DOCSLIB.ORG

Radar Detection of Tornadogenesis Kristofer S

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Radar Detection of Tornadogenesis Kristofer S Meteorology Senior Theses Undergraduate Theses and Capstone Projects 12-2016 Radar Detection of Tornadogenesis Kristofer S. Tuftedal Iowa State University, [email protected] Follow this and additional works at: https://lib.dr.iastate.edu/mteor_stheses Part of the Meteorology Commons Recommended Citation Tuftedal, Kristofer S., "Radar Detection of Tornadogenesis" (2016). Meteorology Senior Theses. 2. https://lib.dr.iastate.edu/mteor_stheses/2 This Dissertation/Thesis is brought to you for free and open access by the Undergraduate Theses and Capstone Projects at Iowa State University Digital Repository. It has been accepted for inclusion in Meteorology Senior Theses by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Radar Detection of Tornadogenesis Kristofer S. Tuftedal Department of Geological and Atmospheric Sciences, Iowa State University, Ames, Iowa Dr. James V. Aanstoos Department of Geological and Atmospheric Sciences, Iowa State University, Ames, Iowa ABSTRACT This research compared the basic and polarimetric radar products of non-tornadic and pre-tornadic supercells with the intent of finding a signature which appears to be indicative of tornadogenesis or a lack thereof. Reflectivity (ZHH), spectrum width (σv), differential reflectivity (ZDR), correlation coefficient (ρhv), and specific differential phase (KDP) were all visually analyzed using GR2Analyst and compared to existing schematics in an attempt to find a signature. Once an apparent signature was found, pooled t-tests were performed on the data to see if the mean value of the pre-tornadic supercell, where the signature was found, had a statistically significant difference with the mean value of the non-tornadic supercell in the same area. Overall, it was found that the discovered signature was statistically significant on the 95% confidence level. However, due to the small number of cases tested, a relationship between the signature and tornadogenesis cannot be proven, but can be suggested. ______________________________________________________________________________ 1. Introduction and Background warning due to their mistrust from previous warnings that did not produce a tornado. Finding ways to more accurately forecast tornadogenesis has been a long-standing Certain radar signatures have been found issue for National Weather Service (NWS) to be suggestive or indicative of tornadic meteorologists. Issuing tornado warnings for activity, such as the tornado vortex signatures supercells that do not produce tornadoes (TVS) and the tornado debris signatures leads to the public believing that most (TDS) (Stelten and Wolf 2014). These tornado warnings are only false alarms, signatures are either limited to moments prior resulting in a sort of “crying wolf” effect. to tornadogenesis like a TVS, or while a These false alarms not only harm the public’s tornado is ongoing like a TDS. While these perception of the NWS, but could also signatures are highly useful in their own potentially lead to serious injury to or even respects, such as determining whether a death of an individual that ignores a tornado supercell has enough vertical vorticity to produce a tornado or showing that a tornado 1 is ongoing and is lofting debris without on, but offer interesting hints at the having to rely on trained spotters, the public, possibility of radar signatures that are or law enforcement to confirm this, these indicative of tornadogenesis. signatures do little to aid a meteorologist in Another paper, Cai (2005), compared the determining whether a supercell will become mesocyclones for both tornadic and non- tornadic in advance of tornadogenesis. tornadic supercells in attempt to show that it Dual-polarization (Polarimetric) radar is a was possible to determine the difference relatively new tool in the world of Doppler between the two types of supercells using radar. Even though the first research pseudovorticity calculations. Pseudovorticity polarimetric radar was installed in 1983 and is defined in the paper as being the difference the first collection of polarimetric variables between the maximum outbound velocity and became available in 1992; the upgrade of the maximum inbound velocity in the velocity Weather Surveillance Radar-1988 Doppler couplet divided by the distance between the (WSR-88D) radars ran by NWS was not two maximum values. completed until 2013. Hence, we are only 휁 = Δ푉⁄퐿 (1) beginning to understand the operational pv potential that polarimetric products have to The prefix “pseudo” is used because equation offer. (1) does not look at full vorticity and only Some early research into detecting measures vorticity along the radial of the tornadoes with polarimetric products was radar beam. The study suggests that there will done in Ryzhkov et al. (2005). That study be notable differences between the slopes of the pseudovorticity lines, with the tornadic looked at different radar products, both polarimetric and not. The study looked at cases having a steeper slope than the non- tornadic cases. Even if pseudovorticity reflectivity factor (ZHH), radial velocity, calculations are not used in the same way that differential reflectivity (ZDR), specific it was used here, it can still be a useful differential phase (KDP), and correlation diagnostic tool to determine the rotational coefficient (ρhv) in order to determine the strength of a velocity couplet. usefulness of these products in tornado detection. That research, while showing that As research into polarimetric variables polarimetric data was definitely capable of continued, Van Den Broeke et al. (2008) detecting ongoing tornadoes and would help looked at these radar products at different forecasters with issuing tornado warnings, times during a given tornado’s life cycle. also found polarimetric signatures aloft and That study defined certain high, medium, and near the supercells in the study. These low thresholds for reflectivity factor (ZHH), signatures were deemed as out of the ordinary differential reflectivity (ZDR), specific and that they could be related with the differential phase (KDP), and correlation tornadogenesis processes. The signatures coefficient (ρhv). With these defined referred as out of the ordinary in that study thresholds, several tornadic supercells were were not explicitly mentioned or elaborated analyzed visually during distinct times in the 2 tornado’s life cycle. One rather interesting While the radar measurements in the finding from that paper, with respect to previous two studies were taken from mobile tornadogenesis, is the presence of medium X-band radars, these findings could prove values of KDP on the back side of the very important in detecting tornadogenesis supercells that was only present in times prior from WSR-88Ds. Considering that WSR- to tornadogenesis. Considering that the study 88Ds have a coarser temporal resolution only looked at tornadic supercells, looking when compared to the RaXPol radars, some for this same signature in non-tornadic of these features may happen too quickly to supercells could tell if this signature is be resolved by the WSR-88D radars. indicative of tornadogenesis. However, other features should still be able to be resolved, especially with the Two case studies (Houser et al. (2015) and implementation of Automated Volume Scan Klees et al. (2016)) have also provided some Evaluation and Termination (AVSET), insight into the life cycle of a tornadic Supplemental Adaptive Intra-Volume Low- supercell as well the differences between Level Scans (SAILS), and Multiple Elevation tornadic and non-tornadic supercells. Houser Scan Option with SAILS (MESO-SAILS). et al. (2015) found, using a mobile, rapid- scanning X-band, polarimetric Doppler radar The intention of this research is to attempt (RaXPol), that storm scale processes, such as to find a signature which appears in advance intensification and dissipation of velocity of tornadogenesis and does not appear in the happened quite rapidly, in about 30s, but non-tornadic cases; or find a signature which storm-scale processes that lead to appears in the non-tornadic cases, but does tornadogenesis happened on the order of not appear in the pre-tornadic cases. This approximately 2 minutes. Another finding research, then intends to determine the from that paper which could be particularly significance of any present signatures that fit interesting is that tornadogenesis did not these criteria and speculate on potential occur until after the strengthening of rotation causes for these signatures. between 3 and 3.5 km above ground. While 2. Data and Methods that study did not look at non-tornadic supercells, this signature would be one that a. Data Selection could be looked for when doing the An initial set of days to search for comparison as it might potentially be a potential pre-tornadic and non-tornadic signature that is only visible in tornadic supercells were selected based on the Storm storms. In the second case study, Klees et al. Prediction Center (SPC) event archive. Days (2016), it was found that non-tornadic with reported tornadoes in the region of supercells had strong rotation in the mid- interest (Fig. 1) were selected from May 2013 levels, but weak low-level rotation, whereas to May 2016. Forty days were selected to the tornadic supercells had significant search for potential cases. Following the rotation both in the mid-levels and lower selection of these potential case days, Next levels. 3 FIG.
Load more

Recommended publications
  • From Improving Tornado Warnings: from Observation to Forecast
    Improving Tornado Warnings: from Observation to Forecast John T. Snow Regents’ Professor of Meteorology Dean Emeritus, College of Atmospheric and Geographic Sciences, The University of Oklahoma Major contributions from: Dr. Russel Schneider –NOAA Storm Prediction Center Dr. David Stensrud – NOAA National Severe Storms Laboratory Dr. Ming Xue –Center for Analysis and Prediction of Storms, University of Oklahoma Dr. Lou Wicker –NOAA National Severe Storms Laboratory Hazards Caucus Alliance Briefing Tornadoes: Understanding how they develop and providing early warning 10:30 am – 11:30 am, Wednesday, 21 July 2010 Senate Capitol Visitors Center 212 Each Year: ~1,500 tornadoes touch down in the United States, causing over 80 deaths, 100s of injuries, and an estimated $1.1 billion in damages Statistics from NOAA Storm Prediction Center Supercell –A long‐lived rotating thunderstorm the primary type of thunderstorm producing strong and violent tornadoes Present Warning System: Warn on Detection • A Warning is the culmination of information developed and distributed over the preceding days sequence of day‐by‐day forecasts identifies an area of high threat •On the day, storm spotters deployed; radars monitor formation, growth of thunderstorms • Appearance of distinct cloud or radar echo features tornado has formed or is about to do so Warning is generated, distributed Present Warning System: Warn on Detection Radar at 2100 CST Radar at 2130 CST with Warning Thunderstorms are monitored using radar A warning is issued based on the detected and
    [Show full text]
  • Evaluating Operational and Newly Developed Mesocyclone and Tornado Detection Algorithms for Quasi-Linear Convective Systems Thomas James Turnage
    Florida State University Libraries Electronic Theses, Treatises and Dissertations The Graduate School 2007 Evaluating Operational and Newly Developed Mesocyclone and Tornado Detection Algorithms for Quasi-Linear Convective Systems Thomas James Turnage Follow this and additional works at the FSU Digital Library. For more information, please contact [email protected] THE FLORIDA STATE UNIVERSITY COLLEGE OF ARTS AND SCIENCES EVALUATING OPERATIONAL AND NEWLY DEVELOPED MESOCYCLONE AND TORNADO DETECTION ALGORITHMS FOR QUASI-LINEAR CONVECTIVE SYSTEMS By THOMAS JAMES TURNAGE A thesis submitted to the Department of Meteorology in partial fulfillment of the requirements for the degree of Master of Science Degree Awarded: Summer Semester, 2007 The members of the Committee approve the thesis of Thomas J. Turnage defended on April 5th, 2007. ____________________________________ Henry E. Fuelberg Professor Directing Thesis ____________________________________ Jon E. Ahlquist Committee Member ____________________________________ Paul H. Ruscher Committee Member ____________________________________ Andrew I. Watson Committee Member The Office of Graduate Studies has verified and approved the above named committee members. ii ACKNOWLEDGEMENTS I first want to thank the Lord. Without His blessings, none of this would have been possible. Next, I want to express my deepest gratitude and appreciation to my major professor Dr. Henry Fuelberg for working with me to complete this thesis in spite of rotating shift work at the National Weather Service (NWS) in Tallahassee and a subsequent move to Michigan. His high standards of integrity and academic excellence have been an inspiration to me. I also wish to thank the members of my thesis committee, Mr. Irv Watson of the NWS in Tallahassee, and Drs. Jon Ahlquist and Paul Ruscher for their advice and support.
    [Show full text]
  • 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.
    [Show full text]
  • 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].
    [Show full text]
  • Delayed Tornadogenesis Within New York State Severe Storms Article
    Wunsch, M. S. and M. M. French, 2020: Delayed tornadogenesis within New York State severe storms. J. Operational Meteor., 8 (6), 79-92, doi: https://doi.org/10.15191/nwajom.2020.0806. Article Delayed Tornadogenesis Within New York State Severe Storms MATTHEW S. WUNSCH NOAA/National Weather Service, Upton, NY, and School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY MICHAEL M. FRENCH School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY (Manuscript received 11 June 2019; review completed 21 October 2019) ABSTRACT Past observational research into tornadoes in the northeast United States (NEUS) has focused on integrated case studies of storm evolution or common supportive environmental conditions. A repeated theme in the former studies is the influence that the Hudson and Mohawk Valleys in New York State (NYS) may have on conditions supportive of tornado formation. Recent work regarding the latter has provided evidence that environments in these locations may indeed be more supportive of tornadoes than elsewhere in the NEUS. In this study, Weather Surveillance Radar–1988 Doppler data from 2008 to 2017 are used to investigate severe storm life cycles in NYS. Observed tornadic and non-tornadic severe cases were analyzed and compared to determine spatial and temporal differences in convective initiation (CI) points and severe event occurrence objectively within the storm paths. We find additional observational evidence supporting the hypothesis the Mohawk and Hudson Valley regions in NYS favor the occurrence of tornadogenesis: the substantially longer time it takes for storms that initiate in western NYS and Pennsylvania to become tornadic compared to storms that initiate in either central or eastern NYS.
    [Show full text]
  • Downloaded 09/30/21 06:43 PM UTC JUNE 1996 MONTEVERDI and JOHNSON 247
    246 WEATHER AND FORECASTING VOLUME 11 A Supercell Thunderstorm with Hook Echo in the San Joaquin Valley, California JOHN P. MONTEVERDI Department of Geosciences, San Francisco State University, San Francisco, California STEVE JOHNSON Association of Central California Weather Observers, Fresno, California (Manuscript received 30 January 1995, in ®nal form 9 February 1996) ABSTRACT This study documents a damaging supercell thunderstorm that occurred in California's San Joaquin Valley on 5 March 1994. The storm formed in a ``cold sector'' environment similar to that documented for several other recent Sacramento Valley severe thunderstorm events. Analyses of hourly subsynoptic surface and radar data suggested that two thunderstorms with divergent paths developed from an initial echo that had formed just east of the San Francisco Bay region. The southern storm became severe as it ingested warmer, moister boundary layer air in the south-central San Joaquin Valley. A well-developed hook echo with a 63-dBZ core was observed by a privately owned 5-cm radar as the storm passed through the Fresno area. Buoyancy parameters and ho- dograph characteristics were obtained both for estimated conditions for Fresno [on the basis of a modi®ed morning Oakland (OAK) sounding] and for the actual storm environment (on the basis of a radiosonde launched from Lemoore Naval Air Station at about the time of the storm's passage through the Fresno area). Both the estimated and actual hodographs essentially were straight and suggested storm splitting. Although the actual CAPE was similar to that which was estimated, the observed magnitude of the low-level shear was considerably greater than the estimate.
    [Show full text]
  • ESSENTIALS of METEOROLOGY (7Th Ed.) GLOSSARY
    ESSENTIALS OF METEOROLOGY (7th ed.) GLOSSARY Chapter 1 Aerosols Tiny suspended solid particles (dust, smoke, etc.) or liquid droplets that enter the atmosphere from either natural or human (anthropogenic) sources, such as the burning of fossil fuels. Sulfur-containing fossil fuels, such as coal, produce sulfate aerosols. Air density The ratio of the mass of a substance to the volume occupied by it. Air density is usually expressed as g/cm3 or kg/m3. Also See Density. Air pressure The pressure exerted by the mass of air above a given point, usually expressed in millibars (mb), inches of (atmospheric mercury (Hg) or in hectopascals (hPa). pressure) Atmosphere The envelope of gases that surround a planet and are held to it by the planet's gravitational attraction. The earth's atmosphere is mainly nitrogen and oxygen. Carbon dioxide (CO2) A colorless, odorless gas whose concentration is about 0.039 percent (390 ppm) in a volume of air near sea level. It is a selective absorber of infrared radiation and, consequently, it is important in the earth's atmospheric greenhouse effect. Solid CO2 is called dry ice. Climate The accumulation of daily and seasonal weather events over a long period of time. Front The transition zone between two distinct air masses. Hurricane A tropical cyclone having winds in excess of 64 knots (74 mi/hr). Ionosphere An electrified region of the upper atmosphere where fairly large concentrations of ions and free electrons exist. Lapse rate The rate at which an atmospheric variable (usually temperature) decreases with height. (See Environmental lapse rate.) Mesosphere The atmospheric layer between the stratosphere and the thermosphere.
    [Show full text]
  • Analysis of Tornadogenesis Failure Using Rapid-Scan Data from the Atmospheric Imaging Radar
    Analysis of Tornadogenesis Failure Using Rapid-Scan Data from the Atmospheric Imaging Radar KYLE D. PITTMAN∗ Department of Geographic and Atmospheric Sciences, Northern Illinois University DeKalb, Illinois ANDREW MAHRE School of Meteorology, and Advanced Radar Research Center, University of Oklahoma Norman, Oklahoma DAVID J. BODINE,CASEY B. GRIFFIN, AND JIM KURDZO Advanced Radar Research Center, University of Oklahoma Norman, Oklahoma VICTOR GENSINI Department of Geographic and Atmospheric Sciences, Northern Illinois University DeKalb, Illinois ABSTRACT Tornadogenesis in supercell thunderstorms has been a heavily studied topic by the atmospheric science community for several decades. However, the reasons why some supercells produce tornadoes, while others in similar environments and with similar characteristics do not, remains poorly understood. For this study, tornadogenesis failure is defined as a supercell appearing capable of tornado production, both visually and by meeting a vertically contiguous differential velocity (DV) threshold, without producing a sustained tor- nado. Data from a supercell that appeared capable of tornadogenesis, but which failed to produce a sustained tornado, was collected by the Atmospheric Imaging Radar (the AIR, a high temporal resolution radar) near Denver, CO on 21 May 2014. These data were examined to explore the mechanisms of tornadogenesis fail- ure within supercell thunderstorms. Analysis was performed on the rear-flank downdraft (RFD) region and mesocyclone, as previous work highlights the importance of these supercell features in tornadogenesis. The results indicate a lack of vertical continuity in rotation between the lowest level of data analyzed (100 m AGL), and heights aloft (> 500 m AGL). A relative maximum in low-level DV occurred at approximately 100 m AGL (0.5◦ in elevation on the radar) around the time of suspected tornadogenesis failure.
    [Show full text]
  • Tornadogenesis in a Simulated Mesovortex Within a Mesoscale Convective System
    3372 JOURNAL OF THE ATMOSPHERIC SCIENCES VOLUME 69 Tornadogenesis in a Simulated Mesovortex within a Mesoscale Convective System ALEXANDER D. SCHENKMAN,MING XUE, AND ALAN SHAPIRO Center for Analysis and Prediction of Storms, and School of Meteorology, University of Oklahoma, Norman, Oklahoma (Manuscript received 3 February 2012, in final form 23 April 2012) ABSTRACT The Advanced Regional Prediction System (ARPS) is used to simulate a tornadic mesovortex with the aim of understanding the associated tornadogenesis processes. The mesovortex was one of two tornadic meso- vortices spawned by a mesoscale convective system (MCS) that traversed southwestern and central Okla- homa on 8–9 May 2007. The simulation used 100-m horizontal grid spacing, and is nested within two outer grids with 400-m and 2-km grid spacing, respectively. Both outer grids assimilate radar, upper-air, and surface observations via 5-min three-dimensional variational data assimilation (3DVAR) cycles. The 100-m grid is initialized from a 40-min forecast on the 400-m grid. Results from the 100-m simulation provide a detailed picture of the development of a mesovortex that produces a submesovortex-scale tornado-like vortex (TLV). Closer examination of the genesis of the TLV suggests that a strong low-level updraft is critical in converging and amplifying vertical vorticity associated with the mesovortex. Vertical cross sections and backward trajectory analyses from this low-level updraft reveal that the updraft is the upward branch of a strong rotor that forms just northwest of the simulated TLV. The horizontal vorticity in this rotor originates in the near-surface inflow and is caused by surface friction.
    [Show full text]
  • Multiscale Overview of a Violent Tornado Outbreak with Attendant Flash Flooding
    416 WEATHER AND FORECASTING VOLUME 15 Multiscale Overview of a Violent Tornado Outbreak with Attendant Flash Flooding JOSEPH A. ROGASH NOAA/NWS/Storm Prediction Center, Norman, Oklahoma RICHARD D. SMITH National Weather Service, Tulsa, Oklahoma (Manuscript received 8 January 1999, in ®nal form 7 January 2000) ABSTRACT On 1 March 1997 violent tornadoes caused numerous fatalities and widespread damage across portions of central and eastern Arkansas and western Tennessee. In addition, the associated thunderstorms produced very heavy rainfall and ¯ash ¯ooding, with a few locations receiving up to 150 mm (6 in.) of rainfall in 3 h. The initial environment appeared favorable for strong tornadoes with unseasonably warm moist air at lower levels resulting in signi®cant instability (convective available potential energy values between 1400 and 1800 J kg21) where 0±2-km storm-relative helicities exceeded 300 m2 s22 and the middle-tropospheric storm-relative ¯ow was conducive for tornadic supercells. The most destructive tornadoes developed along a preexisting surface boundary where lower-tropospheric moisture convergence and frontogenesis were enhanced. Tornadoes and heaviest rainfall only ensue after upward motion associated with the direct circulation of an upper-tropospheric jet streak became collocated with lower-tropospheric upward forcing along the surface boundaries. From a ¯ash ¯ood perspective the event occurred in a hybrid mesohigh-synoptic heavy rain pattern as thunderstorms developed and moved along surface boundaries aligned nearly parallel to the mean wind. In addition, strong ¯ow and associated moisture ¯ux convergence in the lower troposphere favored the formation of cells to the southwest or upstream of the initial convection with thunderstorms, including a a tornadic supercell, traversing over the same area.
    [Show full text]
  • Near-Surface Vortex Structure in a Tornado and in a Sub-Tornado-Strength Convective-Storm Vortex Observed by a Mobile, W-Band Radar During VORTEX2
    VOLUME 141 MONTHLY WEATHER REVIEW NOVEMBER 2013 Near-Surface Vortex Structure in a Tornado and in a Sub-Tornado-Strength Convective-Storm Vortex Observed by a Mobile, W-Band Radar during VORTEX2 ,1 # @ ROBIN L. TANAMACHI,* HOWARD B. BLUESTEIN, MING XUE,* WEN-CHAU LEE, & & @ KRZYSZTOF A. ORZEL, STEPHEN J. FRASIER, AND ROGER M. WAKIMOTO * Center for Analysis and Prediction of Storms, and School of Meteorology, University of Oklahoma, Norman, Oklahoma # School of Meteorology, University of Oklahoma, Norman, Oklahoma @ National Center for Atmospheric Research, Boulder, Colorado & Microwave Remote Sensing Laboratory, University of Massachusetts, Amherst, Amherst, Massachusetts (Manuscript received 14 November 2012, in final form 22 May 2013) ABSTRACT As part of the Second Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2) field campaign, a very high-resolution, mobile, W-band Doppler radar collected near-surface (#200 m AGL) observations in an EF-0 tornado near Tribune, Kansas, on 25 May 2010 and in sub-tornado-strength vortices near Prospect Valley, Colorado, on 26 May 2010. In the Tribune case, the tornado’s condensation funnel dissipated and then reformed after a 3-min gap. In the Prospect Valley case, no condensation funnel was observed, but evidence from the highest-resolution radars in the VORTEX2 fleet indicates multiple, sub-tornado-strength vortices near the surface, some with weak-echo holes accompanying Doppler velocity couplets. Using high-resolution Doppler radar data, the authors document the full life cycle of sub- tornado-strength vortex beneath a convective storm that previously produced tornadoes. The kinematic evolution of these vortices, from genesis to decay, is investigated via ground-based velocity track display (GBVTD) analysis of the W-band velocity data.
    [Show full text]
  • Radar Artifacts and Associated Signatures, Along with Impacts of Terrain on Data Quality
    Radar Artifacts and Associated Signatures, Along with Impacts of Terrain on Data Quality 1.) Introduction: The WSR-88D (Weather Surveillance Radar designed and built in the 80s) is the most useful tool used by National Weather Service (NWS) Meteorologists to detect precipitation, calculate its motion, estimate its type (rain, snow, hail, etc) and forecast its position. Radar stands for “Radio, Detection, and Ranging”, was developed in the 1940’s and used during World War II, has gone through numerous enhancements and technological upgrades to help forecasters investigate storms with greater detail and precision. However, as our ability to detect areas of precipitation, including rotation within thunderstorms has vastly improved over the years, so has the radar’s ability to detect other significant meteorological and non meteorological artifacts. In this article we will identify these signatures, explain why and how they occur and provide examples from KTYX and KCXX of both meteorological and non meteorological data which WSR-88D detects. KTYX radar is located on the Tug Hill Plateau near Watertown, NY while, KCXX is located in Colchester, VT with both operated by the NWS in Burlington. Radar signatures to be shown include: bright banding, tornadic hook echo, low level lake boundary, hail spikes, sunset spikes, migrating birds, Route 7 traffic, wind farms, and beam blockage caused by terrain and the associated poor data sampling that occurs. 2.) How Radar Works: The WSR-88D operates by sending out directional pulses at several different elevation angles, which are microseconds long, and when the pulse intersects water droplets or other artifacts, a return signal is sent back to the radar.
    [Show full text]