MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 30W (THIRTY) WARNING NR 01// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION 30W (THIRTY), LOCATED APPROXIMATELY 226 NM EAST-SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WEST- NORTHWESTWARD AT 15 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A RAPIDLY CONSOLIDATING SYSTEM WITH BANDS OF DEEP CONVECTION WRAPPING INTO THE LOW LEVEL CIRCULATION CENTER. THERE IS HIGH CONFIDENCE IN THE INITIAL POSITION WHICH IS BASED ON A 082305Z 89GHZ AMSU-B IMAGE SHOWING A LOW REFLECTIVITY CIRCULATION FEATURE WITH A BURST OF STRONG CENTRAL CONVECTION. THE INITIAL INTENSITY IS ASSESSED AT 25 KNOTS AND IS BASED ON AGENCY DVORAK ESTIMATES RANGING FROM T1.5 TO 2.0 (25 TO 30 KNOTS). A SURFACE OBSERVATION FROM CATARMAN, PHILIPPINES IS REPORTING A STATION PRESSURE OF 1002 MB WHICH FURTHER SUPPORTS THE INITIAL INTENSITY ESTIMATE. UPPER-LEVEL ANALYSIS SHOWS VERY LOW VERTICAL WIND SHEAR AS AN ANTICYCLONE DEVELOPS OVER THE SYSTEM. POLEWARD OUTFLOW IS ROBUST AS IT TAPS INTO THE MIDLATITUDE WESTERLY JET, WHILE EQUATORWARD OUTFLOW EXHIBITING SUBSTANTIAL DIFFLUENCE. CURRENTLY TD 30W IS TRACKING WEST-NORTHWEST ALONG THE SOUTHERN BOUNDARY OF AN EAST-WEST ORIENTED SUBTROPICAL RIDGE (STR) LOCATED TO THE NORTH 3. FORECAST REASONING. A. THIS IS THE INITIAL PROGNOSTIC REASONING AND SETS THE FORECAST PHILOSOPHY. B. TD 30W WILL CONTINUE TRACKING WEST-NORTHWESTWARD OVER THE FORECAST PERIOD ALONG THE SOUTHERN BOUNDARY OF THE STR. OVER THE NEXT 12 TO 18 HOURS TD 30W WILL TRACK OVER THE PHILIPPINES. DESPITE THE FAVORABLE ENVIRONMENTAL CONDITIONS, LAND INTERACTION WITH THE ARCHIPELAGO WILL LIMIT THE POTENTIAL FOR INTENSIFICATION, AND TD 30W IS FORECAST TO REMAIN A TROPICAL DEPRESSION DURING THIS TIME. BETWEEN TAU 18 AND 24 THE SYSTEM WILL EMERGE OVER THE WARM WATERS OF THE SOUTH CHINA SEA. UPPER-LEVEL CONDITIONS ARE FORECAST TO REMAIN VERY FAVORABLE AND TD 30W WILL BEGIN A PERIOD OF RAPID INTENSIFICATION, REACHING A PEAK INTENSITY OF 70 KNOTS AROUND TAU 48. THE SYSTEM IS ALSO EXPECTED TO REMAIN FAIRLY COMPACT WITH THE 34- KNOT WIND RADII REMAINING CLOSE TO THE SYSTEM CENTER. C. IN THE EXTENDED PERIOD TD 30W WILL MOVE INTO AN AREA OF LOWER SSTS, THIS COMBINED WITH DETERIORATING UPPER-LEVEL CONDITIONS WILL RESULT IN A WEAKENING TREND BEGINNING JUST BEFORE TAU 72. AROUND TAU 96 THE STEERING RIDGE WILL HAVE WEAKENED SUFFICIENTLY TO CAUSE A TRACK SHIFT TO THE NORTH-NORTHWEST STEERING TD 30W OVER HAINAN AND CLOSER TO THE WESTERLY JET. LAND INTERACTION AND INCREASED WIND SHEAR WILL FURTHER WEAKEN THE SYSTEM. DYNAMIC MODEL GUIDANCE SHOWS VERY GOOD AGREEMENT IN THE MID-RANGE FORECAST DUE TO THE WELL- ESTABLISHED DEEP-LAYERED STEERING RIDGE. HOWEVER THERE ARE SLIGHT DIFFERENCES IN THE MODELS THAT ORIGINATE FROM THE INITIAL 12 HOURS AND IN THE UNCERTAINTY OF THE TRACK WHILE OVER THE PHILIPPINES. BY TAU 96 AND 120 MODELS ARE IN DISAGREEMENT WITH THE EXACT POSITION AND TIMING OF THE TURN TO THE NORTH-NORTHWEST. DUE TO THESE UNCERTAINTIES THERE IS OVERALL LOW CONFIDENCE IN THE FORECAST TRACK.// NNNN NNNN