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Bohumil M. Svoma

1. Introduction The influx of moisture associated with the North American monsoon during the months of June–September accounts for the majority of annual precipitation in much of Arizona, contributing up to 60% in the southern portion of the state ( Douglas et al. 1993 ). Although some researchers have found that much of this precipitation is linked to gulf-surge events ( Dixon 2006 ; Becker and Berbery 2008 ), which are low-level influxes of cool and moist air from the Gulf of California

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Seung-Eon Lee and Kyong-Hwan Seo

that El Niño induced an anomalous anticyclone over the Philippine Sea, which influenced EASM circulation through a meridional tripole teleconnection pattern called the Pacific–Japan (PJ) teleconnection ( Nitta 1987 ). In the extratropical region, a wave train zonally propagating from western Europe to North America through East Asia is called the circumglobal teleconnection (CGT; Ding and Wang 2005 ). The North Atlantic Oscillation (NAO) has been known to modify EASM rainfall through the CGT

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Paul J. Kocin, David A. Olson, Arthur C. Wick, and Robert D. Harner

Division (MOD) ofthe National Meteorological Center (NMC) is responsible for producing a variety of surface weather analysisproducts. These products include analyses of surfaceweather conditions over North America and offshorewaters at 3-hourly intervals (the North American orNA charts), analyses over the Northern Hemisphereevery 6 h (the Northern Hemispheric or NH charts),and a 7-day collection of daily surface and other chartscontained in "Daily Weather Maps, Weekly Series"(DWM), a publication

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Nicholas A. Bond and Gabriel A. Vecchi

intermediate timescales, useful outlooks may be possible through consideration of the effects of the Madden–Julian oscillation (MJO) on the atmospheric circulation over the North Pacific Ocean and western North America (e.g., Higgins and Mo 1997 ; Waliser et al. 2003 ). The MJO is the dominant mode of subseasonal tropospheric variability over the tropical Indian and Pacific Oceans. The MJO was originally identified as a coherent, eastward-propagating perturbation in tropical sea level pressure and upper

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Omar V. Müller, Miguel A. Lovino, and Ernesto H. Berbery

), and Heidke skill score (7% higher on average). The lower scores in the dry region are due to the difficulties in forecasting the few rain days that occur. The only score that is better over the dry region is the accuracy (on average 7% higher than in the wet region), largely because of the rise in correct negatives. Despite the diversity of model versions and parameterizations, the ranges of the skill scores are similar to those found over North America even for individual cases (e.g., Pennelly

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Isaque Saes Lanfredi and Ricardo de Camargo

1. Introduction Cold-air incursions across South America can present particular characteristics due to the presence of the Andes Mountains, which contribute to the advancement of cold fronts to the southwest of the Amazon basin. Besides organizing the convection in northern Brazil ( Garreaud and Wallace 1998 ), the continental fronts are also known to cause impacts that are especially felt by agriculture because of freeze events, with significant losses in coffee production and consequent

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Mark R. Jury and David M. Sanchez

tropical moisture northward from South America. During boreal spring (April and May) the jet stream may bifurcate, giving rise to high-amplitude, short-wavelength patterns that favor the development of meridional cloud bands ( Keyser and Shapiro 1986 ). Simultaneously, the northern Hadley cell and Caribbean trade winds weaken, and the ITCZ drifts northward toward Venezuela ( Amador 1998 ; Magaña et al. 1999 ; Amador et al. 2000 ; Muñoz et al. 2008 ). There is a greater probability of westerly

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Geoffrey J. DiMego, Kenneth E. Mitchell, Ralph A. Petersen, James E. Hoke, Joseph P. Gerrity, James J. Tuccillo, Richard L. Wobus, and Hann-Ming H. Juang

parallel (RAFX)00-h forecasts of height, temperature, and vector wind against 96North American radiosonde observations for the period 24 Marchto 20 April 1991. TAI~LE ld. Verification of operational (RAFS) and parallel (RAFX)00-h forecasts of height, temperature, and vector wind against 15Alaskan-region radiosonde observations for the period 24 March to20 April 1991.Bias STDEBias STDERAFS RAFX RAFS RAFXRAFS RAFX

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Christopher M. Fuhrmann and Charles E. Konrad II

in the present study and found that the trajectory model was able to resolve key aspects of winter precipitation, such as temperature and moisture, and that ensemble members with varying trajectory paths were distinguished by their meteorological properties. The meteorological dataset used to initialize each HYSPLIT run was the National Centers for Environmental Prediction's (NCEP) Eta Data Assimilation System (EDAS), which became the North American Mesoscale Model (NAM) Data Assimilation System

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Baoqiang Tian and Ke Fan

temperatures . Geophys. Res. Lett. , 29 , 2043 , doi: 10.1029/2002GL014952 . Scaife, A. A. , and Coauthors , 2014 : Skillful long-range prediction of European and North American winters. Geophys. Res. Lett., 41, doi: 10.1002/2014GL059637 . Smith, T. M. , Reynolds R. W. , Peterson T. C. , and Lawrimore J. , 2008 : Improvements to NOAA’s historical merged land–ocean surface temperature analysis (1880–2006) . J. Climate , 21 , 2283 – 2296 , doi: 10.1175/2007JCLI2100.1 . Stephenson, D. B

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