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Robin L. Tanamachi, Wayne F. Feltz, and Ming Xue

observed surface wind shift (from southerly to northerly winds) and pressure jump line associated with the outflow boundary ( Fig. 5 ), the speed of the outflow boundary as it approached the Homestead site (between 1100 and 1400 UTC) was approximately 11 m s −1 . This figure is within 10% of the theoretical speed of a density current with a 6-K difference of potential temperature ( θ ) and a depth of 250 m (quantities derived from the AERI θ data, Fig. 1 , to be further discussed in the next section

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Roger M. Wakimoto and Hanne V. Murphey

a one location along the thin line. As a result, the life cycle and the along-boundary variability could not be accurately assessed. Marquis et al. (2007) examined the kinematic structure of several boundaries but focused on the characteristics of mesocyclones using ground-based dual-Doppler analysis. Miao and Geerts (2007) examined the vertical structure of drylines primarily based on the analysis of data collected by the Wyoming King Air. The current study presents airborne dual

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Roger M. Wakimoto and Hanne V. Murphey

baroclinic disturbances that are well predicted by numerical forecast models. Fortunately, there have been important advances in warm season forecasting with the recognition that there is a strong relationship between convergence lines (e.g., synoptic-scale fronts, drylines, gust fronts, and sea-breeze fronts) that develop within the boundary layer and convection initiation (e.g., Purdom 1982 ; Wilson and Schreiber 1986 ; Wilson and Mueller 1993 ). While these studies have led to major improvements in

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Steven E. Koch, Wayne Feltz, Frédéric Fabry, Mariusz Pagowski, Bart Geerts, Kristopher M. Bedka, David O. Miller, and James W. Wilson

1. Introduction One of the coordinated research objectives of the International H 2 O Project (IHOP), which occurred from 13 May to 25 June 2002 in the southern Great Plains of the United States, was to seek to improve understanding of the relationship between water vapor and processes occurring in the surface and boundary layers that might have a bearing on convective initiation ( Weckwerth et al. 2004 ). Density currents and bores are lower-tropospheric phenomena that have a proven capability

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John H. Marsham, Stanley B. Trier, Tammy M. Weckwerth, and James W. Wilson

1. Introduction Nocturnal convective storms in the United States are poorly forecast compared with convection during the day ( Davis et al. 2003 ). One aspect of nocturnal warm-season precipitation that contributes to the difficulty of its prediction is the greater occurrence of elevated convection at night (e.g., Wilson and Roberts 2006 ). Here, we refer to convection where the conditionally unstable source air is located above the boundary layer as “elevated” ( Glickman 2000

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Margaret A. LeMone, Fei Chen, Mukul Tewari, Jimy Dudhia, Bart Geerts, Qun Miao, Richard L. Coulter, and Robert L. Grossman

1. Introduction This paper is the second of a two-part series that uses a combination of numerical simulations and observations to explore the relationship of surface heterogeneity and associated fluxes (W m −2 ) of sensible heat H and latent heat (LE), to potential temperature Θ (K), mixing ratio Q (g kg −1 ), depth, and convective structure on scales from 1 to 100 km in the fair-weather convective boundary layer (CBL), while evaluating the numerical simulations. The

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S. B. Trier, F. Chen, K. W. Manning, M. A. LeMone, and C. A. Davis

gradient of soil wetness was also found by Bosilovich and Sun (1999) to influence circulations in the 1993 flood case. However, in their simulations its primary role was to impact the meridional LLJ strength. In the current case we find little difference among simulations at the southern boundary of the east subdomain ( Fig. 8h ) and only small differences of up to 2 m s −1 at the southern boundary of the west subdomain ( Fig. 8g ). Unlike in Paegle et al. (1996) , the magnitude of the diurnal

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John R. Mecikalski, Kristopher M. Bedka, Simon J. Paech, and Leslie A. Litten

well as a physical interpretation, are provided in Table 1 . For 2004–06, the MB06 algorithm has been transitioned from a “proof of concept” into a real-time product, one designed for use in broader applications over larger domains. These applications include, in addition to 0–1-h day and night CI nowcasting at 1 km-resolution, CI climatological applications, 0–90-min lightning initiation nowcasting, delineation of surface convergent boundaries (Jay Hanna, NOAA, 2005, personal communication

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Margaret A. LeMone, Mukul Tewari, Fei Chen, Joseph G. Alfieri, and Dev Niyogi

data from the International H 2 O Project (IHOP_2002; Weckwerth et al. 2004 ; LeMone et al. 2007a ) and the 1997 Cooperative Atmosphere–Surface Exchange Study (CASES-97; LeMone et al. 2000 ). Here we focus on the more sparsely vegetated IHOP_2002 western track, located in the Oklahoma Panhandle. IHOP_2002 was organized to improve prediction of warm-season precipitation; the surface and boundary layer component looked at how surface processes affect the planetary boundary layer (PBL) and

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