Cb arcus

A panoramic view of a supercell cloud formed through back-building with a well-defined shelf cloud known as cumulonimbus arcus praecipitatio with very heavy rain particularly on the cloud’s left side. These clouds are the leading edge of a gust front. It forms when a thunderstorm with heavy rain begins to discharge cold air towards the ground known as a downdraft. As the cold air is heavier than warm air, it begins to flow away at ground-level from the storm and hence it pushes the warmer air upwards. This warm, moist air is then forced to ride along the leading edge of the thunderstorm as the thunderstorm continued to build towards the area condensing into a sharp-looking shelf cloud as it continues to rise above the outflow boundary. A detailed explanation of this phenomena could be found in this link – http://thevane.gawker.com/shelf-clouds-one-of-natures-most-alarming-and-awesome-1538431006. The first thumbnail is the beginnings of the formation of a shelf cloud whilst the second thumbnail shows the shelf cloud developing as it continues to approach the area. The third thumbnail is a single shot photo potentially showing 3 shelf clouds heading towards western Malta as the supercell becomes full of sinking cold air to the extent that it had split up. In fact, temperature suddenly fell from a MAX of 22C to 13C during the storm.

The thunderstorm itself was caused by an upper-level trough, third thumbnail, bringing cold air at upper-levels which contrasted heavily with the warm, moist airmass at the surface. The weather sounding on the fourth thumbnail depicts this wind shear though the air was only slightly unstable, also notice the very dry mid-levels enabling the strong downdraft to form the shelf cloud. The fifth thumbnail chart shows a small warm front to the west of Malta turning out to be very important for huge temperature contrast inside the air column, though the air became much colder for many hours after the storm. The sixth and seventh thumbnails are the visible satellite and lightning images showing the storm characteristics that hit our Islands. Following this weather event, a cold pool and an overcast sky consisting of nimbostratus clouds persisted for the rest of that day giving hours of continuous moderate rain. In fact, more photos and weather images are shown here.

Further photos and a small video of the described weather phenomena are available upon request on the website email.

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