In solar-terrestrial terms, this absorption line of neutral hydrogen falls in the red part of the visible spectrum and is convenient for solar observations. The H-alpha line is universally used for patrol observations of solar flares.
- Browse Related Terms: Active Longitude, Active Region (AR), burst, Comprehensive Flare Index (CFI), H-Alpha, Homologous Flares, Hyder Flare, Limb Flare, Loop Prominence System, LPS, Magflare, Microwave Burst, Post-Flare Loops, White Light Flare, X-Ray Background, X-Ray Burst, X-Ray Flare Class
(Geomagnetic Elements) In solar-terrestrial terms, the components of the geomagnetic field at the surface of the earth. In SESC use, the northward and eastward components are often called the H and D components, where the D component is expressed in gammas and is derived from D (the declination angle) using the small angle approximation.
- Browse Related Terms: ASAPTRAN, BR, Crochet, Direct Solar Radiation, Fugitive dust, Geomagnetic Elements, Geomagnetic Storm, H-component of the Geomagnetic Field, Magnetic Bay, NWD, RDS, RTRN, Sudden Commencement (SC), Sudden Impulse (SI+ or SI-)
500 millibar level height (in a standard atmosphere this is near 5,500 meters (18,000 ft)
- Browse Related Terms: Altimeter Setting, COR, Geopotential Height, Growler, H5, H7, H8, Height, MB, Sea Level Pressure
height of the 700 millibar level. In a standard atmosphere this is near 3,000 meters (10,000 ft)
- Browse Related Terms: Altimeter Setting, COR, Geopotential Height, Growler, H5, H7, H8, Height, MB, Sea Level Pressure
height of the 850 millibar level.
- Browse Related Terms: Altimeter Setting, COR, Geopotential Height, Growler, H5, H7, H8, Height, MB, Sea Level Pressure
The North Atlantic boundary between the U.S. and Canada fishing waters as determined by the World Court in The Hague, Netherlands.
- Browse Related Terms: Alaska Current, Aleutian Current, Antilles Current, Azores Current, Hague Line, N, NC, PNA, Rex Block, Typhoon Season
Showery precipitation in the form of irregular pellets or balls of ice more than 5 mm in diameter, falling from a cumulonimbus cloud.
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A limitation in NEXRAD rainfall estimates whereby abnormally high reflectivities associated with hail are converted to rainfall rates and rainfall accumulations. These high reflectivity values are mistaken by the radar for extremely heavy rain, thus "contaminating" (inflating) its estimation of how much rain has fallen over the affected area.
- Browse Related Terms: Hail Contamination, Hail Spike, Inch-Degrees, Partial Beam Filling, POH, Precipitation Mode, Probability of Hail, Radar Data Acquisition, Radar Mosaic, Radar Product Generator (RPG), Rainfall Estimates, SHARS, Storm Total Precipitation
An indication of whether the thunderstorm structure of each storm identified is conducive to the production of hail.
- Browse Related Terms: Dense Fog Advisory, Frost Advisory, Hail Index, Red Flag, WDSPRD
Typically refers to the diameter of the hailstones. Warnings and reports may report hail size through comparisons with real-world objects that correspond to certain diameters:
Description Diameter (inches) Pea 0.25 Marble or Mothball 0.50 Penny or Dime 0.75 Nickel 0.88 Quarter 1.00 Half Dollar 1.25 Walnut or Ping Pong Ball 1.50 Golfball 1.75 Hen's Egg 2.00 Tennis Ball 2.50 Baseball 2.75 Tea Cup 3.00 Grapefruit 4.00 Softball 4.50 - Browse Related Terms: AOPA, Hail Size, METAR, Non-Uniform Sky Condition, Non-Uniform Visibility, Pilot Report, PIREP, RPRT
An area of reflectivity extending away from the radar immediately behind a thunderstorm with extremely large hail. In an area of large hail, radiation from the radar can bounce from hailstone to hailstone before being reflected back to the radar. The time delay between the backscattered radiation from the storm and the bounced and scattered radiation from the large hail causes the reflectivity from the hail to appear to come from a farther range than the actual storm.
- Browse Related Terms: Hail Contamination, Hail Spike, Inch-Degrees, Partial Beam Filling, POH, Precipitation Mode, Probability of Hail, Radar Data Acquisition, Radar Mosaic, Radar Product Generator (RPG), Rainfall Estimates, SHARS, Storm Total Precipitation
This is also called the Lower Atmosphere Stability Index. It is computed from the morning (12Z) soundings from RAOB stations across North America. The index is composed of a stability term and a moisture term. The stability term is derived from the temperature difference at two atmosphere levels. The moisture term is derived from the dew point depression at a single atmosphere level. This index has been shown to be correlated with large fire growth on initiating and existing fires where surface winds do not dominate fire behavior. The Haines Indices range from 2 to 6 for indicating potential for large fire growth
- Browse Related Terms: Delta T, Dew Point Depression, DP, Haines Index, Isentropic Surface, Isodrosotherm, Isopleth, Isotherm, K-Index, Moisture Ridge, Nieve Penitente, Radiation Fog, Total-Totals Index
Any of a variety of bright circles or arcs centered on the sun or moon, caused by the refraction or reflection of light by ice crystals suspended in the earth's atmosphere and exhibiting prismatic coloration ranging from red inside to blue outside.
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In hydrologic terms, a mass of ice composed mainly of frazil or broken ice deposited underneath an ice cover in a region of low flow velocity.
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A narrative statement produced by the National Weather Service, frequently issued on a routine basis, to provide information regarding the potential of significant weather expected during the next 1 to 5 days.
- Browse Related Terms: Air Stagnation Advisory, Brisk Wind Advisory, Daily Climatological Report, Excessive Heat Watch, FAWS, Hazardous Weather Outlook, Heavy Surf Advisory, Monthly Climatological Report, Record Event Report, Severe Local Storm Watch, Significant Weather Outlook, Special Avalanche Warning
CPC's Hazards Assessment provides emergency managers, planners, forecasters and the public advance notice of potential hazards related to climate, weather and hydrological events.
- Browse Related Terms: A, B, CL, Climate Diagnostics Bulletin, Climatological Outlook, Drought Assessments, ENSO Diagnostic Discussion, Hazards Assessment, OTLK, PWO, SWODY2
(abbrev. HZ)- An aggregation in the atmosphere of very fine, widely dispersed, solid or liquid particles, or both, giving the air an opalescent appearance that subdues colors.
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Heating Degree Days- A form of degree day used to estimate energy requirements for heating. Typically, heating degree days are calculated as how much colder the mean temperature at a location is than 65°F on a given day. For example, if a location experiences a mean temperature of 55°F on a certain day, there were 10 HDD (Heating Degree Days) that day because 65 - 55 = 10.
- Browse Related Terms: C, CDD, Cooling Degree Days, Degree Day, HDD, Heating Degree Days, Supercooled Liquid Water
An Hourly Digital Rainfall Product of the WSR-88D.
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