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Cloud-cover symbols used on weather teleprinters and aviation reports in the US [6] In the early 20th century, it was common for weather maps to be hand drawn. The symbols for cloud cover on these maps, like the modern symbols, were drawn inside the circle marking the position of the weather station making the measurements.
VFR / VMC visibility requirements in the US. In aviation, visual meteorological conditions (VMC) is an aviation flight category in which visual flight rules (VFR) flight is permitted—that is, conditions in which pilots have sufficient visibility to fly the aircraft maintaining visual separation from terrain and other aircraft.
Fractus clouds, also called fractostratus or fractocumulus, [1] are small, ragged cloud fragments that are usually found under an ambient cloud base. They form or have broken off from a larger cloud, and are generally sheared by strong winds , giving them a jagged, shredded appearance.
Thin scattered wispy cloud resembling cirrus through which the planet's surface can be seen. High stratocumuliform Thin scattered wave-cloud resembling cirrocumulus. Low stratocumuliform Wave-cloud resembling stratocumulus, especially as a polar cap cloud over the winter pole which is mostly composed of suspended frozen carbon dioxide. [25] [26]
The height above the ground or water of the base of the lowest layer of cloud below 6000 meters (20,000 feet) covering more than half the sky. [2] United Kingdom The vertical distance from the elevation of an aerodrome to the lowest part of any cloud visible from the aerodrome which is sufficient to obscure more than half of the sky. [3] United ...
Figure 3: Cumulus castellanus.Thes clouds can sometimes be used by glider pilots. Castellanus (clouds made of very narrow columns) are notorious [17] as being unusable by glider pilots. In order for a cloud to have a usable thermal, the updraft column needs to exist under the cloud, in which case the cloud will have a flat base.
Although clouds can exist within a wide range of altitudes, typical cloud cover has a base at approximately 4,000m and extends up to an altitude of about 5,000m. [9] Clouds height can vary depending on latitude; with cloud cover in polar latitudes being slightly lower and in tropical regions the cloud cover may extend up to 8,000m.
Thus, cloud ceiling and flight visibility are the most important variables for safe operations during all phases of flight. [3] The minimum weather conditions for ceiling and visibility for VFR flights are defined in FAR Part 91.155, and vary depending on the type of airspace in which the aircraft is operating, and on whether the flight is ...