Part 13

A very slow fall from a high point is usually connected with wet and unpleasant weather without much wind.

The following table of the United States Weather Bureau gives a summary of the wind and barometer indications:

Barometer Reduced to Sea Level Wind Character of Weather Indicated Direction

─────────────────────────────────────────────────────────────────────── 30.10 to 30.20 and steady SW to NW Fair with slight temperature changes for 1 to 2 days 30.10 to 30.20 and rising SW to NW Fair, followed within 2 days rapidly by warmer and rain 30.10 to 30.20 and falling SW to NW Warmer, with rain in 24 to 36 slowly hours 30.10 to 30.20 and falling SW to NW Warmer, with rain in 18 to 24 rapidly hours 30.20 and above and stationary SW to NW Continued fair, with no decided temperature change 30.20 and above and falling SW to NW Slowly rising temperature and slowly fair for two days 30.10 to 30.20 and falling S to SE Rain within 24 hours slowly 30.10 to 30.20 and falling S to SE Wind increasing in force, with rapidly rain within 12 to 24 hours 30.10 to 30.20 and falling SE to NE Rain in 12 to 18 hours slowly 30.10 to 30.20 and falling SE to NE Increasing wind, with rain rapidly within 12 hours 30.10 and above and falling E to NE In summer, with light winds, slowly rain may not fall for several days. In winter, rain within 24 hours 30.10 and above and falling E to NE In summer, rain probably rapidly within 12 to 24 hours. In winter, rain or snow, with increasing wind will often set in, when the barometer begins to fall and the wind sets in from the NE 30 or below and falling slowly SE to NE Rain will continue 1 or 2 days 30 or below and falling SE to NE Rain, with high wind, followed rapidly within 24 hours by clearing and cooler 30 or below and rising slowly S to SW Clearing within a few hours and continued fair for several days 29.80 or below and falling S to E Severe storm of wind and rain rapidly or snow imminent, followed within 24 hours by clearing and colder 29.80 or below and falling E to N Severe northeast gales and rapidly heavy rain or snow, followed in winter by a cold wave 29.80 or below and rising Going to Clearing and colder rapidly W

A sudden fall indicates a sudden shower or high winds, or both.

Courtesy Julien Friez & Son Baltimore, Md.

Fig. 49 U. S. STANDARD RAIN GAUGE ]

A stationary barometer indicates a continuance of existing weather conditions. (Note: Tap the barometer slightly on the face. If the hands move a trifle, it indicates that there is the tendency to rise or fall, depending upon the direction of movement of the hands.)

Northeasterly winds precede storms that approach from the southwest; that is, in New England and the Middle States and the Ohio Valley. Southeasterly winds precede storms that approach from the Lake region.

THERMOMETERS

For information regarding the manufacture of thermometers, we recommend P. R. Jameson’s book, “Weather and Weather Instruments,” published by the Taylor Instrument Companies of Rochester, N. Y.

Thermometers are of great importance to us in determining weather.

LOCATION OF THERMOMETERS

1. They must be properly exposed.

2. A good circulation of air around them is necessary.

3. They must be properly protected from the rays of the sun.

Note: If these instructions are not carefully followed out, errors are apt to occur, and you will be misled.

For a change of wind towards northerly directions, a thermometer falls. For a change of wind toward southerly directions a thermometer rises.

Fig. 50

GILBERT RAIN GAUGE ]

MAXIMUM AND MINIMUM THERMOMETERS

Maximum and minimum thermometers are used to record the daily maximum and minimum temperatures. Fig. 46 shows a typical maximum and minimum thermometer used for giving the extremes of temperature. One side of the thermometer has a scale reading, beginning at the top, from 60° below zero to 140° above zero. This is the scale used when determining the coldest temperature reached during a day. The other side of the thermometer has a scale marked from 70° below zero, beginning at the bottom and reading up, to 130° above zero. On this side the maximum heat reached during the day is recorded. There is a small metal piece in the tubes, one on each side, and as the mercury pushes ahead or recedes, the small index is left at the lowest point reached in one tube and at the highest point reached in the other. The small metal piece is drawn back to the level of the mercury by means of a small magnet.

WHEN MAXIMUM TEMPERATURE IS REACHED

You can generally look for maximum temperature between three and four o’clock in the afternoon. At this time the sun has reached its highest altitude.

Courtesy Julien Friez & Sons, Baltimore, Md.

Fig. 51

TIPPING BUCKET RAIN GAUGE ]

WHEN THE MINIMUM TEMPERATURE IS REACHED