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In meteorology, a heat burst is a rare atmospheric phenomenon characterized by gusty winds along with a rapid increase in temperature and decrease in dew point (moisture). Heat bursts typically occur during night-time and are associated with decaying thunderstorms.
Although this phenomenon is not fully understood, it is theorized that the event is caused when rain evaporates (virga) into a parcel of cold, dry air high in the atmosphere- making the air denser than its surroundings.The parcel descends rapidly, warming due to compression, overshoots its equilibrium level and reaches the surface, similar to a downburst.
Recorded temperatures during heat bursts have reached well above 40 °C (104 °F ), sometimes rising by 10 °C (18 °F) or more within only a few minutes. More extreme events have also been documented, where temperatures have been reported to exceed 50 °C (122 °F). However, such extreme events have never been officially verified. Heat bursts are also characterized by extremely dry air and are sometimes associated with very strong, even damaging, winds.
In general, heat bursts occur during the late spring and summer seasons. During these times, thunderstorms tend to generate due to day heating and lose their main energy during the evening hours.Due to a potential temperature increase, heat bursts normally occur at night; however, heat bursts have also been recorded to occur during the daytime. Heat bursts have lasted for times spanning from a couple of minutes to several hours. The rare phenomenon is usually accompanied by strong gusty winds, extreme temperature changes, and an extreme decrease in humidity. They occur near the end of a weakening thunderstorm cluster. Dry air and a low-level inversion are also present during the storm.
As the thunderstorm starts to dissipate, the layer of clouds start to rise. After the layer of clouds have risen, a rain-cooled layer remains. The cluster shoots a burst of unsaturated air down towards the ground. In doing so, the system loses all of its updraft related fuel. °C per 1000 meters (5.5 °F per 1000 feet) of descent. The warm air from the cluster replaces the cool air on the ground. The effect is similar to someone blowing down on a puddle of water. On 4 March 1990, the National Weather Service in Goodland, Kansas detected a system that had weakened, containing light rain showers and snow showers. It was followed by gusty winds and a temperature increase. A heat burst was being observed. The detection proved that heat bursts can occur in both summer months and winter months. The occurrence also proved that a weakening thunderstorm was not needed in the development of heat bursts.The raindrops begin to evaporate into dry air, which emphasizes the effects of the heat bursts. As the unsaturated air descends, the air pressure increases. The descending air parcel warms at the dry adiabatic lapse rate of approximately 10
The first step of forecasting and preparing for heat bursts is recognizing the events that come before heat bursts occur. Rain from a high convection cloud falls below cloud level and evaporates, cooling the air. Air parcels that are cooler than the surrounding environment fall. And lastly, temperature conversion mixed with a downdraft momentum continue downward until the air reaches the ground. The air parcels then become warmer than their environment. McPherson, Lane, Crawford, and McPherson Jr. researched the heat burst system at the Oklahoma Mesonet, which is owned by both the University of Oklahoma and Oklahoma State University. The purpose of their research was to discover any technological benefits and challenges in detecting heat bursts, document the time of day and year that heat bursts mostly occur, and to research the topography of where heat bursts mostly occur in Oklahoma. Scientists and meteorologists use archived data to manually study data that detected 390 potential heat burst days during a fifteen-year period. In studying the archived data, they observed that 58% of the potential days had dry-line passages, frontal passages or a temperature change. The temperature change was due to an increase in solar radiation in the hours of the morning or a daytime precipitation weather system. By studying the archived data, the scientists' have the ability to determine the beginning, peak and end of heat burst conditions. The peak of heat burst conditions is the maximum observed temperature. The beginning of the heat burst occurrence is the time when the air temperature began to increase without decreasing until after the heat burst. The end of the heat burst is when the system ceased to affect the temperature and dew point of the area. In addition to researching the life cycle and characteristics of heat bursts, a group of scientists concluded that the topography of Oklahoma coincided with the change in atmospheric moisture between northwest and southeast Oklahoma. An increase in convection normally occurs over the United States High Plains during the late spring and summer. They also concluded that a higher increase in convection develops if a mid-tropospheric lifting mechanism interacts with an elevated moist layer.
A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are sometimes called thundershowers."NWS JetStream". National Weather Service. Retrieved 26 January 2019.</ref> Thunderstorms occur in a type of cloud known as a cumulonimbus. They are usually accompanied by strong winds, and often produce heavy rain and sometimes snow, sleet, or hail, but some thunderstorms produce little precipitation or no precipitation at all. Thunderstorms may line up in a series or become a rainband, known as a squall line. Strong or severe thunderstorms include some of the most dangerous weather phenomena, including large hail, strong winds, and tornadoes. Some of the most persistent severe thunderstorms, known as supercells, rotate as do cyclones. While most thunderstorms move with the mean wind flow through the layer of the troposphere that they occupy, vertical wind shear sometimes causes a deviation in their course at a right angle to the wind shear direction.
The humidex is an index number used by Canadian meteorologists to describe how hot the weather feels to the average person, by combining the effect of heat and humidity. The term humidex was first coined in 1965. The humidex is a nominally dimensionless quantity based on the dew point.
A squall line or quasi-linear convective system (QLCS) is a line of thunderstorms forming 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. Strong straight-line winds can occur where the squall line is in the shape of a bow echo. Tornadoes can occur along waves within a line echo wave pattern (LEWP), where mesoscale low-pressure areas are present. Some bow echoes which develop within the summer season are known as derechos, and they move quite fast through large sections of territory. On the back edge of the rainband associated with mature squall lines, a wake low can be present, sometimes associated with a heat burst.
METAR is a format for reporting weather information. A METAR weather report is predominantly used by aircraft pilots, and by meteorologists, who use aggregated METAR information to assist in weather forecasting.
A downburst is a strong ground-level wind system that emanates from a point source above and blows radially, that is, in straight lines in all directions from the point of contact at ground level. Often producing damaging winds, it may be confused with a tornado, where high-velocity winds circle a central area, and air moves inward and upward; by contrast, in a downburst, winds are directed downward and then outward from the surface landing point.
The heat wave of 1995 derecho series are a series of derechos that occurred from July 11 through July 15, 1995 in the U.S. and Ontario, Canada. This weather event is among one of the least known about but still notable weather events that occurred during the 20th century.
A southerly buster is the colloquial name of an abrupt southerly wind change in the southern regions of New South Wales and Victoria, Australia, which approaches from the southeast, mainly on a hot day, bringing in cool, usually bringing severe weather and a dramatic temperature drop, thus ultimately replacing and relieving the prior hot conditions. Marking the boundary between hot and cool air masses, a southerly buster is sometimes represented by a roll-up cloud perpendicular to the coast, which appears from the south and coexists with the wind change, though sometimes there is little visual signal of the southerly's arrival.
This article describes severe weather terminology used by the National Weather Service (NWS) in the United States. The NWS, a government agency operating as an arm of the National Oceanic and Atmospheric Administration (NOAA) branch of the United States Department of Commerce (DoC), defines precise meanings for nearly all of its weather terms.
Kopperl is an unincorporated community in Bosque County, Texas, United States. It lies on the northwestern end of Lake Whitney, and has an estimated population of 225.
This article describes severe weather terminology used by the Meteorological Service of Canada, a branch within Environment and Climate Change Canada. The article primarily describes various weather warnings, and their criteria. Related weather scales and general weather terms are also addressed in this article. Some terms are specific to certain regions.
Launch commit criteria are the criteria which must be met in order for the countdown and launch of a space shuttle or other launch vehicle to continue. These criteria relate to safety issues and the general success of the launch, as opposed to supplemental data.
The Corn Belt derecho was a progressive derecho which affected a large area of the central United States on June 29, 1998. In the morning, thunderstorms, including a supercell, developed over South Dakota and tracked into central Iowa. As the thunderstorms reached central Iowa, a strong rear-inflow jet developed which caused the thunderstorm to take on a different characteristic, becoming a derecho. It traveled more than 600 miles in about ten hours, causing more than $125 million worth of widespread damage destruction, especially to crops, and was responsible for power outages to nearly a half a million people.
Atmospheric convection is the result of a parcel-environment instability, or temperature difference layer in the atmosphere. Different lapse rates within dry and moist air masses lead to instability. Mixing of air during the day which expands the height of the planetary boundary layer leads to increased winds, cumulus cloud development, and decreased surface dew points. Moist convection leads to thunderstorm development, which is often responsible for severe weather throughout the world. Special threats from thunderstorms include hail, downbursts, and tornadoes.
Airport weather stations are automated sensor suites which are designed to serve aviation and meteorological operations, weather forecasting and climatology. Automated airport weather stations have become part of the backbone of weather observing in the United States and Canada and are becoming increasingly more prevalent worldwide due to their efficiency and cost-savings.
A wake low, or wake depression, is a mesoscale low-pressure area which trails the mesoscale high following a squall line. Due to the subsiding warm air associated with the systems formation, clearing skies are associated with the wake low. Once difficult to detect in surface weather observations due to their broad spacing, the formation of mesoscale weather station networks, or mesonets, has increased their detection. Severe weather, in the form of high winds, can be generated by the wake low when the pressure difference between the mesohigh preceding it and the wake low is intense enough. When the squall line is in the process of decay, heat bursts can be generated near the wake low. Once new thunderstorm activity along the squall line concludes, the wake low associated with it weakens in tandem.
The Oklahoma Mesonet is a network of environmental monitoring stations designed to measure the environment at the size and duration of mesoscale weather events. The phrase "mesonet" is a portmanteau of the words mesoscale and network. In meteorology, “mesoscale” refers to weather events that range in size from approximately 1 mile (1.6 km) to 150 miles (240 km) and can last from several minutes to several hours. Mesoscale events include thunderstorms, wind gusts, heat bursts, and dry lines. Without densely spaced weather observations, these mesoscale events might go undetected. In addition to surface weather observations, Oklahoma Mesonet stations also include environmental data such as on insolation and soil conditions, and some sites are co-located with wind profilers.
Rawalpindi features a humid subtropical climate with long and hot summers, a monsoon and short, mild and wet winters. Its climate is classified as very similar to its twin city Islamabad, but the geographical location and extreme urbanization of Rawalpindi has led to weather and climatic conditions that are notably different from its twin. Rawalpindi's weather has historically been known to change rather quickly due to its proximity to Himalayas and the Pir Panjal Range. These mountains not only influence the weather of the city, but also provide great recreation during the hot months. Furthermore, Its warm comfortable mean annual temperature of 21.3 °C (70 °F) attracts people to live here permanently from all over Pakistan. The average annual rainfall is abundant at 1,346.8 millimetres (53.02 in), most of which falls in the monsoon season. However, frontal cloud bands also bring significant rainfall in the winter. In summers, June is the hottest with record maximum temperature at a blistering 48.3 °C (119 °F) recorded on 13 June 1953. On the other hand, January is the coldest month of the year when temperature can drop to a minimum −3.9 °C (25 °F) in the winter recorded on 17 January 1967. Throughout the year, Rawalpindi and Islamabad experience an average of about 98 thunderstorms, which is the highest frequency of thunderstorms in Punjab province of any plane station. In fact, most rainfall in the city is accompanied by a thunderstorm with peak activity experienced in August. Record rainfall was experienced in the year 2013 at a massive 1,988 millimetres (78.3 in) mostly due to an unusually wet monsoon season. On a typical day, the city hosts breezy afternoons, but usually calm to light breeze wind conditions are observed after midnight. The mean annual wind speed of Rawalpindi is roughly 10 kilometres per hour (6.2 mph) at 14 m height. Moreover, just a few kilometers southwest of Rawalpindi, the potential power generation has been identified by U.S. Aid to be between marginal to good at 50 m height.
2014 Pentecost weekend storms in Europe were a series of severe supercell storms affecting western Europe which followed a heatwave in early June 2014, resulting from a Spanish plume synoptic weather pattern. The weekend saw repeated convective storm development across an arc from southwest France towards Paris and on towards Belgium and northwest Germany, where warm air masses interacted with the cooler air brought in by an area of low pressure moving towards the continent from the Atlantic. Outbreaks of severe weather were reported from these storm developments with the worst damages occurring over the German state of North Rhine-Westphalia on 9 June, where the storm was described as one of the most violent in decades by the German weather service, this storm is also referred to as low pressure area "Ela" in some German media.
This glossary of meteorology is a list of terms and concepts relevant to meteorology and atmospheric science, their sub-disciplines, and related fields.