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Christian Jakob

The parameterization schemes used to represent clouds in general circulation models have significantly evolved in their complexity over the last 10 yr. This increases the demand for a thorough evaluation of their performance. Several techniques ranging from the evaluation of the model climate to single column modeling have been proposed for that purpose. This paper aims to provide a strategy for an improved, more coherent use of these techniques. An overview of the different techniques is given using examples from the evaluation of the global model of the European Centre for Medium-Range Weather Forecasts. Advantages and disadvantages of the individual methods are highlighted. The paper closes by proposing a strategy to join the different techniques into a coherent procedure of cloud parameterization evaluation.

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Joseph T. Schaefer, James P. Travers, Thomas A. Heffner, A. Dale Eubanks, Armando L. Garza, Lans P. Rothfusz, Walter A. Rogers, Sylvia K. Graff, James T. Skeen, Kenneth Haydu, and M. Lee Harrisons

The National Weather Service sponsored a workshop on aviation weather on 10–12 December 1991, in Kansas City, Missouri. The theme of the workshop was the improvement of service to the aviation community through the application of technology and advanced forecast techniques. The 150-plus people who attended the workshop included a cross section of operational forecasters, pilots, research meteorologists, and representatives of the aviation industry. The workshop included sessions on user requirements, operational procedures, and the impacts of new technology on the forecast products. There were also four “hands-on” laboratory sessions where participants produced various types of aviation weather products. The interaction between the user community and working-level forecasters made the workshop a unique event.

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John S. Kain, Paul R. Janish, Steven J. Weiss, Michael E. Baldwin, Russell S. Schneider, and Harold E. Brooks

Collaborative activities between operational forecasters and meteorological research scientists have the potential to provide significant benefits to both groups and to society as a whole, yet such collaboration is rare. An exception to this state of affairs is occurring at the National Severe Storms Laboratory (NSSL) and Storm Prediction Center (SPC). Since the SPC moved from Kansas City to the NSSL facility in Norman, Oklahoma in 1997, collaborative efforts between researchers and forecasters at this facility have begun to flourish. This article presents a historical background for this interaction and discusses some of the factors that have helped this collaboration gain momentum. It focuses on the 2001 Spring Program, a collaborative effort focusing on experimental forecasting techniques and numerical model evaluation, as a prototype for organized interactions between researchers and forecasters. In addition, the many tangible and intangible benefits of this unusual working relationship are discussed.

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James W. Wilson, N. Andrew Crook, Cynthia K. Mueller, Juanzhen Sun, and Michael Dixon

This paper reviews the status of forecasting convective precipitation for time periods less than a few hours (nowcasting). Techniques for nowcasting thunderstorm location were developed in the 1960s and 1970s by extrapolating radar echoes. The accuracy of these forecasts generally decreases very rapidly during the first 30 min because of the very short lifetime of individual convective cells. Fortunately more organized features like squall lines and supercells can be successfully extrapolated for longer time periods. Physical processes that dictate the initiation and dissipation of convective storms are not necessarily observable in the past history of a particular echo development; rather, they are often controlled by boundary layer convergence features, environmental vertical wind shear, and buoyancy. Thus, successful forecasts of storm initiation depend on accurate specification of the initial thermodynamic and kinematic fields with particular attention to convergence lines. For these reasons the ability to improve on simple extrapolation techniques had stagnated until the present national observational network modernization program. The ability to observe small-scale boundary layer convergence lines is now possible with operational Doppler radars and satellite imagery. In addition, it has been demonstrated that high-resolution wind retrievals can be obtained from single Doppler radar. Two methods are presently under development for using these modern datasets to forecast thunderstorm evolution: knowledge-based expert systems and numerical forecasting models that are initialized with radar data. Both these methods are very promising and progressing rapidly. Operational tests of expert systems are presently taking place in the United Kingdom and in the United States.

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Robert S. Arthur

The adequacy of existing forecasting techniques is demonstrated for a situation involving extreme wave conditions on the northern shores of the Hawaiian Islands. Computations of wave characteristics as made from Sverdrup and Munk's revised relationships show that this unusually high swell could be forecast more than 24 hours in advance. Travel time is computed on the basis of the group velocity at the end of the decay distance. The situation affords a particularly good check on computed travel time since the time of maximum wave height is observed at both the Hawaiian and Palmyra Islands.

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R. M. Whiting

An attempt is made to relate the occurrence and the location of Tornado activity to areas of intense surface warm advection as indicated by the isobars and isotherms on the sea level chart. The degree of cross-isotherm flow is classified by the packing of the thermal field and the temperatures in it along with the strength and direction of flow as indicated by the isobars to determine short range forecasting patterns. The method presented is limited in that it is not applicable to all tornado situations and is offered as a supplementary technique which could serve to raise the confidence level of short range tornado forecasts based on upper air parameters.

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James L. Buizer, Josh Foster, and David Lund

It has been estimated that severe El Niño-related flooding and droughts in Africa, Latin America, North America, and Southeast Asia resulted in more than 22 000 lives lost and in excess of $36 billion in damages during 1997–98. As one of the most severe events this century, the 1997–98 El Niño was unique not only in terms of physical magnitude, but also in terms of human response. This response was made possible by recent advances in climate-observing and forecasting systems, creation and dissemination of forecast information by institutions such as the International Research Institute for Climate Prediction and NOAA's Climate Prediction Center, and individuals in climate-sensitive sectors willing to act on forecast information by incorporating it into their decision-making. The supporting link between the forecasts and their practical application was a product of efforts by several national and international organizations, and a primary focus of the United States National Oceanic and Atmospheric Administration Office of Global Programs (NOAA/OGP).

NOAA/OGP over the last decade has supported pilot projects in Latin America, the Caribbean, the South Pacific, Southeast Asia, and Africa to improve transfer of forecast information to climate sensitive sectors, study linkages between climate and human health, and distribute climate information products in certain areas. Working with domestic and international partners, NOAA/OGP helped organize a total of 11 “Climate Outlook Fora” around the world during the 1997–98 El Niño. At each Outlook Forum, climatologists and meteorologists created regional, consensus-based, seasonal precipitation forecasts and representatives from climate-sensitive sectors discussed options for applying forecast information. Additional ongoing activities during 1997–98 included research programs focused on the social and economic impacts of climate change and the regional manifestations of global-scale climate variations and their effect on decision-making in climate-sensitive sectors in the United States.

The overall intent of NOAA/OGP's activities was to make experimental forecast information broadly available to potential users, and to foster a learning process on how seasonal-to-interannual forecasts could be applied in sectors susceptible to climate variability. This process allowed users to explore the capabilities and limitations of climate forecasts currently available, and forecast producers to receive feedback on the utility of their products. Through activities in which NOAA/OGP and its partners were involved, it became clear that further application of forecast information will be aided by improved forecast accuracy and detail, creation of common validation techniques, continued training in forecast generation and application, alternate methods for presenting forecast information, and a systematic strategy for creation and dissemination of forecast products.

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Leonard W. Snellman

Changes in the hemispheric zonal wind-profile were used at the USAF South Ruislip Weather Central in England as one forecast tool to help in constructing prognostic charts for 48 hours and occasionally for 96 hours. The successes and failures of this technique during the period February to October 1952 are discussed. Suggestions for the improvement of its use on a daily basis are put forth.

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James P. Jenrette

An objective method of forecasting Gulf stratus clouds at Bryan Air Base, Texas in the summer season is developed using the scatter-diagram technique. The parameters used are (1) resultant wind direction, (2) resultant pressure-gradient magnitude, (3) Houston temperature-dew-point spread, (4) Bryan dew point, and (5) Bryan temperature-dew-point spread. Based on one year of independent data and four years of dependent data, the skill scores are 0.55 and 0.70 respectively.

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David W. Reynolds and Eric A. Smith

A technique is developed to digitally composite satellite and radar imagery in a common coordinate reference frame. Results obtained from using Geosynchronous Operational Environmental Satellite (GOES) visible and infrared data, 5 cm radar data, and recording raingage data are presented. The composite displays are created on Colorado State University's All Digital Video Imaging System for Atmospheric Research (ADVISAR), an interactive image processing system that uses modern high fidelity digital video display technology. An efficient methodology based on analytic transforms for remapping dissimilar digital image formats into common map projections is discussed. Applications of multi-sensor composite images are demonstrated with the use of two case studies. The technique is shown to enhance our understanding of a) convective development, b) organization of mesoscale features as they relate to the synoptic scale, c) severe storm development, and d) precipitation mechanisms. Our final comments concern the compositing technique's potential for on-line interactive forecast systems, particularly in terms of an embedding approach.

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