WDPN32 PGTW 152100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 29W (CHAMPI) WARNING NR 006// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 11.5N 156.5E INITIAL INTENSITY: 40 KTS GEOGRAPHIC REFERENCE: 692 NM EAST OF ANDERSEN AFB MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 10 KTS SIGNIFICANT WAVE HEIGHT: 15 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL STORM (TS) 29W FORMING A NASCENT CENTRAL DENSE OVERCAST THAT IS OBSCURING THE LOW-LEVEL CIRCULATION CENTER (LLCC) BELOW. THE BULK OF DEEP CONVECTION REMAINS WEST OF THE SYSTEM, IMPACTED BY THE EASTERLY VERTICAL WIND SHEAR (VWS). A THIN LINE OF CIRRUS OUTFLOW APPEARS TO BE ATTEMPTING UPSHEAR EXPANSION, A SIGN THE SYSTEM COULD BE BEGINNING TO RESIST THE PRESSURE AND CONSOLIDATE. THE 151746Z SSMIS MICROWAVE DATA REVEALS A COMPACT SURFACE CIRCULATION WITH THE SMALL PATCH OF CENTRAL CONVECTION DISPLACED TO THE WEST, CONFIRMING THE SLIGHT WESTWARD VERTICAL TILT. ENVIRONMENTAL ANALYSIS REVEALS A FAVORABLE ENVIRONMENT, CHARACTERIZED BY LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS), WARM (29-30 C) SEA SURFACE TEMPERATURES (SST), DECENT (75-100 KJ PER CM SQUARED) OCEAN HEAT CONTENT (OHC) AND MODERATE OUTFLOW SUPPORTED BY THE EASTERLY FLOW. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED SSMIS DATA. THE INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES AND THE AUTOMATED CIMSS INTENSITY ESTIMATES LISTED BELOW. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: THE SOUTHERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTH AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS RJTD: T2.5 - 35 KTS RCTP: T3.0 - 45 KTS CIMSS SATCON: 40 KTS AT 151740Z CIMSS ADT: 49 KTS AT 151740Z CIMSS AIDT: 39 KTS AT 151740Z CIMSS D-MINT: 33 KTS AT 151722Z CIMSS D-PRINT: 43 KTS AT 151810Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-15 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE WESTWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TS 29W (CHAMPI) IS FORECAST TO CONTINUE STEADILY TRACKING WEST-NORTHWESTWARD THROUGH TAU 36 WHILE IT REMAINS ON THE SOUTHERN PERIPHERY OF THE STEERING STR CENTERED FAR TO THE NORTH. AT ABOUT TAU 36, A DEEP-LAYER TROUGH IS EXPECTED TO PASS TO THE NORTH, WEAKENING THE RIDGE AND FORCING IT TO RETREAT EASTWARD. SIMULTANEOUSLY, A SECOND STR IS EXPECTED TO BUILD IMMEDIATELY FOLLOWING THE PASSAGE OF THE TROUGH AND ASSUMING STEERING INFLUENCE OVER 29W FROM TAU 36-120. IT IS EXPECTED TO BE A SMOOTH TRANSITION FROM ONE STR TO THE OTHER, AND THE NEW STEERING ENVIRONMENT WILL MAINTAIN THE STEADY WEST-NORTHWESTWARD TRACK FOR THE REMAINDER OF THE FORECAST PERIOD. REGARDING INTENSITY, 29W IS FORECAST TO STEADILY INTENSIFY THROUGH TAU 12 WHILE THE SYSTEM CONTINUES TO CONSOLIDATE AND ORGANIZE. FOLLOWING TAU 24, 29W IS FORECAST TO UNDERGO A PROLONGED PERIOD OF RAPID INTENSIFICATION (RI) IN RESPONSE TO THE INCREASINGLY FAVORABLE ENVIRONMENT IT WILL ENCOUNTER BETWEEN TAU 24-72. THOUGH VWS IS EXPECTED TO REMAIN APPROXIMATELY 15KTS THROUGH TAU 96, THE EQUATORWARD AND WESTWARD OUTFLOW CHANNELS ARE EXPECTED TO STRENGTHEN AND CHAMPI IS EXPECTED TO TRACK THROUGH A REGION OF SLIGHTLY HIGHER (100-125 KJ PER CM SQUARED) OHC. AFTER TAU 72, 29W WILL CONTINUE TO INTENSIFY GRADUALLY UNTIL PEAKING AT TAU 96. AFTER THAT POINT, 29W WILL LIKELY MAINTAIN A HIGH INTENSITY, AS ENVIRONMENTAL CONDITIONS WILL CONTINUE TO IMPROVE. NAMELY, VWS IS EXPECTED TO DROP TO LESS THAN 10KTS BY TAU 96 AND OHC IS EXPECTED TO INCREASE TO ABOVE 150 KJ PER CM SQUARED. THIS ENVIRONMENT SHOULD HAVE NO ISSUE SUSTAINING A STRONG TYPHOON, HOWEVER, THE POTENTIAL FOR AN EYEWALL REPLACEMENT CYCLE (ERC) INCREASES, WHICH WOULD CAUSE A MOMENTARY DROP IN INTENSITY. AS A RESULT, THE INTENSITY BETWEEN TAU 96-120 REMAINS RELATIVE STABLE. THE POTENTIAL OF A PEAK INTENSITY GREATER THAN 130 KTS IS ALSO WITHIN THE REALM OF POSSIBILITY, DEPENDING ON HOW QUICKLY 29W IS ABLE TO CONSOLIDATE BETWEEN TAU 0-24, THEREBY IMPACTING WHEN THE SYSTEM IS ABLE TO COMMENCE RAPIDLY INTENSIFYING. MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN STRONG AGREEMENT THROUGHOUT THE FORECAST PERIOD, BUT PARTICULARLY THROUGH THE FIRST 48 HOURS. THE CROSS-TRACK SPREAD AS THE STORM PASSES THROUGH THE NORTHERN MARIANAS IS 85 NM, EVEN INCLUDING TWO OUTLIERS (GFS AND GEFS). DISCOUNTING THOSE, THE CROSS-TRACK SPREAD DROPS TO 55 NM AT CPA, WITH THE BULK OF GUIDANCE SUPPORTING A TRACK THAT CLIPS THE NORTHERN COAST OF GUAM OR PASSES JUST OFFSHORE. THE EXCELLENT MODEL AGREEMENT FOR THE FIRST 72 HOURS SUPPORTS THE JTWC NEAR-TERM TRACK FORECAST WITH HIGH CONFIDENCE. AFTER TAU 72, THE GUIDANCE SPREADS A MINIMAL AMOUNT, COMPOUNDING TO A 200 NM CROSS-TRACK SPREAD AT TAU 120 (EXCLUDING GFS AND GEFS), LENDING HIGH CONFIDENCE TO THE LATE-TERM JTWC TRACK FORECAST. THE JTWC TRACK FORECAST IS PLACED IN CLOSE AGREEMENT WITH THE MULTI-MODEL CONSENSUS, EXPERIMENTAL AI CONSENSUS, AND GOOGLE DEEPMIND WITH OVERALL HIGH CONFIDENCE. RELIABLE INTENSITY AIDS ARE IN GOOD AGREEMENT THROUGH TAU 36, THOUGH THERE IS SOME DISAGREEMENT REGARDING THE TIMING OF RI. SEVERAL JTWC RI INDICATORS HAVE REACHED TRIP CRITERIA, SUPPORTING THE POSSIBILITY OF RI OCCURRING WITHIN THE NEXT 24-48 HOURS. HOWEVER, THE HAFS-A AND HWRF SOLUTIONS DEPICT RI BEGINNING AS LATE AS TAU 60. MODEL GUIDANCE ALSO DISAGREES ON THE PEAK INTENSITY AND THE TIMING OF THE PEAK. THE PEAK INTENSITY SPREAD RANGES FROM 105 KTS AND 135 KTS, WITH THE TIMING SPREAD BETWEEN TAU 72 AND TAU 120. THE JTWC INTENSITY FORECAST IS IN CLOSE AGREEMENT WITH THE RI AIDS AND THE BULK OF MODELS FROM TAU 0-24, THEN HEDGED CLOSE TO THE MESOSCALE MODELS AND GOOGLE DEEPMIND FROM TAU 24 THROUGH THE END OF THE FORECAST PERIOD. THE JTWC INTENSITY FORECAST IS ASSESSED WITH OVERALL MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 00-72 HR: HIGH TRACK 72-120 HR: HIGH INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN