WDPN31 PGTW 041500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 02W (PENHA) WARNING NR 003// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 8.7N 131.5E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 711 NM EAST-SOUTHEAST OF MANILA, PHILIPPINES MOVEMENT PAST 6 HOURS: WESTWARD AT 11 KTS SIGNIFICANT WAVE HEIGHT: 15 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: TROPICAL DEPRESSION (TD) 02W (PENHA) REMAINS HIGHLY ASYMMETRIC AND DISORGANIZED AS IT MAINTAINS A WESTWARD TRACK TOWARDS THE PHILIPPINES. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DEEP CONVECTION FORMING ON THE SOUTHEASTERN TERMINUS OF A CONVERGENT INFLOW BAND, COALESCING INTO A MESOSCALE CONVECTIVE CLUSTER APPROXIMATELY 110NM TO THE NORTHEAST OF THE FULLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) ASSOCIATED WITH TD 02W. RECENT INFRARED DATA INDICATES A LOCALIZED CELL OF ISOLATED CONVECTION DEVELOPING APPROXIMATELY 40NM WEST OF THE LLCC. THE SUSTAINABILITY OF THIS CONVECTIVE PULSE AS A PRECURSOR TO A ROBUST CONSOLIDATION PHASE REMAINS TO BE SEEN. A 040957Z SSMIS 91GHZ MICROWAVE PASS REVEALED A WELL-DEFINED BUT BROAD CIRCULATION, WITH AN INNER-CORE DEVOID OF DEEP CONVECTION AND FRAGMENTED FORMATIVE BANDING EXTENDING ACROSS THE NORTHERN SEMICIRCLE. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE EXPOSED LLCC IN THE EIR IMAGERY. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE SUPPORTED BY SUBJECTIVE AND OBJECTIVE ESTIMATES OUTLINED BELOW. ENVIRONMENTAL CONDITIONS REMAIN MARGINALLY FAVORABLE, WITH ROBUST POLEWARD OUTFLOW MITIGATING MODERATE EASTERLY VERTICAL WIND SHEAR (VWS); WARM SSTS CONTINUE TO PROVIDE AMPLE THERMODYNAMIC FORCING, NOTWITHSTANDING A MID-LEVEL DRY TONGUE PERSISTING IN THE SOUTHEASTERN QUADRANT OF THE CIRCULATION. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A LOW- TO MID-LEVEL SUBTROPICAL RIDGE (STR) CENTERED EAST OF TAIWAN. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T2.0 - 30 KTS KNES: T2.5 - 35 KTS CIMSS ADT: 33 KTS AT 041140Z CIMSS AIDT: 32 KTS AT 041140Z CIMSS D-MINT: 33 KTS AT 040937Z CIMSS D-PRINT: 28 KTS AT 041230Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 15-20 KTS SST: 28-29 CELSIUS OUTFLOW: STRONG POLEWARD OTHER FACTORS: HIGHLY ASYMMETRIC WIND FIELD; VERTICAL VORTEX DISPLACEMENT. ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: NOT APPLICABLE 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TD 02W HAS ESTABLISHED A WESTWARD TRACK AS IT TRANSITS THE SOUTHERN AXIS OF THE STR EAST OF TAIWAN. THIS ZONAL MOTION IS FORECAST TO PERSIST THROUGH TAU 24, AT WHICH POINT THE SYSTEM WILL BE SITUATED PROXIMAL TO THE NORTHEASTERN COAST OF MINDANAO. TD 02W IS PROJECTED TO RECURVE NORTHWESTWARD AFTER TAU 24 IN RESPONSE TO THE RAPID EASTWARD RETREAT OF THE STEERING RIDGE. BY TAU 36, TD 02W WILL BE POSITIONED WITHIN THE BOHOL SEA, TRACKING NORTHWESTWARD WITH A FORECAST PATH CLIPPING SOUTHERN CEBU BEFORE TRANSITING SOUTHERN NEGROS THROUGH TAU 48. TRANSLATION SPEEDS WILL DECELERATE MARKEDLY AFTER TAU 48 AS THE RIDGE ATTENUATES AND MIGRATES EASTWARD, RESULTING IN A WEAK STEERING GRADIENT. BETWEEN TAU 48 AND TAU 72, TD 02W WILL SLOWLY CROSS THE NORTHERN PORTION OF THE SULU SEA BEFORE CROSSING NORTH OF PALAWAN AND INTO THE SOUTH CHINA SEA BY TAU 96. REGARDING INTENSITY, REDUCED SHORT-TERM VWS WILL PERMIT TD 02W TO STRENGTHEN TO A PEAK OF 40 KNOTS PRIOR TO LANDFALL IN MINDANAO. HOWEVER, THE ABSENCE OF A CONSOLIDATED, VERTICALLY ALIGNED VORTEX STRUCTURE, COUPLED WITH LIMITED TIME OFFSHORE, WILL CONSTRAIN THE INTENSIFICATION POTENTIAL. THE SYSTEM IS EXPECTED TO TRANSIT A RELATIVELY NARROW PORTION OF MINDANAO, THEREBY MINIMIZING FRICTIONAL EFFECTS; CONSEQUENTLY, THE SYSTEM IS FORECAST TO EMERGE INTO THE BOHOL SEA AS A MINIMAL TROPICAL STORM. SUFFICIENT FORWARD VELOCITY WILL CARRY IT RAPIDLY ACROSS CEBU AND NEGROS, WHILE PERSISTENT LOW SHEAR DURING THIS WINDOW SHOULD ALLOW THE SYSTEM TO SUSTAIN 35 KNOT INTENSITY THROUGH TAU 48. UPON ENTRY INTO THE SULU SEA, VWS IS FORECAST TO INCREASE SHARPLY, MID-LEVEL ENTRAINMENT OF DRY AIR WILL BEGIN AGAIN, AND THE UPPER-LEVEL FLOW PATTERN TURNS CONVERGENT, ALL OF WHICH WILL PRECIPITATE A WEAKENING PHASE. AS THE SYSTEM TRANSITS INTO THE SCS, THE WESTERN FLANK WILL INTERACT WITH A GALE-FORCE NORTHEASTERLY COLD SURGE. SURGE-RELATED ADVECTION WILL EXACERBATE ASYMMETRY WHILE MAINTAINING GRADIENT WINDS OF 25-30 KNOTS. HOWEVER, TD 02W WILL LACK TROPICAL CHARACTERISTICS AFTER TAU 96 AS DRY AIR ENTRAINMENT SUPPRESSES REMNANT CONVECTION AND THE VORTEX BECOMES EMBEDDED ALONG THE COLD SURGE BOUNDARY. MODEL DISCUSSION: DETERMINISTIC, ENSEMBLE, AND ARTIFICIAL INTELLIGENCE (AI) MODELS ARE IN TIGHT ALIGNMENT, PARTICULARLY THROUGH TAU 48. AT THAT JUNCTURE, NAVGEM REMAINS A STATISTICAL OUTLIER, DEPICTING AN ERRONEOUS NORTH-NORTHEASTWARD RECURVATURE EAST OF MANILA, AND HAS BEEN EXCLUDED FROM THE CONSENSUS. THE REMAINDER OF THE GUIDANCE SUITE EXHIBITS HIGH COHESION, WITH TRACKERS CONFINED TO A 75NM ENVELOPE CENTERED ON THE UPDATED CONSENSUS MEAN. THE JTWC FORECAST IS POSITIONED NEAR THE CONSENSUS MEAN THROUGH THE FORECAST PERIOD WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS EXHIBITING INCREASED CONVERGENCE, WITH ALL MODELS CONSTRAINED TO A 30-40 KNOT BAND THROUGH THE MAJORITY OF THE FORECAST. MAXIMUM PROJECTED INTENSITY IS CAPPED AT 40 KNOTS IMMEDIATELY PRE-LANDFALL, FOLLOWED BY A GENERAL WEAKENING TREND, ALTHOUGH ONLY SHIPS DEPICTS ATTENUATION BELOW 25 KNOTS. THE JTWC FORECAST IS PLACED NEAR THE CTCX TRACE THROUGH TAU 24, THEN CLOSE TO THE CONSENSUS THROUGH THE REMAINDER OF THE FORECAST PERIOD. OF NOTE, THE SYSTEM IS EXPECTED TO UNDERGO DISSIPATION OVER WATER BY THE END OF THE PERIOD, DESPITE RETAINING 30 KNOT WIND SPEEDS. AS STATED, WHILE THE PRESSURE GRADIENT WILL SUPPORT 30 KNOT WINDS ALONG THE WESTERN PERIPHERY, THE VORTEX WILL BECOME HIGHLY ELONGATED, SHALLOW, AND ASSIMILATED INTO THE COLD SURGE BOUNDARY, THEREBY CEASING TO MEET THE CRITERIA FOR A TROPICAL CYCLONE. FORECAST CONFIDENCE: TRACK 00-72 HR: HIGH TRACK 72-120 HR: MEDIUM INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN