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Hook echo

A hook echo is a characteristic radar reflectivity pattern observed in supercell thunderstorms, appearing as a hook-shaped or pendant-like extension of the main precipitation echo, usually located on the right-rear flank of the storm relative to its direction of motion.^[1] This feature is produced by the wrapping of rain, hail, or even debris around a rotating updraft known as a mesocyclone, often signaling the presence of significant storm rotation.^[2] Hook echoes are a critical diagnostic tool in severe weather forecasting, as they frequently precede or accompany tornado development within supercell environments.^[3] The formation of a hook echo is primarily driven by the storm's rear-flank downdraft (RFD), a downdraft of cooler air on the backside of the thunderstorm that descends and interacts with the updraft, causing precipitation to curl around the mesocyclone in a cyclonic manner.^[3] This process creates the distinctive hook shape on Doppler radar images, where higher reflectivity values outline the appendage, sometimes accompanied by a "clear slot" or low-reflectivity area adjacent to it.^[1] While not every hook echo results in a tornado, its appearance prompts heightened vigilance from meteorologists, as it indicates conditions favorable for tornadogenesis, particularly in environments with strong wind shear and instability.^[2] Historically, hook echoes were first identified through conventional radar observations in the mid-20th century, but their interpretation advanced significantly with the deployment of Doppler radar systems in the 1990s, such as the NEXRAD network, which enhanced detection of rotational signatures.^[4] Today, they remain a cornerstone of tornado warning criteria issued by the National Weather Service, often integrated with velocity data to confirm mesocyclone rotation and debris signatures for real-time threat assessment.^[1]

Overview and Characteristics

Definition

A hook echo is a distinctive radar reflectivity pattern observed in supercell thunderstorms, appearing as a hook-shaped or pendant-like appendage extending from the rear flank of the main storm echo. This feature forms when precipitation particles, such as rain or hail, are advected around the storm's rotating updraft, known as a mesocyclone, creating a curved extension that wraps cyclonically behind the primary precipitation core.^[5]^[6] Hook echoes are characteristic of supercell thunderstorms, which are long-lived, rotating storms capable of producing severe weather, and they serve to differentiate these storms from non-rotating or multicell varieties. Unlike other radar signatures, such as the bounded weak echo region (BWER)—a doughnut-shaped area of reduced reflectivity surrounding the intense updraft—the hook echo specifically highlights the precipitation associated with the mesocyclone's rotation rather than a void in echoes. This association underscores the hook echo's role as an indicator of organized, persistent storm rotation.^[1]^[7] In terms of scale, a typical hook echo measures several kilometers in length, though its exact dimensions can vary based on storm intensity and environmental conditions. It is readily visible on conventional Doppler weather radar displays, where the curved extension stands out against the broader storm echo, often in the right-rear quadrant relative to the storm's motion.^[8]^[9]

Radar Appearance and Features

The hook echo appears on radar reflectivity imagery as a distinctive, curved appendage extending from the rear flank of a supercell's precipitation echo, often resembling a fishhook with a tight curl at its tip that highlights intense low-level rotation.^[10] This morphology typically manifests in the right-rear quadrant relative to the storm's motion, forming a pendant-like structure where precipitation particles are wrapped around the mesocyclone.^[5] The hook's attachment to the main echo may feature a pronounced "notch," an indentation marking the boundary between the rotating updraft and surrounding precipitation.^[11] Associated radar signatures enhance the hook echo's identification. An inflow notch often appears on the southeast flank, characterized by a concave indentation in reflectivity where low-level warm air inflows into the storm, contrasting with higher reflectivity areas.^[5] Above the hook, a weak echo vault—a region of low reflectivity or a "doughnut hole"—is evident at mid-levels, indicating the updraft's protection from precipitation fallout.^[12] During intense rotation, a debris ball may form at the hook's tip, appearing as a small, high-reflectivity core (often exceeding 50 dBZ) from lofted debris.^[13] A classic example is the hook echo observed during the 1999 Bridge Creek-Moore tornado in Oklahoma, captured by NEXRAD radar at the Twin Lakes site (KTLX), which displayed a well-defined, tightly curled appendage on the storm's southwest flank amid extreme reflectivity values exceeding 70 dBZ.^[14] This signature, detailed in post-event analyses, exemplified the hook's role in visualizing mesocyclone structure in a supercell thunderstorm.^[15]

Formation Mechanisms

Atmospheric Processes

The primary formation mechanism of the hook echo involves the rear-flank downdraft (RFD), a descending current of cool air that wraps precipitation around the mesocyclone's rotating updraft in supercell thunderstorms.^[1] This wrapping occurs due to horizontal wind shear at the interface between the storm's warm inflow and the cooler RFD outflow, which creates a cyclonic circulation that advects hydrometeors into a curved appendage on the radar echo.^[9] The RFD originates from evaporative cooling of precipitation and dynamic pressure perturbations, descending behind the main updraft and interacting with the low-level inflow to sculpt the hook shape.^[9] The mesocyclone's cyclonic rotation plays a central role in shaping the hook by shearing rain and hail into the appendage, with typical tangential velocities of approximately 20 m/s in the rotating updraft. This rotation generates vertical vorticity through the storm's internal dynamics, quantified by the relative vorticity equation \zeta = \frac{\partial v}{\partial x} - \frac{\partial u}{\partial y}, where u and v are the zonal and meridional wind components, respectively.^[3] The vorticity arises primarily from the tilting and stretching of environmental horizontal vorticity within the updraft, amplifying the low-level rotation that sustains the hook structure.^[3] Hydrometeors such as rain and hail interact with these processes by being advected horizontally by diverging winds at the edge of the updraft, forming the narrow, curved rain curtain characteristic of the hook. These particles, falling through the mesocyclonic circulation, are drawn into the RFD's outflow and wrapped around the rotation axis, enhancing the radar reflectivity appendage while the divergent flow at the surface contributes to the hook's pointed tip. This advection maintains the hook's integrity until occlusion disrupts the updraft-inflow interface.^[9]

Required Environmental Factors

The development of hook echoes in supercells requires specific large-scale atmospheric conditions that provide the necessary instability, shear, and moisture profiles for storm persistence and rotation. High convective available potential energy (CAPE), typically exceeding 2000 J/kg, supplies the buoyancy needed to sustain powerful updrafts within these storms.^[16] Strong vertical wind shear, particularly in the 0-6 km layer greater than 40 knots, organizes the storm's structure by promoting updraft tilting and separation from downdrafts, enabling the longevity essential for hook echo formation.^[17] Additionally, a low lifted condensation level (LCL) below 1000 m facilitates the ingestion of moist low-level air, which supports the development of tight rotation near the surface and enhances the potential for hook appendages to appear on radar.^[18] Synoptic-scale features often set the stage for these environments by creating focused zones of lift and shear. Hook echoes frequently form in association with dry lines, warm fronts, or outflow boundaries, where convergent airflow initiates convection in conditionally unstable air.^[19] Veering wind profiles, such as southerly flow at low levels transitioning to westerly winds in the mid-levels, contribute to storm-relative helicity that amplifies mid-level rotation, a precursor to the mesocyclone dynamics underlying hook structures.^[17] These favorable conditions are most prevalent in the Great Plains region, known as Tornado Alley, where the combination of ample instability from Gulf moisture and pronounced shear from upper-level westerlies routinely supports supercell development and associated hook echoes.^[20]

Historical Development

Early Discoveries

In the 1940s, prior to widespread radar use, meteorologists began documenting visual features of severe thunderstorms that suggested organized rotation. These early field observations, such as those during the U.S. Thunderstorm Project (1946–1947), provided initial clues to the structural complexity of tornadic storms, bridging to postwar radar advancements.^[21] E.M. Brooks made significant observations in 1949 by analyzing pressure and wind records from microbarographs near tornado paths, identifying larger-scale circulations—termed "tornado cyclones" with radii of about 8–16 km—that encompassed the tornadoes themselves. Brooks' work in Weatherwise highlighted these circulations as key to tornado genesis, laying groundwork for recognizing radar-detected hook appendages as indicators of such rotating features.^[22] A pivotal advancement came on April 9, 1953, when electrical engineer Donald Staggs inadvertently captured the first documented radar image of a hook echo during routine testing of a 3-cm wavelength radar at Willard Airport near Champaign-Urbana, Illinois. The hook-shaped reflectivity pattern, observed on a plan position indicator (PPI) scope, depicted a thunderstorm that produced an F3 tornado causing two fatalities and significant damage in the area. Subsequent detailed analysis by F.A. Huff, H.W. Hiser (often cited as Heiser), and S.G. Bigler confirmed the hook echo's direct association with the tornado's path, marking the transition from anecdotal visual reports to verifiable radar evidence of tornadic signatures. Their 1954 report emphasized the potential for radar-based warnings, influencing early severe weather monitoring efforts.^[23]^[24]

Key Scientific Studies

One of the earliest detailed analyses of hook echoes was conducted by Tetsuya Fujita in his 1958 mesoanalysis of the Illinois tornadoes that occurred on April 9, 1953.^[25] Using photogrammetric techniques on aerial photographs combined with radar data from the University of Illinois Weather Radar, Fujita examined the structure and evolution of hook-shaped appendages in the reflectivity echoes associated with multiple tornado-producing supercells.^[25] He identified that these hook echoes were linked to rotating mesocyclones within the storms, with the hook's curvature indicating cyclonic circulation around a central low-pressure area, where air converged at low levels and ascended along the echo's boundaries.^[25] This work provided foundational evidence that hook echoes signify organized rotation in severe thunderstorms, advancing the conceptual understanding of mesocyclone dynamics.^[25] Building on early radar observations, J.R. Fulks proposed a key hypothesis for hook echo formation in his 1962 report "On the Mechanics of the Tornado."^[26] Analyzing radar observations from a 1960 severe storm outbreak in central Oklahoma collected by the National Severe Storms Project, Fulks suggested that hooks arise from the interaction between a rear-flank downdraft (RFD) and the updraft-inflow boundary in environments of strong vertical wind shear.^[9] He described how a tall convective tower tilts due to shear, wrapping precipitation around the mesocyclone to form the hook appendage, with the RFD providing a descent mechanism that enhances the rotation.^[9] This model emphasized the role of downdraft-inflow dynamics in shaping hook structures, influencing subsequent theoretical frameworks for supercell evolution.^[9] The Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX) represented a major advancement through targeted field campaigns. VORTEX1, conducted from 1994 to 1995 across the central Plains, deployed mobile platforms including the prototype Doppler on Wheels (DOW) radar to probe hook echo regions in supercell thunderstorms.^[27] Researchers captured high-resolution dual-Doppler data revealing the three-dimensional wind fields within hooks, validating the RFD-mesocyclone interaction by mapping vorticity couplets and precipitation patterns associated with tornadogenesis. These observations confirmed that hook echoes often enclose intense low-level rotation driven by updraft tilting and stretching. VORTEX2, executed from May to June 2009 and 2010 with an expanded fleet of DOW radars and other mobile mesonet tools, provided even finer-scale validation of hook echo dynamics. The campaigns produced detailed 3D mappings of hook structures in multiple supercells, such as the 2010 Dumas, Texas, event, showing how rear-flank downdrafts surge into the hook to intensify mesocyclone rotation through momentum redistribution.^[28] By integrating rapid-scan radar volumes with in-situ measurements, VORTEX2 datasets substantiated the conceptual models of hook formation, highlighting the spatial variability of wind shear and buoyancy within these features.^[28]

Forecasting Significance

Role in Tornado Detection

Hook echoes serve as a primary radar signature for detecting potential tornadoes, enabling meteorologists at the National Weather Service (NWS) to identify supercell thunderstorms with heightened risk of tornadogenesis. When observed in conjunction with Doppler radar velocity data revealing rotational couplets indicative of a mesocyclone, a hook echo prompts the issuance or escalation of tornado warnings, often providing lead times of 10-15 minutes or more. This combination enhances warning accuracy, as the hook's appearance signals the wrapping of precipitation around a rotating updraft, a process linked to the rear-flank downdraft in supercells.^[1]^[29] The predictive value of hook echoes stems from their strong association with mesocyclones, which are rotating storm features that precede many tornadoes. Studies indicate that hook echoes are present in a majority of mesocyclone cases, with research showing that approximately 29% of hook echoes are followed by tornado formation, though false alarms occur in the remaining instances due to varying storm dynamics. The NWS incorporates these signatures into operational protocols, prioritizing warnings for storms exhibiting both reflectivity hooks and velocity-based rotation to balance timeliness and reliability. Modern tools like the New Tornado Detection Algorithm (NTDA), developed by NOAA's National Severe Storms Laboratory, further integrate hook echoes with velocity and other data to provide probabilistic tornado forecasts, improving detection as of 2023.^[1]^[30] Hook echoes are commonly observed in significant tornadoes rated EF2 or stronger, emphasizing their relevance for forecasting more destructive events, though not all significant tornadoes display hooks due to factors like storm evolution or radar resolution.^[1] Prominent case examples illustrate the hook echo's role in real-time detection. During the 1999 Bridge Creek-Moore F5 tornado in Oklahoma, a well-defined hook echo on NEXRAD radar at 6:51 PM CDT facilitated an early warning, allowing evacuations that limited fatalities despite the storm's extreme winds exceeding 300 mph.^[31]^[15] Likewise, the 2013 El Reno EF3 tornado exhibited a robust hook echo with an accompanying debris ball on dual-polarization radar, verifying the tornado's width over 2 miles and intensity, which informed urgent warnings amid the storm's rapid intensification.^[32]

Associated Phenomena

Hook echoes frequently co-occur with other radar signatures in supercell thunderstorms, enhancing their diagnostic value for severe weather. On velocity scans, they often align with tornado vortex signatures (TVS), which indicate intense low-level rotation through tight couplets of inbound and outbound velocities near the hook's tip.^[33] In reflectivity data, hook echoes are commonly adjacent to high-reflectivity hail cores in the storm's forward flank, where values exceeding 50 dBZ signal significant hail production within the updraft region.^[34] Additionally, hook structures may precede or accompany rear-inflow jets, which descend through the rear-flank downdraft (RFD) to invigorate the storm's circulation, as well as overshooting tops that mark vigorous updrafts penetrating the tropopause.^[9]^[35] Not all hook echoes lead to tornadoes; the majority do not result in tornadic development, often due to storm occlusion, where the RFD surges forward and disrupts the low-level updraft, or to insufficient low-level shear, which fails to stretch and intensify the mesocyclone's rotation to the surface.^[36] In such scenarios, the hook echo may weaken as precipitation wraps around a decaying circulation, reducing the overall storm threat but still warranting monitoring for residual hazards. Beyond direct rotation, hook echoes signify advanced supercell organization, where persistent mesocyclonic rotation sustains a structured inflow-outflow balance. This configuration can produce damaging straight-line winds from the RFD or embedded gust fronts, as well as large hail from the robust updraft, even absent tornado intensification.^[35]^[37] Such features underscore the hook's role in broader severe weather contexts, including environments with moderate instability and veering winds that favor non-tornadic supercell hazards.

Observational Challenges

Detection Limitations

One significant limitation in detecting hook echoes arises from precipitation masking, particularly in high-precipitation (HP) supercells, which are prevalent in humid environments such as the Southern United States where heavy rain and hail often fill the hook region, obscuring the signature on radar reflectivity images.^[7]^[38] In these storms, the dense precipitation drawn into the mesocyclone circulation reduces the visibility of the hook appendage, making it harder to distinguish from surrounding echoes compared to classic low-precipitation supercells.^[38] Resolution constraints further complicate hook echo detection, especially with pre-2008 NEXRAD systems where the beam width of approximately 1 degree resulted in cross-range resolutions of about 1 km at close ranges (e.g., 50-60 km), often blurring small-scale hook features.^[39] Additionally, ground clutter from non-meteorological targets and beam blockage by complex terrain, such as mountains, can hide low-level hook echoes by contaminating or blocking radar returns in the storm's rear flank.^[40]^[41] These issues are exacerbated at greater distances, where beam broadening averages out fine details.^[41] Hook echoes are also prone to false positives, as similar hook-like shapes can form from mergers of non-rotating storm cells or radar artifacts, such as sidelobe contamination, without indicating true rotation; confirmation typically requires dual-polarization or velocity data to verify mesocyclonic couplets.^[42] Studies have shown that hook echoes have a false alarm rate of 52-71% for tornado production, depending on the verification timeframe (instantaneous or within 30 minutes), underscoring the need for multi-parameter analysis to avoid misinterpretation.^[42]

Technological Advancements

The evolution of the Next Generation Weather Radar (NEXRAD) network has significantly enhanced the detection and analysis of hook echoes through key upgrades. In 2008, the WSR-88D radars received a super-resolution upgrade as part of Build 10, improving spatial resolution to 0.5-degree azimuthal by 250-meter range gates for reflectivity data up to 460 km, which better delineates small-scale features like hook appendages that were previously obscured by coarser 1-km resolution.^[43]^[44]^[45] This improvement has proven particularly valuable for identifying hook echoes in supercell thunderstorms, allowing forecasters to more accurately resolve their curvature and association with mesocyclones.^[46] Further advancements came with the dual-polarization upgrade, rolled out from 2011 to 2013 across the NEXRAD network, which added the ability to transmit and receive both horizontal and vertical radar pulses.^[47]^[48] This capability introduced products like differential reflectivity (ZDR), which measures the shape of hydrometeors, and correlation coefficient (CC or ρhv), which indicates particle uniformity. In hook echo regions, low ZDR and CC values help distinguish rain from non-meteorological debris lofted by tornadoes, confirming tornadic activity even when visibility is low.^[49]^[50] Mobile and supplemental radar systems have complemented fixed-site NEXRAD by providing finer-scale observations during intensive field campaigns. The Doppler on Wheels (DOW) radars, deployed during the Verification of the Origins of Rotation in Tornadoes Experiment 2 (VORTEX2) in 2009-2010, offered high-resolution scans with range gates as fine as 25-50 meters, enabling detailed mapping of hook echo structures and low-level inflows in supercells.^[51]^[52] More recently, Phased Array Radar (PAR) systems, under experimental testing by NOAA as of 2025, support rapid volumetric scans updating every 30-60 seconds, improving the tracking of hook echo evolution and tornado genesis in real time.^[53]^[54] Integrations of multi-Doppler networks with artificial intelligence have further advanced real-time hook echo analysis. NOAA's Warn-on-Forecast (WoF) system, operational in experimental form from 2023 to 2025, employs ensemble modeling and machine learning for pattern recognition, identifying hook echo signatures and predicting tornadic potential up to two hours in advance.^[55]^[56]

References

[1]
Severe Weather 101: Tornado Detection
A “hook echo” describes a pattern in radar reflectivity images that looks like a hook extending from the radar echo, usually in the right-rear part of the ...
[2]
Glossary - NOAA's National Weather Service
Hook Echo. A radar reflectivity pattern characterized by a hook-shaped extension of a thunderstorm echo, usually in the right-rear part of the storm (relative ...
[3]
Severe Weather 101: Tornado Basics
The rear flank downdraft is the motion in the storm that causes the hook echo feature on radar. A condensation funnel is made up of water droplets and ...Tornado Detection · FAQ · Tornado Types · Tornado Forecasting
[4]
Introducing NEXRAD - National Weather Service Heritage - Virtual Lab
Jan 5, 2020 · This distinctive hook-shape is produced sometimes by conventional radar signals reflected from swirling raindrops inside a storm. Within minutes ...
[5]
Weather Glossary for Storm Spotters
Hook (or Hook Echo) - A radar reflectivity pattern characterized by a hook-shaped extension of a thunderstorm echo, usually in the right-rear part of the ...
[6]
[PDF] Glossary - NWS Training Portal
Hook Echo. A radar signature characterized by a curve-shaped band of reflectivity echo caused when precipitation is drawn into the spiral of a mesocyclone. The ...
[7]
What is a Supercell? - National Weather Service
Radar features may include the presence of a hook echo, a weak echo region (WER), a bounded weak echo region (BWER), and a V-notch. Low-level storm features ...
[8]
Glossary of Weather Terms - National Weather Service
Hook echo - A radar pattern sometimes observed in the southwest (right, rear) quadrant of a tornadic thunderstorm. The rain echo forms the hook pattern as ...
[9]
Hook Echoes and Rear-Flank Downdrafts: A Review in - AMS Journals
Based largely on the work by Barnes (1978a,b), Lemon and Doswell inferred that the RFD typically originated between 7–10 km on the relative upwind side of the ...
[10]
https://forecast.weather.gov/glossary.php?word=hook
[11]
Applied Performance Drills: Convective Mode
Hook Echo. A radar signature characterized by a curve-shaped band of ... Inflow Notch. A radar signature characterized by an enhanced, low-level, concave ...
[12]
NWS Weather Radar
Hook Echoes/Debris Ball Signatures: A hook echo is a pendant or hook-shaped weather radar signature as part of a supercell thunderstorm. It is found in the ...Missing: visual morphology inflow notch
[13]
NWS Doppler Radar Dual Pol - Tornado Debris
This is dual pol's depiction of a "debris ball" at the location of the tornado, i.e., various debris caught within and rotating around the tornado, and lifted ...Missing: visual morphology features inflow notch vault
[14]
May 3, 1999 Oklahoma/Kansas Tornado Outbreak
May 3, 1999 NEXRAD radar image. Doppler reflectivity: A National Weather Service NEXRAD radar image of central Oklahoma at 7:00 pm on May 3rd shows four ...
[15]
Radar Observations of the 3 May 1999 Oklahoma City Tornado in
Because the DOWs were very close to the tornado, the radar data depict the hook echo in great detail (Fig. 2). At some intermediate elevation angles in the ...
[16]
On the Environments of Tornadic and Nontornadic Mesocyclones
The environments are characterized by moderate to high CAPE (more than 2000 J kg- 1) and significant low-level hodograph curvature leading to high helicity ( ...
[17]
[PDF] Severe Weather Forecasting Tip Sheet
Vertical Wind Shear & SRH. • 0-6 km bulk shear > 40 kts – supercells. • 0-6 km bulk shear 20-35 kts – organized multicells. • 0-6 km bulk shear < 10-20 kts ...
[18]
Close Proximity Soundings within Supercell Environments Obtained ...
A sample of 413 soundings in close proximity to tornadic and nontornadic supercells is examined. The soundings were obtained from hourly analyses.Data and methodology · RUC-2 sounding error... · Supercell and tornado forecast...
[19]
[PDF] On the Relationship of Cold Pool and Bulk Shear Magnitudes on ...
Aug 9, 2021 · A front, dry line, or outflow boundary was present within 100 km of the initiating convection in 12 of the 15 non-MCS cases and in 14 of the 15 ...
[20]
Is tornado frequency increasing in parts of the U.S.?
Tornado frequencies are changing across the United States. Their findings include a decrease in the traditional "Tornado Alley" of the Great Plains and an ...Missing: hook echo
[21]
The Thunderstorm Project - AMS Journals
The earliest published report of TSP plans was by. Byers et al. (1946). In that brief report we find: "We will make measurements in thunderstorms by means of ...
[22]
Severe Convective Storms: A Brief History of Science and Practice
Brooks, E.M., 1949: The tornado cyclone. Weatherwise, 12, 32–33. Article ... Sirmans, 1971: Preliminary Doppler velocity measurements in a developing radar hook ...
[23]
History of Operational Use of Weather Radar by U.S. ... - AMS Journals
The storm was reported by Stout and Huff (1953) and later analyzed in detail by Huff et al. (1954). Within two months, two more hook-shaped echoes ...
[24]
[PDF] Illinois Tornadoes
A hook-shaped echo, viewed on a 3-centimeter. PPI radar, was associated with a confirmed sighting of a tornado in central Illinois. (Huff et al., 1954). This ...
[25]
mesoanalysis of the illinois tornadoes of 9 april 1953
DEVELOPMENT OF TORNADO RELATED ECHO OF APRIL 9, 1953. 201705. 1708. 1709. -031 ... Illinois tornado using radar, synoptic weather and field survey data ...
[26]
[PDF] NOAA Technical Memorandum ERL NSSL-81
Radial-height distributions of mean tangential. (Vt), radial (vr), and vertical (w) wind during early mesocyclone development (1515 CST). Positive velocities (m ...
[27]
VORTEX-95 | Earth Observing Laboratory
VORTEX1 took place from 1 April to 15 June in 1994 (VORTEX-94) and 1995 (VORTEX-95) ... It was equipped with a Doppler radar, a variety of cloud physics ...Missing: hook echo Wheels
[28]
[PDF] vortex2 - Flexible Array of Radars and Mesonets (FARM)
The first detailed three-dimensional maps of the winds in tornadoes were obtained by the prototype Doppler on Wheels (DOW) mobile radar. These three-dimensional ...
[29]
Glossary - NOAA's National Weather Service
Hook Echo: A radar reflectivity pattern characterized by a hook-shaped extension of a thunderstorm echo, usually in the right-rear part of the storm ...
[30]
On the Reliability of Hook Echoes as Tornado Indicators
### Summary of Hook Echo Reliability for Tornado Production
[31]
https://www.weather.gov/oun/events-19990503
[32]
The Great Plains Tornado Outbreak of May 3-4, 1999
On May 3, 1999, multiple supercell thunderstorms produced many large and damaging tornadoes in central Oklahoma during the late afternoon and evening hours.
[33]
The May 31-June 1, 2013 Tornado and Flash Flooding Event
May 31, 2013 · The second tornado, labeled the "El Reno Tornado" to form would go on to be one of the most powerful tornadoes sampled by mobile radar and also ...
[34]
Keys_Radar1 - National Weather Service
In the velocity image below taken at the same time as the reflectivity image, a TVS (Tornado Vortex Signature) is noted clearly associated with the hook echo ...
[35]
NWS Radar Base Reflectivity 4-Panel
In the upper left panel, a classic supercell is shown at 0.5 degree elevation, with very heavy rain and hail in the storm's core, and a hook echo and "debris ...Missing: visual morphology features inflow notch vault
[36]
[PDF] Supercell Thunderstorm Structure and Evolution
Supercell tornadoes occur in hook area. Supercell Characteristics: Hook Echo. Debris ball: Tornado on ground. Page 10. • Forms from water loading (dragging cool ...
[37]
Analysis of a Nontornadic Storm during VORTEX 95 in - AMS Journals
9b reveals that precipitation particles that comprise part of the hook echo are now within the inflow region and encircle the mesocyclone. ... low-level shear ...
[38]
[PDF] Supercell Radar Signatures
Supercell radar signatures include hook echoes, low-level hook, bounded weak echo, and tornado vortex signatures (TVS) indicating cyclonic motion.
[39]
1.4.6 The structure of supercells - ESTOFEX
This is caused by the fact that precipitation (rain and hail) is drawn into the circulation of the mesocyclone. The hook-echo is not very well visible when the ...
[40]
https://www.weather.gov/media/abq/LocalStudies/TornadoDetection.pdf
[41]
[PDF] Tornado Detection Capabilities and Limitations
Technically, radar shows larger shear zones, not the actual tornado. • Base reflectivity shows hook echo due to precipitation thrown out of/around.
[42]
[PDF] Tornado es - Mesonet
This causes some features such as hook echoes to be less identifiable (or not present at all) at farther distances from the radar.
[43]
On the Reliability of Hook Echoes as Tornado Indicators
only 29% of the echoes produce tornadoes and the false alarm rate is 71% (instantaneous verification). Within 30 min, 48% of the distinctive echoes be- came ...
[44]
[PDF] 6b.1 nexrad product improvement – update 2008
These system upgrades enable the operational implementation of new scientific applications, and signal processing techniques to improve the radar data quality ...Missing: hook | Show results with:hook
[45]
NOAA Next Generation Radar (NEXRAD) Level 3 Products
Jul 11, 2025 · The upgraded Super Resolution data provides radar reflectivity at 0.5 degree azimuthal by 250 m range gate resolution to a range of 460 km, and ...Missing: hook | Show results with:hook
[46]
NOAA Next Generation Radar (NEXRAD) Level 2 Base Data
Sep 30, 2025 · During 2008, the WSR-88D radars were upgraded to produce increased spatial resolution data, called Super Resolution.
[47]
Radar Tutorial - weatherTAP
It also allows the ability to locate certain weather phenomena such as gust fronts and hook echoes that can be hard to see with the Level III data. ... Data ...
[48]
NOAA's National Weather Service completes Doppler radar upgrades
Apr 25, 2013 · Dual-pol can also spot airborne debris giving forecasters the ability to confirm a tornado on the ground, even in the dark or when hidden by ...Missing: CC hook echo<|separator|>
[49]
Key Advances in Weather History: Dual-Pol Radar - NOAA VLab
Jan 15, 2020 · Upgrades of the 88Ds to the dual-pol technology began the following year, in 2011, and all systems were updated by 2013.Missing: timeline | Show results with:timeline
[50]
[PDF] 2012: Dual-Polarization Tornadic Debris Signatures Part I
In addition to ρhv, ZDR can also be useful for tornadic debris detection. ZDR is a measure of the reflectivity-weighted oblateness of scatterers in a radar ...Missing: NEXRAD 2011-2013
[51]
[PDF] HOW THE WSR-88D AND ITS NEW DUAL POLARIZATION ...
Velocity product indicate possible tornado (note hook echo and velocity couplet in circle). Dual polarization data (low ZDR and. CC values in circle on right) ...
[52]
Rapid-Scan DOW radar observations of tornadoes during VORTEX2 ...
Sep 27, 2011 · Range resolution as fine as 25 m is possible with short pulses and radar gating. This capability makes the rapid-scan DOW ideally suited to ...
[53]
VORTEX2 Vehicles and Instruments
The OK-LMA detects and measures all types of lightning including flashes inside clouds. The 11-station OK-LMA provides high-resolution 3-D mapping of all types ...Missing: 2009-2010 hook echo
[54]
Experimental Phased Array Radar captures wildfire data - Inside NSSL
Apr 3, 2025 · This rapid update capability enhances forecasters' ability to monitor evolving storms, track tornado development, and improve severe weather ...
[55]
Phased Array Radar innovating for the future | NOAA Climate.gov
Nov 23, 2024 · Phased Array Radar can give meteorologists a clearer view of fast moving weather systems by providing almost instantaneous scans of multiple areas in the ...
[56]
THE WARN-ON-FORECAST SYSTEM: A Weather ... - Inside NSSL
May 29, 2024 · The Warn-on-Forecast System uses computer modeling to provide longer lead times for severe weather warnings, bridging the gap between watches ...Missing: 2023-2025 AI hook echo Kansas EF2
[57]
[PDF] Classifying Convective Storms Using Machine Learning
We demonstrate that machine learning (ML) can skillfully classify thunderstorms into three categories: supercell, part of a quasi-linear convective system, ...Missing: setups | Show results with:setups
[58]
March 13, 2024 Tornadoes - National Weather Service
Mar 13, 2024 · On March 13, 2024, two EF-2 tornadoes occurred: one near Alta Vista (8.8 miles, 115 mph winds) and one near Rossville (4.7 miles, 120 mph winds ...<|control11|><|separator|>
[59]
File:NEXRAD radar of an EF2 tornado in Kansas on March 13, 2024 ...
Mar 13, 2024 · At this exact moment, the NEXRAD radar is scanning the tornado at a height of 650 feet (220 yd; 200 m) and it measured the tornado vortex ...