Meteorology – Lecture 19
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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 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. -
Extratropical Cyclones and Anticyclones
© Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION Courtesy of Jeff Schmaltz, the MODIS Rapid Response Team at NASA GSFC/NASA Extratropical Cyclones 10 and Anticyclones CHAPTER OUTLINE INTRODUCTION A TIME AND PLACE OF TRAGEDY A LiFE CYCLE OF GROWTH AND DEATH DAY 1: BIRTH OF AN EXTRATROPICAL CYCLONE ■■ Typical Extratropical Cyclone Paths DaY 2: WiTH THE FI TZ ■■ Portrait of the Cyclone as a Young Adult ■■ Cyclones and Fronts: On the Ground ■■ Cyclones and Fronts: In the Sky ■■ Back with the Fitz: A Fateful Course Correction ■■ Cyclones and Jet Streams 298 9781284027372_CH10_0298.indd 298 8/10/13 5:00 PM © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION Introduction 299 DaY 3: THE MaTURE CYCLONE ■■ Bittersweet Badge of Adulthood: The Occlusion Process ■■ Hurricane West Wind ■■ One of the Worst . ■■ “Nosedive” DaY 4 (AND BEYOND): DEATH ■■ The Cyclone ■■ The Fitzgerald ■■ The Sailors THE EXTRATROPICAL ANTICYCLONE HIGH PRESSURE, HiGH HEAT: THE DEADLY EUROPEAN HEAT WaVE OF 2003 PUTTING IT ALL TOGETHER ■■ Summary ■■ Key Terms ■■ Review Questions ■■ Observation Activities AFTER COMPLETING THIS CHAPTER, YOU SHOULD BE ABLE TO: • Describe the different life-cycle stages in the Norwegian model of the extratropical cyclone, identifying the stages when the cyclone possesses cold, warm, and occluded fronts and life-threatening conditions • Explain the relationship between a surface cyclone and winds at the jet-stream level and how the two interact to intensify the cyclone • Differentiate between extratropical cyclones and anticyclones in terms of their birthplaces, life cycles, relationships to air masses and jet-stream winds, threats to life and property, and their appearance on satellite images INTRODUCTION What do you see in the diagram to the right: a vase or two faces? This classic psychology experiment exploits our amazing ability to recognize visual patterns. -
Chapter 5 Frictional Boundary Layers
Chapter 5 Frictional boundary layers 5.1 The Ekman layer problem over a solid surface In this chapter we will take up the important question of the role of friction, especially in the case when the friction is relatively small (and we will have to find an objective measure of what we mean by small). As we noted in the last chapter, the no-slip boundary condition has to be satisfied no matter how small friction is but ignoring friction lowers the spatial order of the Navier Stokes equations and makes the satisfaction of the boundary condition impossible. What is the resolution of this fundamental perplexity? At the same time, the examination of this basic fluid mechanical question allows us to investigate a physical phenomenon of great importance to both meteorology and oceanography, the frictional boundary layer in a rotating fluid, called the Ekman Layer. The historical background of this development is very interesting, partly because of the fascinating people involved. Ekman (1874-1954) was a student of the great Norwegian meteorologist, Vilhelm Bjerknes, (himself the father of Jacques Bjerknes who did so much to understand the nature of the Southern Oscillation). Vilhelm Bjerknes, who was the first to seriously attempt to formulate meteorology as a problem in fluid mechanics, was a student of his own father Christian Bjerknes, the physicist who in turn worked with Hertz who was the first to demonstrate the correctness of Maxwell’s formulation of electrodynamics. So, we are part of a joined sequence of scientists going back to the great days of classical physics. -
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. -
Central Region Technical Attachment 95-08 Examination of an Apparent
CRH SSD APRIL 1995 CENTRAL REGION TECHNICAL ATTACHMENT 95-08 EXAMINATION OF AN APPARENT LANDSPOUT IN THE EASTERN BLACK HILLS OF WESTERN SOUTH DAKOTA David L. Hintz1 and Matthew J. Bunkers National Weather Service Office Rapid City, South Dakota 1. Abstract On June 29, 1994, an apparent landspout occurred in the Black Hills of South Dakota. This landspout exhibited most of the features characteristic of traditional landspouts documented in eastern Colorado. The landspout lasted 3 to 8 minutes, had a width of less than 20 m and a path of 1 to 3 km, produced estimated wind speeds of Fl intensity (33 to 50 m s1), and emanated from a towering cumulus (TCU) cloud located along a quasi-stationary convergencq/cyclonic shear zone. No radar echo was observed with this event; however, a supercell thunderstorm was located 80-100 km to the east. National Weather Service meteorologists surveyed the “very localized” damage area and ruled out the possibility of the landspout being related to microburst, gustnado, or dust devil activity, as winds away from the landspout were less than 3 m s1. The landspout apparently “detached” from the parent TCU and damaged a farm which resulted in $1,000 dollars in expenses. 2. Introduction During the late 1980’s and early 1990’s researchers documented a phe nomenon with subtle differences from traditional tornadoes and waterspouts, herein referred to as the landspout (Seargent 1994; Brady and Szoke 1988, 1989; Bluestein 1985). The term “landspout” was actually coined by Bluestein (I985)(in the formal literature) when he observed this type of vortex along an Oklahoma squall line. -
HODOGRAPHS and SEVERE WEATHE B E. W. Mccaul. Jr.. Steve
HODOGRAPHS AND SEVERE WEATHE B E. W. McCaul. Jr.. Steve Lazarus. Fred Carr One ingredient which is believed to be important in governing the morphology of thunderstorms is the profile of vertical shear in the environment which supports the storms. Numerous observational and theoretical studies have shown that storms which form in weakly-sheared environments tend to have non-steady circulations (multicells), while those that form in strongly-sheared environments can develop steady, persistent circulations (supereells). Although intuition suggests that strong shear can only inhibit the formation of organized updrafts, this tendency is partly offset by the ability of shear flows to generate a variety of hydrodynamical instabilities which allow for the possibility of updraft growth. Forecasters who work in areas of the country prone to outbreaks of severe weather should be prepared to recognize not only the thermodynamic conditions but also the vertical shear conditions favorable for various types of severe storms. Inspection of temperature and moisture soundings can reveal the presence of the necessary thermodynamic instability, while inspection of wind profiles (hodographs) can help diagnose whether conditions are right for the development of tornadoes. Hodographs can be drawn either as plots of u (z) vs. v (z) in Cartesian coordinates or V (z) vs. 8 (z) in cylindrical coordinates. In either case, the actual shape of the hodograph will be the same for any given wind profile. On the OU Meteorology weather computer, hodographs from any raob station may be plotted using "mchodo" in GEMPAK. Each plotted hodograph represents nothing more than the curve which connects, in order of ascending altitude, the tips of all the observed wind vectors from a sounding, with the bases of the vectors attached to a common origin. -
Severe Weather Forecasting Tip Sheet: WFO Louisville
Severe Weather Forecasting Tip Sheet: WFO Louisville Vertical Wind Shear & SRH Tornadic Supercells 0-6 km bulk shear > 40 kts – supercells Unstable warm sector air mass, with well-defined warm and cold fronts (i.e., strong extratropical cyclone) 0-6 km bulk shear 20-35 kts – organized multicells Strong mid and upper-level jet observed to dive southward into upper-level shortwave trough, then 0-6 km bulk shear < 10-20 kts – disorganized multicells rapidly exit the trough and cross into the warm sector air mass. 0-8 km bulk shear > 52 kts – long-lived supercells Pronounced upper-level divergence occurs on the nose and exit region of the jet. 0-3 km bulk shear > 30-40 kts – bowing thunderstorms A low-level jet forms in response to upper-level jet, which increases northward flux of moisture. SRH Intense northwest-southwest upper-level flow/strong southerly low-level flow creates a wind profile which 0-3 km SRH > 150 m2 s-2 = updraft rotation becomes more likely 2 -2 is very conducive for supercell development. Storms often exhibit rapid development along cold front, 0-3 km SRH > 300-400 m s = rotating updrafts and supercell development likely dryline, or pre-frontal convergence axis, and then move east into warm sector. BOTH 2 -2 Most intense tornadic supercells often occur in close proximity to where upper-level jet intersects low- 0-6 km shear < 35 kts with 0-3 km SRH > 150 m s – brief rotation but not persistent level jet, although tornadic supercells can occur north and south of upper jet as well. -
Hurricane Force Extratropical Cyclones As Observed by the Quikscat Scatterometer
P2.11 HURRICANE FORCE EXTRATROPICAL CYCLONES AS OBSERVED BY THE QUIKSCAT SCATTEROMETER Joan Ulrich Von Ahn* STG, Inc./National Oceanic and Atmospheric Administration/National Weather Service/National Centers for Environmental Prediction, Camp Springs, Maryland Joseph M. Sienkiewicz National Oceanic and Atmospheric Administration/National Weather Service/ National Centers for Environmental Prediction, Camp Springs, Maryland Joi Copridge Clark Atlanta University, Atlanta, Georgia Jodi Min United States Coast Guard Academy, New London, Connecticut Tony Crutch National Oceanic and Atmospheric Administration/National Weather Service/ National Centers for Environmental Prediction, Camp Springs, Maryland 1. INTRODUCTION or significant water cloud, the algorithm is unable to The primary responsibility of The Ocean Prediction report a wind speed. The accuracy of ±2 m s-1 for the Center (OPC) of the National Centers for Environmental wind speed data can only be guaranteed in the 2-25 m Prediction (NCEP) is the issuance of marine wind s-1 range. Wind speeds above this value are not reliable warnings and forecasts for maritime users in order to (Atlas et al., 1996). Therefore, SSM/I cannot foster the protection of life and property, safety at sea, distinguish between gale and storm force winds (Atlas et and the enhancement of economic opportunity. The al, 2001). Since Storm warnings are issued for winds warnings discussed in this study refer to the short-term from 24.7 – 32.4 m s -1 and Hurricane Force warnings marine wind warnings that are placed as labels on the are issued for wind speed greater than 32.9 m s -1 the North Atlantic and North Pacific Surface Analyses SSM/I wind observations are of limited value to OPC produced by OPC four times per day. -
Quasi-Linear Convective System Mesovorticies and Tornadoes
Quasi-Linear Convective System Mesovorticies and Tornadoes RYAN ALLISS & MATT HOFFMAN Meteorology Program, Iowa State University, Ames ABSTRACT Quasi-linear convective system are a common occurance in the spring and summer months and with them come the risk of them producing mesovorticies. These mesovorticies are small and compact and can cause isolated and concentrated areas of damage from high winds and in some cases can produce weak tornadoes. This paper analyzes how and when QLCSs and mesovorticies develop, how to identify a mesovortex using various tools from radar, and finally a look at how common is it for a QLCS to put spawn a tornado across the United States. 1. Introduction Quasi-linear convective systems, or squall lines, are a line of thunderstorms that are Supercells have always been most feared oriented linearly. Sometimes, these lines of when it has come to tornadoes and as they intense thunderstorms can feature a bowed out should be. However, quasi-linear convective systems can also cause tornadoes. Squall lines and bow echoes are also known to cause tornadoes as well as other forms of severe weather such as high winds, hail, and microbursts. These are powerful systems that can travel for hours and hundreds of miles, but the worst part is tornadoes in QLCSs are hard to forecast and can be highly dangerous for the public. Often times the supercells within the QLCS cause tornadoes to become rain wrapped, which are tornadoes that are surrounded by rain making them hard to see with the naked eye. This is why understanding QLCSs and how they can produce mesovortices that are capable of producing tornadoes is essential to forecasting these tornadic events that can be highly dangerous. -
Short-Term Forecasts of Left-Moving Supercells from an Experimental Warn-On-Forecast System
Jones, T. A., and C. Nixon, 2017: Short-term forecasts of left-moving supercells from an experimental Warn-on-Forecast system. J. Operational Meteor., 5 (13), 161-170, doi: https://doi.org/10.15191/nwajom.2017.0513 Short-term Forecasts of Left-Moving Supercells from an Experimental Warn-on-Forecast System THOMAS A. JONES Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, Norman, Oklahoma CAMERON NIXON Texas Tech University, Lubbock, Texas (Manuscript received 10 March 2017; review completed 23 June 2017) ABSTRACT Most research in storm-scale numerical weather prediction has been focused on right-moving supercells as they typically lend themselves to all forms of high-impact weather, including tornadoes. As the dynamics behind splitting updrafts and storm motion have become better understood, differentiating between atmospheric conditions that encourage right- and left-moving supercells has become the subject of increasing study because of its implication for these weather forecasts. Despite still often producing large hail and damaging winds, left- moving (anticyclonically rotating in the Northern Hemisphere) supercells have received much less attention. During the 2016, NOAA Hazardous Weather Testbed, the NSSL Experimental Warn-on-Forecast System for ensembles (NEWS-e) was run in real-time. One event in particular occurred on 8 May 2016 during which multiple left- and right- moving supercells developed in western Oklahoma and Kansas—producing many severe weather reports. The goal of this study was to analyze the near storm environment created by NEWS-e using wind shear and other severe weather parameters. Then, we sought to determine the ability of the NEWS-e system to forecast storm splits and the persistence of left- and right- moving supercells through qualitatively analyzing tracks of forecast updraft helicity. -
Mesoscale Organization of Convection
MesoscaleMesoscale OrganizationOrganization ofof ConvectionConvection SquallSquall LineLine • Is a set of individual intense thunderstorm cells arranged in a line. • Thy occur along a boundary of unstable air – e.g. a cold front. • Strong environmental wind shear causes the updraft to be tilted and separated from the downdraft. • The dense cold air of the downdraft forms a ‘gust front’. SquallSquall lineline fromfrom SpaceSpace Image courtesy of http://cnls.lanl.gov. This image has been removed due to copyright restrictions. Please see: http://www.floridalightning.com/Hurricane_Wilma.html This image has been removed due to copyright restrictions. Please see similar images on: http://www.bom.gov.au/wa/sevwx/ MesoscaleMesoscale ConvectiveConvective ComplexComplex • A Mesoscale Convective Complex is composed of multiple single-cell storms in different stages of development. • The individual thunderstorms must support the formation of other convective cells • In order to last a long time, a good supply of moisture is required at low levels in te atmosphere. InfraredInfrared imageimage ofof aa mesoscalemesoscale convectiveconvective complexcomplex overover Kansas,Kansas, JulyJuly 88 1997.1997. This image has been removed due to copyright restrictions. Please see similar images on: http://cimss.ssec.wisc.edu/goes/misc/970708.html TYPESTYPES OFOF THUNDERSTORMTHUNDERSTORM • SINGLE-CELL THUNDERSTORM • MULTICELL THUNDERSTORM • MESOSCALE CONVECTIVE C0MPLEX • SUPERCELL THUNDERSTORM Non-equilibrium Convection SUPERCELLSUPERCELL THUNDERSTORMSTHUNDERSTORMS • SINGLE CELL THUNDERSTORM THAT PRODUCES DANGEROUS WEATHER • REQUIRES A VERY UNSTABLE ATMOSPHERE AND STRONG VERTICAL WIND SHEAR - BOTH SPEED AND DIRECTION • UNDER THE INFLUENCE OF THE STRONG WIND SHEAR MUCH OF THE THUNDERSTORM ROTATES • FAVORED IN THE SOUTHERN GREAT PLAINS IN THE SPRING WindWind ShearShear Shear Vector Hodograph This image has been removed due to copyright restrictions.