![Wakelowimage](https://upload.wikimedia.org/wikipedia/commons/d/d3/Wakelowimage.JPG)
A wake low, or wake depression, is a
mesoscale low-pressure area
In meteorology, a low-pressure area, low area or low is a region where the atmospheric pressure is lower than that of surrounding locations. Low-pressure areas are commonly associated with inclement weather (such as cloudy, windy, with possible ...
which trails the mesoscale high following a
squall line
A squall line, or more accurately a quasi-linear convective system (QLCS), is a line of thunderstorms, often forming along or ahead of a cold front. In the early 20th century, the term was used as a synonym for cold front (which often are accompa ...
. Due to the subsiding warm air associated with the system's formation, clearing skies are associated with the wake low. Once difficult to detect in
surface weather observation
Surface weather observations are the fundamental data used for safety as well as climatological reasons to forecast weather and issue warnings worldwide. They can be taken manually, by a weather observer, by computer through the use of automate ...
s due to their broad spacing, the formation of mesoscale
weather station
A weather station is a facility, either on land or sea, with instruments and equipment for measuring atmospheric conditions to provide information for weather forecasts and to study the weather and climate. The measurements taken include tempera ...
networks, or
mesonet
In meteorology and climatology, a mesonet, portmanteau of mesoscale network, is a network of automated weather and, often, environmental monitoring stations designed to observe mesoscale meteorological phenomena and/or microclimates.
Dry lines ...
s, has increased their detection.
[Mark R. Conder, Steven R. Cobb, and Gary D. Skwira (2006)]
West Texas Mesonet Observations of Wake Lows and Heat Bursts Across Northwest Texas.
American Meteorological Society
The American Meteorological Society (AMS) is the premier scientific and professional organization in the United States promoting and disseminating information about the Atmospheric sciences, atmospheric, Oceanography, oceanic, and Hydrology, hydr ...
. Retrieved on 2009-04-24. Severe weather
Severe weather is any dangerous meteorological phenomenon with the potential to cause damage, serious social disruption, or loss of human life. Types of severe weather phenomena vary, depending on the latitude, altitude, topography, and atm ...
, in the form of high
wind
Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hou ...
s, 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 burst
In meteorology, a heat burst is a rare atmospheric phenomenon characterized by a sudden, localized increase in air temperature near the Earth's surface. Heat bursts typically occur during night-time and are associated with decaying thunderstorm ...
s can be generated near the wake low. Once new
thunderstorm
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 someti ...
activity along the squall line concludes, the wake low associated with it weakens in
tandem
Tandem, or in tandem, is an arrangement in which a team of machines, animals or people are lined up one behind another, all facing in the same direction.
The original use of the term in English was in ''tandem harness'', which is used for two ...
.
Formation
Wake lows form due to
adiabatic warming in the wake of mature squall lines at the back edge of their rain shields, where
evaporative cooling is unable to offset warming due to atmospheric
subsidence
Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope move ...
, or downward motion. They can be caused by
gravity wave
In fluid dynamics, gravity waves are waves generated in a fluid medium or at the interface between two media when the force of gravity or buoyancy tries to restore equilibrium. An example of such an interface is that between the atmosphere ...
s which duct through boundary layers which are deep and cold to the north of a
weather front
A weather front is a boundary separating air masses for which several characteristics differ, such as air density, wind, temperature, and humidity. Disturbed and unstable weather due to these differences often arises along the boundary. For in ...
. As with mesoscale
high-pressure area
A high-pressure area, high, or anticyclone, is an area near the surface of a planet where the atmospheric pressure is greater than the pressure in the surrounding regions. Highs are middle-scale meteorological features that result from interpl ...
s behind a squall line, when new
thunderstorm
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 someti ...
development stops along the squall line, the wake low will weaken as well. Clearing conditions will accompany the wake low, due to the descending warm air mass associated with the feature.
Within the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
, these systems have been observed to form in the
Mississippi river
The Mississippi River is the second-longest river and chief river of the second-largest drainage system in North America, second only to the Hudson Bay drainage system. From its traditional source of Lake Itasca in northern Minnesota, it f ...
valley,
Southeast,
Florida
Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...
, and
Great Plains
The Great Plains (french: Grandes Plaines), sometimes simply "the Plains", is a broad expanse of flatland in North America. It is located west of the Mississippi River and east of the Rocky Mountains, much of it covered in prairie, steppe, an ...
.
[Robert R. Handel and Pablo Santos (2005)]
P4.6 Observations From the 13 April 2004 Wake Low Damaging Wind Event In South Florida.
American Meteorological Society
The American Meteorological Society (AMS) is the premier scientific and professional organization in the United States promoting and disseminating information about the Atmospheric sciences, atmospheric, Oceanography, oceanic, and Hydrology, hydr ...
. Retrieved on 2009-04-24. A wake low producing strong northeasterly winds of and very rough seas was determined to be responsible for the capsizing of the ''
Seacor Power
The ''Seacor Power'' was a , 265 Class liftboat, constructed in 2002, belonging to Seacor Marine and flagged in the United States. The ship was powered by two Caterpillar 3508B@1900hp engines.
Capsizing incident
On April 13, 2021 ''Seacor P ...
'' lift boat (according to the
National Weather Service
The National Weather Service (NWS) is an Government agency, agency of the Federal government of the United States, United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weathe ...
) with 13 mariners drowned or missing.
Detection
![Tahomawakelow](https://upload.wikimedia.org/wikipedia/commons/5/57/Tahomawakelow.gif)
Both direct and indirect ways have been found to indicate the presence of a wake depression. The most direct is through the use of surface observations. Prior to the development of mesoscale weather station networks, or mesonets, it was difficult to locate wake lows. With the advent of mesoscale networks, wake lows have become easier to detect. On
weather satellite
A weather satellite or meteorological satellite is a type of Earth observation satellite that is primarily used to monitor the weather and climate of the Earth. Satellites can be polar orbiting (covering the entire Earth asynchronously), or ge ...
and
weather radar
Weather radar, also called weather surveillance radar (WSR) and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, and estimate its type (rain, snow, hail etc.). Modern weather radars are mostly puls ...
imagery, wake lows and heat bursts normally occur on the rear side of a precipitation area. However, within larger precipitation areas, they can be located within the area showing a minimum of returns.
When using velocity data from a
WSR-88D doppler radar, high winds on the back edge of reflectivity data can give away the location of a wake low.
Association with heat bursts
Heat bursts are rare atmospheric phenomenon characterized by gusty winds and a rapid increase in
temperature
Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer.
Thermometers are calibrated in various temperature scales that historically have relied o ...
and decrease in
dew point
The dew point is the temperature to which air must be cooled to become saturated with water vapor, assuming constant air pressure and water content. When cooled below the dew point, moisture capacity is reduced and airborne water vapor will cond ...
(moisture). Heat bursts typically occur during night-time and are associated with decaying
thunderstorms
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 someti ...
. In association with wake lows, heat bursts are caused when rain evaporates (
virga
In meteorology, a virga, also called a dry storm, is an observable :wikt:fallstreak, streak or Precipitation shaft, shaft of precipitation (meteorology), precipitation falling from a cloud that Evaporation, evaporates or Sublimation (phase t ...
) 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 In meteorology, the equilibrium level (EL), or level of neutral buoyancy (LNB), or limit of convection (LOC), is the height at which a rising parcel of air is at the same temperature as its environment.
This means that unstable air is now stable ...
and reaches the surface, similar to a
downburst
In meteorology, a downburst is a strong downward and outward gushing wind system that emanates from a point source above and blows radially, that is, in straight lines in all directions from the area of impact at surface level. Capable of pro ...
.
Recorded temperatures during heat bursts have reached well above , sometimes rising by 20 °F (11 °C) or more within only a few minutes. More extreme events have also been documented, where temperatures have been reported to exceed , although 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,
wind
Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hou ...
s.
See also
*
Mesoscale convective vortex A mesovortex is a small-scale rotational feature found in a convective storm, such as a quasi-linear convective system (QLCS, i.e. squall line), a supercell, or the eyewall of a tropical cyclone. Mesovortices range in diameter from tens of miles to ...
(MCV)
References
{{good article
Vortices
Types of cyclone
Severe weather and convection