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Mesocyclone

A mesocyclone is a storm-scale region of rotation, typically 2–6 miles (3–10 km) in diameter, consisting of a deep and persistent rotating updraft within a supercell thunderstorm.^[1] This cyclonically rotating vortex forms in convective storms and is characterized by significant vertical vorticity, distinguishing supercell thunderstorms from ordinary cellular convection.^[2]^[3] Mesocyclones are primarily detected using Doppler radar, which identifies rotation patterns through criteria such as azimuthal shear, vertical depth, and duration, often via algorithms like the WSR-88D Mesocyclone Detection Algorithm.^[1] They play a critical role in severe weather, as the strong rotation can stretch and intensify low-level vorticity, creating conditions favorable for tornado genesis, though not all mesocyclones produce tornadoes.^[1]^[4] In supercells, the mesocyclone often appears in the right rear flank relative to the storm's motion, contributing to the development of hook echoes on radar imagery.^[5] The formation of mesocyclones is driven by environmental factors including vertical wind shear, instability, and buoyancy, which sustain the rotating updraft against precipitation loading.^[6] Research indicates that mesocyclones are key precursors to the most destructive tornadoes, with studies emphasizing their quasi-steady nature and association with hail, heavy rain, and damaging winds in supercell environments.^[3]^[7]

Definition and Characteristics

Definition

A mesocyclone is defined as a cyclonically rotating vortex, around 2–10 km in diameter, within a convective storm, with associated vorticity in the range of 10^{-2} s^{-1} or greater.^[8] This rotation manifests as a deep, persistent updraft that distinguishes it as a key feature of severe weather, often spanning vertical depths of several kilometers and lasting 30 minutes or longer to meet observational criteria.^[9]^[10] As a mesoscale phenomenon, a mesocyclone operates on horizontal scales of 1–100 km, fitting within the broader meteorological classification of mesoscale convective systems while being smaller than synoptic-scale cyclones and larger than sub-mesoscale features like individual tornadoes, which typically measure under 1 km in diameter. This scale positions it as a storm-scale rotation, integral to the dynamics of thunderstorms but not encompassing the full storm structure.^[1] The term "mesocyclone" originated in the early 1970s among U.S. meteorologists at institutions like the National Severe Storms Laboratory, coined to describe rotations revealed by pioneering Doppler radar observations of thunderstorms.^[11]^[12] Its basic structure typically includes a mid-level mesocyclone centered at altitudes of 3–7 km above ground level, where the primary rotation develops, potentially accompanied by a low-level mesocyclone below 3 km that enhances near-surface wind shear. Mesocyclones most commonly occur within supercell thunderstorms, where the sustained rotation contributes to their severe potential.^[8]

Physical Properties

Mesocyclones typically exhibit horizontal diameters ranging from 3 to 10 kilometers, encompassing a meso-gamma scale region of organized rotation within severe thunderstorms.^[13] Their vertical extent often spans from near the surface up to altitudes of 10 to 15 kilometers, aligning with the depth of supercell updrafts that sustain the vortex.^[6] The rotation in mesocyclones features tangential wind speeds generally between 20 and 50 meters per second, with peak velocities contributing to the storm's rotational kinetic energy.^[14] The detectable rotation in radar observations typically persists for at least 10 minutes, with overall mesocyclone lifetimes often exceeding 30 minutes.^[15] Structurally, these vortices are often tilted with height due to wind shear, with the axis of rotation shifting from more vertical at mid-levels to increasingly inclined aloft.^[16] Intensity of mesocyclones is quantified using the Mesocyclone Strength Index (MSI) and associated strength ranks, as implemented in National Weather Service radar algorithms, where ranks from 1 to 25 (with higher values indicating stronger rotation) help classify weak to violent vortices based on shear magnitude and depth.^[10] Mesocyclones predominantly rotate cyclonically, counterclockwise in the Northern Hemisphere, accounting for approximately 90% of observed cases, while anticyclonic variants (clockwise rotation) are rarer and typically occur in mirror-image left-moving supercells.^[17]

Context in Thunderstorms

Role in Supercell Development

The mesocyclone serves as the defining characteristic of supercell thunderstorms, manifesting as a deep, persistent rotating updraft that sets supercells apart from other convective storms. This rotation arises from the tilting and stretching of environmental vorticity within the updraft, enabling the storm to maintain organization and longevity far beyond typical multicell or pulse storms.^[18] Supercells featuring mesocyclones are responsible for nearly all instances of very large hail and violent (EF4-EF5) tornadoes, underscoring their disproportionate impact on severe weather despite their relative rarity.^[18] Within the supercell lifecycle, the mesocyclone emerges prominently during the mature stage, where it drives key structural features such as the anvil overhang through updraft tilt and supports extensive hail production by suspending supercooled water droplets in a bounded weak echo region (BWER).^[18] As the storm evolves, the mesocyclone's sustained rotation persists for 1-4 hours, fueling the storm's deviation from linear propagation and promoting isolated development.^[18] This integration allows supercells to outlast non-rotating storms, often dominating local weather patterns.^[19] At the storm scale, the mesocyclone's rotation organizes airflow into distinct forward-flank and rear-flank downdrafts, which encircle and protect the main updraft from entrainment of dry air and precipitation, thereby preserving its intensity.^[18] This partitioning enhances updraft speeds exceeding 50 m/s in some cases, contributing to the supercell's overall vigor and potential for severe hazards.^[18]

Environmental Prerequisites

Mesocyclones typically form in environments characterized by high convective available potential energy (CAPE), with values exceeding 2000 J/kg providing the necessary buoyancy for robust updrafts that sustain rotation.^[20] Low lifted condensation levels (LCL) below 1500 m above ground level further favor development by allowing parcels to reach their level of free convection quickly, enhancing updraft intensity.^[21] Veering wind profiles with height, where winds shift clockwise from southeasterly at the surface to southwesterly aloft, generate storm-relative helicity (SRH) that supports persistent mesocyclonic rotation.^[22] Vertical wind shear is critical, particularly 0-6 km bulk shear greater than 15 m/s, which tilts horizontal vorticity generated by the veering winds into the vertical axis, amplifying rotation within the updraft.^[23] Abundant low-level moisture, indicated by surface dewpoints above 15°C (60°F), supplies the fuel for intense convection, while mid-level dry air promotes evaporative cooling in rear-flank downdrafts, helping to separate precipitation from the updraft and maintain storm organization.^[22]^[18] These conditions are most prevalent in the Great Plains of the United States, known as Tornado Alley, where synoptic patterns such as drylines—sharp boundaries between moist Gulf air and dry continental air—provide ideal lifting mechanisms and enhance low-level shear.

Formation Processes

Vorticity Dynamics

In mesocyclones, the initiation of rotation begins with the generation of horizontal vorticity, primarily through baroclinic processes driven by horizontal temperature gradients along boundaries such as gust fronts or drylines. These gradients create density contrasts that induce solenoidal circulations, producing horizontal vorticity aligned streamwise with the low-level inflow. For instance, in supercell environments, the forward-flank gust front often features sharp buoyancy gradients that generate vorticity magnitudes on the order of 10^{-2} s^{-1}, contributing to the rotational potential of the storm.^[24]^[25] This horizontal vorticity is then tilted into the vertical by the storm's updraft, transforming it into vertical vorticity that establishes initial mid-level rotation characteristic of the mesocyclone. The tilting occurs as inflow parcels ascend, reorienting vortex lines from horizontal to vertical orientations, typically at altitudes between 3 and 6 km where the updraft is strongest. This mechanism is fundamental to mesocyclone development, as it converts ambient shear into organized rotation without requiring initial vertical spin.^[26]^[27] The vertical component of vorticity, denoted as \zeta, is mathematically expressed in Cartesian coordinates as

\zeta = \frac{\partial v}{\partial x} - \frac{\partial u}{\partial y},

where u and v represent the zonal and meridional wind components, respectively. This initial spin-up manifests as weak rotation, often quantified by storm-relative helicity (SRH) exceeding 150 m²/s² in the low levels, which measures the potential for updraft-relative streamwise vorticity and is derived from environmental wind profiles. Environmental vertical wind shear provides the necessary background vorticity for these processes, enhancing the efficiency of baroclinic generation.^[28]^[29]

Updraft Interaction

The interaction between the thunderstorm updraft and the mesocyclone primarily involves vertical stretching of vorticity filaments, which amplifies the rotational intensity. As the updraft ascends, it draws in and elongates these vorticity elements, conserving angular momentum and thereby increasing the angular velocity \Omega according to the relation \Omega \propto \frac{1}{r^2}, where r is the radius of rotation.^[18]^[30] This stretching effect, often likened to an ice skater pulling in their arms, concentrates the rotation within a narrower column, typically strongest in the mid-levels where the updraft acceleration peaks.^[18] Initial vertical vorticity arises from the tilting of environmental horizontal vorticity into the updraft, setting the stage for this amplification.^[31] A positive feedback loop emerges as the intensifying rotation generates dynamic pressure reductions at the mesocyclone core, further bolstering the updraft. The cyclonic rotation produces centrifugal and curvature effects that lower the perturbation pressure, drawing in more air parcels and sustaining a tighter, more organized vortex.^[32]^[18] This enhanced updraft, in turn, promotes additional stretching and convergence, leading to smaller mesocyclone cores with intensified rotation. The loop maintains the mesocyclone's coherence until disrupted by broader storm dynamics. Over time, the mid-level mesocyclone, initially centered around 3-6 km above ground level, undergoes descent, narrowing and intensifying as it interacts with lower-level inflows. This downward migration, driven by the updraft's persistence and rear-flank downdraft influences, can spawn a distinct low-level mesocyclone near 1 km altitude, completing a full rotating column from mid- to low levels.^[26]^[18] Mesocyclones typically persist for 30-60 minutes, aligned with the updraft's lifecycle, before dissipation as the updraft weakens due to entrainment of drier environmental air or the incursion of cold outflow boundaries.^[33]^[18] Entrainment dilutes the updraft's buoyancy, while outflows from evaporatively cooled downdrafts disrupt the inflow, halting the stretching process and allowing the rotation to decay.^[18]

Detection Methods

Radar-Based Identification

Mesocyclones are primarily detected using Doppler radar systems, which measure radial velocities to identify rotational signatures in Doppler velocity data that reveal couplets of inbound (negative) and outbound (positive) winds on opposite sides of the circulation center. These couplets typically exhibit differential velocities exceeding 25 m/s, with peak tangential velocities around 25 m/s at a core radius of approximately 3 km, indicating cyclonic rotation in supercell thunderstorms.^[14] For a cyclonic mesocyclone, inbound winds appear on the left and outbound on the right relative to the radar's viewing direction, allowing forecasters to distinguish rotation from linear wind patterns.^[14] The Mesocyclone Detection Algorithm (MDA), integrated into the NEXRAD (WSR-88D) network, automates detection by applying pattern recognition to identify symmetric regions of azimuthal shear in Doppler velocity data across multiple elevation angles. Key thresholds include tangential shear of at least 14.4 per hour (high shear mode) or 7.2 per hour (low shear mode), angular momentum of at least 540 km² per hour (high) or 180 km² per hour (low), and features extending up to 8 km in height, with the mesocyclone base often at lower altitudes and the core typically between 3 and 7 km.^[34] The algorithm correlates two-dimensional shear features into three-dimensional rotations persisting over several radar volume scans, focusing on azimuthally coherent velocity changes that confirm mesocyclone presence without relying on reflectivity alone.^[34] Mesocyclone intensity is quantified using the Mesocyclone Strength Rank (MSR), a nondimensional index ranging from 0 (very weak) to 25 (exceptionally intense), assigned based on the strongest continuous vertical core of two-dimensional features. For MSR 3, the core must consist of features with a two-dimensional strength rank of at least 3, span at least 3 km in half-beamwidth depth, and have its base below 5 km above radar level, corresponding to moderate rotational shear often exceeding 30 m/s over gate-to-gate distances of several kilometers.^[35] Higher ranks, such as MSR 5 or above, indicate intense mesocyclones with deeper cores and greater shear, enhancing severe weather warning potential.^[35] Advancements in NEXRAD technology, including the 2010s dual-polarization upgrade, enable detection of tornadic debris signatures associated with mesocyclones by analyzing particle shape and orientation through differential reflectivity (ZDR) and correlation coefficient (CC), which reveal lofted non-meteorological debris in rotating updrafts.^[36] The New Mesocyclone Detection Algorithm (NMDA), introduced in 2019, improves upon the original MDA by incorporating azimuthal shear (AzShear > 0.006 s⁻¹), smoothed shear diameter (≥ 2 km), and velocity differences (≥ 5 km), reducing false alarms and better tracking circulations in real time.^[37] As of 2025, machine learning algorithms are being integrated to enhance predictions of mesocyclone intensity and associated tornado damage using radar velocity and strength data.^[38] Phased-array radar (PAR) implementations in the 2020s, such as NOAA's Advanced Technology Demonstrator, provide volume scans in under one minute—compared to 4-6 minutes for traditional NEXRAD—facilitating faster updates for mesocyclone evolution and supporting Warn-on-Forecast initiatives with higher-resolution data on storm rotation.^[39]

Observational Techniques

Observational techniques for mesocyclones extend beyond radar to include visual and in-situ methods, which provide complementary evidence of rotational features in supercell thunderstorms. Visual cues such as a persistent wall cloud—a localized, often abrupt lowering of the cloud base beneath the main updraft—serve as key indicators of mesocyclone presence, particularly when the wall cloud exhibits sustained rotation or rapid vertical motion.^[40] Additionally, a rotating base of the cumulonimbus cloud or striations—linear streaks of cloud or precipitation along the storm's flanks—can suggest underlying rotation, as these features arise from organized inflow and vorticity in the mesocyclone.^[40] These visual signs, while not definitive on their own, help spotters identify potential mesocyclones during field observations.^[7] In-situ measurements further aid detection by capturing low-level wind dynamics associated with mesocyclones. Mobile mesonets, consisting of instrumented vehicles equipped with ground-based anemometers, pressure, temperature, and humidity sensors, traverse near-storm environments to record surface wind shifts and convergence zones indicative of mesocyclone inflow.^[41] Radiosonde soundings, launched from mobile platforms or fixed sites in proximity to the storm, profile vertical wind variations, revealing low-level shear and directional changes that support mesocyclone development.^[9] These techniques provide direct thermodynamic and kinematic data, often validating indirect visual assessments. Storm chaser reports have historically played a vital role in mesocyclone documentation since the 1970s, when organized intercept programs began integrating visual observations with emerging radar data to confirm rotational structures.^[42] These efforts, including ground-based photography and time-lapse video, captured evolving cloud features like rotating updrafts, contributing to early understandings of supercell dynamics. Satellite imagery supplements such reports by detecting overshooting tops—dome-like protrusions above the anvil that signal intense updrafts linked to mesocyclones—offering broad-scale confirmation in data-sparse regions. Despite their utility, these non-radar techniques exhibit lower reliability for precise mesocyclone identification compared to radar velocity signatures, as visual and in-situ methods often capture only indirect effects of the rotation rather than the full three-dimensional structure.^[43] They are particularly valuable for confirmation in remote or radar-poor areas, where direct access allows for real-time environmental sampling.^[41]

Relation to Tornadoes

Tornadogenesis Mechanisms

Tornadogenesis typically begins with the intensification and descent of the mid-level mesocyclone to low levels near the surface, a process facilitated by the rear-flank downdraft (RFD).^[44] The RFD wraps around the mesocyclone, creating an occlusion signature that isolates a region of focused rotation within the updraft base.^[45] This occlusion enhances vertical stretching of vorticity as descending air parcels converge toward the ground, amplifying the rotational intensity and generating a low-level mesocyclone.^[45] The stretching mechanism reorients baroclinically generated horizontal vorticity from the RFD into vertical vorticity, which is critical for concentrating rotation sufficient to form a tornado.^[44] A key process in this descent is the dynamic pipe effect, where strong radial convergence at the base of the mesocyclone concentrates vorticity into a narrow vertical "pipe" aloft, drawing the vortex downward.^[46] This effect arises from the restriction of radial inflow by cyclostrophic balance, leading to progressive intensification of vorticity from mid-levels toward the surface.^[46] The circulation \Gamma, defined as the line integral \Gamma = \oint \mathbf{v} \cdot d\mathbf{l} around a closed path, increases due to this convergence; for a circular vortex with tangential velocity V, it simplifies to \Gamma = 2\pi r V.^[46] Numerical simulations indicate this descent can occur over approximately 18 minutes when buoyancy is concentrated mid-level, enabling the vortex to reach the surface and initiate tornadogenesis.^[46] Favorable environmental conditions significantly influence the likelihood of tornadogenesis from mesocyclones, including low lifted condensation level (LCL) heights (typically ≤ 1000 m) and storm-relative helicity (SRH) exceeding 300 m²/s² in the 0-3 km layer.^[44] Low LCL heights promote a warmer, more buoyant RFD that sustains low-level updrafts without excessive cooling, while high SRH provides ample low-level shear to generate and maintain intense rotation.^[23] These parameters are particularly critical for surface-based supercells, where they enhance the dynamic lifting necessary for vorticity amplification.^[44] Recent research (as of 2024) highlights additional factors like streamwise vorticity currents in the forward flank contributing to low-level mesocyclone development and tornadogenesis.^[47] In strong mesocyclones, tornado formation occurs in approximately 20-30% of cases, with average warning lead times of about 18 minutes after initial detection of the mesocyclone signature on radar.^[48]^[49] This brief timeline underscores the rapid evolution from mid-level rotation to surface touchdown, often marked by a sudden intensification of low-level winds.^[49]

Non-Tornadic Variants

Most mesocyclones, approximately 70-80% based on radar climatologies of supercell events, do not produce tornadoes and are classified as non-tornadic variants.^[50] These occur frequently in environments with weaker vertical wind shear, which limits the intensification of rotation necessary for tornadogenesis.^[9] Key failure modes in non-tornadic mesocyclones include insufficient low-level stretching of vorticity, often due to elevated lifting condensation levels (LCLs) (typically > 1000 m), which hinder the descent of the rotating updraft to the surface.^[23] Additionally, disruptions in the rear-flank downdraft (RFD), such as premature surges that occlude the mesocyclone and cut off inflow, prevent the concentration of angular momentum required for tornado formation.^[51] Despite lacking tornadoes, non-tornadic mesocyclones remain hazardous, commonly generating severe hail exceeding 2 inches in diameter and damaging straight-line winds over 58 mph (50 knots), though they do not produce tornadoes (surface vortices); funnel clouds may form without reaching the ground.^[9] Such variants are prevalent in marginal supercells across the Midwest United States, particularly during nocturnal hours when stable boundary layers further suppress low-level convergence and rotation amplification.^[3]

Mesoscale Convective Vortex

A mesoscale convective vortex (MCV) is a mid-level, warm-core cyclonic circulation that emerges as a remnant feature following the decay of mesocyclones within a mesoscale convective system (MCS), characteristically spanning 100–300 km in diameter and persisting for 12–24 hours or longer after the parent convection dissipates.^[52]^[53]^[54] This vortex typically forms in the mid-troposphere (around 3–6 km altitude) within the stratiform precipitation region of the MCS, where divergent outflow aloft and convergent inflow below create a favorable environment for rotational development.^[55] The formation of an MCV involves the aggregation and amplification of vorticity generated by multiple embedded mesocyclones during the mature stage of the MCS, with diabatic heating from latent heat release in the stratiform area stretching vertical vorticity into a coherent mesoscale feature.^[55]^[56] As the convective cells weaken, the mesocyclone-induced vorticity is redistributed and balanced by the Coriolis effect, leading to a quasi-geostrophic response that sustains the vortex independently of ongoing deep convection. MCVs exert significant meteorological impacts by modulating the local environment, often triggering renewed convection along their outflow boundaries or within their circulation, which can lead to additional heavy rainfall episodes and prolong the overall life cycle of precipitation events.^[55] They are frequently observed in MCSs across the central and eastern United States, with climatological analyses identifying them as a common outcome in systems featuring extensive stratiform coverage. Detection of MCVs relies on their subtler signatures compared to active mesocyclones, as they produce weaker rotational signals on conventional Doppler radar due to their elevated position and decoupled nature from surface features; instead, wind profilers and dual-Doppler radar networks are particularly effective for resolving the mid-level wind patterns and vorticity maxima.^[57] Satellite imagery can also reveal spiral cloud bands associated with the vortex, aiding in tracking its evolution post-MCS decay.^[55]

Comparisons to Other Rotational Features

Mesocyclones serve as parent circulations to tornadoes, featuring kilometer-scale rotations typically occurring at mid-levels within supercell thunderstorms, whereas tornadoes represent smaller-scale, surface-touching vortices on the order of tens to hundreds of meters in diameter that develop as concentrated extensions of this broader rotation.^[7]^[58] The mesocyclone's larger size, often 2–6 km in diameter, and its persistence driven by the storm's updraft distinguish it from the tornado's more intense but localized winds, which require additional low-level stretching for formation.^[1] In contrast to gustnadoes, which are shallow, short-lived whirlwinds forming as eddies along thunderstorm outflow boundaries in the planetary boundary layer, mesocyclones demand sustained deep updrafts and organized storm-scale rotation extending through much of the troposphere.^[59] Gustnadoes lack connection to cloud-base rotation or mesocyclonic circulations, remaining confined to near-surface levels with typical diameters under 100 m and durations of minutes, unlike the vertically extensive and radar-detectable structure of mesocyclones.^[60] Mesocyclones differ markedly from tropical cyclones in scale, embedding within individual convective storms as meso-gamma features (2–10 km diameter) with lifespans of minutes to hours, while tropical cyclones constitute synoptic-scale systems spanning hundreds to thousands of kilometers, originating over warm tropical waters with organized, surface-based circulations persisting for days.^[61] Tropical cyclones feature warm-core structures without fronts and rely on latent heat release across expansive rainbands, whereas mesocyclones arise from wind shear interactions in mid-latitude supercells, lacking the broad, symmetric organization of their larger counterparts.^[62] Early radar studies in the 1970s and 1980s often misidentified mesocyclone signatures as direct tornado indicators due to limited resolution and sampling, leading to overestimations of tornadic potential—initial research suggested up to 50% of mesocyclones produced tornadoes, but refined analyses in the 1990s and 2000s, including nationwide WSR-88D data, revised this to approximately 20–30% for mid-level detections, clarifying distinctions from surface vortices like "tight" low-level rotations. These confusions with compact, intense rotations were resolved through improved Doppler algorithms and multi-radar verification, emphasizing mesocyclones' role as precursors rather than equivalents to tornadoes.^[10]

References

[1]
Severe Weather 101: Tornado Detection
A mesocyclone is usually 2-6 miles in diameter, and is much larger than the tornado that may develop within it. NSSL researchers discovered the Tornado Vortex ...Missing: definition characteristics
[2]
Supercell Low-Level Mesocyclones: Origins of Inflow and Vorticity in
A defining characteristic of supercell thunderstorms is their mesocyclone, a quasi-steady region of vertical vorticity within the storm's updraft. This ...
[3]
The Future of Supercells in the United States in - AMS Journals
A supercell is distinguished from ordinary cellular convection by its deep, persistent mesocyclone, which is a storm-embedded, rotating vortex that has a ...
[4]
[PDF] Supercell low-level mesocyclones: Origins of inflow and vorticity
A defining characteristic of supercell thunderstorms is their mesocyclone, a quasi-steady region of vertical vorticity within the storm's updraft. This ...
[5]
Weather Glossary: M's - NOAA
Apr 17, 2023 · Mesocyclone - It is a sufficiently strong circulation detected on two or more elevation angles which are symmetrically linked within a ...
[6]
Severe Weather 101: Thunderstorm Types
A Mesoscale Convective System (MCS) is a collection of thunderstorms that act as a system. An MCS can spread across an entire state and last more than 12 hours.
[7]
Severe Weather 101: Tornado Basics
The most destructive tornadoes occur from supercells, which are rotating thunderstorms with a well-defined radar circulation called a mesocyclone.FAQ · Tornado Detection · Tornado Types · Tornado Forecasting
[8]
None
Nothing is retrieved...<|control11|><|separator|>
[9]
On the Environments of Tornadic and Nontornadic Mesocyclones
For very weak storm-relative, environmental winds, any low-level mesocyclones will occur early in the storm's life and will be short-lived, with the outflow ...
[10]
The National Severe Storms Laboratory Mesocyclone Detection ...
ABSTRACT. The National Severe Storms Laboratory (NSSL) has developed a mesocyclone detection algorithm (NSSL. MDA) for the Weather Surveillance Radar-1988 ...
[11]
MESOCYCLONE definition in American English - Collins Dictionary
[1970–75; meso- + cyclone]This word is first recorded in the period 1970–75. Other words that entered English at around the same time include: Heimlich ...<|control11|><|separator|>
[12]
History of Operational Use of Weather Radar by U.S. ... - AMS Journals
Using the PSI, the first mesocyclone detected by Doppler radar was recorded on 9 August 1968 (Donaldson et al. 1969). Donaldson (1970) investigated Doppler ...Missing: term | Show results with:term
[13]
Radar Signatures for Severe Convective Weather: Mid-level ...
A persistent Mid-level Mesocyclone signature indicates a strong and reasonably steady rotating updraft associated with a supercell. Generally, supercells can ...
[14]
4. interpretation of doppler velocity patterns within convective storms
Doppler velocity pattern (right) corresponding to two identical mesocyclones (peak tangential velocity is 25 m s-1 or 49 kt, core radius is 3 km or 1.6 n mi) ...Missing: periods tilt
[15]
Radar Signatures for Severe Convective Weather: Low-Level ...
A Low-Level Mesocyclone is a storm-scale, usually cyclonic circulation in the low levels of a thunderstorm that satisfies the mesocyclone definition.
[16]
VORTEX2 Observations of a Low-Level Mesocyclone with Multiple ...
The initially strong midlevel mesocyclone weakens and becomes more strongly tilted with height over the following five minutes, and by 2257 is characterized ...
[17]
Glossary - NOAA's National Weather Service
Nearly all mesocyclones and strong or violent tornadoes exhibit cyclonic rotation, but some smaller vortices, such as gustnadoes, occasionally rotate ...Missing: prevalence | Show results with:prevalence
[18]
[PDF] Supercell Thunderstorm Structure and Evolution
• In intense supercells, mid-level mesocyclone becomes strong enough to wrap precipitation around ... increases with height, which in turn can feed back ...Missing: altitude | Show results with:altitude
[19]
Severe Weather 101: Tornado Types
As few as 20 percent of all supercell thunderstorms actually produce tornadoes. Why does one supercell thunderstorm produce a tornado and another nearby ...
[20]
Sensitivities of Simulated Convective Storms to Environmental ...
When CAPE = 2000 J kg−1 or more, updrafts benefit from enhanced shear, higher levels of free convection, and reduced precipitable water. Strong low-level shear ...
[21]
Mesoscale Analysis Parameters
Anvil Level/9-11-km SR Winds (kts) The Anvil Level SR (Storm Relative) winds and SR winds from 9-11-km are meant to discriminate supercell type.Missing: rank | Show results with:rank
[22]
Env Parameters and Indices - National Weather Service
The EHI attempts to combine CAPE and S-R helicity into one index to assess the potential for supercell and mesocyclone development. ... Can get non-supercell/ ...
[23]
[PDF] Severe Weather Forecasting Tip Sheet
Storm-boundary interactions may not be necessary when the environmental shear is very large. Mergers: • Watch for cells merging into the inflow flank of ...Missing: formation | Show results with:formation
[24]
[PDF] 1 Tornado Dynamics Readings - twister.ou.edu
The low-level vortex lines depicted in Figures 12 and 13 further illustrate the baroclinic vorticity generation mechanism. Page 14. 14. Since the ...
[25]
Relation between Baroclinity, Horizontal Vorticity, and Mesocyclone ...
The baroclinic mechanism (also known as the solenoidal mechanism) generates horizontal vorticity ... generation and horizontal stretching of streamwise vorticity ...
[26]
A review of supercell and tornado dynamics - ScienceDirect.com
A classic supercell in its mature stage consists of a rotating updraft (mid-altitude mesocyclone) and a downdraft that coexists symbiotically with the updraft ...
[27]
[PDF] davies-jones, trapp, and bluestein - twister.ou.edu
This may take the form of downward transport of horizontal momentum, which is associated with tilting of existing horizontal vorticity toward the vertical (Wiin ...
[28]
Storm-Relative Helicity Revealed from Polarimetric Radar ...
Minimum SRH thresholds for mesocyclones have been reported at 157 m2 s−2 in observed storms (Davies-Jones et al. 1990) and 250 m2 s−2 for simulated supercells ( ...
[29]
[PDF] Effective Storm-Relative Helicity and Bulk Shear in Supercell ...
Feb 7, 2007 · The EBWD corresponds to the familiar 0–6-km bulk wind difference that is often referenced in operational forecast products originating from the ...
[30]
What we know and don't know about tornado formation
Sep 1, 2014 · In step 3, conservation of angular momentum amplifies the now vertical vorticity as air converges toward the axis of rotation while being ...
[31]
How tornadoes form – Markowski Research Group
The intensification occurs by way of the “figure-skater effect”—referred to by scientists as the conservation of angular momentum or vorticity stretching. A ...
[32]
The Role of Surface Drag in Mesocyclone Intensification Leading to ...
Larger vorticity within the stronger mesocyclone produces larger pressure deficits via the “spin” term of the dynamic pressure equation. Second, the reduced ...
[33]
[PDF] The Effect of Surface Drag Strength on Mesocyclone Intensification ...
May 1, 2020 · have more effectively induced a positive feedback of dynamic perturbation pressure falls aloft that gave rise to this robust updraft.
[34]
WOOD ET AL.
mesocyclone duration. The data suggest that a tornado-. (63%) farther and therefore lasts about 40 min (62%) producing mesocyclone typically travels about 30 km.
[35]
[PDF] MESOCYCLONE DETECTION ALGORITHM DESCRIPTION NX-DR ...
AZIMUTH and ELEVATION are obtained by direct measurement of the radar antenna pointing direction. VELOCITY (Doppler) is acquired by direct radar measurements.Missing: principles VAD
[36]
[PDF] increasing the usefulness of a mesocyclone climatology 5.4
The first technique employed to create a more meaningful data set involves filtering out these weak areas of rotation using the Mesocyclone Strength Rank (MSR).
[37]
Research Tools:Dual Polarized Radar
Examine dual-pol signatures ... Can help identify large hail and tornadic debris on radar displays, improving severe thunderstorm and tornado warnings.Missing: mesocyclone | Show results with:mesocyclone
[38]
[PDF] New Mesocyclone Detection Algorithm (NMDA)
NMDA is a new algorithm to modernize severe weather detection, using AzShear as main catalyst, to identify and track mesocyclones.
[39]
A CLEAR VISION: Phased Array Radar innovating for the future
Nov 14, 2024 · A revolutionary new weather radar being developed by NOAA's National Severe Storms Laboratory, offers faster updates, more accurate and detailed data and game- ...Missing: mesocyclone 2020s
[40]
[PDF] Features Indicating Strong/Severe Storms
Visual Clues of Supercells. ▫ Rotating wall cloud suggests the presence of a rotating updraft. ▫ Striations on the sides of the storm, streaks of cloud or ...
[41]
A Mobile Mesonet for Finescale Meteorological Observations in
The mobile mesonet instruments measure pressure (600–1100 mb), temperature (−33° to 48°C), relative humidity (0%–100%), and wind direction and speed (0°–360° ...
[42]
A History of Severe-Storm-Intercept Field Programs in - AMS Journals
The first organized storm-intercept (colloquially known as chase) programs dedicated to the study of severe convective storms and tornadoes in the plains of the ...
[43]
Observations of Nontornadic Low-Level Mesocyclones and ...
The study found that some storms with low-level mesocyclones did not produce tornadoes, showing that a mesocyclone is insufficient for tornadogenesis.
[44]
[PDF] METR 4403:5403 Tornadogenesis Lecture - twister.ou.edu
Apr 3, 2023 · It is pretty well agreed in current literature that the tornado vortex forms in the lower portions of the storm. • They proposed the tornado ...
[45]
Hook Echoes and Rear-Flank Downdrafts: A Review in - AMS Journals
During a 40-min period, two tornadoes grew and decayed within the mesocyclone. Wicker and Wilhelmson's Fig. 9 depicted a spiraling, asymmetric RFD associated ...
[46]
Tornadogenesis with and without a Dynamic Pipe Effect in
A dynamic pipe effect (DPE) has been used previously to explain the descent from aloft of tornadic vortex signatures (TVSs), and presumably embryonic tornadoes.Abstract · Introduction · Description of the model · Results
[47]
What is a mesocyclone and its impact on the Carolinas | wcnc.com
Apr 29, 2021 · A mesocyclone is a rotating part of a thunderstorm or more technically the storm-scale region of rotation. This area can range up to 2-6 miles.
[48]
Tornado Probability of Detection & Lead Time vs. Mode
Oct 1, 2013 · The PODs for supercells averaged between 80% and 88% with a median lead time of 13–15 min. The POD for nonsupercell storms varied between 44% ...
[49]
A Reassessment of the Percentage of Tornadic Mesocyclones in
In terms of height or altitude of mesocyclone base, 15% of midaltitude mesocyclone detections were tornadic, and more than 40% of low-altitude mesocyclone ...
[50]
[PDF] Tornadoes – forecasting, dynamics and genesis
Low-level rotation seems to require downdrafts, and there are 2 thunderstorm downdrafts to pay attention to: I) FFD (forward-flank-downdraft) marks the edge of ...
[51]
The Vertical Structure of Mesoscale Convective Vortices in
Typically 100–300 km in diameter, these vortices are several ... Mesoscale convective vortex formation in a weakly sheared moist neutral environment.
[52]
Vorticity Budget and Formation Mechanisms of a Mesoscale ... - MDPI
The mesoscale convective vortex (MCV) is one of the weather systems that can ... The diameter of an MCV is about 100–300 km [9]. The main part of an ...
[53]
Long-Lived Mesoconvective Vortices and Their Environment. Part II
... Mesoscale Convective Vortex and Associated Severe Weather Environment ... long periods (τ > 12–24 h). 4. Sensitivity to vertical shear and vortex ...
[54]
[PDF] MESOSCALE CONVECTIVE SYSTEMS
This feature is now called a ''mesoscale convective vortex'' or MCV. Bartels and Maddox [1991] compiled a satellite-based climatology of MCVs over the United ...
[55]
https://atmos.uw.edu/MG/PDFs/ROG04_houze_MCS.pdf
[56]
Mesoscale Convective Vortices Observed during BAMEX. Part I
Composite radar reflectivity images for mature MCSs at the time of MCV formation as deduced from radar reflectivity animations and wind profiler observations.
[57]
Glossary - NOAA's National Weather Service
Mesocyclone: (abbrev. MESO)- A storm-scale region of rotation, typically around 2-6 miles in diameter and often found in the right rear flank of a supercell ...Missing: AMS | Show results with:AMS
[58]
https://forecast.weather.gov/glossary.php?word=MESOCYCLONE
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[PDF] Glossary - NWS Training Portal
Gustnadoes are usually visualized by a rotating dust or debris cloud. Gustnadoes are not associated with storm-scale rotation (i.e. mesocyclones); they are ...<|separator|>
[60]
Hurricane and Tropical Cyclone Science - American Meteorological ...
A tropical cyclone is called a hurricane if it has maximum sustained wind speeds of at least 32 meters per second (roughly 64 knots/74 miles per hour) AND it ...
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