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- Author or Editor: Morris Tepper x
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Abstract
On December 6, 1949, an accelerated microbarograph in Washington, D. C., produced a unique pressure trace at the time that a peculiar cloud bank passed overhead. The rear (western) edge of this cloud bank ended very abruptly and had the appearance of an Antarctic ice barrier. A study of the synoptic conditions of the day revealed that this pressure variation was produced by an expansion-type pressure wave which travelled eastward from the Midwest and was propagated between two inversion surfaces with a speed far in excess of the wind speed in that layer. The cloud bank also travelled in this same atmospheric layer but was advected by the prevailing winds. The conclusion is reached that the pressure wave which progressively overtook the cloud bank was associated with a rapid drop of the isentropic surfaces which in turn produced the adiabatic heating necessary to desiccate the cloud partially in the Midwest and completely over Washington. Confirmation of this conclusion is found in solar radiation records.
Abstract
On December 6, 1949, an accelerated microbarograph in Washington, D. C., produced a unique pressure trace at the time that a peculiar cloud bank passed overhead. The rear (western) edge of this cloud bank ended very abruptly and had the appearance of an Antarctic ice barrier. A study of the synoptic conditions of the day revealed that this pressure variation was produced by an expansion-type pressure wave which travelled eastward from the Midwest and was propagated between two inversion surfaces with a speed far in excess of the wind speed in that layer. The cloud bank also travelled in this same atmospheric layer but was advected by the prevailing winds. The conclusion is reached that the pressure wave which progressively overtook the cloud bank was associated with a rapid drop of the isentropic surfaces which in turn produced the adiabatic heating necessary to desiccate the cloud partially in the Midwest and completely over Washington. Confirmation of this conclusion is found in solar radiation records.
Abstract
The radar and synoptic analysis of the tornado situation of November 14, 1949, at Pierson, Fla., yields conclusions which are compatible with the author's hypothesis that the interaction zone of two intersecting pressure jump lines is a preferred region for tornado formation. Relevant to the case discussed, another mechanism for producing a pressure jump line is suggested—the “backward” moving pressure jump line.
Abstract
The radar and synoptic analysis of the tornado situation of November 14, 1949, at Pierson, Fla., yields conclusions which are compatible with the author's hypothesis that the interaction zone of two intersecting pressure jump lines is a preferred region for tornado formation. Relevant to the case discussed, another mechanism for producing a pressure jump line is suggested—the “backward” moving pressure jump line.
Mesometeorology is the study of atmospheric motions of characteristic dimensions too small to make them readily identifiable on the macroscale synoptic maps in use today. Results of mesoanalysis reveal systems which have definite order, pattern, and chronological continuity, and with which most pertinent local weather seems to be associated. The role of mesometeorology in local weather forecasting is analyzed.
Nine senior meteorologists with considerable experience and stature in the field of forecasting participated in a forecasting experiment wherein three were given mesometeorological analyses and six were given the regular analyses available at a forecasting center. The results showed that the former group was able to identify and forecast the short-range significant variations in wind, temperature, and precipitation in time and place while the others in general could not.
Mesometeorology is the study of atmospheric motions of characteristic dimensions too small to make them readily identifiable on the macroscale synoptic maps in use today. Results of mesoanalysis reveal systems which have definite order, pattern, and chronological continuity, and with which most pertinent local weather seems to be associated. The role of mesometeorology in local weather forecasting is analyzed.
Nine senior meteorologists with considerable experience and stature in the field of forecasting participated in a forecasting experiment wherein three were given mesometeorological analyses and six were given the regular analyses available at a forecasting center. The results showed that the former group was able to identify and forecast the short-range significant variations in wind, temperature, and precipitation in time and place while the others in general could not.
Abstract
The problem of the impulsive addition of momentum to a simple current system, discussed previously by Rossby and Cahn, is reexamined and the basic equations are solved by a numerical-graphical technique. The equations representing the transient phase are considered first from a linear and then from a non-linear point of view and the differences indicated. The conclusion is reached that the non-linear solution can yield a gravity wave which steepens with time and which propagates normal to the orientation of the initial current. A possible application of the theory to the atmosphere is suggested, in the production of eastward moving pressure-jump lines by southerly currents.
Abstract
The problem of the impulsive addition of momentum to a simple current system, discussed previously by Rossby and Cahn, is reexamined and the basic equations are solved by a numerical-graphical technique. The equations representing the transient phase are considered first from a linear and then from a non-linear point of view and the differences indicated. The conclusion is reached that the non-linear solution can yield a gravity wave which steepens with time and which propagates normal to the orientation of the initial current. A possible application of the theory to the atmosphere is suggested, in the production of eastward moving pressure-jump lines by southerly currents.
Abstract
The squall line of 16 May 1948 in the area of the Cloud Physics Project, U. S. Weather Bureau micro-meteorological network of weather recording stations near Wilmington, Ohio, is analyzed by means of one-minute synoptic maps, x–t diagrams and isochrone maps. The relative behavior of the pressure jump, wind shift, temperature fall, maximum wind velocity, rain gush and pressure maximum forms the basis of a hypothesis concerning the physical mechanism of the squall line. Following the theory developed by Freeman, it is proposed that a squall line might be considered as a disturbance generated by accelerations along the cold front and which travels along the warm sector inversion as a gravitational wave. It is recommended that any series of meteorological events similar to this mechanism be called a Pressure Jump Line. The weather associated with the passage of a pressure jump line is then indicated.
Speculatively it is proposed, by analogy to the theory of supersonic flow and shock waves, that the zone of interaction of two pressure jump lines is a preferred zone for tornado formation.
The importance of the intensity and the time of passage of a pressure jump over a station, as the primary tools for identifying and following the progress of pressure jump lines, is emphasized.
Abstract
The squall line of 16 May 1948 in the area of the Cloud Physics Project, U. S. Weather Bureau micro-meteorological network of weather recording stations near Wilmington, Ohio, is analyzed by means of one-minute synoptic maps, x–t diagrams and isochrone maps. The relative behavior of the pressure jump, wind shift, temperature fall, maximum wind velocity, rain gush and pressure maximum forms the basis of a hypothesis concerning the physical mechanism of the squall line. Following the theory developed by Freeman, it is proposed that a squall line might be considered as a disturbance generated by accelerations along the cold front and which travels along the warm sector inversion as a gravitational wave. It is recommended that any series of meteorological events similar to this mechanism be called a Pressure Jump Line. The weather associated with the passage of a pressure jump line is then indicated.
Speculatively it is proposed, by analogy to the theory of supersonic flow and shock waves, that the zone of interaction of two pressure jump lines is a preferred zone for tornado formation.
The importance of the intensity and the time of passage of a pressure jump over a station, as the primary tools for identifying and following the progress of pressure jump lines, is emphasized.
Abstract
An attempt is made to rationalize the spectacular increase in the number of tornado reports during recent years and to make a logical segment of these reports compatible with reports of previous years. A numerical method of classifying tornado reports into “tornado,” “possible tornado,” “severe local storm,” and “local storm” is suggested.
Abstract
An attempt is made to rationalize the spectacular increase in the number of tornado reports during recent years and to make a logical segment of these reports compatible with reports of previous years. A numerical method of classifying tornado reports into “tornado,” “possible tornado,” “severe local storm,” and “local storm” is suggested.
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