Advisories

WDPN32 PGTW 192100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 29W (CHAMPI) WARNING NR 
022//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.4N 136.7E
   INITIAL INTENSITY: 135 KTS
   GEOGRAPHIC REFERENCE: 766 NM SOUTH-SOUTHWEST OF CHICHI JIMA
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 52 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS SUPER
TYPHOON (STY) 29W AS A VIGOROUS SYSTEM BOASTING A SYMMETRICAL EYE
MEASURING 18 NM IN DIAMETER WITH AN EYE TEMPERATURE OF +18C. THE
BULK OF THE DEEP CONVECTION ALSO RESIDES IN THE EASTERN PERIPHERY,
THOUGH NEW SPIRAL BANDS ARE CONTINUOUSLY FORMING IN THE WEST AS
WELL. THE 1911Z GMI MICROWAVE SUITE REVEALS THE STORM IS CONTINUING
ITS THIRD ERC, DEPICTING A STRENGTHENING AND CONTRACTING OUTER
EYEWALL AND A WEAKENING INNER EYEWALL. THE INNER EYEWALL REMAINS
STRONG IN THE WESTERN SEMICIRCLE, BUT HAS ERODED AWAY IN THE
EASTERN SEMICIRCLE WHERE A PROMINENT DRY SLOT HAS REPLACED IT.
ENVIRONMENTAL ANALYSIS REVEALS A FAVORABLE ENVIRONMENT,
CHARACTERIZED BY ROBUST DUAL-CHANNEL OUTFLOW, 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).
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
WELL-DEFINED EYE IN ANIMATED EIR. THE INITIAL INTENSITY OF 135 KTS
IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES
AND THE CIMSS AUTOMATED INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: THE SOUTHWESTERN PERIPHERY OF A
BUILDING SUBTROPICAL RIDGE (STR) TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T7.0 - 140 KTS 
   RJTD: T7.0 - 140 KTS 
   RCTP: T6.5 - 127 KTS
   CIMSS SATCON: 142 KTS AT 191623Z
   CIMSS ADT: 132 KTS AT 191900Z
   CIMSS AIDT: 138 KTS AT 191900Z
   CIMSS D-MINT: 144 KTS AT 191709Z
   CIMSS D-PRINT: 138 KTS AT 191900Z

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: MEDIUM
   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. THE STR WILL CONTINUE TO BUILD THROUGH THE NEXT 36
HOURS, CAUSING 29W TO ACCELERATE SLIGHTLY. AT TAU 24-36 A SHORTWAVE
TROUGH IS EXPECTED TO PASS TO THE NORTH OF THE RIDGE, CAUSING A
BREAK BETWEEN THE STEERING RIDGE AND A SECOND RIDGE CENTERED OVER
CHINA. THIS BREAK WILL NOT HAVE AN IMMEDIATE IMPACT ON CHAMPI'S
TRACK MOTION, WHICH IS EXPECTED TO HAVE A NORTHWESTWARD TRAJECTORY
THROUGH TAU 60. BY TAU 48, HOWEVER, 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 AROUND TAU
96 AND APPROACHING THE RIDGE AXIS NEAR TAU 120. REGARDING
INTENSITY, 29W IS EXPECTED TO WEAKEN THROUGH THE NEXT 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 60, WITH LOW VWS, HIGH SSTS, ROBUST DUAL-CHANNEL
OUTFLOW THE ENTIRE TIME, SUPPLEMENTED BY OHC INCREASING TO ABOVE
150 KJ PER CM SQUARED BRIEFLY BETWEEN TAU 12-24, AIDING IN 29W
REACHING ITS SECOND PEAK. 29W IS FORECAST TO WEAKEN GRADUALLY
FOLLOWING TAU 24, 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 IT FAILS TO COMPLETE THE CYCLE. AFTER ABOUT TAU 36,
OHC WILL DECREASE TO 100-125KJ 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 BY TAU 48, AND CHAMPI IS EXPECTED TO
CROSS THE 26C ISOTHERM NO LATER THAN TAU 120, THOUGH THE UPWELLING
WILL LIKELY INTRODUCE WATER COOLER THAN 26C MUCH SOONER. AS A
RESULT, 29W IS FORECAST TO WEAKEN RAPIDLY FROM TAU 72-120.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN STRONG
AGREEMENT THROUGH TAU 48. FOLLOWING TAU 48, 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, ECENS, UKMET, AND GSM -- DEPICT A STRAIGHT RUNNING TRACK
THAT PROGRESSES NORTHWESTWARD THROUGH TAU 120, WITH LANDFALLS IN
TAIWAN AND CHINA. 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. THE JTWC FORECAST REFLECTS THE
RECURVE SCENARIO. BOTH GFS AND ECMWF DEPICT THE WEAKNESS BETWEEN THE
TWO RIDGES AS A DISTINCT BREAK, YET BOTH SHOW 29W FOLLOWING THE
LOWER LEVEL FLOW BETWEEN THE TWO RIDGES. THIS SCENARIO IS DEEMED
UNLIKELY, DUE TO THE FACT THAT 29W IS FORECAST TO STILL BE A
SIGNIFICANT TYPHOON AT THAT TIME AND SHOULD HAVE NO DIFFICULTY
PUNCHING THROUGH TO RECURVE AROUND THE DEEP-LAYER STR. THIS TRACK
FORECAST PHILOSOPHY IS SUPPORTED BY THE HIGH ACCURACY OF THE
AI-BASED MODELS, WHICH HAVE ALREADY PROVEN CORRECT IN A DIFFERENT
TYPHOON WITH THE SAME ATMOSPHERIC SETUP. THE JTWC TRACK FORECAST IS
PLACED WITH MEDIUM CONFIDENCE FROM TAU 0-72 AND LOW CONFIDENCE FROM
TAU 72-120. 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: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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