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Martin Weissmann, Florian Harnisch, Chun-Chieh Wu, Po-Hsiung Lin, Yoichiro Ohta, Koji Yamashita, Yeon-Hee Kim, Eun-Hee Jeon, Tetsuo Nakazawa, and Sim Aberson

forecasts by different models is presented in section 3 , followed by a discussion of the influence of T-PARC observations on ECMWF forecasts in midlatitudes over the Pacific and on the Northern Hemisphere in section 4 . The discussion and conclusions are presented in section 5 . 2. Model descriptions a. JMA GSM experiment description To evaluate the impact of the T-PARC 2008 special observations, experiments using the operational global 4D-Var system and the operational JMA global spectral model

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Maxi Boettcher and Heini Wernli

realistic model setting. And finally, it is unclear how well operational forecast models predict the generation, propagation, and intensification of a DRW. A first study dealing with this issue has been performed for the storm Lothar by Kenzelmann (2005) . They analyzed the 50 simulations of the ECMWF ensemble prediction system and identified a strong sensitivity of the track and intensity of the mature storm to its structure and position relative to the jet axis during the DRW propagation phase

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Florian Harnisch and Martin Weissmann

collaboration with T-PARC, the Taiwanese Astra Jet was operated under the research program Dropwindsonde Observations for Typhoon Surveillance near the Taiwan Region (DOTSTAR), where dropsonde observations are deployed operationally on TCs that pose a threat to the Taiwanese island ( Wu et al. 2005 , 2007b ). This study investigates the benefit of T-PARC dropsonde observations in different locations on the basis of data denial experiments with the European Centre for Medium-Range Weather Forecasts (ECMWF

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Kirstin Kober, Annette M. Foerster, and George C. Craig

1. Introduction The skill of numerical forecasts of convective precipitation is limited by several sources of uncertainty that can be minimized, but never completely removed. The initial and the boundary conditions for the model integration have limited accuracy and additionally physical processes have to be approximated and truncated to the model’s grid. Furthermore, the atmosphere is chaotic and the physical nature of convection stochastic. Ensembles of different model integrations and their

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Julia H. Keller

and Torn 2008 ) and was successfully applied to investigate the effect of initial condition uncertainty (or perturbations) on short-range ensemble forecasts (e.g., Hawblitzel et al. 2007 ; Sippel and Zhang 2008 ; Torn and Hakim 2008 ; Torn 2010a , b ; Torn and Cook 2013 ) or for revealing the dynamical and physical dependencies in operational medium-range ensemble forecasts (e.g., Schumacher 2011 ; Chang et al. 2013 ; Zheng et al. 2013 ). The studies by Harr and Dea (2009) and Keller et

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Julia H. Keller, Sarah C. Jones, and Patrick A. Harr

analysis data, available at 10 and more pressure levels (referred to as vertical output resolution in the remainder). However, data from the operational ECMWF EPS is only available at nine pressure levels. Vertical velocity, which is crucial for the computation of the baroclinic conversion (cf. section 2c ), is only available at six pressure levels. This requires determination as to whether the coarse vertical output resolution of the ECMWF EPS forecast data is sufficient to adequately define the K e

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Marlene Baumgart, Michael Riemer, Volkmar Wirth, Franziska Teubler, and Simon T. K. Lang

. Res. , 101 , 1435 – 1456 , https://doi.org/10.1029/95JD02674 . 10.1029/95JD02674 Bauer , P. , A. Thorpe , and G. Brunet , 2015 : The quiet revolution of numerical weather prediction . Nature , 525 , 47 – 55 , https://doi.org/10.1038/nature14956 . 10.1038/nature14956 Boer , G. J. , 1984 : A spectral analysis of predictability and error in an operational forecast system . Mon. Wea. Rev. , 112 , 1183 – 1197 , https://doi.org/10.1175/1520-0493(1984)112<1183:ASAOPA>2.0.CO;2 . 10

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Julian F. Quinting, Michael M. Bell, Patrick A. Harr, and Sarah C. Jones

) showed that operational global numerical models do not properly simulate these structural changes. However, the dynamical processes that are associated with these structural changes perturb the midlatitude flow. In idealized simulations Riemer et al. (2008) showed that these complex perturbations to the midlatitude flow may result in a baroclinic downstream development. Real case ensemble forecasts indicate that initially small perturbations may lead to plumes of forecast uncertainty in downstream

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Tobias Selz and George C. Craig

gravity waves radiating from convective regions in upscale growth or errors will be discussed. 2. Experimental design This study employs a nonhydrostatic limited-area atmospheric model provided by the Consortium for Small-Scale Modeling (COSMO) ( Baldauf et al. 2011 ). It has been applied for many years by the German Meteorological Service [Deutscher Wetterdienst (DWD)] for operational forecasting with a 7-km grid spacing (COSMO-EU) and a 2.8-km grid spacing (COSMO-DE). In the higher

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Julia H. Keller, Christian M. Grams, Michael Riemer, Heather M. Archambault, Lance Bosart, James D. Doyle, Jenni L. Evans, Thomas J. Galarneau Jr., Kyle Griffin, Patrick A. Harr, Naoko Kitabatake, Ron McTaggart-Cowan, Florian Pantillon, Julian F. Quinting, Carolyn A. Reynolds, Elizabeth A. Ritchie, Ryan D. Torn, and Fuqing Zhang

transport, which may impact both the occurrence frequency and predictability of subseasonal regimes on basin to hemispheric length scales. The Subseasonal to Seasonal Project database ( www.s2sprediction.net ; Vitart et al. 2017 ), which provides access to subseasonal to seasonal forecasts from 11 operational centers, could be a valuable resource for such investigations. On still longer time scales, the influence of a warming climate on the downstream impact of ET, in particular, is another aspect that

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