Subj : Wx Terms (I)(1) To : All From : Daryl Stout Date : Sun Sep 10 2017 12:04 am Ice Age A time of widespread glaciation. Ice Boom In hydrologic terms, a floating structure designed to retain ice. Ice Bridge In hydrologic terms, a continuous ice cover of limited size extending from shore to shore like a bridge. Ice Crystals A barely visible crystalline form of ice that has the shape of needles, columns or plates. Ice crystals are so small that they seem to be suspended in air. Ice crystals occur at very low temperatures in a stable atmosphere. Ice Fog Same as Freezing Fog; a suspension of numerous minute ice crystals in the air, or water droplets at temperatures below 0ø Celsius, based at the Earth's surface, which reduces horizontal visibility; also called ice fog. Ice Gorge In hydrologic terms, the gorge or opening left in a jam after it has broken. Ice Jam In hydrologic terms, a stationary accumulation that restricts or blocks streamflow. Ice Nucleus Any particle that serves as a nucleus in the formation of ice crystals in the atmosphere. Ice Pellets (abbrev. IP) Same as Sleet; 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 1" or more. Ice Push In hydrologic terms, compression of an ice cover particularly at the front of a moving section of ice cover. Ice Run In hydrologic terms, flow of ice in a river. An ice run may be light or heavy, and may consist of frazil, anchor, slush, or sheet ice. Ice Shove In hydrologic terms, on-shore ice push caused by wind, and currents, changes in temperature, etcetera. Ice Storm An ice storm is used to describe occasions when damaging accumulations of ice are expected during freezing rain situations. Significant accumulations of ice pull down trees and utility lines resulting in loss of power and communication. These accumulations of ice make walking and driving extremely dangerous. Significant ice accumulations are usually accumulations of 1" or greater. Ice Storm Warning This product is issued by the National Weather Service when freezing rain produces a significant and possibly damaging accumulation of ice. The criteria for this warning varies from state to state, but typically will be issued any time more than 1/4" of ice is expected to accumulate in an area. Ice Twitch In hydrologic terms, downstream movement of a small section of an ice cover. Ice twitches occur suddenly and often appear successively. Iceberg A piece of a glacier which has broken off and is floating in the sea. Icelandic Low A semi-permanent, subpolar area of low pressure in the North Atlantic Ocean. Because of its broad area and range of central pressure, it is an area where migratory lows tend to slow down and deepen. It is strongest during a Northern Hemisphere winter and early spring, centered over Iceland and southern Greenland, and is the dominate weather feature in the area. During the summer, it is weaker, less intense, and might divide into two parts, one west of Iceland, the other over the Davis Strait between Greenland and Baffin Island. Then the Azores or Bermuda High becomes the dominate weather feature in the North Atlantic. Icing A coating of ice on a solid object. Ideal Gas Laws The thermodynamic laws applying to perfect gases. IFR Instrument Flight Rules Impermeable Material that does not permit fluids to pass through it. Impervious In hydrologic terms, the ability to repel water, or not let water infiltrate. IMPL Impulse- Alternate term for Upper Level System and Shortwave; a general term for any large-scale or mesoscale disturbance capable of producing upward motion (lift) in the middle or upper parts of the atmosphere. Import In hydrologic terms, water piped or channeled into an area. IMPT Important Impulse (abbrev. IMPL) Alternate term for Upper Level System and Shortwave; a general term for any large-scale or mesoscale disturbance capable of producing upward motion (lift) in the middle or upper parts of the atmosphere. in Hg Inches of Mercury In-Cloud Lightning (abbrev. IC) Lightning that takes place within the cloud. Inactive Storage Capacity In hydrologic terms, the portion of capacity below which the reservoir is not normally drawn, and which is provided for sedimentation, recreation, fish and wildlife, aesthetic reasons, or for the creation of a minimum controlled operational or power head in compliance with operating agreements or restrictions. Inch-Degrees The product of rainfall (in inches) multiplied by the temperature (in degrees Fahrenheit) above freezing. Used as a measure of the snowmelting capacity of rainfall. Inches of Mercury (or in Hg) Unit of atmospheric pressure used in the United States. The name comes from the use of mercurial barometers which equate the height of a column of mercury with air pressure. One inch of mercury is equivalent to 33.86 millibars or 25.40 millimeters. See barometric pressure. First divised in 1644 by Evangelista Torricelli (1608-1647), an Italian physicist and mathematician, to explain the fundamental principles of hydromechanics. To convert millibars (mb) to inches of mercury (in Hg), divide the millibar reading by 33.86: in Hg = mb / 33.86 Inches of Runoff In hydrologic terms, the volume of water from runoff of a given depth over the entire drainage. INCR Increase INDC Indicate Index of Wetness The ratio of precipitation for a given year over the mean annual precipitation. Indian Summer An unseasonably warm period near the middle of autumn, usually following a substantial period of cool weather. Indirect Hit Generally refers to locations that do not experience a direct hit from a tropical cyclone, but do experience hurricane force winds (either sustained or gusts) or tides of at least 4 feet above normal. Industrial Consumption The quantity of water consumed in a municipality or district for mechanical, trade, and manufacturing purposes, in a given period, generally one day. The per capita use is generally based on the total population of the locality, municipality, or district. Infiltration In hydrologic terms, movement of water through the soil surface into the soil. Infiltration Capacity In hydrologic terms, the maximum rate at which water can enter the soil at a particular point under a given set of conditions. Infiltration Index In hydrologic terms, an average rate of infiltration, in inches per hour, equal to the average rate of rainfall such as that the volume of rainfall at greater rates equals the total direct runoff. Infiltration Rate In hydrologic terms, (1) The rate at which infiltration takes place expressed in depth of water per unit time, usually in inches per hour. (2) The rate, usually expressed in cubic feet per second, or million gallons per day per mile of waterway, at which ground water enters an infiltration ditch or gallery, drain, sewer, or other underground conduit. --- þ Synchronet þ The Thunderbolt BBS - wx1der.dyndns.org .