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Upper midwest tornados

Discussion in 'Environmental Discussion' started by bwilson4web, Nov 19, 2013.

  1. bwilson4web

    bwilson4web BMW i3 and Model 3

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    An impressive series, the numbers and area reminds me of the 2011 April tornados. Like North Alabama, I'm sure the power grid has a lot of cuts. But unlike our storms, theirs is being followed by a lot of freezing temperatures.

    Now I'm OK with shear being part of the recipe for tornados and understand some climate models report less shear as the earth warms up. This remains an area of some interest as it isn't clear how having more energy in the atmosphere causes winds to becalmed. But perhaps there is some other source of thermodynamic energy that drives these storms. It isn't as if these are just variations of dry air, dust devils.

    I remember looking at the satellite images of the warm, moist air, coming from the Pacific over southern Mexico, then passing over the Gulf of Mexico, and headed Northeast along the frontal line. Not an unfamiliar pattern but it raises an interesting thought.

    Can we see thermal effects on sea surface temperatures before and after a major weather event? The recent typhoon and these tornado outbreaks release a significant amount of energy. So where did it come from and is it small enough to be detected?

    Bob Wilson
     
    #1 bwilson4web, Nov 19, 2013
  2. wxman

    wxman Active Member

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    Hi Bob,

    That isn't necessarily what's happening. TORNADOES require shear, but you still can have incredibly strong "downbursts" from pulse (as opposed to supercell) thunderstorms. Downburst wind speeds have been measured in the EF-3 tornado strength category (see Downbursts - Severe Weather Awareness).

    So you still can have very strong thunderstorms in weakly sheared environments, just not tornadoes (typically).



    I've seen thermal images of SSTs shortly after a strong hurricane moved through, and temps were clearly lower alomh its path compared to surrounding sea surface (unaffected by the hurricane). It's my understanding that this is the result of turbulent upwelling.
     
    #2 wxman, Nov 19, 2013
  3. Trollbait

    Trollbait It's a D&D thing

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    Ocean currents are driven by basic convection. The greater the difference in temperature between the hot area and the cold one, the stronger the current. A similar mechanism is at play for local winds, and likely is part of the driving force for wind currents on the global level.

    The temperature delta between the poles and equator is predicted to drop with global warming. This will slow down the major ocean currents, and should do so for winds that rely on it for their energy.
     
    #3 Trollbait, Nov 19, 2013
  4. tochatihu

    tochatihu Senior Member

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    Wxman "thermal images of SSTs"

    NOAA AOML TCHP seems the best source of such things; global and promptly updated.

    The heat capacity of air is about 1/1000 of water (volume basis) so while there should be a thermal change after any major rain event, it would be diluted out very rapidly I'd think.
     
    #4 tochatihu, Nov 19, 2013
    bwilson4web likes this.
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