Showing papers on "Nowcasting published in 1986"
TL;DR: In this article, an overview of some conceptual models that are useful for nowcasting is given, which represent a variety of systems associated with midlatitude cyclones and also mesoscale convective systems in the tropics and midlatitudes.
Abstract: Imagery from radars and satellites is one of the main ingredients of nowcasting. When used to provide very detailed forecasts of precipitation for a few hours ahead, the imagery needs to be interpreted carefully in terms of synoptic and mesoscale phenomena and their mechanisms. This paper gives an overview of some conceptual models that are useful for this purpose. The models represent a variety of systems associated with midlatitude cyclones and also mesoscale convective systems in the tropics and midlatitudes. Specific phenomena discussed are warm conveyor belts, including those with rearward- and forward-sloping ascent in ana and kata cold frontal situations, respectively; cold conveyor belts ahead of warm fronts; narrow rainbands associated with line convection at the boundary of a pre-cold-frontal low-level jet; wide mesoscale rainbands associated with midtropospheric convection; squall lines in the tropics and midlatitudes; nonsquall mesoscale convective systems in the tropics and midlatitu...
160 citations
01 Jan 1986
TL;DR: In this paper, the authors use the term nowcast to describe the ability of the forecaster to assimilate great quantities of weather data, conceptualize a model of the environment, and extrapolate this forward in time.
Abstract: Short-range forecasting or nowcasting is based upon the ability of the forecaster to assimilate great quantities of weather data, conceptualize a model of the environment, and extrapolate this forward in time. Frequently this is done just to describe existing conditions, and thus has the term “now-cast” originated. Since the time scales are essentially the same for short-range forecasting and nowcasting (the same processes are used for both), the terms are used here interchangeably.
26 citations
31 Jul 1986
TL;DR: In this article, the authors used pencil-beam Doppler weather radar data, combined with on-airport ground clutter measurements, to analyze the performance of the six-level weather channel in the next generation airport surveillance radar, the ASR-9.
Abstract: : In this report, we use pencil-beam Doppler weather radar data, combined with on-airport ground clutter measurements, to analyze the performance of the six-level weather channel in the next generation airport surveillance radar, the ASR-9 A key tool was a computer procedure that used these data to simulate the output of the ASR-9's weather channel, including effects of the radar's fan-shaped elevation beams, short coherent processing intervals and ground clutter filters Our initial analysis indicates that: (a) the combination of high-pass Doppler filters and spatial/temporal smoothing should normally prevent ground clutter from having a significant effect on the controllers' weather display; (b) the spatial/temporal smoothing processor will result in weather contours that are statistically stable on a to-scan basis, reinforcing controller confidence in the validity of the data; (c) relative to the coarse resolution imposed by use of the NWS levels, accurate two-dimensional parameterizations of storm reflectivity can be estimated Our assessment indicates that the ASR-9's weather reflectivity maps should be reliable The radar will be widely deployed at significant air terminals, and will provide a combination of high update rate and large volumetric coverage not available from other sensors These attributes should lead the ASR-9 becoming an important component of the Federal Aviation Agency's modernized weather nowcasting system
8 citations
TL;DR: In this paper, the authors used the diagnosed divergence initialization procedure of Tarbell et al. (1979) to predict the hourly rainfall data used in short-term precipitation forecasts, and compared it to nondivergence or observed-divergence initializations.
Abstract: Use of the diagnosed-divergence initialization procedure of Tarbell et al. (1979) to predict the hourly rainfall data used in short-term precipitation forecasts is examined experimentally. Data simulations using a mesoscale model and balanced and internally consistent data were conducted; the physical and numerical characteristics of the mesoscale model are described. The real experiment used rainfall data from April 25-26, 1979 to investigate the capabilities of the initialization procedure to improve short-term precipitation forecasts. The derivation of the diagnosed-divergent wind using a mesoscale omega equation which includes the effects of latent heating is discussed. The diagnosed-divergence initialization forecasts are compared to nondivergence or observed-divergence initializations. It is observed that the diagnosed-divergence initializations provide better rainfall data than the other initializations.
4 citations
01 Jan 1986
TL;DR: In this article, the authors define nowcasting as the extrapolation of current weather to some future time, based on the behavior of existing phenomena as described by intensive observations, and very short-range forecasting is the anticipation of events beyond the period during which extrapolation usually works but not beyond 12 hours.
Abstract: Computer displays are especially useful for nowcasting and very-shortrange forecasting of regional and local weather events. Nowcasting is the extrapolation of current weather to some future time, based on the behavior of existing phenomena as described by intensive observations. Extrapolation is considered to involve no physics, dynamics, or the application of numerical or conceptual models. How long it is successful depends heavily upon the phenomenon itself, the location, and, more than likely, the season. Very-short-range forecasting is the anticipation of events beyond the period during which extrapolation usually works but not beyond 12 h. These definitions, proposed by Zipser (1983), are adopted here.
1 citations