MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W (SIX) WARNING NR 012// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION (TD) 06W (SIX), LOCATED APPROXIMATELY 411 NM EAST OF KADENA AB, OKINAWA, HAS TRACKED WEST-SOUTHWESTWARD AT 11 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS EXPOSED LOW-LEVEL CLOUD LINES WRAPPING INTO A BROAD, RAGGED CENTER. A 120646Z SSMIS 91GHZ MICROWAVE IMAGE SHOWS ISOLATED CONVECTIVE BURSTS OVER THE WEST AND SOUTHWEST QUADRANTS BUT OVERALL WEAK CONVECTIVE STRUCTURE. RECENT ASCAT IMAGERY AND THE SSMIS WIND PRODUCT INDICATE A HIGHLY ASYMMETRIC WIND FIELD WITH A PATCH OF 20- 25 KNOT WINDS OVER THE NORTHWEST QUADRANT AND A BROADENING CENTER REFLECTING A GRADUAL WEAKENING TREND. HOWEVER, THE INITIAL INTENSITY IS HELD AT 25 KNOTS BASED ON THE ASCAT DATA AND DVORAK CURRENT INTENSITY ESTIMATES OF 1.0-1.5 (25 KNOTS). THE SYSTEM REMAINS EMBEDDED WITHIN AN EXPANSIVE REGION OF ENHANCED EASTERLIES BETWEEN THE UPPER-LEVEL RIDGE AND A TUTT CELL TO THE SOUTHEAST WITH LOW TO MODERATE (15 TO 20 KNOTS) VERTICAL WIND SHEAR, DRY AIR ENTRAINMENT AND WEAK DIFFLUENCE. TD 06W IS TRACKING WEST-SOUTHWESTWARD UNDER THE STEERING INFLUENCE OF A LOW-LEVEL SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTH AND NORTHWEST. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. DUE TO THE WSW-ENE ORIENTATION OF THE LOW-LEVEL STR, TD 06W IS FORECAST TO CONTINUE TRACKING WEST-SOUTHWESTWARD THROUGH TAU 24. AS IT APPROACHES THE RYUKYU ISLANDS, THE SYSTEM SHOULD TURN WESTWARD TO WEST-NORTHWESTWARD AS IT TRACKS ALONG THE SOUTHWEST PERIPHERY OF THE STR. ENVIRONMENTAL CONDITIONS ARE EXPECTED TO REMAIN MARGINAL WITH LOW TO MODERATE VWS AND DRY AIR ENTRAINMENT (700-500MB RH VALUES OF 50-55%), THEREFORE, THE SYSTEM SHOULD REMAIN SHALLOW AND WEAK WITH SOME POTENTIAL FOR DISSIPATION DURING THE FORECAST PERIOD. NUMERICAL MODEL GUIDANCE SUPPORTS THE JTWC FORECAST TRACK AND REMAINS IN FAIR AGREEMENT WITH MINOR VARIATIONS IN TRACK ORIENTATION THROUGH TAU 48. MODEL SPREAD AT TAU 36 TO 48 RANGES FROM 50 TO 110NM, THEREFORE, THE JTWC FORECAST TRACK IS POSITIONED CLOSE TO THE MULTI-MODEL CONSENSUS WITH MODERATE CONFIDENCE.// NNNN NNNN