WDPN31 PGTW 180300 MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W WARNING NR 06// RMKS/ 1. FOR METEOROLOGISTS. 2. 12 HOUR SUMMARY AND ANALYSIS. A. TROPICAL DEPRESSION (TD) 06W (SIX), LOCATED APPROXIMATELY 305 NM EAST-SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED NORTHWESTWARD AT 11 KNOTS OVER THE PAST SIX HOURS. THE CURRENT POSITION IS BASED ON RECENT MICROWAVE SATELLITE IMAGERY, INCLUDING A 172033Z TRMM PASS, WHICH SHOWS A NEARLY FULLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH DEEP CONVECTION CONFINED TO THE WESTERN PERIPHERY. THE CURRENT INTENSITY ESTIMATE OF 30 KNOTS IS CONSISTENT WITH RECENT DVORAK T-NUMBER ESTIMATES FROM PGTW AND KNES OF 2.0 AND 2.5 RESPECTIVELY. TD 06W CONTINUES TO TRACK NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF A SUBTROPICAL STEERING RIDGE TO THE NORTHEAST. 3. FORECAST REASONING. A. THERE ARE NO SIGNIFICANT CHANGES TO THE PREVIOUS FORECAST PHILOSOPHY. B. GENERALLY NORTHWESTWARD MOTION IS EXPECTED TO CONTINUE FOR THE NEXT 48 HOURS ALONG THE SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL STEERING RIDGE. TD 06W SHOULD CONTINUE A SLOW BUT STEADY INTENSIFICATION TREND DRIVEN BY PASSAGE OVER VERY WARM WATER, FAVORABLE WESTWARD OUTFLOW ALOFT, AND DECREASING VERTICAL WIND SHEAR. A TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) TO THE EAST APPEARS TO BE CONNECTING WITH THE SYSTEM AND MAY ENHANCE POLEWARD OUTFLOW IN THE DAYS AHEAD. ADDITIONALLY, A MIGRATORY UPPER LEVEL, MID-LATITUDE TROUGH APPROACHING FROM THE WEST MAY BRIEFLY ENHANCE POLEWARD OUTFLOW AROUND TAU 36 THROUGH TAU 48. C. IN THE EXTENDED RANGE, LOWER OCEAN HEAT CONTENT, RESTRICTED OUTFLOW ALOFT, INCREASING VERTICAL WIND SHEAR FROM THE EAST, AND PASSAGE OVER LAND ARE EXPECTED TO WEAKEN THE CYCLONE. THE NUMERICAL MODELS ARE IN FAIR AGREEMENT WITH THE CURRENT TRACK FORECAST. THE LATEST ECMWF RUN REMAINS THE WESTERN OUTLIER, KEEPING TD 06W WEAK THROUGHOUT ITS LIFECYCLE AND STEERING THE SYSTEM WESTWARD WITH LOWER LEVEL FLOW AS A RESULT. THIS FORECAST FAVORS THE MAIN MODEL GROUPING CLUSTERED AROUND THE CONSENSUS, WHICH IS MORE CONSISTENT WITH THE CURRENT SYNOPTIC REASONING AND INTENSITY FORECAST. // NNNN