WDPN31 PGTW 100300 MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 21W (NEPARTAK)// WARNING NR 07// RMKS/ 1. FOR METEOROLOGISTS. 2. 12 HOUR SUMMARY AND ANALYSIS. A. TROPICAL DEPRESSION NEPARTAK HAS MAINTAINED ITS INTENSITY AND REMAINS A POORLY ORGANIZED SYSTEM. ANIMATED INFRARED IMAGERY SHOWS THE SYSTEM HAS LIMITED CONVECTION EMBEDDED IN FRAGMENTED BANDS LOOSELY WRAPPING INTO AN ILL-DEFINED LOW LEVEL CIRCULATION CENTER. UPPER LEVEL ANALYSIS INDICATES THE SYSTEM IS SLOWLY TRACKING ALONG THE WESTERN EDGE OF A LOW- TO MID-LEVEL SUBTROPICAL RIDGE TO THE EAST IN A REGION OF MODERATE VERTICAL WIND SHEAR. THE CURRENT INTENSITY IS BASED ON DVORAK FIXES FROM PGTW, RJTD AND KNES. THE CURRENT POSITION IS BASED FROM ANIMATED MULTISPECTRAL IMAGERY AND FROM A 092206Z SSMIS 37H MICROWAVE PASS. 3. FORECAST REASONING A. THE TRACK FORECAST PHILOSOPHY HAS CHANGED SINCE THE PREVIOUS BULLETIN TO REFLECT A MUCH SLOWER POLEWARD PROGRESSION. B. TD 21W IS EXPECTED TO CONTINUE SLOWLY TRACKING NORTH AND INTENSIFY TO A MINIMAL TROPICAL STORM AS IT APPROACHES THE JETSTREAM TO THE NORTH THAT WILL MOMENTARILY PROVIDE POLEWARD OUTFLOW. HOWEVER, THE STRONGER VWS WILL ULTIMATELY ERODE THE SYSTEM AND CAUSE IT TO DISSIPATE BY TAU 72. THE AVAILABLE NUMERIC GUIDANCE ARE SPREAD OUT WITH NOGAPS, GFS AND WBAR ACCELERATING THE SYSTEM TO THE NORTHEAST AND JGSM GOING THE EXACT OPPOSITE. THIS TRACK IS SIMILAR TO THE EGRR AND ECMWF SOLUTIONS.// NNNN