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Mar M. Flexas, Martina I. Troesch, Steve Chien, Andrew F. Thompson, Selina Chu, Andrew Branch, John D. Farrara, and Yi Chao

is derived from hourly output from operational forecasts performed with the NCEP 5-km North American model (NAM). Tidal forcing obtained from the TPXO.6 global barotropic tidal model ( Egbert and Erofeeva 2002 ) is added through lateral boundary conditions. An essential component of this system is the new two-step multiscale three-dimensional variational data assimilation (MS-3DVAR) scheme used to generate the three-dimensional ocean state estimates, a generalization of the 3DVAR methodology of

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Reza Marsooli, Philip M. Orton, George Mellor, Nickitas Georgas, and Alan F. Blumberg

future water level based on multiple numerical predictions conducted using perturbed physical parameters and initial conditions (e.g., Zou et al. 2013 ). Operational ensemble flood forecast systems require over a 100 simulations every forecast cycle to robustly address worst-case scenario metrics like the 10% chance exceedance flood (e.g., Forbes et al. 2014 ). These systems are increasingly being utilized because they are more valuable for decision support than deterministic forecasting systems

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Elizabeth J. Thompson, Steven A. Rutledge, Brenda Dolan, V. Chandrasekar, and Boon Leng Cheong

1. Introduction and background Reducing uncertainty associated with winter storm precipitation type, accumulation, and timing is a major forecasting, safety, and socioeconomic challenge ( Ralph et al. 2005 ; Kringlebotn Nygaard et al. 2011 ; Smith et al. 2012 ). These rapidly evolving mesoscale systems will be better understood with the national dual-polarization radar upgrade through use of hydrometeor classification algorithms (HCAs; Liu and Chandrasekar 2000 ; Zrnić et al. 2001 ; Park

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Nicolas Gaussiat, Robin J. Hogan, and Anthony J. Illingworth

supercooled water with an LWP of about 20 g m −2 , but their presence in the liquid rather than the ice phase can lead to shortwave flux changes of about 100 W m −2 . Accurate observations of liquid water path are needed to evaluate the representation of liquid water clouds in global circulation models (GCMs) used for forecasting future climate and for numerical weather prediction (NWP). In most operational NWP models, production of rain by collision and coalescence is parameterized by an autoconversion

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S. N. Londhe and Vijay Panchang

model. In section 3 , we provide a brief review of the modeling strategy. Modeling results are presented in section 4 along with a discussion of the reliability of the predictions and the identification of the limitations of this technology. Section 5 provides some results of a real-time implementation of the model with a view to providing operational online forecasts in the future. Concluding remarks are given in section 6 . 2. Study area and data For the present work, data from six buoys

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Valérian Jewtoukoff, Riwal Plougonven, Albert Hertzog, Chris Snyder, and Glen Romine

order of several tens of kilometers. This uncertainty seriously reduces the places on Earth where such OSB flights can occur, as well as the flight opportunities during a flight campaign, since the larger the uncertainty, the wider the landing polygon. The time scale for such balloon flights is associated with the horizontal travel of several tens of kilometers. Common operational practice consists of forecasting balloon trajectories from forecasts produced with a global NWP model, for example, from

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R. Rabin and I. Zawadzki

attention to problems inherent in radar measurements. A method is suggested tominimize the effects of beam smoothing and refiectivity weighting. A case study indicates the possibility ofoperational short-term forecasting of the onset time of precipitation from the radar measurements of divergence.1. Introduction The possibility of obtaining the kinematic propertiesof airflow from single-Doppler radar observations hasbeen of interest for a number of years. In an earlywork, Browning and Wexler (1968

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Hyun-Sook Kim, Carlos Lozano, Vijay Tallapragada, Dan Iredell, Dmitry Sheinin, Hendrik L. Tolman, Vera M. Gerald, and Jamese Sims

and Chen (2012) have demonstrated in their numerical studies that two-way interaction must be included, in order to improve atmosphere and ocean forecast skill. Based on the analysis of the 11-yr storm guidance performance of the operational Geophysical Fluid Dynamics Laboratory (GFDL) hurricane–ocean model, Bender et al. (2007) have concluded that skill improvement in hurricane intensity forecast can be also be improved by accurate initialization of ocean mesoscale features. Toward having a

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Robert Atlas, Ross N. Hoffman, Zaizhong Ma, G. David Emmitt, Sidney A. Wood Jr., Steven Greco, Sara Tucker, Lisa Bucci, Bachir Annane, R. Michael Hardesty, and Shirley Murillo

ECMWF T511 (~26-km horizontal resolution) NR ( Andersson and Masutani 2010 ). The most recent of these OSSEs, to assess the potential impact of the proposed Global Wind Observing Sounder (GWOS) mission, were conducted by Riishojgaard et al. (2012) and Ma et al. (2015) . The DA system used in the GWOS experiments was the operational NCEP Global Data Assimilation System (GDAS; Kleist et al. 2009 ) circa 2009. This system included the Global Forecast System (GFS) running at a resolution of T382

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Valliappa Lakshmanan, Robert Rabin, Jason Otkin, John S. Kain, and Scott Dembek

these features have been parameterized in forecast models, rather than explicitly represented on the model grid (e.g., Sundqvist et al. 1989 ; Janjic 1990 ). However, in recent years, increases in computer power have allowed operational NWP centers to increase spatial resolution and explicitly resolve more key processes, such as deep precipitating convection, which were previously parameterized (e.g., Weiss et al. 2008 ; Dixon et al. 2009 ). This transition has allowed for the development of new

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