Cloud suck is a phenomenon commonly known in paragliding

Paragliding

Paragliding is the recreational and competitive adventure sport of flying paragliders: lightweight, free-flying, foot-launched glider aircraft with no rigid primary structure...

 and hang gliding

Hang gliding

Hang gliding is an air sport in which a pilot flies a light and unmotorized foot-launchable aircraft called a hang glider ....

 where pilots experience significant lift

Lift (soaring)

Gliding flight is heavier-than-air flight without the use of thrust. It is employed by gliding animals and by aircraft such as gliders. The most common human application of gliding flight is in sport and recreation using aircraft designed for this purpose...

 due to a thermal

Thermal

A thermal column is a column of rising air in the lower altitudes of the Earth's atmosphere. Thermals are created by the uneven heating of the Earth's surface from solar radiation, and are an example of convection. The sun warms the ground, which in turn warms the air directly above it...

 under the base of cumulus

Cumulus cloud

Cumulus clouds are a type of cloud with noticeable vertical development and clearly defined edges. Cumulus means "heap" or "pile" in Latin. They are often described as "puffy" or "cotton-like" in appearance. Cumulus clouds may appear alone, in lines, or in clusters...

 clouds, especially towering cumulus

Towering cumulus

Towering cumulus clouds can be based in the low or middle height ranges and achieve considerable vertical development in areas of deep, moist convection. They are an intermediate stage between cumulus mediocris and cumulonimbus...

 and cumulonimbus. The vertical extent of a cumulus cloud is a strong indicator of the level of lift beneath it, and the potential for cloud suck.
Cloud suck commonly occurs in low pressure weather

Low pressure area

A low-pressure area, or "low", is a region where the atmospheric pressure at sea level is below that of surrounding locations. Low-pressure systems form under areas of wind divergence which occur in upper levels of the troposphere. The formation process of a low-pressure area is known as...

 and in humid conditions.

Cloud suck is typically associated with an increase in thermal updraft velocity near cloud base

Cloud base

This article refers to meteorology. For the airborne base of the TV series Captain Scarlet and the Mysterons, see Cloudbase.The cloud base is the lowest altitude of the visible portion of the cloud...

. As a parcel of air lifted in a thermal rises, it also cools, and water vapor will eventually condense to form a cloud if the parcel rises above the lifted condensation level

Lifted condensation level

The lifted condensation level or lifting condensation level is formally defined as the height at which the relative humidity of an air parcel will reach 100% when it is cooled by dry adiabatic lifting...

. As the water vapor condenses, it releases its latent heat of vaporization, thereby increasing the buoyancy of the parcel.
The updraft is amplified by this latent heat release.

Paraglider pilots have reported being unable to descend in strong cloud suck, even after bringing their canopies into full stall, which would normally result in a rapid vertical descent. Cloud suck is especially dangerous for paraglider pilots, whose maximum speed is less than 30 knots, because the updrafts can exceed their ability to get away.

On 14 February 2007 while practicing for a paragliding contest in Australia, Polish-born
German team pilot Ewa Wiśnierska-Cieślewicz was sucked into a cumulonimbus cloud, climbing at up to 20 meters per second (4,000 feet per minute)
to an altitude of 9,946 meters (32,600 feet). She lost consciousness due to hypoxia

Hypoxia (medical)

Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...

, but regained consciousness after 30 minutes to an hour, and landed still covered in ice after a three and a half hour flight.

Chinese paraglider pilot He Zhongpin died after he was sucked into the same storm system and struck by lightning at 5900 meters (19,000 feet). His body was found the next day 15 km (9.3 mi) from his last known position prior to entering the cloud.

Compared with hang-gliders and paragliders, sailplanes

Glider (sailplane)

A glider or sailplane is a type of glider aircraft used in the sport of gliding. Some gliders, known as motor gliders are used for gliding and soaring as well, but have engines which can, in some cases, be used for take-off or for extending a flight...

 have much higher top speeds (often over 250 km/h), they could easily escape powerful cumulo-nimbus clouds by flying away quickly or by using their powerful air brakes

Air brake (aircraft)

In aeronautics, air brakes or speedbrakes are a type of flight control surface used on an aircraft to increase drag or increase the angle of approach during landing....

. Furthermore, since lee waves are nowadays used by glider pilots to gain great heights instead of thunderstorms, occurrences of unplanned ascents are rare.

Cloud suck is also a concern for powered aircraft, but usually not a lethal hazard, except in extreme weather situations. The USS Shenandoah

USS Shenandoah (ZR-1)

USS Shenandoah was the first of four United States Navy rigid airships. It was built in 1922-1923 at Lakehurst Naval Air Station, and first flew in September 1923. It developed the Navy's experience with rigid airships, even making the first crossing of North America by airship...

, the first rigid airship

Airship

An airship or dirigible is a type of aerostat or "lighter-than-air aircraft" that can be steered and propelled through the air using rudders and propellers or other thrust mechanisms...

 built in the United States, and the first in the world to be inflated with helium

Helium

Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...

, was lost in a cloud suck accident associated with a squall line

Squall line

A squall line is a line of severe thunderstorms that can form along or ahead of a cold front. In the early 20th century, the term was used as a synonym for cold front. It contains heavy precipitation, hail, frequent lightning, strong straight-line winds, and possibly tornadoes and waterspouts....

. At about 6:00 am on the morning of 3 September 1925, near Ava

Ava, Ohio

Ava is an unincorporated community in northwestern Noble Township, Noble County, Ohio, United States. Although it is unincorporated, it has a post office, with the ZIP code of 43711. Also located in Ava is a small museum dedicated to the nearby crash of the airship USS Shenandoah in...

 in northern Noble County

Noble County, Ohio

Noble County is a county located in the state of Ohio. As of the 2010 census, the population was 14,645. Its county seat is Caldwell. Noble County is named for Rep. Warren P. Noble of the Ohio House of Representatives, who was an early settler there.-History:...

, Ohio

Ohio

Ohio is a Midwestern state in the United States. The 34th largest state by area in the U.S.,it is the 7th‑most populous with over 11.5 million residents, containing several major American cities and seven metropolitan areas with populations of 500,000 or more.The state's capital is Columbus...

, the Shenandoah was suddenly caught in a violent updraft, while at an altitude of 2,100 feet rising at the rate of a meter a second. At about 6,200 feet the ascent was checked, but the ship began to descend. When halfway to the ground it was hit by another updraft and began to rise rapidly at an even faster rate. Ultimately the keel snapped, and the ship broke up while still more than a mile above the ground. Shenandoah's commanding officer and 13 other officers and men were killed. Twenty-nine members of the crew survived the break-up, although some received serious injuries.

External links

• How To Avoid Cloud Suck article by USHPA
  USHPA
  The United States Hang Gliding and Paragliding Association is a non-profit organization supporting foot-launched soaring flight in the United States. It began in 1971 as the Southern California Hang Gliding Association and became national in scope by the mid-1970s. When paragliding became popular...