Accession Number:

AD0258884

Title:

THE MOTION AND PREDICTABILITY OF STRATIFORM PRECIPITATION

Descriptive Note:

Corporate Author:

ALLIED RESEARCH ASSOCIATES INC BOSTON MASS

Personal Author(s):

Report Date:

1961-02-01

Pagination or Media Count:

1.0

Abstract:

Analysis of the motion of the edges of sheets of uniform precipitation as viewed on radar, indicates that the velocity of advance of the edge measured perpendicular to the edge is a reasonably conservative quantity. The speed appears unrelated to the observed wind component in the direction of advance at any level or combination of levels however, the orientation of the edge is such that the direction of advance generally lies to the right of the upper winds. The motion of elements within the precipitation sheets is closely related to the direction of the wind at the 700 mb level. The empirical probability of precipitation reaching a given point is derived in terms of the estimated travel time of the precipitation. The probability is significantly higher, for the same travel time, than that previously derived for precipitation lines. Simulated forecast tests of the predictability of the edge motion for periods of 2 to 6 hr indicate that in 74 of the trials the error in timing the arrival of precipitation amounted to 30 or less of the forecast period, and that these values changed little as the length of the forecast period increased. Author

Subject Categories:

Distribution Statement:

APPROVED FOR PUBLIC RELEASE