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Louis L. Lussier III, Blake Rutherford, Michael T. Montgomery, Mark A. Boothe, and Timothy J. Dunkerton

location is often referred to as the sweet spot. There are three hypothesized ways ( Dunkerton et al. 2009 ) that the recirculating cat’s-eye region provides a favorable environment for tropical cyclogenesis: 1) wave breaking or rollup of the cyclonic vorticity and moisture near the critical surface in the lower troposphere provides the moist vorticity seedlings and a favorable environment for vorticity aggregation; 2) the cat’s-eye is a region of quasi-closed Lagrangian circulation, and air is

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Edward I. Tollerud and Steven K. Esbensen

hatched regionson the horizontal plots on the figures in this paper(e.g., Fig. 1) identify areas where the index is 1. The anvil index is used to locate duster centers inthe compositing procedure described in Section 6. Itis also used as an indicator of a duster's stage of development. We break the life cycle of each duster intothree stages: growing, mature and dissipating. In thegrowing stage, the anvil first appears (that is, the indexbecomes 1 at some location in the vicinity of the duster

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Clifford F. Mass and Mark D. Albright

Cascade Mountains to devastate the area nearEnumclaw,~ Washington (see Fig. 1). Gusts exceeding50 m s-I leveled homes and barns, tore roofs offhundreds of buildings and downed numerous treesand powefiines. Damage was conservatively estimatedin the tens of millions of dollars. Although theEnumclaw area was particularly hard hit, strong butlesser winds also struck several other locations in ornear gaps of the Cascade Mountains of Oregon andWashington. For example, substantial winds anddamage were found

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Pascal J. Mailier, David B. Stephenson, Christopher A. T. Ferro, and Kevin I. Hodges

with particular emphasis on the North Atlantic and European sectors. Section 6 summarizes the main findings and suggests possible future work. 2. Background a. Complete serial randomness A useful statistical tool to model the succession of events such as cyclone occurrences at a particular location is the point process (see Cox and Isham 1980 for a detailed discussion). The simplest hypothesis that can be formulated is that cyclones occur in a completely random fashion (i.e., the occurrence

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Kelly M. Mahoney and Gary M. Lackmann

severe surface winds and RIJ descent in idealized bow-echo systems to magnitudes of low-level shear and CAPE ahead of the system. Fully idealized studies (e.g., Weisman 1992 , 1993 ) provide an important complement to a study such as this one, where (i) changes in humidity have introduced slight changes in CAPE and (ii) the system itself forms in different geographical locations and thus experiences slight differences in CAPE and wind shear due to thermodynamic gradients in the initial environment

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Daniel Gombos and James A. Hansen

singular values, w ( HT08 ). However, despite the computational stability of the SVD, multicolinearities due to geographic proximity are likely to render the estimate of 𝗣′ e −1 via (14) ill-conditioned. A singular value spectrum of the data used in section 5 of this paper (not shown) reveals that the retained singular values of 𝗣′ e T 𝗣′ e (and undoubtedly those of other realistic 𝗣′ e T 𝗣′ e matrices) decay to zero, leading to high condition numbers and correspondingly inflated

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Richard C. Igau and John W. Nielsen-Gammon

, including the evolution of these features over Mexico. The relationship of the LLJs to the lee trough and EML is discussed in later sections. The history of air parcels that constitute the EML in this simulation is documented in Lanicci and Warner (1997) . Figure 3 shows a portion of the topography used in the model and the location of vertical sections and geographic regions referred to in later discussions. The terrain varies north to south from the gently sloping plains of the southern United

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Mary M. McGarry and Richard J. Reed

the land stations were combined into four geographically distinct groups and the ship data into asingle group before making the harmonic analyses. The long-term representativeness of the results for theland areas is judged by comparing them with the results obtained from analysis of data presented by Burpee(1976) on the frequencies of occurrence of thunder, moderate to heavy precipitation and light precipitationduring the period June-September 1966-69. The main findings are the following: 1

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Da-Lin Zhang, John S. Kain, J. Michael Fritsch, and Kun Gao

extensively by MD to classify current modeling approaches and to challengesome of the previous simulation studies.) Section 3 dis * On leave from the Department of Geography, Hangzhou University, Hangzhou, People's Republic of China. Corresponding author address: Dr. Da-Lin Zhang, Department ofAtmospheric and Oceanic Sciences, McOill University, 805 Sherbrooke Street West, Montreal, Quebec H3A 2K6, Canada.cusses MD's criteria for classifying modeling approaches and elucidates the individual roles

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Manuel D. Zuluaga and Robert A. Houze Jr.

forms of convection. Since the form taken by convection affects how the convection interacts with the large-scale tropical atmospheric circulation, it is important to understand the varied phenomenology of the convective elements across the region. Fig . 1. Geographical regions referred to in this study. The labeled rectangles are regions of composites referred to in the text. Convection in the regions of the equatorial Africa and neighboring eastern Atlantic has been studied many times in the past

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