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Jared A. Rackley and John A. Knox

barrier ( Smith 1982 ). This weakens the northward-directed component of the Coriolis force and the flow turns to the south and accelerates in response to the now-unbalanced pressure gradient force. As the ageostrophic northerly flow accelerates, the Coriolis force strengthens once again and acts to deflect the flow in a toward-barrier direction, causing both an accumulation of mass and orographic ascent along the eastern Appalachian slopes. The mass accumulation and adiabatic cooling due to the

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James T. Moore, Charles E. Graves, Sam Ng, and Jamie L. Smith

has been previously documented in the plains (e.g., Cissell and Marwitz 1998 ). Banacos (2003) has noted that the spatial location and duration of these heavy snowbands is often difficult to predict accurately. The challenge of this heavy snow event is to explain the length and breadth of the heavy snowfall as well as thundersnow in the presence of a weak surface cyclone. Toward that end, this paper examines the processes that help to force and focus this narrow region of heavy snowfall, while

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Riccardo Mel and Piero Lionello

forecast over a longer time range, and their accuracy is determined mostly by their spatial resolution and by the quality of the forcing meteorological fields. While, in general, for hourly sea level a hydrodynamical model has a lower bias than a model based on the statistical autoregressive approach, the latter produces better results if only high storm surges are considered (see Table 1 ). However, hydrodynamic models provide information on SR along the whole coast (also where observations are not

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Frederick Sanders

maximum is a sufficient condition for explosive cyc!ogenesis. The results are not to be taken as a comprehensiveguide to the prediction of explosive cyclogenesis, inwhich factors other than the upper-level forcing needto be taken into account. In particular, we do not studythe static or slantwise stability of the environment ofthe incipient bomb, which is presumably responsiblefor the degree of response to the forcing. Nor have weattempted to evaluate the surface forecasts producedby operational

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Michael C. Coniglio, David J. Stensrud, and Michael B. Richman

) Upstream-trough pattern The upstream-trough pattern is formed from 91 cases (40.4%) that have a well-defined mobile upstream trough as the primary influence on the development of the DCS. The mean midlevel differential vorticity advection (estimated from the reanalysis data) is found to be 4–6 times larger for the upstream-trough events than for the ridge and zonal-flow events. Accordingly, these events best match Johns's (1993) strong-forcing/dynamic pattern and mostly exhibit characteristics of

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Paul J. Roebber, David M. Schultz, and Romualdo Romero

the afternoon (section 2b in TE ). By 0000 UTC 4 May, these winds were 10–15 m s –1 greater than forecast (Figs. 10 and 11 in TE ; Fig. 6 in E02 ). These winds could play three roles in the resulting convection. First, the incoming jet streak provides a forcing mechanism for upper-level synoptic-scale ascent and the development of cirrus, reducing insolation and slowing the removal of the low-level capping inversion. Second, the low-level synoptic-scale ascent associated with the jet streak

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Claudia K. Walters

discussed in relation to previous research. The major findings of Part I and Part II are summarized in section 6 . 2. Background Low-level wind maxima have been observed in a variety of synoptic settings. Increasingly, investigators are calling for a distinction to be made between spatially extensive wind maxima that appear to be related to synoptic-scale forcing and more localized wind maxima that are primarily controlled by boundary layer or lower-tropospheric forcing (e.g., Uccellini 1980 ; Chen

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Charles P. Guard, Lester E. Carr, Frank H. Wells, Richard A. Jeffries, Nicholas D. Gural, and Dianne K. Edson

, with emphasis on the aircraf~ reconnaissance era and the evolution of satellite reconnaissance. The joint Navy-Air Force Operations Evaluation to assess the impact of the loss of aircraft reconnaissance and the Office of Naval Research Tropical Cyclone Motion-90 Experiment are briefly discussed.Finally, the paper takes a cursory look at JTWC's postanalysis program, which includes the Annual TropicalCyclone Report; training, qualification, and certification programs; and technique development to

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Steve Keighton, Douglas K. Miller, David Hotz, Patrick D. Moore, L. Baker Perry, Laurence G. Lee, and Daniel T. Martin

transitioning to a typical NWFS scenario with shallow moisture and dominant orographic influences on the back side of the storm. The variety of evolutions resulting in NWFS events will be discussed in more detail in section 2 . Given that the Sandy snowfall totals (and especially the liquid equivalent measurements) were more extreme than with typical NWFS events, this study investigates specifically how and why the synoptic evolution, forcing mechanisms, moisture characteristics and sources, wind, and

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Seung-Eon Lee and Kyong-Hwan Seo

and July. In Fig. 1 , a zonally elongated rainband can be seen in the EASM region (25°–40°N) and the rainfall maximum appears over the Korean Peninsula and southern Japan. The rainband moves gradually northward into North Korea in August. This general movement can be modified by a variety of external forcing factors ( Lau et al. 2000 ), such as variation in sea surface temperatures (SSTs; Wang et al. 2000 ; Kim et al. 2009 ; Xie et al. 2009 ). Fig . 1. Climatological mean precipitation data

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