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Julia H. Keller, Christian M. Grams, Michael Riemer, Heather M. Archambault, Lance Bosart, James D. Doyle, Jenni L. Evans, Thomas J. Galarneau Jr., Kyle Griffin, Patrick A. Harr, Naoko Kitabatake, Ron McTaggart-Cowan, Florian Pantillon, Julian F. Quinting, Carolyn A. Reynolds, Elizabeth A. Ritchie, Ryan D. Torn, and Fuqing Zhang

downstream, and the next downstream ridge builds, which signifies the downstream propagation that arises from the initial local changes in the jet near the site of ET ( Fig. 1c ). Meanwhile, Nuri reintensifies into a strong extratropical cyclone and initiates cyclonic wave breaking over the western North Pacific ( Fig. 1c ). Subsequently, the upper-level wave pattern amplifies farther downstream, establishing a high-amplitude ridge–trough couplet over North America. A heat wave develops in the high

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Volkmar Wirth, Michael Riemer, Edmund K. M. Chang, and Olivia Martius

gradual than that of the carrier wave (dotted) or the RWP signal (blue). Fig . 1. Schematic of a Rossby wave packet (RWP) at a specific time. The blue line represents , the black dotted line is the underlying carrier wave , and the two red lines depict plus (upper line) and minus (lower line) the amplitude . A real world example is presented in Fig. 2 . Figure 2a shows the midlatitude jet with large meridional undulations over North America. Over the rest of hemisphere, the jet is more zonally

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Clark Evans, Kimberly M. Wood, Sim D. Aberson, Heather M. Archambault, Shawn M. Milrad, Lance F. Bosart, Kristen L. Corbosiero, Christopher A. Davis, João R. Dias Pinto, James Doyle, Chris Fogarty, Thomas J. Galarneau Jr., Christian M. Grams, Kyle S. Griffin, John Gyakum, Robert E. Hart, Naoko Kitabatake, Hilke S. Lentink, Ron McTaggart-Cowan, William Perrie, Julian F. D. Quinting, Carolyn A. Reynolds, Michael Riemer, Elizabeth A. Ritchie, Yujuan Sun, and Fuqing Zhang

-transitioning counterparts. Post-ET weakening was approximately twice as likely as post-ET intensification, whereas post-ET cold-core thermal structure was more than twice as likely as post-ET warm-seclusion thermal structure. Post-ET warm-seclusion cyclones were larger and were located closer to North America as ET began than their post-ET cold-core counterparts. However, more research is needed to quantify the effects of TC size and intensity on the outcome of ET as well as what factors govern post-ET intensity change

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Clifford Mass and Brigid Dotson

providing some warning. Kuo and Reed (1988) using the MM4 for that storm found that improving the initialization with supplementary data produced a moderate cyclone, albeit still weaker than observed. In contrast, the 20 January 1993 Inauguration Day Storm and the 12 December 1995 event were well forecast by the Eta Model. Similar skill was noted for the December 2006 Hanukkah Eve event using the Global Forecast System (GFS) and North American Mesoscale (NAM) models. A clear contributor to more

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Roland A. Madden and Paul R. Julian

,the authors again used spectrum analysis to describe-c 1994 American Meteorological SocietyMAY 1994 MADDEN AND JULIAN 815this time--tropospheric, synoptic-scale features in thetropics. In those days, long time series were not readily available from tropical rawinsonde stations, nor were theyeasy to process with the computers of the time. Theabove authors

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Dayton G. Vincent

, structure, and characteristics of theSPCZ are described, with attention devoted to seasonal Corresponding author address: Dr. Dayton G. Vincent, Department of Earth and Atmospheric Sciences, Purdue University, 1397Civil Engineering Building, West Lafayette, IN 47907.c 1994 American Meteorological Societychanges. This is followed by a summary of theories andobservations concerning its origin and maintenance(section 3). Next, the significance of the SPCZ and itsrole within global-scale circulation

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Daniel Keyser and M. A. Shapiro

100 kmstation spacing and a 6 h sampling frequency. The greater spatial and temporal resolution afl?ordedby the European radiosonde network in comparisonwith that of North America (400 km station spacing,12 h sampling interval) probably contributed to thedifferences between the analyses of the cyclonic: shearzone in the vicinity of the LMW and in the lowerstratosphere by Berggren and by Palm6n and Nagler,the latter of which is broader and more diffuse (compareFEBRUARY 1986

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J. R. Garratt

Percentage cover ~o CDN(iO) C~NLand mass (X107 km~) ~ Forest Desert (m) (X10a) (X10~)North America(70--10-N) 1.97 40- 40 < 5 0.17 10.1 1.89South America(10-N-50-S) 1.76 20- 50 <5 0

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Robert Wood

are major differences in the seasonal phase between the western and the eastern sides of the midlatitude North Atlantic and Pacific Ocean, with a wintertime peak over the western sides and summertime peaks over the eastern sides ( Weaver and Ramanathan 1997 ). This probably reflects the greater importance of surface sensible heat flux (e.g., during wintertime cold-air outbreaks) for stratocumulus on the western side. Over the tropical oceans, there does not appear to be a systematic favored month

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Bogdan Antonescu, David M. Schultz, Fiona Lomas, and Thilo Kühne

column of air, in contact with the surface, pendant from a cumuliform cloud, and often visible as a funnel cloud and/or circulating debris/dust at the ground” ( American Meteorological Society 2015a ). The Glossary of Meteorology defines a waterspout as “any tornado over a body of water” ( American Meteorological Society 2015b ). The National Weather Service classifies tornadoes separate from waterspouts. Yet, as Rauhala et al. (2012) have argued, a strict separation between tornadoes and

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