS TRACKING SLOWLY IN A WEAK STEERING ENVIRONMENT INDUCED BY AN EXTENSION OF A NEAR EQUATORIAL RIDGE POSITIONED TO THE SOUTH AND EAST OF THE SYSTEM CENTER THAT EXTENDS FROM THE PHILIPPINES EASTWARD ALONG 10 DEGREES NORTH LATITUDE, A STRONG SUBTROPICAL RIDGE (STR) TO THE NORTH AND A DEEP-LAYER SUBTROPICAL LOW CENTERED NEAR THE NORTHERN MARIANAS. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TD 10W WILL CONTINUE ITS SLOW, GENERALLY WESTWARD TRACK UNDER THE INFLUENCE OF THE CURRENT WEAK STEERING PATTERN THROUGH TAU 12. STEADY INTENSIFICATION TO 50 KTS WILL TAKE PLACE DURING THIS TIME AS THE SYSTEM TRACKS OVER VERY WARM WATERS AND THROUGH CONTINUED MODERATE VWS AND CONVERGENT FLOW ALOFT TO THE NORTH FROM THE AFOREMENTIONED TUTT CELL. DECREASING VWS FROM TAU 12 TO TAU 24, COUPLED WITH THE WARM SST AND AND CONTINUED DIVERGENT EQUATORWARD OUTFLOW, WILL ALLOW FOR FURTHER INTENSIFICATION TO 50 KTS BY TAU 24. AFTER THIS TIME, THE CONVERGENT FLOW FROM THE TUTT CELL WILL BECOME DIVERGENT AS THE THE CELL PROPAGATES WESTWARD. BETWEEN TAU 24 AND TAU 36, A REORIENTATION OF THE STEERING RIDGES WILL ALSO TAKE PLACE WITH THE NER MOVING NORTHWARD AND REORIENTING INTO A NORTH-SOUTH ORIENTATED RIDGE AXIS ALONG ROUGHLY THE 140 EAST LONGITUDE LINE, RESULTING IN A GENERALLY NORTHWARD TRACK BETWEEN THESE TIMES. AT TAU 36 THE ENHANCED OUTFLOW FROM THE TUTT CELL, ALONG WITH THE CONTINUED HIGH OCEAN HEAT CONTENT, VERY WARM SSTS AND LOW (5-10 KTS) VWS WILL ALLOW THE SYSTEM TO INTENSIFY, POSSIBLY RAPIDLY, FROM TAU 36 TO TAU 48 AT WHICH TIME THE SYSTEM WILL REACH AN INTENSITY OF 80 KTS. AFTER THIS TIME, THE SYSTEM WILL BEGIN TO TRACK ALONG THE PERIPHERY OF THE SUBTROPICAL RIDGE TO THE EAST, RESULTING IN A NORTH-NORTHWESTWARD TRACK. THE ENVIRONMENT IS EXPECTED TO REMAIN VERY FAVORABLE FOR FURTHER INTENSIFICATION AND WILL RESULT IN FURTHER INTENSIFICATION TO 100 KTS BY TAU 72. NUMERICAL MODEL SOLUTIONS ARE IN POOR AGREEMENT ON THE TIMING OF THE STEERING RIDGE REPOSITIONING, WHICH LEADS TO A 255 NM CROSS TRACK SPREAD IN SOLUTIONS BY TAU 72. THIS LARGE SPREAD IN SOLUTIONS LENDS OVERALL FAIR CONFIDENCE IN THE INITIAL PORTION OF THE JTWC FORECAST TRACK. C. IN THE EXTENDED PERIOD, THE AFOREMENTIONED RIDGE COMPLEX TO THE EAST WILL REORIENT ONCE AGAIN, DEEPENING AFTER TAU 72, AND BECOME THE PRIMARY STEERING MECHANISM OF THE STORM. THIS WILL LEAD TO A GENERALLY NORTHWESTWARD TRACK INITIALLY, AND THEN TO A NORTHWARD TRACK AS TD 10W APPROACHES THE SUBTROPICAL RIDGE AXIS. TD 10W IS FORECAST TO REACH PEAK INTENSITY OF 110 KNOTS AT TAU 96 UNDER VERY FAVORABLE CONDITIONS OF LOW VWS, ROBUST, DIVERGENT POLEWARD OUTFLOW AND VERY WARM SSTS. AS THE SYSTEM ENTERS THE EAST CHINA SEA, IT IS FORECAST TO WEAKEN SLIGHTLY, AS COOLER SSTS IN THE WAKE OF THE PASSAGE OF TY 09W THROUGH THE AREA AND INCREASING VWS, WILL OFFSET STRONG POLEWARD OUTFLOW INTO THE BASE OF AN APPROACHING MID-LATITUDE TROUGH. THIS SLIGHT WEAKENING WILL BRING THE INTENSITY DOWN TO 100 KTS BY TAU 120. NUMERICAL MODEL SOLUTIONS MAINTAIN A NEARLY 255 NM CROSS TRACK SPREAD THROUGH THE REMAINDER OF THE FORECAST. ALONG TRACK CROSS SPREAD HAS IMPROVED SINCE THE LAST SET OF NUMERICAL MODEL CALCULATIONS, WITH AN AVERAGE 120 NM SPREAD BETWEEN TAU 72 AND TAU 120. THE JTWC FORECAST TRACK LIES WEST OF THE MULTI-MODEL CONSENSUS THROUGH TAU 72, FAVORING THE ECMWF SOLUTION, THEN LIES VERY CLOSE TO THE CONSENSUS, ALBEIT WITH A FASTER TRACK, THROUGH TAU 120. DUE TO THE SPREAD IN MODEL SOLUTIONS AND UNCERTAINTY IN THE TIMING OF STEERING RIDGE REPOSITIONING, THE OVERALL JTWC FORECAST TRACK IS PLACED WITH OVERALL FAIR CONFIDENCE.// NNNN NNNN