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Michael Fiorino, James S. Goerss, Jack J. Jensen, and Edward J. Harrison Jr.

the western North Pacific. The evaluationwas conducted during the 1990 operational testing of a procedure to improve the initial analysis or specificationof tropical cyclones (TCs) in NOGAPS by the U.S. Navy Fleet Numerical Oceanography Center (FNOC). TheNOGAPS TC analysis procedure generates synthetic TC observations based on operational vortex data (e.g.,location and maximum surface wind speed) and then adds the observations to the observational data base withflags to force their assimilation

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John G. W. Kelley, David W. Behringer, H. Jean Thiebaux, and Bhavani Balasubramaniyan

Ocean Forecast System (COFS) for the U.S. East Coast. COFS was implemented experimentally at NCEP in August of 1993 ( Aikman et al. 1994 ; Aikman et al. 1996 ). From August of 1993 to March of 1998, COFS generated 24-h forecasts once per day for the northwest Atlantic Ocean with surface forcing provided by NCEP's operational eta-coordinate mesoscale atmospheric prediction model without oceanic data assimilation ( Fig. 1a ). Analyses of errors from these forecasts pointed out a need to modify the

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

updrafts and rotation. Jewett and Wilhelmson (2006) found that idealized simulations of environments with reduced CAPE and high shear did not produce intense, long-lasting convection in the absence of large-scale environmental forcing. Recent research has corroborated these findings, suggesting that cool season HSLC events in the Mississippi, Tennessee, and Ohio valleys, as well as the Southeast and mid-Atlantic regions, may rely more heavily on the synoptic environment than severe thunderstorms and

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

broad area of 850–500-hPa layer-averaged Q -vector convergence, forcing QG ascent, located west of CYOW and just downstream of a midtropospheric trough ( Fig. 4 ). By t = −6 h ( Fig. 3c ), CYOW is located in the center of the large area of Q -vector convergence, which has strengthened relative to t = −18 h ( Fig. 3a ). Simultaneously, a large low-level θ e gradient is present over the region, supporting the earlier assertion of an Arctic cold front approaching and subsequently moving through

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Joseph A. Rogash and Richard D. Smith

precipitation across the region. Wind and temperature fields suggest warm air advection is present along and just north of the boundary. As demonstrated by Maddox et al. (1980) , though such boundaries may be short lived and lack vertical continuity, they can play a critical role in initiating and forcing deep moist convection. Eta Model 6-h forecasts indicate little change in the large-scale upper-tropospheric weather pattern during the remainder of the morning hours ( Fig. 8a ); the trough–ridge system

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Xiaoyu Chen and Liguang Wu

over China’s mainland increased significantly during the period 1975–2009. The increasing overland duration resulted from both the decreasing translation speed on the interdecadal scale and the decreasing vertical wind shear. Duan and Wu (2008) demonstrated that the sensible heat (SH) flux over the Tibetan Plateau has exhibited a significant decreasing trend since the mid-1980s, mainly because of decreases in the surface wind speed. The weakening trend in the thermal forcing of the Tibetan

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Andy Taylor and Gary B. Brassington

1. Sea level anomalies and forecast narratives Many activities are organized around expectations of coastal water levels over the next few days, including mitigation of nuisance coastal flooding ( Sweet et al. 2014 ; Hague et al. 2019 ). Still water levels ( Pugh and Woodworth 2014 ) at the coast are not just a matter of tidal patterns and local storms, but can also be influenced by remote forcing via coastally trapped wave (CTW) mechanisms. While CTWs have received much academic attention

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Dongliang Wang, Xudong Liang, Ying Zhao, and Bin Wang

Research and Air Force Weather Agency (NCAR–AFWA; Low-Nam and Davis 2001 ) proposed a scheme (hereafter referred to as the N–A bogussing scheme) for bogussing TCs into the initial conditions of the nonhydrostatic version of the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5). The process they used to detect and extract the inaccurate vortex from the first-guess field distinguishes it from many other approaches. For example, Kurihara et al. (1993) used a sophisticated

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William R. Ryerson and Joshua P. Hacker

1. Introduction Reductions to visibility between the ranges 1 and 7 mi (1 mi = 1.6 km) due to fog are a significant safety concern for many aviation operations. Accurate visibility predictions in this range, hereafter termed light fog, are critical because they dictate restrictions on certain aircraft types and equipment, pilot level of experience, etc. Remote and sparsely observed regions, often of primary interest to the U.S. Air Force, provide a particularly challenging visibility prediction

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Jerome D. Fast

pressure gradient comprises two terms, of which both are large over steep slopes. It has been known for decades that an inconsistent discretization of these terms can fail to properly account for the partial compensation between them, producing large errors in the horizontal momentum equations ( Pielke 1984 ). A number of alternative approaches for calculating the pressure gradient force in the sigma coordinate have been proposed to minimize these errors (e.g., Carroll et al. 1987 ; Danard et al

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