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Patrick T. Marsh, John S. Kain, Valliappa Lakshmanan, Adam J. Clark, Nathan M. Hitchens, and Jill Hardy

1. Introduction Rare meteorological events 1 that occur on small spatial and short temporal scales pose significant challenges to forecasters. This is related to the limited predictability of phenomena occurring on short time–space scales. However, these events compose a substantial portion of meteorological phenomena that negatively impact society, such as heavy rain, large hail, and tornadoes. Thus, accurate numerical guidance of these events would provide large societal benefits. Convection

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Tirthankar Roy, Xiaogang He, Peirong Lin, Hylke E. Beck, Christopher Castro, and Eric F. Wood

1. Introduction The North American Multi-Model Ensemble (NMME; Kirtman et al. 2014 ) system incorporates seasonal forecasts of different hydroclimatic variables from multiple U.S. and Canadian models. These forecasts are invaluable for a plethora of scientific and operational applications, including precipitation and temperature forecasting ( Setiawan et al. 2017 ; Wang 2014 ; Krakauer 2017 ; Cash et al. 2019 ; Wanders et al. 2017 ), prediction of extremes ( Yuan et al. 2015 ), atmospheric

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David T. Myrick and John D. Horel

1. Introduction The National Weather Service (NWS) has extensively revised the procedures used by forecasters to create and distribute forecasts of sensible weather elements. Instead of manually typing text forecast products, forecasters now use graphical editors included in the Interactive Forecast Preparation System (IFPS) to create high-resolution gridded forecasts of weather elements that can be viewed graphically by customers as well as downloaded for specific user applications ( Ruth 2002

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Jonathan Lin, Kerry Emanuel, and Jonathan L. Vigh

1. Introduction Tropical cyclones (TCs) are complex weather systems that bring flooding, storm surge, high winds, and other hazards to many coastal and island locations. Each year, TCs cause billions of dollars in damage to businesses and property and result in the loss of numerous lives ( Pielke et al. 2008 ). To mitigate such losses and allow vulnerable populations to undertake life-saving preparations, TC forecasts must be provided with sufficient lead time and be reasonably accurate and

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Andreas P. Weigel, Daniel Baggenstos, Mark A. Liniger, Frédéric Vitart, and Christof Appenzeller

1. Introduction Probabilistic ensemble forecasts have become a standard technique in numerical weather and climate forecasting. Particularly in the context of weather and climate risk management, the probability information provided by ensembles is important in that it allows us to foresee forecast uncertainties and thus the limits of predictability. Depending on the time scales considered, and ignoring uncertainties due to model errors, ensembles sample two kinds of forecast uncertainty

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Q. J. Wang, Andrew Schepen, and David E. Robertson

1. Introduction Seasonal climate forecasts are in high demand in Australia, and seasonal rainfall forecasts in particular are sought by farmers, water managers, and others throughout the year. The Australian Bureau of Meteorology provides probabilistic forecasts of seasonal rainfall using a statistical prediction system based on sea surface temperature (SST) anomaly patterns over the Indian and Pacific Oceans ( Drosdowsky and Chambers 2001 ; Fawcett et al. 2005 ). Different forecast models are

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Min Li, Ting Zhang, Jianzhu Li, and Ping Feng

approach, the contributions of climate change and human activities were 7%–49% and 51%–93%, respectively. Based on the Budyko decomposition method, the impacts of climate change and human activities accounted for 15%–40% and 60%–85% of the decrease in runoff, respectively. Drought forecasting is typically based on probability theory and statistical principles, such as principal component analysis, regression analysis, time series models, Markov processes, gray systems, and artificial neural networks

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James S. Goerss and Charles R. Sampson

1. Introduction Consensus tropical cyclone (TC) intensity forecast aids formed using TC intensity forecasts from statistical models and regional numerical weather prediction models have become increasingly important in recent years as guidance for forecasters at both the National Hurricane Center (NHC) and the Joint Typhoon Warning Center (JTWC). Two of these consensus forecast aids are IVCN, which is available for forecasting in the Atlantic and eastern North Pacific, and S5YY, which is

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Randal D. Koster, Thomas L. Bell, Rolf H. Reichle, Max J. Suarez, and Siegfried D. Schubert

1. Introduction The strategy employed for forecasting meteorological variables such as precipitation and air temperature in large part relies on the lead time of the forecast. For medium-range weather forecasts, extending out to about a week, forecast skill relies mostly on the correct initialization of atmospheric states. For seasonal-to-interannual (SI) forecasts, however, atmospheric initialization has almost no impact on skill. SI forecasts must instead rely on the slower-moving components

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Ricardo Martins Campos, Jose-Henrique G. M. Alves, Stephen G. Penny, and Vladimir Krasnopolsky

1. Introduction Accurate wave forecasts are important for monitoring waves that threaten ships either at sea or at harbor, as well as offshore and coastal structures. When dealing with structures and wave energy converters, model skill becomes very important due to the quadratic relation of the wave energy in relation to the wave height, according to linear wave theory ( Airy 1841 ). For a monochromatic wave, the total energy is integrated over the wavelength, which is directly proportional to

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