Chapter 3 Mesoscale Processes and Severe Convective Weather
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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). -
How Does Convective Self-Aggregation Affect Precipitation Extremes?
EGU21-5216 https://doi.org/10.5194/egusphere-egu21-5216 EGU General Assembly 2021 © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License. How does convective self-aggregation affect precipitation extremes? Nicolas Da Silva1, Sara Shamekh2, Caroline Muller2, and Benjamin Fildier2 1Centre for Ocean and Atmospheric Sciences, School of Environmental Sciences, University of East Anglia, Norwich, United Kingdom 2Laboratoire de Météorologie Dynamique (LMD)/Institut Pierre Simon Laplace (IPSL), École Normale Supérieure, Paris Sciences & Lettres (PSL) Research University, Sorbonne Université, École Polytechnique, CNRS, Paris, France Convective organisation has been associated with extreme precipitation in the tropics. Here we investigate the impact of convective self-aggregation on extreme rainfall rates. We find that convective self-aggregation significantly increases precipitation extremes, for 3-hourly accumulations but also for instantaneous rates (+ 30 %). We show that this latter enhanced instantaneous precipitation is mainly due to the local increase in relative humidity which drives larger accretion efficiency and lower re-evaporation and thus a higher precipitation efficiency. An in-depth analysis based on an adapted scaling of precipitation extremes, reveals that the dynamic contribution decreases (- 25 %) while the thermodynamic is slightly enhanced (+ 5 %) with convective aggregation, leading to lower condensation rates (- 20 %). When the atmosphere is more organized into a moist convecting region, and a dry convection-free region, deep convective updrafts are surrounded by a warmer environment which reduces convective instability and thus the dynamic contribution. The moister boundary-layer explains the positive thermodynamic contribution. The microphysic contribution is increased by + 50 % with aggregation. The latter is partly due to reduced evaporation of rain falling through a moister near-cloud environment (+ 30 %), but also to the associated larger accretion efficiency (+ 20 %). -
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. -
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. -
Employing the WSR-88D for Waterspout Forecasting
Employing the WSR-88D for Waterspout Forecasting Scott M. Spratt LT (jg) Barry K. Choy, NOAA Corps National Weather Service Melbourne, Florida 1. Introduction Waterspouts and weak coastal tornadoes or "landspouts" (hereafter referred to collectively as "spouts") account for much of Florida's severe weather during the "wet season" (Schmocker et al. 1990). The Melbourne NEXRAD Weather Service Office (NWSO) County Warning Area (CWA) includes 160 miles of coastline along the east central Florida peninsula. Within this area, spouts are most frequent from June through September (Fig. 1). In the past, warnings were issued for spouts only after reports of visual sightings were received. This delay was likely due to the seemingly benign atmospheric conditions in which spouts develop, combined with a lack of pronounced severe weather signatures on conventional radars. However, recent research utilizing the NWSO MLB WSR- 88D may now help forecasters warn for spouts prior to receiving visual reports. A preliminary forecast strategy was developed based on post analyses of archived WSR- 88D products and regional upper-air data from reported spout days (Choy and Spratt 1994). This strategy has proved useful by providing additional lead time for spout events. This paper will identify specific atmospheric conditions which have been observed to precede spout generations along the east central Florida coast. A unique WSR-88D Routine Product Set (RPS) list will be shown which can be implemented once these conditions become satisfied. Finally, case studies of two recent events will be illustrated to help familiarize WSR-88D users with the environmental conditions and radar signatures often evident prior to and during spout events. -
Evidence of Fire in the Pliocene Arctic in Response to Elevated CO2 and Temperature
1 Evidence of fire in the Pliocene Arctic in response to elevated CO2 and temperature 2 Tamara Fletcher1*, Lisa Warden2*, Jaap S. Sinninghe Damsté2,3, Kendrick J. Brown4,5, Natalia 3 Rybczynski6,7, John Gosse8, and Ashley P Ballantyne1 4 1 College of Forestry and Conservation, University of Montana, Missoula, 59812, USA 5 2 Department of Marine Microbiology and Biogeochemistry, NIOZ Royal Netherlands Institute for Sea Research, Den 6 Berg, 1790, Netherlands 7 3 Department of Earth Sciences, University of Utrecht, Utrecht, 3508, Netherlands 8 4 Natural Resources Canada, Canadian Forest Service, Victoria, V8Z 1M, Canada 9 5 Department of Earth, Environmental and Geographic Science, University of British Columbia Okanagan, Kelowna, 10 V1V 1V7, Canada 11 6 Department of Palaeobiology, Canadian Museum of Nature, Ottawa, K1P 6P4, Canada 12 7 Department of Biology & Department of Earth Sciences, Carleton University, Ottawa, K1S 5B6, Canada 13 8 Department of Earth Sciences, Dalhousie University, Halifax, B3H 4R2, Canada 14 *Authors contributed equally to this work 15 Correspondence to: Tamara Fletcher ([email protected]) 16 Abstract. The mid-Pliocene is a valuable time interval for understanding the mechanisms that determine equilibrium 17 climate at current atmospheric CO2 concentrations. One intriguing, but not fully understood, feature of the early to 18 mid-Pliocene climate is the amplified arctic temperature response. Current models underestimate the degree of 19 warming in the Pliocene Arctic and validation of proposed feedbacks is limited by scarce terrestrial records of climate 20 and environment, as well as discrepancies in current CO2 proxy reconstructions. Here we reconstruct the CO2, summer 21 temperature and fire regime from a sub-fossil fen-peat deposit on west-central Ellesmere Island, Canada, that has been 22 chronologically constrained using radionuclide dating to 3.9 +1.5/-0.5 Ma. -
Downloaded 09/29/21 11:17 PM UTC 4144 MONTHLY WEATHER REVIEW VOLUME 128 Ferentiate Among Our Concerns About the Application of TABLE 1
DECEMBER 2000 NOTES AND CORRESPONDENCE 4143 The Intricacies of Instabilities DAVID M. SCHULTZ NOAA/National Severe Storms Laboratory, Norman, Oklahoma PHILIP N. SCHUMACHER NOAA/National Weather Service, Sioux Falls, South Dakota CHARLES A. DOSWELL III NOAA/National Severe Storms Laboratory, Norman, Oklahoma 19 April 2000 and 30 May 2000 ABSTRACT In response to Sherwood's comments and in an attempt to restore proper usage of terminology associated with moist instability, the early history of moist instability is reviewed. This review shows that many of Sherwood's concerns about the terminology were understood at the time of their origination. De®nitions of conditional instability include both the lapse-rate de®nition (i.e., the environmental lapse rate lies between the dry- and the moist-adiabatic lapse rates) and the available-energy de®nition (i.e., a parcel possesses positive buoyant energy; also called latent instability), neither of which can be considered an instability in the classic sense. Furthermore, the lapse-rate de®nition is really a statement of uncertainty about instability. The uncertainty can be resolved by including the effects of moisture through a consideration of the available-energy de®nition (i.e., convective available potential energy) or potential instability. It is shown that such misunderstandings about conditional instability were likely due to the simpli®cations resulting from the substitution of lapse rates for buoyancy in the vertical acceleration equation. Despite these valid concerns about the value of the lapse-rate de®nition of conditional instability, consideration of the lapse rate and moisture separately can be useful in some contexts (e.g., the ingredients-based methodology for forecasting deep, moist convection). -
How Appropriate They Are/Will Be Using Future Satellite Data Sources?
Different Convective Indices - - - How appropriate they are/will be using future satellite data sources? Ralph A. Petersen1 1 Cooperative Institute for Meteorological Satellite Studies (CIMSS), University of Wisconsin – Madison, Madison, Wisconsin, USA Will additional input from Steve Weiss, NOAA/NWS/Storm Prediction Center ✓ Increasing the Utility / Value of real-time Satellite Sounder Products to fill gaps in their short-range forecasting processes Creating Temperature/Moisture Soundings from Infra-Red (IR) Satellite Observations A Conceptual Tutorial All level of the atmosphere is continually emit radiation toward space. Satellites observe the net amount reaching space. • Conceptually, we can think about the atmosphere being made up of many thin layers Start from the bottom and work up. 1 – The greatest amount of radiation is emitted from the earth’s surface 4 - Remember, Stefan’s Law: Emission ~ σTSfc 2 – Molecules of various gases in the lowest layer of the atmosphere absorb some of the radiation and then reemit it upward to space and back downward to the earth’s surface - Major absorbers are CO2 and H2O 4 - Emission again ~ σT , but TAtmosphere<TSfc - Amount of radiation decreases with altitude Creating Temperature/Moisture Soundings from Infra-Red (IR) Satellite Observations A Conceptual Tutorial All level of the atmosphere is continually emit radiation toward space. Satellites observe the net amount reaching space. • Conceptually, we can think about the atmosphere being made up of many thin layers Start from the bottom and work -
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. -
Coniglio Et Al. (2006)
P1.30 FORECASTING THE SPEED AND LONGEVITY OF SEVERE MESOSCALE CONVECTIVE SYSTEMS Michael C. Coniglio∗1 and Stephen F. Corfidi2 1NOAA/National Severe Storms Laboratory, Norman, OK 2NOAA/Storm Prediction Center, Norman, OK 1. INTRODUCTION b. MCS maintenance Forecasting the details of mesoscale convective Predicting MCS maintenance is fraught with systems (MCSs) (Zipser 1982) continues to be a difficult challenges such as understanding how deep convection problem. Recent advances in numerical weather is sustained through system/environment interactions prediction models and computing power have allowed (Weisman and Rotunno 2004, Coniglio et al. 2004b, for explicit real-time prediction of MCSs over the past Coniglio et al. 2005), how pre-existing mesoscale few years, some of which have supported field features influence the system (Fritsch and Forbes 2001, programs (Davis et al. 2004) and collaborative Trier and Davis 2005), and how the disturbances experiments between researchers and forecasters at generated by the system itself can alter the system the Storm Prediction Center (SPC) (Kain et al. 2005). structure and longevity (Parker and Johnson 2004c). While these numerical forecasts of MCSs are promising, the utility of these forecasts and how to best use the From an observational perspective, Evans and capabilities of the high-resolution models in support of Doswell (2001) suggest that the strength of the mean operations is unclear, especially from the perspective of wind (0-6 km) and its effects on cold pool development the Storm Prediction Center (SPC) (Kain et al. 2005). and MCS motion play a significant role in sustaining Therefore, refining our knowledge of the interactions of long-lived forward-propagating MCSs that produce MCSs with their environment remains central to damaging surface winds (derechos) through modifying advancing our near-term ability to forecast MCSs.