Weather Terms and Definitions


Introduction

This glossary contains weather-related terms that may be either heard or used by severe local storm spotters or spotter groups. Its purposes are 1) to achieve some level of standardization in the definitions of the terms that are used, and 2) provide a reference from which the meanings of any terms, especially the lesser-used ones, can be found. The idea is to allow smooth and effective communication between storm spotters and forecasters, and vice versa. This is an important necessity within the severe weather warning program. Despite advances in warning and forecasting techniques (e.g., Doppler radar), the human eye will always be a vital part of any effective warning system. Storm spotters are, and always will be, an indispensable part of the severe local storm warning program.

A complete list of terms probably is impossible to arrive at, but this list is as comprehensive as possible. Certainly it is not necessary for every spotter to know the meaning of every term contained herein. In this sense, the glossary serves as a reference. In fact, many of the terms may never be heard at all; they are included here just in case, someday, they are. (By the way, inclusion of a term in this glossary does not give license to use it freely in radio or phone communication. Use of technical terms should be kept to a minimum). But there are some terms for which the meanings are both important and specific. The important ones are preceded by asterisks; all spotters should be familiar with the definitions of these terms before taking an active role in any spotter group.

The definitions have been written in what hopefully passes as "layman's terms." They are written to be easily understood by the storm spotter, regardless of his or her meteorological background. At times technical purity has been sacrificed for simplicity, and the result may prompt a few moans from the technical purists. So be it; this glossary wasn't written for them. Many of the terms are so closely interrelated, though, that it becomes necessary to "cross-reference;" that is, to use one or more terms in the definition of another. In this glossary, all terms that are hyperlinked within a definition are terms that are defined themselves elsewhere.

The glossary is a culmination of an effort which began in the spring of 1991. Many individuals with considerable experience in severe storm research and storm spotting (or chasing) contributed to the glossary. Because of the many comments offered by these individuals, there was disagreement on the descriptions of some terms. Those terms that were identified as such as being somewhat more controversial are handled in the text by inclusion of a second paragraph in the description, which discusses any cautions or controversy regarding the use of the term.

One last word: Storm spotting is vital, but also can be very dangerous. No one should attempt storm spotting without first obtaining the proper training! This glossary in itself is not to be considered sufficient training material to qualify oneself as a spotter. Further training, usually provided by the National Weather Service, must be obtained through local agencies (usually Emergency Management) before one can be certified as a storm spotter. There is also something to be said for the so-called storm chasers, who chase storms mainly for the thrill of it (and as such are not spotters). Chasers of all levels of background and experience will no doubt find this glossary useful or at least interesting. But while their enthusiasm is commended, it must emphasize that the glossary does not condone storm chasing as a leisure activity - especially for the unprepared. Proper training and foreknowledge of the dangers are required of everyone who meets face to face with severe thunderstorms - regardless of the reason for the encounter.

Michael L. Branick
National Weather Service, Experimental Forecast Facility
Norman, Oklahoma
June 1992


Introduction to the Second Edition

Based on feedback since its introduction, the "Spotter Glossary" (as this glossary has come to be known) has achieved considerable popularity among spotters - at least in the southern Plains region of "Tornado Alley." In this region, spotters actively seek as much information as possible when assessing severe weather potential on a given day. The information available often includes products which contain technical terms which are more esoteric to operational meteorology, and less familiar to those who do not pursue meteorology as a living. Examples include forecast discussions issued by local National Weather Service offices, and convective outlooks and discussions issued by the Storm Prediction Center (SPC, formerly known as SELS/NSSFC).

The question arises as to just how far one should go into the technical realm of operational meteorology when compiling a glossary like this for storm spotters. The dilemma is thus: The spotters' thirst for knowledge is admirable, but how much of the technical jargon really needs to be understood by spotters in the field?

The glossary is certainly not a meteorological textbook for spotters (or anyone else). That is not its purpose. Spotters have a vital role in the warning program, as do forecasters. And while interaction between them is an absolute necessity, one must be careful not to allow the two functions to overlap so much that we end up with spotters routinely generating their own forecasts and disregarding those made by the forecasters. That is not the spotter's function; spotting is.

On the other hand, the spotters who demonstrate a genuine interest in understanding the atmosphere that they are trained to observe are applauded. If they are interested in understanding what the forecaster is talking about when he/she refers to, say, "Isentropic Lift" or a "Right-Rear Quad Of An Upper Jet Max", then they should have a place to find at least a general description of the unfamiliar terms. This is preferable to saying, "you don't need to know that." And those who are "turned off" by the technical jargon need not look into it further.

Attempts have been made to "strike a happy medium" by adding a number of meteorological terms and phrases to this edition, accompanied by general definitions. New terms to this addition, many of which were added at the suggestion of spotters, are listed below. They at least should help the spotter to understand a little more about why a particular feature is important to severe weather forecasting. Those who wish to pursue a particular issue beyond what is covered in this glossary are directed to the local library or the nearest university meteorology department.

Note that a similar dilemma arose in the first edition, regarding the inclusion of "slang" terms that are used most often by storm chasers. Again there is a distingtion between chasers and spotters - the former tending to observe storms for their own gratification, the latter tending to do so more for the needs of the community. The "slang" dilemma continues, but as with the first edition many slang terms have been included that are consider appropriate for spotter use. That means that terms like "Caprock Delight" (which may be anything but a delight to residents in the path of one) will not be found herein, but that slang terms that are more-or-less universally accepted, such as "Bear'S Cage" or "Anvil Crawlers" probably will appear.

Finally, modernization of the National Weather Service requires a few updates. NMC now is NCEP; SELS now is SPC. The Eta and RUC models are now here. And NEXRAD is no longer the NEXt-generation weather RADar, but is here now. The latest changes have been incorporated accordingly into the glossary.

Mike Branick
September 1996


Terms added for the second edition:



Acknowledgements

The author expresses his most sincere thanks to the many individuals who provided input to the glossary. The following individuals were instrumental in contributing, through helpful comments and suggestions: David Andra, Dave Beusterien, Dr. Harold Brooks, Bill Bunting, Don Burgess, E. Brian Curran, Dr. Charles A. Doswell III, Mike Emlaw, Mike Foster, Dave Gold, Paul Janish, Tim Marshall, Alan Moller, Mike Morgan, Steve Parker, Steve Piltz, Robert Prentice, Jim Purpura, Gene Rhoden, Lans Rothfusz, Dan Smith, Greg Stumpf, Steve Vasiloff. Steve Nelson and Doug Speheger both were instrumental in setting up the glossary on the WSFO Norman home page.


Bibliography

  • American Meteorology Society, 1990: Glossary of Meteorology. American Meteorological Society Press, Boston.
  • Caracena, Fernando, Ronald L. Holle, and Charles A. Doswell III, 1989: Microbursts - A Handbook for Visual Identification. NOAA, Environmental Research Laboratories, National Severe Storms Laboratory.
  • Doswell, Charles A. III, 1982: The Operational Meteorology of Convective Weather. Volume I: Operational Mesoanalysis. NOAA Technical Memorandum NWS NSSFC-5.
  • Doswell, Charles A. III, 1985: The Operational Meteorology of Convective Weather. Volume II: Storm Scale Analysis. NOAA Technical Memorandum ERL ESG-15.
  • Fujita, T. T., 1985: The Downburst - Microburst and Macroburst. SMRP Research Paper No. 210, University of Chicago, 122 pp.
  • Marshall, Tim, 19--: Storm Chase Manual. Published annually in association with Storm Track. Contact: 1336 Brazos Blvd, Lewisville TX 75067.
  • Marshall, Tim (Editor): Storm Track. Published bi-monthly by Master Graphics, Lewisville TX. Contact the editor, 1336 Brazos Blvd, Lewisville TX 75067, for subscription information.
  • National Weather Service, 1982: Spotter's Guide for Identifying and Reporting Severe Local Storms. Available from most National Weather Service offices, or from the U. S. Dept. of Commerce, NOAA, Rockville MD 20852.

Figures




Figure 1, Bow Echo


Figure 2, Weak Echo Region, Bounded Weak Eco Region


Figure 3, High-Precipitation Supercell Thunderstorm


Figure 4, Line Echo Wave Pattern


Figure 5, Low-Precipitation Supercell Thunderstorm


Figure 6, Sounding


Figure 7, Classic Supercell Thunderstorm





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