2002年10月7日横須賀で発生した竜巻 : 10月6日から7日にかけて各地で発生した突風災害に関連して Tornado Disaster in Yokosuka on October 7, 2002 : Strong Wind Disasters from October 6 through 7, 2002

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2002年10月6日から7日にかけて発達した低気圧の北東進に伴い,各地で突風災害が相次いだ.横須賀市内では10月7日04時頃突風災害が発生した.現地調査の結果,被害は100か所を越える住家で確認され,被害域はほぼ直線的で長さ2.5km,最大幅は約150m(平均で30~50m)であった.被害スケールはF1から局所的にF2であった.被害域は連続しておらず,かつ蛇行していた.また,最も被害の大きかった公郷小学校付近で被害幅が広がっており,竜巻の複雑な挙動が示唆された.最大風速に関しては,被害が最も甚大であった場所の東端に位置する道路標識から少なくとも風速は34~38ms^<-1>と見積もられ,被害スケール(F1)を裏付けた.今回の突風は以下の理由から竜巻であったと推測された.地上被害の特徴から,1)被害域の幅が狭く直線的である.2)回転性(低気圧性)の風による痕跡が確認された.3)吸い上げ渦とおもわれる痕跡が2か所確認された.4)吸い上げ渦の痕跡近傍では,実際に体育館の屋根や空調室外機が少なくとも高さ10mは吹き上げられた.上空の積乱雲の特徴は,5)強エコー域の南西端に被害域が対応していた.6)ドップラー速度パターンには直径7kmの渦が上空に確認された.7)このメソサイクロンの影響をうける地上観測点では,1hPaの気圧降下が確認された.横須賀市の竜巻被害は,発達した低気圧の暖域で形成された積乱雲群が広範囲にわたりもたらした竜巻(ダウンバースト)の中のひとつに位置づけられる.

As an extratropical cyclone developed on October 6,2002 and moved east, extensive wind disasters occurred in various places in Japan. Areas presently known to be damaged areas are Kaseda-city in Kagoshima, Kagoshima-city, Minamichita-cho in Aichi, Hamamatsu-city in Shizuoka, Ohshima cho in Tokyo, Miura-city and Yokosuka-city in Kanagawa, Tateyama-city in Chiba. In Yokosuka-city at approximately 03:50 JST on October 7,2002 a gust with thunderstorm occurred and caused damage in Morisaki, Kugo-cho and Miharu-cho. We were able to assess the features of damage in a densely built-up area where ground level can vary by 20-30m. The maximum wind speed cannot be fully determined because of the lack of structures appropriate for speed estimation. However, judging by the damage of the traffic sign, we can deduce that the damage scale of the tornado was F1 and locally F2. The tornado was rated F2-P1-P1 on the Fujita-Pearson scale. There are three reasons why the gust in the area was a tornado as follows. 1) The damaged area lies in a narrow line. 2) Indication of rotatory (cyclonic) wind was observed. 3) Two signs of suction vortices were found. Damage to over 100 residential buildings was observed and the damage area extends over a line of about 2.5km by 150m. Looking in detail at the damage map, we can see that the damaged area is discontinuous and meandering. The discontinuity is probably due to the repetitive touchdown (the so-called 'tornado jump') affected by the rugged landscape. The damaged area, which extends mostly near Kugo elementary school, indicates the complicated tornado's path in the mature stage. The features of the parent cloud were as follows: 4) The damage area was located at southwestern edge of the strong echo. 5) The vortex with 7km in diameter (mesocyclone) was observed by a Doppler radar. 6) Pressure drop of 1hPa was recorded below the mesocyclone. The wind disaster in Yokosuka was caused by one of the tornadoes, which formed in the tapering cloud developed in the warm sector of a synoptic low.

収録刊行物

  • 天気

    天気 54(1), 53-64, 2007-01-31

    日本気象学会

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  • NII論文ID(NAID)
    110006165053
  • NII書誌ID(NCID)
    AN00151568
  • 本文言語コード
    JPN
  • 資料種別
    ART
  • ISSN
    05460921
  • NDL 記事登録ID
    8673933
  • NDL 雑誌分類
    ZM43(科学技術--地球科学--気象)
  • NDL 請求記号
    Z15-35
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    CJP書誌  CJP引用  NDL  NII-ELS  NDL-Digital 
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