Subj : Wx Terms (T)(2) To : All From : Daryl Stout Date : Mon Aug 21 2017 12:05 am Theta-e (or Equivalent Potential Temperature) - The temperature a parcel of air would have if a) it was lifted until it became saturated, b) all water vapor was condensed out, and c) it was returned adiabatically (i.e., without transfer of heat or mass) to a pressure of 1000 millibars. Theta-e, which typically is expressed in degrees Kelvin, is directly related to the amount of heat present in an air parcel. Thus, it is useful in diagnosing atmospheric instability. Theta-e Ridge An axis of relatively high values of theta-e. Severe weather and excessive rainfall often occur near or just upstream from a theta-e ridge. THETAE Abbreviation for Theta-e; the temperature a parcel of air would have if a) it was lifted until it became saturated, b) all water vapor was condensed out, and c) it was returned adiabatically (i.e., without transfer of heat or mass) to a pressure of 1000 millibars. Theta-e, which typically is expressed in degrees Kelvin, is directly related to the amount of heat present in an air parcel. Thus, it is useful in diagnosing atmospheric instability. Thin Line Echo A narrow, elongated, non-precipitating echo. It is usually associated with thunderstorm outflows, fronts, or other density discontinuities. It is also known as a Fine Line. THK Thick/Thickness THN Thin Three-Hour Rainfall Rate This WSR-88D Radar product displays precipitation total (in inches) of the current and past two clock hours as a graphical image. It displays hourly precipitation total (in inches) as a graphical image (polar format with resolution 1.1 nm by 1 degree). It is updated once an hour. It is used to: 1) Assess rainfall intensities and amounts over a longer viewing interval; and 2) Possibly adjust flash flood guidance values since the product corresponds to the timing of Flash Flood Guidance values. Threshold Runoff In hydrologic terms, the runoff in inches from a rain of specified duration that causes a small stream to slightly exceed bankfull. When available, flood stage is used instead of slightly over bankfull. THRFTR Thereafter THRU Through THRUT Throughout THSD Thousand Thunder The sound caused by rapidly expanding gases in a lightning discharge. Thunderstorm A local storm produced by a cumulonimbus cloud and accompanied by lightning and thunder. Tidal Cycle The periodic changes in the intensity of tides caused primarily by the varying relations between the earth, moon, and sun. Tidal Piling Occurs when unusually high water levels occur as the result of an accumulation of successive incoming tides that do not completely drain due to opposing strong winds and/or waves. Tidal Wave See TSUNAMI TIDE On a buoy report, the water level in feet above or below Mean Lower Low Water (MLLW). Tide Anomaly Actual water level minus the prediction. Tide Prediction The computation of tidal highs and lows at a given location resulting from the gravitational interactions between the earth and primarily the moon and sun. Tides The periodic (occurring at regular intervals) variations in the surface water level of the oceans, bays, gulfs, and inlets. Tides are the result of the gravitiational attraction of the sun and the moon on the earth. The attraction of the moon is far greater than the attraction of the sun due to the close proximity of the earth and the moon. The sun is 360 times further from the earth than the moon. Therefore, the moon plays a larger role than the sun in producing tides. Every 27.3 days, the earth and the moon revolve around a common point. This means that the oceans and other water bodies which are affected by the earth-moon system experience a new tidal cycle every 27.3 days. Because of the physical processes which occur to produce the tidal system, there are two high tides and two low tides each day. Because of the angle of the moon with respect to the earth, the two high tides each day do not have to be of equal height. The same holds true for the two low tides each day. Tides also differ in height on a daily basis. The daily differences between tidal heights is due to the changing distance between the earth and the moon. Scientists use measurements of the height of the water level to examine tides and the various phenomena which influence tides, such as hurricanes and winter storms. TIL Until Tilt It describes a storm in which a line connecting the centroid of a mid level storm component to the centroid of the lowest storm component is to the right or the rear of the direction of motion. Tilt Sequence Radar term indicating that the radar antenna is scanning through a series of antenna elevations in order to obtain a volume scan. Tilted Storm A thunderstorm or cloud tower which is not purely vertical but instead exhibits a slanted or tilted character. It is a sign of vertical wind shear, a favorable condition for severe storm development. Tilted Updraft A thunderstorm updraft which is not purely vertical but instead exhibits a slanted or tilted character. It is a sign of vertical wind shear, a favorable condition for severe storm development. Tipping-Bucket Rain Gage A precipitation gage where collected water is funneled into a two compartment bucket; 0.01, 0.1 mm, or some other designed quantity of rain will fill one compartment and overbalance the bucket so that it tips, emptying into a reservoir and moving the second compartment into place beneath the funnel. As the bucket is tipped, it actuates an electric circuit. TKE Turbulent Kinetic Energy TMW Tomorrow TNDCY Tendency TNGT Tonight Toe of Dam (Upstream and Downstream) : The junction of the face of a dam with the ground surface. TOP Cloud Top Topography The shape of the land. TOR Tornado (or) Tornado Warning Tornado A violently rotating column of air, usually pendant to a cumulonimbus, with circulation reaching the ground. It nearly always starts as a funnel cloud and may be accompanied by a loud roaring noise. On a local scale, it is the most destructive of all atmospheric phenomena. Tornado Family A series of tornadoes produced by a single supercell, resulting in damage path segments along the same general line. Tornado Vortex Signature An image of a tornado on the Doppler radar screen that shows up as a small region of rapidly changing wind speeds inside a mesocyclone. The following velocity criteria is normally required for recognition: Velocity difference between maximum inbound and outbound (shear) is greater than or equal to 90 knots at less than 30 nmi and is greater than or equal to 70 knots between 30 and 55 nmi. It shows up as a red upside down triangle on the Storm Relative Velocity Display. Existence of a TVS strongly increases the probability of tornado occurrence, but does not guarantee it; therefore, the feature triggering it must be examined closely by the radar operator. A TVS is not a visually observable feature. --- þ Synchronet þ The Thunderbolt BBS - wx1der.dyndns.org .