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H. Reed Ogrosky and Samuel N. Stechmann

average is removed from each dynamical field prior to the regression in order to remove the effects of low-frequency variability due to, for example, ENSO. A separate regression equation is solved for each variable at each longitude, latitude, pressure level, and time lag. The resulting linear regression coefficients are then used to produce a composite picture of the evolution of each wave type. In these composites, the winds are plotted only at locations where they are deemed to be significant at

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Salvatore Pascale and Simona Bordoni

Abstract

In this study ERA-Interim data are used to study the influence of Gulf of California (GoC) moisture surges on the North American monsoon (NAM) precipitation over Arizona and western New Mexico (AZWNM), as well as the connection with larger-scale tropical and extratropical variability. To identify GoC surges, an improved index based on principal component analyses of the near-surface GoC winds is introduced. It is found that GoC surges explain up to 70% of the summertime rainfall over AZWNM. The number of surges that lead to enhanced rainfall in this region varies from 4 to 18 per year and is positively correlated with annual summertime precipitation. Regression analyses are performed to explore the relationship between GoC surges, AZWNM precipitation, and tropical and extratropical atmospheric variability at the synoptic (2–8 days), quasi-biweekly (10–20 days), and subseasonal (25–90 days) time scales. It is found that tropical and extratropical waves, responsible for intrusions of moist tropical air into midlatitudes, interact on all three time scales, with direct impacts on the development of GoC surges and positive precipitation anomalies over AZWNM. Strong precipitation events in this region are, however, found to be associated with time scales longer than synoptic, with the quasi-biweekly and subseasonal modes playing a dominant role in the occurrence of these more extreme events.

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Roderick van der Linden, Andreas H. Fink, Tan Phan-Van, and Long Trinh-Tuan

a resting period during the dry season. Besides impacts on the cultivation of coffee and other agricultural products, heavy rainfall bears a risk of flooding and landslides. Fig . 1. Topographic map of the study area. Map of Vietnam and adjacent countries and zoom in on the Central Highlands region. Numbers in the zoomed map correspond with the locations of stations that are used for the analysis of rainfall events ( Figs. 2 , 6 , 9 , and 12 ). The stations are listed in Table 1 . The dashed

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Clémence Macron, Yves Richard, Thomas Garot, Miloud Bessafi, Benjamin Pohl, Adolphe Ratiarison, and Andrianaharimanana Razafindrabe

. Fig . 1. (a) Location of the 37 daily rainfall stations and percentage of missing values. The dot size is proportional to the percentage of missing values (stations with fewer missing values are larger); the colors also represent the percentage of missing values (see color scale for legend). Names cited in the text appear in red for stations, in blue for ocean sectors, and in brown for mountains. (b) Temporal distribution of the missing values for each of the 37 stations for NDJF 1971–99. (c) Mean

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Andrew I. Barrett, Suzanne L. Gray, Daniel J. Kirshbaum, Nigel M. Roberts, David M. Schultz, and Jonathan G. Fairman Jr.

of potentially high-impact weather: terrain-locked convective bands. In particular, we study four recent such events in the United Kingdom to determine whether convection-permitting ensemble simulations succeed in accurately representing the bands. Specifically, we address the following questions: Do convection-permitting ensembles capture the structure, location, timing, intensity, and duration of quasi-stationary convective bands? What evaluation methods provide useful insights into forecast

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Prabhani Kuruppumullage Don, Jenni L. Evans, Francesca Chiaromonte, and Alex M. Kowaleski

= magenta, 3 = dark blue, 4 = cyan, and 5 = green). As an example, consider the IFS forecasts initialized at 0000 UTC 16 September, ( Fig. 7d ); at this time, Sinlaku was located northeast of Taiwan and was drifting to the east as a 45-kt (23 m s −1 ) tropical storm ( Fig. 2a , location 5 in the Philippine Sea). In the red mean trajectory (westernmost cluster), Sinlaku moves farthest to the north, staying west of Kyushu and moving into the Sea of Japan before making landfall in northwest Honshu. In the

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Ben Jolly, Adrian J. McDonald, Jack H. J. Coggins, Peyman Zawar-Reza, John Cassano, Matthew Lazzara, Geoffery Graham, Graeme Plank, Orlon Petterson, and Ethan Dale

) provide a unique opportunity to assess Polar WRF output from AMPS at very high resolution. Fig . 1. Map of deployment area with topographic contours every 250 m. Ross Island (marked by proxy through Mt. Erebus and Mt. Terror) is situated in the top-left segment, with Scott Base and McMurdo Station located at the tip of the peninsula on the south side (near Pegasus North). The smaller circular markers denote SWS locations while the larger, labeled ones denote existing AWS locations. SWS are color coded

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Anthony G. Barnston, Nicolas Vigaud, Lindsey N. Long, Michael K. Tippett, and Jae-Kyung E. Schemm

still needs a more convincing demonstration in the observations and/or the model, and we return to Table 4 . Table 4. (top) Location key of seven geographical subsectors. (bottom) The percentage of the average over the eight MJO phases, of ACE in (left) observations and (right) in the T382 CFS model, by the MJO phase for each of the seven geographical subsectors in the North Atlantic. The average entry for any subsector, over the 8 phases, is 100. The location of the cells within each table

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George R. Alvey III, Jonathan Zawislak, and Edward Zipser

intensifying TCs [particularly those that undergo rapid intensification (RI)] have a higher proportion of convective bursts within the inner core? 3) If important, is there a favored location for these bursts during intensification? Rodgers et al. (1998 , 2000) and Guimond et al. (2010) analyzed several TCs in which intense convective bursts precede or are coincident with the start of RI. One hypothesis for how convective bursts are favorable for intensification is that they moisten the middle

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Eric B. Wendoloski, David R. Stauffer, and Astrid Suarez

model with terrain-following vertical coordinates and Arakawa C horizontal gridpoint staggering ( Skamarock et al. 2008 ). The WRF configuration includes four one-way nested domains of 12-, 4-, 1.3-, and 0.4-km horizontal grid spacing with the 1.3- and 0.4-km nests centered over central Pennsylvania and the Nittany Valley ( Fig. 1a ). The location and topography of the 0.4-km domain with respect to the topography of the 1.3-km domain are shown in Figs. 1b and 1c . Initial and lateral boundary

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