Advisories

WDPN32 PGTW 190300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 29W (CHAMPI) WARNING NR 
019//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.0N 139.2E
   INITIAL INTENSITY: 135 KTS
   GEOGRAPHIC REFERENCE: 278 NM NORTH-NORTHEAST OF YAP
   MOVEMENT PAST 6 HOURS: WESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 49 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS SUPER
TYPHOON (STY) 29W (CHAMPI) WITH A RAPIDLY CLEARING EYE THAT HAS
WARMED FROM -50 C UP TO 5 C OVER THE PAST SIX HOURS. AN 181844Z
F-18 SSMIS MICROWAVE PASS CONFIRMED THE SUSPECTED COMPLETION OF AN
EYEWALL REPLACEMENT CYCLE (ERC) AS IT DEPICTS A LARGE PRIMARY
EYEWALL MEASURING ROUGHLY 35 NM IN DIAMETER AND A MOAT OF 40 NM
BETWEEN THE DEEP CONVECTIVE BAND WRAPPING FROM THE NORTHERN SIDE
AROUND THE EASTERN FLANK. THE 1800Z INTENSITY WAS REASSESSED TO 130
KTS BASED ON THE INTENSIFICATION THAT FOLLOWED THIS COMPLETION OF
ERC AS THE PRIMARY EYEWALL REDUCED IN DIAMETER AND RAPIDLY WARMED. A 
LATER 182138Z F-16 SSMIS PASS SHOWED A SMALLER EYE WITH A DIAMETER OF 
20 NM AND A POSSIBLE PARTIAL SECONDARY EYEWALL FORMING ON THE EASTERN
SIDE OF THE PRIMARY EYEWALL, INDICATING THE POSSIBILITY FOR ANOTHER
ERC TO BEGIN IN THE NEAR FUTURE. THE CIMSS MPERC TOOL FOR PREDICTING
ERC HAS SLOWLY INCREASED TO A 30 TO 50 PERCENT CHANCE OF THE
FULL MODEL AND VELOCITY BASED PREDICTORS, RESPECTIVELY. ENVIRONMENTAL 
CONDITIONS ARE ASSESSED AS HIGHLY FAVORABLE AS 29W MOVES INTO AN AREA 
OF HIGH (120 KJ PER CM SQUARED) OCEAN HEAT CONTENT, LOW (5-10 KTS) 
VERTICAL WIND SHEAR (VWS), AND ROBUST POLEWARD AND EQUATORWARD 
OUTFLOW 
ALOFT. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON 
THE CLEARING EYE IN EIR AND MSI. THE INITIAL INTENSITY IS ASSESSED 
WITH HIGH CONFIDENCE, IN GOOD AGREEMENT WITH THE AGENCY DVORAK FIXES 
AND CIMSS OBJECTIVE ESTIMATES.

INITIAL WIND RADII BASIS: 182316Z METOP-B ASCAT DATA

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE CENTERED TO THE
NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T6.0 - 115 KTS
   CIMSS SATCON: 130 KTS AT 180000Z
   CIMSS ADT: 134 KTS AT 182330Z
   CIMSS AIDT: 126 KTS AT 182330Z
   CIMSS D-MINT: 113 KTS AT 182254Z
   CIMSS D-PRINT: 110 KTS AT 190000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE 1800Z INTENSITY WAS REASSESSED TO
BE 130 KTS. THE INITIAL INTENSITY OF 135 KTS IS ABOVE THE
PREVIOUSLY FORECAST TAU 12 INTENSITY.

FORECAST DISCUSSION: STY 29W IS FORECAST TO CONTINUE NORTHWESTWARD
UNDER THE STEERING INFLUENCE OF THE SUBTROPICAL RIDGE (STR)
CENTERED TO THE NORTHEAST. BY TAU 60, THE EASTWARD PROPAGATION OF A
POLAR TROUGH OVER THE KOREAN PENINSULA WILL CAUSE THE ELONGATED STR
CURRENTLY CENTERED OVER HONG KONG TO SLIDE EASTWARD AND BECOME THE
PRIMARY STEERING INFLUENCE. THIS WILL CREATE A COL BETWEEN THE
NEWLY FORMED STR TO THE NORTHEAST OF 29W AND THE WEAKER REMNANTS OF
THE ORIGINAL STR OVER HONG KONG, LEADING TO A SLOW IN TRACK SPEED
AT THIS POINT. A POLEWARD TURN BY TAU 60 IS ALSO EXPECTED AS THE
SYSTEM BEGINS RECURVING AROUND THE AXIS OF THE STR TO THE NORTHEAST, 
RESULTING IN A TRACK JUST EAST OF TAIWAN FOR THE REMAINDER OF THE 
FORECAST PERIOD. REGARDING INTENSITY, 29W IS EXPECTED TO INTENSIFY AS 
IT HAS COMPLETED ERC AND ENTERS HIGHLY FAVORABLE ENVIRONMENTAL 
CONDITIONS OF ENHANCED OHC FOR THE NEXT 48 HOURS AND ROBUST OUTFLOW 
ALOFT. A PEAK OF 145 KTS IS EXPLICITLY FORECAST BUT 29W COULD EXCEED 
THIS WITH THE ANTICIPATED ENVIRONMENTAL CONDITIONS. THE UPPER-END OF 
THE FORECAST IS LIMITED PRIMARILY BY THE POSSIBILITY OF FUTURE ERC(S) 
AND THE DIFFICULT NATURE IN FORECASTING THEIR DYNAMICAL EFFECTS ON 
THE SYSTEM. BEYOND TAU 48, A GENERAL WEAKENING TREND IS EXPECTED FOR 
THE REMAINDER OF THE FORECAST PERIOD AS THE SLOWING TRACK SPEED AND 
LOWER OHC WILL LEAD TO UPWELLING OF COOLER SSTS. THE WIND RADII BY 
TAU 120 ALSO REFLECT A WEAKENING IN THE SOUTHWESTWARD QUADRANT DUE TO 
THE EXPECTED TERRAIN INTERACTION WITH TAIWAN.

MODEL DISCUSSION: TRACK MODEL GUIDANCE IS IN GOOD AGREEMENT OUT TO
TAU 60 BEFORE BIFURCATING THEREAFTER BETWEEN PHYSICS-BASED MODELS
(AND THE AI GEFS MEAN) DEPICTING A STRAIGHT-RUNNING TRACK OVER
CENTRAL TAIWAN, WHEREAS THE REMAINDER OF AI-BASED MODELS DEPICT A
RECURVATURE AND RESULTANT OVER-WATER TRACK BETWEEN TAIWAN AND
OKINAWA. THE FNV-3 GOOGLE DEEPMIND CONTINUES TO BE THE MOST
POLEWARD SOLUTION AND THE GFS AND GEFS MEAN THE MOST EQUATORWARD.
ENSEMBLE MODEL ANALYSIS REVEALS A CONTINUED TREND OF FAVORING THE
RECURVATURE SCENARIO, SPECIFICALLY WITH THE LATEST ECENS RUN WHICH
SHOWS ROUGHLY A THIRD OF MEMBERS NOW RECURVING NORTH OF TAIWAN,
WHEREAS GEFS HAS DRIFTED SLIGHTLY SOUTHWARD DEPICTING SOME MEMBERS
GOING THROUGH THE LUZON STRAIT. PART OF THIS DISAGREEMENT IS LIKELY
DUE TO GFS CONSISTENTLY INITIALIZING 29W AT A MUCH LOWER INTENSITY 
AND THE GFS MODEL FIELDS RESOLVING THE CURRENT STEERING STR CENTERED 
TO THE NORTHEAST AS MUCH MORE DISPLACED, WHEREAS THE AIFS AND ECMWF 
FIELDS SHOW TWO SEPARATE ANTICYCLONES, WITH THE DOMINANT STR MUCH 
CLOSER TO 29W. GFS MODEL FIELDS ALSO PREDICT THE POLAR TROUGH TO 
WEAKEN AND FLATTEN THE FUTURE STEERING STR MUCH MORE THAN THE OTHER 
MODEL FIELDS, LENDING FURTHER UNCERTAINTY TO THE SOLUTIONS DEPICTED 
BY GFS-BASED TRACKERS. THE OFFICIAL JTWC TRACK FORECAST IS PLACED 
WITH MEDIUM CONFIDENCE OUT TO TAU 72 AND LOW CONFIDENCE THEREAFTER, 
CLOSELY IN LINE WITH THE MULTI-MODEL AND AI CONSENSUS IN THE SHORT 
TERM AND THEN DEVIATING TO FAVOR THE AI CONSENSUS BEGINNING AT TAU 
60. MODEL INTENSITY GUIDANCE IS IN GOOD AGREEMENT ON AN 
INTENSIFICATION AND THEN GENERAL PLATEAU OUT TO TAU 36 TO 48 BEFORE 
BEGINNING A WEAKENING TREND THEREAFTER. HAFS-A HAS RISEN TO SHOW A 
PEAK OF 155 KTS WHILE THE FNV-3 GOOGLE DEEPMIND REMAINS MORE 
CONSERVATIVE AND WEAKENS THE SYSTEM EARLIER. THE OFFICIAL JTWC 
INTENSITY FORECAST IS ASSESSED WITH MEDIUM CONFIDENCE OUT TO TAU 72 
DUE TO SHORT TERM UNCERTAINTY DISCUSSED ABOVE AND LOW CONFIDENCE 
THEREAFTER, CLOSELY IN LINE WITH HAFS-A WITH THE EXCEPTION OF THE 
PEAK INTENSITY.

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