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

1. Introduction Precipitation is a fundamental element of the earth’s weather, water, and climate system, and is a primary link in the transfer of mass and energy between the atmosphere and ocean. Because of that, it is important to monitor variations in precipitation, yet it remains a challenge to quantify precipitation over all regions of the planet and even more of a challenge to forecast it correctly. Furthermore, even where rain gauge density is relatively dense, such as over the United

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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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Wayne Higgins and David Gochis

international team of NAME scientists from the United States, Mexico, and Central America carried out a major field campaign during the summer of 2004 to develop improved North American monsoon forecasts. NAME 2004 was an unprecedented opportunity to gather an extensive set of atmospheric, oceanic, and land surface observations in the core region of the North American monsoon, including northwestern Mexico, the southwestern United States, and adjacent oceanic areas. The campaign involved scientists from

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Kingtse C. Mo, Eric Rogers, Wesley Ebisuzaki, R. Wayne Higgins, J. Woollen, and M. L. Carrera

assimilation and SSTs in the Gulf of California and address the uncertainties in the analyses. The impact studies are based on three of NCEP’s data assimilation systems: one global and two regional systems. The global system is the Climate Data Assimilation System (CDAS). During the EOP, data from the operational Global Data Assimilation System (GDAS) forecast system were also archived. The GDAS products serve as a reference because it has higher resolution and captures the monsoon-related features better

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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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Arthur V. Douglas and Phillip J. Englehart

monsoon season in northern Mexico. Principal investigators and forecasters associated with the field experiment agreed that the synoptic features and event phenomena given in Table 1 would be of primary concern during the decision-making process for calling IOPs. With very detailed measurements of these systems and specific phenomena, NAME expects to develop a better understanding of the various components of the monsoon system, ranging from the diurnal cycle to large-scale forcing. This note

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

days—the longest updating time interval in our tests, the 2004 NAM simulation was comparable with observations and consistent with the NAM’s diagnostic features when checked at intraseasonal time scales (i.e., the monthly to daily means). Because predicting intraseasonal precipitation and circulation features is an important issue for operational short-term weather/climate forecasts and because the predictions have many applications, to areas such as hydrology and agriculture, we focus on examining

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Alberto M. Mestas-Nuñez, David B. Enfield, and Chidong Zhang

European Centre for Medium-Range Weather Forecasts (ECMWF) 15-yr global reanalysis (ERA15, Gibson et al. 1997 ). They examine uncertainties arising from choices of area boundaries, calculation algorithms, spatial and temporal resolutions, as well as a combination of these effects. Their main conclusion is that these uncertainties are smaller than the large annual and interannual variabilities in moisture flux divergence estimated from the NCEP–NCAR reanalysis. The implication is that the NCEP

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

reviews by Douglas et al. 1993 ; Adams and Comrie 1997 ; Higgins et al. 2003 ) and these features are critical for precipitation forecasting and water resource management in this part of North America. The purpose of this paper is to document the summer 2004 mean flow characteristics and multiscale variability over the NAME domain using data from the NAME sounding network. Particular attention will be given to the kinematic and thermodynamic properties, as well as the apparent heat and moisture

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Michelle Hallack-Alegria and David W. Watkins Jr.

very different, seasonal rainfall totals tend to be uncorrelated with each other, and thus separate cold season drought frequency analysis is warranted. Details of drought frequency analysis for the cold season may be found in Hallack-Alegria (2005) , who also investigated the potential for cold season precipitation forecasting. Preliminary analysis showed significant correlation between warm season ENSO phenomena and winter precipitation, with La Niña events consistently leading drier

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