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Carlee F. Loeser, Michael A. Herrera, and Istvan Szunyogh

major difficulties with predicting the large-scale atmospheric flow in the long (longer than 240 h) forecast range. These difficulties are due to the inability of the ensemble members to maintain large-scale waves in the forecasts, which presents a stumbling block in the way of extending the skill of numerical weather forecasts to the subseasonal range. The results show that the current technology of ensemble forecasting can provide reliable prediction of the first and second central moments of the

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Juanzhen Sun, Stanley B. Trier, Qingnong Xiao, Morris L. Weisman, Hongli Wang, Zhuming Ying, Mei Xu, and Ying Zhang

occasional short-wave features propagating through this overall upper-level regime. Key surface features at the beginning of the period included generally moist, unstable conditions supportive of convection through most of the region, with a dryline in the western portion of the domain. Fig . 1. (a)–(f) Synoptic conditions during the 10–16 Jun 2002 IHOP retrospective period as determined from 13-km RUC model analyses. Plots are of 500-hPa winds (full barb = 5 m s −1 , half barb = 2.5 m s −1 , and pennant

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Peter J. Bowyer and Allan W. MacAfee

the ability of atmospheric models to generate the correct wind field ( Tolman et al. 2002 ). This is especially true on regional scales ( Cardone et al. 1996 ; Moon et al. 2003 ). Because of their versatility, spectral wave models are required for general wave modeling; however, under certain conditions, a model built using a representative wave method, such as the significant wave height, is also viable ( SWAMP Group 1985 ). Along with these developments in the science of wave forecasting, the

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Steven E. Koch and Christopher O’Handley

1. Introduction Most weather forecasters learn in their undergraduate or military courses in atmospheric dynamics that internal gravity waves result from the action of the restoring force of gravity acting upon air parcels that are displaced vertically in a statically stable atmosphere (e.g., Holton 1992 ). Forecasters may also have learned of the destabilizing effects of vertical wind shear on internal waves, or studied gravity–inertia waves, in which the Coriolis force further alters wave

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Jean-Raymond Bidlot, Damian J. Holmes, Paul A. Wittmann, Roop Lalbeharry, and Hsuan S. Chen

1. Introduction Any operational weather center involved in wave prediction should have some form of quality monitoring of its products. For quite some time now, operational weather centers have systematically exchanged statistical information (scores) in an attempt to further diagnose the quality of their atmospheric model; however, prior to the end of 1995, no systematic comparative study of the different wave forecasting systems existed. In the past, there have been some efforts to evaluate

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Bruce H. Bauck

innew depressions and so on. These unbalanced horizontal pressure gradients will continue to produce anoutward propagation of the wave disturbance. Atmospheric gravity waves propagate in much the samemanner. However, the atmosphere has no sharp upperboundary and vertical propagation of energy is possibleif no duct or inversion is present. A duct, in this context,is a layer in which strong temperature and moisturegradients act to reflect and transmit or guide wave energy horizontally (Lindzen and

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Øyvind Saetra and Jean-Raymond Bidlot

1. Introduction In June 1998, the Ensemble Prediction System (EPS) at the European Centre for Medium-Range Weather Forecasts (ECMWF) was coupled to the ocean wave model. From then on, daily ensemble wave forecasts have been available. Although the positive impact on both the atmospheric and the wave forecasts was the main reason for the introduction of the coupling ( Janssen et al. 2002 ), probabilistic forecasts of ocean waves are also potentially very valuable products by themselves. There

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Gabriel García-Medina, H. Tuba Özkan-Haller, Peter Ruggiero, and Jeffrey Oskamp

-shelf wave predictions need to resolve the relevant bathymetric features and account for the associated wave transformation processes. The National Oceanic and Atmospheric Administration's (NOAA) National Weather Service (NWS) operates a third-generation wave forecasting model called WAVEWATCH III. This model contains the necessary physics to account for shelf-scale wave transformation processes if the bathymetry at the relevant length scales is defined. However, the current forecasts in the eastern

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W. F. Feltz, K. M. Bedka, J. A. Otkin, T. Greenwald, and S. A. Ackerman

1. Introduction Atmospheric turbulence is a major aviation hazard responsible for 609 fatalities, 823 injuries, and an estimated property loss of $134M from 1983 to 1997 ( Eichenbaum 2000 ). Aircraft turbulence is often associated with rapid thunderstorm development (e.g., Lane et al. 2003 ), upper-tropospheric folding events (e.g., Endlich 1964 ; Koch et al. 2005 ), and topographically induced mountain-wave and rotor phenomena (e.g., Reiter and Foltz 1967 ; Clark and Gall 1982 ; Clark et

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Hendrik L. Tolman, Jose-Henrique G. M. Alves, and Yung Y. Chao

1. Introduction Hurricane Isabel made landfall on the east coast of the United States near Cape Hatteras on 18 September 2003 (see Fig. 1 ). Due to the size and intensity of Isabel, extreme wave conditions were observed and predicted along the coast. Significant wave heights greater than 10 m were observed about 250 nm offshore at National Data Buoy Center (NDBC) buoys 41001 and 41002, which were located on either side of the corridor of predicted maximum wave heights. NDBC buoy 41025, located

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