Explanation:
What kind of cloud is this?
A roll cloud.
These rare long clouds may form near advancing cold fronts.
In particular, a downdraft from an advancing storm front can cause moist warm air to rise, cool below its dew point, and so form
a cloud.
When this happens uniformly along an extended front, a
roll cloud may form.
Roll clouds
may actually have air circulating along the long horizontal axis of the cloud.
A roll cloud is not thought to be able to morph into a
tornado.
Unlike a similar
shelf cloud,
a roll cloud, a type of
Arcus cloud,
is completely detached from their parent
cumulonimbus cloud.
Pictured
above, a
roll cloud extends far into the distance in 2009 January
above Las Olas Beach in
Maldonado,
Uruguay.
Note: An
APOD editor will review astronomy images of 2009,
hosted by the Amateur Astronomers Association of New York on Friday,
January 8 at the American Museum of Natural History, NYC.
digg_url = 'http://apod.nasa.gov/apod/ap100105.html'; digg_skin = 'compact';
