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Irving I. Gringorten

significant skills in a series of forecasts? How can we decideconclusively that one system of forecasting is betterthan another? In addition to these problems, there isthe problem of setting forth a procedure to sample aforecast method just often enough to rate the technique as successful or inferior, without necessarily demanding a long-term program for the trial testing ofthe technique.In this article, the familiar 95 per cent confidencelimit is discussed with respect to any program of verification in

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Sim D. Aberson and Brian J. Etherton

presented in section 2 . Section 3 provides descriptions and results of conventional and ensemble-based data assimilation techniques on forecasts from a barotropic hurricane track forecast model. Implications and conclusions are presented in section 4 . 2. Operational surveillance results a. Techniques To assess the impact of the surveillance missions on operational numerical forecasts, the version of the NCEP Global Data Assimilation System (GDAS) operational at the time of the missions was used

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P. J. Roebber and A. A. Tsonis

observed data (including some variables that are not observed at all), missing data, inaccuracies in the data, and imperfect analysis techniques. All of these errors, even with a perfect model, will grow nonlinearly over time, eventually swamping the forecast signal ( Lorenz 1963 , 1965 , 1969 ). The rate of this error growth and hence the lead time at which predictability is lost depends on the stability of the evolving flow ( Lorenz 1965 ), which in addition is affected by factors such as the large

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C. Cardinali and R. Buizza

published literature (e.g., Palmer et al. 1998 ) for a discussion of similarities and differences among these techniques. Targeting techniques also include the quasi-inverse linear method ( Pu et al. 1997 , 1999 ) and the ensemble transform Kalman filter (ETKF) [ Bishop et al. (2001 ), the ETKF had been used operationally as targeting guidance during the 2000, 2001, and 2002 WSR missions]. This study explores the forecast impact results from the assimilation of targeting dropsondes during NORPEX, one

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Tomislava Vukicevic, Eric Uhlhorn, Paul Reasor, and Bradley Klotz

’s (2013) study was based on subjective estimates by the forecasters, whereas in Torn and Snyder’s (2010) study a lower bound of BT error variance has been estimated objectively using a relatively large sample of differences between BT values for which the aircraft reconnaissance measurements were considered, and the intensity estimates that were based only on the empirical techniques using passive remote sensing observations (the Dvorak techniques; Velden et al. 2006 ; Knaff et al. 2010 ). When

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Eugeune J. Aubert

verticallinear interpolation between the specific humidity atthe standard reporting levels. Likewise, the saturation specific humidity was determined from the average temperature of a 400-mb layer. Both of thesecomputational techniques can have a modifying effecton the degree of saturation at the initial time. Eventhough the initial condensation was computed atisolated points, this does not appear to have caused aserious error in the later precipitation forecasts. Thethree-dimensional flow pattern rapidly

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Richard A. Craig, Chester W. Newton, R. Robert Rapp, and Robert O. Reid

--analysis- and forecast-oriented scientists, including not only forecasters but also scientistswho develop techniques applicable to forecasting problems, and analyses that clarify the structure andbehavior of the atmosphere; JAM--applications-oriented scientists in fields such as instrumentation, weathermodification, atmospheric pollution, agriculture andforestry, transportation and commerce, and otherhuman activities where a substantial meteorologicalinput is required; JPO--scientists in the broad fieldof

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Peter M. Norris and Arlindo M. da Silva

paid to predicted cloud properties, due to the slower time scales associated with cloud-induced radiative heating rates compared with the forecast duration. Nevertheless, clouds do have an important societal impact from day to day, in terms of their effects on diurnal temperature range and sunlight exposure. Furthermore, since NWP and GCM models have become more merged, typically sharing the same physics, advances in cloud parameterization in either climate or weather studies ought to benefit the

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David Kuhl, Istvan Szunyogh, Eric J. Kostelich, Gyorgyi Gyarmati, D. J. Patil, Michael Oczkowski, Brian R. Hunt, Eugenia Kalnay, Edward Ott, and James A. Yorke

and the fast propagation speed indicate that the dominant error pattern takes the shape of a packet of synoptic-scale Rossby waves. This conclusion can be confirmed by calculating the packet envelope of the forecast errors for the 4- to 9-wavenumber range with a Hilbert transform-based method ( Zimin et al. 2003 , 2006 ). Using the technique of Zimin et al. (2006) , Fig. 6 depicts an amplifying eastward-extending envelope of errors. An inspection of the vertical cross section of the errors

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Florence Seaver Mulkern and Duane S. Cooley

50JOURNAL OF METEOROLOGY VOLUME 18VERIFICATION OF STATISTICAL HEMISPHERICAL PREDICTIONSFlorence Seaver Mulkern and Driartc S. Cooley *Geophysics Research Directorate, Air Force Rest I- Division (Manuscript received 9 May 1960)ABSTRACTA statistical procedure for forecasting the 500-mb contour height at grid points around the hemisphere isverified. Coefficients of Tschebycheff polynomials are used as predictors, and these are tested on an independent data sample. The results indicate

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