scholarly journals Observational Analysis of a Wind Gust Event during the Merging of a Bow Echo and Mini-Supercell in Southeastern China

Atmosphere ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1511
Author(s):  
Hui Zheng ◽  
Yuchun Zhao ◽  
Yipeng Huang ◽  
Wei Zhang ◽  
Changrong Luo ◽  
...  
Keyword(s):  
Convective Cell ◽  
Cyclonic Circulation ◽  
Wind Gust ◽  
Southeastern China ◽  
Wind Speeds ◽  
Significant Damage ◽  
Bow Echo ◽  
Layer 4 ◽  
Surface Station ◽  
Differential Reflectivity

The merging of a fast-moving bow echo with a convective cell of a hook-echo signature was studied by using polarimetric radar detections. Gusts with wind speeds near 35 m s–1 were recorded by the surface station, which caused significant damage. A convective cell with a mesovortex signature, which is hereafter referred to as a mini-supercell, was observed over the northeast of the bow echo before the convective merging. It was found that the mesovortex possessed cyclonic circulation and resembled a supercell-like feature. The merging of the bow echo and the mini-supercell strengthened the updraft near the apex of the bow echo. The enhanced updraft was also demonstrated by the appearance of a differential reflectivity (ZDR) column with a topmost height of 4 km above the melting layer (~4 km). The bow was separated into northern and southern sectors after merging with the mini-supercell, leading to the gusty wind over the surface of the south sector.

Dynamic Response Analysis of a Spar Platform Subjected to Wind and Wave Forces

2008 ◽  
Author(s):  
Bernt J. Leira ◽  
Dag Myrhaug ◽  
Jarle Voll
Keyword(s):  
Dynamic Response ◽  
Roughness Parameter ◽  
Response Analysis ◽  
Wave Forces ◽  
Wind Gust ◽  
Wave Age ◽  
Spar Platform ◽  
Dynamic Response Analysis ◽  
Wind Speeds ◽  
Wind Response

Results from a study on dynamic response analysis of a floating production unit (FPSO) excited by wave and wind forces are presented. The FPSO is examplified by a Spar platform considering the motion in surge and pitch. The wind gust is modelled with the Harris [4] and Ochi and Shin [7] wind gust spectra. The effect of the wave age on the wind gust spectrum is included by adopting the Volkov wave age dependent sea surface roughness parameter [10]; the wave age independent Charnock roughness parameter [2] is also used as a reference. Examples of results demonstrate clear effects of wave age on the dynamic response. Moreover, for high mean wind speeds the total wind response is much smaller than the wave response, but for low mean wind speeds the wind appears to be more important.

scholarly journals Polarimetric Radar Observations from a Waterspout-Producing Thunderstorm

2015 ◽  
Vol 30 (2) ◽  
pp. 329-348 ◽  
Author(s):  
Matthew S. Van Den Broeke ◽  
Cynthia A. Van Den Broeke
Keyword(s):  
Lake Michigan ◽  
Convective Cell ◽  
Great Lakes Region ◽  
Polarimetric Radar ◽  
Air Mass ◽  
Radar Observations ◽  
Potential Source ◽  
Western Lake ◽  
Low Levels ◽  
Differential Reflectivity

Abstract A family of four waterspouts was produced by a convective cell over western Lake Michigan on 12 September 2013. This storm initiated along a boundary north of a mesolow in a low-level cold-air advection regime, and developed supercell characteristics once the second waterspout was in progress. Polarimetric characteristics of the storm, and of the development of supercell character, are presented. These observations represent the first documented polarimetric radar observations of waterspout-producing convection in the Great Lakes region. Unusually high differential reflectivity values accompanied this storm and its initiating boundary. The high values along the boundary are partially explained by a high density of dragonflies. High differential reflectivity values were present through much of the storm of interest despite very low aerosol concentration at low levels in the lake-influenced air mass. Finally, this case illustrates the importance of environmental awareness on waterspout-favorable days, especially when boundaries are nearby to serve as a potential source of enhanced environmental vertical vorticity.

Dynamic Response of Articulated Tower Platforms to Random Sea Environment

2009 ◽  
Author(s):  
Mohd Moonis Zaheer ◽  
Nazrul Islam
Keyword(s):  
Dynamic Response ◽  
Excitation Frequency ◽  
Response Analysis ◽  
Wave Forces ◽  
Wind Gust ◽  
Wave Age ◽  
Wind Speeds ◽  
Positive Side ◽  
The Mean ◽  
Low Wind Speeds

Articulated tower motions have been characterized by rigid body mode of vibrations falling in the wind excitation frequency range due to its compliant nature. Dynamic response analysis of a multi hinged articulated tower platform to random wind and wave forces are presented in this paper. The wave forces on the submerged elements of the tower are calculated by using Morison’s Equation. The fluctuating wind is modeled with Ochi and Shin wind gust spectrum. The effect of wave age (young, intermediate and fully developed waves) on the wind gust spectrum is incorporated by adopting the wave age dependent Volkov, and wave age independent Charnock sea surface roughness models. The response of the tower is determined by a time domain iterative method. An example of results demonstrates the clear effect of wave age on the nonlinear dynamic response on the system. The mean wind modifies the mean position of the surge response to the positive side, causing an offset. Moreover, for high mean wind speeds the total wind response is much smaller than the wave response, but for low wind speeds the wind appears to be more important.

scholarly journals High resolution modelling results of the wind flow over Canary Islands during the meteorological situation of the extratropical storm Delta (28–30 November 2005)

2008 ◽  
Vol 2 (1) ◽  
pp. 81-87 ◽  
Author(s):  
O. Jorba ◽  
C. Marrero ◽  
E. Cuevas ◽  
J. M. Baldasano
Keyword(s):  
High Resolution ◽  
Canary Islands ◽  
Large Scale ◽  
Static Stability ◽  
Horizontal Resolution ◽  
Wind Speeds ◽  
Warm Core ◽  
Average Wind ◽  
Significant Damage ◽  
Large Scale Flow

Abstract. On 28–29 November 2005 an extratropical storm affected the Canary Islands causing significant damage related to high average wind speeds and intense gusts over some islands of the archipelago. Delta was the twenty-sixth tropical or subtropical storm of the 2005 Atlantic hurricane season. It represents an unusual meteorological phenomenon for that region, and its impacts were underestimated by the different operational meteorological forecasts during the previous days of the arrival of the low near Canary Islands. The aim of this study is to reproduce the local effects of the flow that were observed over the Canary Islands during the travel of the Delta storm near the region using high-resolution mesoscale meteorological simulations. The Advanced Research Weather Research & Forecasting Model (WRF-ARW) is applied at 9, 3 and 1 km horizontal resolution using ECMWF forecasts as initial and boundary conditions. The high-resolution simulation will outline the main features that contributed to the high wind speeds observed in the archipelago. Variations in vertical static stability, vertical windshear and the intense synoptic winds of the southwestern part of Delta with a warm core at 850 hPa were the main characteristics that contributed to the development and amplification of intense gravity waves while the large-scale flow interacted with the complex topography of the islands.

scholarly journals A Bow-Echo and Severe Weather Observed Over Poland on 11th and 12th August, 2017

2018 ◽  
Vol 215 (4) ◽  
pp. 157-168
Author(s):  
Czesław Dyrcz
Keyword(s):  
Weather Conditions ◽  
Severe Weather ◽  
Naval Academy ◽  
Training Centre ◽  
Weather Phenomenon ◽  
Significant Damage ◽  
Bow Echo ◽  
Significant Area ◽  
History Of ◽  
The Village

Abstract The paper presents results of research based on analysis of weather conditions during the storm front on 11th and 12th August, 2017, which has been relocated through a significant area of Poland. The front with an unprecedented force struck the infrastructure of the Academic Training Centre in the village of Czernica (ATC Czernica) on 11th August, 2017 about 23:05 CET. Due to wind impact of near-hurricane force, significant damage in the facility’s infrastructure and the biggest losses are incurred in forest resources. The data from the front passage through Gdynia was observed on a mobile meteorological station located at the Naval Academy in Gdynia. Describing the phenomenon and displaying the losses caused is one of the historical goals set before the article, because such a rapid weather phenomenon has not been recorded in the more than 50-years history of the Center in Czernica.

scholarly journals Modelling winter storm impacts on insured claim ratios of residential buildings in German administrative districts

2021 ◽  
Author(s):  
Andreas Trojand ◽  
Nico Becker ◽  
Henning Rust
Keyword(s):  
Urban Areas ◽  
Linear Models ◽  
Mean Squared Error ◽  
Residential Buildings ◽  
Daily Maximum ◽  
Wind Gust ◽  
Loss Ratio ◽  
Winter Storms ◽  
Wind Speeds ◽  
Link Functions

<p>Severe winter storms are one of the most damaging natural hazards for European residential buildings. Previous studies mainly focused on the loss ratio (loss value / total insured sum) as a monetary value for damages. In this study the focus is on the claim ratio (number of claims / number of contracts), which is derived from a storm loss dataset provided by the German Insurance Association. Due to its magnitude, the claim ratio might be a more intuitive parameter for the use in impact-based warnings than the loss ratio.</p><p>In a first step, loss ratios and claim ratios in German administrative districts are compared to investigate differences and similarities between the two variables. While there is no significant change in the ratio between claim ratio and loss ratio with increasing wind speeds, a tendency for lower loss ratios in urban areas can be confirmed.</p><p>In a second step, a generalized linear model for daily claim ratios is developed using daily maximum wind gust (ERA5) and different non-meteorological indicators for vulnerability and exposure as predictor variables. The non-meteorological predictors are derived from the Census 2011. They include information about the district-average construction years, the number of apartments per buildings and others to get a better understanding of these factors concerning the number of buildings affected by windstorms. The modelling procedure is divided into two steps. First, a logistic regression model is used to model the probabilty claim ratios larger than zero. Second, generalized linear models with different link functions are compared regarding their ability to predict claim ratios larger than zero. In a cross-validation setting a criteria for model selection is implemented and the models of both steps are verified. Both steps show an improvement over the climatological forecast and in both cases the addition of data for vulnerability and exposure leads to in decrease of the mean squared error. </p>

Risk Assessment of Road Vehicles Under Wind Gust Excitation

2020 ◽  
Vol 15 (10) ◽  
Author(s):  
Xiaoyu Zhang ◽  
Carsten Proppe
Keyword(s):  
Risk Assessment ◽  
Risk Analysis ◽  
Warning System ◽  
Practical Method ◽  
Large Contribution ◽  
Wind Gust ◽  
Road Vehicles ◽  
Wind Speeds ◽  
The Past ◽  
Crosswind Stability

Abstract Crosswind stability of vehicles has attracted a lot of attention in the past years. Accidents caused by strong crosswind occupy a relatively small proportion. However, they may have unproportionally large contribution to serious and fatal injuries. In order to assess the crosswind stability of road vehicles in a more realistic way, risk analysis for road vehicles running under realistic wind excitation has to be considered. This paper summarizes the method for risk analysis of crosswind stability of road vehicles. A nonstationary model for the wind forces and moments acting on a running vehicle is presented and analyzed in detail. In addition, guidelines for speed limitations or traffic restrictions are developed. Based on the risk analysis, a practical method to determine the critical mean wind speeds for a wind warning system is proposed.

scholarly journals Prediction of Near-Surface Variables at Independent Locations from a Bias-Corrected Ensemble Forecasting System

2006 ◽  
Vol 134 (11) ◽  
pp. 3415-3424 ◽  
Author(s):  
Nusrat Yussouf ◽  
David J. Stensrud
Keyword(s):  
New England ◽  
Near Surface ◽  
Wind Speeds ◽  
Dewpoint Temperature ◽  
Model Domain ◽  
Oklahoma Mesonet ◽  
Independent Observations ◽  
Forecasting System ◽  
Surface Station ◽  
Forecast Time

Abstract The ability of a multimodel short-range bias-corrected ensemble (BCE) forecasting system, created as part of NOAA’s New England High Resolution Temperature Program during the summer of 2004, to obtain accurate predictions of near-surface variables at independent locations within the model domain is explored. The original BCE approach produces bias-corrected forecasts only at National Weather Service (NWS) observing surface station locations. To extend this approach to obtain bias-corrected forecasts at any given location, an extended BCE technique is developed and applied to the independent observations provided by the Oklahoma Mesonet. First, a Cressman weighting scheme is used to interpolate the bias values of 2-m temperature, 2-m dewpoint temperature, and 10-m wind speeds calculated from the original BCE approach at the NWS observation station locations to the Oklahoma Mesonet locations. These bias values are then added to the raw numerical model forecasts bilinearly interpolated to this same specified location. This process is done for each forecast member within the ensemble and at each forecast time. It is found that the performance of the extended BCE is very competitive with the original BCE approach across the state of Oklahoma. Therefore, a simple postprocessing scheme like the extended BCE system can be used as part of an operational forecasting system to provide reasonably accurate predictions of near-surface variables at any location within the model domain.

scholarly journals Disdrometer, Polarimetric Radar, and Condensation Nuclei Observations of Supercell and Multicell Storms on 11 June 2018 in Eastern Nebraska

Atmosphere ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 770
Author(s):  
Matthew Van Den Broeke
Keyword(s):  
Particle Concentration ◽  
Rain Rate ◽  
Radar Data ◽  
Convective Cell ◽  
Observation Time ◽  
Precipitation Intensity ◽  
Polarimetric Radar ◽  
Condensation Nuclei ◽  
Supercell Storm ◽  
Differential Reflectivity

Disdrometer and condensation nuclei (CN) data are compared with operational polarimetric radar data for one multicell and one supercell storm in eastern Nebraska on 11 June 2018. The radar was located ~14.3 km from the instrumentation location and provided excellent observation time series with new low-level samples every 1–2 min. Reflectivity derived by the disdrometer and radar compared well, especially in regions with high number concentration of drops and reflectivity <45 dBZ. Differential reflectivity also compared well between the datasets, though it was most similar in the supercell storm. Rain rate calculated by the disdrometer closely matched values estimated by the radar when reflectivity and differential reflectivity were used to produce the estimate. Concentration of CN generally followed precipitation intensity for the leading convective cell, with evidence for higher particle concentration on the edges of the convective cell associated with outflow. The distribution of CN in the supercell was more complex and generally did not follow precipitation intensity.

Boulevard Tree Failures During Wind Loading Events

2019 ◽  
Vol 45 (6) ◽  
Author(s):  
Gary Johnson ◽  
Chad Giblin ◽  
Ryan Murphy ◽  
Eric North ◽  
Aaron Rendahl
Keyword(s):  
Urban Trees ◽  
Wind Loading ◽  
Wind Speeds ◽  
Site Characteristics ◽  
Significant Damage ◽  
Large Trees ◽  
Degree Of Damage ◽  
Structural Failures ◽  
Potential Damage

Wind loading events vary in their intensity and degree of damage inflicted on urban infrastructure, both green and gray. Damage to urban trees can begin with wind speeds as low as 25 miles per hour, especially when those trees harbor defects that predispose them to structural failures. The tree damage triangle integrates the three main factors that influence tree failures during wind loading events, namely the site characteristics, the (wind) loading event and any defects of the trees in question. The degree of damage that trees experience is generally a function of these factors overlapping each other. For instance, when the potential damage from wind loading events is exacerbated by poor tree architecture and compromised site conditions, the likelihood of significant damage is realized. Two studies on the damage to urban trees and the predictability of damage are reviewed; one study is a longterm gathering of wind loading events and accompanying damage to trees while the other is a case study of one storm in one city on one day. Both studies revealed critical pre-existing conditions that left trees vulnerable to whole tree losses: large trees in limited boulevard widths and severed roots as a result of sidewalk repair.

Sign in / Sign up

Export Citation Format

Share Document