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Xiaodong Hong, Craig H. Bishop, Teddy Holt, and Larry O’Neill

of Taiwan and flowing northeastward past Japan. The Kuroshio Extension is the eastward continuation of the Kuroshio, a free jet leaving the Japanese coast and entering the open basin of the North Pacific ( Sverdrup et al. 1942 ; Kawai 1972 ). The mean circulation feature of the Kuroshio Extension has been presented using the sea surface dynamic height maps constructed from historical hydrographic data (e.g., Wyrtki 1975 ; Qu et al. 2001 ). There is high mesoscale anticyclonic and cyclonic eddy

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Nicholas J. Weber, Matthew A. Lazzara, Linda M. Keller, and John J. Cassano

the mountains builds high pressure along the range, as is evident in the ridging of the isohypses ( O’Connor et al. 1994 ), which geostrophically forces a jet—or barrier wind—along the edge of the ice shelf toward Ross Island. The ground-level isotachs support this idea, revealing a jet along the Transantarctic Mountains ( Fig. 8d ) with a maximum average wind speed of roughly 20 m s −1 in the Ross Island vicinity. ERA-Interim composites of the 500-hPa height field and mean sea level pressure

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R. Fehlmann, C. Quadri, and H. C. Davies

is some indication of nonconservation of PV in the 24-h period between the two panels of Fig. 2 . At the surface and ahead of the trough a meridionally aligned front traversed slowly over western Europe and approached the western rim of the Alps early on 5 November ( Fig. 3 ). The front was coaligned with the upper-level filament and a weak frontal wave evolved over central France. Ahead of the front a low-level jet provided sustained flux of moisture onshore off the Gulf of Genoa from circa

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John M. Lanicci and Thomas T. Warner

polar jet has relreated northward. We define a four-phase composite of the chronology of the lid cycle..Analyses of composited synoptic-flow types to represent the various stages in each type of lid cycle are presented,and we examine several of these composites to identify geographically favored zones for initiation of deep convection.1. Introduction The elevated mixed-layer inversion, or lid, is an iraportant feature of the severe-storm environment overtbe central U.S. in spring and summer. The

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Louis A. Giordano and J. Michael Fritsch

northwest flow seldom affect the East Coast. For the most part, synoptic conditions during the strong convective events depart very little from the meansummertime conditions. Notable exceptions are 1) extremely high dewpoints in the surface-850-mb layer, and2) stronger low-level clockwise directional shear (mostly in the boundary layer) and helicity. It was also foundthat most events occur in proximity to an upper-level jet-stream maximum and/or a diffluence zone. The mean environmental conditions

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John A. Augustine and Fernando Caracena

-troposphericenvironments that indicate the expected location and degree of nocturnal mesoscale convective system (MCS)development over the central United States. The authors concentrate on two features: 1 ) the forcing for thelow-level jet (LLJ), and 2) the frontogenetic character of lower-tropospheric fronts, or other types of airmassboundaries, with which MCSs are associated. Results show that very large, long-lived, nocturnal MCSs are likelyto mature downwind of a late afternoon surface geostrophic wind maximum if that

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Christopher M. Bailey, Gail Hartfield, Gary M. Lackmann, Kermit Keeter, and Scott Sharp

classical CAD (CDEN) By convention, classical CAD events must exhibit a parent high that is strong (central pressure > 1030 mb) and favorably located to the north of the Appalachian damming region. Precipitation must be observed at one or more of the stations in the central damming region within 6 h of CAD onset. The sequence of composites for the 19-case cold-season CDEN sample is presented in Figs. 6 – 8 . At 24 h prior to the onset of CAD, a prominent 250-mb jet extends from southwest to northeast

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Yijia Hu, Yimin Zhu, Zhong Zhong, and Yao Ha

also is accompanied by the arrival of the leading edge of the East Asian summer monsoon (EASM) in the region, the jump of the western Pacific subtropical high (WPSH) axis to the north of 20°N, the stabilized WPSH axis within 20°–25°N, and the northward migration of the upper-level westerly jet over Eurasia to the north of the Tibetan Plateau ( Tao and Chen, 1987 ; Li and Yanai, 1996 ; Ding 1992 ; Ding et al. 2007 ). Therefore, the atmospheric circulation patterns in the years with early MODs

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A. Philip, T. Bergot, Y. Bouteloup, and F. Bouyssel

the thermal inversion layer is stronger in HR ( Fig. 6 ), leading to stronger dynamical production of TKE. The TKE budget near the ground is dominated by the mean shear velocity, and the TKE at 10 m is stronger in HR than in LR (about 0.3 m 2 s −2 for HR against 0.23 m 2 s −2 for LR). Furthermore, in HR, significant advections are simulated within the surface boundary layer, with a maximum of about −0.4 K h −1 at the level of the low-level jet ( Fig. 5b ). This process is not simulated in LR

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Raymond H. Brady and Jeff S. Waldstreicher

passed across northeast Pennsylvania later in the day, was preceded by a large area of rain that extended from New England into the mid-Atlantic region. The 850-mb plot ( Fig. 3b ) depicted a 35–40 m s −1 (70–80 kt) southerly jet from northern Virginia across Pennsylvania and New York. This jet was also evident in the KBGM velocity azimuth display (VAD) wind profiles ( Fig. 4 ). Other than a gradual overall increase in velocity of between 2.5 and 5.0 m s −1 (5–10 kt), the wind profile below 3 km

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