Cirrus spissatus cloud
Encyclopedia
Cirrus spissatus clouds are the highest of the main cloud
genera, and may sometimes even occur in the lower stratosphere
. The characteristic features of cirrus cloud
s are fine threads or wisps of ice crystals
, generally white, but appearing grey when dense and seen against the light. No precipitation
at the ground. Frequently exhibits optical phenomena
.
Cirrus spissatus is the dense cirrus that will partly or completely hide the sun
(or Moon
) and which appears dark grey when seen against the light. Although it arises under various circumstances, it is particularly commonly found in the plumes or anvils of cumulonimbus cloud
s.
Precipitation likely within 15 to 25 hours if winds steady from NE E to S, or sooner if winds SE to S. Other winds bring an overcast
sky.
A different variety of cirrus spissatus also forms from phenomena that have nothing to do with cumulonimbus blow-off or dissipating cumulonimbus cells. When dense cirrus is formed by other means than by cumulonimbus blow-off or dissipating cumulonimbus clouds, it will frequently be seen as many dense patches at different levels (cirrus spissatus duplicatus), often mixed with thin cirrus filaments. Another variety, cirrus spissatus intortus, is sometimes described as looking like "entangled sheaves" of cirrus clouds. When viewed toward the sun, the denser patches often have gray bases.
-http://www.clouds-online.com/cloud_atlas/cirrus/cirrus.htm
-http://www.tpub.com/content/aerographer/14269/css/14269_34.htm
Cloud
A cloud is a visible mass of liquid droplets or frozen crystals made of water and/or various chemicals suspended in the atmosphere above the surface of a planetary body. They are also known as aerosols. Clouds in Earth's atmosphere are studied in the cloud physics branch of meteorology...
genera, and may sometimes even occur in the lower stratosphere
Stratosphere
The stratosphere is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. It is stratified in temperature, with warmer layers higher up and cooler layers farther down. This is in contrast to the troposphere near the Earth's surface, which is cooler...
. The characteristic features of cirrus cloud
Cirrus cloud
Cirrus clouds are atmospheric clouds generally characterized by thin, wispy strands, giving them their name from the Latin word cirrus meaning a ringlet or curling lock of hair...
s are fine threads or wisps of ice crystals
Ice crystals
Ice crystals are a small crystalline form of ice including hexagonal columns, hexagonal plates, dendritic crystals, and diamond dust. The highly symmetric shapes are due to depositional growth, namely, direct deposition of water vapour onto the ice crystal...
, generally white, but appearing grey when dense and seen against the light. No precipitation
Precipitation (meteorology)
In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...
at the ground. Frequently exhibits optical phenomena
Optical phenomenon
An optical phenomenon is any observable event that results from the interaction of light and matter. See also list of optical topics and optics. A mirage is an example of an optical phenomenon....
.
Cirrus spissatus is the dense cirrus that will partly or completely hide the sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
(or Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
) and which appears dark grey when seen against the light. Although it arises under various circumstances, it is particularly commonly found in the plumes or anvils of cumulonimbus cloud
Cumulonimbus cloud
Cumulonimbus is a towering vertical cloud that is very tall, dense, and involved in thunderstorms and other inclement weather. Cumulonimbus originates from Latin: Cumulus "Heap" and nimbus "rain". It is a result of atmospheric instability. These clouds can form alone, in clusters, or along a cold...
s.
Precipitation likely within 15 to 25 hours if winds steady from NE E to S, or sooner if winds SE to S. Other winds bring an overcast
Overcast
Overcast or overcast weather, as defined by the World Meteorological Organization, is the meteorological condition of clouds obscuring all of the sky. Overcast, written as "OVC" in the METAR observation, is reported when the cloud cover is observed to equal eight oktas .Sometimes clouds can be...
sky.
A different variety of cirrus spissatus also forms from phenomena that have nothing to do with cumulonimbus blow-off or dissipating cumulonimbus cells. When dense cirrus is formed by other means than by cumulonimbus blow-off or dissipating cumulonimbus clouds, it will frequently be seen as many dense patches at different levels (cirrus spissatus duplicatus), often mixed with thin cirrus filaments. Another variety, cirrus spissatus intortus, is sometimes described as looking like "entangled sheaves" of cirrus clouds. When viewed toward the sun, the denser patches often have gray bases.
Sources
-http://www.theweatherobserver.com/2005/09/21/cirrus-spissatus-ci-spi/-http://www.clouds-online.com/cloud_atlas/cirrus/cirrus.htm
-http://www.tpub.com/content/aerographer/14269/css/14269_34.htm