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David M. Schultz and Joseph M. Sienkiewicz

1. Introduction Extreme winds in extratropical cyclones often occur south of the surface low center (e.g., Lynott and Cramer 1966 ; Neiman et al. 1993 ; Grønås 1995 ; Steenburgh and Mass 1996 ; Nielsen and Sass 2003 ; Von Ahn et al. 2006 ; Chelton et al. 2006 ; Knox et al. 2011 ; Fox et al. 2012 ; Hanafin et al. 2012 ). Studying the United Kingdom's Great Storm of 15–16 October 1987, Browning (2004) coined the term sting jet to refer to one specific type of wind maximum in this

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Oscar Martínez-Alvarado, Laura H. Baker, Suzanne L. Gray, John Methven, and Robert S. Plant

Hemisphere Shapiro–Keyser cyclone in development stage 3: surface cold front (SCF); surface warm front (SWF); bent-back front (BBF); cold conveyor belt (CCB); sting jet airstream (SJ); dry intrusion (DI); warm conveyor belt (WCB); WCB anticyclonic branch (WCB1); WCB cyclonic branch (WCB2); and the large × represents the cyclone center at the surface, and the gray shading represents cloud top (see also Fig. 2 ). There are two separate regions usually associated with strong winds in Shapiro

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G. Vaughan, J. Methven, D. Anderson, B. Antonescu, L. Baker, T. P. Baker, S. P. Ballard, K. N. Bower, P. R. A. Brown, J. Chagnon, T. W. Choularton, J. Chylik, P. J. Connolly, P. A. Cook, R. J. Cotton, J. Crosier, C. Dearden, J. R. Dorsey, T. H. A. Frame, M. W. Gallagher, M. Goodliff, S. L. Gray, B. J. Harvey, P. Knippertz, H. W. Lean, D. Li, G. Lloyd, O. Martínez–Alvarado, J. Nicol, J. Norris, E. Öström, J. Owen, D. J. Parker, R. S. Plant, I. A. Renfrew, N. M. Roberts, P. Rosenberg, A. C. Rudd, D. M. Schultz, J. P. Taylor, T. Trzeciak, R. Tubbs, A. K. Vance, P. J. van Leeuwen, A. Wellpott, and A. Woolley

physics background can be vital to access university teaching of these subjects and, more importantly, to develop the skills usually required for a career in the field. THE NORTH ATLANTIC WEATHER REGIME OF EARLY WINTER 2011/12. The second DIAMET aircraft campaign (24 November–14 December 2011) was characterized by an unusually strong zonal jet stream across the North Atlantic and a rapid succession of intense cyclones, many of which crossed northwest Europe. One way to characterize the large

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Jesse Norris, Geraint Vaughan, and David M. Schultz

. 2008 ). As in Norris et al. (2014) , WRF was initialized with the baroclinic-wave test case, which consists of a zonal jet on an f plane ( s −1 ) in thermal wind balance with a horizontal temperature gradient at the surface of roughly 20 K (1000 km) −1 . The jet is obtained by inverting a baroclinically unstable potential vorticity distribution in the y – z plane, as in Rotunno et al. (1994) . The computational domain is 8000 km in the north–south direction. In the east–west direction, the

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Thomas H. A. Frame, John Methven, Nigel M. Roberts, and Helen A. Titley

predicting movements of the North Atlantic jet to be ~1.0 at 1-day lead times. The strike probability depends on multiple scales of motion and can be associated with position uncertainties in the centers of large and perhaps fairly predictable features such as cyclones, and the existence uncertainty in smaller and perhaps inherently unpredictable features such as small kinks on frontal surfaces. The strike probability does not distinguish between these two paradigms with all features being reduced to a

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David M. Schultz, Bogdan Antonescu, and Alessandro Chiariello

lengthen and narrow ( Fig. 3c ). At 300 mb, an 80 m s −1 jet upstream of a strong diffluent trough was associated with the surface pressure center ( Fig. 4 ). That the large-scale flow environment in which the cyclone was embedded was diffluent supports the formation of a Norwegian cyclone, weak warm front, and meridionally oriented occluded front (e.g., Schultz et al. 1998 ; Schultz and Zhang 2007 ). Fig . 3. Sea level pressure (black lines every 4 hPa), 850-mb potential temperature (green lines

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H. F. Dacre, P. A. Clark, O. Martinez-Alvarado, M. A. Stringer, and D. A. Lavers

region of an upper-level jet, a favorable location for cyclogenesis, beneath a region of strong upper-level divergence. Spatial distribution and magnitude of precipitation. In this section the spatial distribution and magnitude of precipitation and integrated water vapor transport (IVT) during the intensifying stage of the cyclone evolution is described. Figures 3a–c show the 6-hourly accumulated precipitation at three times during the development stage of the cyclone’s evolution. Also shown in

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Oscar Martínez-Alvarado, Suzanne L. Gray, and John Methven

, while that of and is shown in Fig. 3c . In this case, the flow moves westward across the whole dropsonde curtain ( Fig. 3a ). The maximum zonal velocity ( ) is located at midtropospheric levels around 450 hPa, constituting the system’s WCB. At lower levels, the maximum zonal velocity ( ) is located within a low-level jet (LLJ) toward the section’s northern edge behind the system’s cold front. The cold front is located around 55.5°N near the surface. A column with extends over the cold front

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Matthew R. Clark and Douglas J. Parker

; Browning 1995 ). This could explain the absence of a well-defined prefrontal low-level jet and associated strong alongfront component of prefrontal winds at low levels, such as is usually observed ahead of NCFRs associated with rearward-sloping fronts ( Browning and Pardoe 1973 ; Browning et al. 1998 ), and as observed in the other NCFR cases analyzed herein. b. Vorticity, convergence, and stretching The NCFR of 29 November 2011 was marked by a line of large vertical vorticity, horizontal convergence

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Jeffrey M. Chagnon and Suzanne L. Gray

depend on whether convection is parameterized or explicitly resolved, but the mesoscale convective systems analyzed were more convectively unstable than the cases presented in this paper. Finally, the characteristics of the dipole were not uniform across the large domains in which the simulations were performed. In case I, positive net diabatic PV accumulated at the level of the tropopause (i.e., 1.5–5 PVU) within a subdomain confined to low latitudes south of the primary jet (not shown). This

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