Evening star. [volume] (Washington, D.C.) 1854-1972, 1936-03-19

Thunderstorms are meteorological
gypsies.
There are two big tribes of them wan
dering over the United States, following
rather definite routes from their GEN.
tiers year after year.
The thunderstorm distribution for 80
years has been analysed by William s.
Alexander of the staff of the United
States Weather Bureau, who finds some
striking Irregularities in their monthly re-
currence from year to year.
During the Winters, naturally, they are
in their southern quarters. The January
camp, scene of the greatest activity. Is
over Northern Louisiana. From this
center they are spread out thinly over
the Gulf and South Atlantic States as
far north as the Carolinas and over the
lower Missouri, Ohio and Tennessee val
leys, West of line drawn about through
the center of Texas they are practically
unknown. But, curiously enough. there
is a small thunderstorm center over
Northern Utah.
During February the Northern Louisi-
ana center shifts eastward. resting over
Mississippi. Southern Alabama and
extreme Western Florida. Also the
storms have started to spread over the
country The line has moved westward
to Southern Arizona and northward to
the Great Lakes, although still the
storms in these regions are very infre-
Quent.
In March the center shifts again. Dur
ING most of the month the greatest thun-
derstorm density, as shown by the 90
wear record, is found over Southern
Arkansas and extreme Northeastern
Louisiana. The area has continued TO
spread rather rapidly and now covers the
entire eastern half of the country. There
also has been a spread over Arizona,
New Mexico and Utah. During April
there is a slight westward shift OF the
center until it comes to rest over North
eastern Texas. Practically no part OF
the United States is entirely immune
from the storms during this month. AL
though they are quite rare along the
Pacific Coast, they are quite frequent in
the Southern Rocky Mountain States.
The May chart, says Mr.. Alexander,
reveals a very interesting and Slgnlfl-
cant development apparently not fore
Swallowed in any of the previous months
the sudden appearance OF secondary
center of activity on the West Florida
Coast in the vicinity of Tampa" This
marks the first appearance during the
year of the second gypsy tribe of storms.
All Winter they have been alternating
neutrality-suspicious. over the west
Indies. At the same time the first tribe
moves its camp northward into Missouri
and the Ohio and Tennessee valleys.
During June, 1t is shown by the 30-year
record, the storms have become common
all over the United States. The two
tribes" now are clearly distinct and
far apart. The Florida center has be-
come by far the largest and most active.
The Western, or secondary, center now is
established over Colorado. From each
center the storms spread out with de
minishing density. In the area of great
est activity the storms occur on an aver
age of every other day. About the west
ern center there is storm every three
days.
July. Mr.. Alexander finds, is the month
of greatest intensity over the entire
country. During this month the sec
ondary center over the Southwest has
about the same intensity as the primary
over the Southeast. The former has
had SIS days with thunderstorms in 80
years and the latter GAL. Curiously
enough, the Pacific Coast still is prac-
tically immune.