MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (EIGHTEEN) WARNING NR 02// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM 18W (EIGHTEEN), LOCATED APPROXIMATELY 301 NM NORTH OF CHUUK, HAS TRACKED WESTWARD AT 11 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL IMAGERY (MSI) CONTINUES TO DEPICT BROAD CIRCULATION ABOUT A POORLY DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC). A 28216Z SSMIS IMAGE REVEALS FORMATIVE BANDING ALONG THE NORTHERN PERIPHERY OF THE SYSTEM AND DEEP CONVECTION TO THE SOUTHEAST. HOWEVER THERE IS LOW CONFIDENCE IN ITS INITIAL POSITION DUE TO THE CHAOTIC NATURE OF THE SYSTEMS STRUCTURE. THE INITIAL INTENSITY IS ASSESSED AT 35 KNOTS BASED ON THE DVORAK CURRENT INTENSITY ESTIMATES FROM PGTW AND KNES. THERE IS A FAVORABLE UPPER- LEVEL ENVIRONMENT DUE TO LOW (5 TO 10 KNOTS) OF VERTICAL WIND SHEAR (VWS) AND RADIAL OUTFLOW, WITH THE POSSIBILITY OF A POINT SOURCE TO THE NORTHWEST. TS 18W IS TRACKING TO THE WEST ALONG THE SOUTHERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR). 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 18W WILL CONTINUE TO TRACK ALONG THE SOUTHWESTERN EDGE OF THE STR THROUGH THE NEXT 72 HOURS, TAKING A MORE NORTHWESTWARD ROUTE. LIMITED MODEL GUIDANCE IS IN OVERALL GOOD AGREEMENT WITH THE SYSTEM TRACKING TO THE NORTHWEST OVER THE NEXT 48 HOURS. ADDITIONALLY, EXPECT THE UPPER-LEVEL ENVIRONMENT TO IMPROVE AND HIGH SEA SURFACE TEMPERATURES ALONG THE TRACK TO POSSIBLY PRODUCE A RAPID INTENSIFICATION SCENARIO WITHIN THE NEXT 72 HOURS. IT SHOULD BE NOTED THAT THE SPREAD IN THE MODELS BECOME MORE SIGNIFICANT NEAR TAU 72, WITH A DISPARITY OF ABOUT 200NM. C. IN THE EXTENDED FORECAST, THERE IS MODERATE DISAGREEMENT IN MODELS WITH REGARD TO THE STRENGTH OF THE STR AND WHERE TS 18W BEGINS TO TURN INTO THE BREAK IN THE RIDGE. HWRF CONTINUES TO BE THE WESTERN, MORE FLAT OUTLIER WHILE COAMPS-TC DEPICTS THE EASTERN, MORE NORTHERN SCENARIO. DUE TO THE SPREAD OF OVER 450NM IN BY TAU 120, THE JTWC TRACK CLOSELY RESEMBLES THE MULTI-MODEL CONSENSUS WITH OVERALL LOW CONFIDENCE IN THE FORECAST TRACK.// NNNN NNNN