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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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Matthew A. Janiga and Chris D. Thorncroft

-scale environments and convective properties. The variability of large-scale thermodynamic and dynamic fields as a function of AEW phase and geography is also examined and used to explain the contrasts in convective properties. Section 4 summarizes the results and offers some conclusions. 2. Data and methodology As in the companion paper JT14 , this study uses data from TRMM and the ERA-Interim reanalysis from the period June–September (JAS) 1998–2012. TRMM PR–based precipitation features (PFs), defined as

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Ronald L. Holle, Kenneth L. Cummins, and William A. Brooks

stroke location accuracy (LA) have been validated over Florida ( Mallick et al. 2014 ). The validation showed a GLD360 CG flash DE (relative to the NLDN in Florida) of 67%, a CG stroke DE of 37%, and a CG stroke median LA of 2.0 km. The performance of GLD360 over North America is estimated to be a CG flash DE of 70% and a median CG stroke LA of 2–5 km. GLD360 stroke densities in the second portion of this study are also in 20 km by 20 km grid squares within geographical boundaries extending beyond

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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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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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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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Chung-Chieh Wang, George Tai-Jen Chen, and Kuok-Hou Ho

described later in sections 4c and 5 , followed by the related diagnostic results. 3. Synoptic environment and frontal retreat In this section, the retreat of the mei-yu front and the accompanied synoptic evolution in the present case are described. In Fig. 1 , manually analyzed surface weather maps near Taiwan during the case period, produced operationally by the Central Weather Bureau, are shown to depict the general frontal locations. At 0600 UTC 13 June ( Fig. 1a ), the front had already passed

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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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Lukas Papritz and Stephan Pfahl

Pole of the rotated model grid is located at 15°N and 155°W in geographical coordinates. In addition, we run the model in the so-called climate mode, allowing for continuous updates of sea surface temperature (SST) from the 6-hourly analyses. The model domain and topography are depicted in Fig. 2 . The domain consists of 1100 × 740 grid points and covers the RS and the ABS, as well as parts of the Transantarctic Mountains, the Ross Ice Shelf, and Marie Byrd Land (see Fig. 2 for location names

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