WDPN31 PGTW 082100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 02W (MALAKAS) WARNING NR 008// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 6.5N 144.6E INITIAL INTENSITY: 40 KTS GEOGRAPHIC REFERENCE: 49 NM SOUTH-SOUTHEAST OF IFALIK MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 11 KTS SIGNIFICANT WAVE HEIGHT: 18 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A CYCLONE BEING SHEARED FROM THE SOUTHEAST, WITH A RAGGED MASS OF DEEP CONVECTION DISPLACED LARGELY NORTHWEST OF THE LOW-LEVEL CIRCULATION CENTER (LLCC). A 081214Z ASCAT-B PASS REVEALED AN ELONGATED CIRCULATION NEAR OR JUST EAST OF THE EASTERN EDGE OF THE DEEP CONVECTION, WITH A WESTWARD EXTENSION TOWARD THE CONVECTION. SINCE THAT TIME, EIR IMAGERY AND A 081847Z SSMIS MICROWAVE PASS HAVE REVEALED THE CONVECTIVE AREA TO BE DOMINATED BY A SINGLE, PERSISTENT UPDRAFT TO THE WEST OF THE LLCC, CHARACTERISTIC OF SOME SHEARED TROPICAL CYCLONES. WITH NO APPARENT WRAPPING OF THE CONVECTION AROUND THE LLCC, THIS STRUCTURE SUGGESTS THAT THE CYCLONE IS NEAR STEADY-STATE. THE INITIAL INTENSITY REMAINS 40 KT BASED ON A COMBINATION OF ASCAT DATA AND SUBJECTIVE DVORAK INTENSITY ESTIMATES RANGING FROM T2.5 (35 KTS) TO T3.0 (45 KTS). THIS IS ALSO CONSISTENT WITH A 081623Z AMSR-2 WIND SPEED ESTIMATE OF 39 KT. INITIAL WIND RADII BASIS: COMBINATION OF SCATTEROMETER DATA AND PERSISTENCE CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE NORTHEAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS RJTD: T2.5 - 35 KTS RCTP: T3.0 - 45 KTS CIMSS SATCON: 47 KTS AT 081541Z CIMSS ADT: 43 KTS AT 081740Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 20-25 KTS SST: 28-29 CELSIUS OUTFLOW: MODERATE WESTWARD ANALYSIS CONFIDENCE: INITIAL POSITION: LOW INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THE ALTERNATE SCENARIO FOR A SIGNIFICANTLY MORE WESTWARD TRACK DESCRIBED IN PREVIOUS WARNINGS IS NO LONGER CONSIDERED A DISTINCT POSSIBILITY FORECAST DISCUSSION: TROPICAL STORM 02W (MALAKAS) IS CURRENTLY EMBATTLED BY UPPER-LEVEL SOUTHEASTERLY FLOW THAT MAXIMIZES AT 25 KT AROUND 300 MB, JUST BELOW THE OUTFLOW LAYER, AS ANALYZED BY THE GFS AND ECMWF MODELS. THE RESULTING CONVECTIVE STRUCTURE LACKS ANY SIGNS OF PROGRESS TOWARD AXISYMMETRY, IMPLYING THAT MALAKAS MAY STRUGGLE TO MAKE SIGNIFICANT GAINS IN INTENSITY DURING THE NEAR TERM. HOWEVER, THE 300 MB ENVIRONMENTAL FLOW IS FORECAST TO DECREASE TO 20 KT BY 24 HOURS, AND 15 KT BY 36 HOURS, LEADING TO A DECREASE IN VERTICAL SHEAR THAT SHOULD ALLOW CONVECTION TO WRAP FURTHER AROUND THE CIRCULATION CENTER AND FACILITATE INTENSIFICATION. MALAKAS IS FORECAST TO REACH TYPHOON INTENSITY AFTER 48 HOURS AND CONTINUE INTENSIFYING TO A PEAK OF 95 KT IN 96 HOURS IN AN ENVIRONMENT OF WEAK VERTICAL SHEAR AND WARM SEA SURFACE TEMPERATURES. BEYOND 96 HOURS, THE CYCLONE WILL APPROACH COOLER WATERS AROUND LATITUDE 19N AND POTENTIALLY BEGIN ENTRAINING AN AMBIENT DRY SUBTROPICAL AIR MASS, WHICH SHOULD ARREST THE INTENSIFICATION. THE TRACK FORECAST IS MORE STRAIGHT-FORWARD THAN IN PREVIOUS WARNINGS, WITH MODEL GUIDANCE IN TIGHT AGREEMENT THROUGH 48 HOURS, TAKING MALAKAS NORTHWESTWARD WELL SOUTHWEST OF GUAM, STEERED BY THE DEEP-LAYER SUBTROPICAL RIDGE EAST OF THE MARIANAS. A TURN NORTHWARD AROUND THE WESTERN PERIPHERY OF THIS RIDGE IS EXPECTED AROUND 72 HOURS, AT WHICH POINT MODEL SPREAD INCREASES. STEERING CURRENTS MAY WEAKEN AS THE MID-LATITUDE JET REMAINS WELL NORTH OF THE CYCLONE AND A SHORTWAVE TROUGH CROSSES KYUSHU AND BEGINS ERODING THE STEERING RIDGE. ADDITIONALLY, THE POTENTIAL DEVELOPMENT OF INVEST 94W TO THE SOUTHWEST OF MALAKAS COULD INDUCE A TEMPORARY WESTWARD JOG IN THE TRACK OF MALAKAS DURING THE 72-96 HOUR PERIOD, DEPENDING ON HOW STRONG 94W BECOMES AND THE EXACT PROXIMITY OF THE TWO CIRCULATIONS. SUCH A JOG, IF ANY, IS EXPECTED TO BE SMALL GIVEN THE MUCH LARGER SIZE OF 02W (MALAKAS). GIVEN THESE FACTORS, CONFIDENCE IN THE TRACK FORECAST AFTER 72 HOURS IS MEDIUM. MODEL DISCUSSION: THE JTWC TRACK FORECAST IS CLOSE TO THE MULTI-MODEL CONSENSUS THROUGH 48 HOURS AND SLIGHTLY WEST OF THE PREVIOUS FORECAST, THEN SLIGHTLY RIGHT OF CONSENSUS BEYOND 48 HOURS, CLOSE TO THE MEAN OF ECMWF AND GFS, BUT A LITTLE SLOWER, CLOSE TO THE PREVIOUS FORECAST. THE JTWC INTENSITY FORECAST IS SLIGHTLY BELOW THE MULTI-MODEL CONSENSUS THROUGH 48 HOURS DUE TO EXPECTED IMPEDIMENTS TO INTENSIFICATION. THE AGGRESSIVE HWRF SOLUTION CALLS FOR TYPHOON INTENSITY IN 18 HOURS DUE TO A FORECAST FOR RAPIDLY IMPROVING CONVECTIVE STRUCTURE, A FORECAST THAT IS NOT VERIFYING AT PRESENT, AND IS CONSIDERED UNLIKELY. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN