Dangerous Thunderstorm Phenomenon - Term Paper Example

Contents Contents 1 Introduction 2 How thunderstorms form 2 Role of cumulonimbus clouds in thunderstorms 3 Cumulonimbus clouds 3 Electrical charges and lightning 4 Types of thunderstorms 5 Air mass thunderstorm 5 Multi-cell storm  6 Squall Lines 6 Mesoscale Convective Systems (MCS) 6 Supercell thunderstorm 7 Life cycle of thunderstorms 8 The developing stage 8 Mature stage 8 Dissipating stage 8 Thunderstorm detection 9 Satellites 9 Radars 9 Aviation accident related to thunderstorms – Delta Flight 191 – August 2, 1985 10 Conclusion 12 Reference List 13 Introduction Thunderstorms refer to a weather phenomenon that is characterized by thunder, lightning and a number of other aspects of weather including hail, heavy rainfall, or sudden temperature changes, snow and high winds in winter. Thunderstorms are mostly formed from cumulonimbus clouds that are vertical and tall clouds. The clouds and resultant thunderstorms form after occurrence of convection, a process where heated moist air goes up to higher atmospheric levels. This paper investigates the basic facts about thunderstorms and analyzes an aviation accident that was occasioned by occurrence of a thunderstorm. How thunderstorms form There are three basic components that are necessary for a thunderstorm to occur. These include unstable air that keeps on rising after being lifted, moisture, and a lifting mechanism for the aforementioned air. When a storm goes up and enters freezing air, a number of ice particles form as a result of freezing of the drops of liquid within the storm. The particles of ice can become even bigger as they collect and freeze surrounding liquid drops and as they condense vapour. After two particles of ice collide, the result is a bouncing off each other. However, one ice particle may brush the other and get a bit of its ice, together with an electric charge. When several collisions occur this way, then big areas of electric charge are formed, which result in a bolt of lightning. The lightning bolt forms the waves of sound that we hear as thunder (“Severe Weather 101”, 2014). Role of cumulonimbus clouds in thunderstorms Cumulonimbus clouds Cumulonimbus clouds are dense and heavy clouds that have significant vertical extent, taking the form of huge towers or a mountain. In most cases, its upper portion is striated, fibrous or smooth, and almost always flattened. This part normally spreads out forming the shape of a vast plume or anvil. In this cloud’s base that is frequently dark with low ragged clouds, precipitation often takes the form of a virga. The cumulonimbus is known for their short-lived heavy showers, often with lightning, thunder or hail. It is important to note at this point that not all clouds that are cumulonimbus result in thunderstorms. Some cumulonimbus clouds only result in heavy hail or showers. Averagely, one cumulonimbus cloud will take around an hour to form, grow and dissipate. Such a cloud will lead to around thirty minutes of lightning and thunder. In cases where the thunderstorm lasts for longer than half an hour, then the clouds are composed of more than one cumulonimbus (“Thunderstorms”, 2011). Fig. 1 below shows a cumulonimbus cloud. (“Thunderstorms”, 2011, p. 2). Electrical charges and lightning Lightning occurs when electrons move from one block of ice/cloud to another, casing a large electrical spark. From the surface of the earth, the lightning streak, which represents the path that is taken b electrons as they move, is visible. The first step before the occurrence of lightning is the formation of water droplets in a cloud, which are moved towards the cloud’s top by up-draughts – strong internal winds. After reaching the cloud’s top, they are converted to ice by the low temperatures there. Some ice pieces remain small as others form hails. As hails get larger, they move downwards through the cloud colliding with small particles of ice in upward motion. After the collision, the hail takes some electrons off the smaller ice particles, giving the former a negative charge and the latter a positive charge. Thus eventually the cloud’s top gains a positive charge while the bottom part of the cloud gets a net negative charge. Apart from attraction by the aforementioned positive charge that forms the top of the cloud, the cloud’s bottom is attracted by surrounding clouds as well as the ground. If the force of attraction gets strong enough, the electrons in the cloud’s base move to the surrounding clouds (“Thunderstorms”, 2011). As more negative charges move to the cloud’s base, the electrons that are near the surface of the ground are repelled leaving the objects on the ground and the ground itself with a net positive charge. When the attraction between the ground and its objects, and the cloud’s negative charge grows strong enough, electrons are transferred from the cloud towards the ground following a river delta path with step leaders forming the different directions (“Thunderstorms”, 2011). When the stepped leader comes close to the ground, tall objects on the ground’s surface release positive charge that moves upwards, causing sparks that are referred to as upward streamers. On meeting the upward streamer, the stepped leaser’s channel for forming lightning is completed and thus electrons move faster towards the ground lighting up the channel. The first electrons that hit the ground light the channel starting from the bottom, leading to the lighting of the stepped leaders, which are visible as the lightning (“Thunderstorms”, 2011). After the channel is depleted of electrons, the lightning stops because there are no more electrons moving. However, electrons can be attracted from other cloud parts leading to a dark leader that causes a return stroke. Repeated dart leaders and return strokes lead to flickering of the lightning because they occur at high speeds (“Thunderstorms”, 2011). Types of thunderstorms There are a number of thunderstorm types, which include the following: Air mass thunderstorm This refers to isolated thunderstorms which normally occur in places where a vertical wind shear has not occurred. They are mild thunderstorms that last for about one hour. Their name reflects the fact they form inside an air mass. Air mass thunderstorms are started by lifting of air along a slope or a mountain, heating of the earth’s surface, or even an outflow of cool air from another thunderstorm. Multi-cell storm  This is the type of storm that is common in gardens, where new updrafts are occasioned along the edge leading air that is cooled by rain – i.e. the gust front. An individual cell in a multi-cell storm may last between half an hour and an hour, while the multi-cell storm system lasts for a number of hours. Multi-cell storms usually cause strong winds, flooding, tornadoes, as well as hail. Squall Lines This is a group of storms that are normally arranged in a line, with heavy rain and high wind in squalls. This kind of storm rarely leads to tornadoes because it passes quickly. Squall lines are normally long, stretching through a length of around hundreds of miles. However, they are fairly thin because their width is less than 20 miles. Mesoscale Convective Systems (MCS) An MCS refers to a system that is composed of several thunderstorms. When an MCS occurs, it can spread throughout a large area like a whole state, and last for long periods like for more than 12 hours. Radar images of the system of thunderstorms appear as broken lines, solid lines of cell cluster. The MCS include any of the following types of thunderstorm. Mesoscale convective complex (MCC) — this type refers to long-lived, wide-spread and circular that are identifiable via satellite. It is mainly formed from other storm types early in the morning or late at night, and it can spread throughout an entire state. Mesoscale convective vortex (MCV) — this refers to an area of low pressure that forms within an MCS, pulling winds to form a vortex – circling pattern. Since it only has a core of less than 60 miles and a depth of less than 3 miles, an MCV is often ignored in standard weather analysis. However, it is important to note that an MCV can persist for a period of 12 hours after dissipation of the parent MCS, thereby feeding the next outbreak of thunderstorm. If an MCV reaches tropical waters like the ones I the Gulf of Mexico, it can form the epicenter of a tropical hurricane or storm. Derecho – refers to a long-lived wide-spread wind storm, which normally occurs with rapidly moving thunderstorms or showers. Despite the fact that a derecho can be as destructive as a tornado, its destruction is normally in a one-direction straight swath. Consequently, its effects are usually referred to as straight-line wind damage (“Severe Weather 101”, n.d.). Supercell thunderstorm A supercell is a storm that lasts for more than an hour, and which is highly organized and fed by a rotating and tilted updraft. The updraft, which can be 50,000 feet tall and 10 miles in diameter, can persist for a period of up to an hour before the occurrence of a tornado. When the rotation mentioned above is detected by radar, it is referred to as a mesocyclon. Most violent and large tornadoes, which form from the larger rotation, result from supercells. Supercells, being the most powerful of all storms, lead to a large number of casualties and damage. The main reason why supercells are powerful and destructive is because of the rotating updraft that feeds itself, increasing the storm’s longetivity. The two factors, rotating updraft and a long storm, lead to violent and strong tornadoes (Sirvatka, n.d.) Life cycle of thunderstorms The life cycle of storms is composed of three stages, which include the following: The developing stage This is the stage in which a cumulus cloud is continually pushed in the upward direction by an updraft. With time, the cumulus cloud becomes a towering cumulus, meaning that it gains height with continued updraft. During this stage, rain is absent although there is some occasional lightning. Mature stage A storm matures when it is continually fed by the updraft, but rain begins to fall from the storm, leading to a downdraft, which refers to downward movement of air. After the above-mentioned downdraft together with rain-cooled air reaches the ground, it spreads out on the ground forming a line of gusty winds that are referred to as a gust front. During the mature stage, tornadoes, hail, strong winds, frequent lightning, and heavy rains are likely to occur. Dissipating stage At long last, the precipitation becomes so much that the downdraft overcomes the updraft. This is the stage that is referred to as the dissipation stage. On the ground, the warm moist air fuelling the storm is cut off by a fast-spreading gust front. At this stage, the intensity of precipitation decreases substantially but the stage remains dangerous due to lightning. Life cycle of a thunderstorm [+] (“Severe Weather 101”, n.d. p. 1). Thunderstorm detection Satellites Weather satellites are capable of seeing most areas on the earth’s surface. Satellites capture earth pictures from the space at regular intervals with the aim of determining the locations of clouds. Meteorologists study the patterns of these pictures over a long period of time with a view to establishing how rapidly the clouds are forming and growing, which is an indication of a possible thunderstorm. In addition, satellites can be used to study the temperatures of clouds. If the cloud has a top which is cold, then it is in the higher levels of the atmosphere and it is likely to cause a thunderstorm because it could be very tall. The movement of the clouds is also monitored in a bid to establish which areas on the surface of the earth are likely to experience the next thunderstorm. Radars Meteorologists frequently use weather radar because it can enable them to detect severe weather and rain, even when the atmosphere is dark or cloudy. Doppler radar works by sending out wave fields that are electromagnetic in nature, and which are reflected to the radar by an atmospheric phenomenon like precipitation. If an enormous amount of energy is captured by the radar as a reflection, then the implication is that there is hail or heavy precipitation. Doppler radar is also capable of showing the status of the wind inside or near the storm, which is instrumental in determining the kind of hazards that the storm may cause, and how the storm feeds itself. Aviation accident related to thunderstorms – Delta Flight 191 – August 2, 1985 On 2nd August in the year 1985, there occurred sudden and strong wind gusts at the Dallas/Fort Worth Airport, which is located in Texas. The wind gusts led to the crashing of Delta Flight 191 at the aforementioned airport, leading to the deaths of 135 people. The crash was reportedly caused by a supercell that formed in the airport. A supercell, as discussed above, is a form of a thunderstorm that is extremely violent and dangerous. Flight 191 had left Florida from Fort Lauderdale that afternoon, headed towards Dallas, Texas. The passengers who had boarded the plane enjoyed a flight that was completely normal until they came close to the central Texas area. Afternoons during the summer in the Dallas area sometimes include thunderstorms and the fateful day was one of those days when the area was having thunderstorms. The aforementioned flight maneuvered around a significantly large storm while following its scheduled flight path, and consequently approached the airport due south in the direction of runway 17. The crew of the plane saw lightning in the northern side of the airport, but they decided to continue with the planned landing, and thus they did not abort. This led to strong headwinds occurring in the path of the plane, which forced the pilot to slow the thrust because he expected the altitude of the plane to be upheld by the updraft in the storm. However, contrary to the pilot’s expectations, the storm had a sudden wind shear in the downward direction, which also came with a blast of wind that hit the tail of the plane. The plane was comparatively heavy and thus it did not react to the downward thrust with a quick upward thrust. This made the pilot to lose all control of the plane and consequently the plane crashed at an approximate 6,000 feet before reaching the intended runway. The plane collided with a car, killing the driver of the car instantly. After the collision, the plane skidded and ultimately hit two water tanks. As a result of the crash, a total of 135 people were killed and an additional 15 sustained very serious injuries. In an investigation that followed the tragic plane crash, it was revealed that the main cause of the crash was the fact that the area had experienced a drastic change in weather shortly before the scheduled landing of the plane. Actually, the resultant report estimated that the crash took place eight minutes after the weather changed into a thunderstorm of the supercell type. The unpredictable winds that brought down the plane were therefore as a result of supercell formation (“Sudden thunderstorm causes plane crash”, 2014). However, the investigation revealed some flaws in the way that the pilots handled the situation. It was suggested that because the pilots and crew could clearly see the developing storm from a distance as they got closer to the airport, they should have aborted the flight or planned for a better touchdown. In the contemporary aviation industry, such incidents and accidents are unlikely to occur because there have been substantial improvements in technology and therefore the location and progression of similar storms are closely monitored. Modern aircrafts are equipped with on-board equipment for depiction of weather. However, it is important to mention that these devices are fairly limited in capability. According to the manufacturer of the yoke-mounted GPS, the device is equipped to receive updates in intervals of five minutes in some aircraft. It must be appreciated that when dealing with thunderstorms that are rapidly developing and quickly moving, a lot can occur in the 5-minute interval. In addition, images picked by radar are normally representative of precipitation but not turbulence. As a measure for avoiding air crashes as a result of thunderstorms, it is recommended that areas with thunderstorm coverage of about 50% should be circumnavigated, or a distance of 20 miles kept between an aircraft and such areas. If the area cannot be completely skirted, it is recommended that the pilots should land nearby and wait until the storm clears. Conclusion From the discussion above, it is apparent that the formation of thunderstorms is caused by movement of air as a result of heating or as a result of coming across obstacles. There are a number of types of thunderstorms that include the air-mass storm, squall lines, the multi-cell storm, supercell thunderstorm and Mesoscale Convection Systems (MCS). The development and occurrence of a storm takes place through a number of stages that include the developing stage, the mature stage and the dissipating stage. Given the importance of the detection and prediction of thunderstorm occurrence, meteorologists use satellites and radars in detecting and predicting thunderstorms. This enables them to advise people accordingly, which ensures that weather-related accidents and incidents are reduced. The fact that flight 191 was downed by a supercell shows how dangerous thunderstorms are, and thus meteorologists and aviation stakeholders have been taken to minimize the chances of occurrence of a similar incident. Reference List Severe Weather 101. (n.d.). Retrieved from http://www.nssl.noaa.gov/education/svrwx101/thunderstorms/ Sirvatka, P. (n.d.). Thunderstorms. Retrieved from http://weather.cod.edu/sirvatka/es115/unit1/Thunderstorms.pdf Sudden thunderstorm causes plane crash. (2014). Retrieved from http://www.history.com/this-day-in-history/sudden-thunderstorm-causes-plane-crash Thunderstorms. (2011). Retrieved from http://www.metoffice.gov.uk/media/pdf/i/r/Fact_sheet_No._2.pdf Read More

As hails get larger, they move downwards through the cloud colliding with small particles of ice in upward motion. After the collision, the hail takes some electrons off the smaller ice particles, giving the former a negative charge and the latter a positive charge. Thus eventually the cloud’s top gains a positive charge while the bottom part of the cloud gets a net negative charge. Apart from attraction by the aforementioned positive charge that forms the top of the cloud, the cloud’s bottom is attracted by surrounding clouds as well as the ground.

If the force of attraction gets strong enough, the electrons in the cloud’s base move to the surrounding clouds (“Thunderstorms”, 2011). As more negative charges move to the cloud’s base, the electrons that are near the surface of the ground are repelled leaving the objects on the ground and the ground itself with a net positive charge. When the attraction between the ground and its objects, and the cloud’s negative charge grows strong enough, electrons are transferred from the cloud towards the ground following a river delta path with step leaders forming the different directions (“Thunderstorms”, 2011).

When the stepped leader comes close to the ground, tall objects on the ground’s surface release positive charge that moves upwards, causing sparks that are referred to as upward streamers. On meeting the upward streamer, the stepped leaser’s channel for forming lightning is completed and thus electrons move faster towards the ground lighting up the channel. The first electrons that hit the ground light the channel starting from the bottom, leading to the lighting of the stepped leaders, which are visible as the lightning (“Thunderstorms”, 2011).

After the channel is depleted of electrons, the lightning stops because there are no more electrons moving. However, electrons can be attracted from other cloud parts leading to a dark leader that causes a return stroke. Repeated dart leaders and return strokes lead to flickering of the lightning because they occur at high speeds (“Thunderstorms”, 2011). Types of thunderstorms There are a number of thunderstorm types, which include the following: Air mass thunderstorm This refers to isolated thunderstorms which normally occur in places where a vertical wind shear has not occurred.

They are mild thunderstorms that last for about one hour. Their name reflects the fact they form inside an air mass. Air mass thunderstorms are started by lifting of air along a slope or a mountain, heating of the earth’s surface, or even an outflow of cool air from another thunderstorm. Multi-cell storm  This is the type of storm that is common in gardens, where new updrafts are occasioned along the edge leading air that is cooled by rain – i.e. the gust front. An individual cell in a multi-cell storm may last between half an hour and an hour, while the multi-cell storm system lasts for a number of hours.

Multi-cell storms usually cause strong winds, flooding, tornadoes, as well as hail. Squall Lines This is a group of storms that are normally arranged in a line, with heavy rain and high wind in squalls. This kind of storm rarely leads to tornadoes because it passes quickly. Squall lines are normally long, stretching through a length of around hundreds of miles. However, they are fairly thin because their width is less than 20 miles. Mesoscale Convective Systems (MCS) An MCS refers to a system that is composed of several thunderstorms.

When an MCS occurs, it can spread throughout a large area like a whole state, and last for long periods like for more than 12 hours. Radar images of the system of thunderstorms appear as broken lines, solid lines of cell cluster. The MCS include any of the following types of thunderstorm. Mesoscale convective complex (MCC) — this type refers to long-lived, wide-spread and circular that are identifiable via satellite. It is mainly formed from other storm types early in the morning or late at night, and it can spread throughout an entire state.

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