Terminology is important when discussing weather. The definitive source of weather-related definitions is the
National Weather Service Glossary.
National Weather Service Glossary
The
National Weather Services 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.
NWS Glossary:
https://w1.weather.gov/glossary/
Here are a couple of definitions that are key to our discussion tonight.
Weather
"The state of the atmosphere with respect to wind, temperature, cloudiness, moisture, pressure, etc. Weather refers to these conditions at a given point in time (e.g., today's high temperature)."
Think of "weather" as short-term conditions.
Climate
"The composite or generally prevailing weather conditions of a region, throughout the year, averaged over a series of years."
Think of "climate" as long-term average weather conditions.
Forecast
"A statement of prediction."
Think of a forecast as an educated prediction of the future.
Probability of Precipitation (PoP)
"The probability that precipitation will be reported at a certain location during a specified period of time."
The PoP does not tell you how much it will rain. Rather, the PoP tells you the probability that at least one point in the forecast area will receive measurable precipitation (typically, >=0.01").
Quantitative Precipitation Forecast (QPF)
"A spatial and temporal precipitation forecast that will predict the potential amount of future precipitation for a specified region, or area."
The forecast QPF tells you how much rain can be expected in an area over a specified period of time. QPFs are often summarized by 1, 3, 4, 6, 12 or 24 hour period, and sometimes these time increments of Day, Daytime, and Nighttime are used.
Precipitation
"The process where water vapor condenses in the atmosphere to form water droplets that fall to the Earth as rain, sleet, snow, hail, etc."
Rain
"Precipitation that falls to earth in drops more than 0.5 mm in diameter."
A component of precipitation.
Drizzle
"Precipitation consisting of numerous minute droplets of water less than 0.5 mm (500 micrometers) in diameter."
A component of precipitation.
Mist
"A visible aggregate of minute water particles
suspended in the atmosphere that reduces visibility to less than 7 statute miles, but greater than or equal to 5/8 statute miles. It does not reduce visibility as much as fog and is often confused with drizzle."
A component of precipitation.
Sleet
"Sleet is defined as pellets of ice composed of frozen or mostly frozen raindrops or refrozen partially melted snowflakes. These pellets of ice usually bounce after hitting the ground or other hard surfaces. Heavy sleet is a relatively rare event defined as an accumulation of ice pellets covering the ground to a depth of ½" or more."
A component of precipitation.
Snow
"Precipitation in the form of ice crystals, mainly of intricately branched, hexagonal form and often agglomerated into snowflakes, formed directly from the freezing [deposition] of the water vapor in the air."
A component of precipitation.
Hail
"Showery precipitation in the form of irregular pellets or balls of ice more than 5 mm in diameter, falling from a cumulonimbus cloud."
A component of precipitation.