• Thunderstorms Was: Wegman

    From Daryl Stout@454:1/33 to NANCY BACKUS on Wed Jul 31 15:55:00 2019
    Nancy,

    More often, we just get snow.... just like we often just get rain
    (even very heavy rain) without any thunder/lightning.... :)
    True. Maybe when Daryl gets back he'll explain it to us.

    I don't think I've seen him jump in on this yet...

    Maybe we should look for Jim Cantore. <G>

    Seriously, if you have enough lift and instability, along with charged particles in the cloud, you're going to get lightning and thunder. The
    type of precipitation is determined by the air temperatures aloft, at
    the mid levels, and at the ground level.

    1) Below freezing at the surface, midlevels, and aloft: SNOW -- the
    closer to freezing it is, may determine the difference between a heavy,
    wet snow, and a dry, powdery snow.

    I forget which one is better for making snow cream and a snowman with
    (never mind Calvin and Hobbes with his anatomically correct creations
    <G>). The dry powdery snow is best for skiing, but in the mountain
    areas, a large amount of such could lead to deadly avalanches.

    2) Below freezing at the surface (shallow layer), above freezing at the midlevels, and below freezing aloft: FREEZING RAIN or FREEZING DRIZZLE.

    This is the most dangerous, as it puts a GLAZE on EVERYTHING -- trees,
    power lines, bridges/overpasses, sidewalks, etc. Widespread downed
    trees, power lines, and power outages result...sometimes for several
    weeks. If more than 1/4 inch of ice accumulation is forecast, it's known
    as an "ice storm". Back to back ice storms in Arkansas in 2000, had
    portions of north Arkansas in the dark for 6 weeks!!

    3) Below freezing at the surface (deep layer), above freezing at the
    mid levels, and below freezing aloft: SLEET (also known as ice pellets).
    This isn't as dangerous as freezing rain, but it can still make things slippery.

    4) Above freezing at the surface, and either above or below freezing at
    the midlevels and aloft: RAIN

    What you mentioned is known as "VIRGA"...where the precipitation
    evaporates before reaching the ground. You can still get the lightning
    and thunder, but there is dry air at the low levels, and at the base of
    the storm, that the precipitation dissipates on the way down. Once the
    lower levels moisten up, then precipitation reaches the ground. Doppler
    Radar may indicate it's raining, but surface observations note that it's
    not.

    Now, the first stage of a storm is known as the cumulus stage.
    Moisture rises and condenses into clouds...basically, the entire storm
    is composed of updrafts. Inside the cloud, particles of dust, dirt,
    etc., known as condensation nuclei, attract the water droplets, which
    bump into each other, and grow larger. This is known as coalesence.

    Over time, the weight of the water droplets in the cloud become too
    heavy to be supported and held aloft by the updrafts, so they fall,
    creating a downdraft. Some thunderstorms can have as much as 500,000
    tons of water or more!!

    Lightning is basically a massive discharge of static electricity. In a thunderstorm, negative electrical charges buildup from the condensation
    nuclei bumping into each other. These negative charges, usually at the
    base of the storm, induce positive charges in the higher levels of the
    storm, and on the ground for several miles around the storm. Finally,
    the build up of charges becomes so great, that the air can not insulate
    them from one another, and you get lightning.

    All lightning can be deadly, and you never know where it'll strike
    next. But, you have lightning within the thundercloud...lightning from
    cloud to cloud (from one storm to another)...lightning from cloud to air
    (a bolt from the blue)...and cloud to ground. Some thunderstorms can be prolific lightning producers. It only takes one lightning strike to
    cause damage, injury, or death. I'm a 2 time lightning strike survivor
    myself, and have nervous system as a result. The strikes were indirect,
    but I still got the shock...however, I carry no electrical charge, and
    can be handled safely. <G>

    Each lightning bolt:

    1) Is 50,000 degrees Fahrenheit (5 times hotter than the sun's surface).

    2) Has 3 million volts and 300,000 amps of electricity (not even 1 amp
    of electricity will kill you).

    3) Is as wide as your thumb, but can be 5 miles long.

    4) Can strike from 20 to 200 miles from the parent thunderstorm.

    The thunder is the rapid expansion of the air in the lightning
    channel. If it sounds like a sharp clap, boom, or explosion, the strike
    was likely very close to you. If it sounds like a low rumble, the
    storm is a few miles away. Regardless, if you hear thunder, you are
    close enough to be struck by lightning...and if you're outdoors, you
    need to STOP all activities IMMEDIATELY!! Lightning does NOT need to
    strike twice!!

    Tbe best way to remember it is "The 30-30 Rule". The first part means
    that if less than 30 seconds elapses after you see lightning before you
    hear thunder, you are close enough to be struck by lighnting. The second
    part means that if 30 minutes has elapsed since you last heard thunder,
    you can resume all normal activities.

    Back to the thunderstorm itself, at this point, the storm is mature.
    Heavy rain falls from the storm, causing urban and flash flooding;
    especially if several thunderstorms move over the same area (known as "training", like a train repeatedly going down the tracks).

    Strong winds fan out at the base of the storm, and if above 58 mph
    (the criteria to class a storm as severe), it's known as downburst or
    straight line winds, which can cause damage similar to an EF-0 or EF-1
    tornado.

    There's also lightning (some storms have very little, but others seem
    to have an unending supply).

    If the storm is intense enough with strong updrafts, rain droplets are
    swept to the upper reaches of the storm, where temperatures are below
    freezing. These super cooled water droplets freeze, and form hailstones. Depending on how strong the updraft is, the hailstone may make several
    trips up and down the storm, before it becomes too heavy for the updraft
    to support, and it rockets to the ground at 100 mph. Hailstones can
    range from 1/4 inch diameter, to the size of a grapefruit (4 1/2 inches
    in diameter). At 1 inch in diameter, it can hurt or kill you, and that's
    the criteria for a severe thunderstorm. The largest hailstone ever
    recorded was in South Dakota or Nebraska, at nearly 9 inches in
    diameter!! If you're in an areas with large hail, you're in or near an
    area where tornado development may occur.

    Speaking of which, if the storm is "surface based", and there's a
    turning of the winds with height, the storm may rotate. At this point,
    it's known as a "supercell"...and it likely to spawn tornadoes. This
    element is known as wind shear...such as southeast winds at the surface, southwest winds at the mid levels, and west winds at the upper
    levels...the wind is turning with height. If the shear is extremely
    strong, strong to violent, long track tornadoes, may develop. In the
    case, the tornado can be a mile wide, if not bigger...and be on the
    ground for hundreds of miles.

    Finally, the updraft weakens. The downdraft takes over, and the
    thunderstorm collapses in on itself. This is when you get intense
    flooding rain, and strong downburst winds. However, the cool air left by
    the storm may create an outflow boundary, where new thunderstorm
    activity may form later on.

    And, that's Meteorology 101 for today. :)

    Daryl

    ===
    þ OLX 1.53 þ We all have to go sometime -- where's the toilet??
    --- SBBSecho 3.07-Win32
    * Origin: The Thunderbolt BBS - tbolt.synchro.net (454:1/33)
  • From Nancy Backus@454:1/452 to Daryl Stout on Mon Aug 5 15:50:34 2019
    Quoting Daryl Stout to NANCY BACKUS on 31-Jul-2019 15:55 <=-

    More often, we just get snow.... just like we often just get rain
    (even very heavy rain) without any thunder/lightning.... :)
    True. Maybe when Daryl gets back he'll explain it to us.
    I don't think I've seen him jump in on this yet...

    Maybe we should look for Jim Cantore. <G>
    Seriously, if you have enough lift and instability, along with
    charged particles in the cloud, you're going to get lightning and
    thunder. The type of precipitation is determined by the air
    temperatures aloft, at the mid levels, and at the ground level.

    Well... <G> When you do jump in, you do with a vengeance...! <G>
    Seriously, it is quite the treatise... although I snipped out quite a
    lot for the reply, I saved the whole thing to its own file to refer to
    in times to come.... :)

    I forget which one is better for making snow cream and a snowman
    with (never mind Calvin and Hobbes with his anatomically correct
    creations <G>). The dry powdery snow is best for skiing, but in the mountain areas, a large amount of such could lead to deadly avalanches.

    For snowballs and snowmen, one wants a snow with some moisture, so that
    it packs nicely, but not so wet that it turns to ice when one compacts
    it....

    What you mentioned is known as "VIRGA"...where the precipitation evaporates before reaching the ground. You can still get the lightning
    and thunder, but there is dry air at the low levels, and at the base
    of the storm, that the precipitation dissipates on the way down. Once
    the lower levels moisten up, then precipitation reaches the ground. Doppler Radar may indicate it's raining, but surface observations note that it's not.

    Actually, what I was talking about wasn't the lack of precipitation, but
    the lack of thunder and lightning.... Many times there's just rain, even
    heavy rain, and none of the electric stuff.... And only rarely does one
    get thunder and lightning with snow.... I have on rare occasion,
    though, also experienced the virga...

    Now, the first stage of a storm is known as the cumulus stage.
    Moisture rises and condenses into clouds...basically, the entire storm
    is composed of updrafts. Inside the cloud, particles of dust, dirt,
    etc., known as condensation nuclei, attract the water droplets, which
    bump into each other, and grow larger. This is known as coalesence.
    Over time, the weight of the water droplets in the cloud become too
    heavy to be supported and held aloft by the updrafts, so they fall, creating a downdraft.

    That essentially is how I understood rain (and snow) storms to form...
    Barry was talking about an experiment with oil that he thought could be analogous... but that did require some difference in potential as well
    as just the coalesence....

    ttyl neb

    ... Seen it all, done it all, can't remember most of it.

    --- EzyBlueWave V3.00 01FB001F
    * Origin: Tiny's BBS - http://www.tinysbbs.com (454:1/452)