| At ________ during the Month of ________. | ||||||||||
| N. | NE. | E. | SE. | S. | SW. | W. | NW. | Totals | Percentages | |
| Clear | D | J | ||||||||
| Fair | F | K | ||||||||
| Cloudy | G | L | ||||||||
| Rain and Snow | H | M | ||||||||
| Totals | A | |||||||||
| Percentages | B | C | etc. | |||||||
Count every observation of rain or snow also as cloudy, for it usually rains or snows only when the sky is cloudy. Continue your observations on all the maps for the month you have chosen. Then count up the whole number of cases of clear weather you have found with north winds, and write down this sum in the first space, in the column reserved for N. winds. Do the same with fair and cloudy weather. Add up and enter at the bottom of the column in the space marked Totals the whole number of observations of clear, fair, and cloudy weather you have observed with N. winds. Then find what percentage of the weather with N. winds was clear, and enter this percentage next to the sum of clear weather observations, in the first division in the column headed N. Do the same for fair, cloudy, and rainy or snowy weather, deriving the percentages of rain or snow from the total of clear and fair and cloudy. Repeat
this process of summarizing in every column. Your results will then show the percentages of the different kinds of weather noted with the different wind directions.
The lower division of the table and the last two columns on the right are to be used for a general summary of the whole investigation. By adding together all the totals of clear, fair, and cloudy weather observed with all the eight wind directions you obtain the whole number of observations you have made. Enter this in the space marked A, at the right of the table. From this grand total and the total number of observations in each column you may find (in percentages) the relative frequencies of the different wind directions. These should be entered under the totals at the bottom of each column, in the spaces marked Percentages (spaces B, C, etc.). The total number of observations of clear, fair, cloud, and rain or snow, noted with all the wind directions, are to be entered in spaces D, F, G, and H, at the right of the table. From these totals, and from the grand total in space A, we can determine the relative frequency (in percentages) of each kind of weather during the month. These results should be entered in spaces J, K, L, and M.
Study these results carefully. Formulate them in a brief written statement. Express graphically the following:—
A. The percentages of frequency of the different wind directions during the month.
B. The percentages of the different kinds of weather noted during the whole month for all wind directions.
Fig. 51.
A wind rose, indicating the percentages of frequency of different winds during a month, or