Cumulus humilis are

cumuliform Cumulus clouds are clouds that have flat bases and are often described as puffy, cotton-like, or fluffy in appearance. Their name derives from the Latin , meaning "heap" or "pile". Cumulus clouds are low-level clouds, generally less than in a ...

clouds with little vertical extent, common in the summer, that are often referred to as "fair weather cumulus". If they develop into cumulus mediocris or cumulus congestus, thunderstorms could form later in the day. They generally form at lower altitudes (500–3000 m (1,500–10,000 ft)), but in hot countries or over mountainous terrain these clouds can occur at an altitude of up to . They show no significant vertical development, indicating that the

temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...

in the atmosphere above them either drops off very slowly or not at all with altitude; that is, the

environmental lapse rate The lapse rate is the rate at which an atmospheric variable, normally temperature in Earth's atmosphere, falls with altitude. ''Lapse rate'' arises from the word ''lapse'' (in its "becoming less" sense, not its "interruption" sense). In dry air, ...

is small or negative. Cumulus humilis clouds often have little variance in their depths due to their constrained vertical development. Cumulus humilis may be accompanied by other

cloud In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles, suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may ...

types. Air below the cloud base can be quite turbulent due to the

thermal A thermal column (or thermal) is a rising mass of buoyant air, a convective current in the atmosphere, that transfers heat energy vertically. Thermals are created by the uneven heating of Earth's surface from solar radiation, and are an example ...

s that formed the clouds, giving occupants of light aircraft an uncomfortable ride. To avoid

turbulence In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to laminar flow, which occurs when a fluid flows in parallel layers with no disruption between ...

where such clouds are present, pilots may climb above the cloud tops. However, glider pilots actively seek out the rising air to gain altitude. These clouds may later metamorphose into cumulus mediocris and eventually cumulus congestus clouds when

convection Convection is single or Multiphase flow, multiphase fluid flow that occurs Spontaneous process, spontaneously through the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoy ...

is intense enough, though the presence of these types of clouds usually indicates fair weather.

Forecasting

Morning cumulus humilis clouds are signs of an unstable atmosphere. Larger clouds or possibly thunderstorms could form throughout the day to cause bad or

severe weather Severe weather is any dangerous meteorological phenomenon with the potential to cause damage, serious social disruption, or loss of human life. These vary depending on the latitude, altitude, topography, and atmospheric conditions. High ...

in the afternoon or evening. Cumulus humilis clouds are not rain clouds but could precede a storm. Cumulus humilis are sometimes seen beneath cirrostratus clouds, which block some of the heat from the sun and thus create an inversion, causing any cumuliform clouds to flatten and become cumulus humilis. In this case, a warm front could be approaching and rain is possible for the next 12 to 24 hours. When cumulus humilis appear in a clear sky, they are an indicator of pleasant weather for the next several hours.

Formation

Cumulus humilis clouds are formed by rising warm air or

s with ascending

air current In meteorology, air currents are concentrated areas of winds. They are mainly due to differences in atmospheric pressure or temperature. They are divided into horizontal and vertical currents; both are present at Mesoscale meteorology, mesoscale w ...

s of 2–5 m/s (7–17 ft/s). These clouds are usually very small convective clouds and usually form after a thermal reaches the condensation level. They can develop into cumulus mediocris clouds but most often dissipate a few minutes after formation.

References

External links

Cumulus humilis
{{Cloud types Cumulus

Forecasting

Formation

See also

References

External links