Thunderstorms and tornadoes

Cumulonimbus is a deep, vertically developed cloud produced by strong convection. Its large vertical extent allows intense updrafts, heavy rain, hail, lightning, and thunder to occur within the same cloud system. Stratus and cirrus clouds do not normally produce thunderstorms, making option C correct.

A lightning discharge heats the surrounding air extremely rapidly, causing a sudden expansion that produces thunder. The flash and the sound are generated almost together, but light travels through the atmosphere far faster than sound. Consequently, the flash reaches an observer first, while the thunder arrives later; the delay increases with distance from the lightning channel. Thus, option D is correct.

The mature stage is the most active stage of a thunderstorm. Strong updrafts build the cloud and carry moisture upward, while downdrafts bring rain-cooled air downward. Their simultaneous presence produces heavy rain, lightning, thunder, hail, and strong gusts, so option B is correct.

During the day, solar radiation warms the land surface, which heats the air immediately above it. Warm air rises, and if sufficient moisture and instability are present, the rising motion intensifies into deep convection and thunderstorms. The surface usually reaches its highest temperature in the afternoon, making A correct.

Humidity refers to the amount of water vapour present in the air. When humidity is high, sweat evaporates less efficiently, making the air feel muggy or humid. Abundant moisture can also provide fuel for convection and cloud growth when warmth and instability are present, so option B is correct.

The initial stage of a thunderstorm is called the cumulus stage. During this phase, warm, moist air rises strongly through updrafts and the cloud grows vertically. The cloud is still developing, so upward motion dominates and rainfall is usually limited. It is followed by the mature stage and then the dissipating stage.

During lightning, the safest choice among these options is to enter a substantial, enclosed building and remain away from windows, plumbing, and electrical equipment. Open fields, isolated trees, and water increase exposure because lightning can strike elevated or conductive objects. A vehicle with a hard metal roof can also provide protection if a building is unavailable.

During a tornado warning, people should move to a basement or a small interior room on the lowest floor, away from windows. Upper floors and rooms with large openings can be more exposed to extreme winds and flying debris. The shelter should be structurally strong, and occupants should protect their heads and follow official instructions.

The base of a storm cloud can look dark because the cloud is deep and dense, containing many water droplets, ice particles, and sometimes rain. These materials scatter and absorb a large part of incoming sunlight, so much less light reaches the underside. The darkness does not mean that the cloud emits black light.

Temperature generally decreases with altitude in the troposphere. Powerful thunderstorm updrafts carry water droplets upward into very cold levels, where droplets may freeze or collide with ice crystals and hail particles. Thus, ice can accumulate in the upper cloud even though liquid water exists in warmer lower portions.

When warm, moist air rises, it expands and cools. Once it reaches its dew point, water vapour begins changing into tiny liquid droplets or ice crystals around condensation nuclei. This condensation forms clouds and releases latent heat, which can further support upward motion in a developing thunderstorm.

A thunderstorm is considered a local or mesoscale weather event because its strongest effects are usually concentrated over a relatively limited area and last for a short period, often less than a few hours. It may produce intense rain, lightning, hail, and gusts locally without affecting an entire country or the whole planet.

A cloud that grows strongly upward indicates vigorous convection. Warm, buoyant air is rising through the atmosphere and carrying moisture to higher, colder levels, where condensation and freezing enlarge the cloud. Tall vertical development is therefore a sign of strong updrafts and instability, both of which support thunderstorm formation.

Strong thunderstorms can sharply reduce visibility because heavy rain scatters and absorbs light, while hail and dust add more particles between the observer and distant objects. Gust fronts may lift additional dust from the ground. The result is a shorter visible distance and more difficult travel, especially for drivers and aircraft.

An electric discharge that travels between a cloud and the ground is called a cloud-to-ground lightning strike. It occurs when charge separation within the storm creates a sufficiently strong electrical potential difference. Lightning is the visible electrical flash; thunder is the sound produced when the discharge rapidly heats and expands surrounding air.

A lightning channel heats the surrounding air extremely rapidly to a very high temperature. The heated air expands explosively and creates a shock wave, which travels outward as sound. That sound is heard as thunder. The delay between seeing lightning and hearing thunder occurs because light reaches us much faster than sound.

A flash flood can occur when intense thunderstorm rainfall falls faster than soil, drains, streams, and channels can absorb or carry it away. Water levels then rise rapidly, often within minutes or a few hours. Steep terrain, urban surfaces, and blocked drainage can make the flooding more severe and dangerous.

A downdraft is a current of air moving downward inside or beneath a thunderstorm. Rain and melting ice cool the surrounding air, making it denser. Gravity then pulls this air downward, and when it reaches the ground it can produce strong outflow winds.

Standing under a tree during a thunderstorm is dangerous because a tall, isolated tree can be struck by lightning. The electrical current may travel through the trunk, branches, or wet ground and can injure people nearby. A safer action is to enter a substantial enclosed building or a hard-topped vehicle, while avoiding contact with electrical equipment and plumbing.

During a thunderstorm, remaining inside a strong, enclosed building is safer than being outdoors. People should stay away from windows because strong winds or flying debris may break the glass, and they should avoid using or touching electrical appliances connected to outlets. Going to the roof, an open field, or a tree increases exposure to lightning and wind.

When a tornado warning is issued, the safest location is usually a basement or a small interior room on the lowest available floor of a strong building. Windows and outside walls should be avoided because violent winds can break glass and carry debris. People should protect their heads and follow official emergency instructions until the danger has passed.

Thunderstorms are localized, short-duration weather systems generated by strong convection. Warm moist air rises, condenses into a cumulonimbus cloud, and releases latent heat that can strengthen the updraft. Such storms commonly produce lightning and thunder, heavy rain, hail, squalls, or damaging gusts, so the remaining statements contradict their defining features.

Thunderstorms can produce intense rainfall that forms a dense curtain in front of an observer. Strong gusts may lift dust, soil, leaves, and debris, adding further scattering and obstruction. These combined effects can reduce visibility abruptly and create serious hazards for transport and outdoor activity.

A thunderstorm can release a large amount of rain over a small area in a short period. If rainfall exceeds the capacity of soil, drains, streams, and local channels to absorb or carry water, runoff accumulates rapidly and produces flash flooding, especially in urban areas or steep valleys.

Because light reaches an observer much sooner than sound, the interval between the flash and the thunder depends mainly on distance. A very short interval means that the sound did not have far to travel, so the lightning occurred nearby. Such a situation indicates immediate danger, and people should move into a substantial enclosed shelter rather than remain outdoors.