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Mark J. Rodwell
and
Francisco J. Doblas-Reyes

) based on the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) record ( Uppala et al. 2005 ). The much higher daily observed values for summer 2003 are shown by the dotted curve. Horizontal dashed and dotted lines show the corresponding weekly mean and monthly mean values. Important questions are how well was this 2003 event “predicted,” and what impact did the predictions have on decision making? The solid black curve shows a single high-resolution forecast

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Jean-Jacques Morcrette
,
George Mozdzynski
, and
Martin Leutbecher

this radiation burden, radiation transfer is only computed every few model hours. For example, with full radiation computations performed every 2 h at all grid points, radiation transfer accounts for 27% of the run time of the “GME” forecast model ( Majewski et al. 2002 ). The recent introduction of the McRad package for radiation computations ( Morcrette et al. 2008 ) in the Integrated Forecasting System (IFS) has increased the cost of the radiation computations and required revisiting the use of

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Cristina Primo
,
Christopher A. T. Ferro
,
Ian T. Jolliffe
, and
David B. Stephenson

1. Introduction Probabilistic forecasts represent the uncertainty in a prediction by a probability distribution for the predictand. This distribution may be derived from historical errors of deterministic forecasts or from ensemble forecasts (see Leith 1974 ; Ehrendorfer 1997 ; Stephenson and Doblas-Reyes 2000 , and references therein). In the latter case, probabilistic forecasts for binary events are often obtained as the relative frequency with which the event occurs in the ensemble. For

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William S. Lamberson
,
Ryan D. Torn
,
Lance F. Bosart
, and
Linus Magnusson

1. Introduction The last 30 years have been characterized by a significant improvement in the quality of medium-range (3–10 day) forecasts of midlatitude weather systems. Presently, 6-day forecasts issued by the European Centre for Medium-Range Weather Forecasts (ECMWF) for the Northern Hemisphere extratropics are as accurate as 5-day forecasts issued in the early 2000s, 4-day forecasts issued in the mid-1990s, and 3-day forecasts issued in the early 1980s ( Richardson et al. 2013 ). These

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Michael C. Kochasic
,
William A. Gallus Jr.
, and
Christopher J. Schaffer

1. Introduction Numerous probability of precipitation (PoP) forecast generation approaches exist, with the simplest approach considering the agreement between members of an ensemble prediction system (EPS). If there are 10 ensemble members, for example, with two showing precipitation exceeding a specified threshold amount, then the PoP for that threshold is 20%. This approach is referred to as the uncalibrated traditional approach (denoted Uncali_trad hereafter) in Schaffer et al. (2011

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Linus Magnusson
,
Jean-Raymond Bidlot
,
Simon T. K. Lang
,
Alan Thorpe
,
Nils Wedi
, and
Munehiko Yamaguchi

behind the rapid deepening of the cyclone the day before the landfall is given in Galarneau et al. (2013) . The European Centre for Medium-Range Weather Forecasts (ECMWF) has improved the average skill of its tropical cyclone predictions in the past decade ( Richardson et al. 2013 ). However, it is the performance of weather forecasts in individual high-profile cases such as Sandy that can establish and retain the trust and confidence of the public and other forecast users, in a way disproportionate

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Grace Zalenski
,
Witold F. Krajewski
,
Felipe Quintero
,
Pedro Restrepo
, and
Steve Buan

1. Introduction The National Weather Service (NWS) has the mandate of providing streamflow forecast services for the United States. To meet its function, it relies on observations from the U.S. Geological Survey (USGS), the U.S. Army Corps of Engineers, and a number of federal, state, and tribal partners that supply streamflow, snow, temperature, and other variables used in the forecast process. Hydrologic forecasts produced by the NWS in real time, specifically river streamflow forecasts, are

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Kevin Werner
and
Kristen Yeager

1. Introduction This paper describes the 2011 peak streamflows in the Colorado basin and the Great Basin in an attempt to illuminate the forecasting efforts of the NOAA Colorado Basin River Forecast Center (CBRFC). A recent National Research Council (2012) report highlighted the difficulties in transferring research results into operational river forecasting as a major impediment to improving forecasts. The primary goal of this paper is to highlight three areas where research is most needed

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Thomas C. Pagano
,
Andrew W. Wood
,
Maria-Helena Ramos
,
Hannah L. Cloke
,
Florian Pappenberger
,
Martyn P. Clark
,
Michael Cranston
,
Dmitri Kavetski
,
Thibault Mathevet
,
Soroosh Sorooshian
, and
Jan S. Verkade

1. Introduction Recent water-related disasters have captured public attention and led to increased interest in hydrologic forecasting systems. Flooding was responsible for nearly half of all natural catastrophe-related losses in 2013, with floods in Europe, Asia, Canada, the United States, and Australia causing over $20 billion (U.S. dollars) in losses [see www.swissre.com/media/news_releases/nr_20130821_sigma_natcat_estimates_H1_2013.html and Coffman (2013) ]. The human toll in developing

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Allen B. White
,
Daniel J. Gottas
,
Arthur F. Henkel
,
Paul J. Neiman
,
F. Martin Ralph
, and
Seth I. Gutman

1. Introduction The “snow level” is a term used by National Oceanic and Atmospheric Administration’s (NOAA) forecasters at the National Weather Service (NWS) to ascribe the altitude in the atmosphere where falling snow melts to rain. The snow level should be distinguished from another term used by forecasters, the “free atmosphere freezing level,” which is the altitude corresponding to the 0°C isotherm. However, in cloud physics and in other fields, the term “melting level” is often used in

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