MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 31W (YUTU) WARNING NR 19// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUPER TYPHOON (STY) 31W (YUTU), LOCATED APPROXIMATELY 903 NM SOUTHEAST OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED WEST- NORTHWESTWARD AT 11 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A CONSOLIDATING, SYMMETRIC EYEWALL SURROUNDING AN OBLONG EYE. ADDITIONALLY, A 260033Z AMSU 89GHZ IMAGE REVEALS A 40NM MICROWAVE EYE FEATURE, THEREFORE, THERE IS GOOD CONFIDENCE IN THE INITIAL POSITION. HOWEVER, RECENT ANIMATED SATELLITE IMAGERY CONTINUES TO INDICATE TROCHOIDAL TRACK MOTION. UPPER-LEVEL ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH LOW (10 TO 15 KNOTS) EASTERLY VERTICAL WIND SHEAR AND ROBUST OUTFLOW WITH THE EXCEPTION OF THE EASTERN QUADRANT. THE INITIAL INTENSITY IS HELD AT SUPER TYPHOON STRENGTH (130 KNOTS) BASED ON A PGTW DVORAK CURRENT INTENSITY ESTIMATE OF 127 KNOTS, CONSISTENT WITH A 252137Z SATCON ESTIMATE OF 128 KNOTS. STY 31W IS TRACKING WEST-NORTHWESTWARD ALONG THE SOUTHWEST PERIPHERY OF A DEEP SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST WITH A BREAK IN THE STR LOCATED SOUTH OF HONSHU (NORTH OF THE SYSTEM) ASSOCIATED WITH A BROAD, WEAK MIDLATITUDE SHORTWAVE TROUGH. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. STY 31W IS FORECAST TO CONTINUE TRACKING WEST-NORTHWESTWARD TOWARD THE BREAK IN THE STR THROUGH TAU 36, HOWEVER, THE SYSTEM SHOULD GRADUALLY TURN MORE WESTWARD AFTER TAU 36 AS THE AFOREMENTIONED SHORTWAVE TROUGH PROPAGATES EASTWARD AND A BROAD MIDLATITUDE RIDGE TO THE NORTH ALLOWS THE STR TO RE-BUILD. EXCLUDING THE PRIMARY OUTLIERS, COAMPS-TC (CTCX) AND NAVGEM, DYNAMIC MODEL GUIDANCE IS IN BETTER AGREEMENT THROUGH TAU 72 WITH A 170NM SPREAD IN SOLUTIONS AT TAU 72. STY 31W IS EXPECTED TO MAINTAIN NEAR-STY STRENGTH THROUGH TAU 12 AS THE EYEWALL RE-STRENGTHENS AND THE EYE CONTRACTS. HOWEVER, AFTER TAU 12, THE SYSTEM SHOULD GRADUALLY WEAKEN AS VERTICAL WIND SHEAR INCREASES TO MODERATE LEVELS. C. BEYOND TAU 72, THERE IS INCREASING UNCERTAINTY IN THE FORECAST TRACK WITH TWO DISTINCT CLUSTERS OF MODEL GUIDANCE. ECMWF, EEMN, UKMET, JGSM, AFUM, GFS, AEMN AND HWRF INDICATE A WEST-SOUTHWESTWARD (OVER LUZON) TO WEST-NORTHWESTWARD (TOWARD THE LUZON STRAIT) TRACK. NAVGEM AND COAMPS-TC (CTCX) CONTINUE TO INDICATE AN UNLIKELY RECURVE SCENARIO. BASED ON ANALYSIS OF MODEL FIELDS FROM BOTH CLUSTERS, THE RE-CURVE SCENARIO IS ASSESSED AS UNLIKELY DUE TO A LACK OF A DEEP MIDLATITUDE SHORTWAVE TROUGH AND THE PRESENCE OF A LOW-LEVEL RIDGE FORECAST TO BUILD OVER THE EAST CHINA SEA. THE JTWC FORECAST TRACK FAVORS A MORE WESTWARD TRACK WITH A DECREASE IN TRACK SPEEDS ASSOCIATED WITH A BREAK IN THE STR AND INCREASING NORTHEASTERLY LOW- LEVEL FLOW FORECAST TO DEVELOP EAST OF TAIWAN. BASED ON THE BIFURCATION IN THE DYNAMIC MODELS AND LARGE OVERALL SPREAD, THERE IS LOW CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK.// NNNN NNNN