More typically, by tracking the motion of persistent clouds, wind speeds have been shown to vary from 20 m/s in the easterly direction to 325 m/s westward.

Once known as one of the most polluted urban areas for its persistent brown cloud, Denver is about to become the first major city to achieve full compliance with the Clean Air Act by eliminating severe air pollution.

Winters are generally cold with persistent cloud and fog.

Perhaps the important point is simply that there is a persistent cloud of uncertainty about where China is going.

Late daylight was fading steadily behind persistent clouds, though still the sun was not quite down.

With the lingering traces of daylight baffled by persistent clouds of mist, the awesome dimensions of the Canyon remained concealed-though the mist was now beginning to sink into the depths.

The prospect of rain, what with the persistent clouds overhead indistinguishable from the black incinerator smoke that belched across the Bronx sky, was no doubt for more than a couple of Yankee fans as promising as it was threatening.

Over this was a persistent dark cloud over Breithaupt; that of drug abuse, that has been with him since the l980s and tied to the untimely loss of his father.

But for all the numerical wonders - a .322 average in 1987, a career fielding percentage of .980, the 17 triples in 1990 - there has been a persistent cloud of disappointment.

This band of persistent clouds is called the Intertropical Convergence Zone, the place where the easterly trade winds in the Northern and Southern Hemispheres meet.