WDPN31 PGTW 090900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 04W (FOUR) WARNING NR 002// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 8.1N 152.1E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 541 NM SOUTHEAST OF ANDERSEN AFB MOVEMENT PAST 6 HOURS: WESTWARD AT 03 KTS SIGNIFICANT WAVE HEIGHT: 16 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A LARGE, SLOWLY CONSOLIDATING LOW-LEVEL CIRCULATION CENTER (LLCC) WITH FORMATIVE BANDING NORTHWEST OF THE CENTER AND GOOD POLEWARD UPPER-LEVEL OUTFLOW. LOCATED SOUTH OF A WEAKNESS IN THE SUBTROPICAL RIDGE, TD 04W IS SLOWLY TRAVERSING WESTWARD OVER WARM SEA SURFACE TEMPERATURES (SST) OF 28-29 DEGREES CELSIUS AND HIGH MID-LEVEL MOISTURE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE DEFINED, PARTIALLY EXPOSED LLCC AND A 090329Z AMSR2 89 GHZ IMAGE. THE INTENSITY IS SET AT 30 KTS WITH HIGH CONFIDENCE BASED ON THE T2.0 FROM PGTW AND KNES AMIDST GRADUAL IMPROVEMENT IN STRUCTURE OBSERVED IN THE VISIBLE IMAGERY. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: COMBINATION OF THE BETA EFFECT AND AN EXTENSION OF A DEEP LAYER, NEAR-EQUATORIAL RIDGE TO THE EAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.0 - 30 KTS RJTD: T1.0 - 25 KTS KNES: T2.0 - 30 KTS CIMSS SATCON: 28 KTS AT 090410Z CIMSS ADT: 30 KTS AT 090540Z CIMSS AIDT: 31 KTS AT 090540Z CIMSS D-MINT: 31 KTS AT 090618Z CIMSS D-PRINT: 26 KTS AT 090710Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 28-29 CELSIUS OUTFLOW: MODERATE POLEWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: NOT APPLICABLE 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THE FORECAST INTENSITY HAS BEEN SIGNIFICANTLY INCREASED. FORECAST DISCUSSION: TD 04W IS LOCATED IN A WEAK STEERING ENVIRONMENT WITH A NORTHWEST EXTENSION OF A NEAR-EQUATORIAL RIDGE (NER) TO THE EAST AND A STRONG SUBTROPICAL RIDGE (STR) CENTERED NEAR LUZON. AFTER TAU 36, THE NER WILL BUILD AND INDUCE A MORE NORTHWESTWARD MOTION. THE RIDGE WILL CONTINUE TO STRENGTHEN AND GUIDE THE SYSTEM TOWARDS THE MARIANA ISLANDS THROUGH TAU 120. THERE REMAINS SIGNIFICANT CHALLENGES IN THE EXTENDED FORECAST TRACK. TD 04W WILL ENCOUNTER COMPETING STEERING INFLUENCES: FROM THE EXTENSION OF THE NER TO THE EAST AND THE STR TO THE WEST. A STRONGER NER WILL PUSH THE SYSTEM MORE POLEWARD, WHILE A WEAKER RIDGE WILL LEAD TO A MORE ZONAL TRACK. THE FORECAST CURRENTLY FAVORS THE MORE ZONAL FORECAST VICE THE STRONGLY POLEWARD TRAJECTORY AS DEPICTED IN SOME OF THE MODEL GUIDANCE. THE INTENSITY FORECAST IS MORE STRAIGHTFORWARD. THE ENVIRONMENTAL CONDITIONS WILL BE HIGHLY FAVORABLE FOR CONTINUED DEVELOPMENT. LOW VWS, PLENTIFUL MID-LEVEL MOISTURE, AND WARM SST WILL FUEL INTENSIFICATION. THE FORECAST RATE OF DEEPENING INITIALLY FOLLOWS THE CLIMATOLOGICAL RATE, GIVEN THE SIZE OF THE CIRCULATION. MORE SIGNIFICANT INTENSIFICATION TOWARDS A 115 KT PEAK IS THEN FORECAST AS THE INNER CORE BECOMES ESTABLISHED BY TAU 48. IT IS IMPORTANT TO NOTE THAT THE WIND FIELD WILL EXTEND FAR OUT FROM THE CENTER, MAKING FOR FAR-REACHING IMPACTS. THE FORECAST HOLDS THE INTENSITY AT TAU 120 WITH LOW CONFIDENCE DUE TO THE EFFECTS OF A SLIGHTLY WORSE ENVIRONMENT. MODEL DISCUSSION: THE FORECAST TRACK LARGELY FOLLOWS THE MULTI-MODEL CONSENSUS, WHICH IS CLOSELY ALIGNED WITH THE ECMWF AND THE ECEPS MEAN. THE EXPERIMENTAL AI MODELS, ALONG WITH THE GALWEM AND UKMET SUGGEST A MORE POLEWARD TRACK, TRACKING EAST OF THE MARIANAS, WHILE THE GFS FAVORS A MORE ZONAL MOTION. THERE IS CONSIDERABLE UNCERTAINTY IN THE ENSEMBLE MEMBERS, WITH OUTLIERS SPREAD ACROSS OVER 1200 NM, BUT GENERALLY FOCUSED ON THE SOUTHERN MARIANAS. CROSS-TRACK SPREAD IN THE CONSENSUS MEMBERS INCREASES TO 420 NM BY TAU 120. ALL MODELS DEPICT INTENSIFICATION THROUGH TAU 96, AFTER WHICH TIME A COMBINATION OF LESS IDEAL ENVIRONMENTAL CONDITIONS AND INTERNAL STORM DYNAMICS MAY CAP THE INTENSITY. THE INTENSITY FORECAST FOLLOWS THE CONSENSUS THROUGH TAU 48 WITH MEDIUM CONFIDENCE AT ROUGHLY THE CLIMATOLOGICAL RATE. FROM TAU 48 TO TAU 120, THE INTENSITY IS HEDGED CLOSER TO THE COAMPS-TC AND HAFS-A MODELS WITH MEDIUM CONFIDENCE. THE HAFS-A INTERPOLATION NOTABLY DEPICTS A PEAK INTENSITY OF 130 KTS WHEN THE STORM WILL BE AT ITS CLOSEST APPROACH TO GUAM, HIGHLIGHTING THE UNCERTAINTY IN THE PEAK INTENSITY AT TAU 96. FORECAST CONFIDENCE: TRACK 00-72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN