A bureau within the U.S. Department of Commerce   
NOAA logo - Click to go to the NOAA homepage National Weather Service   NWS logo - Click to go to the NWS homepage
Warning Decision Training Branch (Click Here to return to WDTB Home.)
 
 


 

WDTB Glossary

A|B|C|D|E|F|G|H|K|L|M|N|O|P|Q|R|S|T|U|V|W

8

8-Bit Products - Radar base products that display data in 256 levels, in contrast with other products that display data in 16 (4-bit) or 8 (3-bit) data levels.

A

Above Ground Level (AGL) - An expression used with height measurements to indicate the measurement is for the heigh above the ground at that location (in constrast to above mean sea level or above radar level).

Advanced Warning Operations Course (AWOC) - The Advanced Warning Operations Course is a blended learning course designed to provide every NWS Forecaster (Meteorologist and Hydrologist) training on advanced warning decision making techniques.

Advanced Weather Interactive Processing System (AWIPS) - The AWIPS is the hardware and software the NWS uses to acquire, process, view, and store data from numerous sources (including those products received from the RPG).

Algorithm - A step-by-step procedure for solving a mathematical problem. The WSR-88D relies on algorithms while producing derived products.

American Meteorological Society (AMS) - A professional organization that serves the public, private, and academic meteorological community in the U.S.

America's Weather Industry - A term for describing the entire private sector of the meteorology industry in the U.S.

Angular Beam Width - The angle in degrees measured across the axis of the radar beam between half power points.

Anomalous Propagation (AP) - The abnormal bending of the radar beam as it passes through the atmosphere.

Area Forecast Discussion (AFD) - A free-form text product issued by each NWS Warning Forecast Office to explain the current and near future weather-related topics that will impact the upcoming forecasts and warnings that the forecast office will issue.

Attenuation - The reduction in power of a signal due to refraction, scattering, or absorption of energy.

Automated Surface Observing System (ASOS) - The surface weather observing network (supported by the NWS, Federal Aviation Administration, and Department of Defense) designed to support aviation operations and weather forecasts by collecting automated surface observations.

B

Backscattered Signal - The scattering of radiant energy at 180 degrees to the direction of the transmitted wave; scattering from a target back toward the antenna.

Base Data Distribution System (BDDS) - A subcomponent of the WSR-88D system that was added as part of the Open Radar Product Generator system upgrade. The BDDS provides real-time access to base data for NWS partners to provide value added products for their customers.

Base Product - The WSR-88D products that display the three base moments: Reflectivity, Velocity, and Spectrum Width.

Base Reflectivity (Z) - A reflectivity product at a specific elevation which has been obtained directly from the base reflectivity data.

Beam Blockage - The physical obstruction of the radar beam, usually at close range, caused by building, mountains, etc.

Beam Width - The distance between half-power points of the radar beam. Can also be a measure of the concentration of power of a radar beam.

Below Beam Effects - The inaccurate radar measurements caused by incomplete sampling of the atmosphere. For example, evaporation or growth of precipitation below the beam will not be detected.

Bounded Weak Echo Region (BWER) - A core of weak equivalent reflectivity in a thunderstorm which identifies the location of a strong updraft with a mesocyclone.

Bow Echo - A rapidly moving crescent shaped echo which is convex in the direction of motion. Bow echoes are typically associated with strong straight-line winds.

BUFKIT - BUFKIT is a forecast profile visualization and analysis tool kit developed by the staff at the National Weather Service to view model output profiles and forecast parameters at high vertical and temporal resolutions.

Build Training - Training for NWS Forecasters (Meteorologist and Hydrologist) on software and hardware updates to the AWIPS, RPG, RDA, etc.

C

Clutter Suppresion - Clutter suppression is a quality assurance process performed at the WSR-88D RDA to remove ground clutter contamination caused by non-meteorological ground return.

Cognitive Task Analysis (CTA) - A study conducted to capture how experts at a particular task think, what they know, how they organize and structure information, and what they seek to understand better.

Composite Reflectivity (CZ) - A WSR-88D volumetric product which displays the highest reflectivities detected above a given area on the earth's surface.

County Warning Area (CWA) - The region where each Weather Forecast Office is responsible to provide locally generated forecast and warning products. While not always true, the forecast office is generally located towards the center of the CWA.

D

DBZ (dBZ) - A decibel of the equivalent radar reflectivity factor, where:
dBZ = 10*Log(equivalent reflectivity).

Dealiasing - Process of removing undersirable aliases from the velocity field.

Decibel db - A logarithmic expression for the ratio of two quantities, such as the ratio of power transmitted to the power received at the antenna [i.e.,
db = 10*Log(Power Trans/Power Rec)].

Derived Product - The WSR-88D derived products are all the products generated from the three base moments of the base data using meteorological algorithms.

Digital Mesocyclone Detection (DMD) - The Digital Mesocyclone Detection (DMD) product is similar to the MDA, with the key difference being that DMD is a rapid update product that is available after each elevation scan (while the MDA is available only at the end of each volume scan).

Displaced Real-Time (DRT) - A term used to describe the process of setting the system clock backwards on a WES-enabled Linux workstation so that archived data from the Advanced Weather Interactive Processing System can be displayed as when it was originally received.

Display Two Dimensions (D2D) - The visualization software used to display data on AWIPS.

Distance Learning Operations Course (DLOC) - The Distance Learning Operations Course is a blended learning course designed to provide all new NWS Forecasters (Meteorologist and Hydrologist) training on the use of the WSR-88D when making forecast and warning decisions.

Doppler Dilemma - The problem encountered in arriving at a balance between maximum velocity determination and maximum detection range.

Doppler Effect - The observed change in the frequency of sound or electromagnetic waves due to the relative motion of the source and observer.

Downburst - A strong downdraft associated with thunderstorms which induces an outflow of damaging winds on or near the surface.

Ducting - A special condition of superrefraction in which the radar beam becomes trapped within a layer of the atmosphere. A condition of warm, dry air overlying relatively cool, moist air may result in ducting.

E

Echo - Energy backscattered from a target and received by the RDA, displayable in the base and derived products.

Elevation Angle - The angle between the horizon and a point above the horizon.

Emergency Manager (EM) - Individuals who are responsible for the civil response to natural and man-made emergencies in local communities.

F

Facilitators - The facilitator is the person at a local NWS office who provides assistance, support and guidance to students throughout a course. Facilitators are usually the SOO, DOH, Training Officer, or other designate in the office.

Flash Flood Guidance (FFG) - Flash Flood Guidance is a tool used by meteorologists to predict flash flooding of urban areas, creeks and streams.

Flash Flood Monitoring and Prediction (FFMP) - The Flash Flood Monitoring and Prediction (FFMP) system is an integrated suite of multi-sensor applications which detects, analyzes, and monitors precipitation and generates short-term warning guidance for flash flooding automatically within AWIPS.

Frequency - The number of recurrences of a periodic event per unit time. Radar waves have a frequency specified per second.

G

Ground Clutter - Echoes that result from physical obstructions such as buildings, trees, and mountains.

Gust Front - An outflow boundary which consists of winds meeting gust criteria. On the surface, its passage resembles that of a cold front.

H

High-Resolution Precipitation Nowcaster (HPN) - A rainfall nowcasting algorithm that produces regional, gridded, one-hour rainfall nowcasts using input data generated by the High-Resolution Multisensor Precipitation Estimator, which is software that runs at most WFOs as part of the FFMP application.

Hook Echo - A classical radar echo which is often shaped like a figure six. The hook echo is associated with tornadic activity.

Hydrometeorology Technician (HMT) - Staff member(s) at a local National Weather Service office that provide a range of technical support and assistance to shift operations and other basic activities in the office.

I

Ice Jam - A phenomenon where large chunks of ice get caught up on a bridge, or other structure, and block the flow of water through a hydrologic drainage system. Ice Jams during the Spring, or mid-Winter rapid ice melts, can result in significant flooding.

Incident Meteorologist (IMET) - NWS forecaster who is stationed on-site with firefighters and/or emergency management personnel during significant events that require constant contact between NWS meteorologists and the people responsible for mitigating the impacts of the on-going event.

Information Technology Officer (ITO) - The staff member in each NWS Weather Forecast Office who is responsible for maintaing the Advanced Weather Interactive Processing System and other computer equipment necessary for weather operations in the office.

Instructional Component (IC) - An organizational unit for training material in the different tracks of AWOC for which a student must pass an exam to receive credit. Each IC is made up of one or more lessons which cover the objectives for that topic.

ISO File - An archive file, or disk image, that is used by most Windows and Linux software vendors to create file systems on CDs and DVDs. ISO files can be mounted as a file system (just like a disk) and can be easier to distribute than actual disks.

L

Layer Composite Reflectivity Maximum (LRM) - One of the derived radar product that computes the composite reflectivity maximum for three predefined layers of the atmosphere.

Learning Management System (LMS) - A service provided to organizations that require distance education and e-learning delivery, tracking, and evaluation in a cost effective manner.

Line Echo Wave Pattern (LEWP) - A line of radar echoes which has been subjected to an acceleration along one portion of the line. This results in a mesoscale wave pattern in the line.

Local Area Prediction System (LAPS) - An objective anaylsis system that integrates observational data from numerous data platforms into a very high-resolution grid. These grids can then be analyzed by forecasters to determine current conditions or used as input fields for forecast models.

Local Storm Reports (LSR) - Text products issued by NWS weather forecasters containing information on reports of severe weather that have occurred in their local area. These reports may be phoned in to the office, submitted on-line, reported by HAM radio operators, or shown on TV.

M

Maximum Unambiguous Range - The maximum range to which a transmitted pulse of radar energy can travel and return to the radar before the next pulse is transmitted

Melting Level - The level where frozen precipitation particles melt into water during their decent to the surface. The melting level usually appears about 1,000 ft. above the bright band on radar displays.

Mesocyclone - A three-dimensional region in a storm that rotates cyclonically, meets a series of criteria related to its intensity and temporal consistancy, and is closely correlated with severe weather.

Mesocyclone Detection Algorithm (MDA) - The Mesocyclone Detection Algorithm (MDA) was developed by NSSL to develop a more robust algorithm than the Mesocyclone algorithm that was deployed with the WSR-88D.

Mesoscale Convective System (MCS) - A long-lived line of thunderstorms that often results in strong, if not damaging, winds occurring over a large area for several hours. Hail, flash flooding, and even tornadoes are also sometimes reported within a MCS.

Meteorologist-In-Charge (MIC) - The person in charge of all management responsibilities at each local Weather Forecast Office.

Microburst - A damaging wind event that results from a downburst and is often less than 2 sq. miles in extent.

N

National Digital Forecast Database (NDFD) - The primary database used by the NWS for its customers to display, analyze, and compare digital forecast products for the entire U.S.

National Oceanic and Atmospheric Administration (NOAA) - The NOAA is the parent organization of the National Weather Service.

National Weather Service (NWS) - The NWS is the federal agency responsible for issuing weather, hydrological, and climate forecasts and warnings for the U.S. to protect the life and property of its citizens and to enhance the national economy.

NWS Learning Center - The NWS Learning Center is the Learning Management System implemented throughout NWS, NOAA, and Department of Commerce.

Nyquist Velocity - The velocity value up to which Doppler radar can detect inbound and outbound velocities unambiguously.

O

Open Radar Data Acquisition (ORDA) - A software and hardware update to the Radar Data Acquisition unit using open source technology and replacing equipment that was deployed when the WSR-88D was originally fielded.

Open Radar Product Generator (ORPG) - A software and hardware update to the Radar Product Generator that used open source technology and replaced equipment that was deployed when the WSR-88D was originally fielded.

Operational Build (OB) - "OB" refers to specific versions of AWIPS. After AWIPS was fielded, the developers switched to a more open source architecture to the system. As a result, the release versions were renamed "Build" to "Operational Build" to highlight the change.

Operations Training Branch (OTB) - The previous name of the Warning Decision Training Branch when it was part of the Operational Support Facility (now the Radar Operations Center).

Outflow Boundaries - The leading edge of horizontal air flow resulting from cooler, denser air sinking and spreading out at the surface. Outflow boundaries often are cased by the downdraft of thunderstorms.

P

Partial Beam Filling - The effect that occurs when a target fills only a small portion of the radar beam.

Post-Mortem - A detailed examination or evaluation of a significant event from which some lessons may be learned to improve future performance. In AWOC, post-mortems most often refer to meteorological events.

Probability of Precipitation (POP) - A forecast product that indicates the certainty with which weather forecasters think a measurable (.01" or more) precipitation event will occur at any given point during a defined forecast period.

Professional Competency Units (PCU) - Subcomponents of the Professional Development Series where knowledge and performance standards are determined and training is developed to ensure that forecasters are capable of performing their jobs in a proficient manner.

Professional Development Series (PDS) - An organizational structure for training in the National Weather Service where the subject is divided into a series of professional competency units (PCUs) with specific courses and/or modules are developed.

Pulse - A single short duration transmission of electromagnetic energy.

Pulse Pair Processing - A method of determining the Doppler shift by comparing the returned frequency shift of consecutive pulses.

Pulse Repetition Frequency (PRF) - The rate at which the pulses of electromagnetic energy are transmitted by the radar; the number of pulses per second.

Pulse Storms - A particular classification of convective storms that are typically short-lived, lack well-defined storm structure, and can produce damaging winds near the ground as the storms collapse and dissipate.

Pulse-Storm Downburst Prediction (PSDP) - A series of workshops organized by the Warning Decision Training Branch in the mid-to-late 1990s to discuss research on the science and forecast techniques related to dry and wet microbursts events through the U.S.

Q

Quantitative Precipitation Estimate (QPE) - An estimate of the total precipitation that fallen during a specified period of time. QPE values are usually calculated from reflectivity (or related) products from the nearest available radar.

Quantitative Precipitation Forecast (QPF) - A prediction for the total precipitation expected to fall during the specified forecast period.

Quasi-Linear Convective System (QLCS) - A multicellular thunderstorm complex that, generally, has a linear appearance (i.e., MCS, squall line) but also exhibits localized storm-scale vorticies that can behave very similar to low-level mesocyclones and are capable of producing tornadoes.

R

Radar - An acronym for Radio Detection and Ranging; it's also an electronic instrument used to detect atmospheric scatters such as precipitation.

Radar Data Acquisition (RDA) - The RDA is the component of the WSR-88D system that includes the radar transmitter, antenna, receiver, and associated hardware that produced the base data sent to the RPG for processing.

Radar Operations Center (ROC) - The agency (funded by the National Weather Service, Department of Defense, and Federal Aviation Administration) that provides meteorological, software, maintenance, and engineering support for all WSR-88D systems.

Radar Product Generator (RPG) - The RPG, which is a component of the WSR-88D, is a multi-function unit that ingests base data, processes that data, and produces products for viewing by users.

Radial Velocity (V) - The component of velocity parallel to the radar beam.

Range Folding (RF) - The display of multiple trip return which differs from the actual location of the target. A multiple trip return appears at the difference of the true range and a multiple of the unambiguous range.

Range Resolution - The ability of the radar to distinguish between two targets at different ranges from the radar, but at the same azimuth.

Rankine Vortex - Velocity profile for a symmetric circulation in which the inner core is in solid body rotation.

Refraction - The process in which the direction of energy propagation is changed as the result of a change in density. Large changes is the refractive index of the atmosphere can cause subrefraction and superrefraction.

S

Satellite Broadcast Network (SBN) - The data nework that the Advanced Weather Interactive Processing System uses to transfer data from the Network Control Facility to each Weather Forecast Office (or other location that owns an AWIPS).

Scanning Strategy - A programmed combination of antenna motions and switched PRFs. A Volume Coverage Pattern for the WSR-88D is an example of a scanning strategy.

Science and Operations Officer (SOO) - A member of the management team in each Weather Forecast Office, the SOO is responsible for the local training and research efforts in their office. The SOO is a key partner (and local facilitator) in WDTB's training efforts in each local office.

Second-Trip Echo - A radar echo received from a target beyond the normal maximum range of detection.

Severe Weather Statement (SVS) - A product issued by NWS weather forecasters to provide follow-up information on a previously issued severe weather warning (tornado or severe thunderstorm). The SVS product can be used to continue, cancel, correct, or expire a warning.

Short Term Forecast (NOW) - A text-based product issued by NWS forecasters to alert NWS partners and the general public of significant weather conditions that are forecast to occur in the next several hours.

Side Lobes - Concentrated elements of focused power outside the main radar beam. Backscatter from side lobes can be displayed as if it were in the main beam. Ground clutter is a common result from side lobes.

Signal-to-Noise Ratio (SNR) - A ration of the intensity of the minimum signal capable of being detected to the amount of interference generated by the radar.

Situation Awareness (SA) - The process of acquiring the perception of the elements in the environment within a volume space, the comprehension of their meaning, and the projection of their status in the near future.

Spectrum Width (SW) - A measure of dispersion of velocities within the radar sample volume, it can also be defined as the standard deviation of the velocity spectrum.

Storm Total Precipitation Product (STP) - A product generated by the WSR-88D Radar Product Generator that specifies the quantitative precipitation estimate for all areas within 124 nm of the radar data acquisition unit location.

Subject Matter Experts (SME) - Subject Matter Experts are those who provide expertise in the content of an instructional area. SMEs can either contribute to or develop the training.

Subrefraction - Atmospheric conditions which cause a straightening of the radar beam upward.

Supercell Thunderstorm - A classification of thunderstorm that is often associated with severe and tornadic thunderstorms. Supercells have strong, rotating thunderstorm updrafts, among other storm features, that allow them to last longer than most common thunderstorms.

Superrefraction - Bending of the radar beam in the vertical which is greater than under standard refractive conditions. This causes the beam to be lower than indicated, and often results in extensive ground return as well as an overestimation of cloud top heights.

System for Convection Analysis and Nowcasting (SCAN) - An integrated suite of multisensor applications which detects, analyzes, and monitors convection and generates short-term probabilistic forecast and warning guidance for severe weather automatically within AWIPS.

T

Teletraining - A delivery method of distance education where the instructor and students are in different locations, viewing training visuals on monitors (or projectors) and utilizing teleconferencing technology for audio communication.

Terminal Doppler Weather Radar (TDWR) - The Terminal Doppler Weather Radar (TDWR) is a dedicated meteorological surveillance radar deployed by the FAA near many of the larger airports in the U.S.

Three-Body Scatter Spike (TBSS) - An area of enhanced reflectivity that is often seen down the radar beam radial from an area of significant hail. In addition to enhanced reflectivity, TBSSs often have near-zero radial velocities and high spectrum width values.

Thunderstorm Downdraft - The region of a thunderstorm where air descends towards the surface. Downdrafts can occur in a thunderstorm because the air in that region is relatively stable or because the wind fields in the thunderstorm force air towards the surface.

Thunderstorm Updraft - The portion of a thunderstorm where relatively unstable air flows into the storm and rises. A stronger, or faster, a thunderstorm updraft usually results in stronger, more intense severe weather associated with that thunderstorm.

Tornadic Vortex Signature (TVS) - The radar "signature" of a vortex indicative of a tornado or tornadic circulation. The WSR-88D employs an algorithm that uses the base moment data to detect these circulations.

Tornado Warning Guidance (TWG) - A series of joint research products between WDTB and the National Severe Storms Laboratory (NSSL) to determine potential relationships between radar signatures and environmental data that might improve lead time in tornado warnings issued by the NWS.

Turbulence - Irregular, random fluctuations in the wind velocity field in the horizontal and vertical planes.

U

Unambiguous Range - The range to which a transmitted pulse wave can travel and return to the radar before the next pulse is transmitted.

Unit Control Position (UCP) - Prior to the WSR-88D upgrade to an "open systems" infrastructure, the UCP was the component of the WSR-88D system that ingested base data, processed that data, and produced products for viewing by users.

V

Valid Time Event Code (VTEC) - The short line of text at the beginning of each watch/warning/advisory product issued by the NWS. VTEC allows NWS partners to quickly access critical information (e.g., product type, start & stop time) and relay it to customers in a timely fashion.

Velocity Aliasing - This occurs as a result of an incorrect value(s) for radial velocities when the actual velocity exceeds the Nyquist velocity.

Velocity Couplet - Adjacent maxima of radial velocities of opposite sign that indicate the presence of rotation or divergence in Doppler radial velocities.

Vertically Integrated Liquid (VIL) - The algorithm that estimates the total amount of liquid suspended in a vertical column of the atmosphere.

Virga - This phenomenon is precipitation that falls from a cloud but evaporates before reaching the earth's surface.

VISITView - An application used for NWS teletraining development and delivery.

Volume Coverage Pattern (VCP) - The particular scanning strategy employed by the WSR-88D to best sample the atmosphere based on the current conditions.

W

WarnGen - An application that is part of the Advanced Weather Interactive Processing System that allows forecasters to create and issue short-fuse (severe thunderstorm, tornado, and flash flood)warnings and follow-ups statements.

Warning Coordination Meteorologist (WCM) - The staff member at a local Weather Forecast Office who is responsible for the severe weather warning program and public outreach activities for that area.

Warning Decision Making (WDM) - Warning Decision Making refers to the process of how a forecaster makes the decision to issue (or not issue) a warning on a particular storm, as well as mentally processing all of the data inputs that go into making that decision.

Weather Event Simulator (WES) - The Weather Event Simulator is an application that provides case playback and simulation capabilities from archived AWIPS data. The WES is effectively a data pump and a training interface for AWIPS.

Weather Event Simulator Scripting Language (WESSL) - WESSL is an application that utilizes scripts written to enhance the capabilities of WES by adding interaction, maps, and other non-AWIPS visuals and text to the simulation experience.

Weather Forecast Office (WFO) - The local offices in the National Weather Service that issue weather, hydrologic, and climate forecasts and warnings to meet the agency's mission.

Weather Surveillance Radar - 88 Doppler (WSR-88D) - The dedicated meteorological surveillance radar deployed by the NWS that significantly improved the quality of reflectivity data available and added the capability of Doppler velocity and spectral width data.


A|B|C|D|E|F|G|H|I|L|M|N|O|P|Q|R|S|T|U|V|W

WDTB Home!

Department of Commerce
National Oceanic & Atmospheric Administration
National Weather Service
Office of Climate, Water, and Weather Services
Web site owner:
Warning Decision Training Branch
120 David L. Boren Blvd.
Norman, OK 73072
Page Author: WDTB Webmaster
Page last modified: September 25, 2013 9:02

Disclaimer
Credits
Glossary
FOIA
Privacy Policy
Information Quality

About NWS
Career Opportunities
Strategic Plan
NWS Mission Statement