MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 29W (TWENTYNINE) WARNING NR 01// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION 29W (TWENTYNINE), LOCATED APPROXIMATELY 449 NM SOUTHEAST OF ANDERSEN AFB, GUAM, HAS TRACKED WEST-NORTHWESTWARD AT 15 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN EXTREMELY BROAD LOW-LEVEL CIRCULATION (LLC) WITH ENHANCED CONVECTION THAT DISPLAYS MID-LEVEL TURNING THAT PULLS THE EYE NORTHWARD. THE INITIAL POSITION IS PLACED WITH LOW CONFIDENCE BASED ON EXTRAPOLATION FROM A 251134Z METOP-C ASCAT PASS THAT INDICATES THE LLC IS SOUTH OF THE AFOREMENTIONED CONVECTION. THE INITIAL INTENSITY IS BASED ON 20 KNOTS DEPICTED NORTH OF THE LLC ON THE 251134Z METOP-C ASCAT PASS. HOWEVER, FURTHER TO THE NORTH OF THE CIRCULATION ARE 35 KNOT WINDS ASSOCIATED WITH GRADIENT FLOW BETWEEN TD 29W AND THE SUBTROPICAL RIDGE (STR) TO THE NORTHEAST. ENVIRONMENTAL ANALYSIS REVEALS A FAVORABLE ENVIRONMENT FOR DEVELOPMENT WITH LOW VERTICAL WIND SHEAR (VWS), ROBUST UPPER- LEVEL OUTFLOW, AND HIGH SEA SURFACE TEMPERATURES. 3. FORECAST REASONING. A. THIS IS THE FIRST PROGNOSTIC REASONING MESSAGE ON THIS SYSTEM AND SETS THE FORECAST PHILOSOPHY. B. TD 29W IS FORECAST TO TRACK WEST-NORTHWESTWARD ALONG THE SOUTHERN PERIPHERY OF A STR POSITIONED TO THE NORTH-NORTHEAST THROUGH TAU 48. BETWEEN TAUS 48 AND 72 AN UPPER-LEVEL TROUGH TO THE NORTH WILL TRACK EASTWARD PROVIDING A BREAK BETWEEN THE PREVIOUSLY MENTIONED STR AND A SECOND TO THE WEST OVER THE SOUTH CHINA SEA. THIS BREAK IN THE RIDGES WILL ALLOW THE SYSTEM TO TURN MORE POLEWARD INTO THE CULL AFTER TAU 48. TD 29W IS EXPECTED TO GRADUALLY INTENSIFY THROUGH TAU 36 REACHING 45 KNOTS AT TAU 36. AS THE SYSTEM BEGINS TO ROUND THE STR ENHANCED POLEWARD OUTFLOW WILL LEAD TO MORE RAPID INTENSIFICATION, REACHING 80 KNOTS BY TAU 72. THERE IS GOOD AGREEMENT AMONG THE MODELS THROUGH TAU 36, COMBINED WITH THE LOW CONFIDENCE IN THE INITIAL POSITION OF THE LLCC THERE IS FAIR CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK. AFTER TAU 48, THE MODELS DIVERGE IN THE TIMING FOR THE SYSTEM RECURVING, THEREFORE CONFIDENCE IN THE JTWC TRACK AFTER TAU 48 DECREASES. C. AFTER TAU 72, THERE IS PERSISTENT LOW CONFIDENCE IN THE EXACT FORECAST TRACK AS THE TIMING OF THE TROUGH WILL SIGNIFICANTLY AFFECT THE TRACK. TD 29W IS EXPECTED TO SLOW DOWN AS IT SITS IN THE CULL BETWEEN THE TWO STRS AND HAS MINIMAL STRONG STEERING INFLUENCES IN THE LATTER PORTION OF THE FORECAST.// NNNN NNNN