Showing papers on "Thunderstorm published in 1970"

Satellite observations of lightning.

Abstract: Analysis of the positions of nighttime thunderstorms as determined from the detection of optical radiation by satellite OSO-B reveals that ten times as many lightning storms occur over land areas as over the sea.

Some Aspects of a Severe, Right-Moving Thunderstorm Deduced from Mesonetwork Rawinsonde Observations.

Abstract: On 24 May 1968 a rawinsonde observation was obtained in the updraft of a growing cell on the south flank of a thunderstorm which was turning to the right of winds and later produced large hail and funnel clouds. Moist adiabatic ascent was indicated with maximum excess temperature of 10C at 500 mb. Winds above 4.5 km deviated as much as 64° from environmental winds measured 15 n mi upwind. Diversion of mid-tropospheric flow is attributed to horizontal accelerators produced mainly by excess hydrostatic pressure within the updraft. At 5 km, a 23 m sec−1 updraft deduced from a hydrostatically-calculated ascent rate is one-third less than that obtained from an entraining jet model and two-thirds less than the parcel theory estimate. Excess hydrostatic pressure is considered as a contributing factor in reducing bouyancy. Although ambient vorticity through an attitude of 7 km was mostly anticyclonic, cyclonic rotation in the southwest portion of the storm was observed by radar and corroborated by visual...

Convective transport of mass and energy in severe storms over the United States—an estimate from a geostationary altitude

Abstract: Some important characteristics of intense convection associated with tornado vortices are described in a case study based on photographs of the United States on April 19 and 23, 1968, that were transmitted from NASA's geosynchronous satellite, ATS-3. The growth rates of a number of convection complexes as estimated from the satellite cloud photographs are studied. Based on a three-layer convection model, the upward fluxes of mass and energy in these severe storms are computed. The computed fluxes seem to be higher by at least one order of magnitude than in a moderate thunderstorm (Brown, 1967). It is suggested that the pronounced growth rate of a convection complex as estimated on the ATS-3 satellite photographs should be an indication of the presence of severe storm cells below the cirrus canopy. DOI: 10.1111/j.2153-3490.1970.tb00519.x

Weather Extremes Around the World

Abstract: : The report consists of a map of world and continental weather extremes and a map of North American weather extremes, with comments on the reliability of the records shown. Included are highest and lowest temperatures, largest temperature ranges, greatest and least amounts of precipitation for various durations, maximum precipitation variability, greatest thunderstorm frequency, highest and lowest atmospheric pressure, highest solar radiation, largest hailstones, greatest snowfall, highest wind speed, highest humidity, and most frequent occurrence of dense fog. Both the absolute extreme and the most extreme annual average are given for most of the elements. As far as possible, the records are taken from official sources, and all of them are documented. Conditions of site, instrumentation, observational procedure, and other factors pertinent to the reliability of extremes are discussed.

Radiometric Observations of Liquid Water in Thunderstorm Cells.

Abstract: An estimate of the integrated liquid water content along radio rays passing through a thunderstorm has been made by using the thermal emission from the storm at 10.7 GHz. The radiometric data, together with supplementary radar, radiosonde, and surface meteorological data are used to determine absorption in the storm, which in turn is used to determine the liquid water content. The results of the technique are illustrated by contour diagrams showing liquid water content of a small storm system and its changes over a period of 2 hr.

Accretion rates of cloud drops, raindrops, and small hail in mature thunderstorms

Abstract: Some “best estimates” of collision efficiencies, including the influence of charges and fields from zero to those found in mature thunderstorms, have been made and incorporated into calculations of instantaneous mass accretion rates of the full range of cloud drop and raindrop sizes, an embryonic hailstone, and two larger hail stones. The implication drawn from these calculations is that instantaneous particles mass growth rate in the continued quasi steady-state phase of precipitation growth in mature thunderstorms or electric fields of several hundred volts per centimeter can be speeded up by more than an order of magnitude by electrical forces when all particles involved are less than 100 μ. The effect decreases with increasing particle size.

The flashing behavior of thunderstorms

Abstract: The distribution in time of individual lightning flashes recorded visually during 20 storms in New Mexico and on 23-cm radar screens during several storms in the south-central United States has been analyzed. The logarithms of the intervals between flashes within a given storm are normally distributed with a standard deviation σ of approximately one natural-log unit. The available data do not reject the hypothesis that there are no statistically significant variations in σ among storms. The autocorrelation of the intervals between flashes in one storm is very small. The implications of these findings are briefly explored.

Hail and Lightning Occurrence in Mountain Thunderstorms

Abstract: The characteristics of northern Rocky Mountain thunderstorms with and without hail are compared on the basis of visual observations of hail at surface stations and electric field meter records of lightning frequency. Data from a sample of 25 thunderstorms in western Montana indicate that hailstorms generally produce lightning at a higher rate and for a longer period than storms without hail. The largest hailstones fell during the storm with most lightning activity.

Turbulence measurements in and near thunderstorms

Abstract: In May of 1969, the NAE T-33 participated in a co-operative program of storm turbulence measurement. During the program, the T-33 made several thunderstorm penetrations in the vicinity of Tinker Air Force Base, Oklahoma. The aim of the program was to explore turbulence characteristics in and near thunderstorms and to correlate aircraft turbulence measurements with a ground-based radar. Data recorded by the T-33 are used to compute true gust velocity time histories and to determine the variation in mean square gust velocities during the storm penetrations.

Flood peaks from small southwest range watershed

Abstract: RUNOFF ON THE 67-SQUARE-MILE ALAMOGORDO CREEK EXPERIMENTAL WATERSHED IN NORTHEASTERN NEW MEXICO IS GENERATED FROM STORM PRECIPITATION WITH GREATLY DIFFERING CHARACTERISTICS. THE LARGEST PEAK DISCHARGES OCCURRED FROM A COMBINATION OF CONVECTIVE HEATING AND WEAK SUMMER COLD FRONTS. THUNDERSTORMS WITHIN FRONTAL SYSTEMS HAVE PRODUCED LARGE PEAK DISCHARGES AND RUNOFF VOLUMES, WHEREAS THE LONG-DURATION SUMMER FRONTAL STORMS HAVE PRODUCED APPRECIABLE VOLUMES OF RUNOFF, BUT MUCH LOWER PEAK DISCHARGES. FOR A STORM DURATION OF LESS THAN SIX HOURS, THE POINT PRECIPITATION FREQUENCIES APPEAR TO BE HIGHER THAN THOSE PUBLISHED BY THE U.S. WEATHER BUREAU. THE DATA SHOW THE IMPORTANCE OF WATERSHED RAINFALL VALUES AS COMPARED TO SINGLE POINT VALUES. THE FIVE LARGEST RUNOFF EVENTS DURING THE 14-YEAR RECORD ARE COMPARED AND DISCUSSED IN RELATION TO PRECIPITATION DIFFERENCES. BY EXTRAPOLATION OF THE AVAILABLE DATA, USING A LOG-NORMAL FREQUENCY DISTRIBUTION, THE 20-YEAR FLOOD WAS ESTIMATED TO BE 8,700 CFS. /ASCE/

Hailstorms in the Kanto-Koshin District (2)

Abstract: The result of detailed analysis of the severe hailstorm of 7 June 1966 is presented. The storm caused more than 10 million dollar over wide area (Fig. 3). Synoptic conditions on this day were apparently favorable to the formation of severe convective storms in Kanto region (Fig. 1, 2, 13).Although the information concerning to hailstroms on this day was not sufficient to locate all individual hailclouds, behavior of some of these are investigated in detail. It seems that at least 10 individual hail clouds were formed on this day. These are grouped into 4 systems. One of the system (No. IV) moved relatively dense surface observational network, thus allowed detailed examination of its structure.This storm developed into an extraordinarily size, compared with most thunderstorms which develop in this area, within short time. The storm accompanied hail about 6 hours, the whole life time was more than 7 hours. Severe to moderate hail-damage occurred along its path for a continuous belt of 150km in length. Very intense rain was observed. 35.0mm in 10 minutes was an official record at the site of the Japan Meteorological Agency. Stronger rain, perhaps up to 50mm/10min, . might occur at some areas in Saitama Prefecture, north of Tokyo. Distribution of surface weather at 8pm shown in Fig. 10, reaveals that the storm structure was very much similar to a SR-storm dicsussed by Browning (1964). An interesting event occurred between 8pm and 9pm, namely, at 9pm the storm was already a squall mesosystem (Fujita, 1963) with several cells, some of them accompanied hail and intense rain. The transition form a single cell structure to a multi-cell system was apparent. It seems this change was related to weakening of the whole convective storm unit. Unfortunaely it was not possible to examine the course of this change because PPI pictures were available about one hour intervals. Most of the other hail clouds were small and the lack of data prevented detailed study of these storms.

A Center for the Description of Environmental Conditions. Weather Phenomena

Abstract: : -B-81-A-00ECOM0083-14See Annual progress rept. no. 4, AD-739 544.*Atmospherics, *Thunderstorms, *Data processing, Data acquisition, Data reduction, Pattern recognition, Spectrum signatures, Weather forecasting, Meteorological instruments, Very low frequency, Clouds, Magnetic detectors, Atmospheric electricity, Computer programs, Clear air turbulence, Tornadoes, Weather modificationThemis projectA summary of results is made in this Final Report. Five major categories of information about severe storm sferics and severe storm characterizations are presented: (1) Statistical Descriptions of Lightning as a VLF Source; (2) Model Studies of Cloud and Sferic Behavior; (3) Hardward Developments; (4) Software Developments; and (5) Results of a Cumulus Cloud Magnetic Field Survey. It is concluded that VLF sferics has no intrinsic predictive content. However, sferic behavior is closely correlated with cloud development and vigor and thus has very high indicative content. A method for examining the electric current motions within a cumulus cloud by sensing the resulting magnetic field is shown to be feasible. (Author)

A system for measuring the electrical currents to the earth during thunderstorm conditions

Abstract: A system was developed to continuously measure the current to the Earth from conduction, precipitation, and convection during thunderstorm conditions » The total current to an isolated earth-filled collecting plate in the plane of the Earth's surface was measured« Displacement current was electronically substracted from the total current. The experimental site was located at the USCCS Magnetic Observatory about eight miles east of The University of Arizona, Tucson, Arizona * A. summary is given for measurements that were taken during four different periods of thunderstorm conditions «