This data set, from the National Climatic Data Center (NCDC), contains hourly or 3-hourly surface weather observations, primarily measured at major airports and military bases. The stations are operated by the National Weather Service (NWS), the Federal Aviation Administration (FAA), the U.S. Air Force (Air Weather Service), and the U.S. Navy (Navy Weather Detachment). The NWS and FAA sites are located in the contiguous U.S., Alaska, Puerto Rico, Hawaii and other Pacific Islands. The Air Force and Navy operate stations worldwide; however, only a few are included in this set.

The observations are generally recorded midnight to midnight for the 24-hour period. The major data parameters are clouds, visibility, wind, temperature, sky cover, relative humidity, pressure, and descriptive weather. The earliest data is for 1938 but most stations begin in 1948. There are about 300 stations.

TD14 refers to the NCDC format of the original data up through 1983, which has been converted into a packed binary format; TD3280 refers to the ASCII format used at NCDC beginning with the 1984 data.

This set was retired from production at NCDC after 2005.