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Jung-Hoon Kim, Robert D. Sharman, Stanley G. Benjamin, John M. Brown, Sang-Hun Park, and Joseph B. Klemp

. 1 , which covers the entire North American continent including the contiguous United States (CONUS), Canada, Mexico, Hawaii, and Alaska to provide better forecast products over the CONUS, North Pacific and Atlantic Oceans, and Alaska regions. The domain has a 13-km horizontal mesh with 51 sigma (eta) levels in the terrain-following vertical coordinate used in the RAPv3 and earlier. This has been updated to use the hybrid pressure–sigma vertical coordinate system in the RAPv4 that is a focus of

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Ray Bell and Ben Kirtman

interested in how the storm track behaves overall during the winter months. Brayshaw et al. (2009) noted that midlatitude orography and the land–sea temperature contrast on the east coast of North America play a role in determining the southwest–northeast tilt of the upper-tropospheric jet. In addition, sea surface temperature (SST) gradients in the North Atlantic act to perturb the jet stream. Gradients in the western North Atlantic, such as the Gulf Stream, strengthen the jet downstream, while

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Dan L. Bergman, Linus Magnusson, Johan Nilsson, and Frederic Vitart

key factor impacting the extent of the damage caused. The present paper reports the results of an investigation of the possibility to use ECMWF’s seasonal forecast system 4 (System 4) to forecast TC and hurricane landfall risk along different segments of the North American Atlantic and Gulf coasts, with a particular focus on the U.S. part of the coast. For this purpose, a method has been developed to forecast landfall using the ensembles of storm tracks generated by System 4, and the quality of

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Clark Evans, Steven J. Weiss, Israel L. Jirak, Andrew R. Dean, and David S. Nevius

profiles and derived thermodynamic parameters are evaluated for two closely related operational regional and convection-allowing model pairs: the North American Mesoscale Forecast System (NAM; e.g., Janjić and Gall 2012 ; Environmental Modeling Center 2017 and references therein) model and its conterminous U.S. convection-allowing nest (NAM Nest), and the Rapid Refresh (RAP; Benjamin et al. 2016 ) and High Resolution Rapid Refresh (HRRR; Smith et al. 2008 , Benjamin et al. 2016 ) models. These

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Todd A. Hutchinson

into south-central Canada or the north-central United States before moving eastward to thecoast of North America, were studied using the National Meteorological Center's Nested Grid Model ( NGM ).All available NGM forecasts between I January 1988 and 31 December 1992, excluding the months of June,July, and August, were analyzed. The 5-yr sample included 59 Alberta Clippers. For each case, the cyclonecenter position and central pressure were recorded for the NGM's initialization (0 h) and for 12

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Richard H. Grumm, Robert J. Oravec, and Anthony L. Siebers

fill. About 15% of the time in the winter months, the NGM forecast cyclones todeepen when they were observed to fill. The NGM had difficulty detecting the initial development of surface cyclones, especially near the elevatedterrain of western North America and along the track of transient cyclones. In these same regions, the NGMtended to forecast cyclones that were not observed. There was a preponderance of both nonobserved andnonforecast cyclones over the elevated terrain of North America

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Kai-Yu Ma and Lance F. Bosart

convective complex appeared tobe comparable to what has been seen in similar cases over North America. Warm air advection in the lower troposphere appeared to help trigger the rainfall through weak synopticscale ascent of I-2 cm s-~. An analysis of the water vapor flux revealed the South China Sea as a moisturesource in the surface-to-850 mb layer, and the Indian subcontinent-Bay of Bengal region as the moisture sourcein the 850-500 mb layer.1. Introduction This paper presents a synoptic analysis

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Ghassan J. Alaka Jr., Xuejin Zhang, Sundararaman G. Gopalakrishnan, Zhan Zhang, Frank D. Marks, and Robert Atlas

96 h. HBE1 and HBE2 have 80 total members. HBE3, HBE4, and HBE5 have 25 total members. Table 4. Track error statistics (km) for all HBE experiments at a lead time of 120 h. HBE1 and HBE2 have 80 total members. HBE3, HBE4, and HBE5 have 25 total members. b. Impact of the synoptic-scale environment The synoptic-scale environment over the North Atlantic Ocean and North America evolved rapidly from 0000 UTC 1 October 2015 to 1200 UTC 3 October 2015 and significantly influenced the steering flow near

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Yuejian Zhu, Xiaqiong Zhou, Malaquias Peña, Wei Li, Christopher Melhauser, and Dingchen Hou

the tropics, the Madden–Julian oscillation (MJO; Madden and Julian 1971 , 1972 ) was found to be a key phenomenon for extended-range prediction due to its 40–50-day oscillation time scale. In the Northern Hemisphere (NH), the Pacific–North American (PNA) and North Atlantic Oscillation (NAO) patterns in the mid- to high latitudes have been found to be sources of extended-range predictability ( Wallace and Gutzler 1981 ; Barnston and Livezey 1987 ). In particular, specific blocking patterns can

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Norman W. Junker, James E. Hoke, and Richard H. Grumm

368WEATHER AND FORECASTINGVOLUME Performance of NMC's Regional ModelsNORMAN W. JUNKER, JAMES E. HOKE AND RICHARD H. GRUMMNational Meteorological Center, NW$, NOAA, Washington, D.C.(Manuscript received 4 March 1989, in final form 4 May 1989) ABSTRACT This paper details the performance characteristics of the two regional dynamical models used at the.NationalMeteorological Center to forecast for North America. Strengths and weaknesses of these models--the limitedarea

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