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Madalina Surcel, Isztar Zawadzki, and M. K. Yau

-scale ensemble forecasting (SSEF) system developed at the Center for the Analysis and Prediction of Storms (CAPS; Xue et al. 2008 ; Kong et al. 2008 ). While the ensemble configuration has changed throughout the years, each year a set of members with perturbed initial conditions (IC) and lateral boundary conditions (LBC), different model physics, and mesoscale data assimilation (DA; including radar) was produced. The ICs and LBCs for these members were derived from the operational short-range ensemble

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Masakazu Taguchi

Forecasts subseasonal (2–6 week) hindcast (HC) data. They showed that the skill of 1000-hPa NAM forecasts is enhanced not only when they were initialized during periods of anomalously weak events of the stratospheric polar vortex (i.e., MSSWs) but also when they were initialized during periods of anomalously strong events. Mukougawa et al. (2009) analyzed Japan Meteorological Agency (JMA) 1-month operational forecast data and showed that the upper-tropospheric NAM is better forecasted for lead times

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R. Buizza and A. Montani

the target area defined using singular vectors evolving along a trajectory started from the analysis or started from the 24-h forecast started one day before are very close. Concerning the number of singular vectors, small differences have been detected between targets defined using either 4 or 10 singular vectors. Thus, our sensitivity analysis suggests that real-time targeting is feasible, despite operational constraints as the fact that only a forecast state can be used to start a singular

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Robert W. Jones

large-scale atmospheric motion.Similar techniques for reliable forecasts of smallscale disturbances like the hurricane have not beenperfected for operational use. To date, several modelshave been tried experimentally for operational forecasts, by vl7. Hubert (1957), L. Hubert (1959) andVandermaii (1959) at the Joint Numerical WeatherPrediction unit in Suitland, Mar).land, and byinvestigators at Japan's numerical weather-predictioncenter, but none of these models has been highlycompetitive with

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Craig H. Bishop, Carolyn A. Reynolds, and Michael K. Tippett

determine forecast and analysis error covariance ( Lorenz and Emanuel 1998 ; Palmer et al. 1998 ; Berliner et al. 1999 ; Baker and Daley 2000 ; Bishop et al. 2001 ). In operational settings, model error, poorly specified observation error covariances together with the prohibitive computational expense of running an extended Kalman filter or smoother (e.g., Jazwinski 1970 ) severely limit our ability to accurately estimate analysis and forecast error covariance. To gain insight into how flow

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Edward M. Carlstead

significance was obtained,an examination of the data shows that it is the datafrom trajectories constructed on isentropic charts thatare better .It is gratifying to note that the greatest improvement was shown in the wind-direction forecasts for48 hr. In much operational forecasting, wind direction is usually deemed more important than windspeed, since the proper location of troughs, ridges andassociated weather patterns depends greatly on correctwind-direction forecasts. Therefore, from results obtained

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Henk Eskes, Arjo Segers, and Peter van Velthoven

and Atmospheric Administration (NOAA) has recently started to provide ozone forecasts based on assimilated operational data from the NOAA satellites. The Data Assimilation Office of NASA has developed the Goddard Earth Observing System (GEOS) ozone data assimilation system for the offline analysis of Total Ozone Mapping Spectrometer (TOMS) and Solar Backscatter UV (SBUV/2) data ( Štajner et al. 2001 ). The University of Reading, in collaboration with the Met Office, has developed an ozone data

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Richard C. J. Somerville

resolution, they undertook an investigation of the effect of an equatorial wall in a highresolution model with elaborate parameterizedphysics. The model was the spectral version of the15-level primitive-equation operational model of theEuropean Centre for Medium Range Weather Forecasts truncated triangularly at wavenumber 63. Incomparing global and hemispheric forecasts in anensemble of eight cases, Bengtsson et al. employedas a measure of skill the "useful predictability,"defined as the length of time

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Xuguang Wang and Craig H. Bishop

of the breeding techniques. In other words, the ensemble spread of the ETKF ensemble is better able to distinguish the case-to-case forecast uncertainty than the breeding ensembles. Besides the superior ensemble forecast skills of the ETKF scheme over the breeding schemes, the computational expense of the ETKF is also quite small (<6% more than the breeding ensemble). Thus, the ETKF ensemble generation scheme would be straightforward to employ operationally. When applied to operational forecast

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

equations to heights obtained from barotropic prognoses would have produced temperaturepredictions of positive skill during the test winter of 1957-58.The forecasts can be considerably improved by including as a predictor the local value of 5-day meansurface temperature for a period 4 days earlier than the forecast period. When this term was combinedwith the barotropically-estimated heights, objective temperature predictions comparable in accuracy toconventional forecasts were made by multiple

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