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.
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.
But the greater part of north-west India is served as a rule by cyclonic storms between the two currents.
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.
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.
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.
The islands on the sea-front are exposed to devastation by cyclonic storm-waves.
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.
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.
Dissipation was above the average when cyclonic conditions prevailed, but this seemed simply a consequence of the increased wind velocity.