Typhoons No. 9 and No. 10, which moved northward west of Kyushu, might have indirectly caused a cold spell in the Midwest in the United States, according to an analysis by Hokkaido University Prof. Shoshiro Minobe.
Minobe says it is possible that the two typhoons forced the jet stream flowing from east to west to divert from its route and meander dramatically, changing the atmospheric movement above the United States along the way.
The two typhoons passed by the west coast of Kyushu from Sept. 2 to 7 in close succession. According to the U.S. Meteorological Administration, the Midwest met with a cold snap that is unusual for this time of year. In Denver, Col., it was scorching hot on Sept. 5 with a high of 38 C, but the temperature plummeted to 0 C on the morning of Sept. 8.
Minobe obtained meteorological data from the U.S. National Oceanic and Atmospheric Administration and analyzed the movement of the jet stream, which was flowing eastward while also meandering to the north and the south in the upper atmosphere at 30 to 60 degrees north latitude. He then found that the jet stream's meandering became more frequent than usual after the two typhoons passed Kyushu and reached the Korean Peninsula.
As a result of the analysis, it has been confirmed that around Sept. 8, the air stream moved southward through northern Canada from around Alaska, heading deep into the Midwest. According to Minobe, a strong rising current from the two typhoons seemed to cause the jet stream to move with greater fluctuation, drawing the cold air from the north to the south.
"A typhoon is a powerful weather phenomenon, so it has a significant impact on atmospheric flow and temperature along its path and in surrounding areas. You can say the jet stream fluctuated after the typhoons passed, causing a chain reaction of abnormal weather," said Prof. Takeshi Enomoto of Kyoto University.
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