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Kimberly L. Elmore, Heather M. Grams, Deanna Apps, and Heather D. Reeves

), sometimes resulting in a heterogeneous mix of various precipitation types. Precipitation-type forecasts in numerical models are typically performed by one or more postprocessing algorithms. Explicit algorithms use the predicted mixing ratios of snow, graupel, and rain in concert with vertical profiles of temperature to assign the type. The North American Mesoscale Forecast System (NAM; Janjic et al. 2005 ) uses an explicit scheme as part of a “mini-ensemble” of precipitation-type methods. The implicit

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Brian C. Ancell

.g., upper-level geopotential height troughs, or midlevel temperature gradients) that have dynamical relevance to the response function. The features shown to be most sensitive are those that must be accurate at early forecast times to well predict the chosen response function later in the forecast window. Figures 2 – 4 show an example of a 24-h forecast of a deepening cyclone (initialized 0000 UTC 19 November 2009) soon to make landfall on the west coast of North America and the ensemble sensitivity

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Rebecca E. Morss and F. Martin Ralph

1. Introduction Winter storms making landfall in western North America can produce heavy precipitation, strong winds, and other significant weather, with severity similar to that found in tropical storms (e.g., Ralph et al. 1999 ; McMurdie and Mass 2004 ; Neiman et al. 2004 ). The resulting flooding, landslides, and other hazards cause substantial damage, deaths, injuries, and economic disruption (e.g., NCDC 1993–2004 ; Ross and Lott 2003 ; NRC 2004 ). Improving forecasts of these storms

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Steven M. Lazarus, Samuel T. Wilson, Michael E. Splitt, and Gary A. Zarillo

resolved first-guess inner-core wind field. Using hindcasts, the parametric model is constructed and tuned with observations from the “extended best track” dataset ( DeMuth et al. 2006 ) and wind measurements from National Data Buoy Center (NDBC) buoys. A total of 12 Gulf of Mexico (GOM) TC events of varying intensities are examined. The data used to generate the wind analyses, the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) North American Regional

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J. Dustin Hux, Paul C. Knappenberger, Patrick J. Michaels, Philip J. Stenger, Hugh D. Cobb III, and Michael P. Rusnak

most difficult tasks in operational meteorology in North America. Indeed, Keeter et al. (1995) have written that “perhaps the most challenging winter weather forecast problem in the Southeast is forecasting precipitation type.” In the mid-Atlantic region, the onset of a winter precipitation event is often preceded by the formation of a cold anticyclone under a transient ridge that occurs in partial response to an upstream short wave passing through a longer wavelength trough ( Maglares et al

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Shih-Yu Wang and Adam J. Clark

handling planetary boundary layer evolution (e.g., Bukovsky et al. 2006 ; Coniglio et al. 2009 ). Further difficulties in forecasting warm-season precipitation in current operational NWP models such as the National Centers for Environmental Prediction (NCEP) North American Mesoscale Model (NAM; Janjić 2003 ) arise from the use of cumulus parameterization (CP), which is needed to depict the effects of subgrid-scale convective processes (e.g., Molinari and Dudek 1992 ). Specifically, previous works

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Hong Guan, Yuejian Zhu, Eric Sinsky, Wei Li, Xiaqiong Zhou, Dingchen Hou, Christopher Melhauser, and Richard Wobus

revealed the importance of a hindcast (i.e., reforecast) for extreme weather forecasts or bias correction during week 1 or week 2. Thus, the hybrid decaying and reforecast bias-correction method ( Guan et al. 2015 ) is being operationally applied to the North American Ensemble Forecast System (NAEFS; Candille 2009 ) in order to improve 1–16-day forecasts. The major focus of this study is to analyze the spatial and temporal distributions of 2-m temperature bias and identify the saturation

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Lionel Peyraud

1. Introduction While supercell thunderstorms tend to be most prevalent in North America east of the Rocky Mountains over predominantly flat terrain, almost all regions around the world support the development of these storms, albeit on a less frequent basis. Countries such as Argentina, Australia, and Bangladesh are among regions where supercells have been known to occur on a regular basis ( Held et al. 2005 ). Supercells also occur intermittently on the European continent. Synoptic conditions

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Israel L. Jirak and William R. Cotton

convection in mind to locate and identify initiating features. If the convection began near a feature that likely influenced its development, then that feature was recorded to be associated with the initial convection of the MCS. In the same manner, the initiating mechanisms for the cases of widespread convection were identified for comparison with the MCS triggers. The results of this subjective analysis are presented in section 4a . Data from the NCEP North American Regional Reanalysis (NARR) were

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William R. Burrows, Colin Price, and Laurence J. Wilson

1. Introduction The North American Lightning Detection Network (NALDN) provides continuous lightning detection over Canada and the contiguous United States and near offshore to about 65°N in the northwest and 55°N in the northeast. Locations of detectors are listed in Orville et al. (2002) . The Meteorological Service of Canada (MSC) receives lightning flash reports for Canada and the northern United States to 35°N east of 100°W and to 40°N west of 100°W. Network detection efficiency of cloud

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