912 
the Northern Hemisphere. Typhoons at times can be- 
come as big as any Aleutian or Icelandic lows. Such 
centers move quite slowly at times. Frequently they 
are entirely stationary for days, usually near latitudes 
25-30°. Evidently it is of greatest importance to fore- 
cast when such storms will stagnate and when and how 
they will resume motion. 
In the whole field of hurricane work, this topic has 
been left untouched more than any other. From both 
theoretical and practical viewpoints the difficulties have 
appeared to be almost insurmountable. Among the 
older literature only the work of Fujiwhara [14, 15] is 
applicable. He has taken up the problem of rotation of 
vortices about each other. If a storm is situated as de- 
scribed above, it will be flanked by other vortices east, 
west, south, and frequently even north, especially in 
the upper troposphere. A mean zonal motion does not 
exist at high levels. Attempts at forecasting must turn 
to the relation between the upper vortices. 
Theoretically, the problem of internal forces also 
moves into the foreground. This subject remained dor- 
mant until 1948. Since then two theoretical papers have 
appeared that treat the analysis of internal forces in 
vortices on the rotating earth [9, 34]. At this time, it is 
impossible to say how useful these particular papers 
will prove in practice, since again there are no direct 
data and application depends entirely on inference. 
But it is gratifying to note that the theoretical deadlock 
has been broken. Now that a way has been shown, 
dynamic meteorologists have a good opportunity to 
advance the understanding of the movement of large 
typhoons. 
On the practical side, recent studies of the high- 
tropospheric wind structure over the tropical oceans 
(27] and the interrelation between high- and low-lati- 
tude circulations [8] have produced an opening. The 
problem of large storms evidently can be solved only by 
considering the atmosphere over very wide areas. Events 
in the entire belt of polar westerlies, the motion of long 
waves in the westerlies, and the structure and movement 
of the high-tropospheric vortex train in low latitudes 
must determine the fate of typhoons of huge size. A 
southward shift of a westerly jet stream or its forma- 
tion in low latitudes, plus development of an extended 
trough near or west of a typhoon, might be favorable 
for acceleration of the typhoon into middle latitudes. 
Settling of a major ridge to its north could produce 
stagnation. These are merely suggestions which outline 
the direction which new efforts could take. 
CONCLUSION 
This report has tried to demonstrate briefly the cur- 
rent knowledge on structure, formation, and movement 
of tropical storms, shortcomings of this knowledge, and 
suggested paths for future research. The outstanding 
deficiency is the lack of observations which is so keenly 
felt in all low-latitude work. A network of upper-air 
data such as exists in the United States has never been 
at the disposal of the tropical analyst. Moreover, the 
quality of the high-level data is sometimes poor since 
errors in radiosonde flight evaluation can be as large as 
TROPICAL METEOROLOGY 
synoptic changes. If many upper-wind observations are 
taken, however, the quality of the reported heights and 
temperatures aloft can be judged easily. For this reason 
it is proposed to have as many rawins as possible and 
to revive the old and relatively inexpensive reports of 
middle- and high-cloud direction. 
For scientific purposes, detailed observational pro- 
grams should be initiated for short periods in low lati- 
tudes during the hurricane season. If this is done, it may 
be possible to derive analysis and forecast principles 
that are also applicable when less detailed data are at 
hand. The suggestions for the future take on several 
forms. Regarding structure, new observations and theo- 
retical studies alone can bring advances. Formation is 
a subject that for the present should be continued with 
standard qualitative synoptic methods plus theoretical 
calculations based on the empirical inferences. As the 
release of several forms of energy is involved, quantita- 
tive computations appear premature at this time. 
Methods of numerical integration are recommended for 
forecasting the movement of hurricanes by steering 
currents. Statistical correlations are most likely to yield 
an advance on the problem of recurvature. 
REFERENCES 
1. Bennamy, J. C., ‘“The Use of Pressure Altitude and Alti- 
meter Corrections in Meteorology.” J. Meteor., 2: 1-79 — 
(1945). 
2. Bserxnes, J., and Houmpog, J., ‘“‘On the Theory of Cy- 
clones.’’ J. Meteor., 1: 1-22 (1944). 
3. Brooks, C. HE. P., and Brasy, H. W., ‘‘The Clash of the 
Trades in the Pacific.”’ Quart. J. R. meteor. Soc., 47: 1-13 
(1921). 
4. Brunt, D., Physical and Dynamical Meteorology. Cam- 
bridge, University Press, 1939. 
5. Bunker, A. F., and others, ‘‘Vertical Distribution of Tem- 
perature and Humidity over the Caribbean Sea.” Pap. 
phys. Ocean. Meteor. Mass. Inst. Tech. Woods Hole ocean. 
Insin., Vol. 11, No. 1 (1949). 
6. Byers, H. R., General Meteorology. New York, McGraw, 
1944. 
7. —— and Brauam, R. R., Jr., ‘“Thunderstorm Structure 
and Circulation.” J. Meteor., 5: 71-86 (1948). 
8. Cressman, G. P., ‘‘Relations between High and Low Lati- 
tude Circulations.”’ Dept. Meteor. Univ. Chicago, Misc. 
Rep., No. 24, pp. 65-100 (1948). 
9. Daviss, T. V.,‘‘Rotatory Flow on the Surface of the Earth. 
Part I—Cyclostrophic Motion.” Phil. Mag., Ser. 7, 39: 
482-491 (1948). 
10. DeppERmMaNN, C. E., Some Characteristics of Philippine 
Typhoons, 143 pp. Manila, Bureau of Printing, 1939. 
11. —— ‘Notes on the Origin and Structure of Philippine 
Typhoons.”’ Bull. Amer. meteor. Soc., 28: 399-404 (1947). 
12. Duwn, G. E., ‘“‘Aerology in the Hurricane Warning Serv- — 
ice.”” Mon. Wea. Rev. Wash., 68: 303-315 (1940). 
13. Durst, C. 8., and Sutctirre, R. C., ‘‘The Importance of 
Vertical Motion in the Development of Tropical Re- 
volving Storms.” Quart. J. R. meteor. Soc., 64: 75-84 
(1938). 
14, Fustwuara, S., ‘‘The Natural Tendency Towards Sym- 
metry of Motion and Its Application as a Principle of 
Meteorology.”’ Quart. J. R. meteor. Soc., 47: 287-293 
(1921). 
15. —— “On the Growth and Decay of Vortical Systems.” 
Quart. J. R. meteor. Soc., 49: 75-104 (1923). 
