The National Weather Service issued a tornado warning Monday evening for a part of Guadalupe County in eastern New Mexico where the estimated population was zero. A day later, several other tornado warnings were issued in the same state for populations nearly as low, with some estimated to be in the single digits.

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Tornado warnings are disseminated by the NWS based on radar-indicated rotation or visual confirmation of a tornado, regardless of location or population across the United States.

(MORE: The Most Tornado Prone Counties)

Zero-population tornado warnings are rare, but there have been other recent examples since the NWS graphical tornado warnings first went into use.

The High Plains in the central U.S. and the Florida Everglades are a couple potential candidates for a zero-population tornado warning. Both areas have a low population density and also experience tornadoes.

You may ask: Why bother issuing a tornado warning when the estimated population is zero?

It could be for the simple fact that we can't be 100 percent certain whether an unknown person is passing through the area of the tornado warning at that time. Also, the tornado-warned storm could eventually move into a more-populated area where another warning may be issued. Knowing a warning is in effect nearby could make residents or visitors in the adjacent unwarned location more vigilant if they are aware a potentially tornadic storm is moving in their direction.

Population estimates in NWS graphical tornado warnings are not simply based on census data. They use what is called the ambient population from the Landscan Ambient Population Dataset 2014 Edition 1.

"Ambient population refers to the population expected to be present in a grid box at any given time, regardless of residency," said the NWS.

(MORE: Why Some Tornadoes May Not Get Warned)

Prior to the implementation of storm-based warnings in 2007, tornado warnings were issued for entire counties. At that time, it would have been impossible to issue new tornado warnings with no people in them since all U.S. counties had at least some population as of the 2010 census. The least-populated county in the country as of 2010 was Loving County, Texas, where 82 people resided.

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