812 
also omitted in working with daily charts which, in 
reality, are also mean charts, but for brief time inter- 
vals. 
But these arguments can be of little avail until 
definite solutions, theoretical or empirical, are found. 
Ultimately empiricism and theory must converge to 
truth. It seems probable that in long-range forecasting, 
as in hydrodynamics, the most rewarding line of attack 
will be a happy combination of theory and empiricism. 
By way of stimulating dynamic meteorologists to 
study the problem of evolution of mean states of the 
general circulation over periods as long as a month, the 
author desires to point out some indicative results of a 
statistical verification of thirty-day forecasts made 
twice monthly during the past five years and summa- 
rized by seasons. 
1. The average correlation coefficients between fore- 
cast and observed patterns of anomalies of the mean 
monthly 700-mb contours have been positive during 19 
out of 20 seasons over North America. 
2. The forecasts of monthly temperature anomaly 
over the United States (verified at 100 points) have been 
superior to climatological probability forecasts for 19 
out of 20 seasons. 
3. The forecasts of total monthly precipitation over 
the United States (verified at 100 points) have been 
superior to climatological probability forecasts during 
17 out of 20 seasons. 
THE COURSE AHEAD 
Viewed pessimistically, the present status of extended- 
range weather forecasting may appear to be hopelessly 
distant from perfection. It is in part this attitude which 
leads to the quest for stop-gap solutions. From the 
optimistic viewpoint, it appears that during the last 
decade notable advances have been made in under- 
standing as well as in forecasting the general circulation 
and its weather. These advances lie principally in in- 
terrelations between the great centers of action and 
have been made largely through study of mid-tropo- 
spheric patterns. This progress holds out the hope that 
forecast skill may be on the lower branch of an ex- 
ponentially imcreasmg curve which may subsequently 
turn into an asymptotic approach to perfection. 
Indeed, the problem of extended-range forecasting 
may be looked upon as the ultimate test of a complete 
theory of the general circulation. For this reason re- 
marks made elsewhere in this Compendium pertaining 
to the avenues of improvement of knowledge of the 
general circulation are directly applicable to the sub- 
ject of improvement in extended-range forecasting. 
In addition to completing basic studies, meteorol- 
ogists the world over would do well to improve the 
position of extended-range forecasting by consolidating 
their gains of the past score of years. Along this line, it 
would be desirable for those engaged in forecasting 
practice or research to make a greater effort to study 
and apply methods developed in other countries and to 
relate them to locally practiced techniques. This is a 
plea for greater international collaboration. 
Another less basic but highly practical problem is a 
WEATHER FORECASTING 
better method of representation of the tremendous 
wealth of data apparently necessary to make long- 
range forecasts. Similar questions involving time and 
space derivatives also arise in short-range forecasting. 
Perhaps a healthier state of cooperation more con- 
ducive to progress could be developed between the so- 
called dynamic meteorologists and the practicing fore- 
casters and empirical researchers. The ultimate goal of 
these groups is essentially the same—prediction, or 
understanding which leads to prediction. For this reason 
it is hard to reconcile attitudes of some dynamic me- 
teorologists that application (7.e., forecasting) is not 
their concern and that empirical, including statistical, 
knowledge is of little relevance if it does not fit certain 
classical concepts. Likewise, it is equally difficult to 
understand the philosophy of that group of practicing 
forecasters who look upon all theoretical work as com- 
pletely removed from everyday problems of weather 
forecasting. 
Given a prevailingly peaceful state of world affairs 
permitting international collaboration, the outlook for 
long-range weather forecastmg appears bright. In the 
opinion of the author, an incurable optimist, not only 
an increase in accuracy but also in the time range of 
general forecasts is probable. Forecasts for at least a 
season in advance and possibly a decade are within the 
grasp of the present generation. 
REFERENCES 
1. Baur, F., Musterbeispiele europdischer Grosswetterlagen. 
Wiesbaden, Dieterich, 1947. 
Hinfiihrung in die Grosswetterkunde. Wiesbaden, Diete- 
rich, 1948. 
3. Bysrrxnes, J., ‘Theorie der aussertropischen Zyklonen- 
bildung.” Meteor. Z., 54:462-466 (19387). 
4. Brooxs, C. E. P., “‘Annual Recurrences of Weather: 
Singularities.’’ Weather, 1:107-113, 130-134 (1946). 
5. Caurrornia INstTITUTE oF TECHNOLOGY, Drepr. METEOR., 
Synoptic Weather Types of North America. Pasadena, 
Calif., 1948. 
6. Haurwitz, B., ‘‘Final Report on the Use of Symmetry 
Points in the Pressure Curves for Long-Range Fore- 
casts.”? U. 8. Air Force, Air Wea. Serv. Tech. Rep. No. 
105-7 (1944). 
7. Kiemn, W. H., ‘‘Winter Precipitation as Related to the 
700-Mb Circulation.”? Bull. Amer. meteor. Soc., 29:489- 
453 (1948). 
8. —— “The Unusual Weather and Circulation of the 1948- 
49 Winter.’’ Mon. Wea. Rev. Wash., 77:99-113 (1949). 
9. Martin, D. E., and Hawkins, H. F., Jr., “Forecasting 
the Weather: The Relationship of Temperature and 
Precipitation over the United States to the Circulation 
Aloft.”? Weatherwise, 3:16-19, 40-48, 65-67, 89-92, 113- 
116, 138-141 (1950). 
10. Martin, D. B., and Lrreut, W. G., ‘Objective Tempera- 
ture Estimates from Mean Circulation Patterns.’’ Mon. 
Wea. Rev. Wash., 77:275-283 (1949). 
11. Namias, J., Hxtended Forecasting by Mean Circulation 
Methods. U. S. Weather Bureau, Washington, D. C., 
1947. 
12. —— “Characteristics of the General Circulation over the 
Northern Hemisphere during the Abnormal Winter 1946- 
47.’ Mon. Wea. Rev. Wash., 75:145-152 (1947). 
13. —— ‘Evolution of Monthly Mean Circulation and Weather 
Patterns.” Trans. Amer. geophys. Un., 29:777-788 (1948). 
