MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 05W (PEIPAH) WARNING NR 21// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION (TD) 05W (PEIPAH), LOCATED APPROXIMATELY 759 NM SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED NORTHWESTWARD AT 04 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS AN OBSCURED, SLOWLY-CONSOLIDATING LOW-LEVEL CIRCULATION CENTER (LLCC) WITH THE BULK OF THE DEEP CONVECTION SHEARED WEST AND NORTHWEST OF THE LLCC. A 072312Z SSMIS IMAGE SHOWS WEAK, FRAGMENTED CONVECTIVE BANDING WRAPPING INTO A WEAKLY DEFINED LLCC. DESPITE THE WEAK CONVECTIVE STRUCTURE, A 080028Z ASCAT IMAGE DEPICTS A SYMMETRIC CIRCULATION WITH A WEAK CORE OF WINDS SURROUNDED BY NUMEROUS 25 TO 30 KNOT WIND BARBS, PRIMARILY OVER THE NORTHERN SEMI-CIRCLE. UPPER-LEVEL ANALYSIS REVEALS A MARGINAL ENVIRONMENT CHARACTERIZED BY MODERATE TO STRONG (20 TO 30 KNOTS) EASTERLY VERTICAL WIND SHEAR OFFSET BY STRONG DIFFLUENCE AND GOOD POLEWARD OUTFLOW. BASED ON THE ASCAT IMAGE, THERE IS FAIR CONFIDENCE IN THE INITIAL POSITION. THE INITIAL INTENSITY IS ASSESSED AT 30 KNOTS BASED ON DVORAK ESTIMATES OF 3O KNOTS FROM KNES, RJTD AND PGTW, AS WELL AS ASCAT DATA. TD 05W IS SITUATED WITHIN A WEAK STEERING ENVIRONMENT AND HAS TRACKED ERRATICALLY AND SLOWLY OVER THE PAST 12 HOURS. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TD 05W IS FORECAST TO REMAIN IN THE WEAK STEERING ENVIRONMENT THROUGH TAU 48 BUT IS FORECAST TO TRACK SLOWLY NORTHWESTWARD TOWARD THE WEAKNESS IN THE SUBTROPICAL RIDGE (STR). DYNAMIC GUIDANCE IS IN FAIR AGREEMENT WITH SOLUTIONS INDICATING NORTHWESTWARD TO NORTHWARD TRACKS. THE JTWC FORECAST TRACK IS POSITIONED CLOSE TO THE MULTI- MODEL CONSENSUS. TD 05W SHOULD MAINTAIN INTENSITY THROUGH TAU 36 WITH A GRADUAL INCREASE TO 40 KNOTS BY TAU 72 AS THE TRACK SPEEDS INCREASE AND AS THE SYSTEM TRACKS INTO LOWER VERTICAL WIND SHEAR WITH ROBUST POLEWARD OUTFLOW. C. IN THE EXTENDED TAUS, TD 05W IS EXPECTED TO TURN WEST- NORTHWESTWARD AND TO ACCELERATE AS THE STR RE-BUILDS NORTH OF THE SYSTEM. 05W SHOULD WEAKEN GRADUALLY PRIOR TO TRACKING OVER THE PHILIPPINES. DUE TO THE UNCERTAINTY IN THE INITIAL POSITION AS WELL AS MAJOR TRACK AND TRACK SPEED DIFFERENCES BETWEEN THE DYNAMIC MODELS, THERE IS LOW CONFIDENCE IN THE JTWC TRACK FORECAST.// NNNN NNNN