MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 27W (TWENTYSEVEN) WARNING NR 07// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION 27W (TWENTYSEVEN), LOCATED APPROXIMATELY 253 NM EAST-SOUTHEAST OF ANDERSEN AFB, HAS TRACKED WEST-SOUTHWESTWARD AT 07 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A WELL-DEFINED FULLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH VERY LIMITED CENTRAL CONVECTION OVER THE LAST SIX HOURS. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE EXPOSED LLCC EVIDENT IN SATELLITE IMAGERY. THE INITIAL INTENSITY IS ASSESSED AT 30 KNOTS BASED LARGELY ON PERSISTENCE FROM PREVIOUS DVORAK ESTIMATES OF T2.0 (30KTS), A 202313Z OSCAT IMAGE SHOWING A SOLID REGION OF 30 KNOT WIND BARBS ON THE SOUTHWESTERN PERIPHERY, AND A 210548Z SATCON ESTIMATE OF 33 KNOTS. UPPER-LEVEL ANALYSIS SHOWS A TUTT CELL TO THE NORTH, WHICH PREVIOUSLY PROVIDED AN OUTFLOW MECHANISM, HAS DETERIORATED UNDER THE INFLUENCE OF A BUILDING RIDGE TO THE NORTHEAST. INCREASING EASTERLY FLOW FROM THE RIDGE HAS ALSO LED TO A RAPIDLY DETERIORATING SHEAR ENVIRONMENT. SSTS IN THE REGION ARE VERY WARM IN EXCESS OF 30 CELSIUS, BUT THE DETERIORATING UPPER-LEVELS HAVE THUS FAR HINDERED THE POSSIBILITY OF FURTHER DEVELOPMENT. TD 27W IS TRACKING SLOWLY WEST-SOUTHWESTWARD WITHIN A COMPETING STEERING ENVIRONMENT. 3. FORECAST REASONING. A. NO CHANGE IN THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TD 27W IS POSITIONED WITHIN A COMPETING STEERING ENVIRONMENT WITH MID-TO-LOW LEVEL RIDGES POSITIONED TO BOTH THE SOUTHWEST AND NORTHEAST. THE SYNOPTIC SETUP WILL RESULT IN A SLOW AND UNCERTAIN TRACK MOTION OVER THE NEXT 48 HOURS. THE WESTERN RIDGE IS FORECAST TO BUILD BECOMING SLIGHTLY MORE DOMINANT AND RESULTING IN A TRACK SOUTH TO SOUTHWEST OVER THE NEXT 36 HOURS. BEYOND TAU 36, THE WESTERN RIDGE IS EXPECTED TO WEAKEN RETREATING TO THE SOUTHWEST WHILE THE EASTERN RIDGE STRENGTHENS, ACCELERATING TD 27W ON A NORTHWESTWARD TRACK. INTENSE EASTERLY FLOW ALOFT WILL PERSIST WHILE TRAPPED BETWEEN THE TWO RIDGES MITIGATING THE LIKELIHOOD OF FURTHER DEVELOPMENT. C. IN THE EXTENDED PERIOD, THE EASTERN STEERING RIDGE IS FORECAST TO WEAKEN AND AROUND TAU 72 UPPER-LEVEL CONDITIONS WILL BECOME INCREASINGLY FAVORABLE. SHOULD THE LLCC SURVIVE THE HOSTILE SHEAR ENVIRONMENT, THE IMPROVING CONDITIONS ALOFT COUPLED WITH SSTS REMAINING FAVORABLY WARM, TD 27W IS FORECAST TO BEGIN GRADUALLY INTENSIFYING. AROUND TAU 96 THE STEERING RIDGE WILL WEAKEN SUFFICIENTLY TO BEGIN SLOWING DOWN TD 27W, WITH THE POSSIBILITY OF ENTERING A WEAK STEERING ENVIRONMENT AND SUBSTANTIAL UNCERTAINTY IN THE TRACK BEYOND TAU 120. DYNAMIC MODEL GUIDANCE SHOWS GENERAL AGREEMENT ON THE STEERING PHILOSOPHY, HOWEVER, THERE IS SUBSTANTIAL UNCERTAINTY IN EXACT POSITION AND TIMING OF THE TURN THE NORTHWEST. DUE TO THE LARGE DEGREE OF UNCERTAINTY IN THE OVER THE NEXT 48 HOURS WHILE IN A COMPETING STEERING ENVIRONMENT, THERE IS LOW CONFIDENCE IN THE JTWC FORECAST.// NNNN NNNN