But what happened last Saturday changed everyone's understanding of this mountain fire, because the northern California area where the mountain fire happened is close to Nevada, and the local meteorological Doppler radar detected five tornado signals, which is absolutely unusual, because the fire tornado and the arid northern Canada must definitely "start a prairie fire with a single spark"!
The drought in California is getting worse every year.
Mountain fires happen every year in California, especially this year?
The wildfire season in California usually occurs in August-165438+1October, and dry and hot winds ravage the north and south of California. Generally, the fire season in the north will be earlier and the fire season in the south will be later. This year's fire broke out earlier than last year! By August 9, 6060 mountain fires had occurred in northern California, burning about 920 square kilometers of forest!
This figure is not large compared with the New Year fire in Australia, but as long as you know that the fire area in California in 20 19 is only 1025 square kilometers, you know that the fire in 2020 is not generally large, and the California fire season has just begun, and the whole fire will last until 12 years. I don't know to what extent the California fire will expand under the epidemic!
There are several reasons why the fire is particularly serious this year. From 1 to February this year, California was extremely dry, many plants were brown and trees died! These are the driest months in California since meteorological records began. On March 22nd, California Governor gavin Newson declared a state of emergency. There is precipitation in California in spring, but it still failed to revive the previously dry and dead vegetation and clean up these very flammable "fuels" in time!
In addition, the epidemic situation in California this year has also stretched the fire prevention work during the fire season. Therefore, fires broke out in various places in the early autumn, which made the California government somewhat unexpected, and it was really difficult to carry out fire fighting at this time, which is also an important reason for the intensification of the fire!
The fire tornado was surprised, and California meteorologists were dumbfounded.
Tornadoes are not uncommon in the United States. The United States is also a world-famous hometown of tornadoes. From the Mississippi River Plain to Canada, there is also a tornado corridor across the north and south. So the American people are friendly to tornadoes, so tornadoes are not unusual. Surprisingly, there were no tornadoes this year. Of course, this is impossible. Under normal circumstances, there are dozens and hundreds of tornadoes every day from March to May!
However, California is on the west coast of the United States, and it is not a high incidence of tornadoes in the United States. Why is there a tornado in this part of California? And it is a rare "fire tornado". Ben Gelber, a long-term meteorologist at WCMH TV in Columbus, Ohio, explained that the fire tornado in California was caused by many factors:
Violent wind
Uneven terrain
Extreme updraft
Mountain fires in California provide all these conditions, because the hot air rising from the fire will cause the surrounding air to supplement and form strong winds. The mountains in California are not flat, so it is not uncommon for California to have a fire in a fire tornado! However, Ben Gelber said that although it is true in theory that the fire in California formed five fire whirlwinds, which is rare and unbelievable!
Fire tornadoes can also involve unburned combustible gas into the flame, producing a spiral fierce fire, which can spread the fire to areas where tornadoes are difficult to reach at ordinary times, which will help the rapid spread of the fire, which may lead to the explosive spread of fires in California!
Last Saturday afternoon, the National Weather Service issued a warning about some possible "tornadoes caused by fire", which were caused by wildfires in Larsen County, Loyal. The report said that the spread of the fire on Saturday was shocking, and the photos and videos of the fire on Twitter and Facebook were shocking!
In 20 18, a tornado during the California fire in northern California destroyed the community in the city of Reading, about 260 kilometers north of Sacramento, California. The fire killed 8 people and forced about 40,000 people to leave their houses. Of course, it all depends on the complete tornado warning system in the United States, otherwise the casualties may be even greater!
Further reading: tornado warning system in the United States
Because of the special terrain in the United States, tornadoes are very frequent! Due to the towering Rocky Mountains in the western United States, the westerlies passing through it and the warm current in the southern Gulf of Mexico, tornadoes occur every year when warm and humid air flows northward along the plains and forms strong convective weather with cold air, and the number of tornadoes is so large that other countries can't reach the number of tornadoes in the United States in one day. 20 1 1, the most in history, on April 27th, there were 208 tornadoes in Central America!
Therefore, the United States has established a huge tornado early warning system, and its main information source is the weather radar all over the United States. In the high season of tornadoes, it closely monitors its flow direction and provides tornado forecast for residents. Generally, you can give an early warning before a tornado strikes 15 minutes! In areas with high incidence of tornadoes, residents have basements to avoid tornadoes!
Follow-up of California Mountain Fire: Burning Wind and Big Devil Wind
Recently, the ridge of high pressure has controlled the midwest of the United States. The high-pressure "hot dome" is located over great basin, Nevada. Clockwise winds attract it to the north, which may greatly prolong the high temperature season. There is a high temperature of 48 degrees Celsius in northern California, and this high temperature is still spreading to Nevada and Oregon!
The Sierra Nevada between Northern California and Nevada is still about 1500 ~ 2700 meters above sea level. When the cold and wet airflow passes through Nevada and reaches California, the airflow will rise through the mountains, and the moisture will form precipitation. In California, it will descend with the mountain, heat up, and the air flow will be dry and hot, forming a foehn!
foehn
In Southern California, although the terrain is relatively low, the humid airflow from Nevada will cross the Mojave Desert, forming a famous big devil wind, which is as powerful as burning wind, so California, which has been on the edge of the fire in autumn, may be out of control in the future!
According to the US Forest Service, the traffic in the mountain fire area in northern California is very inconvenient and fire engines cannot reach it. Only helicopters and fixed-wing fire extinguishers can be used to put out the fire, but it is obviously impossible to put out the fire in a short time in hot weather, strong winds and dry trees! Many institutions in California have prepared emergency shelters!
So this fire in California, USA, is going to burn Christmas!