? Crochet Echo – Definition and Explanations


Formation and propagation of the hook echo (center echo) in Kansas City, Missouri

L’touch echo is a characteristic signature in the form of low-level reflective echoes of a cloud (A cloud… contains lots of water droplets (or ice crystals)) of the type cumulonimbus (Cumulonimbus, from the cumulus family, is the largest extended cloud…) in the data a weather radar (Weather radar is a type of radar used in meteorology…). related to a mesocyclone (A mesocyclone is an area of ​​more or less vertical rotation in a thunderstorm. It…) one the storm (Storm, from Old French ore meaning wind, a disturbance…) supercellular and often associated with the presence of a tornado (Tornado (derived from the Spanish tornado, tornar, the verb to turn) is a whirlwind…). The presence of this fork is due to the descent of precipitation (rain, hail) and even debris in the downslope behind the storm. around (Autour is the name given by French bird nomenclature (update)…) shooting up in front. It is usually found quadrant (In Euclidean geometry: a quarter of the circumference of a circle (itself divisible by 100…) south (South is the cardinal point against north.) Where Southwest (Southwest is the half direction between the south and west cardinal points. The…) of the system. Its presence correlates so well with the presence of tornadoes that meteorologists National Weather Service (The National Weather Service (NWS) is the weather service of the United States…) Americans will send a tornado warning when it appears on the exits radar (Radar is a system that uses radio waves to detect and identify…). However, its presence is less obvious for low-level tornadoes in severe rainstorms, so it’s not the only clue meteorologists will be looking for.

The story

On April 9, 1953, Donald Staggs, a engineer (The main job of an engineer is to solve the problems of nature…) in electricity (It is a physical phenomenon due to different electric charges of electric current…) works for Illinois State Water Survey, was the first to note the hook echo commonly associated with hurricane storms in reflectance results. Mr. Staggs was studying the use of weather radar to estimate the amount of rain falling on his watershed when a tornado hit his watershed. territory (The concept of territory is becoming more and more important in geography and especially…) he said he learned and was able to combine it with the radar output.


Radar echo images showing the horizontal section of the tornado cloud during the May 3, 1999 Oklahoma tornadoes (Source NOAA)

In the low-level PPI radar image at right, radar echoes from the largest tornado that occurred during the tonic episode in Oklahoma on May 3, 1999 can be seen. The hook-shaped area is where the vortex is located. just to the left of the no-precipitation sector (top shot). One might note correspondence (Correspondence is usually an exchange of mail extending over a long period of time. The…) with theoretical diagrams:

  • The frontal precipitation kernel corresponds to the reduction of precipitation generated aloft by the airflow;
  • The posterior heart is associated with the lower flow of the midlevels.

whom’animation (Animation consists of giving the illusion of motion using a sequence of images. These images…) As the top of the article points out, these hooks have an expiration date life (Life is a given name 🙂 is limited. They depend on the balance between the currents in the cloud and the presence of rotation in this couplet. The boss can only last a few minute (The original form of the document: Law: minute one…is the original) weak tornadoes or more than one hour (An hour is a unit of time. The word also means magnitude…) in constant reformation for long-lived supercells.


Horizontal structure and vertical (A vertical is a straight line parallel to the direction of gravity, especially…) supercell storm seen by radar.

In the left part of the image on the left, we can see the horizontal structure of a low-level supercell storm. Areas included blue (Blue (from Old High German “blao” = bright) is one of the three colors…) it shows where it is in this pictureweather (Air is a mixture of gases that make up the Earth’s atmosphere. Odorless and…) descends in this type of cloud that gives winds to the ground. Areas in yellow indicate rising air. A section of reflectors in the vertical, right part a vaulted (A vault (or vault) is an architectural element of the interior covering of a house…) allows a strong updraft without echoeshumidity (Humidity is the presence of water or water vapor in the air or in a substance…) air parcels convection (Convection is a method of energy transfer that involves a motion…) only at a very high level of compaction. The latter is in the part that enters the cloud, and the precipitation is in the back part.

On the southern side, we observe that traffic (Traffic (Anglicism: traffic) is the movement of motor vehicles…) rotates between the blue area behind yellow (There are (at least) five definitions of the color yellow, which are roughly the same…) from the top project. Two currents enter communication (An interaction is an exchange of information, influence, or energy between two agents…) and this is where tornadoes can occur. Since the radar only records rain, this surrounds the low-level upstream sector behind and forms a hook.

This fork is not always visible in strong supercells precipitation (In meteorology, the term precipitation refers to ice crystals or…) (HP). The rain (Rain generally refers to water falling in a state…) of these tend to be lower in the upper draw and fill part of the hook. The shape is more like a kidney (The kidney has many functions (hormonal, blood pressure regulation, but above all…) In this case. Newer radars such as NEXRADs and these radars network (A computer network is a set of devices connected to each other to exchange information…) Get Canadian weather radars speed (We notice 🙂 instantaneous raindrops in addition to the precipitation rate. This data (In information technology (IT), data is an elementary description, often…) let `s note everything (The whole, understood as the whole of what exists, is often interpreted as the world or…) allows to fix poor detection of mesocyclone and fork in the storm.

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