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William H. Klein, Billy M. Lewis, and Isadore Enger

PredictionUnit (JNWP) in Suitland, Maryland (Staff Members,19.57). At the same time, forecasting by statisticalmethods has been made feasible by the increasedavailability of high-speed electronic computers, andencouraging results have been obtained by severalgroups working under the leadership of Malone (1956),Lorenz (1956), and White (1957). In the present paper,an attempt will be made to combine both dynamicaland statistical techniques to derive an objective methodof predicting 5-day mean surface

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John O. Roads

and diverge ata great rate from the true state on the average, the similarity of sequential forecasts lends greater confidenceto the final forecast. This similarity of forecasts can be developed evenfurther through the application of statistical techniques.Statistical weights can be attached to forecasts thatshould describe the contribution by individual forecaststo the total lagged average. The latest forecast will havethe greatest weight but due to random analysis errorsit has been thought

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Irving I. Gringorten and Norman Sissenwine

: The production of rain and drizzle by coales cence in stratiform clouds. Quart. J. I. meteor. SOC., 78, p. 377.CORRELATION COEFFICIENTS AND PREDICTION ACCURACY Irving I. Gringorten and Norman SissenwineAir Force Cambridge Research Center, Bedford, Massachusetts (Manuscript received 2 November 1959)If one uses a "least square estimate" technique asa means of predicting a future (or distant) weatherparameter, the root-mean-square error in this prediction increases monotonically toward that

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Rupa Kamineni, T. N. Krishnamurti, S. Pattnaik, Edward V. Browell, Syed Ismail, and Richard A. Ferrare

/National Environmental Satellite, Data, and Information Service (NESDIS) operational real-time analysis files that were based on weekly averages (preceding the initial state for each storm) and included datasets from surface ships, buoys, and satellite-derived estimates. Several techniques have been developed to assess the influence of new datasets for the analysis/forecast issues. In this study, the data-denial experiment (DDE) procedure was used to assess the impact of new datasets on hurricane analysis and

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A. Stohl, O. R. Cooper, and P. James

. Different data assimilation techniques exist, the most advanced of which use variational algorithms ( Courtier and Talagrand 1987 ). The variant used at ECMWF is four-dimensional ( White 2002 ), where during a certain period of time (currently 12 h) the model forecast is adjusted iteratively to minimize a so-called cost function, a measure of the deviation between the forecast and the observations. During that period, the meteorological fields evolve in a dynamically consistent manner. Analyses are the

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Edward M. Carlstead

air is best resolved onthese surfaces. Namias [6] states that, from availableobservations, isentropic surfaces appear to be substantial surfaces (it?., surfaces that contain the sameparticles from day to day), to a first approximation.Starr E113 suggested that CAV trajectories mightbetter be depicted on an isentropic chart than on aconstant level chart, as there are no solenoids onisentropic surfaces. It would then seem that the technique of forecasting future positions of particles byCAV

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John A. Knox, Donald W. McCann, and Paul D. Williams

regarding our focus on the source, not the far-field propagation, of gravity waves: operational CAT forecasting algorithms have never attempted to forecast CAT by predicting the motion of gravity wave trains (e.g., ray-tracing techniques). Practical considerations have always limited forecasting approaches to the hypothesis that aircraft encounter turbulence near regions of strong forcing. This may be surprising to dynamicists, but it is still the state of the art in CAT forecasting and therefore was

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R. S. Scorer

initial, predicted and finally observed northwardvelocity at 500 mb at 4S0N, reveals that as good aFERRUARY 195 1C`O R RESPO N DEN CE69forecast as his could be obtained by advecting .theinitial values. Sutcliffe's technique of using the geostrophic equation in the process of calculating thehorizontal divergence from the vorticity field is thesame as Dr. Charney's (filtering technique, but Sutcliffe finds no need to consider the signal velocity in hismethod which is primarily a forecasting method

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Manuel Pulido

determine the error produced by the unresolved motions. First, the use of short-range forecasts started from analyses so that the model errors are not spread and time superposed between them. Second, it makes use of knowing the response of the equations to the momentum errors so that a dynamic variable, potential vorticity, is used in the technique in which the response to the momentum errors is local. The technique works optimally if it is applied in a data assimilation cycle. The paper is organized as

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W. Lawrence Gates

techniques andprocedures have been devised to overcome some ofthe difficulties encountered in forecasting with thebarotropic model over a large area. These include theuse of objective analysis, truncation-error control andsmoothing procedures, and the incorporation of somenon-geostrophic effects. The present series of integrations, however, was deliberately made by a directapplication of the procedures used in earlier, smallerarea forecasting with the "unadorned" barotropicmodel, and might therefore be

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