Advisories

WDPN32 PGTW 172100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 29W (CHAMPI) WARNING NR 
014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.1N 144.8E
   INITIAL INTENSITY: 130 KTS
   GEOGRAPHIC REFERENCE: 36 NM SOUTH OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 46 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: 
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS SUPER 
TYPHOON (STY) 29W (CHAMPI) TAKING A WESTWARD TRACK OVER THE PAST FEW 
HOURS WITH LESS OF A TROCHOIDAL WOBBLE, AS SUPPORTED IN HIGH FIDELITY 
RADAR DATA FROM GUAM. THE SYSTEM HAS SINCE PASSED THE CLOSEST POINT OF 
APPROACH (CPA) ROUGHLY 10 NM SOUTH OF THE ISLAND, WHILE THE NORTHERN 
EDGE OF THE INNER EYEWALL LIKELY CLIPPED THE SOUTHERN EDGE OF GUAM AND 
THE PARTIAL SECONDARY EYEWALL PASSED OVER  THE ISLAND. WHILE THE 
PARTIAL SECONDARY EYEWALL HAS REMAINED STRONG ON THE EASTERN FLANK, A 
171701Z GPM MICROWAVE PASS REVEALS IT HAS WEAKENED IN THE NORTHWESTERN 
QUADRANT, SIGNALING A POSSIBLE STALL IN THE EYEWALL REPLACEMENT CYCLE 
(ERC). THE INNER EYEWALL REMAINS EXTREMELY COMPACT AND ROBUST, WITH AN 
EYE DIAMETER MEASURING 6 NM AND AN EYE TEMPERATURE THAT HAS RAPIDLY 
WARMED FROM -60 C TO -30 C IN THE PAST THREE HOURS AS IT CONTINUES TO 
CLEAR OUT. THE CONSISTENT SIZE IN EYE DIAMETER AND CLEARING APPEARANCE 
ALSO SUPPORTS THE LIKELIHOOD THAT THE ERC MAY NOT COMPLETE. 
ENVIRONMENTAL CONDITIONS ARE HIGHLY FAVORABLE AS STY 29W IS WITHIN 
WARM (28-29 C) SEA SURFACE TEMPERATURES, LOW (10-15 KTS) VERTICAL WIND 
SHEAR (VWS), AND EXTREMELY FAVORABLE OUTFLOW ALOFT, SUPPORTED BY AN 
EQUATORWARD OUTFLOW CHANNEL. THE INITIAL POSITION IS PLACED WITH HIGH 
CONFIDENCE BASED ON THE EYE IN EIR AND RADAR IMAGERY. THE INITIAL 
INTENSITY IS ALSO ASSESSED WITH HIGH CONFIDENCE BASED ON GOOD 
AGREEMENT ACROSS ALL AGENCY DVORAK FIXES AND CIMSS OBJECTIVE 
ESTIMATES.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: EASTERN PERIPHERY OF A SUBTROPICAL
RIDGE CENTERED OVER TAIWAN

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T7.0 - 140 KTS 
   RJTD: T6.5 - 127 KTS
   RCTP: T6.5 - 127 KTS
   CIMSS SATCON: 108 KTS AT 171617Z
   CIMSS ADT: 129 KTS AT 171730Z
   CIMSS AIDT: 128 KTS AT 171740Z
   CIMSS D-MINT: 128 KTS AT 171657Z
   CIMSS D-PRINT: 128 KTS AT 171830Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG RADIAL
   OTHER FACTORS: EQUATORWARD OUTFLOW CHANNEL AND SECONDARY EYEWALL
FORMATION

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: STY 29W IS FORECAST TO CONTINUE ON A
WEST-NORTHWESTWARD TRACK AS STEERING INFLUENCE IS BECOMING DOMINATED 
BY THE EASTERN EXTENSION OF A SUBTROPICAL RIDGE (STR) CENTERED OVER
TAIWAN. BETWEEN TAUS 12 AND 24, THIS EXTENSION IS EXPECTED TO SEPARATE 
INTO A SEPARATE STR AND MOVE EASTWARD, CREATING A WEAKNESS BETWEEN THE 
TWO STRS AND CAUSING 29W TO TURN POLEWARD AS THIS NORTHEASTERN STR IS
EXPECTED TO THEN BECOME THE PRIMARY STEERING INFLUENCE, RESULTING
IN A NORTHWESTWARD TRACK FOR THE REMAINDER OF THE FORECAST PERIOD.
SHORT-TERM WOBBLING IN TRACK CAN STILL BE EXPECTED, HIGHLY DEPENDENT 
ON IF THE STALLED ERC RESUMES, AS WELL AS FUTURE POTENTIAL ERCS. THIS 
APPLIES TO THE INTENSITY FORECAST AS WELL, AS THE DIFFICULT TO PREDICT 
NATURE OF ERC(S) COULD CAUSE SHORT TERM FLUCTUATIONS IN INTENSITY 
ABOVE OR BELOW THE OFFICIAL FORECAST. HOWEVER, GIVEN THE CURRENT 
FAVORABLE ENVIRONMENTAL CONDITIONS, IN COMBINATION WITH INCREASED 
OCEAN HEAT CONTENT (100-150 KJ PER CM SQUARED) BETWEEN TAUS 24 AND 60 
WILL ALLOW 29W TO REACH A PEAK OF 140 KTS BEFORE BEGINNING A GRADUAL 
WEAKENING TREND AS TRACK SPEED SLOWS, OHC LOWERS, AND THE POWERFUL 
SYSTEM UPWELLS COOLER SSTS.

MODEL DISCUSSION: TRACK MODEL GUIDANCE IS IN EXCELLENT AGREEMENT OF 
THE AFOREMENTIONED POLEWARD TURN BETWEEN TAUS 12 AND 24 AND AN OVERALL 
NORTHWESTWARD TRACK THEREAFTER. EXCLUDING NAVGEM AS THE SOLE 
EQUATORWARD OUTLIER, CROSS TRACK SPREAD IS 135 NM AT TAU 120, WITH THE 
BULK OF THE PHYSICS-BASED MODELS MAKING UP THE SOUTHERN PORTION OF THE 
GUIDANCE PACKAGE AND THE AI-BASED MODELS HEDGING MORE POLEWARD. THE 
OFFICIAL JTWC FORECAST IS PLACED WITH HIGH CONFIDENCE THROUGHOUT, 
HEDGING BETWEEN THE MULTI-MODEL AND AI CONSENSUS, FAVORING THE AI 
CONSENSUS SLIGHTLY IN THE LATER TAUS. INTENSITY GUIDANCE IS IN FAIR 
AGREEMENT WITH A MAJORITY OF AIDS DEPICTING A SHORT TERM 
INTENSIFICATION OR PLATEAU OUT TO TAU 84 BEFORE BEGINNING GRADUAL 
WEAKENING THEREAFTER. THE INCREASED RATE OF INTENSIFICATION OVER THE 
PAST SIX HOURS DUE TO STRENGTHENING OF THE INNER EYEWALL HAS CAUSED AN 
INCREASE TO THE UPPER-END PEAKS PREDICTED BY BOTH FNV-3 AND WNV-3 
GOOGLE DEEPMIND MODELS AT 155 KTS AND 160 KTS, RESPECTIVELY, WHILE 
HAFS-A NOW TAKES IT TO 145 KTS. TAKING THE EFFECT OF THE INTERPOLATION 
OF AIDS UP TO THIS HIGHER CURRENT INTENSITY, THE OFFICIAL JTWC 
FORECAST LIES JUST BELOW THE HAFS-A AND GOOGLE MODELS, WITH THE 
AFOREMENTIONED POSSIBILITY OF SHORT TERM DEVIATIONS ABOVE OR BELOW THE 
FORECAST, WITH MEDIUM CONFIDENCE OUT TO TAU 72 AND LOW CONFIDENCE 
THEREAFTER.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: HIGH
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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