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Michael J. Brennan, Hugh D. Cobb III, and Richard D. Knabb

forecasters include forecasts and warnings for Tehuantepec events in a high seas forecast 2 issued 4 times daily (at 0430, 1030, 1630, and 2230 UTC). NWP model guidance available in the region includes various global models, including the NCEP Global Forecast System (GFS). During the 2006/07 season the domain of the NCEP North American Mesoscale (NAM) model was expanded to include the Gulf of Tehuantepec region. This section will show the results of an evaluation of operational model guidance from the

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Jingyu Wang, Xiquan Dong, Aaron Kennedy, Brooke Hagenhoff, and Baike Xi

simulation under each SOM class. Finally, conclusions and suggestions for model improvement are discussed in section 4 . 2. Data and methodology a. NSSL-WRF simulation NSSL has run a daily (0000 UTC), 4-km, deterministic, Advanced Research version of WRF (WRF-ARW) simulation in support of the SFE from 2007 to present. Integrated over 36 h, the simulations have 35 vertical levels and a time step of 24 s. Run as a singular domain, initial and lateral boundary conditions were provided by the North American

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Steven L. Mullen and Bruce B. Smith

-level cyclone errors which occurred in 24- and 48-h forecasts of the National MeteorologicalCenter's nested grid model (NGM) is performed for the 1987-88 winter season ( 1 December 1987-31 March1988). All available 0000 UTC and 1200 UTC forecast cycles are analyzed for North America and adjacentocean regions. Errors in forecasted central pressure and position are computed. NGM forecasts of cyclone central pressure average 0.6 mb too deep at 24 hours and 0.3 mb too deep at 48hours, The root

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Talmor Meir, Philip M. Orton, Julie Pullen, Teddy Holt, William T. Thompson, and Mark F. Arend

metropolitan area and the Weather Research and Forecasting (WRF) North American Mesoscale (NAM) domain, as well as regional land- and coast-based sensor networks (available through the NYCMetNet website; ), all of which are discussed in detail in section 2 . We evaluate the ability of the models to capture the interaction between the urbanized region and the atmosphere, with a particular focus on the sensitivity of the models in relation to urban–coastal circulation

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Matthew T. Vaughan, Brian H. Tang, and Lance F. Bosart

report density. We attempted to capture the preconvective environment within the CFSR for a majority of the cases and therefore used the 1800 UTC analysis for each event day as a representative time before the climatological diurnal peak in severe weather ( Hurlbut and Cohen 2014 ). The data-gathering process was repeated using the North American Regional Reanalysis (NARR) at 32-km grid spacing ( Mesinger et al. 2006 ). Following Lombardo and Colle (2011) , we chose the closest 3-h NARR analysis

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Shawn M. Milrad, John R. Gyakum, Eyad H. Atallah, and Jennifer F. Smith

thermodynamic analyses performed for this manuscript were completed using the National Centers for Environmental Prediction (NCEP) North American Regional Reanalysis (NARR), with a horizontal resolution of 32 km, and a 3-hourly temporal resolution ( Mesinger et al. 2006 ). NARR fields were compared with the ½° horizontal resolution NCEP Global Forecast System (GFS) analysis and the NCEP–NCAR Global Reanalysis ( Kalnay et al. 1996 ) and were found to be qualitatively similar in terms of both quasigeostrophic

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Wan-Shu Wu, David F. Parrish, Eric Rogers, and Ying Lin

Data Assimilation System (GDAS) in May 2012 and was used in studies with the Global Forecast System (GFS) system ( Wang et al. 2013 ; Kleist and Ide 2015a , b ). The same 3DEnVar scheme in the GSI is employed in this study for the North American Mesoscale Forecast System (NAM) Data Assimilation System (NDAS) at NCEP. Xu et al. (2008) and Zhao et al. (2015) showed that the time-expanded sampling method could be used to reduce the number of forecast runs needed to produce an ensemble with the

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Tom H. Durrant, Frank Woodcock, and Diana J. M. Greenslade

only five models available, two of which were high-resolution nested models within a third, resulting in a lack of independence between these three. This is addressed here with 10 independent models from the major forecasting centers used for compositing. DMO forecasts, interpolated from these models to 14 moored buoy sites surrounding North America, provide the underlying component forecasts in the OCF composite. In addition to H s , the application of OCF techniques to the peak period ( T p

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Melissa S. Bukovsky, John S. Kain, and Michael E. Baldwin

and elsewhere, there has been a compelling interest in trying to identify and understand beneficial and misleading characteristic behaviors in the models. For example, Baldwin et al. (2002) showed that unrealistic vertical structures are often apparent in model output soundings from the Eta Model [ Black (1994) ; now called the North American Mesoscale (NAM) model]. Identification of these structures can help forecasters to make more informed assessments about the reliability of certain aspects

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Akira Yamazaki, Takemasa Miyoshi, Jun Inoue, Takeshi Enomoto, and Nobumasa Komori

nonbeneficial ones seem to be concentrated in the midlatitudes, because standard deviations of Δ E exp 2 ⁡ ( t ) against the 91-time forecasts have peaks around the midlatitudes, regardless of the latitudinal bands of data denial ( Figs. 11d–f ). When comparing the standard-deviation maps of the Mid4 and Tro experiments, the amplified regions seem to concentrate over the westerlies, including the Pacific, North America, and the Atlantic, where the Northern Hemisphere storm tracks are active (e

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