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R. A. Dare and W. F. Budd

used as representatives of summer and winter, respectively. 2. Midtropospheric forcing of the surface wind Streten (1990) showed that the average winds at 500 hPa over Mawson vary from strong westerlies during winter to relatively weak easterlies in the peak of summer. At the surface, however, analysis of observations at Mawson ( Fig. 2 shows that the prevailing wind direction is close to slightly east of southeast throughout the year, similar to that found by Phillpot (1967) . During winter the

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Andrew C. Winters and Jonathan E. Martin

aims to 1) quantify the contribution to the poleward moisture flux made by the superposed jet’s ageostrophic circulation and 2) examine the impact that both geostrophic and diabatic forcing may have had in determining the strength and sense of the overall ageostrophic circulation. The remainder of this study is organized as follows. Section 2 gives an overview of the methodology used to identify superposed jets as well as background on the Sawyer–Eliassen circulation equation. Section 3

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David J. Stensrud, Geoffrey S. Manikin, Eric Rogers, and Kenneth E. Mitchell

and specific humidity based upon typical profiles determined from observational studies ( Betts 1986 ). These profiles are then adjusted to satisfy a total enthalpy constraint.In general, the Betts–Miller–Janjic scheme is designed to respond well to sustained large-scale forcing in the presence of conditional instability and it is not likely to fail egregiously (see Kain et al. 1998 ). The scheme is not designed, however, to respond quickly to regions of strong mesoscale forcing, such as a cold

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Kenneth A. James, David J. Stensrud, and Nusrat Yussouf

-scale forcing for upward motion ( Jankov and Gallus 2004 ). Subgrid-scale parameterization schemes, such as radiation, ice microphysics, and vertical diffusion, also are found to significantly modulate the characteristics of explicitly forecast convection that can be important to forecast operations ( Weisman et al. 1997 ). These results raise important questions regarding the use of high-resolution models to provide improved forecasts of severe convective storms. In contrast, Fowle and Roebber (2003

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Thomas L. Black

) the propagationof a strong cold front where the forcing was primarily internal and not orographic; and (ii) a rainfall event wherethe forcing arose from the interaction of topography with the synoptic-scale flow.1. Introduction As computer technology continues to improve, andthe quantity and quality of atmospheric observationsincrease, the generation of mesoscale forecast guidanceover the United States in an operational mode is becoming increasingly feasible. Providing such guidanceis the goal

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Jerome Namias

circulationand weather pattern in 1987 following a spring that had much different characteristics. Since the forecast forthis pattern was successful, the main reasons for the evolution are detailed. Essentially, these involve the probableinfluences of factors associated with change in season (seasonal forcing) and some new ideas as to how toincorporate these changes objectively.1. Introduction One of the important procedures of a long-rangeforecasting program involves routine postmortems,which attempt to

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Michael L. Jurewicz Sr. and Michael S. Evans

1. Introduction Numerous studies have been carried out on favorable environments for the development of intense, small-scale (widths of 5–40 km) bands of heavy snow within relatively large (100–500 km wide) regions of light to moderate stratiform snow (e.g., Martin 1998a , b ; Nicosia and Grumm 1999 ; Schultz and Schumacher 1999 ; Clark et al. 2002 ). These types of bands typically form in regions of strong, large-scale forcing for upward motion, within the upward branch of a thermally

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William P. O’Connor, David J. Schwab, and Gregory A. Lang

forecasting system must have two components: an ocean model to predict the state of the coastal ocean, and meteorological input to this ocean model. The ocean model may be a two-dimensional or three-dimensional hydrodynamic model and/or a wind wave model. In turn, the ocean model requires accurate meteorological forcing data as input over the duration of the simulation. The output of numerical mesoscale atmospheric models can be used as forcing for the ocean model, because observed data may not be

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David J. Stensrud, John V. Cortinas Jr., and Harold E. Brooks

always sufficient. While July and Johns (1993) show that forecasters from the severe local storms unit of the National Severe Storms Foreast Center have shown considerable skill in forecasting severe weather outbreaks associated with strong large-scale forcing for upward motion (termed synoptically evident outbreaks), Johns and Hart (1993) show that differentiating between outbreaks that produce mostly bow echoes and widespread damaging wind reports, and those that produce mostly supercell

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Molly B. Smith, Ryan D. Torn, Kristen L. Corbosiero, and Philip Pegion

the storm center ( Atallah and Bosart 2003 ), where frontogenesis (and quasigeostrophic forcing for ascent) occurs. Cold-air advection (CAA), meanwhile, entrains dry air to the west, which reduces convection in the storm core, causing the eyewall to dissipate. The net effect of ET on a TC’s rainfall patterns, therefore, is to shift the heaviest precipitation outside of the storm core, toward the region of maximum baroclinicity. One of the reasons that TCs undergo the aforementioned transition is

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