Showing papers in "Bulletin of the American Meteorological Society in 1980"
TL;DR: In this paper, the Mesoscale Convective Complex (MCC) is identified, defined, and contrasted with other types of convective weather systems, and a preliminary conceptual model of the life cycle of these systems is presented using enhanced, infrared satellite imagery in conjunction with conventional surface and radar data.
Abstract: A particular class of weather system, the Mesoscale Convective Complex (MCC) is identified, defined, and contrasted with other types of convective weather systems. It is found that MCC systems frequently occur over the central United States, grow to tremendous areal extent, and often persist for periods exceeding 12 h. In addition to widespread beneficial rains, a wide variety of severe convective weather phenomena attends these systems. The development and evolution of MCC systems is not explicitly predicted by operational numerical models even though they are shown to be organized in a distinctly non-random mode on scales that cannot be considered subgrid. The MCC is a convectively driven weather system whose physics are not yet understood, much less incorporated into operational parameterization schemes. A preliminary conceptual model of the life cycle of these systems is presented using enhanced, infrared satellite imagery in conjunction with conventional surface and radar data. The outlook f...
833 citations
TL;DR: In this paper, magnetic direction-finding (DF) stations have been installed throughout the western United States and Alaska to facilitate early detection of lightning-caused fires and in fire weather forecasting.
Abstract: Extensive networks of magnetic direction-finding (DF) stations have been installed throughout the western United States and Alaska to facilitate early detection of lightning-caused fires. Each station contains a new wideband direction-finder that responds primarily to cloud-to-ground lightning and discriminates against cloud discharges and background noise. Good angle accuracy is obtained by measuring the lightning direction at just the time the return-stroke electro-magnetic field reaches its initial peak. Lightning locations are calculated from the intersections of direction vectors and/or from the ratio of signal strengths recorded simultaneously at two, three, or four DF sites. The development of these systems has proved to be a significant aid in the detection of lightning-caused fires and in fire weather forecasting.
187 citations
TL;DR: In this article, a study of 79 residents of Eugene, Oreg., who completed a questionnaire designed to investigate their understanding of and attitude toward precipitation probability forecasts was conducted, finding that the event in question frequently is misunderstood, with both traditional precipitation forecasts and PoP forecasts producing similar levels of event misinterpretation.
Abstract: Previous studies have suggested that the general public misinterprets probability of precipitation (PoP) forecasts, leading some meteorologists to argue that probabilities should not be included in public weather forecasts. Upon closer examination, however, these studies prove to be ambiguous with regard to the nature of the misunderstanding. Is the public confused about the meaning of the probabilities or about the definition of the event to which the probabilities refer? If event misinterpretation is the source of the confusion, then elimination of the probabilities would not reduce the level of misunderstanding. The present paper summarizes a study of 79 residents of Eugene, Oreg., who completed a questionnaire designed to investigate their understanding of and attitude toward precipitation probability forecasts. Results indicate that the event in question frequently is misunderstood, with both traditional precipitation forecasts and PoP forecasts producing similar levels of event misinterpret...
133 citations
TL;DR: In this article, the Meteotron was used to generate a large thermal plume and three types of vortices were observed: large counter-rotating rolls in the downstream plume, small-scale vortice resembling very strong dust devils seen at the surface on the downwind side of the plume.
Abstract: Observations of vortices of various types produced in a large thermal plume are described. The apparatus used to generate the plume is the Meteotron, an array of 105 fuel oil burners with a total heat output of approximately 1000 MW. Three types of vortices have been observed: 1) large counter-rotating rolls in the downstream plume, 2) intense small-scale vortices resembling very strong dust devils seen at the surface on the downwind side of the plume, and 3) very large columnar vortices produced when the lower portion of the plume goes into rotation as a whole. Three mechanisms leading to the concentration of vorticity necessary to produce these vortex types are discussed. These include tilting and stretching of horizontal vorticity present in the environmental wind field, generation of vorticity within the plume by the action of buoyancy and drag forces, and convergence of preexisting background vorticity from the environment. It is concluded, based on these observations and physical considerat...
88 citations
TL;DR: In this article, it was shown that a single anemometer at a nonideal but reasonable location will usually provide adequate observational data to allow such a representative wind estimate after proper correction and data handling.
Abstract: Wind information for use at airports can be called representative if it provides an optimal estimate of wind variations to be expected over the runway. It is shown that a single anemometer at a nonideal but reasonable location will usually provide adequate observational data to allow such a representative wind estimate after proper correction and data handling. It follows from the properties of the surface wind field and of the instruments used to measure it that aeronautical wind averaging periods should be at least 2 min for mean winds and at least 5 s for gusts. Small-scale obstacle effects and measuring height variations can be dealt with by an objective exposure correction model. It is shown that the aggregate wind estimation error cannot be less than 10% because of the influence of spatial distance and reporting time lag. The employment of additional anemometers appears justified only by large-scale terrain influences such as mountains or sea breeze-inducing coastlines.
84 citations
TL;DR: In this paper, the authors describe typical synoptic-scale features for summertime severe thunderstorms on the High Plains, under conditions that are relatively benign in terms of conventional severe weather parameters.
Abstract: Typical synoptic-scale features are described for summertime severe thunderstorms on the High Plains. Severe weather generally occurs on several days in succession, under conditions that are relatively benign in terms of conventional severe weather parameters. Low-level conditions strongly resemble previously described convective flash flood situations. Moderate westerly flow is indicated at mid- and upper-levels, with the jet stream axis typically across or north of the threat area. Preexisting mesoscale systems often play a significant role in organizing the activity. Examples are shown, including one involving a thunderstorm outflow boundary.
61 citations
Journal Article•
TL;DR: The Summer Monsoon Experiment (MONEX) as mentioned in this paper was conducted over the Indian Ocean and adjacent land areas from May to August 1979, and overlapped with the second Special Observing Period of the Global Weather Experiment (FGGE).
Abstract: The Summer Monsoon Experiment (MONEX) which was conducted over the Indian Ocean and adjacent land areas from May to August 1979, and overlapped with the second Special Observing Period of the Global Weather Experiment (FGGE). Attention is given to the scientific goals of Summer MONEX which cover (1) planetary scale aspects, (2) synoptic scale aspects, (3) interactions with atmospheric circulation in the Pacific, Southern Hemisphere, Northern midlatitudes, and stratosphere, and (4) numerical simulation and prediction. The observing system and field operations designed to attain these goals are discussed in detail. In conclusion, it is noted that the combined MONEX and FGGE observations should provide an unprecedented data set for a basic study of the monsoon phenomena.
38 citations
TL;DR: The La Porte anomaly has been extensively studied and debated and has become a cause celebre in the interwoven areas of climate change, air pollution, weather modification, and the quality of climatic records as discussed by the authors.
Abstract: The anomalous behavior of the precipitation in northwestern Indiana (the La Porte anomaly) since the late 1930s has been extensively studied and debated. Local records suggested an upward shift in warm season rainfall, thunderstorms, and hail during the 1935–65 period. The possible causes for this included changed station exposure, a poor observer, urban influences on the atmosphere due to nearby Chicago, and/or shifts in the general circulation patterns. Most debate has centered on the observer error versus urban effects explanation, but the La Porte anomaly has become a cause celebre in the interwoven areas of climate change, air pollution, weather modification, and the quality of climatic records. A variety of recent studies of rainfall conditions and their areas of impact (streamflow, crop yields, and hail losses) show that the anomaly in the La Porte area began to shift locale in the 1950s and then disappeared in the 1960s. Taken in totality, it seems likely that the anomalous precipitation ...
36 citations
36 citations
TL;DR: In this paper, it was shown that even though a Doppler radar observes only the radial component of the wind, a wide variety of weather features of great importance to weather forecasters can easily be identified with a single radar.
Abstract: Single Doppler weather radar velocity and reflectivity fields have been obtained with the National Center for Atmospheric Research (NCAR) 5 cm radars for a wide variety of weather situations. Among those weather features that can be identified by means of color displays are the vertical variation of wind with height in widespread precipitation, frontal boundaries, gust fronts, “downbursts,” tornadoes, hurricane winds, wind shears dangerous to aircraft, and winds in the boundary layer in clear air. It is concluded that, even though a Doppler radar observes only the radial component of the wind, a wide variety of weather features of great importance to weather forecasters can easily be identified with a single radar. For operational applications a national network of Doppler radars seems justified. It is recommended, particularly in regions of the country where severe storms or high rainfall rates are relatively frequent, that these be 10 cm wavelength radars with a beam width of 1° and that automatic proce...
33 citations
TL;DR: The authors examined long-term records of forecasting performance for different types of precipitation forecasts in the National Weather Service for relative skill and secular trends in skill and found that the largest upward trends were achieved by local probability of precipitation (PoP) forecasts for the periods 24-36-hour and 36-48-hour after 0000 and 1200 GMT.
Abstract: All known long-term records of forecasting performance for different types of precipitation forecasts in the National Weather Service were examined for relative skill and secular trends in skill. The largest upward trends were achieved by local probability of precipitation (PoP) forecasts for the periods 24–36 h and 36–48 h after 0000 and 1200 GMT. Over the last 13 years, the skill of these forecasts has improved at an average rate of 7.2% per 10-year interval. Over the same period, improvement has been smaller in local PoP skill in the 12–24 h range (2.0% per 10 years) and in the accuracy of “Yea/No” forecasts of measurable precipitation. The overall trend in accuracy of centralized quantitative precipitation forecasts of ⩾0.5 in and ⩾1.0 in has been slightly upward at the 0–24 h range and strongly upward at the 24–48 h range. Most of the improvement in these forecasts has been achieved from the early 1970s to the present. Strong upward accuracy trends in all types of precipitation forecasts wit...
TL;DR: The NOAA Data Buoy Office (NDBO) buoys provide vital meteorological and oceanographic reports from data-sparse marine areas as discussed by the authors, and the scope and potential of the buoy system, the buoy network, monitoring capabilities, real-time processing and dissemination, archival data quality and availability, and future programs are described.
Abstract: The NOAA Data Buoy Office (NDBO) buoys provide vital meteorological and oceanographic reports from data-sparse marine areas. To provide a better understanding of the scope and potential of the buoy system, the buoy network, monitoring capabilities, real-time processing and dissemination, archival data quality and availability, and future programs are described.
TL;DR: The T-28 aircraft was specially modified to permit gathering in situ cloud physics and dynamics data from the interior regions of hailstorms as discussed by the authors, and a unique complement of instruments that measure and record hydrometeor sizes and concentrations has been assembled to provide observations of particle size spectra over the full range from cloud droplets to hailstones.
Abstract: A T-28 aircraft was specially modified to permit gathering in situ cloud physics and dynamics data from the interior regions of hailstorms. Since its first use in 1969, the T-28 instrumentation and data acquisition system has undergone evolutionary changes as newer instruments and more sophisticated electronic products have become available. A unique complement of instruments that measure and record hydrometeor sizes and concentrations has been assembled to provide observations of particle size spectra over the full range from cloud droplets to hailstones. The instrumentation and the data recording system are described in this paper, and planned future enhancements that will entail greater use of on-board computers are discussed.
TL;DR: In this article, a two-wavelength airborne lidar system has been constructed and field-tested to observe the distribution of particle concentrations over large regional areas, and the system was designed to detect the presence of particle particles over large regions.
Abstract: A new two-wavelength airborne lidar system has been constructed and field-tested. The system was designed to observe the distribution of particle concentrations over large regional areas. During a ...
TL;DR: In this paper, the evolution of the January 1978 midwestern blizzard-producing cyclone is described based on detailed surface analyses and National Meteorological Center (NMC) facsimile products.
Abstract: Based on detailed surface analyses and National Meteorological Center (NMC) facsimile products, the evolution of the January 1978 midwestern blizzard-producing cyclone is described. The behavior of the storm is contrasted with the actions of typical winter cyclones. Forecasts by the Limited-Area Fine Mesh (LFM) numerical model are compared with observed conditions. An injection of polar air, resulting in the revitalization of the baroclinic zone, and concurrent strong upper-air flow are found to be important factors in the dramatic intensification of the low. The movement and deepening of the low, although not unprecedented, were found to deviate substantially from normal winter cyclone behavior. Although LFM forecasts underestimated the deepening of the low, the amount of predicted intensification was substantial.
TL;DR: A cooling trend over the Northern Hemisphere since around 1940, amounting to over 0.5°C, due primarily to cooling at mid and high latitudes, has been presented and discussed as discussed by the authors.
Abstract: Evidence has been presented and discussed to show a cooling trend over the Northern Hemisphere since around 1940, amounting to over 0.5°C, due primarily to cooling at mid- and high latitudes. Some regions of the middle latitudes have actually warmed while others, such as the central and eastern United States, have experienced sharp cooling. A representative station for this latter region is Lafayette, Ind., which has recorded a drop of 2.2°C in its mean annual temperature from 1940 through 1978. The cooling trend for the Northern Hemisphere has been associated with an increase of both the latitudinal gradient of temperature and the lapse rate, as predicted by climate models with decreased solar input and feedback mechanisms. Observations and interpretation of sunspot activity have been used to infer a direct thermal response of terrestrial temperature to solar variability on the time scale of the Gleissberg cycle (∼90 years, an amplitude of the 11-year cycles). Measurements at the Greenwich Obser...
TL;DR: The University of Oklahoma (OU) Severe Storms Intercept Project-1979 as mentioned in this paper was conducted in conjunction with the spring field program of the National SEVERES Laboratory (NSSL), Norman, Okla., and the Severe Environmental Storms and Mesoscale Experiment (SESAME ‘79).
Abstract: The University of Oklahoma (OU) Severe Storms Intercept Project—1979 was conducted in conjunction with the spring field program of the National Severe Storms Laboratory (NSSL), Norman, Okla., and the Severe Environmental Storms and Mesoscale Experiment (SESAME ‘79). The purposes of the project were to provide NSSL with ground-based visual observations, in the field, of thunderstorms that were observed simultaneously by Doppler radar; to document and photograph severe-storm phenomena and related damage; and to obtain high-quality movies of tornadic debris clouds. A ground-based intercept crew consisting of four members operated from 1 April 1979 to 15 June 1979. The itineraries of the chase crews were usually determined jointly by the NSSL forecaster and the OU crew on the basis of conventional data from the service “A” and “C” teletypewriters, the National Facsimile Circuit (NAFAX), interpretation of satellite photographs, and data from both a conventional and a Doppler radar. Although the total number of...
TL;DR: A new national effort dealing with planned and inadvertent weather modification has been recommended as discussed by the authors, and the contention is that this readiness stems from finally learning important facts about how to properly design and conduct difficult experimentations; the need to study and understand ever growing inadvertent Weather modification; the development of complex instrumentation and growing expertise; and more awareness of the impacts of changing the weather.
Abstract: A new national effort dealing with planned and inadvertent weather modification has been recommended. The contention is that this readiness stems from finally learning important facts about how to properly design and conduct difficult experimentations; the need to study and understand ever growing inadvertent weather modification; the development of complex instrumentation and growing expertise; and more awareness of the impacts of changing the weather. Most importantly, awareness has come that progress can be made only through great attention to resolving many of the complex unknowns in the areas of cloud physics and dynamics. The potential benefits of an uncertain technology are difficult to specify, but appear sufficient to justify the research and development costs many have recommended. Either a better research program should be developed or we should essentially stop weather modification research.
TL;DR: In this paper, a meaoscale low pressure system or vortex formed in the lee of the Olympic Mountains as a deep Pacific storm moved ashore on central Vancouver Island, and the area of major destruction lay over and downwind of the region of extreme pressure gradient.
Abstract: Sustained winds in excess of 70 kt and gusts of close to 100 kt were measured at the Hood Canal Bridge in western Washington on the morning of 13 February 1979 shortly before the bridge collapsed. An extraordinary blowdown of timber also occurred in the nearby area. Elsewhere in western Washington maximum one-minute wind speeds were generally 40 kt or less and peak gusts were mostly under 65 kt. Wind damage was widespread but less concentrated than in the vicinity of the bridge. Use was made of all available routine and nonroutine data sources to analyze the cause of the unusual winds. The analysis revealed that a meaoscale low pressure system or vortex formed in the lee of the Olympic Mountains as a deep Pacific storm moved ashore on central Vancouver Island. The pressure gradient on the southeast side of the mesolow exceeded 5 mb over a distance of less than 10 n. mi. The area of major destruction lay over and downwind of the region of extreme pressure gradient. At the height of the storm the w...
TL;DR: The article of record as published may be found at http://dx.doi.org/10.1175/1520-0477(1980)061 2.0.CO;2
Abstract: The article of record as published may be found at http://dx.doi.org/10.1175/1520-0477(1980)061 2.0.CO;2
TL;DR: The Boundary Layer Instrument System (BLIS) as mentioned in this paper was designed for use from shipboard platforms in the GARP Atlantic Tropical Experiment (GATE) to monitor the thermal and kinematic properties of the boundary layer from approximately 100 m to the level of cloud base (800-1000 m).
Abstract: A tethered sonde, the Boundary Layer Instrument System (BLIS), was designed for use from shipboard platforms in the GARP Atlantic Tropical Experiment (GATE). This system was able to monitor the thermal and kinematic properties of the boundary layer from approximately 100 m to the level of cloud base (800–1000 m). Five levels were simultaneously sampled for periods up to 24 h in length. More detailed vertical structure measurements were obtained by raising and lowering the tethered balloon. The mechanical details of the system and its accuracy in monitoring boundary layer changes and vertical motions are described.
TL;DR: In this article, the authors compared satellite-derived monthly mean sea surface temperature anomalies with National Marine Fisheries Service (NMFS) ship-derived measurements over the North Pacific Ocean and found that the satellite-ship temperature difference between the overall monthly mean anomaly vacillated between +0.31°C and −0.30°C.
Abstract: Comparisons of satellite-derived monthly mean sea surface temperature anomalies with National Marine Fisheries Service (NMFS) ship-derived monthly mean sea surface temperature anomalies over the North Pacific Ocean reveal some encouraging results. Although still far from perfect, correlation coefficients for linear fits of 0.34, 0.49, 0.50, and 0.55 are observed for the winter months of November 1977, December 1977, January 1978, and February 1978, respectively. The standard error of estimate remained close to ±0.6°C and the satellite-ship temperature difference between the overall monthly mean anomaly vacillated between +0.31°C (December 1977) and −0.30°C (February 1978). Several other comparisons are presented. If the encouraging results of this study can be improved using improved sensor systems on the NOAA satellites, in addition to incorporating improved processing procedures, it would seem that we are now on the threshold of a more complete Earth monitoring system for at least one aspect of...
TL;DR: The findings of the Multiple Doppler Radar Workshop are summarized by a series of six papers as mentioned in this paper, including a review of the history of the workshop, fundamental concepts of doppler signal theory, and organization and objectives of the Workshop.
Abstract: The findings of the Multiple Doppler Radar Workshop are summarized by a series of six papers. Part I of this series briefly reviews the history of multiple Doppler experimentation, fundamental concepts of Doppler signal theory, and organization and objectives of the Workshop. Invited presentations by dynamicists and cloud physicists are also summarized. Experimental design and procedures (Part II) are shown to be of critical importance. Well-defined and limited experimental objectives are necessary in view of technological limitations. Specified radar scanning procedures that balance temporal and spatial resolution considerations are discussed in detail. Improved siting for suppression of ground clutter as well as scanning procedures to minimize errors at echo boundaries are discussed. The need for accelerated research using numerically simulated proxy data sets is emphasized. New technology to eliminate various sampling limitations is cited as an eventual solution to many current problems in Par...
TL;DR: A review of the research that has been accomplished on precipitation variability can be found in this paper, with a focus on the temporal and spatial variability of precipitation in the United States and Canada.
Abstract: The knowledge of the temporal and spatial variability of precipitation is important to many aspects of our society. A review of the research that has been accomplished on precipitation variability ...
TL;DR: The results of a 12-month study of this frost pocket are presented in this paper, where a standard National Weather Service instrument shelter with an extension beneath it was used to house a hygrothermograph and five maximum-minimum thermometers to acquire continuous temperature and relative humidity data.
Abstract: The Centre County Barrens is a region of anomalous temperature regimes in central Pennsylvania, which, under the proper weather conditions, can produce a month of subzero (°F less than −18°C) minimum temperatures per year and frost in midsummer. The results of a 12-month study of this frost pocket are presented. A standard National Weather Service instrument shelter with an extension beneath it was used to house a hygrothermograph and five maximum-minimum thermometers to acquire continuous temperature and relative humidity data and also to determine the maximum-minimum temperature gradient (envelope) of the lowest 1.5 m (5 ft). The data were then compared to those recorded at The Pennsylvania State University weather observatory. The temperature data were analyzed to compute monthly and yearly means. Diurnal and seasonal temperature cycles were examined to establish the similarities and differences between these two locations.
TL;DR: TIROS-N data for 21 October 1979 indicate a stronger jet and cyclone vortex at 250 mb in the eastern Pacific than is suggested by forecast continuity and aircraft winds as discussed by the authors.
Abstract: TIROS-N data for 21 October 1979 indicate a stronger jet and cyclone vortex at 250 mb in the eastern Pacific than is suggested by forecast continuity and aircraft winds. NOAA-6 data for 29 January ...
TL;DR: The value of climate data and the information derived from the data still seems to be an unknown to many as discussed by the authors, and the value of the data and its applications still seem to be unknown.
Abstract: The value of climate data and the information derived from the data still seems to be an unknown to many. Five persons engaged in providing climate services in different U.S. climatic zones have assembled a few widely different examples of recent uses of climate data and information. These help demonstrate the diversity of applications, and the value of the data and of those who can interpret them.