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Fujita, T. T.

Publications and source records attributed to Fujita, T. T..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Spearhead echo and downburst in the crash of an airliner

Meteorological conditions leading to the crash of an airliner short of the runway of a New York airport were studied. Thunderstorm downdrafts much stronger than those measured on the 1946-47 Thunderstorm Project were found. These exceptional downdrafts have been designated as 'downbursts'. The violent cloud systems that produce downburst cells can be identified in the form of forward extensions of radar echoes designed as 'spearhead echoes' which move with unusual speed. The development of downburst cells appears to be tied in with overshooting tops of clouds at the anvil level.

Fujita, T. T.↗
NASA NTRS1977

Thunderstorm-associated cloud motions as computed from 5-minute SMS pictures

The five-minute rapid-scan imagery from the Synchronous Meteorological Satellite is employed to study cloud motions associated with the Omaha tornado of May 6, 1975. Cloud-motion vectors derived from automated and man-machine interactive systems provide an account of the mesoscale phenomena. In addition to the geostationary satellite data, aerial photography obtained during a cloud-truth mission is used in the severe storm investigation. For tracking overland cumuli with short half-lives, a three-minute scan interval appears necessary for the satellite imagery.

Tecson, J. J.↗
NASA NTRS1977

Mesoanalysis of record Chicago rainstorm using radar, satellite, and raingauge data

Detailed surface rain and hail data are used to investigate the giant Chicago-area rainstorm of June 13, 1976, which caused up to seven inches of rain. The data provide an understanding of airflow patterns during the storm, and aid in developing proper interpretations of satellite and radar information on the storm. In particular, comparison of the rain and hail data with the satellite and radar imagery makes it possible to estimate the contributions of the two hydrometeors to the reflectivity. Furthermore, differences between the precipitation rate and the signal intensity are analyzed to infer the magnitude of vertical air motions.

Fujita, T. T.↗
NASA NTRS1977

Common denominator of three weather-related aircraft accidents

Three aircraft accidents are analyzed to gain an understanding of thunderstorm-related downbursts, or extremely rapid downdrafts, which interfered with takeoff or landing maneuvers in each of the three cases. For the purposes of this study, downbursts are defined as having downward speeds greater than 3.6 m/sec at 91 m altitude, and diameters of 800 m or greater. Few of the strongest downdrafts investigated reach the intensity of a downburst. The downburst cells mature about 5-10 minutes after formation, and are generally no more than 3-4 miles in diameter at maturity. A spearhead echo is found to be associated with each of the downburst-caused accidents.

Fujita, T. T.↗
NASA NTRS1977

Great Bend tornadoes of August 30, 1974

Photogrammetric analyses of movies and still pictures taken of the Great Bend, Kansas Tornado series have been used to develop design specifications for nuclear power plants and facilities. A maximum tangential velocity of 57 m/sec and a maximum vertical velocity of 27 m/sec are determined for one suction vortex having a translational velocity of 32 m/sec. Three suction vortices with radii in the 20 to 30 m range are noted in the flow field of one tornado; these suction vortices apparently form a local convergence of inflow air inside the outer portion of the tornado core.

Umenhofer, T. A.↗
NASA NTRS1977

Mesoanalysis of record Chicago rainstorm using radar, satellite, and rain-gage data

Comparison of cloud-top topography and rainfall rates at the surface revealed that the areas of heavy rain are located where there are depressions at the anvil top. It was also found that the Z-R relationships show a large scatter when vertical and/or horizontal air currents are strong. Results of this research led to Project NIMROD proposed to begin in May 1978.

Fujita, T. T.↗
NASA NTRS1976

Close-up view of 20 March 1976 tornadoes - Sinking cloud tops to suction vortices

The article describes an airborne mission using a Learjet to secure direct data on a family of tornadoes spawned by a rotating thunderstorm in the Missouri-Illinois-Indiana area in March 1976 following an unusually warm February. Weakening of the tornado following increased cloud-scale vertical motion, predicted by a model constructed by Fujita (1972), was confirmed. The aircraft inspected overshooting cloud tops, examined subsidence (holes and depressions) in anvil tops it overflew, and surveyed footprints left by the tornadoes and tornado-blown litter on the ground traversed by the disturbances. Subsidence of cloud tops in advance of violent tornadoes below was confirmed. Isolated and multiple suction vortices left their characteristic ground marks; three scales of motion: tornado cyclone, tornado, and suction vortex, are evidenced by the ground truth.

Fujita, T. T.↗
NASA NTRS1976

Spearhead echo and downburst near the approach end of a John F. Kennedy Airport runway, New York City

Radar echoes of a storm at John F. Kennedy International Airport are examined. Results regarding the phenomena presented suggest the existence of downburst cells. These cells are characterized by spearhead echoes. About 2% of the echoes in the New York area were spearhead echoes. The detection and identification of downburst cells, their potential hazard to approaching and landing aircraft, and communication of this information to the pilots of those aircraft are discussed.

Fujita, T. T.↗
NASA NTRS1975

Satellite-tracked cumulus velocities

Basic problems in the interpretation of satellite-tracked low-cloud velocities are reviewed. The METRACOM system of cloud velocity computation is outlined, and caution is urged in converting cloud velocities into wind velocities. The motion of various cumulus cells over Springfield, Mo., Barbados, and Tampa, Fla., is analyzed. It is shown that multiturret cells do not always move with the wind, that addition and deletion of turrets belonging to a specific cell may cause erratic motion in a tracer cell, and that cumulus turrets between 0.3 and 2 miles in size are the best targets for inferring the mean wind velocity within the subcloud layers. It is concluded that the accuracy of wind velocity estimates will be no better than 2 meters/sec unless the physical and dynamic characteristics of cumulus motion are further investigated.

Fujita, T. T.↗
NASA NTRS1975

Detection of severe storms by satellites

Ideas are presented for severe storm identification based on satellite data. The tops of huge thunderstorms in satellite pictures often appear as vast areas of extensive cirrus cloud; they consist of clusters of anvil clouds, each generated by vigorous thunderstorm circulation. The overshooting tops observed in satellite pictures are located where the subanvil updrafts are the strongest. Learjet experiment results show that an overshooting top varies either quickly or slowly, depending on the characteristics of individual clouds. When an overshooting top collapses, a small segment of the anvil cirrus jumps upward in the wake of the overshooting top. Also discussed is the monitoring of vertical motions from satellites and tornado-producing thunderstorms from geostationary altitude. A very high-resolution imagery of both infrared and visual spectral bands makes it possible to infer vertical motions beneath the anvil top. A combination of cloud velocity and anvil expansion rate will permit, in the future, determining the location of severe storms within the vast areas of anvil clouds.

Fujita, T. T.↗
NASA NTRS1974

Mesoscale wake clouds in Skylab pictures.

The recognition of cloud patterns formed in the wake of orographic obstacles was investigated using pictures from Skylab, for the purpose of estimating atmospheric motions. The existence of ship-wake-type wave clouds in contrast to vortex sheets were revealed during examination of the pictures, and an attempt was made to characterize the pattern of waves as well as the transition between waves and vortices. Examples of mesoscale cloud patterns which were analyzed photogrammetrically and meteorologically are presented.

Fujita, T. T.↗
NASA NTRS1974

Jumbo tornado outbreak of 3 April 1974

General meteorological data concerning the Jumbo tornado outbreak are presented. In terms of tornado number and total path mileage, it was more extensive than all known outbreaks. Most of the intense tornadoes avoided the large cities, however. Turn information is analyzed in detail. Left-turn tornadoes were more intense than right-turn tornadoes. Many important phenomena were observed, such as multiple suction vortices, family tornadoes, and cousin tornadoes spawned from interacting tornado cyclones. Aerial survey data will aid greatly in the solution of various scales of rotating motions, leading to improved prediction and warning of tornadoes.

Fujita, T. T.↗
NASA NTRS1974

Overshooting thunderheads observed from ATS and Learjet

Overshooting tops of thunderstorms were photographed simultaneously from both ATS and a Learjet during the cloud-truth experiment over the Midwest in the Spring of 1972 and 1973. The characteristics of overshooting tops were studied in various time and space scales, revealing that the horizontal dimensions of overshooting tops vary between 1000 ft and about 10 miles. The period of overshooting turrets with horizontal dimensions of less than 1 mile is found to be comparable to the Brunt-Vaisalla frequency of gravity waves at the lowermost stratosphere. The up-and-down motion of an overshooting dome, consisting of a number of turrets, is much slower than that of individual turrets. It is assumed that the height of a dome is closely related to the intensity of the up and downdrafts beneath the dome. Emphasis is placed upon the importance of the investigation of overshooting domes toward the identification of severe storm characteristics from satellites.

Fujita, T. T.↗
NASA NTRS1974

Superoutbreak tornadoes of April 3, 1974 as seen in ATS pictures

A total of 122 confirmed tornadoes during the April 3-4 superoutbreak is studied by conducting an extensive aerial survey for mapping the precise paths and characteristics of individual tornadoes. Major conclusions are that the life of a tornado varies between 1 and 125 min, that 74% of the tornadoes can be grouped together into 30 tornado families with the mean family life about 5 times the mean individual life, that the identification of family-producing thunderstorms appears to be extremely useful in issuing a tornado alert, and that a tornado-producing thunderstorm within a 50-mile radar range often shows a hook echo on PPI scope as a probable tornado indicator.

Fujita, T. T.↗
NASA NTRS1973

Satellite-tracked cumulus velocities

The research indicates that extreme caution must be exercised in converting cloud velocities into winds. The motion of fair-weather cumuli obtained by tracking their shadows over Springfield, Missouri revealed that the standard deviation in the individual cloud motion is several times the tracking error. The motion of over-ocean cumuli near Barbados clearly indicated the complicated nature of cumulus velocities. Analysis of whole-sky images obtained near Tampa, Florida failed to show significant continuity and stability of cumulus plumes, less than 0.3 mile in diameter. Cumulus turrets with 0.3 to 2 mile in size appear to be the best target to infer the mean wind within the subcloud layers. Cumulus or stratocumulus cells consisting of x number of turrets do not always move with wind. The addition and deletion of turrets belonging to a specific cell appear to be the cause of the erratic motion of a tracer cell. It may by concluded that the accuracy of wind estimates is unlikely to be better than 2m/sec unless the physical and dynamical characteristics of cumulus motion is futher investigated.

Fujita, T. T.↗
NASA NTRS1972

Tornado occurrences related to overshooting cloud-top heights as determined from ATS pictures

A sequence of ATS 3 pictures including the development history of large anvil clouds near Salina, Kansas was enlarged by NASA into 8X negatives which were used to obtain the best quality prints by mixing scan lines in 8 steps to minimize checker-board patterns. These images resulted in the best possible resolution, permitting use to compute the heights of overshooting tops above environmental anvil levels based on cloud shadow relationships along with the techniques of lunar topographic mapping. Of 39 heights computed, 6 were within 15 miles of reported positions of 3 tornadoes. It was found that the tornado proximity tops were mostly less than 5000 ft, with one exception of 7000 ft, suggesting that tornadoes are most likely to occur when overshooting height decreases. In order to simulate surface vortices induced by cloud-scale rotation and updraft fields, a laboratory model was constructed. The model experiment has shown that the rotation or updraft field induces a surface vortex but their combination does prevent the formation of the surface vortex. This research leads to a conclusion that the determination of the cloud-top topography and its time variation is of extreme importance in predicting severe local storms for a period of 0 to 6 hours.

Fujita, T. T.↗
NASA NTRS1971

Proposed characterization of tornadoes and hurricanes by area and intensity

Results of the 1968 through 1970 Tornado Watch Experiment conducted jointly by NASA and NOAA suggested the necessity of characterizing individual tornadoes in order to improve the identity of tornado-producing nephsystems. An attempt was made, therefore, to categorize each tornado by its intensity and area. Fujita-scale wind and corresponding damage categories were devised to classify tornadoes as Gale (F0), Weak (F1), Strong (F2), Severe (F3), Devastating (F4), and Incredible (F5). Additionally, individual tornado areas were also categorized as Trace (TR), Decimicro (DM), Micro (MI), Meso (ME), Marco (MA), Giant (GI), and Decagiant (DG), thus permitting characterizing of a tornado by a combination of intensity and area, such as weak decimicro tornado, severe meso tornado, or incredible giant tornado. A test characterization of 156 Japanese tornadoes in 1950-69 was accomplished for comparison with 893 U.S. tornadoes in 1965. Unexpectedly, the percentage distribution of intensity and individual area of U.S. and Japanese tornadoes is very similar except for large and/or intense ones. Intensity distribution within the Dallas and Fargo tornadoes of 1957 was also studied in detail. It was also found that the F-scale variation along the paths of family tornadoes shows an intensity oscillation with a 45-min interval.

Fujita, T. T.↗