Horace R. Byers

CAUSES OF THUNDERSTORMS OF THE FLORIDA PENINSULA

Abstract After a study of temperature and humidity soundings in Florida during the summer of 1946 failed to produce an explanation for the occurrence or nonoccurrence of thunderstorms, the theory was proposed that large-scale horizontal convergence in the low levels was the necessary condition for thunderstorm convection. Traveling or semipermanent synoptic features of the region producing this convergence were found to be too rare or too remote to account for the almost daily thunderstorm activity of the interior of the Florida peninsula. Low-level horizontal convergence caused by the afternoon sea breezes entering the peninsula from both sides was found to be the most rational explanation of the thunderstorms. Using the Bellamy “triangle method” applied to pilot-balloon stations it was found that low-level convergence developed practically every afternoon during the summer months as a result of this diurnal sea-to-land circulation. The effects extended to an altitude of 3000 or 4000 ft. A comparison wit...

THUNDERSTORM STRUCTURE AND CIRCULATION

Abstract Data from Thunderstorm Project observations in Florida, derived mainly from airplane traverses through thunderstorms, are analyzed in order to obtain a description of thunderstorm structure and circulation. Thunderstorms are normally found to consist of several more-or-less independent convective systems or “cells”. Each cell goes through a life cycle represented by three fairly distinct stages-the cumulus stage, the mature stage, and the dissipating stage. In the cumulus stage the cell is formed from an updraft of air which, as in the other stages, “entrains” air from the environment. In this stage no rain has yet reached the ground. In the mature stage, rain is occurring and a large part of the cell consists of a downdraft which characterizes the rain area. The updraft continues in a portion of the cell in the low and intermediate levels and in all parts of the top levels. In the dissipating stage, downdrafts are present throughout, although weak upward motion is apparent in the upper parts. Th...

Spearhead Echo and Downburst in the Crash of an Airliner

Abstract 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 designated as “spearhead echoes” which move with unusual speed. The development of downburst cells appears to he tied in with overshooting tops of clouds at the anvil level.

A CENSUS OF CUMULUS-CLOUD HEIGHT VERSUS PRECIPITATION IN THE VICINITY OF PUERTO RICO DURING THE WINTER AND SPRING OF 1953-1954

Abstract The analysis of fifteen cloud-census flights confirms the common existence of warm precipitation from trade-wind cumuli. A probability that over-water clouds of certain vertical developments will contain precipitation is presented. Since the examined over-water clouds with tops higher than 11,500 feet always contained precipitation and yet were well below the freezing level, the futility of initiating rain by seeding clouds with freezing reagents becomes obvious.

Some Effects of Vertical Wind Shear on Thunderstorm Structure

Observations of thunderclouds obtained with a 3-cm height-finding radar set are used to obtain a description of the vertical shear of thunderclouds. Several photographs are given which show the she...

Artificial Nucleation of Cumulus Clouds

A field research program was designed to obtain statistically significant answers concerning the efficacy of precipitation inducement methods in cumulus clouds. Operations were carried out in the Caribbean Sea area and in the Central United States. Successful experiments were conducted on 122 valid pairs of clouds. Each pair of clouds consisted of one treated and one untreated cloud. The treated cloud was randomly selected.

MEASUREMENT OF RAIN TEMPERATURE

Abstract A technique for measuring the temperature of rain at the ground and the methods for calibrating the equipment used for this purpose are described in this report. A preliminary analysis of the data indicates that significant differences between the rain and ambient air temperatures usually occur in the first portion of the thunderstorm rain period and that the differences in temperature between the ambient air and the rain falling from the latter portion of the storm are small.

Inflow Patterns of Thunderstorms as Shown by Winds Aloft

Balloons ascending simultaneously at various points around thunderstorms are followed by radar or radio-direction finding (rawins and rawinsondes) to determine horizontal inflow or outflow of the a...

THE ‘BRIGHT LINE’ IN RADAR CLOUD ECHOES AND ITS PROBABLE EXPLANATION

Abstract Observations on 10-cm height-finding radar of echoes from stratified clouds indicate a horziontal band which produces a stronger return than the parts above or below it. The height of ’bright line‘ occurrence is always at the freezing level and therefore supports the idea of drop formation and consequently radar-target formation in the colloidally unstable layer of heterogeneous ice-water mixture. Several examples are given from the thunderstorm observation network in the vicinity of Orlando, Florida

Computing a design flood in the absence of historical records

SummaryA design flood for a Venezuelan river is computed in the absence of rainfall and stream-flow data of more than a few years. From synoptic studies of an area embracing northern South America and the Caribbean, the type of disturbance producing the abundant rains of the area is determined. A disturbance of this type is maximized on the basis of the ratio of energy dissipated through friction to released latent energy represented by rainfall — in other words, theefficiency of the system is given its highest reasonable value. The synthetic disturbance is moved over the river basin in a manner most favorable for heavy rain. Certain data available from other rivers are used as a cross-check on the resultant flood values.