Look In the Sky, It's a Circumhorizon Arc - NBC 5 Dallas-Fort Worth

Look In the Sky, It's a Circumhorizon Arc



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    Daria Moore
    Viewers sent in more than a dozen photos of the circumhorizon arc seen over North Texas on April 16, 2009.

    A weather phenomenon over the Dallas-Fort Worth area Thursday afternoon had North Texans grabbing their cameras and snapping photos.

    Some NBCDFW users who sent in photos referred to the oddity as a "sun dog" but meteorologist David Finfrock says not so fast -- it's really a circumhorizon arc.

    You can find a very detailed explanation of a circumhorizon arc and photos from Atmospheric Optics as well as the National Weather Service. Or, click "watch video" on the left to hear an explanation from Finfrock.

    The simple explanation is that it's a halo or optical phenomenon caused by the refraction of sunlight through thick, flat, horizontal ice crystals in cirrus clouds. The result is just like when sunlight hits a prism separating the light into a myriad of colors.