Lecture 26: Tornadoes I
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A Study of Synoptic-Scale Tornado Regimes
Garner, J. M., 2013: A study of synoptic-scale tornado regimes. Electronic J. Severe Storms Meteor., 8 (3), 1–25. A Study of Synoptic-Scale Tornado Regimes JONATHAN M. GARNER NOAA/NWS/Storm Prediction Center, Norman, OK (Submitted 21 November 2012; in final form 06 August 2013) ABSTRACT The significant tornado parameter (STP) has been used by severe-thunderstorm forecasters since 2003 to identify environments favoring development of strong to violent tornadoes. The STP and its individual components of mixed-layer (ML) CAPE, 0–6-km bulk wind difference (BWD), 0–1-km storm-relative helicity (SRH), and ML lifted condensation level (LCL) have been calculated here using archived surface objective analysis data, and then examined during the period 2003−2010 over the central and eastern United States. These components then were compared and contrasted in order to distinguish between environmental characteristics analyzed for three different synoptic-cyclone regimes that produced significantly tornadic supercells: cold fronts, warm fronts, and drylines. Results show that MLCAPE contributes strongly to the dryline significant-tornado environment, while it was less pronounced in cold- frontal significant-tornado regimes. The 0–6-km BWD was found to contribute equally to all three significant tornado regimes, while 0–1-km SRH more strongly contributed to the cold-frontal significant- tornado environment than for the warm-frontal and dryline regimes. –––––––––––––––––––––––– 1. Background and motivation As detailed in Hobbs et al. (1996), synoptic- scale cyclones that foster tornado development Parameter-based and pattern-recognition evolve with time as they emerge over the central forecast techniques have been essential and eastern contiguous United States (hereafter, components of anticipating tornadoes in the CONUS). -
The Generation of a Mesoscale Convective System from Mountain Convection
JUNE 1999 TUCKER AND CROOK 1259 The Generation of a Mesoscale Convective System from Mountain Convection DONNA F. T UCKER Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas N. ANDREW CROOK National Center for Atmospheric Research Boulder, Colorado (Manuscript received 18 November 1997, in ®nal form 13 July 1998) ABSTRACT A mesoscale convective system (MCS) that formed just to the east of Denver is investigated with a nonhy- drostatic numerical model to determine which processes were important in its initiation. The MCS developed from out¯ow from previous convective activity in the Rocky Mountains to the west. Model results indicate that this out¯ow was necessary for the development of the MCS even though a convergence line was already present in the area where the MCS developed. A simulation with a 3-km grid spacing more fully resolves the convective activity in the mountains but the development of the MCS can be simulated with a 6.67-km grid. Cloud effects on solar radiation and ice sedimentation both in¯uence the strength of the out¯ow from the mountain convection but only the ice sedimentation makes a signi®cant impact on the development of the MCS after its initiation. The frequent convective activity in the Rocky Mountains during the warm season provides out¯ow that would make MCS generation favorable in this region. Thus, there is a close connection between mountain convective activity and MCS generation. The implications of such a connection are discussed and possible directions of future research are indicated. 1. Introduction scale or mesoscale. Forced lifting always occurs on the windward side of mountains; however, the mechanisms Mesoscale convective systems (MCSs) commonly de- that promote lifting on the downwind side of mountains, velop in the central United States during the warm sea- where a large proportion of MCSs initiate, are not as son, accounting for 30%±70% of the summer precipi- obvious. -
The Impact of Outflow Environment on Tropical Cyclone Intensification And
VOLUME 68 JOURNAL OF THE ATMOSPHERIC SCIENCES FEBRUARY 2011 The Impact of Outflow Environment on Tropical Cyclone Intensification and Structure ERIC D. RAPPIN Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, Miami, Florida MICHAEL C. MORGAN AND GREGORY J. TRIPOLI University of Wisconsin—Madison, Madison, Wisconsin (Manuscript received 3 October 2008, in final form 5 June 2009) ABSTRACT In this study, the impacts of regions of weak inertial stability on tropical cyclone intensification and peak strength are examined. It is demonstrated that weak inertial stability in the outflow layer minimizes an energy sink of the tropical cyclone secondary circulation and leads to more rapid intensification to the maximum potential intensity. Using a full-physics, three-dimensional numerical weather prediction model, a symmetric distribution of environmental inertial stability is generated using a variable Coriolis parameter. It is found that the lower the value of the Coriolis parameter, the more rapid the strengthening. The lower-latitude simulation is shown to have a significantly stronger secondary circulation with intense divergent outflow against a com- paratively weak environmental resistance. However, the impacts of differences in the gradient wind balance between the different latitudes on the core structure cannot be neglected. A second study is then conducted using an asymmetric inertial stability distribution generated by the presence of a jet stream to the north of the tropical cyclone. The initial intensification is similar, or even perhaps slower, in the presence of the jet as a result of increased vertical wind shear. As the system evolves, convective outflow from the tropical cyclone modifies the jet resulting in weaker shear and more rapid intensification of the tropical cyclone–jet couplet. -
Kármán Vortex Street Energy Harvester for Picoscale Applications
Kármán Vortex Street Energy Harvester for Picoscale Applications 22 March 2018 Team Members: James Doty Christopher Mayforth Nicholas Pratt Advisor: Professor Brian Savilonis A Major Qualifying Project submitted to the Faculty of WORCESTER POLYTECHNIC INSTITUTE in partial fulfilment of the requirements for the degree of Bachelor of Science This report represents work of WPI undergraduate students submitted to the faculty as evidence of a degree requirement. WPI routinely publishes these reports on its web site without editorial or peer review. For more information about the projects program at WPI, see http://www.wpi.edu/Academics/Projects. Cover Picture Credit: [1] Abstract The Kármán Vortex Street, a phenomenon produced by fluid flow over a bluff body, has the potential to serve as a low-impact, economically viable alternative power source for remote water-based electrical applications. This project focused on creating a self-contained device utilizing thin-film piezoelectric transducers to generate hydropower on a pico-scale level. A system capable of generating specific-frequency vortex streets at certain water velocities was developed with SOLIDWORKS modelling and Flow Simulation software. The final prototype nozzle’s velocity profile was verified through testing to produce a velocity increase from the free stream velocity. Piezoelectric testing resulted in a wide range of measured dominant frequencies, with corresponding average power outputs of up to 100 nanowatts. The output frequencies were inconsistent with predicted values, likely due to an unreliable testing environment and the complexity of the underlying theory. A more stable testing environment, better verification of the nozzle velocity profile, and fine-tuning the piezoelectric circuit would allow for a higher, more consistent power output. -
Polarimetric Radar Characteristics of Tornadogenesis Failure in Supercell Thunderstorms
atmosphere Article Polarimetric Radar Characteristics of Tornadogenesis Failure in Supercell Thunderstorms Matthew Van Den Broeke Department of Earth and Atmospheric Sciences, University of Nebraska-Lincoln, Lincoln, NE 68588, USA; [email protected] Abstract: Many nontornadic supercell storms have times when they appear to be moving toward tornadogenesis, including the development of a strong low-level vortex, but never end up producing a tornado. These tornadogenesis failure (TGF) episodes can be a substantial challenge to operational meteorologists. In this study, a sample of 32 pre-tornadic and 36 pre-TGF supercells is examined in the 30 min pre-tornadogenesis or pre-TGF period to explore the feasibility of using polarimetric radar metrics to highlight storms with larger tornadogenesis potential in the near-term. Overall the results indicate few strong distinguishers of pre-tornadic storms. Differential reflectivity (ZDR) arc size and intensity were the most promising metrics examined, with ZDR arc size potentially exhibiting large enough differences between the two storm subsets to be operationally useful. Change in the radar metrics leading up to tornadogenesis or TGF did not exhibit large differences, though most findings were consistent with hypotheses based on prior findings in the literature. Keywords: supercell; nowcasting; tornadogenesis failure; polarimetric radar Citation: Van Den Broeke, M. 1. Introduction Polarimetric Radar Characteristics of Supercell thunderstorms produce most strong tornadoes in North America, moti- Tornadogenesis Failure in Supercell vating study of their radar signatures for the benefit of the operational and research Thunderstorms. Atmosphere 2021, 12, communities. Since the polarimetric upgrade to the national radar network of the United 581. https://doi.org/ States (2011–2013), polarimetric radar signatures of these storms have become well-known, 10.3390/atmos12050581 e.g., [1–5], and many others. -
Soaring Weather
Chapter 16 SOARING WEATHER While horse racing may be the "Sport of Kings," of the craft depends on the weather and the skill soaring may be considered the "King of Sports." of the pilot. Forward thrust comes from gliding Soaring bears the relationship to flying that sailing downward relative to the air the same as thrust bears to power boating. Soaring has made notable is developed in a power-off glide by a conven contributions to meteorology. For example, soar tional aircraft. Therefore, to gain or maintain ing pilots have probed thunderstorms and moun altitude, the soaring pilot must rely on upward tain waves with findings that have made flying motion of the air. safer for all pilots. However, soaring is primarily To a sailplane pilot, "lift" means the rate of recreational. climb he can achieve in an up-current, while "sink" A sailplane must have auxiliary power to be denotes his rate of descent in a downdraft or in come airborne such as a winch, a ground tow, or neutral air. "Zero sink" means that upward cur a tow by a powered aircraft. Once the sailcraft is rents are just strong enough to enable him to hold airborne and the tow cable released, performance altitude but not to climb. Sailplanes are highly 171 r efficient machines; a sink rate of a mere 2 feet per second. There is no point in trying to soar until second provides an airspeed of about 40 knots, and weather conditions favor vertical speeds greater a sink rate of 6 feet per second gives an airspeed than the minimum sink rate of the aircraft. -
Tornado Safety Q & A
TORNADO SAFETY Q & A The Prosper Fire Department Office of Emergency Management’s highest priority is ensuring the safety of all Prosper residents during a state of emergency. A tornado is one of the most violent storms that can rip through an area, striking quickly with little to no warning at all. Because the aftermath of a tornado can be devastating, preparing ahead of time is the best way to ensure you and your family’s safety. Please read the following questions about tornado safety, answered by Prosper Emergency Management Coordinator Kent Bauer. Q: During s evere weather, what does the Prosper Fire Department do? A: We monitor the weather alerts sent out by the National Weather Service. Because we are not meteorologists, we do not interpret any sort of storms or any sort of warnings. Instead, we pass along the information we receive from the National Weather Service to our residents through social media, storm sirens and Smart911 Rave weather warnings. Q: What does a Tornado Watch mean? A: Tornadoes are possible. Remain alert for approaching storms. Watch the sky and stay tuned to NOAA Weather Radio, commercial radio or television for information. Q: What does a Tornado Warning mean? A: A tornado has been sighted or indicated by weather radar and you need to take shelter immediately. Q: What is the reason for setting off the Outdoor Storm Sirens? A: To alert those who are outdoors that there is a tornado or another major storm event headed Prosper’s way, so seek shelter immediately. I f you are outside and you hear the sirens go off, do not call 9-1-1 to ask questions about the warning. -
Tornadoes & Funnel Clouds Fake Tornado
NOAA’s National Weather Service Basic Concepts of Severe Storm Spotting 2009 – Rusty Kapela Milwaukee/Sullivan weather.gov/milwaukee Housekeeping Duties • How many new spotters? - if this is your first spotter class & you intend to be a spotter – please raise your hands. • A basic spotter class slide set & an advanced spotter slide set can be found on the Storm Spotter Page on the Milwaukee/Sullivan web site (handout). • Utilize search engines and You Tube to find storm videos and other material. Class Agenda • 1) Why we are here • 2) National Weather Service Structure & Role • 3) Role of Spotters • 4) Types of reports needed from spotters • 5) Thunderstorm structure • 6) Shelf clouds & rotating wall clouds • 7) You earn your “Learner’s Permit” Thunderstorm Structure Those two cloud features you were wondering about… Storm Movement Shelf Cloud Rotating Wall Cloud Rain, Hail, Downburst winds Tornadoes & Funnel Clouds Fake Tornado It’s not rotating & no damage! Let’s Get Started! Video Why are we here? Parsons Manufacturing 120-140 employees inside July 13, 2004 Roanoke, IL Storm shelters F4 Tornado – no injuries or deaths. They have trained spotters with 2-way radios Why Are We Here? National Weather Service’s role – Issue warnings & provide training Spotter’s role – Provide ground-truth reports and observations We need (more) spotters!! National Weather Service Structure & Role • Federal Government • Department of Commerce • National Oceanic & Atmospheric Administration • National Weather Service 122 Field Offices, 6 Regional, 13 River Forecast Centers, Headquarters, other specialty centers Mission – issue forecasts and warnings to minimize the loss of life & property National Weather Service Forecast Office - Milwaukee/Sullivan Watch/Warning responsibility for 20 counties in southeast and south- central Wisconsin. -
An Observational Analysis Quantifying the Distance of Supercell-Boundary Interactions in the Great Plains
Magee, K. M., and C. E. Davenport, 2020: An observational analysis quantifying the distance of supercell-boundary interactions in the Great Plains. J. Operational Meteor., 8 (2), 15-38, doi: https://doi.org/10.15191/nwajom.2020.0802 An Observational Analysis Quantifying the Distance of Supercell-Boundary Interactions in the Great Plains KATHLEEN M. MAGEE National Weather Service Huntsville, Huntsville, AL CASEY E. DAVENPORT University of North Carolina at Charlotte, Charlotte, NC (Manuscript received 11 June 2019; review completed 7 October 2019) ABSTRACT Several case studies and numerical simulations have hypothesized that baroclinic boundaries provide enhanced horizontal and vertical vorticity, wind shear, helicity, and moisture that induce stronger updrafts, higher reflectivity, and stronger low-level rotation in supercells. However, the distance at which a surface boundary will provide such enhancement is less well-defined. Previous studies have identified enhancement at distances ranging from 10 km to 200 km, and only focused on tornado production and intensity, rather than all forms of severe weather. To better aid short-term forecasts, the observed distances at which supercells produce severe weather in proximity to a boundary needs to be assessed. In this study, the distance between a large number of observed supercells and nearby surface boundaries (including warm fronts, stationary fronts, and outflow boundaries) is measured throughout the lifetime of each storm; the distance at which associated reports of large hail and tornadoes occur is also collected. Statistical analyses assess the sensitivity of report distributions to report type, boundary type, boundary strength, angle of interaction, and direction of storm motion relative to the boundary. -
More Observations of Small Funnel Clouds and Other Tubular Clouds
3714 MONTHLY WEATHER REVIEW VOLUME 133 PICTURE OF THE MONTH More Observations of Small Funnel Clouds and Other Tubular Clouds HOWARD B. BLUESTEIN School of Meteorology, University of Oklahoma, Norman, Oklahoma (Manuscript received 14 March 2005, in final form 20 May 2005) ABSTRACT In this brief contribution, photographic documentation is provided of a variety of small, tubular-shaped clouds and of a small funnel cloud pendant from a convective cloud that appears to have been modified by flow over high-altitude mountains in northeast Colorado. These funnel clouds are contrasted with others that have been documented, including those pendant from high-based cumulus clouds in the plains of the United States. It is suggested that the mountain funnel cloud is unique in that flow over high terrain is probably responsible for its existence; other types of small funnel clouds are seen both over elevated, mountainous terrain and over flat terrain at lower elevations. 1. Introduction which the benign funnel clouds occur so that if they are observed, severe weather warnings are not issued. Fur- Bluestein (1994) and others (e.g., Doswell 1985, p. thermore, the small funnel clouds are of interest in their 107; McCaul and Blanchard 1990) have documented, in own right because their dynamics are not well under- the plains of the United States, small funnel clouds pen- stood, and they have not been discussed in the litera- dant from convective clouds whose updrafts appear to ture to the much greater extent that the dynamics of be rooted above the boundary layer. Above many of tornadoes have (e.g., Davies-Jones 1986). -
Electrical Role for Severe Storm Tornadogenesis (And Modification) R.W
y & W log ea to th a e m r li F C o r Armstrong and Glenn, J Climatol Weather Forecasting 2015, 3:3 f e o c l a a s n t r i http://dx.doi.org/10.4172/2332-2594.1000139 n u g o J Climatology & Weather Forecasting ISSN: 2332-2594 ReviewResearch Article Article OpenOpen Access Access Electrical Role for Severe Storm Tornadogenesis (and Modification) R.W. Armstrong1* and J.G. Glenn2 1Department of Mechanical Engineering, University of Maryland, College Park, MD, USA 2Munitions Directorate, Eglin Air Force Base, FL, USA Abstract Damage from severe storms, particularly those involving significant lightning is increasing in the US. and abroad; and, increasingly, focus is on an electrical role for lightning in intra-cloud (IC) tornadogenesis. In the present report, emphasis is given to severe storm observations and especially to model descriptions relating to the subject. Keywords: Tornadogenesis; Severe storms; Electrification; in weather science was submitted in response to solicitation from the Lightning; Cloud seeding National Science Board [16], and a note was published on the need for cooperation between weather modification practitioners and academic Introduction researchers dedicated to ameliorating the consequences of severe weather storms [17]. Need was expressed for interdisciplinary research Benjamin Franklin would be understandably disappointed. Here on the topic relating to that recently touted for research in the broader we are, more than 260 years after first demonstration in Marly-la-Ville, field of meteorological sciences [18]. -
The Lagrange Torando During Vortex2. Part Ii: Photogrammetry Analysis of the Tornado Combined with Dual-Doppler Radar Data
6.3 THE LAGRANGE TORANDO DURING VORTEX2. PART II: PHOTOGRAMMETRY ANALYSIS OF THE TORNADO COMBINED WITH DUAL-DOPPLER RADAR DATA Nolan T. Atkins*, Roger M. Wakimoto#, Anthony McGee*, Rachel Ducharme*, and Joshua Wurman+ *Lyndon State College #National Center for Atmospheric Research +Center for Severe Weather Research Lyndonville, VT 05851 Boulder, CO 80305 Boulder, CO 80305 1. INTRODUCTION studies, however, that have related the velocity and reflectivity features observed in the radar data to Over the years, mobile ground-based and air- the visual characteristics of the condensation fun- borne Doppler radars have collected high-resolu- nel, debris cloud, and attendant surface damage tion data within the hook region of supercell (e.g., Bluestein et al. 1993, 1197, 204, 2007a&b; thunderstorms (e.g., Bluestein et al. 1993, 1997, Wakimoto et al. 2003; Rasmussen and Straka 2004, 2007a&b; Wurman and Gill 2000; Alexander 2007). and Wurman 2005; Wurman et al. 2007b&c). This paper is the second in a series that pre- These studies have revealed details of the low- sents analyses of a tornado that formed near level winds in and around tornadoes along with LaGrange, WY on 5 June 2009 during the Verifica- radar reflectivity features such as weak echo holes tion on the Origins of Rotation in Tornadoes Exper- and multiple high-reflectivity rings. There are few iment (VORTEX 2). VORTEX 2 (Wurman et al. 5 June, 2009 KCYS 88D 2002 UTC 2102 UTC 2202 UTC dBZ - 0.5° 100 Chugwater 100 50 75 Chugwater 75 330° 25 Goshen Co. 25 km 300° 50 Goshen Co. 25 60° KCYS 30° 30° 50 80 270° 10 25 40 55 dBZ 70 -45 -30 -15 0 15 30 45 ms-1 Fig.