264 THE WEATHER 



Frequently the forerunning upper clouds are more or less hid- 

 den by stratus that have no connection with the approaching 

 storm. The direction and speed of the upper clouds should 

 then be carefully noted through any breaks that appear in the 

 lower sheet. Storms are usually preceded by cirrus, but cirrus 

 alone do not always indicate a storm. 



289. Other Features of the Illustration. The illustration 

 (Fig. 188) also shows, near the ground, the inflowing winds of a 

 LOW, blowing from east in front and from west in rear; it 

 further shows what becomes of the winds as they approach the 

 center. The highest clouds reach farthest ahead because the 

 upper currents move faster than the body of the storm. The 

 upper clouds seldom move backward much on the rear side of 

 a LOW, because the forward movement of the storm is usually 

 faster than the rearward outflow of the upper currents behind 

 the center. 



The diagram covers 1500 miles of territory and the storm 

 movements of the air were probably not more than 6 or 7 

 miles deep. If on the diagram it is 2 in. from Omaha to Mon- 

 treal, how high should it be from the ground to the upper 

 clouds, to have correct proportions? 



290. The Rain or Snow of a Passing Low. The rainfall of 

 LOWS in the United States is seldom distributed evenly around 

 the center, and the distribution varies much in different 

 storms. In fully developed storms, the precipitation is often 

 well distributed after they reach the eastern third of the 

 country. The heaviest falls are often in the front half, but 

 may occur in almost any portion. In elliptical LOWS, the rain 

 area is likely to extend along or near the center, or axis. 



291. Changes Caused by the Passing of a High. After re- 

 viewing the weather changes caused by the approach and the 

 passing of a well-developed LOW, study Figs. 179, 181, and 186, 

 and note the folio wing : 



1. The barometer rises as a HIGH approaches, and falls as 

 the HIGH departs. The highest readings occur when the center 

 of the HIGH is over us. 



