The Unusual Early Morning Tornado in Ciudad Acuña, Coahuila, Mexico, on 25 May 2015

Abstract This study analyzes the synoptic- and mesoscale conditions present during initiation and intensification of the supercell thunderstorm that produced a tornado in Ciudad Acuña, a community located in the state of Coahuila, Mexico, 10 km southwest of the U.S. border. Early morning convective activity, first detected by radar at 0628 UTC 25 May 2015, developed into an intense and well-defined supercell thunderstorm that produced a tornado between approximately 1045 and 1130 UTC. Hourly analyses from the Rapid Refresh model indicated an upslope component to surface flow in the region of convection initiation over the Serranías del Burro (SdB). Along the storm’s trajectory, dewpoint temperatures increased from 15° to 22°C, convective available potential energy increased from 1500 to near 4000 J kg−1, and convective inhibition changed from −150 J kg−1 at the time of convection initiation to near zero in Ciudad Acuña. Simulations from the Weather Research and Forecasting Model confirmed the sensitivity of both convection initiation and storm intensification to the topography of the SdB. In the control simulation and two simulations in which topography was reduced in elevation, a cluster of storms formed and intensified over the central mountains. However, when topography was further reduced and the SdB region became a large flat plain, little convective activity was seen, forming only along the dryline without intensifying or propagating to the east as was observed.

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Dynamic Ensemble Analysis of Frontal Placement Impacts in the Presence of Elevated Thunderstorms during PRECIP Events

Atmosphere ◽

10.3390/atmos9090339 ◽

2018 ◽

Vol 9 (9) ◽

pp. 339 ◽

Cited By ~ 1

Author(s):

Joshua Kastman ◽

Patrick Market ◽

Neil Fox

Keyword(s):

Potential Energy ◽

Convective Available Potential Energy ◽

Wrf Model ◽

Weather Research And Forecasting ◽

Model Ensemble ◽

Field Campaign ◽

Cold Pools ◽

Frontal Zones ◽

Convective Inhibition ◽

Ensemble Analysis

The Program for Research on Elevated Convection with Intense Precipitation (PRECIP) field campaign sampled 10 cases of elevated convection during 2014 and 2015. These intense observing periods (IOP) mostly featured well-defined stationary or warm frontal zones, over whose inversion elevated convection would form. However, not all frontal zones translated as expected, with some poleward motions being arrested and even returning equatorward. Prior analyses of the observed data highlighted the downdrafts in these events, especially diagnostics for their behavior: the downdraft convective available potential energy (DCAPE) and the downdraft convective inhibition (DCIN). With the current study, the DCAPE and DCIN are examined for four cases: two where frontal motion proceeded poleward, as expected, and two where the frontal motions were slowed significantly or stalled altogether. Using the Weather Research and Forecasting (WRF) model, a multi-model ensemble was created for each of the four cases, and the best performing members were selected for additional deterministic examination. Analyses of frontal motions and surface cold pools are explored in the context of DCAPE and DCIN. These analyses further establish the DCAPE and DCIN, not only as a means to classify elevated convection, but also to aid in explaining frontal motions in the presence of elevated convection.

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A Decade of Antarctic Science Support Through Amps

Bulletin of the American Meteorological Society ◽

10.1175/bams-d-11-00186.1 ◽

2012 ◽

Vol 93 (11) ◽

pp. 1699-1712 ◽

Cited By ~ 78

Author(s):

Jordan G. Powers ◽

Kevin W. Manning ◽

David H. Bromwich ◽

John J. Cassano ◽

Arthur M. Cayette

Keyword(s):

Real Time ◽

Numerical Weather Prediction ◽

Weather Prediction ◽

Weather Research And Forecasting ◽

Forecasting Model ◽

Prediction System ◽

Numerical Weather ◽

The Antarctic ◽

The U.S ◽

Weather Research

The Antarctic Mesoscale Prediction System (AMPS) is a real-time numerical weather prediction (NWP) system covering Antarctica that has served a remarkable range of groups and activities for a decade. It employs the Weather Research and Forecasting model (WRF) on varying-resolution grids to generate numerical guidance in a variety of tailored products. While its priority mission has been to support the forecasters of the U.S. Antarctic Program, AMPS has evolved to assist a host of scientific and logistical needs for an international user base. The AMPS effort has advanced polar NWP and Antarctic science and looks to continue this into another decade. To inform those with Antarctic scientific and logistical interests and needs, the history, applications, and capabilities of AMPS are discussed.

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The Influences of Boundary Layer Mixing and Cloud-Radiative Forcing on Tropical Cyclone Size

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-16-0231.1 ◽

2017 ◽

Vol 74 (4) ◽

pp. 1273-1292 ◽

Cited By ~ 13

Author(s):

Yizhe Peggy Bu ◽

Robert G. Fovell ◽

Kristen L. Corbosiero

Keyword(s):

Boundary Layer ◽

Tropical Cyclone ◽

Radiative Forcing ◽

Vertical Mixing ◽

Outer Core ◽

Weather Research And Forecasting ◽

Forecasting Model ◽

Convective Activity ◽

Cloud Radiative Forcing ◽

Mixing Coefficient

Abstract Tropical cyclone (TC) size is an important factor directly and indirectly influencing track, intensity, and related hazards, such as storm surge. Using a semi-idealized version of the operational Hurricane Weather Research and Forecasting Model (HWRF), the authors show that both enabling cloud-radiative forcing (CRF) and enhancing planetary boundary layer (PBL) vertical mixing can encourage wider storms by enhancing TC outer-core convective activity. While CRF acts primarily above the PBL, eddy mixing moistens the boundary layer from below, both making peripheral convection more likely. Thus, these two processes can cooperate and compete, making their influences difficult to deconvolve and complicating the evaluation of model physics improvements, especially since the sensitivity to both decreases as the environment becomes less favorable. Further study shows not only the magnitude of the eddy mixing coefficient but also the shape of it can determine the TC size and structure.

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Geographic Shift and Environment Change of U.S. Tornado Activities in a Warming Climate

Atmosphere ◽

10.3390/atmos12050567 ◽

2021 ◽

Vol 12 (5) ◽

pp. 567

Author(s):

Zuohao Cao ◽

Huaqing Cai ◽

Guang J. Zhang

Keyword(s):

Wind Shear ◽

Convective Available Potential Energy ◽

Geographic Location ◽

Reanalysis Data ◽

Cyclonic Circulation ◽

Upward Motion ◽

Environment Change ◽

Low Level ◽

High Event ◽

The U.S

Even with ever-increasing societal interest in tornado activities engendering catastrophes of loss of life and property damage, the long-term change in the geographic location and environment of tornado activity centers over the last six decades (1954–2018), and its relationship with climate warming in the U.S., is still unknown or not robustly proved scientifically. Utilizing discriminant analysis, we show a statistically significant geographic shift of U.S. tornado activity center (i.e., Tornado Alley) under warming conditions, and we identify five major areas of tornado activity in the new Tornado Alley that were not identified previously. By contrasting warm versus cold years, we demonstrate that the shift of relative warm centers is coupled with the shifts in low pressure and tornado activity centers. The warm and moist air carried by low-level flow from the Gulf of Mexico combined with upward motion acts to fuel convection over the tornado activity centers. Employing composite analyses using high resolution reanalysis data, we further demonstrate that high tornado activities in the U.S. are associated with stronger cyclonic circulation and baroclinicity than low tornado activities, and the high tornado activities are coupled with stronger low-level wind shear, stronger upward motion, and higher convective available potential energy (CAPE) than low tornado activities. The composite differences between high-event and low-event years of tornado activity are identified for the first time in terms of wind shear, upward motion, CAPE, cyclonic circulation and baroclinicity, although some of these environmental variables favorable for tornado development have been discussed in previous studies.

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Land-Use Improvements in the Weather Research and Forecasting Model over Complex Mountainous Terrain and Comparison of Different Grid Sizes

Boundary-Layer Meteorology ◽

10.1007/s10546-021-00617-1 ◽

2021 ◽

Author(s):

Alessio Golzio ◽

Silvia Ferrarese ◽

Claudio Cassardo ◽

Gugliemina Adele Diolaiuti ◽

Manuela Pelfini

Keyword(s):

Boundary Layer ◽

Land Use ◽

Land Cover ◽

Mixing Layer ◽

Local Area ◽

Heat Fluxes ◽

Weather Research And Forecasting ◽

Forecasting Model ◽

Mountainous Terrain ◽

Weather Research

AbstractWeather forecasts over mountainous terrain are challenging due to the complex topography that is necessarily smoothed by actual local-area models. As complex mountainous territories represent 20% of the Earth’s surface, accurate forecasts and the numerical resolution of the interaction between the surface and the atmospheric boundary layer are crucial. We present an assessment of the Weather Research and Forecasting model with two different grid spacings (1 km and 0.5 km), using two topography datasets (NASA Shuttle Radar Topography Mission and Global Multi-resolution Terrain Elevation Data 2010, digital elevation models) and four land-cover-description datasets (Corine Land Cover, U.S. Geological Survey land-use, MODIS30 and MODIS15, Moderate Resolution Imaging Spectroradiometer land-use). We investigate the Ortles Cevadale region in the Rhaetian Alps (central Italian Alps), focusing on the upper Forni Glacier proglacial area, where a micrometeorological station operated from 28 August to 11 September 2017. The simulation outputs are compared with observations at this micrometeorological station and four other weather stations distributed around the Forni Glacier with respect to the latent heat, sensible heat and ground heat fluxes, mixing-layer height, soil moisture, 2-m air temperature, and 10-m wind speed. The different model runs make it possible to isolate the contributions of land use, topography, grid spacing, and boundary-layer parametrizations. Among the considered factors, land use proves to have the most significant impact on results.

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Simulating the meteorology and PM10 concentrations in Arizona dust storms using the Weather Research and Forecasting model with Chemistry (Wrf-Chem)

Journal of the Air & Waste Management Association ◽

10.1080/10962247.2017.1357662 ◽

2018 ◽

Vol 68 (3) ◽

pp. 177-195 ◽

Cited By ~ 3

Author(s):

Peter Hyde ◽

Alex Mahalov ◽

Jialun Li

Keyword(s):

Dust Storms ◽

Weather Research And Forecasting ◽

Forecasting Model ◽

Weather Research

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Parallelization Strategies for the GPS Radio Occultation Data Assimilation with a Nonlocal Operator in the Weather Research and Forecasting Model

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-13-00195.1 ◽

2014 ◽

Vol 31 (9) ◽

pp. 2008-2014 ◽

Cited By ~ 2

Author(s):

Xin Zhang ◽

Ying-Hwa Kuo ◽

Shu-Ya Chen ◽

Xiang-Yu Huang ◽

Ling-Feng Hsiao

Keyword(s):

Data Assimilation ◽

Radio Occultation ◽

Weather Prediction ◽

Weather Research And Forecasting ◽

Forecasting Model ◽

Observation Operator ◽

Gps Radio Occultation ◽

Phase Observation ◽

Excess Phase ◽

Weather Research

Abstract The nonlocal excess phase observation operator for assimilating the global positioning system (GPS) radio occultation (RO) sounding data has been proven by some research papers to produce significantly better analyses for numerical weather prediction (NWP) compared to the local refractivity observation operator. However, the high computational cost and the difficulties in parallelization associated with the nonlocal GPS RO operator deter its application in research and operational NWP practices. In this article, two strategies are designed and implemented in the data assimilation system for the Weather Research and Forecasting Model to demonstrate the capability of parallel assimilation of GPS RO profiles with the nonlocal excess phase observation operator. In particular, to solve the parallel load imbalance problem due to the uneven geographic distribution of the GPS RO observations, round-robin scheduling is adopted to distribute GPS RO observations among the processing cores to balance the workload. The wall clock time required to complete a five-iteration minimization on a demonstration Antarctic case with 106 GPS RO observations is reduced from more than 3.5 h with a single processing core to 2.5 min with 106 processing cores. These strategies present the possibility of application of the nonlocal GPS RO excess phase observation operator in operational data assimilation systems with a cutoff time limit.

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Sea-Breeze Dynamics and Convection Initiation: The Influence of Convective Parameterization in Weather and Climate Model Biases

Journal of Climate ◽

10.1175/jcli-d-14-00850.1 ◽

2015 ◽

Vol 28 (20) ◽

pp. 8093-8108 ◽

Cited By ~ 35

Author(s):

Cathryn E. Birch ◽

Malcolm J. Roberts ◽

Luis Garcia-Carreras ◽

Duncan Ackerley ◽

Michael J. Reeder ◽

...

Keyword(s):

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Sea Breeze ◽

Early Morning ◽

Sea Temperature ◽

Convective Parameterization ◽

Study Approach ◽

Climate Model Simulations ◽

Convection Initiation

Abstract There are some long-established biases in atmospheric models that originate from the representation of tropical convection. Previously, it has been difficult to separate cause and effect because errors are often the result of a number of interacting biases. Recently, researchers have gained the ability to run multiyear global climate model simulations with grid spacings small enough to switch the convective parameterization off, which permits the convection to develop explicitly. There are clear improvements to the initiation of convective storms and the diurnal cycle of rainfall in the convection-permitting simulations, which enables a new process-study approach to model bias identification. In this study, multiyear global atmosphere-only climate simulations with and without convective parameterization are undertaken with the Met Office Unified Model and are analyzed over the Maritime Continent region, where convergence from sea-breeze circulations is key for convection initiation. The analysis shows that, although the simulation with parameterized convection is able to reproduce the key rain-forming sea-breeze circulation, the parameterization is not able to respond realistically to the circulation. A feedback of errors also occurs: the convective parameterization causes rain to fall in the early morning, which cools and wets the boundary layer, reducing the land–sea temperature contrast and weakening the sea breeze. This is, however, an effect of the convective bias, rather than a cause of it. Improvements to how and when convection schemes trigger convection will improve both the timing and location of tropical rainfall and representation of sea-breeze circulations.

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