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turn their attention to a simplemethod of observing that may be very helpful in settling thepoints at issue. I f the aurora is an optical illusion,. such asthe rainbow or halo, then two observers at neighboring sta-tions, or one observer by moving from place to place, will ob-serve the beams and arches of light at the same altitude abovethe horizon. But if these are material entities having a defi-nite locus, then. as the observer changes his location, thearches and beams will change theirs, as

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Olli M. Turpeinen, Azzouz Abidi, and Wahid Belhouane

, however, based on the individual tracking of cloud entities throughout theirlifetimes, which requires substantial computing resources. Therefore, they are feasible for use only inderiving rainfall estimates over limited areas and timeperiods. The scheme has to be relatively simple if thecoverage is semi-global and the sampling is made frequently for a long period of time. The approach proposed by Arkin (1979) constitutes a feasible solutionfor the global scale. He has shown that the fractionalcloud

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Michael S. Fischer, Brian H. Tang, and Kristen L. Corbosiero

significantly more westward than non-RI episodes in the corresponding cluster, although no significant differences in the locations of RI and non-RI episodes were found in the cutoff cluster. Fig . 7. Geographic locations of the 850-hPa relative vorticity centroids for RI episodes (red) and non-RI episodes (blue) for high-PV TCs within the (a) cutoff cluster, (b) NW trough cluster, and (c) NE trough cluster. 5. The relationship between upper-tropospheric trough structure and RI The upper-tropospheric trough

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Lance F. Bosart and Frederick H. Carr

usingconventional sur/ace and aerological data. Hourly predpitation maps and surface maps showed the northeastward motion and intensification oi a developing rain area over eastern Kentucky at 1200 GMT 20 June1972. This area remained a separate entity from the main Agnes rainshield. Nonlinear balanced omega aswell as kinematic omega computations suggest that a weak short wave in the mid and upper troposphereprovided the initial triggering mechanism for the growth of the rain area. Plentiful moisture was

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Romualdo Romero, Clemente Ramis, Sergio Alonso, Charles A. Doswell III, and David J. Stensrud

the eastern coast of Spain. Moderate to heavy daily rainfall occurred in eastern Spain (especially in Valencia; see Fig. 1 ) from 1 to 7 February, except on 5 February. Although the exact amounts and locations of the rainfall varied from day to day, the pattern of rainfall each day was similar to that shown in Fig. 3 , from 2 February. The second case, the “Piedmont” event, refers to the heavy rains that occurred in northwestern Italy during the period 4–6 November 1994. Whereas the pattern

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Toby N. Carlson

indicate location of major upper-tropospheric windmaxima. system.~ Relative isentropic analysis was first used by Eliassen and Kleinschmidt (1957) and later by Green et al. (1966), Carlson and Ludlam (1968), Browning and his associates (Browning and Har old, 1969; Browning, 1971; Harrold, 1973; and most recently by Atkinson and Smithson, 1978)- to study the motion of airstreams through wave cyclones. Reiter and his associates (Reiter and Mahlman, 1965; Reiter et al., 1965) and Danielsen (Danielsen and

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Altuğ Aksoy, David C. Dowell, and Chris Snyder

convection in terms of its bulk properties and not on explicit prediction of individual storm structures and evolution. Nevertheless, their argument that difficulties in estimating storm environments and convective initiation make it very difficult for cloud-scale models to explicitly forecast thunderstorm behavior is still valid today, considering that uncertainties continue to exist in storm environments and potential locations of convective initiation. In addition, our models are far from being

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Raúl E. López, David O. Blanchard, Daniel Rosenfeld, William L. Hiscox, and Marjorie J. Casey

height maps are matched to the WSR57 low-elevation reflectivity maps. The principal resultof this group of programs is a tabulation for every lowlevel scan, of the radar characteristics of every echoand cell present in that scan, a cross reference to thecontinuation of the echoes and cells in the next scan,and the lifetime properties of each entity. Those tabulations constitute the basic data source for the investigation of the ensemble properties of the cells andechoes, their different structure

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Edward A. O'Lenic

This section examines the magnitude, location, andgeographical distribution of the changes in LFM 500mb height analyses due to using VAS data in the LFManalysis scheme. One case, that of 10 November 1981(case A), will be examined in greater detail in order toclarify the data coverage and the effect of VAS data onspecific aspects of the analysis. In order to put the impact of VAS data into perspective, the VAS analysisfor this case will be compared with an analysis validat the same time made using

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Charles S. Neumann and Joseph M. Pelissier

.further identified in Table 5. All occurred on northzone storms and are identified in Fig. 9A, by anindex number that is plotted adjacent to the specificerror location. Recurvature errors (Table 5) are essentiallycaused by failure to (i) anticipate initial recurvatureinto the westerlies and (ii) identify a renewal ofwesterly motion (sometimes temporary) after initialeasterly motion (recurvature) already has occurred.A classic case of the former occurred with Gladys(1975) (case number 2) and of the latter with

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