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    Unusual Start to Tornado Season

    By by Molly Cochran, AccuWeather.com Staff Writer
    April 29, 2013, 5:45:34 AM EDT

    Tornado season has been off to a slow start compared to the amped-up season last year.

    The daily count and running annual trend of tornadoes in the United States has been significantly lower this season compared to last. According to NOAA, there were 592 tornadoes between Jan. 1 and April 25. This season during the same period, the U.S. has only endured 226 tornadoes. The average is 492.


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    AccuWeather.com Expert Senior Meteorologist Henry Margusity said that there has been a decrease in tornadoes this year compared to last.

    "The tornado season is below normal in regards to tornadoes since May 2012," Margusity said.

    Last year, tornadoes were active during the first half of the season from Jan. 1 through April 25. The decrease in tornadoes this season can be attributed to a much colder weather pattern, according to Margusity.

    "Last year we had gangbusters to start out the year, and this year we haven't had any," he said.

    Warmer weather has been delayed this season compared to last. Cold dry air has been reached farther south.

    "Last January was very warm. As the warmth continued, there were more outbreaks," he said.

    AccuWeather.com Expert Senior Meteorologist Dan Kottlowski said the cold pattern that has occupied the United States is due to a major change in the upper levels of the atmosphere above the Arctic Circle. A pattern change that occurred in February allowed cold air from Canada to dip down into southern states. This pattern occupied much of the U.S. into April.

    With cold air sticking around for a longer period of time, conditions were not favorable for tornado formation, Margusity said.

    Harold Brooks, senior scientist at the National Severe Storms Laboratory in Oklahoma, also agrees that cold weather has a played a significant role in deterring tornadoes from forming.

    "Final counts in March will be close to the lowest mark on record," he said.

    This tornado season is below normal, and Brooks said it is in the lower 10 percent of tornado activity over the past 60 years.


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    The reason that we witnessed more tornadoes last year is because January through March was very warm compared to this year.

    This year, cold fronts moving into the Gulf of Mexico have spread dry air across the Southern states, according to Margusity. Due to the cold, dry air that was dipping so far south, sea temperatures in the Gulf of Mexico were not that warm yet. With sea temperatures not rising as fast as last year and a colder weather pattern in place, humid, moist air from the Gulf, a necessity for tornado development, has not been available. However, Kottlowski said temperatures are starting to rise.

    With cold air lasting into the latter part of spring and the lack of deep tropical moisture, this has contributed to the lack of tornado formation.

    "The atmosphere is not unstable," Kottlowski said.

    Margusity said that this is just a weather pattern we are in. Weather conditions are not favorable for producing tornadoes. The tornado season in 2004 was similar to this one; however, Margusity pointed out that we are not in a La Nina or El Nino that would be driving this colder weather pattern.

    However, AccuWeather meteorologists think that the months of May and June could be active when it comes to tornadoes.

    "Our fear is that there will be more severe weather in June," Kottlowski said.

    According to Kottlowski, severe weather will occur in May, but a better question to ask is how frequently tornadoes will occur.

    Brooks said that even though we got off to a slow start, there is no way to really tell what the rest of the season will be like.

    "This means nothing for May. Anything that happens between Jan. 1 to April virtually tells us nothing about how the rest of the season will be," he said.

    As far as predicting when and where tornadoes will form, meteorologists are still researching.

    Predicting exactly where a tornado will strike is hard to do because tornadoes are unpredictable. However, Margusity said that eventually meteorologists will be able to predict 6-12 hours in advance which areas are likely to have tornadoes and the severity.

    Brooks also expressed the challenge of predicting tornadoes and hopes that by 10 years we will have more technology to predict when and where tornadoes will occur.

    "Maybe 10 years, between five and 10 years from now depending on time of year and what type of system we are looking for. It is a hard research problem," he said.

    The decline in tornadoes compared to last year is not a bad thing.

    Margusity said that with a lack of tornadoes, there is no massive destruction, and people are not getting hurt or killed from severe weather.

    For all of your up-to-date and local severe weather, be sure to check out AccuWeather.com Severe Weather Center.

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