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On July 27, 1963, a storm produced rainfall intensities that exceeded prior records for Tulsa, Okla. The location of a portion of this storm over an urban area permitted the collection of an unusual amount of rainfall data for the size of the area. Depth-area-duration relationships based on recording-gage data are presented. A meteorological analysis of the storm indicates low-level convective activity with nearly calm high-level winds resulted in the almost stationary thunderstorm situation responsible for the excessive rainfall rates.
Abstract
On July 27, 1963, a storm produced rainfall intensities that exceeded prior records for Tulsa, Okla. The location of a portion of this storm over an urban area permitted the collection of an unusual amount of rainfall data for the size of the area. Depth-area-duration relationships based on recording-gage data are presented. A meteorological analysis of the storm indicates low-level convective activity with nearly calm high-level winds resulted in the almost stationary thunderstorm situation responsible for the excessive rainfall rates.
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Some examples of National Severe Storms Project observations are described, showing certain typical structures of the mesoscale environment and of large thunderstorms in the Oklahoma-Texas-Kansas region.
The “dry-line” at the cT/mT boundary is shown to be characterized by an extremely abrupt gradient of water-vapor content and temperature, accompanied by a wind-shift zone with appreciable horizontal convergence. On the moist air side, there were pronounced wavelike perturbations in the moisture and temperature fields, connected with systematic variations of the vector wind velocity.
Special pilot-balloon observations show the low-level jet as a flat sheet of southerly winds, with maximum strength generally 300 to 500 m. above ground, and illustrate the great variations of wind speed associated with diurnal variability of stability in the surface layers. Appreciable streakiness of the velocity field is indicated by both pibal and aircraft measurements.
A description is given of a series of intense low-pressure systems observed at the surface, in association with the northwest sides of radar echoes. These depressions, which form at night, are warm and very dry relative to their surroundings, and are attended by strong, gusty surface winds.
High-level aircraft observations are illustrated, demonstrating particularly the significant disturbances of the wind field around cloud tops. An example of gust measurements in the upper portion of a thunderstorm (imbedded in strong vertical shear) shows that the lateral gust components, up to 30 m./sec., are of the same order as the vertica1 gusts.
Movements of thunderstorms as shown by radar, and certain aspects of the reflectivities of tornado-bearing storms, are discussed briefly. Finally, the three-dimensional forms of large thunderstorms are illustrated, with emphasis on the organized asymmetrical structures.
Abstract
Some examples of National Severe Storms Project observations are described, showing certain typical structures of the mesoscale environment and of large thunderstorms in the Oklahoma-Texas-Kansas region.
The “dry-line” at the cT/mT boundary is shown to be characterized by an extremely abrupt gradient of water-vapor content and temperature, accompanied by a wind-shift zone with appreciable horizontal convergence. On the moist air side, there were pronounced wavelike perturbations in the moisture and temperature fields, connected with systematic variations of the vector wind velocity.
Special pilot-balloon observations show the low-level jet as a flat sheet of southerly winds, with maximum strength generally 300 to 500 m. above ground, and illustrate the great variations of wind speed associated with diurnal variability of stability in the surface layers. Appreciable streakiness of the velocity field is indicated by both pibal and aircraft measurements.
A description is given of a series of intense low-pressure systems observed at the surface, in association with the northwest sides of radar echoes. These depressions, which form at night, are warm and very dry relative to their surroundings, and are attended by strong, gusty surface winds.
High-level aircraft observations are illustrated, demonstrating particularly the significant disturbances of the wind field around cloud tops. An example of gust measurements in the upper portion of a thunderstorm (imbedded in strong vertical shear) shows that the lateral gust components, up to 30 m./sec., are of the same order as the vertica1 gusts.
Movements of thunderstorms as shown by radar, and certain aspects of the reflectivities of tornado-bearing storms, are discussed briefly. Finally, the three-dimensional forms of large thunderstorms are illustrated, with emphasis on the organized asymmetrical structures.
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A correlation of synoptic features and upper level flow patterns with 16 crop-hail insurance claim areas in the mid-western United States is made. This study indicates that the following two parameters are present in each case, and may play a significant role in the establishment of an air mass structure which sustains wide-spread hail activity:
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(a) A 30–40 knot band of maximum wind flow at 16,000 feet through, or just north of, the hail area.
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(b) A closed anticyclonic circulation extending from the gradient level up to the 8,000–10,000 ft level, and occasionally higher.
A correlation of synoptic features and upper level flow patterns with 16 crop-hail insurance claim areas in the mid-western United States is made. This study indicates that the following two parameters are present in each case, and may play a significant role in the establishment of an air mass structure which sustains wide-spread hail activity:
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(a) A 30–40 knot band of maximum wind flow at 16,000 feet through, or just north of, the hail area.
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(b) A closed anticyclonic circulation extending from the gradient level up to the 8,000–10,000 ft level, and occasionally higher.
The FGGE Advisory Panel under the U.S. Committee for the Global Atmospheric Research Program of the National Academy of Sciences has recently published a document that describes the observational systems and availability of research data for the Global Weather Experiment (FGGE). In addition, many areas of research using the FGGE global data sets are suggested by scientists who participated in several FGGE workshops during late 1975 and early 1976. A summary of the document follows.
The FGGE Advisory Panel under the U.S. Committee for the Global Atmospheric Research Program of the National Academy of Sciences has recently published a document that describes the observational systems and availability of research data for the Global Weather Experiment (FGGE). In addition, many areas of research using the FGGE global data sets are suggested by scientists who participated in several FGGE workshops during late 1975 and early 1976. A summary of the document follows.
