Search Results

You are looking at 1 - 9 of 9 items for

  • Author or Editor: Thomas R. Stewart x
  • Refine by Access: All Content x
Clear All Modify Search
Thomas R. Stewart

Abstract

Estimates of several components of forecasting skill can be obtained by combining a skill-score decomposition developed by Allan Murphy with techniques for decomposing correlation coefficients that have been employed in research on human judgment. The decomposition of the correlation coefficient requires knowledge of the information or “cues” used by the forecaster. When the cues are known, it is possible to estimate the effects of uncertainty and the forecaster's consistency and use of the cues.

Full access
Thomas R. Stewart
and
Patricia Reagan-Cirincione

Abstract

Skill-score decompositions can be used to analyze the effects of bias on forecasting skill. However, since bias terms are typically squared, and bias is measured in skill-score units rather than in units of the forecasts, such decompositions only partially describe the nature of the bias. They do not describe the direction of bias or measure the amount of correction required to remove bias. Simple “debiasing” coefficients can be derived to supplement the skill-score decomposition by indicating the direction and amount of bias, relative to unbiased forecasts. Calculation of these coefficients is described and an example is provided.

Full access
Thomas R. Stewart
,
Roger Pielke Jr.
, and
Radhika Nath

A case study of the impact of improved precipitation forecasts on the snow-fighting operations of the New York State Thruway is reported. The goal was to use currently available data and literature on forecast process, communication, and use in conjunction with observations and interviews with key decision makers to derive a model that yields estimates of value to users based on a model of their decision processes rather than an optimal decision-making model. That goal proved too ambitious due to limitations in available data. A major lesson learned from this research is the importance of improved, ongoing data collection to support studies of use and value of weather information. A more holistic approach to understanding and realizing forecast value is needed, that is, one in which information (both of forecast skill and usage) centered on the decision process is collected in a much more intensive manner than is presently the case.

Full access
Thomas R. Stewart
,
Richard W. Katz
, and
Allan H. Murphy

This paper reports some results of a descriptive study of the value of weather information used by fruit growers in the Yakima Valley of central Washington to decide when to protect their orchards against freezing temperatures. Specifically, the study provides data concerning the decision-making procedures of individual orchardists, the growers' use of weather information including frost (i.e., minimum temperature) forecasts, and the dimensions of the value of such forecasts.

Results from the descriptive study regarding the orchardists' information-processing and decision-making procedures are compared with the procedures included in a previous prescriptive study of the fruit-frost problem in the same geographical area (Katz et al., 1982). The prescriptive study employed a dynamic decision-making model and yielded estimates of the economic value of frost forecasts under the assumption (inter alia) that the orchardists' decisions were based solely on these forecasts. On the other hand, the descriptive study with which the current paper is primarily concerned indicates that growers use temperature and dew point observations available after the frost forecast has been issued, as well as the frost forecasts themselves, to make frost protection decisions. Furthermore, while the results of the descriptive study show that the grower makes a series of decisions to protect or not to protect during the night, the model assumed that an irreversible commitment is made early in the night. The results of an initial effort to modify the original prescriptive model in accordance with the descriptive findings to obtain more realistic estimates of the value of frost forecasts also are reported in this paper.

Some implications of this study for the further development of prescriptive models of the decision-making process in the fruit-frost context and in other weather-information-sensitive contexts are discussed.

Full access
Thomas R. Stewart
,
William R. Moninger
,
Ray H. Brady
,
Frank H. Merrem
,
Thomas R. Stewart
, and
Janet Grassia

Abstract

This study compared meteorologists, an expert system, and simple weighted-sum models in a limited-information hail forecasting experiment. It was found that forecasts made by meteorologists were closely approximated by an additive model, and that the model captured most of their forecasting skill. Furthermore, the additive model approximated the meteorologists’ forecasts better than the expert system did. Results of this study am consistent with the results of extensive psychological research on judgment and decision making processes. Potential implications are discussed.

Full access
Kenneth F. Heideman
,
Thomas R. Stewart
,
William R. Moninger
, and
Patricia Reagan-Cirincione

Abstract

The relationship between the quality and quantity of information available to meteorologists and the skill of their forecasts was investigated. Twelve meteorologists were asked to make probabilistic forecasts of significant and severe weather events under three information conditions. Forecast accuracy was generally low. As the amount and quality of the information increased substantially, there was a modest increase in the accuracy of the forecasts. However, the results suggest that the forecasters were least consistent when they had the most information to work with, partially reducing the benefits of the increased information.

Full access
Cynthia M. Lusk
,
Thomas R. Stewart
,
Kenneth R. Hammond
, and
Rodney J. Potts

Abstract

Two studies of microburst forecasting were conducted in order to demonstrate the utility of applying theoretical and methodological concepts from judgment and decision making to meteorology. A hierarchical model of the judgment process is outlined in which a precursor identification phase is separated from the prediction phase. In the first study, forecasters were provided with specific, unambiguous precursor values and were asked to provide judgments regarding the probability of a microburst. Results indicated that the meteorologists' forecast were adequately predicted by a linear model. Modest agreement was observed among the forecasters’ judgments. In the second study, forecasters viewed storms under dynamic conditions representative of their usual operational setting. They made judgments regarding precursor values, as well as of the probability of a microburst occurring. The forecasters’ agreement regarding microburst predictions was found to be lower than in the first study. Surprisingly, agreement regarding the (subjectively) most important precursor value was near zero. These results indicate that there are indeed practical advantages to be gained from a better understanding of the precursor identification and prediction phases of the forecasting process.

Full access
Thomas C. Peterson
,
Richard R. Heim Jr.
,
Robert Hirsch
,
Dale P. Kaiser
,
Harold Brooks
,
Noah S. Diffenbaugh
,
Randall M. Dole
,
Jason P. Giovannettone
,
Kristen Guirguis
,
Thomas R. Karl
,
Richard W. Katz
,
Kenneth Kunkel
,
Dennis Lettenmaier
,
Gregory J. McCabe
,
Christopher J. Paciorek
,
Karen R. Ryberg
,
Siegfried Schubert
,
Viviane B. S. Silva
,
Brooke C. Stewart
,
Aldo V. Vecchia
,
Gabriele Villarini
,
Russell S. Vose
,
John Walsh
,
Michael Wehner
,
David Wolock
,
Klaus Wolter
,
Connie A. Woodhouse
, and
Donald Wuebbles

Weather and climate extremes have been varying and changing on many different time scales. In recent decades, heat waves have generally become more frequent across the United States, while cold waves have been decreasing. While this is in keeping with expectations in a warming climate, it turns out that decadal variations in the number of U.S. heat and cold waves do not correlate well with the observed U.S. warming during the last century. Annual peak flow data reveal that river flooding trends on the century scale do not show uniform changes across the country. While flood magnitudes in the Southwest have been decreasing, flood magnitudes in the Northeast and north-central United States have been increasing. Confounding the analysis of trends in river flooding is multiyear and even multidecadal variability likely caused by both large-scale atmospheric circulation changes and basin-scale “memory” in the form of soil moisture. Droughts also have long-term trends as well as multiyear and decadal variability. Instrumental data indicate that the Dust Bowl of the 1930s and the drought in the 1950s were the most significant twentieth-century droughts in the United States, while tree ring data indicate that the megadroughts over the twelfth century exceeded anything in the twentieth century in both spatial extent and duration. The state of knowledge of the factors that cause heat waves, cold waves, floods, and drought to change is fairly good with heat waves being the best understood.

Full access
Robert J. H. Dunn
,
Freya Aldred
,
Nadine Gobron
,
John B. Miller
,
Kate M. Willett
,
Melanie Ades
,
Robert Adler
,
R. P. Allan
,
John Anderson
,
Orlane Anneville
,
Yasuyuki Aono
,
Anthony Argüez
,
Carlo Arosio
,
John A. Augustine
,
Cesar Azorin-Molina
,
Jonathan Barichivich
,
Aman Basu
,
Hylke E. Beck
,
Nicolas Bellouin
,
Angela Benedetti
,
Kevin Blagrave
,
Stephen Blenkinsop
,
Olivier Bock
,
Xavier Bodin
,
Michael G. Bosilovich
,
Olivier Boucher
,
Gerald Bove
,
Dennis Buechler
,
Stefan A. Buehler
,
Laura Carrea
,
Kai-Lan Chang
,
Hanne H. Christiansen
,
John R. Christy
,
Eui-Seok Chung
,
Laura M. Ciasto
,
Melanie Coldewey-Egbers
,
Owen R. Cooper
,
Richard C. Cornes
,
Curt Covey
,
Thomas Cropper
,
Molly Crotwell
,
Diego Cusicanqui
,
Sean M. Davis
,
Richard A. M. de Jeu
,
Doug Degenstein
,
Reynald Delaloye
,
Markus G. Donat
,
Wouter A. Dorigo
,
Imke Durre
,
Geoff S. Dutton
,
Gregory Duveiller
,
James W. Elkins
,
Thomas W. Estilow
,
Nava Fedaeff
,
David Fereday
,
Vitali E. Fioletov
,
Johannes Flemming
,
Michael J. Foster
,
Stacey M. Frith
,
Lucien Froidevaux
,
Martin Füllekrug
,
Judith Garforth
,
Jay Garg
,
Matthew Gentry
,
Steven Goodman
,
Qiqi Gou
,
Nikolay Granin
,
Mauro Guglielmin
,
Sebastian Hahn
,
Leopold Haimberger
,
Brad D. Hall
,
Ian Harris
,
Debbie L. Hemming
,
Martin Hirschi
,
Shu-pen (Ben) Ho
,
Robert Holzworth
,
Filip Hrbáček
,
Daan Hubert
,
Petra Hulsman
,
Dale F. Hurst
,
Antje Inness
,
Ketil Isaksen
,
Viju O. John
,
Philip D. Jones
,
Robert Junod
,
Andreas Kääb
,
Johannes W. Kaiser
,
Viktor Kaufmann
,
Andreas Kellerer-Pirklbauer
,
Elizabeth C. Kent
,
Richard Kidd
,
Hyungiun Kim
,
Zak Kipling
,
Akash Koppa
,
Jan Henning L’Abée-Lund
,
Xin Lan
,
Kathleen O. Lantz
,
David Lavers
,
Norman G. Loeb
,
Diego Loyola
,
Remi Madelon
,
Hilmar J. Malmquist
,
Wlodzimierz Marszelewski
,
Michael Mayer
,
Matthew F. McCabe
,
Tim R. McVicar
,
Carl A. Mears
,
Annette Menzel
,
Christopher J. Merchant
,
Diego G. Miralles
,
Stephen A. Montzka
,
Colin Morice
,
Leander Mösinger
,
Jens Mühle
,
Julien P. Nicolas
,
Jeannette Noetzli
,
Tiina Nõges
,
Ben Noll
,
John O’Keefe
,
Tim J. Osborn
,
Taejin Park
,
Cecile Pellet
,
Maury S. Pelto
,
Sarah E. Perkins-Kirkpatrick
,
Coda Phillips
,
Stephen Po-Chedley
,
Lorenzo Polvani
,
Wolfgang Preimesberger
,
Colin Price
,
Merja Pulkkanen
,
Dominik G. Rains
,
William J. Randel
,
Samuel Rémy
,
Lucrezia Ricciardulli
,
Andrew D. Richardson
,
David A. Robinson
,
Matthew Rodell
,
Nemesio J. Rodríguez-Fernández
,
Karen H. Rosenlof
,
Chris Roth
,
Alexei Rozanov
,
This Rutishäuser
,
Ahira Sánchez-Lugo
,
Parnchai Sawaengphokhai
,
Verena Schenzinger
,
Robert W. Schlegel
,
Udo Schneider
,
Sapna Sharma
,
Lei Shi
,
Adrian J. Simmons
,
Carolina Siso
,
Sharon L. Smith
,
Brian J. Soden
,
Viktoria Sofieva
,
Tim H. Sparks
,
Paul W. Stackhouse Jr.
,
Ryan Stauffer
,
Wolfgang Steinbrecht
,
Andrea K. Steiner
,
Kenton Stewart
,
Pietro Stradiotti
,
Dimitri A. Streletskiy
,
Hagen Telg
,
Stephen J. Thackeray
,
Emmanuel Thibert
,
Michael Todt
,
Daisuke Tokuda
,
Kleareti Tourpali
,
Mari R. Tye
,
Ronald van der A
,
Robin van der Schalie
,
Gerard van der Schrier
,
Mendy van der Vliet
,
Guido R. van der Werf
,
Arnold. van Vliet
,
Jean-Paul Vernier
,
Isaac J. Vimont
,
Katrina Virts
,
Sebastiàn Vivero
,
Holger Vömel
,
Russell S. Vose
,
Ray H. J. Wang
,
Markus Weber
,
David Wiese
,
Jeanette D. Wild
,
Earle Williams
,
Takmeng Wong
,
R. I. Woolway
,
Xungang Yin
,
Ye Yuan
,
Lin Zhao
,
Xinjia Zhou
,
Jerry R. Ziemke
,
Markus Ziese
, and
Ruxandra M. Zotta
Free access