Alexander McAdie

“ When the weather has been clear and moderately warm for two or more days, and the winds are light and variable, there may occur on the third day a moderate wind from the east, known as the sea-breeze. This occurs during anticyclonic conditions. Preceding the sea-breeze, the winds are very light, there are no clouds, and the temperature rises rapidly during the forenoon. This heating is due to a slow dynamic compression as the air slowly descends and the surface air does not flow away. There is no cooling because there is no evaporation due to air movement. ”

“ Zephyros, the west wind, is represented as a graceful youth, scantily clad, with his arms filled with flowers. In Greece this wind traversed the Ionian Sea and the Gulf of Corinth before reaching Athens. It is quite unlike our west wind which blows across a continent, and is continuously robbed of its water vapor on the long passage. The Ionian wind is pleasantly moist and refreshing. ”

“ One must rise above the ground some distance to get the true air flow, or what is known as the gradient wind, the flow which balances the gradient, i.e. a flow along the isobars. The gradient velocity is found about 300 metres above the ground, and the gradient direction a little higher. The lower clouds as a rule [Pg 31] indicate true wind values very well; and so, it is desirable in studying winds to use cloud directions and velocities rather than surface values. In cloud work a nephoscope is essential. The unaided eye, unless properly shielded, suffers from the glare of a sunlit sky ”

“ A black mirror, with suitable sighting rods and measuring devices, enables an observer to follow the cloud, estimate its height and determine with accuracy the direction from which it is moving. There is an average difference of 30 degrees between the cloud direction and the surface wind; the upper direction being more to the right. ”

“ A vigorous fanning of the air helps evaporation and cools us. That is why a brisk northwest wind routs a muggy condition.
CASTILIAN DAYS
John Hay wrote of such days spent in Spain. We who live in a land where the winds are more boisterous, occasionally experience what we call a perfect day. Such days have easterly winds of two metres per second or less than five miles an hour. The temperature is midway between freezing and normal body temperature or about 70° F. The relative humidity is approximately 75% and the absolute humidity 12 grams per cubic metre. ”

“ If there is so much uncertainty in forecasting the path of a disturbance at sea, how much more uncertain must it be on land? Elaborate statistics of the average daily movement of various types of storms have been officially published. The average speed of storms [Pg 43] (not wind speeds) across the United States is 11 metres per second or 25 miles an hour. Storms travel more rapidly in winter than in summer, about half again as fast ”

“ A depression can make little headway if to the north or east the normal path is blocked by what is known as a stagnant "HIGH." So therefore, if the anticyclone is a slow mover, a Texas storm, which would normally pass not far from southern New England, may be deflected farther north than when the HIGH moved rapidly east. ”

“ The absolute humidity is low, often less than ten grams per cubic metre. Cumulus clouds do not form because there is no uplift of the lower air and consequently no chance for condensation of whatever water vapor may be present. No thunder-heads form notwithstanding the [Pg 76] heat. The heat, while dry, is nevertheless extremely trying to men and animals. Relief comes in the early hours of the afternoon by the arrival of the sea-breeze. ”

“ Moreover, the weather map does not indicate the true flow of the air, for observations of the wind made at the [Pg 28] ground tell only a part of the story of the balance which the flowing air must maintain under the action of various forces, such as gravitation, rotational deflection, centrifugal tendency, and the various expansion and compression forces.
The winds near the ground are modified both in velocity and direction by friction. The free flow is often interfered with by topography. ”

“ On muggy days we are somewhat in the condition of the unfortunate prisoners in the Black Hole at Calcutta. They did not die by poisoning, as has generally been accepted, that is, lack of sufficient oxygen and an excess of carbon dioxide; but because they were unable to keep the skin sufficiently cool. There was no ventilation; no movement of the air and the body became over-heated and exhaustion followed. No matter how [Pg 81] much water there may be on the skin if the surrounding space is saturated, one feels oppressed. ”

“ Nor does the flow extend far inland, which would be the case if there were up-rising currents. The sea-breeze is very shallow, generally not extending upward more than 200 metres, and often not above 100 metres. It [Pg 77] does not penetrate far inland, as a rule not more than 15 kilometres, 9 miles.
The sea-breeze is probably caused by a slow descent of dry, warm air, on an incline sloping from northeast to southwest. As it reaches the surface it is twisted more to the right; that is, becomes an east wind. ”

“ But each storm is in reality a law unto itself; and while we know something of the relations between pressure and flow of the air; as yet we know very little about the relations of wind and weather. The problem is [Pg 35] complicated by the behavior of the load of water vapor.
Fig. 5. Euros—The Southeast Wind
The Chief Forecaster of one of the great national weather services recently wrote:
"Despite the fact that maps have now been drawn day by day for over half a century, we may safely say that no two maps have been identical." ”

“ On the map there will probably appear also an area of high pressure where the surface air flows leisurely outward and away from the place of highest pressure. Such an area is called an anticyclone, a word first used by Sir Francis Galton in 1863 to designate not only high pressure, but general flow of the air in a reversed or opposite direction to that of the low area or cyclone. ”

“ Kaikias—The Northeast Wind
The modern professional forecaster would scorn to consult the entrails. There are however many amateur forecasters who foretell weather by their aches and rheumatic pains. Probably there is a high correlation factor between body sensations and dampness; and some individuals are quite sensitive to changes in both relative and absolute humidity. [Pg 25] This, however, does not always mean that a storm is approaching. ”

“ The lines of equal pressure or isobars generally curve and inclose what is known as a cyclonic centre, or depression or LOW. The arrows point [Pg 26] in, but not exactly toward the centre of the depression. ”