Spectacular cloud holes yesterday

An unusually large series of cloud holes developed over Mississippi, Louisiana, Texas, Arkansas, and Alabama yesterday, which were captured by several alert wunderphotographers (see the thumbnail images at the bottom). These cloud holes (also called "dissipation trails" or "distrails") are formed when an aircraft passes through a deck of clouds containing water drops that have cooled below the freezing point of water. The exhaust particles of the aircraft's engines serve as nuclei for the supercooled water drops to freeze on, and the resulting ice crystals fall towards the ground as "fall streaks". Also, engine heat and turbulence along the wing tips mixes moist and dry air, helping create clear holes. It typically takes about 20 minutes for a cloud hole to form after an airplane has passed, so it is not obvious that a aircraft create the holes.


Visible image of the clouds holes of January 29, 2007, as seen by NASA's Terra satellite.

For more detailed information on this event, including animations and upper-air plots, see the University of Wisconsin CIMSS Satellite blog.

I'll have a preview on Wednesday of the upcoming blockbuster climate report scheduled to be released Friday by the U.N. Intergovernmental Panel on Climate Change (IPCC).

Jeff Masters