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John E. Janowiak, Valery J. Dagostaro, Vernon E. Kousky, and Robert J. Joyce

behavior such as the nighttime maxima over the central United States and over parts of central South America that are associated with low-level jet streams and orographic features. The main purpose of this paper addresses the second concern and thus we present an evaluation of the ability of the National Oceanic and Atmospheric Administration’s (NOAA) Global Forecast System model (GFS) and the regional Eta Model [currently referred to as the North American Mesoscale model (NAM)] to characterize the

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Wayne Higgins and David Gochis

is needed to determine contributions of rainfall-producing systems (e.g., mesoscale convective systems, organized sea-breeze convection lines, etc.) to the mean diurnal cycle of precipitation, including documentation of the frequency of occurrence of rainfall-producing systems. Results from these studies can be used to improve the ability of models to simulate the diurnal cycle toward achieving more accurate precipitation forecasts. b. Tiers II and III research Comparatively less progress has

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Andrea J. Ray, Gregg M. Garfin, Margaret Wilder, Marcela Vásquez-León, Melanie Lenart, and Andrew C. Comrie

, and is in language understood by information users ( Changnon et al. 1988 ; Ray 2004 ; Lemos and Morehouse 2005 ; Jacobs et al. 2005a ). These contexts encompass institutional, socioeconomic, and political settings with a range of sensitivities, vulnerabilities, and capacities to respond to climate and forecasts. Growing population and rising water use increase vulnerability in both the United States ( Liverman and Merideth 2002 ) and northern Mexico ( Magaña and Conde 2000 ). Fortunately

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Richard H. Johnson, Paul E. Ciesielski, Brian D. McNoldy, Peter J. Rogers, and Richard K. Taft

systems (ships, aircraft, wind profilers, radars, and surface stations), was designed to study the complex and multifaceted properties of the North American summer monsoon: its onset, precipitation characteristics, the Gulf of California (GoC) low-level jet, gulf surges, easterly waves, tropical cyclone influences, orographic effects, mesoscale convective systems, and the diurnal cycle of convection ( Higgins et al. 2006 ). While the North American summer monsoon is not as dramatic as its Asian

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Arthur V. Douglas and Phillip J. Englehart

located 3°–4° to the east of the division. In both Sonora and Sinaloa, weak capping associated with downslope flow is common when a trough is over the plateau and winds are from the east and northeast ahead of the system. As the trough moves west and the cap is broken by intense daytime heating, mesoscale convective systems (MCSs) frequently breakout. This synoptic setup was noted by forecasters throughout the NAME experiment. It is interesting to note that for climate regions 2 and 3 that the fairly

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X. Gao, J. Li, and S. Sorooshian

viewpoint of model improvement, it is important to examine how the diagnostic features and their variations can be captured by a numerical model in its case-by-case predictions. This study intends to evaluate the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model’s (MM5) capabilities and limitations in reproducing intraseasonal variabilities in the NAM precipitation in the context of the 2004 monsoon season. Studies for the past two decades have

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Timothy J. Lang, David A. Ahijevych, Stephen W. Nesbitt, Richard E. Carbone, Steven A. Rutledge, and Robert Cifelli

Atmospheric Research (NCAR) S-band dual-polarization Doppler radar (S-Pol), placed ∼100 km north of Mazatlán, Mexico, on the coast west of the SMO; and two Servício Meteorológico Nacional (SMN) Doppler radars—one at Guasave farther north on the coastal plain and one at Cabo San Lucas at the tip of the Baja California peninsula. A central goal of NAME is to characterize and understand convective and mesoscale processes in the complex terrain of the core monsoon region and their interaction within the

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Myong-In Lee, Siegfried D. Schubert, Max J. Suarez, Isaac M. Held, Arun Kumar, Thomas L. Bell, Jae-Kyung E. Schemm, Ngar-Cheung Lau, Jeffrey J. Ploshay, Hyun-Kyung Kim, and Soo-Hyun Yoo

geographical variations in the response that are the result of a number of different forcing mechanisms. These mechanisms can be classified into three categories, according to their horizontal scale: 1) local convective instability induced by boundary heating ( Machado et al. 2002 ); 2) regional controls from differential heating such as land–sea circulations, topography, surface vegetation type ( Machado et al. 2004 ), and mesoscale convective systems ( Maddox 1980 ; Riley et al. 1987 ; Arritt and

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Katrina Grantz, Balaji Rajagopalan, Martyn Clark, and Edith Zagona

–ocean temperature gradient, consequently delaying the summer monsoon. It is reasoned that the wetter winter and spring conditions in the southwestern United States are largely driven by winter oceanic–atmospheric conditions, especially Pacific SSTs, the PDO–ENSO pattern, and the observed increase in ENSO activity in recent decades ( Trenberth and Hoar 1996 ; Rajagopalan et al. 1997 ). Links to the antecedent land, ocean, and atmosphere conditions offer hope for long-lead forecasts of the summer monsoon. This

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Mekonnen Gebremichael, Enrique R. Vivoni, Christopher J. Watts, and Julio C. Rodríguez

semiarid areas, which are generally characterized by low annual rainfall and large interannual variability. The large-scale variability of monsoon rainfall and its relationship to teleconnective, and synoptic- and mesoscale forcing mechanisms has been a focus of many studies (e.g., Douglas et al. 1993 ; Adams and Comrie 1997 ; Higgins and Shi 2001 ). However, work on the submesoscale (<75 km) variability of rainfall is noticeably absent in the literature, mainly due to a paucity of ground

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