Advisories

WDPN32 PGTW 200900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 29W (CHAMPI) WARNING NR 
024//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.5N 134.4E
   INITIAL INTENSITY: 135 KTS
   GEOGRAPHIC REFERENCE: 704 NM SOUTH-SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 58 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
SUPER TYPHOON (STY) 29W HAS A VERY IMPRESSIVE APPEARANCE. DURING
THE PAST TWO HOURS, STY 29W HAS QUICKLY RECOVERED FOLLOWING
COMPLETION OF AN EYEWALL REPLACEMENT CYCLE (ERC). ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A 25-NM-WIDE,
CIRCULAR EYE EMBEDDED IN A THICK CENTRAL DENSE OVERCAST WITH A
SMOOTHING CIRRUS CANOPY. CLOUD TOP TEMPERATURES HAVE RAPIDLY
COOLED, WITH A THICK RING OF THE WHITE SHADE (-70 TO -75 DEGREES
CELSIUS) IN THE BD-ENHANCED IR IMAGERY FULLY ENCIRCLING THE EYE,
WHICH HAS BEEN AS WARM AS +20 DEGREES CELSIUS. THE LAST SEVERAL
FRAMES DEPICT A WIDENING RING OF THE COLD-MEDIUM-GRAY SHADE
ENCIRCLING THE EYE. CONVECTION IS BEGINNING TO FLARE ALONG THE FAR
OUTER PERIPHERY OF THE CIRCULATION, AND THE UPPER-LEVEL OUTFLOW IS
EXPANDING. THESE CHANGES SUGGEST THAT STY 29W IS BEGINNING ANOTHER
ROUND OF SIGNIFICANT INTENSIFICATION. BECAUSE THE ERC HAS ONLY
RECENTLY COMPLETED, THE INITIAL INTENSITY HAS BEEN SET AT 135 KTS
WITH MEDIUM CONFIDENCE, BASED ON A BLEND OF THE T6.5-7.0 DVORAK
CLASSIFICATIONS FROM PGTW, RJTD, AND RCTP. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE CLEAR, WELL-DEFINED EYE.
THE ENVIRONMENT IS EXCEPTIONAL, CHARACTERIZED BY NEAR-ZERO VERTICAL
WIND SHEAR (VWS), VERY WARM SEA SURFACE TEMPERATURES (SST) OF 30-31
DEGREES CELSIUS, AND VERY HIGH OCEAN HEAT CONTENT (OHC) OF 150-160
KJ PER CM2.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: SOUTHERN FLANK OF A DEEP-LAYER
SUBTROPICAL RIDGE POSITIONED SOUTH OF HONSHU

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T7.0 - 140 KTS 
   RJTD: T6.5 - 127 KTS
   RCTP: T6.5 - 127 KTS
   CIMSS SATCON: 136 KTS AT 200429Z
   CIMSS ADT: 124 KTS AT 200420Z
   CIMSS AIDT: 122 KTS AT 200420Z
   CIMSS D-MINT: 130 KTS AT 200430Z
   CIMSS D-PRINT: 136 KTS AT 200700Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 0-5 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG RADIAL

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE FORECAST PEAK INTENSITY HAS BEEN
INCREASED TO 160 KTS.

FORECAST DISCUSSION: STY 29W IS TRAVELING WEST-NORTHWESTWARD ALONG
THE SOUTHERN PERIPHERY OF A STR TO THE NORTH. THE RIDGE TO THE
NORTH WILL ERODE AS A PROGRESSIVE MID-LEVEL TROUGH PASSES OVER THE
KOREAN PENINSULA AND APPROACHES HONSHU. THIS WILL ALLOW THE SYSTEM
TO GRADUALLY TURN POLEWARD, CROSS THE RIDGE AXIS AFTER TAU 72, AND
RECURVE NORTHEASTWARD BY TAU 120. THE EXCEPTIONAL NEAR-TERM
ENVIRONMENTAL CONDITIONS WILL SUPPORT INTENSIFICATION TO AN
EXCEPTIONALLY HIGH PEAK INTENSITY. RECENT SATELLITE IMAGERY
INDICATES THAT 150-160 KTS MAY BE ACHIEVED WITHIN THE NEXT SIX
HOURS. BARRING INTERNAL DYNAMICS THAT MAY LIMIT THE AMOUNT OF
INTENSIFICATION, A PEAK HIGHER THAN 160 KTS IS POSSIBLE BUT
DIFFICULT TO FORECAST GIVEN THE RARITY OF SUCH INTENSITIES. VWS
WILL REMAIN LESS THAN 10 KTS THROUGH TAU 72, WHILE OHC DROPS TO
50-60 KJ PER CM2 AFTER TAU 24. AFTER PEAKING AT TAU 12, THE SYSTEM
WILL WEAKEN AT AN INCREASING RATE AS THE LARGE CIRCULATION QUICKLY
STIRS UP COOLER SUBSURFACE WATERS. AS THE SYSTEM APPROACHES THE
RIDGE AXIS, VWS WILL INCREASE AND DRY AIR WILL BECOME MORE
INFLUENTIAL, LEADING TO MORE RAPID WEAKENING BY TAU 96 AND TAU 120.

MODEL DISCUSSION: TRACK GUIDANCE IS TIGHT THROUGH TAU 36 BUT
DIVERGES SIGNIFICANTLY THEREAFTER. THE BULK OF THE DYNAMICAL MODELS
TAKE THE SYSTEM INTO TAIWAN, WHILE THE AI SOLUTIONS SHOW A
RECURVATURE SCENARIO. THERE HAS BEEN NO MEANINGFUL SHIFT AMONG THE
MORE RELIABLE MODELS THIS CYCLE. THE TAIWAN SOLUTIONS RESULT FROM
THE STR BUILDING QUICKLY AND STRONGLY BEFORE THE SYSTEM CAN GAIN
SUFFICIENT LATITUDE. THE JTWC FORECAST TRACK CONTINUES TO FAVOR THE
RECURVATURE SCENARIO DEPICTED BY AIFS AND GOOGLE DEEPMIND AND LIES
CLOSE TO THE AI-MODEL MEAN. HOWEVER, DEEPMIND AND AIFS RECURVE THE
SYSTEM SIGNIFICANTLY FASTER AND SHOW LANDFALL OVER SOUTHWESTERN
KYUSHU BY TAU 120. THE JTWC FORECAST TRACK IS NOT AS FAST AS THESE
SOLUTIONS, WITH ITS TRACK SPEED ALIGNING MORE CLOSELY WITH THE
EXPERIMENTAL WINDBORNE AI MODEL. THE DIVERGENCE IN TRACK GUIDANCE
NETS LOW CONFIDENCE IN THE JTWC EXTENDED TRACK FORECAST. THE
INTENSITY GUIDANCE IS IN TIGHT AGREEMENT THROUGH TAU 120, THOUGH
THE HAFS-A, COAMPS-TC, AND GFS SOLUTIONS ARE DISCOUNTED GIVEN THE
TAIWAN TRACK SCENARIO. THE JTWC INTENSITY FORECAST IS SET HIGHER
THAN ALL OF THE GUIDANCE THROUGH TAU 36 AND THEN CONVERGES TOWARD
DEEPMIND FROM TAU 48 TO TAU 120.

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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