Before a forecast can be written, there must be data. Temperature, air pressure, relative humidity in the atmosphere, what type of clouds, fog, rain, and all the other elements that make up our daily weather conditions are observed, recorded and transmitted. Thomas Jefferson and Benjamin Franklin noticed that the weather conditions in Philadelphia often reached New York later while the men exchanged letters. In 1776, Thomas Jefferson began to recruit volunteer weather observers throughout Virginia. By 1800, there were volunteers in five other states across the newborn nation. They included Massachusetts, Pennsylvania, Connecticut, New York and North Carolina. In 1891, the network of voluntary weather observers across the country had grown to 2,000 stations. Just prior to the Civil War, in the 1850s, the US Signal Corp picked up the duty of weather observations and gathering data. This network became the roots of the Weather Bureau.

The basic instruments used by the NWS are still the thermometer for air temperature and humidity; the anemometer for wind speed, the wind vane for wind direction; the barometer for air pressure, and an eye to the sky (now a computer-eye) to determine the clouds, the visibility, and the current weather conditions. But how those instruments have changed over the years.


Maximum and minimum thermometers inside the old Cotton Region Thermoscreen Instrument Shelter
MMTS - Replacement for the old mercury thermometers, the digital readout for the maximum and minimum temperatures moved indoors.


ASOS wind system


Mercurial Barometer - the standard for determining air pressure. Removed from all NWS weather stations now because of danger of mercury contamination.
Paro-Scientific precision barometer


Observations as they used to be, manually gathering different data fields to encode and transmit, and always keeping an eye to the sky.
ASOS - Automated Surface Observation System - A computerized and fully automatic observation system that monitors all elements, including the height and amount of the lower clouds.


For additional information:


NWS Jackson Home Page

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