MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 15W (FIFTEEN) WARNING NR 01// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION (TD) 15W (FIFTEEN), LOCATED APPROXIMATELY 422 NM EAST-SOUTHEAST OF IWO TO, HAS TRACKED NORTHWESTWARD AT 12 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A WELL DEFINED AND PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH FLARING CONVECTION OFFSET JUST EAST OF THE CENTER. A TUTT CELL LOCATED IMMEDIATELY NORTHWEST OF THE LLCC IS CREATING INCREASED SUBSIDENCE ALONG THE WESTERN PERIPHERY AS EVIDENT ON WATER VAPOR IMAGERY. A 062328Z ASCAT BULLSEYE SHOWS 20 TO 25 KNOT WINDS ALONG THE EASTERN PERIPHERY CLOSE TO THE LLCC WITH STRONGER 30 KNOT WINDS WITHIN THE CONVECTION. THE CURRENT POSITION IS BASED ON THE LLCC SEEN IN MSI AND THE ASCAT PASS. THE INITIAL INTENSITY IS BASED ON DVORAK INTENSITY ESTIMATES OF T1.5 (25 KNOTS) FROM ALL AGENCIES AND SUPPORTED BY THE ASCAT PASS. THE CURRENT ENVIRONMENT IS MARGINAL DUE TO THE AFOREMENTIONED TUTT CELL CREATING SUBSIDENCE AND MODERATE (15-20 KNOT) VERTICAL WIND SHEAR (VWS), WHICH IS PREVENTING QUICKER CONSOLIDATION. STRONG EQUATORWARD OUTFLOW AND SEA SURFACE TEMPERATURES NEAR 30 CELSIUS ARE CONDUCIVE FOR FURTHER DEVELOPMENT. TD 15W IS TRACKING ALONG THE WESTERN PERIPHERY OF A LOW TO MID-LEVEL SUB-TROPICAL RIDGE TO THE EAST. 3. FORECAST REASONING. A. THIS IS THE INITIAL PROGNOSTIC REASONING AND SETS THE FORECAST PHILOSOPHY. B. TD 15W WILL CONTINUE TRACKING NORTHWESTWARD UNDER THE INFLUENCE OF THE STEERING STR THROUGH TAU 72. ENVIRONMENTAL CONDITIONS WILL REMAIN MARGINAL AS THE TUTT CELL REMAINS JUST WEST TO NORTHWEST OF THE SYSTEM THROUGH TAU 48. BEYOND TAU 48, VWS WILL DECREASE AND POLEWARD OUTFLOW WILL INCREASE, SUPPORTING INTENSIFICATION. BY TAU 72, TD 15W WILL REACH THE WESTERN EXTENT OF THE STR AND BEGIN TO TURN POLEWARD. INITIAL DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 48 AND THEN BEGIN TO DIVERGE DUE TO THE TIMING OF THE RE-CURVE. C. IN THE EXTENDED TAUS, TD 15W WILL BEGIN TO ACCELERATE TO THE NORTHEAST AHEAD OF AN APPROACHING MID-LATITUDE SHORTWAVE TROUGH. INITIALLY THIS TROUGH WILL PROVIDE AN INCREASED POLEWARD OUTFLOW CHANNEL ALLOWING TD 15W TO REACH A PEAK INTENSITY OF 70 KNOTS AT TAU 96. AFTERWARDS, THE TROUGH WILL CAUSE INCREASED VWS AS THE SYSTEM INTERACTS WITH THE MID-LATITUDE WESTERLY FLOW. DYNAMIC MODEL GUIDANCE CONTINUES TO DIVERGE IN THE EXTENDED TAUS DUE TO THEIR DEPICTION OF THE STEERING STR. DUE TO THIS MODEL SPREAD, THERE IS LOW CONFIDENCE IN THE INITIAL JTWC FORECAST.// NNNN NNNN