Evening star., 1935-03-24
FORECASTS AIDED
BY NEW SYSTEM
"Air Mass Analysis" Adopt
ed by Bureau Year Ago,
Proves Effective.

(Copyright, 1895, by the Associated PressJ
Important advances in weather
forcasting have taken place as result
of the Weather Bureaus decision
wear ago to develop its forecaStlng
service along the newer lines OF What
is known as "air mass analysis.
1t definitely has shown Its value
In the following ways: Forecastlng
precipitation-rain and snow; lore
casting thunderstorms and their prob
able movements; forecaSting the PROB
able occurrance and intensity OF
"bumpiness," which Is Of special in
terest to airplane pilots; forecastlng
maximum temperatures, and forecast
ing the probable ceiling" or height
Lf clouds, and the occurrance OF Ice
formation on aircraft.
Several years probably Will be re-
ouired to enable air mass analysis 10
show fully what it can do, but the
first years progress shows its posi-
bilities.
Short Period Success.
This is especially true in the case
of the short-period forecasts Tor
a few hours ahead such as are issued
at night for frosts the next morn
ing. This type of forecasts finds its
greatest use in districts where citrus
fruits and garden truck crops are
extensively grown. At present 1t Is
furnished in an intensive way In
comparatively few sections OF tne
country and its extension to otner
regions would yield very important
economic benefits.
Another example of the short period
forecasts is that issued for flying
activities along the Nations far-t1une
network of civil airways. These fore.
casts cover, as a rule, period Of
4 to 6 hours and must be very precise
and accurate. Air mass analysis is
particularly valuable aid in making
this intensive and detailed type Of
forecast.
Progress along this line has beer
possible chiefly because of the greatel
abundance of information regarding
upper air conditions than was form
erly available. This has come aoou
largely through the use of airplane
that carry so-called "earometeoro-
graphs" which bring back to eartf
a continuous record of temperature
pressure and moisture up to height
averaging 312 miles.
The War and Navy Departments ar
cooperating in this program which a
the present time is providing datt
from % stations. The flights ar
made early enough in the morning
SO that the information can be uSet
for the daily forecasts.
Air characteristics.
The data, as plotted and analyzed
show the chief characteristics o
structure of the air at differen
heights and this enables the fore
casters to determine the extent ant
the interactions of the various masse
of air from different sources and Il
project their development and move
ments into the future more accuratel
than has been possible in the past.
Although chief progress in improv
ing forecasts through air mass analy
sis has been experienced in the cas-
of the short, highly specialized typ
Of forecast, the value of the appli
cation Of this system also to the reg
ular "a to So hour daily forecast
Is already becoming apparent.
In numerous cases the additiona
upper air information, particularly o
temperature. humidity and wint
movement, have resulted in bette
forecasts than would have been pos
sible with surface data only.
t~flr l. l..
Mississippi Valley on october "a, 1894
when the weather map indicated th'
likelihood of general rains. The air.
plane and balloon observations, how.
ever, showed that dry air was coming
in from the West at the levels wherl
rain ordinarily forms.