& SpringerWienNewYork

& SpringerWienNewYork

CISM COURSES AND LECTURES Series Editors: The Rectors Giulio Maier - Milan Jean Salen9on - Palaiseau Wilhelm Schneider - Wien The Secretary General Bemhard Schrefler - Padua Executive Editor Paolo Serafini - Udine The series presents lecture notes, monographs, edited works and proceedings in thefieldof Mechanics, Engineering, Computer Science and Applied Mathematics. Purpose of the series is to make known in the international scientific and technical community results obtained in some of the activities organized by CISM, the International Centre for Mechanical Sciences.

INTERNATIONAL CENTRE FOR MECHANICAL SCIENCES COURSES AND LECTURES - No. 475 ATMOSPHERIC CONVECTION: RESEARCH AND OPERATIONAL FORECASTING ASPECTS EDITED BY DARIO B. GIAIOTTI ARPA FVG OSMER, UDINE, ITALY REINHOLD STEINACKER UNIVERSITY OF VIENNA, AUSTRIA FULVIO STEL ARPA FVG OSMER, UDINE, ITALY SpringerWien NewYork

This volume contains 121 illustrations This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned specifically those of translation, reprinting, re-use of illustrations, broadcasting, reproduction by photocopying machine or similar means, and storage in data banks. 2007 by CISM, Udine Printed in Italy SPIN 11922483 All contributions have been typeset by the authors. ISBN-10 3-211-48963-0 SpringerWienNewYork ISBN-13 978-3-211-48963-5 SpringerWienNewYork

PREFACE The troposphere is the subtle skin of gases and vapors surrounding our planet which hosts almost all the human activities and weather phenomena. Its name comes from the ceaseless vertical mixing it experiences. The mechanism responsible for the continuous tropospheric vertical mixing is the convection. Even if the physical laws describing convection are quite well known, nevertheless our ability in understanding and forecasting convective weather phenomena is, in some cases, quite poor. The reason for that, depends on our limits in the capability of solving the Navier-Stokes equations, applied to the troposphere, and fully monitoring the actual tropospheric state. These limits are dramatically evident in areas characterized by complex orography and geography, where our knowledge of initial conditions is extremely fragmented and the constraints imposed by the boundaries make the Navier-Stokes equations even more sensitive from those initial conditions. Because of these reasons, when facing aspects related to atmospheric convection, one should reflect on the metaphor by Aldous Huxley, who imagined the relationship between Mankind and Nature as a game of chess where both players know very well the rules, but only Nature never fails neither cheats nor bluffs and the best result Mankind can obtain is a tie. Keeping this in mind, this book is meant to be a collection of information and conceptual models (the rules of the game) on deep-moist atmospheric convection, its related weather phenomena, and it presents several useful tools and techniques (the strategy of the game) not only for the prognostic activities, but even for the forecasts verification, which is fundamental to learn from our mistakes and to develop new techniques. Last but not least, by this book the authors would like to remind to the readers that if the understanding of the atmospheric convection is considered a game, as such, they should enjoy themselves carrying out this difficult, but fascinating and important activity. In this book the readers are lead along a path that starts with the basics of the atmospheric convection, in particular the dynamics and thermodynamics of unstable moist air. Then the initiation of the spontaneous vertical motions is considered and the weather phenomena related to deep-moist convection are presented. A significant part of the book is devoted to the boundary conditions of convective weather and in particular the role played by orography is examined in detail. The environments hosting convective severe weather are discussed considering their thermic, moisture and wind vorticity fields features, both from theoretical and experimental point of view. The last part of the book is focused on the specific problem of the convective severe weather forecasts and to the evaluation of their quality.

The book is addressed to meteorologists^ physicists and weather forecasters^ in particular to those interested in improving their knowledge of convection-related weather phenomena. Furthermore the book is considered as a valuable support for the PhD students attending courses on environmental fluid dynamics and meteorology. Each chapter is almost self consistent and there are no propaedeutic parts that the reader should consider necessary before to deal with more advanced ones. Anyway the proposed chapter sequence follows a scheme that the editors consider suitable for the didactics of the topic. The realization of the book owes much to the scientists who shared with us the CISM course from which it springs from. Special thanks are addressed to the Rectors and the Scientific Editor of CISM who gave the opportunity to organize the course since the beginning; in particular Prof. Manuel Velarde who stimulated us and supported our work throughout its development. Furthermore we are indebted with CISM personnel who helped in preparing the proofs of the book; special thanks to dr. Monica Del Pin who kindly an patiently worked with us. Dario B. Giaiotti Reinhold Steinacker Fulvio Stel

CONTENTS An Overview of Atmospheric Convection P. Markowski 1 The Concept of Buoyancy and Its Application to Deep Moist Convection P, Markowski... 7 Pressure Fluctuations Associated with Deep Moist Convection P. Markowski 17 Convective Storm Initiation and Organization P. Markowski 23 Supercell Thunderstorms P. Markowski 29 Tornadoes and Tomadogenesis P. Markowski 45 Dynamical Aspects of Topography: the Role of Obstacles R. Steinacker 57 Thermodynamic Aspects of Topography: the Role of Elevation R. Steinacker 75 Topography: the Global Player in Meteorology R. Steinacker 101 Environmental Conditions Associated with Convective Phenomena: Proximity Soundings H.Brooks 113 Development and Use of Climatologies of Convective Weather H.Brooks 123 Ingredients-Based Forecasting H.Brooks 133

Practical Aspects of Forecasting Severe Convection in the United States: Environmental Conditions and Initiation H.Brooks 141 Practical Aspects of Forecasting Severe Convection in the United States: Storm Evolution and Warning H, Brooks 149 General Considerations on the Operational Forecasts of Severe Convective Events: from Medium to Short Range D, B. Giaiotti and K Stel 157 General Considerations on the Operational Forecasts of Severe Convective Events: from Short Range to Nowcasting D. B. Giaiotti and F. Stel 177 Weather Forecast Verication R Stel and D.B. Giaiotti 195