MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (KROSA) WARNING NR 006// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 11W (KROSA), LOCATED APPROXIMATELY 253 NM SOUTH OF IWO TO, HAS TRACKED NORTH-NORTHWESTWARD AT 11 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS DEEP CONVECTIVE BANDING WRAPPING TIGHTLY AROUND THE LOW LEVEL CIRCULATION CENTER (LLCC). THE CONVECTIVE BANDING EXTENDS TO THE SOUTH AND WEST. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE AND IS BASED ON A 070039Z METOP-B ASCAT IMAGE WHICH CLEARLY SHOWS THE LLCC. THE INITIAL INTENSITY OF 55 KNOTS IS HEDGED SLIGHTLY ABOVE THE ASCAT PASS WHICH SHOWS 50 KNOTS AND BASED ON A DVORAK CURRENT INTENSITY (CI) ESTIMATE OF T3.5 (55 KNOTS) FROM PGTW. ENVIRONMENTAL ANALYSIS SHOW THAT TS 11W IS EXPERIENCING FAVORABLE VERTICAL WIND SHEAR (15 KNOTS). THE EQUATORWARD OUTFLOW CHANNEL REMAINS STRONG AND THE POLEWARD OUTFLOW CHANNEL REMAINS WEAK WHICH HAS INHIBITED FURTHER INTENSIFICATION. SEA SURFACE TEMPERATURES REMAIN FAVORABLE, GREATER THAN 31 DEGREES CELSIUS. TS 11W IS TRACKING NORTH- NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) LOCATED TO THE NORTHEAST. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE OVERALL FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 11W WILL TRACK NORTH-NORTHWESTWARD WHILE UNDER THE INFLUENCE OF THE AFOREMENTIONED STR THROUGH TAU 24. FAVORABLE SEA SURFACE TEMPERATURES AND FAVORABLE VERTICAL WIND SHEAR WILL ALLOW FOR A STEADY INCREASE IN INTENSITY, REACHING 80 KNOTS BY TAU 72. A LIMITED POLEWARD OUTFLOW CHANNEL WILL PREVENT FURTHER INTENSIFICATION IN THE SHORT TERM. BY TAU 24, AN APPROACHING WEST TO EAST MOVING SHORTWAVE TROUGH WILL CAUSE A TEMPORARY BREAK IN THE STR AND ALLOW TS 11W TO TRACK NORTHEASTWARD THROUGH TAU 72. THERE IS A WIDE SPREAD IN NUMERICAL MODEL GUIDANCE. HOWEVER, MODELS DO AGREE IN AN INITIAL NORTH-NORTHWESTWARD TRACK FOLLOWED BY A NORTHEASTWARD TURN. HOWEVER, MODELS DISAGREE ON THE TIMING AND SHARPNESS OF THE TURN. THEREFORE, THERE IS LOW CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK. C. IN THE EXTENDED FORECAST PERIOD, THE MAJORITY OF THE MODELS INDICATE THAT THE STR WILL BUILD WESTWARD AFTER THE PASSAGE OF THE SHORTWAVE TROUGH AND ALLOW TS 11W TO TRACK BACK TOWARD THE NORTHWEST. THE NOTABLE EXCEPTION IS THE NAVGEM SOLUTION WHICH SHOWS A WEAKER STR AND DOES NOT TURN TS 11W BACK TO THE NORTHWEST. INSTEAD, NAVGEM INDICATES A NORTHEASTWARD TRACK BEYOND TAU 72. THE GFS ENSEMBLE ALSO INDICATES A MORE NORTHWARD TRACK BEYOND TAU 72. THE JTWC FORECAST TRACK IS PLACED NEAR THE MULTI-MODEL CONSENSUS AND FAVORS THE ECMWF AND UKMET SOLUTIONS WHICH INDICATE A NORTHWESTWARD TRACK IN THE EXTENDED FORECAST. THERE IS A MODEL SPREAD OF 350 NM BY TAU 120 WITH THE UKMET SOLUTION ON THE WESTERN EDGE OF THE CONSENSUS AND NAVGEM ON THE EASTERN EDGE OF THE CONSENSUS. DUE TO THE WIDE RANGE OF MODEL SOLUTIONS THERE IS LOW CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK.// NNNN NNNN