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Kerry Emanuel and Fuqing Zhang

in the location of strong vortices entail large, non-Gaussian errors in winds at fixed points in space ( Ravela et al. 2007 ). To all this, one can add the operational difficulties and expense of observing tropical cyclones. Even today, there are appreciable discrepancies among real-time intensity estimates by different techniques based on satellite- and aircraft-based observations ( Landsea and Franklin 2013 ). In attempting to improve any type of numerical weather forecast, it is useful to be

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Irving I. Gringorten

forecast.While the forecasting technique described in this paperis objective, it is emphasized that there is no essentialqualitative difference between this technique and themethods normally applied in a more subjectivemanner.2. Meeting the operational requirementsFor qn insight into the operational requirements, letus consider airport operations. A dispatcher, who isresponsible for permitting the take-off of an airplane,usually weighs the importance of his decision againstthe assurances of the

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Romeo Alexander, Zhizhen Zhao, Eniko Székely, and Dimitrios Giannakis

to suggest that the past can serve as a guide to the future. One of the simplest empirical forecasting techniques is the classical analog forecasting method of Lorenz (1969) , which first identifies, via Euclidean distances, a moment in the past that is most similar to the present and then casts the historical evolution from that moment as the forecast for the future. In the context of tropical intraseasonal oscillations, analog techniques have been employed in real-time forecasting of Indian

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G. V. Price

-orthogonal stream-axis coordinates with a condition of gradient flow in the directionof the jet (no assumption is made on the flow in the cross-jet direction). Approximating functions areused to represent the spatial dependence of the variables, and the forecast is advanced using a Galerkintechnique with an Euler-backward time extrapolation scheme. Three-dimensional forecast experiments are performed using a barodinic zonal jet with a superimposedperturbation of the type studied numerically by Mudrick (1974

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H. M. Christensen, I. M. Moroz, and T. N. Palmer

accuracy of high-resolution integrations. Tuning the many hundreds of parameters in models is a difficult, costly process, usually performed by hand. An attractive alternative is the use of a Bayesian parameter estimation approach. This estimates the probability distribution of parameters and provides a framework for using new data from forecasts and observations to update prior knowledge about the parameter distribution ( Beck and Arnold 1977 ). One specific technique is the Ensemble Prediction and

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Sverre Petterssen, M. A. Estoque, and Lawrence A. Hughes

the graphical integrations were used as a first approximation,supplementary techniques were applied to obtain final forecasts of the pressure distribution at sea level.The results of the verification are discussed and compared with those pertaining to other forecasting procedures. The geographical distribution of errors is discussed and interpreted.1. IntroductionThe experiment to be described here was conductedduring the period 11 January to 21 February 1956,except on Saturdays and Sundays. The

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R. Gelaro, R. Buizza, T. N. Palmer, and E. Klinker

1. Introduction It has long been proposed that advances in ensemble weather prediction can provide quantum improvements in assessing forecast skill and utility ( Leith 1974 ). In particular, a primary goal of creating an ensemble of forecasts is not only to produce a mean forecast that is more skillful than the control, but to quantify the uncertainty of the control forecast itself. For realistic models of the atmosphere such as those used at operational forecast centers, ensembles based on a

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Richard C. J. Somerville

ismodified by using a smooth field in the tropics in place of analyzed observed data, the skill of the prediction is degraded further, and the effect is apparent early in the 5-day period.These adverse tropical influences on middle-latitude forecast skill are essentially confined to the ultralong waves (zonal wavenumbers 1-3). They appear to be typical of hemispheric integrations with conventional numerical weather prediction models and conventional analysis and initialization techniques.The resulting

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Timothy DelSole and Ping Chang

power into a complete, uncorrelated set of components that optimize the predictive power. Schneider and Griffies call this procedure predictable component analysis. Apparently by coincidence, Déqué (1988) and Renwick and Wallace (1995) use the same name to describe a technique for determining “well-predicted” spatial patterns of forecast models. In these techniques, Déqué essentially minimized the total error variance, whereas Renwick and Wallace minimized the normalized error variance (J

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Roland J. Boucher and Raymond Wexler

motion are discussed, and an expression is derivedby taking into account advection and development. A series of objective tests on the line-motion predictability leads to a suggested technique for forecasting the arrival of a line at a particular poiiit.1. Introduction(1) The lines are invariably oriented in a directionclockwise from the 700-mb wind direFtioli;(2) The motions of the lines are significantlycorrelated with the 700-mb wind coniponcnts,with the correlation smaller at higher or

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