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Steven C. Albers, John A. McGinley, Daniel L. Birkenheuer, and John R. Smart

Abstract

The Local Analysis and Prediction System combines numerous data sources into a set of analyses and forecasts on a 10-km grid with high temporal resolution. To arrive at an analysis of cloud cover, several input analyses are combined with surface aviation observations and pilot reports of cloud layers. These input analyses am a skin temperature analysis (used to solve for cloud layer heights and coverage) derived from Geostationary Operational Environmental Satellite IR 11.24-µm data, other visible and multispectral imagery, a three-dimensional temperature analysis, and a three-dimensional radar reflectivity analysis derived from full volumetric radar data. Use of a model first guess for clouds is currently being phased in. The goal is to combine the data sources to take advantage of their strengths, thereby automating the synthesis similar to that of a human forecaster.

The design of the analysis procedures and output displays focuses on forecaster utility. A number of derived fields are calculated including cloud type, liquid water content, ice content, and icing severity, as well as precipitation type, concentration, and accumulation. Results from validating the cloud fields against independent data obtained during the Winter Icing and Storms Project are presented.

Forecasters can now make use of these analyses in a variety of situations, such as depicting sky cover and radiation characteristics over a region, three-dimensionally delineating visibility and icing conditions for aviation, depicting precipitation type, rain and snow accumulation, etc.

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Roy Rasmussen, Marcia Politovich, John Marwitz, Wayne Sand, John McGinley, John Smart, Roger Pielke, Steve Rutledge, Doug Wesley, Greg Stossmeister, Ben Bernstein, Kim Elmore, Nick Powell, Ed Westwater, B. Boba Stankov, and Don Burrows

Field studies in support of the Winter Icing and Storms Project (WISP) were conducted in the Colorado Front Range area from 1 February to 31 March 1990 (WISP90) and from 15 January to 5 April 1991 (WISP91). The main goals of the project are to study the processes leading to the formation and depletion of supercooled liquid water in winter storms and to improve forecasts of aircraft icing. During the two field seasons, 2 research aircraft, 4 Doppler radars, 49 Mesonet stations, 7 CLASS sounding systems, 3 microwave radiometers, and a number of other facilities were deployed in the Front Range area. A comprehensive dataset was obtained on 8 anticyclonic storms, 16 cyclonic storms, and 9 frontal passages.

This paper describes the objectives of the experiment, the facilities employed, the goals and results of a forecasting exercise, and applied research aspects of WISP. Research highlights are presented for several studies under way to illustrate the types of analysis being pursued. The examples chosen include topics on anticyclonic upslope storms, heavy snowfall, large droplets, shallow cold fronts, ice crystal formation and evolution, and numerical model performance.

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