老農民版夜神月

LLCC已經外露，風場掃描亦不佳，JTWC不再認為能夠增強
將逐漸轉化，03Z第二報即發布Final Warning

WTPN31 PGTW 120300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL DEPRESSION 12W (TWELVE) WARNING NR 002//
RMKS/
1. TROPICAL DEPRESSION 12W (TWELVE) WARNING NR 002   
   01 ACTIVE TROPICAL CYCLONE IN NORTHWESTPAC
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
   WIND RADII VALID OVER OPEN WATER ONLY
    ---
   WARNING POSITION:
   120000Z --- NEAR 31.5N 138.4E
     MOVEMENT PAST SIX HOURS - 015 DEGREES AT 06 KTS
     POSITION ACCURATE TO WITHIN 030 NM
     POSITION BASED ON CENTER LOCATED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   BECOMING EXTRATROPICAL
   REPEAT POSIT: 31.5N 138.4E
    ---
   FORECASTS:
   12 HRS, VALID AT:
   121200Z --- 33.6N 139.9E
   MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   EXTRATROPICAL
   VECTOR TO 24 HR POSIT: 045 DEG/ 15 KTS
    ---
   24 HRS, VALID AT:
   130000Z --- 35.7N 142.6E
   MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   EXTRATROPICAL
    ---
REMARKS:
120300Z POSITION NEAR 32.0N 138.8E.
12SEP20. TROPICAL DEPRESSION 12W (TWELVE), LOCATED APPROXIMATELY
237 NM SOUTH-SOUTHWEST OF YOKOSUKA, JAPAN, HAS TRACKED NORTH-
NORTHEASTWARD AT 06 KNOTS OVER THE PAST SIX HOURS. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI) INDICATES THAT THE IMPROVING
CONVECTIVE ORGANIZATION OBSERVED SIX HOURS AGO HAS SUCCUMBED
TO THE HIGH (20 KNOT) VERTICAL WIND SHEAR (VWS), LEAVING BEHIND A
WEAK, EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL
POSITION IS BASED ON THE LLCC IN MSI WITH HIGH CONFIDENCE. A 112304Z
ASCAT-A PASS REVEALED ONLY A FEW ISOLATED 25 TO 30 KNOT WIND BARBS
UNDER DEEP CONVECTION, AND DISPLACED 75 NM FROM THE LLCC. THE
INITIAL INTENSITY IS ASSESSED AT 25 KNOTS BASED ON THESE ISOLATED
ASCAT WINDS AND AGENCY DVORAK ESTIMATES, HOWEVER, THE EXPOSED LLCC
IS GENERALLY CHARACTERIZED BY ONLY 10-15 KNOT WINDS. 12W IS CLEARLY
INTERACTING WITH MID-LATITUDE WESTERLIES AND IS TAKING ON EXTRA-
TROPICAL CHARACTERISTICS. EXTRA-TROPICAL TRANSITION IS EXPECTED
TO BE COMPLETED WITHIN 12 HOURS, CONSISTENT WITH FSU PHASE SPACE
GUIDANCE. DYNAMIC GUIDANCE IS GOOD AGREEMENT FOR THIS SHORT
FORECAST. JTWC FORECAST CONFIDENCE IS ASSESSED AS HIGH. THIS IS THE
FINAL WARNING ON THIS SYSTEM BY THE JOINT TYPHOON WRNCEN PEARL
HARBOR HI. THE SYSTEM WILL BE CLOSELY MONITORED FOR SIGNS OF
REGENERATION. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 120000Z IS 9 FEET.
//
NNNN

uodam64402

這個系統於日本關東地區東南方經過時，由於結構與風場不穩定，因而在轉化過程中，發生LLCC替代現象，原本的LLCC逐漸鋒面化並且消散，於東北方再重新發展一個LLCC，並且由該處的對流發展且深化結構（含正壓與斜壓能）。



只是因為該系統還處於轉化的過度階段（未錮囚），且海水溫度尚可支持屬於熱帶系統的正壓發展，因而在新LLCC處，不僅產生大量對流，還疑似發展出未閉合的類眼牆結構。



由風場掃瞄已經掃出少許35KT的旗幟，預計於18UTC，應該就會改列溫帶氣旋的GW警報。該系統預計還會以溫帶氣旋的形式在日本關東／東北區域東方近海滯留一段時間。

周子堯@FB

FNMOC於22Z撤編；JMA亦於00Z判定轉換為溫帶氣旋

GALE WARNING.
DEVELOPING LOW 1002 HPA
AT 37N 146E SEA EAST OF JAPAN MOVING ENE 10 KNOTS.
WARM FRONT FROM 37N 146E TO 38N 150E 37N 156E.
COLD FRONT FROM 37N 146E TO 35N 143E 36N 141E.
WINDS 30 TO 35 KNOTS WITHIN 400 MILES OF LOW NORTHEAST SEMICIRCLE AND
300 MILES ELSEWHERE.
EXPECTED WINDS 30 TO 35 KNOTS WITHIN 400 MILES OF LOW NORTHEAST
SEMICIRCLE AND 300 MILES ELSEWHERE FOR NEXT 24 HOURS.