A Mesoscale Convective Complex Type Storm Over the Desert Southwest
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The Generation of a Mesoscale Convective System from Mountain Convection
JUNE 1999 TUCKER AND CROOK 1259 The Generation of a Mesoscale Convective System from Mountain Convection DONNA F. T UCKER Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas N. ANDREW CROOK National Center for Atmospheric Research Boulder, Colorado (Manuscript received 18 November 1997, in ®nal form 13 July 1998) ABSTRACT A mesoscale convective system (MCS) that formed just to the east of Denver is investigated with a nonhy- drostatic numerical model to determine which processes were important in its initiation. The MCS developed from out¯ow from previous convective activity in the Rocky Mountains to the west. Model results indicate that this out¯ow was necessary for the development of the MCS even though a convergence line was already present in the area where the MCS developed. A simulation with a 3-km grid spacing more fully resolves the convective activity in the mountains but the development of the MCS can be simulated with a 6.67-km grid. Cloud effects on solar radiation and ice sedimentation both in¯uence the strength of the out¯ow from the mountain convection but only the ice sedimentation makes a signi®cant impact on the development of the MCS after its initiation. The frequent convective activity in the Rocky Mountains during the warm season provides out¯ow that would make MCS generation favorable in this region. Thus, there is a close connection between mountain convective activity and MCS generation. The implications of such a connection are discussed and possible directions of future research are indicated. 1. Introduction scale or mesoscale. Forced lifting always occurs on the windward side of mountains; however, the mechanisms Mesoscale convective systems (MCSs) commonly de- that promote lifting on the downwind side of mountains, velop in the central United States during the warm sea- where a large proportion of MCSs initiate, are not as son, accounting for 30%±70% of the summer precipi- obvious. -
The Impact of Outflow Environment on Tropical Cyclone Intensification And
VOLUME 68 JOURNAL OF THE ATMOSPHERIC SCIENCES FEBRUARY 2011 The Impact of Outflow Environment on Tropical Cyclone Intensification and Structure ERIC D. RAPPIN Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, Miami, Florida MICHAEL C. MORGAN AND GREGORY J. TRIPOLI University of Wisconsin—Madison, Madison, Wisconsin (Manuscript received 3 October 2008, in final form 5 June 2009) ABSTRACT In this study, the impacts of regions of weak inertial stability on tropical cyclone intensification and peak strength are examined. It is demonstrated that weak inertial stability in the outflow layer minimizes an energy sink of the tropical cyclone secondary circulation and leads to more rapid intensification to the maximum potential intensity. Using a full-physics, three-dimensional numerical weather prediction model, a symmetric distribution of environmental inertial stability is generated using a variable Coriolis parameter. It is found that the lower the value of the Coriolis parameter, the more rapid the strengthening. The lower-latitude simulation is shown to have a significantly stronger secondary circulation with intense divergent outflow against a com- paratively weak environmental resistance. However, the impacts of differences in the gradient wind balance between the different latitudes on the core structure cannot be neglected. A second study is then conducted using an asymmetric inertial stability distribution generated by the presence of a jet stream to the north of the tropical cyclone. The initial intensification is similar, or even perhaps slower, in the presence of the jet as a result of increased vertical wind shear. As the system evolves, convective outflow from the tropical cyclone modifies the jet resulting in weaker shear and more rapid intensification of the tropical cyclone–jet couplet. -
An Observational Analysis Quantifying the Distance of Supercell-Boundary Interactions in the Great Plains
Magee, K. M., and C. E. Davenport, 2020: An observational analysis quantifying the distance of supercell-boundary interactions in the Great Plains. J. Operational Meteor., 8 (2), 15-38, doi: https://doi.org/10.15191/nwajom.2020.0802 An Observational Analysis Quantifying the Distance of Supercell-Boundary Interactions in the Great Plains KATHLEEN M. MAGEE National Weather Service Huntsville, Huntsville, AL CASEY E. DAVENPORT University of North Carolina at Charlotte, Charlotte, NC (Manuscript received 11 June 2019; review completed 7 October 2019) ABSTRACT Several case studies and numerical simulations have hypothesized that baroclinic boundaries provide enhanced horizontal and vertical vorticity, wind shear, helicity, and moisture that induce stronger updrafts, higher reflectivity, and stronger low-level rotation in supercells. However, the distance at which a surface boundary will provide such enhancement is less well-defined. Previous studies have identified enhancement at distances ranging from 10 km to 200 km, and only focused on tornado production and intensity, rather than all forms of severe weather. To better aid short-term forecasts, the observed distances at which supercells produce severe weather in proximity to a boundary needs to be assessed. In this study, the distance between a large number of observed supercells and nearby surface boundaries (including warm fronts, stationary fronts, and outflow boundaries) is measured throughout the lifetime of each storm; the distance at which associated reports of large hail and tornadoes occur is also collected. Statistical analyses assess the sensitivity of report distributions to report type, boundary type, boundary strength, angle of interaction, and direction of storm motion relative to the boundary. -
Quantifying the Impact of Synoptic Weather Types and Patterns On
1 Quantifying the impact of synoptic weather types and patterns 2 on energy fluxes of a marginal snowpack 3 Andrew Schwartz1, Hamish McGowan1, Alison Theobald2, Nik Callow3 4 1Atmospheric Observations Research Group, University of Queensland, Brisbane, 4072, Australia 5 2Department of Environment and Science, Queensland Government, Brisbane, 4000, Australia 6 3School of Agriculture and Environment, University of Western Australia, Perth, 6009, Australia 7 8 Correspondence to: Andrew J. Schwartz ([email protected]) 9 10 Abstract. 11 Synoptic weather patterns are investigated for their impact on energy fluxes driving melt of a marginal snowpack 12 in the Snowy Mountains, southeast Australia. K-means clustering applied to ECMWF ERA-Interim data identified 13 common synoptic types and patterns that were then associated with in-situ snowpack energy flux measurements. 14 The analysis showed that the largest contribution of energy to the snowpack occurred immediately prior to the 15 passage of cold fronts through increased sensible heat flux as a result of warm air advection (WAA) ahead of the 16 front. Shortwave radiation was found to be the dominant control on positive energy fluxes when individual 17 synoptic weather types were examined. As a result, cloud cover related to each synoptic type was shown to be 18 highly influential on the energy fluxes to the snowpack through its reduction of shortwave radiation and 19 reflection/emission of longwave fluxes. As single-site energy balance measurements of the snowpack were used 20 for this study, caution should be exercised before applying the results to the broader Australian Alps region. 21 However, this research is an important step towards understanding changes in surface energy flux as a result of 22 shifts to the global atmospheric circulation as anthropogenic climate change continues to impact marginal winter 23 snowpacks. -
Outflow from a Nocturnal Thunderstorm
State Water Survey Division METEOROLOGY SECTION AT THE UNIVERSITY OF ILLINOIS SWS Contract Report 242 OUTFLOW FROM A NOCTURNAL THUNDERSTORM Robert W. Scott Meteorology Section Illinois State Water Survey Technical Report 3 NSF Grant ATM 78-08865 Low Level Convergence and the Prediction of Convective Precipitation November 1980 Champaign IL 61820 The project "Low-level Convergence and the Prediction of Convective Precipitation" is a coordinated research effort by the State Water Survey Division of the Illinois Institute of Natural Resources, the Off ice of Weather Modification Research in the National Oceanic and Atmospheric Adminis tration, and the Department of Environmental Sciences of the University of Virginia. Support of this research has been provided to the State Water Survey by the Atmospheric Research Section, National Science Founda tion, through grant ATM-78-08865. This award includes funds from the Army Research Office and the Air Force Office of Scientific Research of the Department of Defense. OUTFLOW FROM A NOCTURNAL THUNDERSTORM Robert W. Scott Illinois State Water Survey TABLE OF CONTENTS Page LIST OF FIGURES iii ABSTRACT .. v ACKNOWLEDGMENTS vii INTRODUCTION 1 STORM CONDITIONS 2 METEOROLOGICAL FIELDS IN THE NETWORK 8 DISCUSSION 19 REFERENCES 26 -iii- LIST OF FIGURES Figure Page 1 Synoptic analyses on 8-9 August 1979. a. Surface chart at 1900 CDT on 8 August 1979. b. Surface chart at 0700 CDT on 9 August 1979 3 c. 850-mb chart at 1900 CDT on 8 August 1979. d. 850-mb chart at 0700 CDT on 9 August 1979 4 e. 700-mb chart at 1900 CDT on 8 August 1979. -
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. -
The Interactions Between a Midlatitude Blocking Anticyclone and Synoptic-Scale Cyclones That Occurred During the Summer Season
502 MONTHLY WEATHER REVIEW VOLUME 126 NOTES AND CORRESPONDENCE The Interactions between a Midlatitude Blocking Anticyclone and Synoptic-Scale Cyclones That Occurred during the Summer Season ANTHONY R. LUPO AND PHILLIP J. SMITH Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, Indiana 20 September 1996 and 2 May 1997 ABSTRACT Using the Goddard Laboratory for Atmospheres Goddard Earth Observing System 5-yr analyses and the Zwack±Okossi equation as the diagnostic tool, the horizontal distribution of the dynamic and thermodynamic forcing processes contributing to the maintenance of a Northern Hemisphere midlatitude blocking anticyclone that occurred during the summer season were examined. During the development of this blocking anticyclone, vorticity advection, supported by temperature advection, forced 500-hPa height rises at the block center. Vorticity advection and vorticity tilting were also consistent contributors to height rises during the entire life cycle. Boundary layer friction, vertical advection of vorticity, and ageostrophic vorticity tendencies (during decay) consistently opposed block development. Additionally, an analysis of this blocking event also showed that upstream precursor surface cyclones were not only important in block development but in block maintenance as well. In partitioning the basic data ®elds into their planetary-scale (P) and synoptic-scale (S) components, 500-hPa height tendencies forced by processes on each scale, as well as by interactions (I) between each scale, were also calculated. Over the lifetime of this blocking event, the S and P processes were most prominent in the blocked region. During the formation of this block, the I component was the largest and most consistent contributor to height rises at the center point. -
Mesoscale Convective Systems and Their Synoptic-Scale Environment in Finland
182 WEATHER AND FORECASTING VOLUME 30 Mesoscale Convective Systems and Their Synoptic-Scale Environment in Finland ARI-JUHANI PUNKKA Finnish Meteorological Institute, Helsinki, Finland MARJA BISTER Division of Atmospheric Sciences, Department of Physics, University of Helsinki, Helsinki, Finland (Manuscript received 9 December 2013, in final form 14 October 2014) ABSTRACT The environments within which high-latitude intense and nonintense mesoscale convective systems (iMCSs and niMCSs) and smaller thunderstorm clusters (sub-MCSs) develop were studied using proximity soundings. MCS statistics covering 8 years were created by analyzing composite radar imagery. One-third of all systems were intense in Finland and the frequency of MCSs was highest in July. On average, MCSs had a duration of 10.8 h and traveled toward the northeast. Many of the linear MCSs had a southwest–northeast line orienta- tion. Interestingly, a few MCSs were observed to travel toward the west, which is a geographically specific feature of the MCS characteristics. The midlevel lapse rate failed to distinguish the environments of the different event types from each other. However, in MCSs, CAPE and the low-level mixing ratio were higher, the deep-layer-mean wind was stronger, and the lifting condensation level (LCL) was lower than in sub- MCSs. CAPE, low-level mixing ratio, and LCL height were the best discriminators between iMCSs and niMCSs. The mean wind over deep layers distinguished the severe wind–producing events from the nonsevere events better than did the vertical equivalent potential temperature difference or the wind shear in shallow layers. No evidence was found to support the hypothesis that dry air at low- and midlevels would increase the likelihood of severe convective winds. -
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. -
Mesoscale Convective Complexes: an Overview by Harold Reynolds a Report Submitted in Conformity with the Requirements for the De
Mesoscale Convective Complexes: An Overview By Harold Reynolds A report submitted in conformity with the requirements for the degree of Master of Science in the University of Toronto © Harold Reynolds 1990 Table of Contents 1. What is a Mesoscale Convective Complex?........................................................................................ 3 2. Why Study Mesoscale Convective Complexes?..................................................................................3 3. The Internal Structure and Life Cycle of an MCC...............................................................................4 3.1 Introduction.................................................................................................................................... 4 3.2 Genesis........................................................................................................................................... 5 3.3 Growth............................................................................................................................................6 3.4 Maturity and Decay........................................................................................................................ 7 3.5 Heat and Moisture Budgets............................................................................................................ 8 4. Precipitation......................................................................................................................................... 8 5. Mesoscale Warm-Core Vortices....................................................................................................... -
Tropical Cyclone Tauktae
Tropical Cyclone Tauktae - Estimated Impacts Warning 7, 15 May 2021 2100 UTC PDC-1I-7A JTWC Summary: TROPICAL CYCLONE 01A (TAUKTAE), LOCATED APPROXIMATELY 263 NM SOUTH OF MUMBAI, INDIA, HAS TRACKED NORTHWESTWARD AT 07 KNOTS OVER THE PAST SIX HOURS.ANIMATED ENHANCED INFRARED SATELLITE IMAGERY SHOWS THE SYSTEM CONTINUED TO CONSOLIDATE AND HAS BECOME MORE SYMMETRICAL WITH A DEEPENING CENTRAL DENSE OVERCAST AND AN EVOLVING EYE FEATURE.THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE LOW LEVEL CIRCULATION FEATURE IN THE 151703Z AMSU-B 89GHZ PASS AND COMPOSITE WEATHER RADAR LOOP FROM GOA, INDIA.THE INITIAL INTENSITY 65 KNOTS IS BASED ON THE PGTW DVORAK ESTIMATE OF T4.0/65KTS AND ADT OF T3.9/63KTS.THE UPPER-LEVEL ANALYSIS INDICATES FAVORABLE ENVIRONMENTAL CONDITIONS WITH ROBUST POLEWARD OUTFLOW, LOW VERTICAL WIND SHEAR (10-15KTS), AND WARM (31C) SEA SURFACE TEMPERATURE.TC 01A IS TRACKING POLEWARD ALONG THE WESTERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE EAST AND WILL CONTINUE ON ITS CURRENT TRACK THROUGH TAU 36.AFTERWARD, IT WILL TRACK MORE NORTHWARD AND ROUND THE RIDGE AXIS BEFORE MAKING LANDFALL NEAR VERAVAL, INDIA SHORTLY AFTER TAU 48.THE POSSIBILITY OF RAPID INTENSIFICATION (RI) REMAINS HIGH DURING THE NEXT 24 TO 36 HOURS AS THE ENVIRONMENTAL CONDITIONS REMAIN FAVORABLE, REACHING A PEAK INTENSITY OF 105 KNOTS BY TAU 36.AFTERWARD, THE SYSTEM WILL BEGIN TO WEAKEN WITH LAND INTERACTION.AFTER LANDFALL, THE CYCLONE WILL RAPIDLY ERODE AS IT TRACKS ACROSS THE RUGGED TERRAIN, LEADING TO DISSIPATION BY TAU 120, POSSIBLY -
Glossary of Severe Weather Terms
Glossary of Severe Weather Terms -A- Anvil The flat, spreading top of a cloud, often shaped like an anvil. Thunderstorm anvils may spread hundreds of miles downwind from the thunderstorm itself, and sometimes may spread upwind. Anvil Dome A large overshooting top or penetrating top. -B- Back-building Thunderstorm A thunderstorm in which new development takes place on the upwind side (usually the west or southwest side), such that the storm seems to remain stationary or propagate in a backward direction. Back-sheared Anvil [Slang], a thunderstorm anvil which spreads upwind, against the flow aloft. A back-sheared anvil often implies a very strong updraft and a high severe weather potential. Beaver ('s) Tail [Slang], a particular type of inflow band with a relatively broad, flat appearance suggestive of a beaver's tail. It is attached to a supercell's general updraft and is oriented roughly parallel to the pseudo-warm front, i.e., usually east to west or southeast to northwest. As with any inflow band, cloud elements move toward the updraft, i.e., toward the west or northwest. Its size and shape change as the strength of the inflow changes. Spotters should note the distinction between a beaver tail and a tail cloud. A "true" tail cloud typically is attached to the wall cloud and has a cloud base at about the same level as the wall cloud itself. A beaver tail, on the other hand, is not attached to the wall cloud and has a cloud base at about the same height as the updraft base (which by definition is higher than the wall cloud).