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Malte Müller, Yurii Batrak, Jørn Kristiansen, Morten A. Ø. Køltzow, Gunnar Noer, and Anton Korosov

(AROME-Arctic) has been in operation since November 2015. Forecast analyses are derived via a 3DVAR data assimilation scheme and observations from various sources, including synoptic, radiosonde, airplane, and satellite data. It is the main Arctic weather forecasting tool used by the Norwegian Meteorological Institute, which has national and international responsibilities for weather, sea ice, and ocean prediction in large parts of the European Arctic. The recent entry into service of the operational

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Philip Muscarella, Matthew J. Carrier, Hans Ngodock, Scott Smith, B. L. Lipphardt Jr., A. D. Kirwan Jr., and Helga S. Huntley

altimeters) observations are typically assimilated in operational ocean models. However, it should be noted that along-track SSH observations are not assimilated directly; they are used to calculate synthetic profiles of temperature and salinity, and it is these synthetic profiles that are assimilated. Since these observations directly constrain only the model mass field, thus influencing only the barotropic component of the flow, their impact on trajectory forecast skill is unclear. In addition, SSH

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Ron McTaggart-Cowan and Ayrton Zadra

at the bottom of the plot. 4. Forecast case study Operational forecasters with Environment Canada regularly report on the performance of GEM-based guidance systems so that model developers can address issues that adversely affect the forecast process. One of the primary failure modes noted by these meteorologists is that of the warm episode (hereafter italicized when used to denote this class of model error), in which surface air temperature (SAT; taken at the standard 2-m level) errors can

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M. U. Altaf, T. Butler, X. Luo, C. Dawson, T. Mayo, and I. Hoteit

Louisiana and Mississippi. Part II: Synoptic description and analyses of Hurricanes Katrina and Rita . Mon. Wea. Rev. , 138 , 378 – 404 . Dietrich , J. , and Coauthors , 2011 : Hurricane Gustav (2008) waves and storm surge: Hindcast, synoptic analysis, and validation in southern Louisiana . Mon. Wea. Rev. , 139 , 2488 – 2522 . El Serafy , G. Y. H. , and A. E. Mynett , 2008 : Improving the operational forecasting system of the stratified flow in Osaka Bay using an ensemble Kalman filter

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Michael A. Hollan and Brian C. Ancell

1. Introduction Substantial progress has been made in numerical weather prediction (NWP) over the last few decades that has allowed for a more accurate representation and prediction of deep moist convection by atmospheric models. Convective systems can now be explicitly modeled, and radar reflectivity can now be calculated by the model and used as model output ( Koch et al. 2005 ). This has proven to be a beneficial forecasting tool in the operational meteorology community ( Kain et al. 2006

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Elizabeth R. Sanabia, Bradford S. Barrett, Nicholas P. Celone, and Zachary D. Cornelius

120 kt ( Hawkins and Helveston 2004 ), indicating that they are a common feature of strong typhoons. Furthermore, because surface wind speed often weakens while the wind field expands during the ERC process, CEs often complicate the operational TC forecast ( Kossin and Sitkowski 2009 ). Despite their frequency, in basins without routine aircraft reconnaissance, such as the western North Pacific Ocean, the primary data source used to operationally identify CE structures is infrequently and

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Jonathan Labriola, Nathan Snook, Ming Xue, and Kevin W. Thomas

( Clark et al. 2012a ). CAMs are increasingly used operationally (e.g., Benjamin et al. 2016 ; Jirak et al. 2018 ), and multiple research organizations run CAM forecasts routinely (e.g., Coniglio et al. 2010 ; Clark et al. 2012a ; Schwartz et al. 2015 ; Gallo et al. 2017 ; Sobash et al. 2016 ). The Hazardous Weather Testbed (HWT) Spring Forecasting Experiment (SFE), performed each year during the climatological maximum for severe weather over the United States ( Clark et al. 2012a ), has

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Jun A. Zhang, Robert F. Rogers, and Vijay Tallapragada

. 2013 ). Accurately representing these scale interactions in numerical models is a challenge, and for this reason forecasting RI remains difficult. Much research has gone into identifying characteristics of the large-scale environment that are conducive to RI. Using data from the operational Statistical Hurricane Intensity Prediction Scheme (SHIPS) model, Kaplan et al. (2015) showed that TCs that undergo RI are situated in regions with lower vertical environmental wind shear, greater upper

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Reto Stauffer, Nikolaus Umlauf, Jakob W. Messner, Georg J. Mayr, and Achim Zeileis

(SAMOS) approach and extend the framework to fulfill all requirements needed for precipitation postprocessing. SAMOS offers a simple and computationally efficient framework for fully probabilistic spatial postprocessing and is applied to the European Centre for Medium-Range Weather Forecasts (ECMWF) ensemble in combination with the ECMWF reforecasts. The approach presented qualifies for an operational system as no extensive archive of historical forecasts is required. SAMOS uses a rolling 4-week time

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Kelly Mahoney, Darren L. Jackson, Paul Neiman, Mimi Hughes, Lisa Darby, Gary Wick, Allen White, Ellen Sukovich, and Rob Cifelli

consistent with the 2012–14 version of the operational NCEP GEFS. The “fixed” status of the dataset allows one to evaluate forecast performance over an extended period of time without having to account for changes in operational modeling systems. 3. IWV and IVT climatological comparison between the western and southeast United States WCUS ARs have been defined in many past studies using IWV as the main metric of identification (e.g., Neiman et al. 2008 , and many others); however, originally ( Newell et

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