Mean synoptic-scale conditions accompanying convective storms that produce hazardous weather phenomena in southern Brazil (SB) and neighboring areas are investigated. Emphasis is placed on ...discriminating between conditions conducive to tornadoes (TORN) and those to heavy rainfall (RAIN) and non-tornadic wind gusts (GUST). For this purpose, an analysis of the meteorological conditions associated with 40 events from each severe weather category is conducted using data from CFSR/CFSv2 reanalysis. Data are sampled for times closest to the severe weather event in a 30
∘
×
30
∘
adaptive latitude-longitude domain centered on each event location. Average charts are obtained for the synoptic fields and atmospheric parameters, and mean tropospheric profiles are compared among the distinct hazards. Overall, the role played by a surface low pressure system that extends to SB is highlighted, conditioning the environment to convective storms. This system favors low-level northwesterly moist flow and surface convergence over the center of the domain. Subtle differences are found between the TORN and GUST composites, with the former exhibiting weaker baroclinic forcing but stronger vertical wind shear in the lower troposphere. Distinctions between TORN and RAIN are more pronounced, with TORN exhibiting more intense horizontal pressure gradients, surface-based CAPE, and vertical wind shear. The average wind profile for TORN exhibited the most elongated and curved hodograph at low levels. Convective parameters showed poor discrimination between TORN and GUST, while performing better in discriminating TORN from RAIN, especially the shear parameters computed along the effective inflow layer of the storms.
In recent years, there have been many incidents around the world in which wind turbines were cut-off on a large scale due to severe wind conditions, resulting in huge impacts on the power system and ...seriously affecting the safe and stable operation of the grid. Accordingly, this paper proposes a novel wind turbine control strategy to maximize the load capacity in severe wind conditions, which can track the wind conditions and adjust the wind turbine load in real time to make full use of the transient survivability and power output capacity of wind turbines. Through simulation, it is confirmed that the proposed strategy can effectively reduce the risk of power steep drop in wind farms under severe wind conditions compared with traditional strategies.
Severe thunderstorms affect more than 30 million people living along the shores of Lake Victoria (East Africa). Thousands of fishers lose their lives on the lake every year. While deadly waves are ...assumed to be initiated by severe wind gusts, knowledge about thunderstorms is restricted to precipitation or environmental proxies. Here we use a regional climate model run at convection-permitting resolution to simulate both precipitation and wind gusts over Lake Victoria for a historical 10-year period. In addition, a pseudo global warming simulation provides insight into the region’s future climate. In this simulation, ERA5’s initial and boundary conditions are perturbed with atmospheric changes between 1995–2025 and 2070–2100, projected by CMIP6’s ensemble mean. It was found that future decreases in both mean precipitation and wind gusts over Lake Victoria can be attributed to a weaker mean mesoscale circulation that reduces the trigger for over-lake nighttime convection and decreases the mean wind shear. However, an intensification of extremes is projected for both over-lake precipitation and wind gusts. The observed ∼7 %K−1 Clausius–Clapeyron extreme precipitation scaling is ascribed to increased water vapor content and a compensation of weaker mesoscale circulations and stronger thunderstorm dynamics. More frequent wind gust extremes result from higher wind shear conditions and more compound thunderstorms with both intense rainfall and severe wind gusts. Overall, our study emphasizes Lake Victoria’s modulating role in determining regional current and future extremes, in addition to changes expected from the Clausius–Clapeyron relation.
Tropical cyclones have caused significant damage to low-rise buildings in the Philippines, with severe to complete damages observed in non-engineered houses. As a response, vulnerability assessments ...need to be conducted to identify strategies that will improve the resilience of buildings against the severe wind. This paper presents a methodology for identifying critical key building components and building typologies that can be used for a component-based vulnerability assessment against extreme wind loads. The paper discusses the recommended survey preparations, survey proper and post-survey activities needed to produce vulnerability and fragility curves. The paper focuses on collecting data wherein buildings can be classified into key building typologies based on their key critical components. Furthermore, a discussion on the application of the methodology in the province of Cebu is presented, wherein four new building classifications are proposed in addition to the existing key building typologies identified in previous research for the Philippines. The new classifications are as follows: Reinforced concrete moment frame, open/without walls (C1o), Steel moment frame, open/without walls (S1o), Wood frame with CHB walls (W4), and wall: bottom half concrete and upper half wood (W5). The amended key building types for the Philippines can then be used for risk assessments initiatives wherein the results can be implemented in disaster risk reduction mitigation strategies (DRRM).
Severe wind events which occur in the metropolis of Beijing in China bring major catastrophes. Characteristics of severe winter and spring wind events over Beijing during the past 40 years have been ...analyzed. An artificial intelligence-based method is adopted to categorize the favorable large-scale circulation patterns and dominant weather systems. Four categories are concluded and compared to each other in terms of distributions of geopotential height at 500 hPa, temperature at 500 hPa, sea level pressure and their corresponding anomalies in 1979–2019. It is found that the first category (T1) which is dominated by strong cold trough at upper levels with strong cold-core high locating at surface is the most conducive circulation pattern, while the fourth category (T4) which is controlled by weak trough and strong ridge with strong low cyclone at surface is the least one. The second and third categories, represented by T2 and T3, are under the control of strong cold trough and warm ridge at upper levels with weak high at surface, and of weak trough and strong ridge with strong low cyclone at surface, respectively. Characteristics and differences under different backgrounds of global temperatures are analyzed by separating the past 40years into two distinct periods. The decreasing trends of intensities of the trough and ridge, the temperature at 500hPa, together with the surface systems, are found to be responsible for the decrease in severe wind events in T1, T2 and T3 in the last 20 years, while T4 is distinct to the other three categories with little change in its circulation pattern, and thus continues contributing to the severe wind events over Beijing. The results found in this study with the usage of an AI-based algorithm will benefit for the operational forecasting for extreme wind events over Beijing.
A devastating storm struck southern Manitoba, Canada on 10-13 October 2019, producing a large region of mainly sticky and wet snow. Accumulations reached 75 cm, wind gusts exceeded 100 km h
−1
, and ...surface temperature (T) remained near 0°C (−1°C ≤ T ≤ 1°C) for up to 88 h. It produced the largest October snowfall and was the earliest to produce at least 20 cm since 1872 in Winnipeg. These factors led to unparalleled damage and power restoration challenges for Manitoba Hydro and, with leaves still largely on vegetation, the most damaging storm to Winnipeg's trees ever recorded. The storm's track was uncommon, and produced elevated convection related to buoyancy-driven instability and conditional symmetric instability (CSI), with a moist absolutely unstable layer (MAUL) near 500 hPa. Instabilities were released via lift through lower-tropospheric warm advection and frontogenesis, differential cyclonic vorticity advection, and jet streak dynamics. Precipitation bands, elevated convection, and lake effect snow bands enhanced local snowfall. Snow adhering to structures was not always wet but, when present, it sometimes occurred because of incomplete freezing of particles partially melted aloft in a near-surface (<100 m deep) inversion. Although other storms over the historical record have produced a similar combination of severe precipitation, temperature and wind conditions, none have done this for such a long period.
Severe wind gusts produced by squall lines are difficult to monitor and forecast. This paper assessed and improved the physics-based Brasseur WGE (wind gust estimate) method for diagnosing wind gust ...of squall lines by coupling the WGE methods with the WRF (Weather Research and Forecasting) model. The simulation results show that the Brasseur WGE method accurately captured the strong gust feature with 32 m·s
−1
maximum wind speed during the disastering Shipwreck event occurred over Yangtze River on 1 June 2015, but overestimated the extended area of severe gust speeds. Analysis of the kinematic structure and boundary-layer conditions of the squall line confirmed the theoretical applicability of the Brasseur WGE method for squall lines. A novel gust-front-area limiting method was introduced to modify the Brasseur WGE method, which effectively reduces its gust wind overestimation area. Furthermore, five squall line events occurred in the middle China during 2021 were simulated to test the modified WGE method and the results exhibit significant improvements to the wind gust forecasts, with an average false alarm rate decreased from 0.89 to 0.54, and the critical success index(CSI) increased from 0.1 to 0.4.
Severe convective gusts lead to wind conditions that differ from those of atmospheric boundary layer (ABL) flows. Main differences are high velocities at ground level and transient flow conditions. ...Their interaction with inner-city areas has only rarely been examined and is the aim of the present work. In the experimental study the convective gusts were simulated by a jet, imbedded in an ABL flow generated by a wind-tunnel. The gust impinged on a street canyon model. Both steady experiments (continuous jet) and non-steady experiments (pulsed jet) were conducted. Flow fields within the street canyon were measured by means of a 2D/2C TR-PIV system.
Comparisons of the steady flow field within a street canyon model and for a gust propagation on open terrain revealed an average increase of the maximum horizontal velocity of 50% within the canyon, an increase of the outflow's height, and a conservation of high velocities over a distance more than 3 times larger compared to open terrain conditions. Further experiments with a transient gust included the generation of a ring vortex. This vortex propagates above the street canyon and results in an additional increase of peak velocities.
•High velocities of convective outflows are conserved within the street canyon.•Small convective outflows lead to an increase of wind speed within street canyons.•Small convective outflows increase in height within streets canyons.•Ring vortex of down-gust propagates above the roof level of cities.•Ring vortex leads to an additional increase of wind speed within the streets.
Severe convective phenomena cause significant loss in the economy and, primarily, casualties. Therefore, it is essential to forecast such extreme events to avoid or minimize the negative ...consequences. Wind shear provides an updraft-downdraft separation in the convective cell, which extends the cell lifetime. Wind shears between a few different air layers have been examined in all damaging convective cases in Poland, taken from the European Severe Weather Database between 2011 and 2015, in order to find their values and patterns according to the intensity of this phenomenon. Each severe weather report was assigned wind shear values from the nearest sounding station, and subsequently the presented summary was made. It was found that wind shear values differ between the given phenomena and their intensity. This regularity is particularly visible in shears containing 0 km wind. The highest shears occur within wind reports. Lower values are associated with hail reports. An important difference between weak and F1+ tornadoes was found in most of the wind shears. Severe phenomena probability within 0-6 km and 0-1 km shears show different patterns according to the phenomena and their intensity. This finding has its application in severe weather forecasting.
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