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Douglas R. Allen, Lawrence Coy, Stephen D. Eckermann, John P. McCormack, Gloria L. Manney, Timothy F. Hogan, and Young-Joon Kim

1. Introduction A research project at the Naval Research Laboratory (NRL) has extended the Navy Operational Global Atmospheric Prediction System (NOGAPS) spectral forecast model from its current 1.0-hPa upper boundary to include a fully resolved prognostic middle atmosphere ( Eckermann et al. 2004 ). This work is ongoing: the goal is to progressively transition aspects of this new NOGAPS-Advanced Level Physics and High Altitude (NOGAPS-ALPHA) to the Fleet Numerical Meteorological and

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L. M. Druyan, T. Ben-Amram, Z. Alperson, and G. Ohring

forecasts)uses operational VTPR temperature profiles transmitted over the global meteorological telecommunicationssystem in January 1976. In both sets of experiments the VTPR soundings are used to enhance the initialanalyses over the Atlantic Ocean. Parallel forecasts with and without the VTPR data are verified againstoperational analyses over a region that includes most of Europe, the Middle East and North Africa. Theresults indicate that, on the average, there is a small improvement in the forecasts

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Sim D. Aberson and Mark DeMaria

National Hurricane Center(NHC) until 1989. Beginning that year, the VICBARmodel (DeMaria et al. 1992, hereafter D92) has beenused for operational track prediction in the North Atlantic basin. One reason that barotropic models continue to beused for track prediction is that they have skill comparable to that of baroclinic models for forecasts toabout 48 h (D92). Forecasts are skillful because tropical cyclones tend to form in low latitudes and in environments where there is little vertical variation

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H. Liu and X. Zou

data impact studies using the U.S. Navy and National Weather Service forecast models showed an approximate 10% reduction in the mean 2-day forecast errors over the NORPEX forecast verification region (NORPEX.FVR) from the inclusion of targeted dropsonde data in the operational data assimilation system ( Langland et al. 1999 ; Szunyogh et al. 1999b ). Analyses were used for forecast verification in these studies. However, a few 48-h forecasts were found to have been degraded by the addition of the

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C. Eric Williford, T. N. Krishnamurti, Ricardo Correa Torres, Steven Cocke, Zaphiris Christidis, and T. S. Vijaya Kumar

outperforms the FSU GSM, which is run at a lower resolution, and the regional model has demonstrated some improved skills in predicting tropical cyclone intensities. Operationally for the public, a charter of the National Hurricane Center (NHC) in Miami is to provide forecasts in real time for the Atlantic, Caribbean, and Gulf of Mexico hurricanes and other tropical systems. The experienced forecasters at NHC receive real-time forecasts from a number of leading operational modeling groups from the United

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JACK D. TRACY

June 1966Jack D. Tracy407ACCURACY OF ATLANTIC TROPICAL CYCLONE FORECASTS JACK D. TRACYNational Hurricane Research Laboratory, Environmental Science Services Administration, Miami, Fla. ABSTRACT During the past several years a number of techniques have been developed for forecasting the motion of tropicalcyclones over areas of the Atlantic, Caribbean, and Gulf of Mexico. Many of these have been tested on an opera-tional basis. These forecasts have been

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GORDON E. DUNN, R. CECIL GENTRY, and BILLY M. LEWIS

the spring of 19.59 when the latter moved its headquartersfrom West Palm Beach to Miami into offices adjacent to thosc occupied by the principal hurricane forecast office inthe United States. Results now available from verification of forecasts made during the period 1954 through 1966show t,hat there hns been a significant improvement in the accuracy of hurricane forecasts during the period of in-creased cooperation between the research and operational forecasting groups. This improvement is

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F. Zhang, Chris Snyder, and Richard Rotunno

cyclone were not exceptional, the precipitation forecast by the operational models running at the National Centers for Environmental Prediction (NCEP) posed a serious challenge for forecasters in the affected region. Figure 1 shows the 24-h observed accumulated precipitation in liquid water content between 1200 UTC 24 and 1200 UTC 25 January 2000, the corresponding operational Eta Model forecast, and the research-model forecast (both models were initialized at 0000 UTC 24 January 2000). Except for

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Jeffrey L. Anderson

1. Introduction Because it is impossible to measure precisely the current state of the atmosphere and because numerical prediction models are only approximations of the true atmospheric dynamics, it is natural to view the task of predicting the future state of the atmosphere in a stochastic framework. In recent years, the world’s operational atmospheric prediction centers have increasingly tended to view the forecast problem in this light. This has led to the development of ensemble prediction

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R. J. RENARD, S. G. COLGAN, M. J. DALEY, and S. K. RINARD

tropical cyclones for forecast intervals upto 72 hr. The MOHATT scheme involves steering of thecenter of the cyclone by geoTtrophic wind9 derived fromheavily smoothed isobaric height fields (both analyzed andprognostic) and a statistical correction determined by thebehavior of the first 12 hr of the steering forecast. Thedevelopmental sample (1967-70) used to establish thepotential accuracy of MOHATT indicates 700 mb as theoptimum steering level, but the fully operational test in1971 suggests that the

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