114 AIR MASS ANALYSIS 
A Dust Storm 
May 9 to 11, 1934, a famous duststorm raced from Montana and North 
Dakota to the Atlantic Seaboard and out to sea, one of the few such to reach 
the ocean. The maps for this situation, below, were analyzed and discussed 
by G. R. Parkinson (BULL., May, 1936, pp. 127-35.) The dust storm generally 
rages in NPP air, which is unstable (by day at least) and windy in the winter 
and spring. Note how in this case the dust (stippled areas) was raised in the 
foreward part of NPP air masses where the pressure gradient was steep and 
hence the wind fairly high and the lapse-rate unstable, and in passing over 
regions of barren soil due to drought, plowing and winter; once raised to con- 
siderable heights in the air mass, the dust stayed in suspension long enough 
to be carried still higher and a long ways East. 
Sy Ja | ened eT \_95 
— 3a HL 3o.l 700 24 AY BTA 1950, 
: 3 ¢ Ss urs 
\ 
(B). WEATHER Map, 8 P.M., May 9, 1934. 
