• Winter Weather Awareness (2)

    From Daryl Stout@1:2320/105 to All on Mon Nov 29 00:01:42 2021
    Public Information Statement
    National Weather Service Little Rock AR
    600 AM CST Mon Nov 29 2021

    ...Winter Weather Awareness Week in Arkansas...

    November 29th through December 3rd is Winter Weather Awareness
    Week in Arkansas. The purpose of this week is to remind people
    what winter weather can bring, and how to deal with
    hazardous winter conditions. Now is the time to prepare
    for the upcoming winter season.

    Today's topic is the outlook for the upcoming winter.

    Overall, winter around here has not exactly been cold in the
    last thirty years. Since the winter of 1990-91, temperatures
    were below average by at least a degree only seven times. Readings
    were above average by a degree or more fifteen times.

    Temperatures last winter were below normal. That is mainly due
    to Arctic air that plunged southward through Arkansas all the way
    to the Gulf Coast in mid-February. Two big storm systems arrived
    from the 14th through the 18th, and deposited more than twenty
    inches of snow in central and southern sections of the state.

    Weather can vary quite a bit from winter to winter, so
    forecasting what will happen is a challenge. The forecast
    usually starts with looking at water temperatures along
    the equator in the Pacific Ocean.

    If the water cools, we trend toward La Nina. If warming occurs,
    then it's El Nino. Both variables have a say in how the weather
    behaves across the country, especially when they become dominant.
    In the coming months, the pendulum will swing toward La Nina,
    which favors warmer and drier conditions across much of the
    southern United States this winter.

    This will be a moderate /versus weak/ La Nina, which not only
    boosts the confidence in the forecast, but also increases the
    chances of extreme weather such as severe storms and tornadoes.
    Such was the case in 1999 and 2008, and eventually 2011 after
    a cold and snowy start to the year.

    While La Nina will likely be the most influential variable that
    governs the weather pattern this winter, there are other factors
    to consider such as the Arctic Oscillation /AO/. In the strongly
    negative phase of the AO, pressure is higher toward the North
    Pole, and this sets up a blocking pattern. Cold air traversing
    Canada is forced to the south, and our temperatures drop.

    In the winter of 2010/2011, there was a long term negative AO,
    and that led to one cold blast after another. On February 9th in
    2011, one to two feet of snow blanketed the Ozark Mountains. Six
    to eight inches of powder accumulated in the Little Rock /Pulaski
    County/ area. It was a top ten snowy winter locally.

    Ten years later, the AO took a similar dive last winter, and that
    led to the already mentioned cold and snow in February.

    Such a lengthy negative AO is rare. Usually, AO phases are of
    short duration /days to weeks/, and are tricky to forecast compared
    to a much more stable El Nino and La Nina /months/.

    Whatever happens, we all know that the weather can be all over
    the place in this part of the world. It can feel like spring in
    January, and it can get really cold. That is an ordinary winter
    locally. Do not expect anything different this time around.

    If more precipitation falls than expected, we will have to
    watch for three things. If we are in the midst of a warm period,
    be wary of severe thunderstorms, which are not unusual. If there
    is a lot of rain, then flooding can become a problem. Finally,
    given a well timed shot of subfreezing air, that is a recipe
    for a big snow or ice storm.


    Additional information on the winter outlook from the Climate
    Prediction Center can be found at:

    https://www.noaa.gov/news-release/us-winter-outlook-drier-warmer- south-wetter-north-with-return-of-la-nina

    * Synchronet * The Thunderbolt BBS - Little Rock, Arkansas
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