WDPN32 PGTW 180300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 12W (TWELVE) WARNING NR 05// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION 12W (TWELVE), LOCATED APPROXIMATELY 373 NM SOUTHWARD OF KADENA AB, HAS TRACKED EASTWARD AT 08 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) ON THE EASTERN EDGE OF IMPROVING DEEP CONVECTION AS WELL AS A LARGE CONVECTIVE BANDING FEATURE ALONG THE SOUTHERN PERIPHERY. A 172327Z SSMIS MICROWAVE IMAGE CLEARLY REVEALS THE LLCC JUST SLIGHTLY TO THE EAST OF THE DEEP CONVECTION AND AGAIN SHOWS THE STRONG BANDING FEATURE TO THE SOUTH. THE INITIAL POSITION IS BASED ON THE MSI LOOP AND THE AFOREMENTIONED MICROWAVE IMAGE WITH GOOD CONFIDENCE. THE INITIAL INTENSITY HAS BEEN ASSESSED AT 30 KNOTS BASED ON A CONSENSUS OF DVORAK INTENSITY ESTIMATES FROM ALL AGENCIES. ADDITIONALLY, A 180044Z ASCAT METOP-B IMAGE CONFIRMS THE INITIAL INTENSITY WITH 25 TO 30 KNOT WIND BARBS SURROUNDING A CLEARLY DEFINED LLCC. UPPER- LEVEL ANALYSIS INDICATES THE SYSTEM IS JUST NORTH OF THE SUBTROPICAL RIDGE (STR) AXIS IN A MODERATELY FAVORABLE ENVIRONMENT AS AN UPPER- LEVEL LOW, NORTHWEST OF THE SYSTEM, HAS LIMITED THE OUTFLOW AND SLIGHTLY INCREASED VERTICAL WIND SHEAR TO MODERATE (10-20 KNOTS) LEVELS. TD 12W IS CURRENTLY TRACKING ALONG THE LOW TO MID-LEVEL STEERING RIDGE SOUTH OF THE SYSTEM. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING. B. TD 12W IS EXPECTED TO TRACK EAST ALONG THE SOUTHERN PERIPHERY OF THE STEERING RIDGE THROUGH THE NEXT 24 HOURS. AFTER TAU 24, THE STEERING INFLUENCES WILL WEAKEN AS THE SYSTEM WILL BE POSITIONED BETWEEN TWO STEERING RIDGES, THE CURRENT STEERING RIDGE TO THE SOUTH AND A RIDGE BUILDING JUST NORTH OF THE SYSTEM. AFTER TAU 48, THE RIDGE TO THE NORTH IS EXPECTED TO BECOME THE DOMINANT STEERING INFLUENCE AND SHOULD ACCELERATE THE SYSTEM WESTWARD. TD 12W IS FORECAST TO INTENSIFY AS THE UPPER-LEVEL LOW IS EXPECTED TO FILL AND CREATE A MORE FAVORABLE ENVIRONMENT OF GOOD OUTFLOW AND LOW VWS THROUGH THIS PORTION OF THE FORECAST PERIOD. TD 12W IS EXPECTED TO REACH A PEAK INTENSITY OF 60 KNOTS BY TAU 72. C. IN THE EXTENDED PERIOD, TD 12W IS EXPECTED TO CONTINUE TO TRACK WEST-NORTHWEST ALONG THE STEERING RIDGE TO THE NORTH AND THEN BEGIN TO WEAKEN, DUE TO LAND INTERACTION, AS IT ENCOUNTERS THE NORTHERN COAST OF TAIWAN AND THE EAST COAST OF CHINA THEREAFTER. ALTHOUGH DYNAMIC MODEL GUIDANCE HAS COME INTO AGREEMENT WITH THE CYCLONIC TURN BACK TO THE WEST, THERE IS A LARGE UNCERTAINTY IN THE EXTENT AND SPEED OF THE TURN. DUE TO THIS LARGE SPREAD OF SOLUTIONS, THE FORECAST IS POSITIONED CLOSE TO MULTI-MODEL CONSENSUS WITH LOW CONFIDENCE.// NNNN