Convective Dynamics
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Squall Lines: Meteorology, Skywarn Spotting, & a Brief Look at the 18
Squall Lines: Meteorology, Skywarn Spotting, & A Brief Look At The 18 June 2010 Derecho Gino Izzi National Weather Service, Chicago IL Outline • Meteorology 301: Squall lines – Brief review of thunderstorm basics – Squall lines – Squall line tornadoes – Mesovorticies • Storm spotting for squall lines • Brief Case Study of 18 June 2010 Event Thunderstorm Ingredients • Moisture – Gulf of Mexico most common source locally Thunderstorm Ingredients • Lifting Mechanism(s) – Fronts – Jet Streams – “other” boundaries – topography Thunderstorm Ingredients • Instability – Measure of potential for air to accelerate upward – CAPE: common variable used to quantify magnitude of instability < 1000: weak 1000-2000: moderate 2000-4000: strong 4000+: extreme Thunderstorms Thunderstorms • Moisture + Instability + Lift = Thunderstorms • What kind of thunderstorms? – Single Cell – Multicell/Squall Line – Supercells Thunderstorm Types • What determines T-storm Type? – Short/simplistic answer: CAPE vs Shear Thunderstorm Types • What determines T-storm Type? (Longer/more complex answer) – Lot we don’t know, other factors (besides CAPE/shear) include • Strength of forcing • Strength of CAP • Shear WRT to boundary • Other stuff Thunderstorm Types • Multi-cell squall lines most common type of severe thunderstorm type locally • Most common type of severe weather is damaging winds • Hail and brief tornadoes can occur with most the intense squall lines Squall Lines & Spotting Squall Line Terminology • Squall Line : a relatively narrow line of thunderstorms, often -
NWS Unified Surface Analysis Manual
Unified Surface Analysis Manual Weather Prediction Center Ocean Prediction Center National Hurricane Center Honolulu Forecast Office November 21, 2013 Table of Contents Chapter 1: Surface Analysis – Its History at the Analysis Centers…………….3 Chapter 2: Datasets available for creation of the Unified Analysis………...…..5 Chapter 3: The Unified Surface Analysis and related features.……….……….19 Chapter 4: Creation/Merging of the Unified Surface Analysis………….……..24 Chapter 5: Bibliography………………………………………………….…….30 Appendix A: Unified Graphics Legend showing Ocean Center symbols.….…33 2 Chapter 1: Surface Analysis – Its History at the Analysis Centers 1. INTRODUCTION Since 1942, surface analyses produced by several different offices within the U.S. Weather Bureau (USWB) and the National Oceanic and Atmospheric Administration’s (NOAA’s) National Weather Service (NWS) were generally based on the Norwegian Cyclone Model (Bjerknes 1919) over land, and in recent decades, the Shapiro-Keyser Model over the mid-latitudes of the ocean. The graphic below shows a typical evolution according to both models of cyclone development. Conceptual models of cyclone evolution showing lower-tropospheric (e.g., 850-hPa) geopotential height and fronts (top), and lower-tropospheric potential temperature (bottom). (a) Norwegian cyclone model: (I) incipient frontal cyclone, (II) and (III) narrowing warm sector, (IV) occlusion; (b) Shapiro–Keyser cyclone model: (I) incipient frontal cyclone, (II) frontal fracture, (III) frontal T-bone and bent-back front, (IV) frontal T-bone and warm seclusion. Panel (b) is adapted from Shapiro and Keyser (1990) , their FIG. 10.27 ) to enhance the zonal elongation of the cyclone and fronts and to reflect the continued existence of the frontal T-bone in stage IV. -
P4.6 Observations from the 13 April 2004 Wake Low Damaging Wind Event in South Florida
P4.6 OBSERVATIONS FROM THE 13 APRIL 2004 WAKE LOW DAMAGING WIND EVENT IN SOUTH FLORIDA Robert R. Handel and Pablo Santos NOAA/NWS, Miami, Florida 1. INTRODUCTION of April 12th persisted across the Florida Straits. This boundary exhibited pseudo-warm frontal characteristics, Damaging winds affected portions of South Florida and was lifting northward over South Florida (white during the early morning of April 13, 2004. These winds dashed line in Fig. 1). To the north of the boundary, a occurred behind a large area of stratiform precipitation cool and stable surface layer was present over land. associated with a mesoscale convective system (MCS) A high amplitude longwave mid/upper tropospheric that moved across the southeastern Gulf of Mexico trough was located over the eastern United States. The during the evening of April 12, 2004 (Fig. 1). Wind axis of this trough extended from the Great Lakes speeds sustained between 30 and 50 mph with gusts southward to the central Gulf of Mexico while South reaching 76 mph were recorded on Lake Okeechobee. Florida was upstream of the ridge axis located near These winds produced a seiche effect on Lake 65°W longitude. In addition, a 130-knot (67 m s-1) polar Okeechobee, resulting in a 5.5 ft maximum water level jet and 60-knot (31 m s-1) subtropical jet were splitting differential between the north and south sides of this over the Gulf of Mexico and South Florida producing shallow lake (Fig. 8). In addition, damage from the high significant upper level diffluence over South Florida. -
The Evolution of the 10–11 June 1985 PRE-STORM Squall Line: Initiation
478 MONTHLY WEATHER REVIEW VOLUME 125 The Evolution of the 10±11 June 1985 PRE-STORM Squall Line: Initiation, Development of Rear In¯ow, and Dissipation SCOTT A. BRAUN AND ROBERT A. HOUZE JR. Department of Atmospheric Sciences, University of Washington, Seattle, Washington (Manuscript received 12 December 1995, in ®nal form 12 August 1996) ABSTRACT Mesoscale analysis of surface observations and mesoscale modeling results show that the 10±11 June squall line, contrary to prior studies, did not form entirely ahead of a cold front. The primary environmental features leading to the initiation and organization of the squall line were a low-level trough in the lee of the Rocky Mountains and a midlevel short-wave trough. Three additional mechanisms were active: a southeastward-moving cold front formed the northern part of the line, convection along the edge of cold air from prior convection over Oklahoma and Kansas formed the central part of the line, and convection forced by convective out¯ow near the lee trough axis formed the southern portion of the line. Mesoscale model results show that the large-scale environment signi®cantly in¯uenced the mesoscale cir- culations associated with the squall line. The qualitative distribution of along-line velocities within the squall line is attributed to the larger-scale circulations associated with the lee trough and midlevel baroclinic wave. Ambient rear-to-front (RTF) ¯ow to the rear of the squall line, produced by the squall line's nearly perpendicular orientation to strong westerly ¯ow at upper levels, contributed to the exceptional strength of the rear in¯ow in this storm. -
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. -
Observations of Turbulent Kinematics and Lightning-Inferred Electric Potential Structure in a Severe Squall Line Eric C
XV International Conference on Atmospheric Electricity, 15-20 June 2014, Norman, Oklahoma, U.S.A. Observations of turbulent kinematics and lightning-inferred electric potential structure in a severe squall line Eric C. Bruning1∗ Vicente Salinas1, Vanna Sullivan1, Scott Gunter1, and John Schroeder1 1Texas Tech University, Lubbock, TX, U.S.A. ABSTRACT: Recent work by Bruning and MacGorman [2013] proposed an energetic measure of lightning flashes based on flash size (area) and rate. The resulting energy spectrum as a function of flash size had a consistent shape, and had an apparently linear scaling regime at the same length scales where a turbulent thunderstorm’s inertial subrange would be expected. They hypothesized that electrical potential was organized by the (possibly turbulent) character of the convective flow. Since then, flash extent has also been applied to the energy available for NOx production by lightning, and the geometric, space-filling character of the lightning channel itself. A severe squall line that moved across West Texas on the night of 5 June 2013 caused extensive dam- age, including much that was consistent with 80-90 mph winds in the vicinity of Lubbock. The storm was samplednear Pep, TX during the onset of severe winds by two Ka-band mobile radars operated by Texas Tech University (TTU), as well as the West Texas Lightning Mapping Array (WTLMA). In-situ observa- tions by TTU StickNet probes verified the severe winds. Vertical scans with the radars were taken ahead of the storm and continuously for one hour behind the line in conditions consistent with the conceptual model for the transition zone of a mesoscale convective system. -
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. -
Synoptic Meteorology
Lecture Notes on Synoptic Meteorology For Integrated Meteorological Training Course By Dr. Prakash Khare Scientist E India Meteorological Department Meteorological Training Institute Pashan,Pune-8 186 IMTC SYLLABUS OF SYNOPTIC METEOROLOGY (FOR DIRECT RECRUITED S.A’S OF IMD) Theory (25 Periods) ❖ Scales of weather systems; Network of Observatories; Surface, upper air; special observations (satellite, radar, aircraft etc.); analysis of fields of meteorological elements on synoptic charts; Vertical time / cross sections and their analysis. ❖ Wind and pressure analysis: Isobars on level surface and contours on constant pressure surface. Isotherms, thickness field; examples of geostrophic, gradient and thermal winds: slope of pressure system, streamline and Isotachs analysis. ❖ Western disturbance and its structure and associated weather, Waves in mid-latitude westerlies. ❖ Thunderstorm and severe local storm, synoptic conditions favourable for thunderstorm, concepts of triggering mechanism, conditional instability; Norwesters, dust storm, hail storm. Squall, tornado, microburst/cloudburst, landslide. ❖ Indian summer monsoon; S.W. Monsoon onset: semi permanent systems, Active and break monsoon, Monsoon depressions: MTC; Offshore troughs/vortices. Influence of extra tropical troughs and typhoons in northwest Pacific; withdrawal of S.W. Monsoon, Northeast monsoon, ❖ Tropical Cyclone: Life cycle, vertical and horizontal structure of TC, Its movement and intensification. Weather associated with TC. Easterly wave and its structure and associated weather. ❖ Jet Streams – WMO definition of Jet stream, different jet streams around the globe, Jet streams and weather ❖ Meso-scale meteorology, sea and land breezes, mountain/valley winds, mountain wave. ❖ Short range weather forecasting (Elementary ideas only); persistence, climatology and steering methods, movement and development of synoptic scale systems; Analogue techniques- prediction of individual weather elements, visibility, surface and upper level winds, convective phenomena. -
Chapter 3 Mesoscale Processes and Severe Convective Weather
CHAPTER 3 JOHNSON AND MAPES Chapter 3 Mesoscale Processes and Severe Convective Weather RICHARD H. JOHNSON Department of Atmospheric Science. Colorado State University, Fort Collins, Colorado BRIAN E. MAPES CIRESICDC, University of Colorado, Boulder, Colorado REVIEW PANEL: David B. Parsons (Chair), K. Emanuel, J. M. Fritsch, M. Weisman, D.-L. Zhang 3.1. Introduction tion, mesoscale phenomena occur on horizontal scales between ten and several hundred kilometers. This Severe convective weather events-tornadoes, hail range generally encompasses motions for which both storms, high winds, flash floods-are inherently mesoscale ageostrophic advections and Coriolis effects are im phenomena. While the large-scale flow establishes envi portant (Emanuel 1986). In general, we apply such a ronmental conditions favorable for severe weather, pro definition here; however, strict application is difficult cesses on the mesoscale initiate such storms, affect their since so many mesoscale phenomena are "multiscale." evolution, and influence their environment. A rich variety For example, a -100-km-Iong gust front can be less of mesocale processes are involved in severe weather, than -1 km across. The triggering of a storm by the ranging from environmental preconditioning to storm initi collision of gust fronts can actually occur on a ation to feedback of convection on the environment. In the -lOO-m scale (the microscale). Nevertheless, we will space available, it is not possible to treat all of these treat this overall process (and others similar to it) as processes in detail. Rather, we will introduce s~veral mesoscale since gust fronts are generally regarded as general classifications of mesoscale processes relatmg to mesoscale phenomena. -
1 Jp2.2 a Case Study of a Wake Low in Northern Illinois And
JP2.2 A CASE STUDY OF A WAKE LOW IN NORTHERN ILLINOIS AND THE WRF PREDICTION OF THE WAKE LOW William Wilson * National Weather Service, Chicago, Illinois Erik Janzon Northern Illinois University We ran four test runs. At 06 UTC A wake low occurred in northern Illinois initialization time one run was using an and southern Wisconsin, during the 11.7 km grid spacing and the other run morning of May 30, 2008. The surface using a 3.4 km grid spacing. At 12 UTC wind was 45 to 55 mph (22 to 28 m/s) initialization, one run was using a 11.7 with gusts to 65 mph (33 m/s). The wind km grid spacing and the other run was was not forecasted or expected. using a 3.4 km grid spacing. The time Forecasters had to quickly issue wind period of the WRF model runs were a 15 warnings as the strong wind was hour run with initialization at 06 UTC occurring. We hope to find ways to and a 12 hour model run with predict wake lows of this strength so to initialization at 12 UTC. We wanted to give forecasters some lead time or investigate the initialization effects on anticipation of wake low development. the wake low production, and the effect The Weather Research and Forecasting of grid spacing. The 3.4 km grid spacing (WRF), Advanced Research WRF model run was without the Kain and (ARW) model is used as a local Fritch convective scheme (Kain and operational model at the National Fritsch, 1990). -
Flash Flooding
NationalNational OceanicOceanic andand AtmosphericAtmospheric AdministrationAdministration (NOAA)(NOAA) NationalNational WeatherWeather ServiceService (NWS)(NWS) PresentsPresents SevereSevere WeatherWeather ObserverObserver andand SafetySafety TrainingTraining 20052005 Severe Weather Spotter Line 1-888-668-3344 Spotter Reports E-mail: www.crh.noaa.gov/espotter Homepage Address: www.crh.noaa.gov/iwx 2 GoalsGoals ofof thethe TrainingTraining You will learn: • Definitions of important weather terms and severe weather criteria • How thunderstorms develop and why some become severe • How to correctly identify cloud features that may or may not be associated with severe weather • What information the observer is to report and how to report it • Ways to receive weather information before and during severe weather events • Observer Safety! 3 WFOWFO NorthernNorthern IndianaIndiana (WFO(WFO IWX)IWX) CountyCounty WarningWarning andand ForecastForecast AreaArea (CWFA)(CWFA) Work with public, state and local officials Dedicated team of highly trained professionals 24 hours a day/7 days a week Prepare forecasts and warnings for 2.3 million people in 37 counties 4 SKYWARNSKYWARN (Severe(Severe Weather)Weather) ObserversObservers Why Are You Critical to NWS Operations? • Help overcome Doppler Radar limitations • Provide ground truth which can be correlated with radar signatures prior to, during, and after severe weather • Ground truth reports in warnings heighten public awareness and allow us to have confidence in our warning decisions 5 SKYWARNSKYWARN (Severe(Severe Weather)Weather) ObserversObservers Why Are You Critical to NWS Operations? • The NWS receives hundreds of reports of “False” or “Mis-Identified” funnel clouds and tornadoes each year • We strongly rely on the “2 out of 3” Rule before issuing a warning. Of the following, we like to have 2 out of 3 present before sending out a warning. -
Synoptic Conditions Favorable for the Formation of the 15 July 1995 Southeastern Canada/Northeastern U.S
SYNOPTIC CONDITIONS FAVORABLE FOR THE FORMATION OF THE 15 JULY 1995 SOUTHEASTERN CANADA/NORTHEASTERN U.S. DERECHO EVENT Mace L. Bentley Climatology Research Laboratory Department of Geography The University of Georgia Athens, Georgia Abstract On 15 July 1995, a derecho-producing mesoscale convective system inflicted considerable damage through southeastern Canada and the northeastern U.S. The synoptic-scale environ ment that precluded and persisted during this event is examined \ using swface and upper-air observations, satellite imagery v""--- and numerical model data. Evidence suggests that low-level ~~- - . -,.~ .... moisture inflow and forcing were major factors in initiating \ .-..... ~".... ". and sustaining this progressive warm season derecho event. : "?-.,. ~.:"... Favorable upper-level dynamics produced by jet streak induced Kingston. Ontario circulations were also found over the region. Products from ..------------.:t i the Eta model run initialized 12 hours prior to the event were ". used in the study to fill in between the 0000 UTC and 1200 UTC upper-air sounding times. Manipulation of these data sets was accomplished using GEMPAK 5.2.1. Calculation of 850 hPa moisture transport vectors andfrontogenesis were found to be particularly useful in determining the derecho producing mesoscale convective system's genesis and propagation regions. Future investiga tions of these systems should employ these techniques in order to assess their forecast applications. Fig. 1. Approximate track of the DMCS cloud shield on 15 July 1995. 1. Introduction In the early morning hours of 15 July 1995, a derecho producing mesoscale convective system (hereafter, DMCS) moved from southern Canada through the northeastern United States (Fig. 1). Widespread wind damage was reported through out the Northeast.