Training Guide in Surface Weather Observations - Multiple Choices

Figure 6-8. Reading a Thermometer to Avoid Parallax Error.
To set (reset) the maximum thermometer, start with the bulb end lowered and
whirl it rapidly, allowing it to spin freely until it comes to rest. Repeat the
whirling if necessary until the mercury will not retreat farther into the bulb;
that is, until the column is no longer separated at or below the constriction.
See Figure 6-9.
Move the catch on the support until it touches the longer shaft. Carefully
elevate the bulb end of the thermometer until the catch locks the shaft in place
on the support. The thermometer is now “set.” It is ready to indicate the
maximum temperature that occurs before it is set again in the same manner.
6.7.5 Reporting Procedures for Maximum and Minimum Temperatures
6-11
Figure 6-9. Maximum
Thermometer Before and
After Whirling
At designated stations, maximum and minimum temperatures shall be reported as additive data in the
remarks section in the 0000, 0600, 1200, and 1800 UTC and 0000 LST observations. The following
steps are used to determine maximum and minimum temperatures. Use the procedure applicable to your
instruments as a guide until you are familiar with the procedures involved. Figure 6-10 illustrates the
method of recording these temperature extremes on MF1M-10C.
6.7.5.1 Reporting Maximum and Minimum Temperatures Using Max./Min. Thermometers
1. Without disturbing the thermometer, read the minimum temperature to the nearest 1/10 of a
degree at the end of the colored glass index farthest from the bulb.
2. Release the catch of the maximum thermometer on the support and lower the bulb end slowly
until the thermometer is vertical.
3. Read the thermometer to the nearest 1/10 of a degree.
4. Spin the thermometer until its reading is the same as the current dry-bulb temperature.