Tornadic thunderstorms are the most intense and most damaging type of convective storm. Whereas ordinary convective cells grow, produce rain, and then decay over a period of 40 rain to an hour, certain thunderstorms may develop into a nearly steady-state structure that persists for several hours, producing heavy rain, large hail, damaging surface winds, and tornadoes. Although tornadoes may arise in a variety of storm conditions, these long-lived storms produce tornadoes most frequently and generate virtually all of the most damaging ones. Prominent features of these tornadic thunderstorms, which are particularly common i the Great Plains and midwestern regions of the United States, are illustrated in an idealized schematic in Figure 1. Our understanding of tornadic storms has evolved gradually over the years as technological advances have been made in observing systems and computer models. The first indications that certain storms exhibit a special behavior came from early studies of data from upper-air soundings and surface stations. While most thunderstorms moved with the mean winds over the lower and middle troposphere (Byers & Braham 1949), certain large storms were found to propagate consistently to the right of the mean winds (Byers 1942, Newton & Katz 1958). Observing the shift in the wind direction as storms passed by surface stations, Byers (1942) and later Brooks (1949) surmised that these intense storms have cyclonic ci rculation (counterclockwise rotation about a vertical axis, viewed from above). Using data from scanning radar and ground observations, case studies of a severe thunderstorm near Wokingham, England (Browning Ludlam 1962), and another near Geary, Oklahoma (Browning & Donaldson 1963), revealed numerous distinctive features that were strikingly

Dynamics of tornadic thunderstorms

We explore the impact of different resolutions, convective closures, and microphysical parameterizations on the representation of precipitation statistics (climatology, seasonal cycle, and intense events) in 20-yr-long simulations over Europe with the regional climate Weather Research and Forecasting (WRF) Model. The simulations are forced in the period 1979–98, using as boundary conditions the ERA-Interim fields over the European region. Special attention is paid to the representation of precipitation in the Alpine area. We consider spatial resolutions ranging from 0.11° to 0.037°, allowing for an explicit representation of convection at the highest resolution. Our results show that while there is a good overall agreement between observed and modeled precipitation patterns, the model outputs display a positive precipitation bias, particularly in winter. The choice of the microphysics scheme is shown to significantly affect the statistics of intense events. High resolution and explicitly resolved ...

Sensitivity of Precipitation Statistics to Resolution, Microphysics, and Convective Parameterization: A Case Study with the High-Resolution WRF Climate Model over Europe

Radar has been used by meteorologists for 30 years or so but it is only during the latter half of this period that the full measure of its versatility has come to be recognised. Operationally important techniques have been or are being developed to identify and track severe storms, to provide warning of tornadoes, to measure and forecast rainfall quantitatively, and to measure winds, turbulence and wind shear. At the same time research meteorologists are using specialised radar techniques to investigate many poorly understood aspects of atmospheric behaviour. This review highlights the strengths and limitations of radar as a tool for observing the atmosphere and attempts to provide a balanced view of its many applications in meteorology.

https://iopscience.iop.org/article/10.1088/0034-4885/41/5/003/pdf

Meteorological applications of radar

Effects of Cumulus Convection on the vorticity Field in the Tropics

For what may seem to be a narrow specialization of atmospheric science, radar meteorology has a surprisingly rich literature. Papers including radar observations have appeared regularly in journals of the American Meteorological Society (AMS) for the past 50 years. Radar meteorology conferences are the oldest series of technical conferences of the AMS and have the longest series of conference proceedings. Critical reviews in the formative years and later (Ligda 1951; Wexler 1951; Marshall et al. 1955; Marshall and Gordon 1957; Atlas 1964) served periodically to bring the subject up to date. The widely used textbooks of Louis J. “Lou” Battan (1959, 1973) did much to delineate the field and to establish radar meteorology as a valid discipline. The text of Doviak and Zrnic, now in its second edition (1993), provides a modern synthesis. Other books on the subject are those of Gossard and Strauch (1983), with its focus on clear-air echoes, and of Rinehart (1991), intended for undergraduate students or operational meteorologists. But it was the publication in 1990 of the monumental Radar in Meteorology, conceived as a tribute to Lou Battan by David Atlas and edited by him, that makes it easy to argue that no part of atmospheric science has been better served. And even the history of the subject is available for the reading—the sparkling account of Walter Hitschfeld (1986) and the first 18 chapters (150 pages) of Radar in Meteorology. What accounts for the extraordinary attention paid to radar in meteorology? And, perhaps more to the point, what can we hope to say in this short review that has not already been said?

A Short History of Radar Meteorology

The dual-Doppler radar coplane method of scanning and data reduction has been used to determine the internal airflow and radar reflectivity structure of a convective storm. Cumulus convection growing in a moderately sheared wind environment resulted in a nonsteady, moderate intensity thunderstorm. Precipitation fallout and downward moving air are found downshear of an updraft inclined in the downshear direction. Rapid storm translation, vertical shear of the ambient wind, and slow subcloud ascent of inflow air act to establish this observed draft configuration. The absence of significant cold air outflow and its attendant gust front at the surface is attributed to (i) appreciable inflow of slow moving air into the downdraft at the middle layers and (ii) the fact that the potentially coldest air was located too low to contribute significantly to a deep downdraft circulation.

L. J. Miller

Papers

Internal Airflow of a Convective Storm from Dual-Doppler Radar Measurements