Taiki OKADA

Understanding the Characteristics of Surface Winds Blowing Over Lake Biwa Related to Water Accidents

Naoyuki INUKAI

Water accidents have been occurring frequently in Lake Biwa in recent years, and the presence of wind has been pointed out as one of the causes of accidents. At Lake Biwa strong winds called Hiraoroshi sometimes blow from Hirayama located on the west side. This Hiraoroshi may cause you to be swept out to lake. The purpose of this study was to understand the characteristics of what kind of wind blows during what kind of weather by comparing past accident dates with wind date and weather maps.
I used MSM data to extract one year’s worth of wind data in order to understand the characteristics of winds in the summer, when Hiraoroshi is prevalent and water accidents occur frequently. However, in August 2023, the wind direction of Hiraoroshi was confirmed to be around 15%, indicating that Hiraoroshi occurs even in summer.
I investigated the weather map pattern of Hiraoroshi that occurs in summer. Hiraoroshi occurred for 18 days in August 2022 and August 2023, and during the total 18 days, the typhoon passing type occurred for 5 days, the west high and east low type, and the high pressure overhanging type for 8 days, and these three patterns were frequently observed. Was done. In addition, when looking at wind speed, it is necessary to be careful as strong Hiraoroshi winds are likely to blow in typhoon passing types and high pressure overhanging types.
I investigated AMeDAS data on the day Hiraoroshi was observed to understand the weather characteristics. AMeDAS data shows that the temperature tends to drop when Hiraoroshi occurs, and it is often sunny or cloudy. The suggests that it is difficult to predict the occurrence of Hiraoroshi based on the weather.
In order to prevent drifting due to Hiraoroshi, it is thought that effective measures such as checking the weather map in advance and canceling swimming if Hiraoroshi is expected to occur are considered effective.