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Seth Saslo and Steven J. Greybush

increases at increasingly longer lead times, so too should ensemble spread increase with forecast hour. Quantitative precipitation forecast (QPF) performance is evaluated using both point and gridded observations. The NCEP/Environmental Modeling Center (EMC) Stage IV multisensor precipitation analysis ( Lin and Mitchell 2005 ) is used for storm-total QPF evaluation across the spatial domain. Stage IV has limitations owing to the shallow depth of LES and poor detection of low levels from the local

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Daniel T. Eipper, George S. Young, Steven J. Greybush, Seth Saslo, Todd D. Sikora, and Richard D. Clark

evaluated each model’s robustness by testing it on independent data, using a block version of leave-one-out cross validation ( Zhang 1993 ; Wilks 2006 ). LLAP-band snapshots were first grouped into 10 blocks, such that each LLAP-band block was separated by at least 24 h from every other block (in contrast to the 6-h minimum separation between snapshots). This process was used to separate groups of snapshots that occurred during distinct synoptic events, recognizing that individual synoptic events could

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Philip T. Bergmaier, Bart Geerts, Leah S. Campbell, and W. James Steenburgh

) campaign. Steenburgh and Campbell (2017) show high-resolution model data indicating that the broader LLAP system during IOP2b formed along a shallow convergence zone associated with a land-breeze front that developed along a bulge in the southern shoreline and extended downstream over eastern Lake Ontario. This study focuses on <1 h of airborne radar observations from when the LLAP system had organized into a well-defined, narrow, steady, and deep LLAP band that extended over the eastern end of the

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Peter G. Veals, W. James Steenburgh, and Leah S. Campbell

higher probability of convective initiation, stronger updrafts, and higher LPE rates, though this has not been evaluated explicitly ( Niziol 1987 ; Hjelmfelt 1990 ; Niziol et al. 1995 ). Lake-effect convection frequently assumes the mode of disorganized open cells or horizontal roll convection, referred to collectively as broad coverage in some studies ( Hjelmfelt 1990 ; Steenburgh et al. 2000 ; Veals and Steenburgh 2015 ; Campbell et al. 2016 ). The likelihood of roll convection increases with

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Justin R. Minder, Theodore W. Letcher, Leah S. Campbell, Peter G. Veals, and W. James Steenburgh

, we are motivated to better understand these mechanisms, both as a fundamental science question regarding the response of shallow convection to surface forcing, and also to aid in the critical evaluation of conceptual and numerical models used to forecast these high-impact storms. Here, we focus specifically on how convective clouds evolve as they transition onto land and rise over Tug Hill. Our primary observations come from an east–west transect (black dots in Fig. 1b ) of four vertically

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Peter G. Veals and W. James Steenburgh

frequency near Mexico Bay that broadens inland and over Tug Hill ( Fig. 20b ). Although this strip may seem a bit south of that expected based on conceptual models showing convergent land breezes meeting in the center of the lake (e.g., LaDue 1996 ), the southern shoreline near Mexico Bay actually lies closer to the central axis of Lake Ontario as a whole. Nevertheless, further work is needed to fully elucidate the causes of the high frequency of echoes during LLAP events near Mexico Bay. Fig . 20

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