CONTEIBUTIONS TO METEOROLOGY. 

 Table XV — Comparison of storm paths with wind directions. 



33 



Column 1 shows the longitudes for which the comparisons are made; column 2 shows the 

 latitude of the points to which the direction of the storm tracks correspond; column 3 shows the 

 average direction of the storm tracks for the months of Januaiy, April, July, and October; column 

 4 shows the latitudes corresponding to the wind directions from Table XIV; column 5 shows the 

 direction of the wind for the given latitudes and longitudes, according to the United States 

 Hydrographic charts ; column 6 shows the differences of latitude between the points to which the 

 storm tracks correspond and those to which the wind directions correspond; column 7 shows the 

 dift'ereuce between the average direction of the wind and the average direction of the storm paths 

 for the points of comi)arison. 



47. It will be seen that there is an average ditference of nearly five degrees between the 

 latitudes of the points for which the wind directions are given and those to which the storm tracks 

 correspond. I have endeavored to deduce from Table XIII the proper correction of the wind 

 directions for this difference of latitude, but the corrections appear so questionable that I have 

 made no use of them. 



We see that for the middle of the Atlantic Ocean, near the parallel of 50°, the average direc- 

 tion of storm paths corresponds verj^ closely with that of the average progress of the wind; 

 but in the western part of the Atlantic the average course of storms is considerably more 

 northerly than that of the wind, while in the eastern part it is more southerly. These results 

 accord very well with those derived from tropical storms, and seem to indicate that in the middle 

 latitudes of the northern hemisphere the direction of progress of storm centers is not identically 

 the same as that of the average wind, but is sensibly aflected by some other cause or causes; and 

 the results derived from observations in the China Sea seem to indicate that one of these causes 

 is the prevalent direction of the wind which follows immediately after a storm. 



48. An examination of the maps accompanying the monthly weather review of the United 

 States Signal Service, which exhibit the tracks of storm centers, shows that between the Eocky 

 Mountains and the meridian of 90° Irom Greenwich storms frequently travel towards the south- 

 east. I have made a oareiul examination of the observations from this region, to determine 

 whether the storm tracks of this region conform to the average direction of the winds. Table XVI 

 shows the wind observations for twelve of the Signal Service stations in this region, for the three 

 winter months, for the ten years from 1873 to 1882. Iliave restricted the comparison to the winter 

 mouths, because during this period the winds are stronger and the northerly motion is more decided 

 than during the warmer months of the year. The table shows for each station the sum of the 

 observations for the year comi)ared, and also the resulting course computed from the observations. 



49. 1 next measured with a protractor, for each of the twelve stations, the direction of the 

 storm paths as delineated on the monthly maps of the Signal Service for the winter mouths, during 

 a period of ten years, from 1875 to 1884. I have omitted the observations of the two or three 

 preceding years, because the storm tracks of this region are not as well delineated for those years 

 as for the subsequent years. Table XVII shows the average results of these measurements and 

 also the results derived from Table XVI. The directious are all measured from the north point 

 towards the east. 



S. Mis. 154 5 



