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Glenn E. Stout
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Robert Cataneo and Glenn E. Stout

Abstract

Raindrop-size spectra obtained with the raindrop camera have been analyzed from two locations, Island Beach, N. J., and Franklin, N. C. The spectra were analyzed with respect to total number of drops per average rain rate per cubic meter of sample, geometric mean diameter, mode diameter, and the diameter of drops at which half the liquid water content lies above that diameter and half below. The results indicate that the distributions from both locations are quite similar for corresponding rainfall rates. Rainfall rate-radar reflectivity relationships indicate that cold frontal rains in these areas generally have smaller drops than warm frontal rains. In addition, it was found that upslope rains are composed of smaller drops than rains of similar synoptic conditions without upslope effects. Finally, a small sampling of a tropical storm rain revealed that small drops may be characteristic of this type of rain.

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Stanley A. Changnon Jr. and Glenn E. Stout

Abstract

Information on hail intensity is not readily available on a national or local scale. As a result, a study was made to obtain general estimates of the mean areal patterns of hail intensity in the central and northwestern continental United States. Although the results of the study are based on indirect measures of hail intensity developed from crop-insurance data, the results provide useful estimates of a phenomenon heretofore unmeasured. Intensity measures derived from crop-insurance data available for 19 states revealed that summer hailfalls at points in the lee of the Rocky Mountains were 5 to 15 times more intense than those in the Middle West. A good correlation was found for the mean intensity indices of states and the mean hailday frequencies, suggesting that the widely available climatological data on hail frequency could provide useful estimates of hail intensity in other states.

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John Schuetz and Glenn E. Stout

Preceding the development of a tornado at the ground a fingerline projection developed on the PPI in the SW corner of an echo. This was also visible on the three-dimensional models constructed from RHI data. The parent echo extended to 37,500 feet and was the highest echo in the vicinity. Tornado occurrence was simultaneous with a new cell merging with the finger. Photographs of the tornado, the lower level echo tilt, and winds aloft data all indicate the same direction of shear.

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Glenn E. Stout and Eugene A. Mueller

Abstract

Numerous investigations have been made in the last two decades from both a direct measurement of the radar reflectivity and the rainfall amount, as well as indirect measurements of the raindrop size spectra. Calculations of the reflectivity factor and rainfall rate from these spectra can be made and the relationships determined. Both methods are discussed and a summary of the relationships presented.

These relationships show differences in excess of 500% in rainfall rate at the same reflectivity. These large differences are primarily associated with differences in geographic locality. In addition, there are smaller differences on the order of 150% that can be attributed to different types of rain or different synoptic conditions.

Some data are available which are indicative of the differences in the relationship on a given day, depending upon the location within the storm which is sampled. This is briefly described and in only one case out of 18 is there a significant difference.

Estimates of the effects of evaporation, accretion and coalescence on the relationship are made and show some of the reasons for the differences in the relationships noted at different geographical locations. The accuracy of the relationships is investigated with attention directed to the evaluation of total storm amounts. It is shown, in general, that the relationships introduce less uncertainty than the uncertainty in obtaining a radar measurement of the reflectivity.

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