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Emily J. Becker, Ben P. Kirtman, Michelle L’Heureux, Ángel G. Muñoz, and Kathy Pegion

States, and Europe ( Ma et al. 2019 ; Madadgar et al. 2016 ; Thober et al. 2015 ), a global approach ( Mo and Lyon 2015 ), and a technique for categorical drought prediction ( Hao et al. 2017 ). Slater et al. (2019) and Slater and Villarini (2018) developed NMME-based hybrid streamflow predictions for the U.S. Midwest, and NASA’s hydrological forecasting and analysis system (NHyFAS), developed to support the U.S. Agency for International Development’s Famine Early Warning Systems network

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Donald S. Foster and Ferdinand C. Bates

A technique for forecasting the size of hailstones accompanying thunderstorms is presented. Hailstone size is related to its terminal velocity which in turn is related to the updraft velocity of a thunderstorm as derived from parcel buoyancy. This updraft velocity is approximated from positive area measurements on a thermodynamic diagram. The technique is tested on proximity soundings taken near the site and prior to known hail occurrences.

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Brian C. Ancell and Austin A. Coleman

improvements). These adjustment techniques, whether objectively calculated or performed subjectively by forecasters, benefit from the numerous long-distance relationships to flow features (e.g., troughs, jet streaks, or gradients) revealed trough ESA. Unlike adjoint sensitivity, which tends to exist at smaller scales and is less obviously associated with discernable flow features ( Ancell and Hakim 2007 ), ensemble sensitivity provides ample opportunity to make beneficial adjustments through the way it

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Brian A. Colle, Rosemary Auld, Kenneth Johnson, Christine O’Connell, Temis G. Taylor, and Joshua Rice

were clear, concise, and repeatable. Workshop 2: Matching message to audience and stakeholder interaction. The second workshop focused on communicating an extreme weather event to actual stakeholders from New York City and the Long Island area (e.g., emergency managers, heads of departments of transportation, media). The forecasters prepared a briefing slide for the event. The workshop started with a review of what the participants learned from the first workshop and the techniques they have

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Robert M. White and Agnes M. Galligan

Forecasts of the pressure-height variations at eight stations in the eastern United States are prepared by a statistical technique employing empirical influence functions. The accuracy of such forecasts is found to be comparable with that attained by synoptic techniques.

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Konstantine P. Georgakakos and Michael D. Hudlow

Quantitative hydrologic forecasting usually requires knowledge of the spatial and temporal distribution of precipitation. First, it is important to accurately measure the precipitation falling over a particular watershed of interest. Second, especially for small watersheds and/or for longer forecast lead times, forecasts of precipitation are critical to the achievement of the greatest possible hydrologic forecast accuracy and longest possible lead time. This paper describes the current hydrologic forecasting program of the U.S. National Weather Service (NWS) and highlights the relevance of Quantitative Precipitation Forecasting (QPF) products to real-time hydrologic forecasting. Specific requirements for QPF products in support of hydrologic forecasting applications are defined and current operational QPF procedures are reviewed to determine to what extent they meet these requirements. It is concluded that no known QPF procedures capable of fulfilling all desired requirements are currently available operationally, although much valuable QPF information is available to meet parts of these requirements. Some recent advances in mesoscale QPF research are examined and these techniques are treated in two categories: those uncoupled dynamically from and those dynamically coupled to hydrologic forecasting procedures. Finally, a summary of possible future directions toward achieving improved use of QPF information in hydrologic forecasting applications is presented.

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William H. Klein

The forecast research program of the Techniques Development Laboratory is summarized. This program combines dynamical, statistical, and synoptic techniques in an effort to improve and automate operational weather forecasting. Principal accomplishments of the Laboratory during the five years of its existence are described, and plans for future work are outlined. Weather elements for which forecast techniques are being developed include temperature, precipitation, humidity, wind, ceiling, visibility, severe local storms, wave heights, and storm surges.

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Myron K. Cox

A thunderstorm forecast technique is evaluated on a day by day basis during the months May through September, 1960. The over-all verification probability is 0.92. In a comparison test with persistence forecasts, the semi-objective method has a 24 per cent greater verification probability and shows more than thrice the skill factor.

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Lars van Galen, Oscar Hartogensis, Imme Benedict, and Gert-Jan Steeneveld

Weather forecasting is critical not only for social activities for the general public but also for transportation, energy supply, water management, agriculture, and many other crucial infrastructures and business decisions. Weather forecasts have become increasingly more accurate in recent decades due to improved numerical weather prediction (NWP) systems as a result of advances in understanding physical processes, data assimilation techniques, and computing capacity ( Bauer et al. 2015

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CAPTAIN Wilburn R. Schrank

The evaluation of the operational utility of new forecast techniques has presented meteorologists with a difficult problem for many years. Both the per cent correct score and the commonly used skill score possess rather serious limitations which are discussed in this paper. Finally, a new evaluation score is proposed which retains most of the good features of the other two scores but does not retain their primary limitations.

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