Navy Operational Global Atmospheric Prediction System Research Articles

Assimilation of Synthetic Tropical Cyclone Observations into the Navy Operational Global Atmospheric Prediction System

Abstract In June 1990, the assimilation of synthetic tropical cyclone observations into the Navy Operational Global Atmospheric Prediction System (NOGAPS) was initiated at Fleet Numerical Oceanography Center (FNOC). These observations are derived directly from the information contained in the tropical cyclone warnings issued by the Joint Typhoon Warning Center (JTWC) and the National Hurricane Center. This paper describes these synthetic observations, the evolution of their use at FNOC, and the details of their assimilation into NOGAPS. The results of a comprehensive evaluation of the 1991 NOGAPS tropical cyclone forecast performance in the western North Pacific are presented. NOGAPS analysis and forecast position errors were determined for all tropical circulations of tropical storm strength or greater. It was found that, after the assimilation of synthetic observations, the NOGAPS spectral forecast model consistently maintained the tropical circulations as evidenced by detection percentages of 96%, 90% ...

Sensitivity Studies of the Navy's Global Forecast Model Parameterizations and Evaluation of Improvements to NOGAPS

Abstract The purpose of this paper is to discuss the major systematic errors of the U.S. Navy Operational Global Atmospheric Prediction System (NOGAPS), version 3.2, and to describe several tuning experiments of NOGAPS parameterizations. It is found that despite its overall good performance, major systematic errors exist in the forecast model. These errors lead to a warmer atmosphere with less precipitation and eddy kinetic energy than is observed. Some of the errors may be attributed to the lack of horizontal and vertical resolution, but most of the errors are due to inadequacies and incorrect assumptions in the physical parameterizations. We present a list of the systematic errors of the operational 5-day forecasts and results of a 1-yr integration with climatological sea surface temperatures. One of the prominent features of NOGAPS integrations is a large diurnal oscillation in the global mean averages. This oscillation is traced to large differences in total albedo over the land and sea areas. We pres...

An Evaluation of the Real-Time Tropical Cyclone Forecast Skill of the Navy Operational Global Atmospheric Prediction System in the Western North Pacific

The paper evaluates the meteorological quality and operational utility of the Navy Operational Global Atmospheric Prediction System (NOGAPS) in forecasting tropical cyclones. It is shown that the model can provide useful predictions of motion and formation on a real-time basis in the western North Pacific. The meterological characteristics of the NOGAPS tropical cyclone predictions are evaluated by examining the formation of low-level cyclone systems in the tropics and vortex structure in the NOGAPS analysis and verifying 72-h forecasts. The adjusted NOGAPS track forecasts showed equitable skill to the baseline aid and the dynamical model. NOGAPS successfully predicted unusual equatorward turns for several straight-running cyclones.

The Design and Testing of the Navy Operational Global Atmospheric Prediction System

Abstract The Navy Operational Global Atmospheric Prediction System (NOGAPS) has proven itself to be competitive with any of the large forecast models run by the large operational forecast centers around the world. The navy depends on NOGAPS for an astonishingly wide range of applications, from ballistic winds in the stratosphere to air-sea fluxes to drive ocean general circulation models. Users of these applications will benefit from a better understanding of how a system such as NOGAPS is developed, what physical assumptions and compromises have been made, and what they can reasonably expect in the future as the system continues to evolve. The discussions will be equally relevant for users of products from other large forecast centers, e.g., National Meteorological Center, European Centre for Medium-Range Weather Forecasts. There is little difference in the scientific basis of the models and the development methodologies used for their development. However, the operational priorities of each center and t...

The Navy's Operational Atmospheric Analysis

Abstract In January of 1988, significant upgrades were made to the Navy Operational Global Atmospheric Prediction System (NOGAPS). Among these improvements was the implementation of a multivariate optimum interpolation analysis scheme. Since that time, this analysis scheme has been improved and expanded to satisfy almost all of the navy's atmospheric analysis requirements. In this paper, we describe the global database available for analysis, the techniques currently used to produce the NOGAPS analyzed fields, and the modification required for other applications.

The Description of the Navy Operational Global Atmospheric Prediction System's Spectral Forecast Model

We present a description of the development of the spectral forecast components of the Navy Operational Global Atmospheric Prediction System (NOGAPS). The original system, called 3.0, was introduced in January 1988. New versions were introduced in March 1989 (3.1) and August 1989 (3.2). A brief description of each version of the forecast model is given. Each physical parameterization is also described. We discuss the large changes in 3.1 and the motivation behind the changes. Statistical results from forecast comparison tests are discussed. Figures showing the total monthly forecast performance in the Northern Hemisphere and the Southern Hemisphere are also given. A brief discussion is presented of computational details, running times, and memory requirements of the forecast model.

Evaluation of the Surface Prognoses of Cyclones and Anticyclones of the JMA and FNOC Models over East Asia and the Western Pacific during the 1983 Mei-Yu Season

Abstract This study compares the systematic errors of 36-h surface cyclone and anticyclone forecasts for two operational numerical weather prediction models over East Asia and the western North Pacific Ocean: the U.S. Navy's Operational Global Atmospheric Prediction System (NOGAPS), and Japan Meteorological Agency's Fine-mesh Limited Area Model (JFLM). The study is carried out for the 1983 Mei-Yu season (May–July), which is the wettest season over East Asia based on nontyphoon-produced rainfall. All available 0000 and 1200 GMT forecast runs are evaluated against an independent dataset of subjective analysis produced operationally by the Central Weather Bureau, Taipei. The mean position errors, mean central pressure errors and forecast skill indices for both cyclones and anticyclones in the NOGAPS and JFLM models are examined. Both NOGAPS and JFLM models are more likely to underforecast than to overforecast the existence and/or genesis of both cyclones and anticyclones. However, over the Tibetan Plateau an...

An operational evaluation of the Navy Operational Global Atmospheric Prediction System (NOGAPS): 48-hour surface pressure forecasts : Toll, R.F. Jr. and W.M. Clune, 1985. Mon. Weath. Rev., 113(9):1433–1440

An operational evaluation of the Navy Operational Global Atmospheric Prediction System (NOGAPS): 48-hour surface pressure forecasts : Toll, R.F. Jr. and W.M. Clune, 1985. Mon. Weath. Rev., 113(9):1433–1440

An Operational Evaluation of the Navy Operational Global Atmospheric Prediction System (NOGAPS): 48-Hour Surface Pressure Forecasts

Abstract The second in a series of studies designed to identify systematic pressure, displacement, and directional errors in the 48-hour surface pressure forecast of extratropical cyclones by the Navy Operational Global Atmospheric Prediction System (NOGAPS) has been completed for the 1983 Northern Hemisphere winter season (5 January–31 March). All available NOGAPS 0000 and 1200 GMT forecast cycles are verified for the Western Pacific, Eastern Pacific, and Atlantic Oceans north of the equator. NOGAPS generally underforecasts the intensity of cyclones during their early stages, but overforecasts them during their mature and decaying phase. NOGAPS was slow in forward movement but showed improvement over the previous Navy forecast model. Case studies are presented which illustrate typical pressure and speed error patterns and the possible consequences of an inferior analysis on forecast quality. The results of this study correspond closely with the conclusions derived from the preliminary evaluation.