The cold is then intense and the force of the wind cyclonic. Speaking generally, the Afghanistan climate is a dry one.
A curious feature of the cyclonic storms is that, whether they cross the interior of the country near the northern or southern boundary or along an intermediate path, they converge towards New England as they pass on toward the Atlantic; and hence that the north-eastern part of the United States is subjected to especially numerous and strong weather changes.
On account of the great frequency of cyclonic disturbances passing in from the Atlantic, the average conditions of wind over the British Islands give no idea of the frequency of change in direction and force.
The prevailing winds in this region, which the sea traverses longitudinally, are westerly, but the sea itself causes the formation of bands of low barometric pressure during the winter season, within which cyclonic disturbances frequently develop, while in summer the region comes under the influence of the polar margin of the tropical high pressure belt.
Dissipation was above the average when cyclonic conditions prevailed, but this seemed simply a consequence of the increased wind velocity.
2 The well-known strangely warm and dry fain- winds of Greenland occur both on the west and the east coast; they are more local than was formerly believed, and are formed by cyclonic winds passing either over mountains or down the outer slope of the inland ice.
A cyclonic circulation of the atmosphere is associated with a cyclonic circulation of the water of the ocean, as is well shown in the Norwegian Sea and North Atlantic between the Azores and Greenland.
This produces a heaping-up of warm water towards the middle of the anticyclonic current circulation between io° and 40°, and on the other hand an updraught of deep water along the outer side of the cyclonic currents.
Between these cyclonic storms come areas of high pressure, or anticyclones, with dry cool air in summer, and dry cold air in winter, sometimes with such decided changes in temperature as to merit the name cold wave.
The ranges of the Rocky Mountains in their turn receive some rainfall from the passing winds, but it is only after the westerlies are reinforced by a moist indraft from the Gulf of Mexico and the Atlanticthe result of summer or of cyclonic inflowthat rainfall increases to a sufficient measure on the lower lands to support agriculture without irrigation.
The cyclonic inflows and anticyclonic outflows, so characteristic of the belt of westerly winds the world over, are very irregular in the Cord illeran region; but farther eastward they are typically developed by reason of the great extent of open country.
Although of reduced strength in the summer, they still suffice to dominate weather changes; it is during the approach of a low pressure centre that hot southerly winds prevail; they sometimes reach so high a temperature as to wither and blight the grain crops; and it is almost exclusively in connection with the cloudy areas near and south-east of these cyclonic centres that violent thunderstorms, with their occasional destructive whirling tornadoes, are formed.
In wintertime, the cyclonic and anticyclonic areas are of increased frequency and intensity; and it is partly for this reason that many meteorologists have been disposed to regard them as chiefly driven by the irregular flow of the westerly winds, rather than as due to convectional instability, which should have a maximum effect in summer.
One of the best indications of actual winter weather, as apart from the arrival of winter by the calendar, is the development of cyclonic disturbances of such strength that the change frcm their warm, sirocco-like southerly inflow hi front of their centre, to the cold wave of their rear produces lion-periodic temperature changes strong enough to overcome the weakened diurnal temperature changes of the cold season, a relation which practically never occurs in summer time.
In some cases changes of intensity take place round the auroral zenith, simulating the effect that would be produced by a cyclonic rotation of luminous matter.
But the greater part of north-west India is served as a rule by cyclonic storms between the two currents.
The islands on the sea-front are exposed to devastation by cyclonic storm-waves.
Missouri lies very frequently in the dangerous quadrant of the great cyclonic storms passing over the Mississippi valley - indeed, northern Missouri, lies in the area of maximum frequency of tornadoes.
Strong winds are frequent, as nearly every cyclonic depression traversing North America, either from the westward or the Gulf of Mexico, passes near enough to Lake Erie to be felt.
The country is exposed to destructive floods from the hill-rivers and also from cyclonic storm-waves.
In the northern section the heavy snowfall is caused by the cyclonic storms along the Canadian border, and in the southern section the snowfall is increased by the storms which ascend the Mississippi Valley.
There are in some winters occasional anti-cyclonic or high-area storms known as blizzards - wind-storms preceded or accompanied by snow-fall - which are very severe.
The climate of the interior has been found to be of a continental character, with large ranges of temperature, and with an almost permanent anti-cyclonic region over the interior of the inland ice, from which the prevailing winds radiate towards the coasts.
The climate is very variable, owing to the frequent passage of cyclonic storms from the W.