Cumulus humilis are

cumuliform Cumulus clouds are clouds which have flat bases and are often described as "puffy", "cotton-like" or "fluffy" in appearance. Their name derives from the Latin ''cumulo-'', meaning ''heap'' or ''pile''. Cumulus clouds are low-level clouds, gener ...

clouds with little vertical extent, common in the summer, that are often referred to as "fair weather

cumulus Cumulus clouds are clouds which have flat bases and are often described as "puffy", "cotton-like" or "fluffy" in appearance. Their name derives from the Latin ''cumulo-'', meaning ''heap'' or ''pile''. Cumulus clouds are low-level clouds, gener ...

". If they develop into

cumulus mediocris Cumulus mediocris is a low to middle level cloud with some vertical extent (Family D1) of the genus cumulus, larger in vertical development than Cumulus humilis. It also may exhibit small protuberances from the top and may show the cauliflower for ...

cumulus congestus Cumulus congestus clouds, also known as towering cumulus, are a form of cumulus that can be based in the low or middle height ranges. They achieve considerable vertical development in areas of deep, moist convection. They are an intermediate stage ...

, 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 expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...

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 the sense of a gradual fall. In dry air, the adiabatic lapse rate is ...

is small. 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 co ...

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 a 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 Glider may refer to: Aircraft and transport Aircraft * Glider (aircraft), heavier-than-air aircraft primarily intended for unpowered flight ** Glider (sailplane), a rigid-winged glider aircraft with an undercarriage, used in the sport of glidin ...

pilots actively seek out the rising air to gain altitude. These clouds may later metamorphose into cumulus clouds when

convection Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convec ...

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. Types of severe weather phenomena vary, depending on the latitude, altitude, topography, and atm ...

in the afternoon or evening. Cumulus humilis clouds are not rain clouds but could precede a storm. Cumulus humilis are sometimes seen beneath

cirrostratus Cirrostratus is a high-level, very thin, generally uniform ''stratiform'' genus-type of cloud. It is made out of ice-crystals, which are pieces of frozen water. It is difficult to detect and it can make halos. These are made when the cloud takes t ...

clouds, which block some of the heat from the sun and thus create an

inversion Inversion or inversions may refer to: Arts * , a French gay magazine (1924/1925) * ''Inversion'' (artwork), a 2005 temporary sculpture in Houston, Texas * Inversion (music), a term with various meanings in music theory and musical set theory * ...

, 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 while horizontal ones d ...

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