Introduction
Thunderstorms are violent atmospheric events characterized by lightning presence, strong gusty winds, thunder, hail or heavy rain, and dense clouds. They commonly result in local atmospheric instability, and one thunderstorm can cause severe flooding and tornadoes. They occur when rapid updrafts send warm layers of moist air to cooler atmosphere regions. Additionally, thunderstorms cause different effects such as shock, electrocution, and deaths in human lives. This essay will focus on the conditions that cause thunderstorms to form and dissipate, the lifecycle and development of a thunderstorm cell, and the variations where thunderstorms can develop beyond a single cell. Moreover, it discusses the hazards to aviation that can be associated with thunderstorms and actions or measures that can be taken to avoid or minimize these hazards.
Conditions That Cause Thunderstorms to Form and Dissipate
Thunderstorms normally develop in warmer spring months, fall, or summer. They are formed by turbulence and atmospheric imbalance initiated by various conditions such as an unstable atmosphere, sufficient moisture, and a way to make the atmosphere more like a lift (Bullock et al., 2018). Moisture is essential in generating clouds and precipitation, and an unstable atmosphere has to be relatively warm and rises swiftly, which is required to form clouds. The air has to be more buoyant than the surrounding air to rise rapidly. The air close to the ground may become buoyant and rise swiftly through the atmosphere when the atmosphere is unstable. Finally, a lift is a means that can trigger atmospheric motion. It can be generated from sea breezes, fronts, or mountains. The lift can be some form of boundary, including a cooling aloft or heating resulting from the sun.
Thunderstorms start to dissipate when the updrafts begin to be overpowered by the downdrafts. Downdrafts interrupt or stop the supply of warm, humid air from the updrafts, which dissipates or kills out the thunderstorms (Islam & Ryan, 2016). This follows the fact that cloud droplets cannot develop since warm moist air cannot rise anymore because they have been cut off. As a result, the thunderstorms dissipate with light wain, and the cloud disappears slowly.
The Development and Life Cycle of a Thunderstorm Cell
The life cycle of a normal thunderstorm cell happens in 3 distinct stages, including the towering cumulus or developing stage, the mature cumulus stage, and the dissipating stage. The towering cumulus stage is identified with a cumulus cloud that is normally pushed aloft by a rising air column. Additionally, as the updraft continues to grow, the cumulus cloud momentarily resembles a tower hence the name towering cumulus. This stage contains irregular lightning with little to no rain (Taszarek et al., 2020). At this stage, moisture masses get lifted upwards into the atmosphere. Solar illumination can initiate this lift where thermals are generated by heating the ground. The lift can also be generated by two winds converging and sending the air upwards. The cumulus clouds are formed from liquid drops of water that condense from the moisture sent upwards. This happens because the cooler temperatures at high altitudes provide the necessary condition for the water to condense. Latent heat is released as the water vapor condenses into liquid, warming the air, which makes it to be less dense compared to the drier surrounding air. The air then rises in an updraft through convection, that is, convective precipitation generating a low-pressure zone within and below the developing thunderstorm.
The thunderstorm enters the second stage, the mature stage when the updraft continues to supply the storm, and the cumulus cloud becomes a cumulonimbus cloud presenting downdrafts and updrafts or sinking air. At this stage, the warmed air continues to rise to a region of warmer air and cannot rise anymore. Instead, the air spreads out, generating an anvil shape for the storm, which results in the formation of a cumulonimbus incus. Additionally, the water droplets combine into heavier, larger droplets that later become ice particles after freezing. The ice particles then become rain as they start to melt when falling. If the updraft is not adequately strong, the water droplets are held upwards until they become fairly huge and they fall as hail instead of rain because they do not melt completely. Additionally, the falling droplets as rain pull the surrounding air, generating downdrafts despite the presence of updrafts (Islam & Ryan, 2016). The occurrence of both updrafts and downdrafts causes the development of cumulonimbus clouds.
In the final stage, downdrafts dominate the thunderstorm, which kills updrafts necessary for the formation and maintenance of a cumulonimbus cloud, making it dissipate. The downdrafts force out of the storm, fall on the ground, spread, and die out, also called the downburst phenomenon (Islam & Ryan, 2016). Moreover, the cooled air taken to the ground by the downdraft interrupts the supply of moist warm air, making the updraft disappear and dissipate the thunderstorm. In an atmosphere that contains no vertical wind shear, thunderstorms fade as they force an outflow in every direction, cutting off the inflow of warm air, which inhibits the further development of thunderstorms. During this stage, a weak flow of winds and light rain may continue for some time before leaving only a remnant anvil top.
Single-cell thunderstorms can become multi-celled if they develop when vertical wind shear becomes adequate. A multi-cell thunderstorm is a family or cluster of isolated cells in various life cycle stages. Multicellular convection can last for several hours even though every isolated-cell storm that generates a multi-cell thunderstorm has a life span of 20 to 30 minutes (Taszarek et al., 2020). This is because new cells constantly form a more controlled gust front lifting moist warm air that flows into the thunderstorm. The gust front consistently starts new cells in contrast to the single-cell convection. Eventually, a group of multi-cell thunderstorms acquires its start similar to that of a single-cell thunderstorm. Moreover, the corresponding cumulus towers accompanied by new updrafts are isolated from their neighbors, and the newest cumulus tower develops away from the oldest cells along the gust front that are potentially in the dissipating stage. As a result, a chain or group of isolated thunderstorm cells develop within one huge thunderstorm with different life cycle stages. This thunderstorm does not lose the supply of warm, moist air, setting the convergence stage along gust fronts to start new convection, proving that these storms are self-perpetuating.
Hazards to Aviation
Thunderstorms have many hazards to aviation, including turbulence, lightning, icing, and wind shear. Thunderstorm outflow can result in wind speed and direction changes near the surface during vital or critical flight phases in wind shear. Wind shear is most risky at low altitudes during landing or takeoff but can happen at any altitude (Islam & Ryan, 2016). This is because a swift loss in airspeed on the last approach from wind shear can bring a plane disturbingly close to stall speed. As a result, a pilot should include half the gust factor on a windy day during landing to ensure that the plane is protected from swift loss in airspeed from wind shear. Additionally, pilots should watch for reports from other pilots on wind shear.
Secondly, pilots can expect to encounter airframe icing in all thunderstorms following that, they are driven in part by the freezing of liquid water to ice. This ice buildup on the plane surface is also known as icing. The icing interferes with the plane’s aerodynamics reducing lift and increasing drag, making the aircraft go into an aerodynamic stall and speed alteration (Bhardwaj & Singh, 2018). A pilot can keep the aircraft instruments running by making sure the pitot heat is on if ice starts sticking on the plane. The pilot has to take the plane from its current location by changing altitude or turning it back, which sends it to a warmer, ice-free region (Islam & Ryan, 2016). After changing the location, the pilots have to keep the windshield warm because they will need to see out the plane front. They can do this by putting the cabin heat control knob on, opening the Defroster Control Outlets to attain optimum windshield defroster airflow, and adjusting the Cabin Air Knob to gain maximum defroster heat.
Thirdly, electronic navigational and communication equipment can be damaged if an aircraft gets struck by lightning. Moreover, lightning can lead to an aircraft explosion because a strike can cause fuel leaks (Taszarek et al., 2020). However, pilots are highly advised to check solely on the instrument rating when encountering a cumulonimbus cloud during a thunderstorm since they may be blinded by nearby lightning. Lighting can be detected using Lightning Detection Networks (LDN) which monitor thunderstorm intensity, development, and movement. They are used to provide meteorological services with data that indicate if lightning is to be expected or has been detected, which allows safe route planning and helps avoid lightning. Moreover, LDN provides Air Traffic Control with information necessary for coordinating the movements of airplanes and warning pilots of severe weather.
Lastly, turbulence is present in all thunderstorm types that can destroy an aircraft when severe. This kind of turbulence is often found between downdrafts and updrafts. As a result, navigating through turbulence can significantly increase stress on the aircraft (Bhardwaj & Singh, 2018). Turbulence can be avoided by flying at higher altitudes. This is because the pilot will always encounter smooth air beyond the cloud level. Moreover, aircrews depend on warnings from other pilots that have flown in the region recently. They can also get warnings from a plane ahead of them over the radio (Bullock et al., 2018). Additionally, pilots rely on pilot reports (PIREPS) made to air traffic control, which conveys information to any flight crew flying into a turbulence area.
One example of when thunderstorms caused an accident is the case of Delta Flight 191. The aircraft left Fort Lauderdale, Florida, on August 2, 1985, and headed for Dallas, Texas, in the afternoon (History, 2019). The light was normal until they approached the Dallas region, where summer afternoons mostly included thunderstorms. The flight crew did not cancel the landing even after seeing lightning north of the airport. The pilot slowed the thrust while the plane entered strong headwinds anticipating that an updraft would hold the altitude of the plane.
However, they encountered an unexpected wind shear together with a wind blast from the tail. Moreover, the pilot lost plane control and crashed 6,000 feet away from the runway (History, 2019). 135 people died, and 15 were injured in the crash caused by a sudden formation of a supercell that resulted from strong winds (History, 2019). In addition, the plane crashed into a car and killed the driver. Investigation showed that drastic weather changes had occurred 8 minutes before the crash (History, 2019). The aircrew, in this case, saw the developing thunderstorm and still decided to land. Finally, pilots should be careful and logical if they encounter such a case. Flight crews should always know that it is not safe to land or go into a visible storm and move away from the region. Pilots can avoid the thunderstorm and change their route to land at another airport or wait until the storm passes.
Conclusion
In conclusion, the essay has discussed the conditions that cause the formation and dissipation of thunderstorms. It has also described the lifecycle and development of thunderstorms and variations that can form more than one thunderstorm cell. Moreover, it has shown aviation hazards associated with thunderstorms and actions to minimize and detect them. Thunderstorms form a combination of moisture, an unstable atmosphere, and a lift to initiate movement of the atmosphere. They start to die when downdrafts begin to overpower the updrafts. The developing stage, mature stage, and dissipation stage form the basic life cycle of a thunderstorm. Finally, thunderstorms may at times form more than one thunderstorm cell called a multi-cell thunderstorm. In addition, has various hazards to aviation, including turbulence, lightning, icing, and wind shear, which can lead to adverse accidents like the case of Delta Flight 191.
References
Bhardwaj, P., & Singh, O. (2018). Spatial and temporal analysis of thunderstorm and rainfall activity over India. Atmósfera, 31(3), 255-284. Web.
Bullock, J., Haddow, G., & Coppola, D. (2018). Hazards. Homeland Security, 45-66. Web.
History. (2019). Sudden thunderstorm causes plane crash. HISTORY. Web.
Islam, T., & Ryan, J. (2016). Hazard mitigation in emergency management (1st ed.). Butterworth-Heinemann is an imprint of Elsevier.
Taszarek, M., Kendzierski, S., & Pilguj, N. (2020). Hazardous weather affecting European airports: Climatological estimates of situations with limited visibility, thunderstorm, low-level wind shear and snowfall from ERA5. Weather and Climate Extremes, 28, 1-48. Web.