Estranhas formações de nuvens (video)


23 Jan 2007
Espectacular visão sem dúvida.
Em princípio terão atravessado um "Undular Bore":

Undular bore over the Gulf of Mexico


A spectacular gravity wave train (or “undular bore“) was captured on a sequence of GOES-12 visible images (above) as it propagated southward across the northwestern Gulf of Mexico on 15 March 2008; as many as 16 separate cloud bands were evident (denoting individual wave crests along the wave train). Because of severe convection over the southeastern US on that day, the GOES-12 satellite had been placed into Rapid Scan Operations (RSO) mode, allowing images as frequently as every 5 minutes. Note how the patches of marine stratus cloud that were moving northeastward (ahead of the gravity wave train) are seen to dissipate very quickly as they encountered the wave. These undular bore features occur with some regularity over that particular part of the Gulf of Mexico — similar events were noted back in April 2007 and March 1998.

Undular bore
Undular bores are usually formed when two air masses of different temperatures collide. When a storm (typically a thunderstorm) approaches a layer of cold, stable air, it creates a disturbance in the atmosphere producing a wave like motion. Although the undular bore waves appear as bands of clouds across the sky, they are transverse waves (a.k.a. gravity waves), and are propelled by the transfer of energy from an oncoming storm. The ripple like appearance of this wave is described as the disturbance in the water when a pebble is dropped into a pond or when a moving boat creates waves in the surrounding water. The object displaces the water or medium the wave is travelling through and the medium moves in an upward motion. However, because of gravity, the water or medium is pulled back down and the repetition of this cycle creates the transverse wave motion.

The undular bore's period can measure 5 miles peak to peak and can travel 10 to 50 mph. The medium it travels through is the atmosphere. There are several varying types of ‘‘bores’’ in different layers of the atmosphere, such as the mesospheric bore which occurs in the mesosphere.

Undular bores are believed to be catalysts for thunderstorms. Although a thunderstorm helps create an undular bore, an undular bore can in turn intensify a thunderstorm because it further disturbs the atmosphere.