National Weather Service Glossary
This glossary contains information on more than 2000 terms, phrases and abbreviations used by the NWS. Many of these terms and abbreviations are used by NWS forecasters to communicate between each other and have been in use for many years and before many NWS products were directly available to the public. It is the purpose of this glossary to aid the general public in better understanding NWS products.
You can either type in the word you are looking for in the box below or browse by letter.
Browse by letter:
Here are the results for the letter Z
- Zulu time; the same as Universal Coordinated Time (UTC), i.e. 18z is the same as 18:00 UTC.
- Zero Datum
- In hydrologic terms, a reference "zero" elevation for a stream or river gage. This "zero" can be referenced (usually within ten feet of the bottom of the channel) to mean sea level, or to any other recognized datum.
- Zone Forecast Product
- Freezing Drizzle
- Zonal Flow
- Large-scale atmospheric flow in which the east-west component (i.e., latitudinal) is dominant. The accompanying meridional (north-south) component often is weaker than normal. Compare with meridional flow.
- Zone of Aeration
- In hydrologic terms, the locus of points just above the water table where soil pores may either contain air or water. This is also called the vadose zone
- Zone of Saturation
- In hydrologic terms, the locus of points below the water table where soil pores are filled with water. This is also called the phreatic zone
- Zoned Embankment Dam
- In hydrologic terms, an embankment dam which is comprised of zones of selected materials having different degrees of porosity, permeability and density.
- Freezing Rain
- Zulu (Z) Time
- For practical purposes, the same as Coordinated Universal Time (UTC). The notation formerly used to identify time Greenwich MeanTime. The word "Zulu" is notation in the phonetic alphabet corresponding to the letter "Z" assigned to the time zone on the Greenwich Prime Meridian.
- Zurich Sunspot Classification
- In solar-terrestrial terms, a sunspot classification system that has been modified for SESC use.
- Z\/R Relationship
- An empirical relationship between radar reflectivity factor z (in mm^6 / m^3 ) and rain rate ( in mm / hr ), usually expressed as Z = A R^b; A and b are empirical constants.