"If you don't like the weather here, wait five minutes." That saying, or a variation of that saying is spoken proudly by locals...just about everywhere. If one place were to truly claim to be home of that saying, it should be the Black Hills region of South Dakota. On a winter day in 1943, not only did that saying actually come true, saying the weather changed in five minutes would be an understatement.
During the seven o'clock hour on January 22nd, 1943 in Spearfish, South Dakota, people were preparing to head out to work and school. They were preparing to head out into a rather cold morning with temperatures just below zero. Many were not prepared for the incredible roller coaster ride they were about to go on. That winter day saw an amazing 116 degree temperature change.
Around 7:30am the temperature was a brisk -4°. It had been very cold leading up to this event as an arctic blast swept through the area just two days prior. On this day, however, warmer Pacific air was building and moving toward the area. The arctic and warm air masses were separated by a strong frontal boundary that lay on top of the Black Hills.
To the west, temperatures were climbing toward 60°, to the east, they were staying around 0°. This boundary began to move back and forth, like tidal waters. The boundary moved toward the east, causing the warm air to crash down from the higher elevations of the hills and right into Spearfish.
Location of the frontal boundary over the Black Hills on January 22nd, 1943:
At 7:32am, the temperature hit the 45° mark. In just two minutes, the temperature rose 49°. Driving through the boundary proved to be an adventure. Cedric Barnes wrote a letter to a newspaper, saying that when he left his house that morning, it was below zero. About half way through his drive, his windshield flash frosted and he nearly drove into a ditch. By the time he got out of his car to clear his windshield, the boundary had rushed north and he said it felt like a warm spring day.
About an hour later, just after 9am, he was driving back the other way, and again his windshield flash frosted during the drive. The temperature had plummeted. Barnes stopped and found that he was only about ten feet from where he had stopped before.
The temperature in Spearfish rose to a maximum of 54° at 9am. At that time, as Barnes recounted in his letter, the boundary rushed back south of Spearfish and the temperature bottomed out at -4° by 9:27am. This time, the temperature had changed 58° in under a half an hour.
While Spearfish got the world record for fastest temperature change and much of the glory for this event, the extreme temperature changes were felt across the entire region. L.M. Jones wrote that she was traveling to Rapid City shortly after the event. She said that everyone was talking about it everywhere she stopped.
She wrote that in Lead, South Dakota the temperature was 52° and at that same time, it was -16° in Deadwood, South Dakota. These towns are just a couple of miles apart. In Lead, the 50° temperatures came in with a vengeance, like in Spearfish. The sudden rise caused windows to crack and break in the town.
Rapid City also saw an extreme temperature change. Downtown warmed to 5° by 9:20am. By 9:40am, it was 54°. That's a rise of 49° in just 20 minutes.
As with any extreme weather event, the question always comes up as to how exactly it occurred. We already know about the intense frontal boundary separating an arctic blast from building pacific warmth. There's always at least one ingredient that pushes unusual weather events to become extreme weather events.
In this case, that ingredient was the Chinook winds. Chinook winds basically occur when warm, moist air runs into the mountainous areas of the west, including the Black Hills. The air works upward and cools at the higher elevations and releases much of its moisture. The air becomes dry, which can heat much faster than moist air. The drier air then shoots down the eastern slopes of the mountains and rapidly re-warms.
The boundary was set up right over the Black Hills. Then, the Chinook winds came up and over the mountain. Those winds allowed for the boundary to move much more rapidly and allow for accelerated warming. The boundary also increased the Chinook wind's power. So, the boundary and the winds enhanced each other, leading to this extreme event.
This event made waves in the news across the country. That was especially impressive considering news at the time was completely dominated by the ongoing Work War II.
コメント