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Wei Sun, Rucong Yu, Jian Li, and Weihua Yuan

, the 200-hPa zonal wind U 200 in the Inner Mongolia region (to the north of CNC) has a high positive correlation with heavy rainfall amounts in CNC ( Fig. 2a ), implying that the strengthening of the high-level westerly jet could increase the rainfall amount to its south ( Cunningham and Keyser 2000 ; Shi et al. 2010 ). Meanwhile, the 700-hPa geopotential height H 700 to the west of 110°E has a significant negative correlation with heavy rainfall amounts in CNC ( Fig. 2b ), suggesting that the

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Joshua M. Boustead, Barbara E. Mayes, William Gargan, Jared L. Leighton, George Phillips, and Philip N. Schumacher

tornadoes. In addition to identifying favorable patterns, M72 also developed a composite checklist forecasters could use operationally to recognize the occurrence of these patterns. The checklist included elements such as moisture, stability, forcing for ascent, jet streaks, and a source of dry air aloft. The M72 checklist gave values that were classified as weak, moderate, or strong. Not always directly related to tornado forecasting, the presence of an upper-level jet has been long associated with

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Crystalyne R. Pettet and Richard H. Johnson

-level southerly jet was located atop the inversion. The sounding behind the LS system at Aberdeen, South Dakota (ABR, Fig. 3b ) shows nearly saturated conditions from 800 to 500 hPa. A strong capping inversion appears between 880 and 850 hPa. Surface parcels have no buoyancy in either sounding; therefore, convection was likely elevated. Both of these soundings indicate a southerly low-level wind that generally veers with height to southwesterly in the mid- to upper troposphere, suggestive of warm advection

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Philip N. Schumacher, Gregory Frosig, Jason L. Selzler, and Robert A. Weisman

from warm-air advection to the east. Significant frontogenesis was associated with the traditional warm front, which extended east of the cyclone center. In the upper troposphere, a jet streak was located near the surface low with the left exit region of the jet located over quadrant A. Therefore, most of the ascent and precipitation occurred in quadrant A. For behind cases, the low-level baroclinicity reoriented itself roughly along and behind the IT producing a frontogenesis maximum. Stronger

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Lawrence B. Dunn and John D. Horel

May 1994) ABSTRACT Outpui from simulations of the Eta model are compared to special observations collected during the 1990Southwest Area Monsoon Project (SWAMP). The emphasis is on the model's prediction of the preconvectionair mass over Phoenix, Arizona, and on the model's representation of the low-level jet and moisture surgeobserved over southwest Arizona. At times the model fails to capture the rapid increase in low- and mid-level moisture that is observed in thehours

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Steven R. Silberberg

stationary, a gusty mesoscale surface jet formed locally overnortheastern Wisconsin and propagated to the south-central part of the state. The surface jet forced a sustainedregion of surface convergence and ascent that was maximized over south-central Wisconsin during the periodof greatest snowfall. The roles of heat and moisture fluxes from the Great Lakes in producing a neutrally buoyantlayer of surface northeasterly flow northeast of the surface cyclone and the redistribution of mass around

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Someshwar Das, A. K. Mitra, G. R. Iyengar, and J. Singh

stability of the mean state, particularly in the Tropics. The simulated variability of climate from diurnal to intraseasonal scales is also affected by the inadequacies in the convective parameterization schemes. The strengthening of the Somali jet during the monsoon in the National Centers for Environmental Prediction (NCEP) model ( White et al. 2000 ) and the typical features of the Indian summer monsoon such as the cross-equatorial flow, the low-level jet, the upper-level tropical easterly jet, and

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Kenneth D. LaPenta, Lance F. Bosart, Thomas J. Galarneau Jr., and Michael J. Dickinson

northward across the Gulf of Alaska, eastward toward Greenland, and over much of the southern half of the United States ( Fig. 3 ). Below normal heights were found west of California and over Canada to the south of Hudson Bay. Given the strong trough (ridge) south of Hudson Bay (over the southern United States), the pattern shown in Fig. 3 was conducive to a strong westerly jet from the northern Rockies to New England. The severe weather threat was maximized where the ascent zones associated with

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Russell L. Elsberry and Peter J. Kirchoffer

regionsduring FGGE is examined. Potential vorticity and jet streak properties are derived from analyses prepared bythe European Centre for Medium-Range Weather Forecasts. The vertical and horizontal resolution of thearchived analyses are not adequate to depict the tropopause folding and downward transport of potential vorticitythought by some investigators to be important in explosive cyclogenesis. Thus, the emphasis is put on therelative maxima in potential vorticity that are present at 300 mb upstream of

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David M. Gaffin and Stephen S. Parker

tornadic environments ( Johns and Doswell 1992 ; Rose et al. 2004 ) that involve examination of such fields as surface and 850-hPa dewpoints, the tilt of the 500-hPa troughs, and the quadrant of the 250-hPa jet streaks (in relation to the southern Appalachian region) will be investigated. Finally, composite maps of significant tornado events will be compared with those of weak tornado events to determine the synoptic-scale characteristics associated with significant tornado events. 2. Methodology and

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