scholarly journals Supercells in Environments with Atypical Hodographs

2011 ◽  
Vol 26 (6) ◽  
pp. 1075-1083 ◽  
Author(s):  
David O. Blanchard
Keyword(s):  
Situational Awareness ◽  
Warm Season ◽  
Severe Weather ◽  
North American Monsoon ◽  
Correct Interpretation ◽  
Weather Event ◽  
Northern Arizona ◽  
Upper Level ◽  
Cold Core ◽  
Severe Weather Event

Abstract An unusual severe weather event with supercell thunderstorms developed across portions of northern Arizona in the midst of the warm-season North American monsoon—a regime characteristically dominated by a subtropical upper-level high over the southwestern United States. The approach of a midlatitude, cold-core, upper-level low brought an environment of enhanced shear and increased instability supportive of supercells. This atypical system is described and how a correct interpretation of the winds and hodograph would allow a forecaster to maintain situational awareness is discussed.

scholarly journals Objective Climatological Analysis of Extreme Weather Events in Arizona during the North American Monsoon

2016 ◽  
Vol 55 (11) ◽  
pp. 2431-2450 ◽  
Author(s):  
Jeremy J. Mazon ◽  
Christopher L. Castro ◽  
David K. Adams ◽  
Hsin-I Chang ◽  
Carlos M. Carrillo ◽  
...  
Keyword(s):  
Extreme Events ◽  
Extreme Weather ◽  
Severe Weather ◽  
North American Monsoon ◽  
Type I ◽  
Type Ii ◽  
Weather Event ◽  
The North ◽  
Weather Events ◽  
Severe Weather Event

AbstractAlmost one-half of the annual precipitation in the southwestern United States occurs during the North American monsoon (NAM). Given favorable synoptic-scale conditions, organized monsoon thunderstorms may affect relatively large geographic areas. Through an objective analysis of atmospheric reanalysis and observational data, the dominant synoptic patterns associated with NAM extreme events are determined for the period from 1993 to 2010. Thermodynamically favorable extreme-weather-event days are selected on the basis of atmospheric instability and precipitable water vapor from Tucson, Arizona, rawinsonde data. The atmospheric circulation patterns at 500 hPa associated with the extreme events are objectively characterized using principal component analysis. The first two dominant modes of 500-hPa geopotential-height anomalies of the severe-weather-event days correspond to type-I and type-II severe-weather-event patterns previously subjectively identified by Maddox et al. These patterns reflect a positioning of the monsoon ridge to the north and east or north and west, respectively, from its position in the “Four Corners” region during the period of the climatological maximum of monsoon precipitation from mid-July to mid-August. An hourly radar–gauge precipitation product shows evidence of organized, westward-propagating convection in Arizona during the type-I and type-II severe weather events. This new methodological approach for objectively identifying severe weather events may be easily adapted to inform operational forecasting or analysis of gridded climate data.

scholarly journals Characterizing severe weather potential in synoptically weakly forced thunderstorm environments

2017 ◽  
Author(s):  
Paul W. Miller ◽  
Thomas L. Mote
Keyword(s):  
United States ◽  
High Resolution ◽  
Numerical Model ◽  
Model Error ◽  
Severe Weather ◽  
Forecasting Model ◽  
Weather Event ◽  
Southeast United States ◽  
Accurate Representation ◽  
Severe Weather Event

Abstract. Weakly forced thunderstorms (WFTs), short-lived convection forming in synoptically quiescent regimes, are a contemporary forecasting challenge. The convective environments that support severe WFTs are often similar to those that yield only nonsevere WFTs, and additionally, only a small proportion individual WFTs will ultimately produce severe weather. The purpose of this study is to better characterize the relative severe weather potential in these settings as a function of the convective environment. Thirty near-storm convective parameters for > 200 000 WFTs in the Southeast United States are calculated from a high-resolution numerical forecasting model, the Rapid Refresh (RAP). For each parameter, the relative likelihood of WFT days with at least one severe weather event is assessed along a moving threshold. Parameters (and the values of them) that reliably separate severe-weather-supporting from nonsevere WFT days are highlighted. Only two convective parameters, vertical totals (VT) and total totals (TT), appreciably differentiate severe-wind-supporting and severe-hail-supporting days from nonsevere WFT days. When VTs exceeded values between 24.6–25.1 °C or TTs between 46.5–47.3 °C, severe-wind days were roughly 5 × more likely. Meanwhile, severe-hail days became roughly 10 × more likely when VTs exceeded 24.4–26.0 °C or TTs exceeded 46.3–49.2 °C. The stronger performance of VT and TT is partly attributed to the more accurate representation of these parameters in the numerical model. Under-reporting of severe weather and model error are posited to exacerbate the forecasting challenge by obscuring the subtle convective environmental differences enhancing storm severity.

scholarly journals The Advantages of a Mixed-Band Radar Network for Severe Weather Operations: A Case Study of 13 May 2009

2014 ◽  
Vol 29 (1) ◽  
pp. 78-98 ◽  
Author(s):  
Vivek N. Mahale ◽  
Jerald A. Brotzge ◽  
Howard B. Bluestein
Keyword(s):  
Situational Awareness ◽  
Severe Weather ◽  
Combined System ◽  
Low Level ◽  
Dynamic Events ◽  
Temporal Sampling ◽  
Radar Network ◽  
Upper Level ◽  
Using Data

Abstract Adding a mix of X- or C-band radars to the current Weather Surveillance Radar-1988 Doppler (WSR-88D) network could address several limitations of the network, including improvements to spatial gaps in low-level coverage and temporal sampling of volume scans. These limitations can result in missing critical information in highly dynamic events, such as tornadoes and severe straight-line wind episodes. To evaluate the potential value of a mixed-band radar network for severe weather operations, a case study is examined using data from X- and S-band radars. On 13 May 2009, a thunderstorm complex associated with a cold front moved southward into southwest Oklahoma. A tornado rapidly developed from an embedded supercell within the complex. The life cycle of the tornado and subsequent wind event was sampled by the experimental Collaborative Adaptive Sensing of the Atmosphere (CASA) radar testbed of four X-band radars as well as two operational WSR-88Ds. In this study, the advantages of a mixed-band radar network are demonstrated through a chronological analysis of the event. The two radar networks provided enhanced overall situational awareness. Data from the WSR-88Ds provided 1) clear-air sensitivity, 2) a broad overview of the storm complex, 3) a large maximum unambiguous range, and 4) upper-level scans up to 19.5°. Data from the CASA radars provided 1) high-temporal, 1-min updates; 2) overlapping coverage for dual-Doppler analysis; and 3) dense low-level coverage. The combined system allowed for detailed, dual- and single-Doppler observations of a wind surge, a mesocyclone contraction, and a downburst.

A warm-front triggered nocturnal tornado outbreak near Kiama, NSW, Australia

2018 ◽  
Vol 68 (1) ◽  
pp. 147
Author(s):  
Simon A. Louis
Keyword(s):  
New South ◽  
Severe Weather ◽  
South Coast ◽  
Horizontal Shear ◽  
Weather Event ◽  
Pressure System ◽  
Warm Front ◽  
South Wales ◽  
Low Pressure System ◽  
Severe Weather Event

This paper documents the case of a nocturnal outbreak of tornadoes on the New South Wales (NSW) south coast on 23 February 2013, and provides an analysis of the conditions that led to the outbreak. These tornadoes were associated with the passage of a warm front which had developed on the eastern flank of a mature extratropical cyclone.The damage from the tornadoes is discussed, and an analysis of the synoptic and mesoscale conditions that led to the event is provided. An analysis of radar at the time of the event shows a series of vortices developing within a zone of horizontal shear just prior to the tornadoes developing. The tornadoes were difficult for operational forecasters to predict, partly due to the infrequent occurrence of nocturnal tornadoes of this type in NSW, and in part due to operational demands from the broader scale severe weather event that resulted from the low-pressure system. This paper presents an analysis of the event that may assist forecasters in identifying similar events in the future.

Analysis of the Algerian severe weather event in November 2001 and its impact on ozone and nitrogen dioxide distributions

Tellus B ◽  
2011 ◽  
Vol 55 (5) ◽  
pp. 993-1006
Author(s):  
W. Thomas ◽  
F. Baier ◽  
T. Erbertseder ◽  
M. Kaästner
Keyword(s):  
Nitrogen Dioxide ◽  
Severe Weather ◽  
Weather Event ◽  
Severe Weather Event

scholarly journals A high-resolution modelling case study of a severe weather event over New Zealand

2008 ◽  
Vol 9 (3) ◽  
pp. 119-128 ◽  
Author(s):  
Stuart Webster ◽  
Michael Uddstrom ◽  
Hilary Oliver ◽  
Simon Vosper
Keyword(s):  
New Zealand ◽  
High Resolution ◽  
Severe Weather ◽  
Weather Event ◽  
Severe Weather Event

Identification of Severe Weather Event with 3D meteorological radar and MLP

2017 ◽  
Author(s):  
Tulipa Gabriela Guilhermina Juvenal da Silva ◽  
Paulo Henrique Siqueira ◽  
Cesar Beneti ◽  
Maiko Buzzi ◽  
Leonardo Calvetti
Keyword(s):  
Severe Weather ◽  
Weather Event ◽  
Meteorological Radar ◽  
Severe Weather Event

A comparison between 4D-VAR and cycling 3D-VAR methods for the simulation of a severe weather event in Central Italy. Preliminary results.

2020 ◽  
Author(s):  
Vincenzo Mazzarella ◽  
Rossella Ferretti
Keyword(s):  
Positive Impact ◽  
Central Italy ◽  
Wrf Model ◽  
Severe Weather ◽  
Precipitation Forecast ◽  
Mountain Range ◽  
Weather Event ◽  
Maximum Rainfall ◽  
The Impact ◽  
Severe Weather Event

<p>Nowadays, the use of 4D-VAR assimilation technique has been investigated in several scientific papers with the aim of improving the localization and timing of precipitation in complex orography regions. The results show the positive impact in rainfall forecast but, the need to resolve the tangent linear and adjoint model makes the 4D-VAR computationally too expensive. Hence, it is used in operationally only in large forecast centres. To the aim of exploring a more reasonable method, a comparison between a cycling 3D-VAR, that needs less computational resources, and 4D-VAR techniques is performed for a severe weather event occurred in Central Italy. A cut-off low (992 hPa), located in western side of Sicily region, was associated with a strong south-easterly flow over Central Adriatic region, which supplied a large amount of warm and moist air. This mesoscale configuration, coupled with the Apennines mountain range that further increased the air column instability, produced heavy rainfall in Abruzzo region (Central Italy).</p><p>The numerical simulations are carried out using the Weather Research and Forecasting (WRF) model. In-situ surface and upper-air observations are assimilated in combination with radar reflectivity and radial velocity data over a high-resolution domain. Several experiments have been performed in order to evaluate the impact of 4D-VAR and cycling 3D-VAR in the precipitation forecast. In addition, a statistical analysis has been carried out to objectively compare the simulations. Two different verification approaches are used: Receiver Operating Characteristic (ROC) curve and Fraction Skill Score (FSS). Both statistical scores are calculated for different threshold values in the study area and in the sub-regions where the maximum rainfall occurred.</p>

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