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CHARLES F. BROOKS

Abstract

SYNOPSIS

Long-range forecasts are so much desired that any number of unqualified persons issue them without regard for criteria of performance. Among what might be called “fake” forecasts are the almanac, astrological, pseudosolar, and “mathematical” sorts, many of them calamity howls. The “prediction” of climatic normals, forecasts from phenomena on certain dates and from the behavior or aspects of certain animals or plants also belong in this category.

To be of value a forecast must be specific, limited as to place and time, and it must have a probability of more than chance verification. Furthermore, the economic consequences of failures, both in the long run and in a small sequence of years, must be reckoned. A forecast that will not hit the mark four times out of five, or at least once out of every three in succession, can not be of much value, though some claim that a forecast verified only three times out of five would be useful. The uncertainties of meteorological relationships on which any long-range forecasts can now be based are generally too great to permit reputable meteorologists to forecast on expectations of less than 75 or 80 per cent verification. A critical study of the methods now used in the attempts at scientific long-range weather forecasting and an evaluation of their relative merits for different parts of the world is much needed.

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CHARLES F. BROOKS

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Charles F. Brooks
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por Charles F. Brooks
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Charles F. Brooks

Synopsis

The two severe storms that overtook Columbus on the return portion of his first voyage, when examined in the light of modern frontal theory, do not appear to have been simple circular storms, as previously thought, but disturbances marked by well developed fronts. The centers of both passed north of Columbus; he apparently experienced the warm sectors of both. The February storm seems to have had two cold fronts, and the March one a very sharp cold front. Storms of both kinds have been observed in the same portion of the Atlantic in recent years.

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Charles F. Brooks
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Charles F. Brooks
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CHARLES F. BROOKS

Abstract

The appearance of mammato-cumulus clouds, whether formed at high or low levels, shows that they are formed by local downward thrusts of air. Those associated with overflow sheets of thunderstorms are obviously formed of snow, which accounts for the slowness with which they change shape. While minor developments are not uncommon. the large, well-developed festoons of this class are associated only with the most severe thunderstorms.

On the boundary between two general winds, interference and initial condensation of moisture as a result of the projection of masses of the upper mammato-cumulus into the lower wind, occasionally form. If the upper wind is the colder, convection quickly destroys the mammato formation. If the lower current is already cloudy, cold air from above, especially if dry, may blow “cheese holes” through it.

The most impressive mammato-cumulus is the low, downward boiling cloud surface which marks the top of a cool, squall wind.

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CHARLES F. BROOKS

Abstract

During the past four years the Gulf Stream has been subjected to investigation by sea-water thermographs on crossing ships. Details of temperature, including alternating masses of warmer and cooler water, diurnal ranges of temperature, and rapid changes in distribution, have been written on the thermograms to form an amazingly complex picture.

The thermograph is a mercury-in-steel bulb and capillary type, the thermal element being fixed in the intake pipe through which large volumes of water from several feet below the surface are continually pumped to the condensers.

An instrument of this sort installed in 1928 on the Peninsular & Occidental steamship Henry M. Flagler, one of the three Key West-to-Habana car ferries, provides the temperature record for one round trip daily while the ship is in operation. The south-bound trip gives a night profile and the northbound a daytime one. From night to day in sunny quiet weather the sea temperature at the surface rises 3° or 4° F. and at a depth of 6 feet about 2°. In windy weather the diurnal range is reduced by stirring to 1° or less.

The summer profile is characteristically warmer in the north than in the south, while the temperature of Key West Harbor stands out several degrees above the Gulf Stream. A band of cool water is almost always traversed within a mile of the Cuban shore, apparently where swell and current striking the steeply sloping bottom bring cool water to the surface. Similar cool water often occurs likewise at the margin of shoal water south of Key West. The winter profile is usually 2° or more warmer in the south than in the north portion of the straits. A narrow zone of probably upwelling water several degrees cooler than on either side usually divides the warmer water from the cooler. This boundary shifts many miles with wind and other effects that bring at one time more water direct from the Caribbean and at another time from the Gulf. Great variations sometimes occur in the course of a few hours.

Storms, chiefly through their stirring action, reduce the surface temperatures by 1° or more. Strong cold winds have an even greater effect than hurricanes, for they chill the water considerably as well as mix the warm surface layer with the cooler substrata.

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Charles F. Brooks
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