764 
f. Correlation of precipitation with upper-air patterns 
and the direction and movement of lows, and develop- 
ment of methods of forecasting the great variation in 
warm-sector precipitation. 
g. Investigation of the whole problem of summertime 
precipitation, the causes of most of which are obscure. 
It is suggested that further relationships between 
showers and convective instability be developed to 
reduce the forecasting of showers to some practical 
numerical basis. 
4. The causes of deepening and filling of pressure 
systems. This problem was second in order of priority 
on the forecasters’ list. With it is the associated problem 
of wave development. 
5. The speed and direction of movement of highs, 
lows, and fronts. Tolerable errors (15°) in forecasting 
the direction of movement will result in very serious 
errors in the weather forecast for 24 hr hence. Less 
complex methods of employing acceleration and de- 
celeration factors are desired. 
6. Treatment of cold upper-air lows; their formation, 
movement, and dissipation. 
7. Bringing the historical weather map series up to 
date, including 700- and 500-mb charts. 
8. Development of instruments which could measure 
vertical motions, and changes in moisture and stability 
aloft. 
There are numerous other problems, local in nature, 
which are properly the subject of investigations at the 
district forecast center, and, of course, only a beginning 
has been made in the attack on forecasting problems 
in the tropics. 
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