Advisories

WDPN32 PGTW 200300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 29W (CHAMPI) WARNING NR 
023//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.9N 135.6E
   INITIAL INTENSITY: 130 KTS
   GEOGRAPHIC REFERENCE: 766 NM SOUTH-SOUTHWEST OF CHICHI JIMA
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 55 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS SUPER
TYPHOON (STY) 29W CONTINUING TO BARREL NORTHWESTWARD, MAINTAINING A
SOLID INNER EYE MEASURING 19 NM IN DIAMETER AND +18C IN CORE
TEMPERATURE. THE DEEP CONVECTION ALONG THE NORTHERN SEMICIRCLE OF
THE STORM IS BEGINNING TO COLLAPSE; THE ONLY SIGNAL THE STORM IS
CONTINUING ITS ERC. THE LACK OF RECENT MICROWAVE DATA PRECLUDES
ANALYSIS OF THE ERC PROGRESS. THE 192036Z RCM-1 SAR WINDSPEED DATA
REVEALS A VAST EXPANSE OF DESTRUCTIVE WINDS, PARTICULARLY WITHIN
THE NORTHERN PERIPHERY. ENVIRONMENTAL ANALYSIS REVEALS A HIGHLY
FAVORABLE ENVIRONMENT CHARACTERIZED BY LOW (5-10 KTS) VERTICAL WIND
SHEAR (VWS), WARM (29-30 C) SEA SURFACE TEMPERATURES (SST), HIGH
(125-150 KJ PER CM SQUARED) OCEAN HEAT CONTENT (OHC), AND ROBUST
DUAL-CHANNEL OUTFLOW. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE WELL-DEFINED EYE IN ANIMATED SATELLITE
IMAGERY. THE INITIAL INTENSITY OF 130 KTS IS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE EARLIER SAR DATA, WHICH SHOWS A PEAK
INTENSITY NEAR 130 KTS, SUPPLEMENTED BY THE STRONG AGREEMENT
BETWEEN THE AGENCY DVORAK FIXES AND AUTOMATED CIMSS INTENSITY
ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: 192036Z RCM-1 SAR WINDSPEED DATA

CURRENT STEERING MECHANISM: THE SOUTHWESTERN PERIPHERY OF AN
ELONGATED SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTH 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   RJTD: T6.5 - 127 KTS
   RCTP: T6.5 - 127 KTS
   CIMSS ADT: 127 KTS AT 200100Z
   CIMSS AIDT: 133 KTS AT 200100Z
   CIMSS D-PRINT: 133 KTS AT 200100Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG DUAL-CHANNEL
   OTHER FACTORS: ONGOING EYEWALL REPLACEMENT CYCLE (ERC)

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: STY 29W (CHAMPI) IS FORECAST TO CONTINUE TRACKING 
ALONG THE SOUTHWESTERN PERIPHERY OF THE ELONGATED STR TO ITS NORTH. BY 
ABOUT TAU 24, A SHORTWAVE TROUGH PASSING TO THE NORTH OF THE RIDGE IS 
EXPECTED TO FORCE THE STR TO RETREAT EASTWARD. THE TROUGH AND 
RETREATING RIDGE ARE EXPECTED TO CAUSE A SIZABLE BREAK BETWEEN THE 
STEERING RIDGE AND A SHALLOWER RIDGE CENTERED OVER SOUTHEAST ASIA. 
NEITHER THE BREAK NOR SECOND RIDGE WILL HAVE AN IMMEDIATE IMPACT ON 
CHAMPI'S TRACK MOTION, WHICH IS EXPECTED TO HAVE A STEADY 
NORTHWESTWARD TRAJECTORY THROUGH TAU 48. NO LATER THAN 48, THE SECOND 
RIDGE OVER CHINA IS EXPECTED TO RETROGRADE TO OVER MAINLAND SOUTHEAST 
ASIA, EMPHASIZING THE COL REGION BETWEEN THE RIDGES. SIMULTANEOUSLY, 
29W WILL BEGIN TO SLOW ITS FORWARD ADVANCE AND TURN POLEWARD INTO THE 
WEAKNESS CREATED BY THE PASSING TROUGH. 29W IS EXPECTED TO ROUND THE 
STR BETWEEN TAU 72-120, CROSSING THE RYUKYU ISLANDS BETWEEN TAU 72-96 
AND APPROACHING THE RIDGE AXIS NEAR TAU 96. BETWEEN TAU 96-120, CHAMPI 
IS EXPECTED TO TRACK NORTHEASTWARD ALONG THE NORTHWEST PERIPHERY OF 
THE STR. REGARDING INTENSITY, 29W IS EXPECTED TO WEAKEN THROUGH THE 
NEXT 6-12 HOURS AS IT COMPLETES THE ERC, WITH MORE PRONOUNCED 
WEAKENING POSSIBLE AT TAU 6. AFTER TAU 12, 29W IS EXPECTED TO REGAIN 
INTENSITY AS IT RECOVERS AND THE INNER EYEWALL CONTRACTS, ULTIMATELY 
REACHING 145 KTS IN 24 HOURS. THE ENVIRONMENT WILL REMAIN HIGHLY 
FAVORABLE THROUGH TAU 36, WITH LOW VWS, HIGH SSTS, AND ROBUST DUAL-
CHANNEL OUTFLOW THE ENTIRE TIME, SUPPLEMENTED BY OHC INCREASING TO 
ABOVE 150 KJ PER CM SQUARED BRIEFLY AROUND TAU 12, AIDING IN 29W 
REACHING ITS SECOND PEAK. 29W IS FORECAST TO WEAKEN GRADUALLY
BETWEEN TAU 24-48, AS IT TRACKS OUT OF THE HIGH OHC AND SIGNIFICANT
UPWELLING BEGINS TO IMPACT THE SYSTEM. ADDITIONALLY, THE POSSIBILITY 
FOR SUBSEQUENT ERCS PERSISTS WHILE CHAMPI REMAINS AN INTENSE SYSTEM, 
WHICH WOULD CAUSE FURTHER UNPREDICTABLE WEAKENING, ESPECIALLY IF THE 
STORM FAILS TO COMPLETE THE CYCLE. AFTER ABOUT TAU 36, OHC WILL 
DECREASE TO 75-100 KJ PER CM SQUARED AND SSTS WILL DECREASE TO 27-28C. 
AS A RESULT OF THOSE FACTORS OCCURRING IN CONJUNCTION WITH 29W SLOWING 
ITS FORWARD TRAJECTORY, THE UPWELLING IS EXPECTED TO BECOME MORE 
PRONOUNCED. OHC IS FORECAST TO DECREASE TO BELOW 75 KJ PER CM SQUARED 
NO LATER THAN TAU 48, AND CHAMPI IS EXPECTED TO CROSS THE 26C ISOTHERM 
AROUND TAU 96, THOUGH THE UPWELLING WILL LIKELY INTRODUCE SUB-26C 
WATER MUCH SOONER. AS A RESULT, 29W IS FORECAST TO WEAKEN RAPIDLY FROM 
TAU 48-120.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN STRONG 
AGREEMENT THROUGH TAU 36. FOLLOWING TAU 36, MODEL GUIDANCE STRUGGLES 
TO INTERPRET THE COMPLEX RIDGING LAYOUT. THERE IS A DISTINCT 
BIFURCATION BETWEEN THE PHYSICS-BASED MODELS AND THE AI-BASED MODELS: 
THE PHYSICS-BASED MODELS -- INCLUDING GFS, GEFS, ECMWF, AND ECENS -- 
DEPICT A STRAIGHT RUNNING TRACK THAT PROGRESSES NORTHWESTWARD THROUGH 
TAU 120, WITH LANDFALLS IN TAIWAN AND CHINA. GSM, NAVGEM, AND THE AI-
BASED MODELS -- INCLUDING GOOGLE DEEPMIND, AI ECMWF, AND AI ECENS -- 
DEPICT A RECURVE SCENARIO WHERE 29W CURVES INTO THE WEAKNESS CREATED 
BY THE SHORTWAVE TROUGH AND TRACKS NORTHEASTWARD TOWARDS JAPAN. EVEN 
WITHIN THE RECURVE SCENARIO, A SPLIT BETWEEN FASTER MODELS AND SLOWER 
MODELS EMERGES. GSM AND NAVGEM -- THE TWO PHYSICS-BASED MODELS 
DEPICTING THE RECURVE, ARE SIGNIFICANTLY SLOWER THAN MANY OF THE AI 
MODELS. AT TAU 120, GSM AND NAVGEM ARE STILL WELL WITHIN THE EAST 
CHINA SEA. GOOGLE DEEPMIND AND AI ECENS, HOWEVER, ARE ALREADY 
POSITIONED OVER SOUTHERN JAPAN AT THE SAME TIME AS THE FASTEST 
RECURVING MEMBERS. THE ALONG-TRACK SPREAD IS APPROXIMATELY 420 NM AT 
TAU 120. THERE IS SIGNIFICANT UNCERTAINTY IN THE LATE-TERM JTWC TRACK 
FORECAST DUE TO BOTH THE BIFURCATION AND SPEED DIFFERENCE IN RECURVING 
MEMBERS. SHOULD THE FASTER AI MODELS (INCLUDING GOOGLE DEEPMIND) PROVE 
CORRECT, ASSETS IN SASEBO COULD SEE IMPACTS AROUND TAU 120. THE JTWC 
TRACK FORECAST IS PLACED CLOSE TO THE AI MODEL CONSENSUS WITH OVERALL 
LOW CONFIDENCE. RELIABLE INTENSITY AIDS ARE IN GOOD AGREEMENT THROUGH 
TAU 120, THOUGH NONE REGISTER THE ONGOING ERC AND RESULTING INTENSITY 
DROP. EVEN SO, THE JTWC INTENSITY FORECAST IS PLACED WITH OVERALL 
MEDIUM CONFIDENCE.

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