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Rezaul Mahmood
,
Megan Schargorodski
,
Eric Rappin
,
Melissa Griffin
,
Patrick Collins
,
Kevin Knupp
,
Andrew Quilligan
,
Ryan Wade
, and
Kevin Cary

Abstract

A total solar eclipse traversed the continental United States on 21 August 2017. It was the first such event in 99 years and provided a rare opportunity to observe the atmospheric response from a variety of instrumented observational platforms. This paper discusses the high-quality observations collected by the Kentucky Mesonet (www.kymesonet.org), a research-grade meteorological and climatological observation network consisting of 72 stations and measuring air temperature, precipitation, relative humidity, solar radiation, wind speed, and wind direction. The network samples the atmosphere, for most variables, every 3 s and then calculates and records observations every 5 min. During the total solar eclipse, these observations were complemented by observations collected from three atmospheric profiling systems positioned in the path of the eclipse and operated by the University of Alabama in Huntsville (UAH). Observational data demonstrate that solar radiation at the surface dropped from >800 to 0 W m‒2, the air temperature decreased by about 4.5°C, and, most interestingly, a land-breeze–sea-breeze-type wind developed. In addition, due to the high density of observations, the network recorded a detailed representation of the spatial variation of surface meteorology. The UAH profiling system captured collapse and reformation of the planetary boundary layer and related changes during the total solar eclipse.

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Rezaul Mahmood
,
Megan Schargorodski
,
Eric Rappin
,
Melissa Griffin
,
Patrick Collins
,
Kevin Knupp
,
Andrew Quilligan
,
Ryan Wade
,
Kevin Cary
, and
Stuart Foster
Full access
Timothy A. Coleman
,
Kevin R. Knupp
,
James Spann
,
J. B. Elliott
, and
Brian E. Peters

Since the successful tornado forecast at Tinker AFB in 1948 paved the way for the issuance of tornado warnings, the science of tornado detection and forecasting has advanced greatly. However, tornado warnings must be disseminated to the public to be of any use. The Texas tornado warning conferences in 1953 began to develop the framework for a modern tornado warning system and included radar detection of tornadoes, a spotter network, and improved communications between the U.S. Weather Bureau, spotters, and public officials, allowing more timely warnings and dissemination of those warnings to the public.

Commercial radio and television are a main source of warnings for many, and the delivery methods on TV have changed much since 1960. NOAA Weather Radio (NWR) was launched after the 1974 Super Outbreak of tornadoes, with the most important feature being the tone alert that allowed receivers to alert people even when the radio broadcast was turned off. Today, NWR reaches most of the U.S. population, and Specific Area Message Encoding technology has improved its warning precision. Outdoor warning sirens, originally designed for use in enemy attack, were made available for use during tornado warnings around 1970.

“Storm based” warnings, adopted by the National Weather Service in 2007, replaced countybased warnings and greatly reduce the warning area. As communications advances continue, tornado warnings will eventually be delivered to precise locations, using GPS and other location technology, through cellular telephones, outdoor sirens, e-mails, and digital television, in addition to NWR.

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David A. R. Kristovich
,
Richard D. Clark
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Jeffrey Frame
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Bart Geerts
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Kevin R. Knupp
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Karen A. Kosiba
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Neil F. Laird
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Nicholas D. Metz
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Justin R. Minder
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Todd D. Sikora
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W. James Steenburgh
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Scott M. Steiger
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Joshua Wurman
, and
George S. Young

Abstract

Intense lake-effect snowstorms regularly develop over the eastern Great Lakes, resulting in extreme winter weather conditions with snowfalls sometimes exceeding 1 m. The Ontario Winter Lake-effect Systems (OWLeS) field campaign sought to obtain unprecedented observations of these highly complex winter storms.

OWLeS employed an extensive and diverse array of instrumentation, including the University of Wyoming King Air research aircraft, five university-owned upper-air sounding systems, three Center for Severe Weather Research Doppler on Wheels radars, a wind profiler, profiling cloud and precipitation radars, an airborne lidar, mobile mesonets, deployable weather Pods, and snowfall and particle measuring systems. Close collaborations with National Weather Service Forecast Offices during and following OWLeS have provided a direct pathway for results of observational and numerical modeling analyses to improve the prediction of severe lake-effect snowstorm evolution. The roles of atmospheric boundary layer processes over heterogeneous surfaces (water, ice, and land), mixed-phase microphysics within shallow convection, topography, and mesoscale convective structures are being explored.

More than 75 students representing nine institutions participated in a wide variety of data collection efforts, including the operation of radars, radiosonde systems, mobile mesonets, and snow observation equipment in challenging and severe winter weather environments.

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Kevin R. Knupp
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Todd A. Murphy
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Timothy A. Coleman
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Ryan A. Wade
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Stephanie A. Mullins
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Christopher J. Schultz
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Elise V. Schultz
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Lawrence Carey
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Adam Sherrer
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Eugene W. McCaul Jr.
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Brian Carcione
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Stephen Latimer
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Andy Kula
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Kevin Laws
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Patrick T. Marsh
, and
Kim Klockow

By many metrics, the tornado outbreak on 27 April 2011 was the most significant tornado outbreak since 1950, exceeding the super outbreak of 3–4 April 1974. The number of tornadoes over a 24-h period (midnight to midnight) was 199; the tornado fatalities and injuries were 316 and more than 2,700, respectively; and the insurable loss exceeded $4 billion (U.S. dollars). In this paper, we provide a meteorological overview of this outbreak and illustrate that the event was composed of three mesoscale events: a large early morning quasi-linear convective system (QLCS), a midday QLCS, and numerous afternoon supercell storms. The main data sources include NWS and research radars, profilers, surface measurements, and photos and videos of the tornadoes. The primary motivation for this preliminary research is to document the diverse characteristics (e.g., tornado characteristics and mesoscale organization of deep convection) of this outbreak and summarize preliminary analyses that are worthy of additional research on this case.

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Christopher Davis
,
Nolan Atkins
,
Diana Bartels
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Lance Bosart
,
Michael Coniglio
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George Bryan
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William Cotton
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David Dowell
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Brian Jewett
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Robert Johns
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David Jorgensen
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Jason Knievel
,
Kevin Knupp
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Wen-Chau Lee
,
Gregory McFarquhar
,
James Moore
,
Ron Przybylinski
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Robert Rauber
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Bradley Smull
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Robert Trapp
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Stanley Trier
,
Roger Wakimoto
,
Morris Weisman
, and
Conrad Ziegler

The Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX) is a research investigation using highly mobile platforms to examine the life cycles of mesoscale convective systems. It represents a combination of two related investigations to study (a) bow echoes, principally those that produce damaging surface winds and last at least 4 h, and (b) larger convective systems that produce long-lived mesoscale convective vortices (MCVs). The field phase of BAMEX utilized three instrumented research aircraft and an array of mobile ground-based instruments. Two long-range turboprop aircraft were equipped with pseudo-dual-Doppler radar capability, the third aircraft was a jet equipped with dropsondes. The aircraft documented the environmental structure of mesoscale convective systems (MCSs), observed the kinematic and thermodynamic structure of the convective line and stratiform regions (where rear-inflow jets and MCVs reside), and captured the structure of mature MCVs. The ground-based instruments augmented sounding coverage and documented the thermodynamic structure of the PBL, both within MCSs and in their environment. The present article reviews the scientific goals of the study and the facility deployment strategy, summarizes the cases observed, and highlights the forthcoming significant research directions and opportunities.

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Todd McKinney
,
Nick Perlaky
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Evan Danielson
,
Areeb Mohammed
,
Jackson Lee
,
Ben O’Bryan
,
Connor Stoll
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Clara Hochmuth
,
Tyler Gallien
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Skyler Kerr
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Timothy Johnson
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Chris Shiffer
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Sean Hassler
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Ethan Jankens
,
Mariama Feaster
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Connor Morris
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Zeb Leffler
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Alice Crawford
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Mark Cohen
,
Michael Newchurch
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Bill Brown
,
Paula Tucker
, and
Kevin Knupp

Abstract

Students from the University of Alabama in Huntsville successfully deployed three micro superpressure balloon satellites in winter 2021. Students planned and implemented all phases of the project: obtaining funding, determining project timelines, preparing equipment, launching balloons, designing and implementing a website, writing daily blogs on the balloon progress, and analyzing the data. The objective of the flights was to use the balloons as a meteorological tool to study conditions in the lower stratosphere (12–14 km), as a tracer for evaluating modeled air parcel trajectories, and as an outreach and educational tool. The three balloons successfully traveled hundreds of thousands of kilometers, making an accumulated total of 16 global circumnavigations. Throughout the project, students made connections with hundreds of researchers, ham radio operators, STEM groups, and other students around the globe. The balloons provided velocity telemetry within many different weather regimes, including vigorous jets over the Himalayas, slow-moving equatorial air masses over the middle of the Pacific Ocean, and dense polar air masses over the Arctic Circle. This study has found that the accuracy of HYSPLIT-calculated trajectories using numerical weather predication (NWP) meteorological data can be quantified using parcel velocity, duration of trajectory forecast, and spatial resolution of the NWP model.

Free access
Bart Geerts
,
David Parsons
,
Conrad L. Ziegler
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Tammy M. Weckwerth
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Michael I. Biggerstaff
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Richard D. Clark
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Michael C. Coniglio
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Belay B. Demoz
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Richard A. Ferrare
,
William A. Gallus Jr.
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Kevin Haghi
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John M. Hanesiak
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Petra M. Klein
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Kevin R. Knupp
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Karen Kosiba
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Greg M. McFarquhar
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James A. Moore
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Amin R. Nehrir
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Matthew D. Parker
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James O. Pinto
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Robert M. Rauber
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Russ S. Schumacher
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David D. Turner
,
Qing Wang
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Xuguang Wang
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Zhien Wang
, and
Joshua Wurman

Abstract

The central Great Plains region in North America has a nocturnal maximum in warm-season precipitation. Much of this precipitation comes from organized mesoscale convective systems (MCSs). This nocturnal maximum is counterintuitive in the sense that convective activity over the Great Plains is out of phase with the local generation of CAPE by solar heating of the surface. The lower troposphere in this nocturnal environment is typically characterized by a low-level jet (LLJ) just above a stable boundary layer (SBL), and convective available potential energy (CAPE) values that peak above the SBL, resulting in convection that may be elevated, with source air decoupled from the surface. Nocturnal MCS-induced cold pools often trigger undular bores and solitary waves within the SBL. A full understanding of the nocturnal precipitation maximum remains elusive, although it appears that bore-induced lifting and the LLJ may be instrumental to convection initiation and the maintenance of MCSs at night.

To gain insight into nocturnal MCSs, their essential ingredients, and paths toward improving the relatively poor predictive skill of nocturnal convection in weather and climate models, a large, multiagency field campaign called Plains Elevated Convection At Night (PECAN) was conducted in 2015. PECAN employed three research aircraft, an unprecedented coordinated array of nine mobile scanning radars, a fixed S-band radar, a unique mesoscale network of lower-tropospheric profiling systems called the PECAN Integrated Sounding Array (PISA), and numerous mobile-mesonet surface weather stations. The rich PECAN dataset is expected to improve our understanding and prediction of continental nocturnal warm-season precipitation. This article provides a summary of the PECAN field experiment and preliminary findings.

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