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Robert Rogers

environmental, vortex, and convective scales. Kaplan and DeMaria (2003) , using the Statistical Hurricane Intensity Prediction Scheme (SHIPS) database, identified several environmental conditions associated with RI: warm sea surface temperatures and deep oceanic mixed layers, high lower-tropospheric relative humidity, low vertical shear, weak upper-level forcing from troughs or cold lows, and upper-level easterly flow. These findings are consistent with what has been found by previous observational and

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Oreste Reale, William K. Lau, Kyu-Myong Kim, and Eugenia Brin

important to emphasize that the processes of cyclogenesis and cyclogenesis suppression should be studied from different perspectives, and global models do have two unquestionable advantages: 1) they are better at capturing the large-scale forcings involved, and 2) do not rely upon the somewhat questionable boundary conditions imposed on the domain’s boundaries of limited-area models. Among the large-scale problems connected with Atlantic tropical cyclogenesis, one of the most debated is the role of the

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Chanh Q. Kieu and Da-Lin Zhang

equations are kept the same as in CTL. This experiment will help elucidate the relative importance of the frictional convergence versus the surface heat exchange in the genesis of Eugene. To minimize any imbalance from an abrupt removal of the frictional forcing prior to the vortex merger, the PBL frictional effects are gradually reduced, starting from 18 h into the integration, by multiplying a factor μ = e − αt to the total PBL frictional forcing, where α is the inverse of an e -folding time

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Robert Cifelli, Timothy Lang, Steven A. Rutledge, Nick Guy, Edward J. Zipser, Jon Zawislak, and Robert Holzworth

that the MCSs passed through multiple periods of generation and decay as the events traversed across the continent. In general, rainfall maxima occurred in proximity to high topography during late afternoon/evening hours, in phase with the maximum of solar insolation. A relative minimum in rainfall activity was observed near the Greenwich meridian, possibly due to the lack of forcing by elevated terrain in this region ( Laing et al. 2008 ). As discussed below, the relative position of the land

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John Molinari and David Vollaro

) . Consistent with Fig. 5 , upshear and downshear profiles were similar for relatively unsheared tropical cyclones. Most of the helicity was present in the lowest kilometer, where frictional forcing produces a veering of wind with height. For highly sheared tropical cyclones the picture differed dramatically. Downshear the mean helicity exceeded 100 m 2 s −2 in the boundary layer alone. Substantial positive helicity existed throughout the lowest 6 km, the same layer over which Fig. 5 showed an upward

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Chanh Q. Kieu and Da-Lin Zhang

“eyewall” as seen from the radar reflectivity, strong thermal gradients across the eyewall, RMW, and spiral rainbands. It is found that strong VWS associated with the midlevel jet could also force the storm to tilt downshear and produce typical wavenumber-1 rainfall structures during the genesis stage, which are similar to those found in hurricanes. In addition, VWS has a thermodynamical impact on the upshear generation of moist downdrafts in the vicinity of the eyewall as a result of dry air intrusion

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Chuntao Liu, Earle R. Williams, Edward J. Zipser, and Gary Burns

hypothesis after many subsequent years of thunderstorm investigation, Wilson (1920 , p. 112) gave equal attention to thunderclouds and electrified shower clouds as “batteries” for the global circuit. In his words: “A thundercloud or shower-cloud is the seat of the electromotive force which must cause a current to flow through the cloud between the earth’s surface and the upper atmosphere … In shower-clouds in which the potentials fall short of what is required to produce lightning discharges, there is

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Andrew J. Heymsfield, Aaron Bansemer, Gerald Heymsfield, and Alexandre O. Fierro

1. Introduction Cirrus clouds at a given time cover about 20% of tropical latitudes and contribute significantly to regional and global radiation budgets ( Rossow and Schiffer 1999 ). Optically thick tropical cirrus are produced primarily through deep convection and generate as much as 25% of the earth’s net cloud radiative forcing ( Hartmann et al. 1992 ). The primary impact of thin versus thick cirrus is on the shortwave energy budget, and the albedo of these ice clouds depends on their

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Gerald M. Heymsfield, Lin Tian, Andrew J. Heymsfield, Lihua Li, and Stephen Guimond

environmental conditions, which are often a function of geographic location and season, would greatly affect the updraft characteristics in deep convection, leading to a variety of characteristics. The convective storm environment deduced from soundings [e.g., convective available potential energy (CAPE) and vertical wind shear] and low-level forcing can be drastically different, leading to different attributes of convection (e.g., Lucas et al. 1994a ; Johnson et al. 2005 ; May and Rajopadhyaya 1999

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