Direction of tornado movement and its relationship with the large-scale wind field

According to Niino et al. (1997), more than half of tornadoes in Japan between 1961 and 1993 moved toward the northeast quadrant. Since their data was subjective assessments incorporating damage surveys and field reports, however, the resulting directions of tornado movements were biased toward 8 directions (e.g., N, NE, E) out of 16 (e.g., N, NNE, NE, ENE). Using latitudes and longitudes of the starting and end points of tornado damage paths in the database of gusty winds of the Japan Meteorological Agency, our study objectively examined the statistics of the direction of tornado movement and its relation with the large-scale wind field. The analysis revealed that approximately 70% of tornadoes moved toward the northeast quadrant in accord with the previous study. The preference for the northeastward movement remains similar for both periods of 1961–1993 and 1994–2023, although the Japan Meteorological Agency changed several times their operation to collect tornado report data. This northeast preference consists of eastward and northward peaks. The eastward peak is caused by cumulonimbus clouds that are steered by the mid-tropospheric westerly winds to the first order. The northward peak, which is more frequent in JJA and SON, overall results from typhoon-associated tornadoes. Tornado movement directions and environmental winds at around 750 hPa are significantly correlated, presumably indicating that tornadoes generally move along with their parent cumulonimbus clouds, which are steered by the mid-tropospheric environmental wind.