SUMMER HOT WINDS ON THE GREAT PLAINS. 319 
on the 1st, moved steadily eastward, and on the 5th occu¬ 
pied the central slope, while the low pressure area moved 
eastward to the lower lakes and central valleys. Cloudy 
weather prevailed in advance of the high pressure area as 
it moved eastward. Cloudless weather prevailed over the 
central and southeastern slopes. 
The hot winds of August 10 accompanied an area of low 
pressure which developed over eastern Colorado on the 
morning of August 8 as g, secondary to a low pressure which 
moved eastward from Montana on the 7th. This latter 
low pressure area soon disappeared, while the one which 
had developed over the central slope increased in energy 
and moved slowly northeast until the 10th, after which it 
moved rapidly eastward and disappeared to the north of 
the lakes on the 11th. The barometer during this time 
continued above 30 inches along the coast of Oregon and 
Washington, with cloudiness to the west of the divide, but 
no well defined atmospheric circulation. Cloudless weather 
prevailed on the 9th and 10th over the central and south¬ 
eastern slopes. 
The hot winds on August 14 were preceded and accom¬ 
panied by the following conditions: On the 12th the ba¬ 
rometer w r as above 30 inches over the central slope, with 
cloudy weather and rain. A low pressure area was advanc¬ 
ing from the northern plateau region, and this displaced 
the high pressure area over the central slope on the morn¬ 
ing of the 13th, with its greatest depth over Nebraska. On 
the 14th the low pressure extended from Lake Michigan to 
Colorado, with its greatest depth over southeastern Iowa, 
but a secondary disturbance was developing over western 
Kansas, with clearing weather. On the loth the low press¬ 
ure moved rapidly eastward. During this time the press¬ 
ure was about 30 inches over the western portions of Ore¬ 
gon and Washington, with a very well defined movement of 
the atmosphere from the Pacific slope across the divide 
toward the low pressure area, with more or less cloudiness. 
