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Kevin Gray and Jeffrey Frame

1. Introduction a. Event overview A tornado outbreak caught many meteorologists by surprise on 24 August 2016 when storms produced 26 confirmed tornadoes across portions of Indiana, Ohio, and Ontario. Many convection-allowing models initialized that morning did not depict discrete storms or significant updraft helicity swaths across the affected area, but instead indicated that a line of storms would form, contributing to this challenging forecast. This event is also of interest because while a

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Bradley R. Carlberg, William A. Gallus Jr., and Kristie J. Franz

thought of as a fully independent sample, as synoptic or mesoscale conditions can favor a particular mode, causing possible cross-member correlation in some forecasts. Forecasts produced higher relative frequencies than were observed for IC, NS, and NL, and lower relative frequencies than were observed for the remaining five convective modes (CC, BL, TS, PS, and BE) ( Fig. 3 ). In addition, results for IC, NS, TS, and BE were similar to those in SG14 in which 115 observed convective modes and 109

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David Siuta, Gregory West, Henryk Modzelewski, Roland Schigas, and Roland Stull

. B. , 2003 : Implementation of Noah land surface model advances in the National Centers for Environmental Prediction operational mesoscale Eta Model . J. Geophys. Res. , 108 , 8851 , doi: 10.1029/2002JD003296 . Google , 2016 : Google compute engine pricing. [Available online at https://cloud.google.com/compute/pricing .] Grimit, E. P. , and Mass C. F. , 2002 : Initial results of a mesoscale short-range ensemble forecasting system over the Pacific Northwest . Wea. Forecasting , 17

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Alexandra K. Anderson-Frey, Yvette P. Richardson, Andrew R. Dean, Richard L. Thompson, and Bryan T. Smith

improved the final manuscript. This work has benefited tremendously from helpful discussions with Martin Tingley, Israel Jirak, Russ Schneider, Richard Grumm, the forecasters at the NWS State College Weather Forecast Office, Steven Weiss, Bill Bunting, Roger Edwards, and Paul Markowski, as well as the mesoscale research group at The Pennsylvania State University. AKAF is supported through NSERC Postgraduate Scholarship PGSD3-462554-2012 and YPR’s time is supported by a NOAA CSTAR Program Award NA14NWS

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Roger Edwards, Andrew R. Dean, Richard L. Thompson, and Bryan T. Smith

. Andra, D. L., Jr ., 1997 : The origin and evolution of the WSR-88D mesocyclone recognition nomogram. Preprints, 28th Conf. on Radar Meteorology, Austin, TX, Amer. Meteor. Soc., 364–365 . Baker, A. K. , Parker M. D. , and Eastin M. D. , 2009 : Environmental ingredients for supercells and tornadoes within Hurricane Ivan . Wea. Forecasting , 24 , 223 – 243 . Barnes, G. M. , Zipser E. J. , Jorgensen D. , and Marks F. Jr ., 1983 : Mesoscale and convective structure of a

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Yuxuan Yang, Lifeng Zhang, Bin Zhang, Wei You, Mingyang Zhang, and Binpeng Xie

1. Introduction The chaotic nature of the atmosphere means that minor deviations of the initial fields in numerical predictions lead to dramatic changes in the evolution of the simulated atmospheric system ( Lorenz 1963 ). With the gradual improvement of numerical models, the quality of the initial fields has played an increasingly important role in improving the accuracy of numerical weather forecasts. To provide more accurate initial fields, the introduction of nontraditional data (including

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Thomas E. Workoff, David A. R. Kristovich, Neil F. Laird, Robert LaPlante, and Daniel Leins

the lakes and their associated overlake boundary layers (OLBLs) 1 affect preexisting deep convective storms, particularly during the warm season where the water surface is predominately cooler than the surrounding land. To develop better forecasting techniques for areas in western lower Michigan, Graham et al. (2004) constructed a 5-yr climatology of the behavior of severe mesoscale convective systems (MCSs) crossing Lake Michigan. They found that MCSs responded variably to passing over the

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Zhan Li and Zhaoxia Pu

challenging problem (e.g., Hennon and Hobgood 2003 ; Kerns et al. 2008 ; Thatcher and Pu 2013 ). Previous studies have shown that initial conditions have substantial impacts on the numerical prediction of tropical cyclone genesis (e.g., Davis and Bosart 2002 ; Kieu and Zhang 2010 ; Pu and Zhang 2010 ). In light of previous findings, we perform numerical simulations of the genesis of Typhoon Nuri (2008) with the mesoscale community Weather Research and Forecasting (WRF) Model using initial and

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Tran Tan Tien, Dao Nguyen-Quynh Hoa, Cong Thanh, and Chanh Kieu

1. Introduction Predicting tropical cyclone (TC) formation is one of the essential missions in current operational TC centers. While it is of practical importance, reliable forecast of TC formation has been difficult to accomplish so far due to our incomplete understanding of multiscale interaction of TCs with the ambient environment (e.g., Harr et al. 1996 ; Simpson et al. 1997 ; Halverson et al. 2007 , Kieu and Zhang 2008 , 2009 ; Wang et al. 2019 ). Despite great achievements in

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Keith D. Sherburn, Matthew D. Parker, Jessica R. King, and Gary M. Lackmann

), and the North American Mesoscale (NAM; 12-km horizontal grid spacing), and Rapid Refresh (RAP; 13-km horizontal grid spacing) models, for an HSLC event on 30 January 2013. For this case, 6-h forecasts valid at 0600 UTC 30 January 2013 show enhanced MOSH values focused over a smaller area than SHERBS3 (cf. Figs. 19 and 20 ), consistent with the NARR event composites. The corridors of enhanced MOSH values do vary somewhat more than those of the SHERBS3 values based upon the chosen analysis

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