errorError The difference between a measured value of a quantity and its true value. Different types of errors are inherent to observations.
EruptiveIn solar-terrestrial terms, solar activity levels with at least one radio event (10 cm) and several chromospheric events per day (Class C Flares).
Eruptive Prominence on Limb (EPL)In solar-terrestrial terms, a solar prominence that becomes activa- ted and is seen to ascend from the sun.
EstuaryA water body where salt and fresh water meet resulting in brackish water. These areas usually have associated marshlands and are critical nursery and…
Esturine watersDeepwater tidal habitats and tidal wetlands that are usually enclosed by land but have access to the ocean and are at least occasionally diluted by…
Esturine ZoneThe area near the coastline that consists of estuaries and coastal saltwater wetlands.
ETA1. The Eta Model, now referred to as North Amercian Meso (NAM) an 84-hour numerical model of the atmosphere run four times daily by NCEP.
Eta ModelNow referred to as North Amercian Meso (NAM) is one of the operational numerical forecast models run at NCEP.
Ethanol (C2 5OH)Otherwise known as ethyl alcohol, alcohol, or grain spirit. A clear, colorless, flammable oxygenated hydrocarbon with a boiling point of 78.
EvaporationThe conversion of a liquid to a vapor (gas), usually by means of heat.
Evaporation PanA pan used to hold water during observations for the determination of the quantity of evaporation at a given location.
Evaporation RateIn hydrologic terms, the quantity of water, expressed in terms of depth of liquid water, which is evaporated from a given surface per unit of time.
Evaporation-mixing FogFog that forms when the evaporation of water raises the dew point of the adjacent air.
EvaporimeterAn instrument which measures the evaporation rate of water into the atmosphere.
EvapotranspirationThe net water loss (in vapour form) per unit area of land, both directly from the land surface, and indirectly through transpiring leaves.
EWWExtreme Wind Warning (EWW) inform the public of the need to take immediate shelter in an interior portion of a well-built structure due to the onset of…
Excess RainEffective rainfall in excess of infiltration capacity.
Excessive HeatExcessive heat occurs from a combination of high temperatures (significantly above normal) and high humidities.
Excessive Heat OutlookThis CPC product, a combination of temperature and humidity over a certain number of days, is designed to provide an indication of areas of the country…
Excessive Heat WarningIssued within 12 hours of the onset of the following criteria: heat index of at least 105F for more than 3 hours per day for 2 consecutive days, or heat…
Excessive Heat WatchIssued by the National Weather Service when heat indices in excess of 105F (41C) during the day combined with nighttime low temperatures of 80F (27C) or…
Exit RegionThe region downstream from a wind speed maximum in a jet stream (jet max), in which air is moving away from the region of maximum winds, and therefore is…
ExosphereThe upper most layer of the earth's atmosphere; the only layer where atmospheric gases can escape into outer space.
Experimental ProductAn experimental product is in the final stages of testing and evaluation. If the product proves accurate and valuable to users then the next step is to…
Explosive DeepeningA decrease in the minimum sea-level pressure of a tropical cyclone of 2.5 mb/hr for at least 12 hours or 5 mb/hr for at least six hours.
Exponential growthGrowth in which some quantity, such as population size, increases by a constant percentage of the whole during each year or other time period; when the…
Extended Forecast DiscussionThis discussion is issued once a day around 2 PM EST (3 PM EDT) and is primarily intended to provide insight into guidance forecasts for the 3- to 5-day…
external dataData whose origin is not from within the ARM Program; may include data observed at ARM facilities, but whose processing and quality control is done by…
External Data Center (XDC)Stores data from non-ARM sources. It is managed by Brookhaven National Laboratory.
external instrumentsInstruments that belong to organizations that are outside of the ARM Program.
Extraterrestrial RadiationThe theoretically-calculated radiation flux from the sun at the top of the atmosphere, before losses by atmospheric absorption.
ExtratropicalA term used in advisories and tropical summaries to indicate that a cyclone has lost its "tropical" characteristics.
Extratropical CycloneA cyclone in the middle and high latitudes often being 2000 kilometers in diameter and usually containing a cold front that extends toward the equator for…
Extratropical LowA low pressure center which refers to a migratory frontal cyclone of middle and higher latitudes.
extreme event timeThe time of extreme meteorological events such as min/max temperature and wind gusts.
Extreme Ultraviolet (EUV)A portion of the electromagnetic spectrum from approximately 100 to 1000 angstroms.
Extreme Wind WarningExtreme Wind Warning (EWW) inform the public of the need to take immediate shelter in an interior portion of a well-built structure due to the onset of…