There are often unfamiliar terms and acronyms that are used if you are involved in FEMA appeals or a floodplain management situation. The glossary here may be helpful as you proceed.


FEMA acronym for Assistant Associate Director for Public and Intergovernmental Affairs


Advisory Council on Historic Preservation


Americans with Disabilities Act


FEMA’s Automated Disaster Assistance Management System

Advanced Weather Interactive Processing System (AWIPS)

The computerized system that processes NEXRAD and ASOS data received at National Weather Service Forecast Offices


A message from the National Hurricane Center in Miami giving warning information with details on tropical cyclone location, intensity and movement, and precautions that should be taken. The advisory will contain a summary of all warnings in effect.


Aeromedical Evacuation


Agency Emergency Coordinators


Aeromedical Evacuation Control Element

Aerial Reconnaissance Weather Officer (ARWO)

The flight meteorologist for weather reconnaissance flights into a tropical cyclone


Aeromedical Evacuation System


Automation of Field Operations and Services


Airlift Control Center


Air Mobility Command, U.S. Air Force


Aerial Measuring System


An instrument that measures the speed or force of the wind


American National Red Cross


Army Operations Center, Pentagon


Area of Potential Effect

Applicant (for FEMA Grants)

The state agency, local government or eligible private nonprofit organization which submits a request for assistance to the State; the State is the Grantee of all federal grants for public assistance and administers subgrants made to applicants.

Applicant Liaison (Liaison)

A State government customer representative responsible for providing applicants with state-specific information and documentation requirements. The Liaison works closely with the Public Assistance Coordinator to provide any assistance the applicant may require.


American Red Cross


Amateur Radio Emergency Services


American Radio Relay League


Agricultural Research Service


Aerial Reconnaissance Weather Office


American Society of Civil Engineers


Assistant Secretary of Defense


Association of State Dam Safety Officials


Automated Surface Observing Systems

Atmospheric Pressure

The pressure exerted by the atmosphere at a given point. Its measurement can be expressed in several ways, such as in millibars and in inches or millimeters of mercury (Hg). Also known as barometric pressure.


Automatic Digital Network

Automated Surface Observing Systems (ASOS) — weather service

A collection of automated weather instruments that collect data. They perform surface-based observations from places that do not have a human observer, or that do not have an observer 24 hours a day.

Automation of Field Operations and Services (AFOS) — weather service

The computer system that links National Weather Service offices together for weather data transmission


Automatic Voice Network


Advanced Weather Interactive Processing System


An instrument for determining the pressure of the atmosphere

Best Track

A subjectively smoothed path, versus a precise and very erratic fix-to-fix path, used to represent tropical cyclone movement. It is based on an assessment of all available data.


Base Flood Elevation


Bureau of Indian Affairs


Boise Interagency Fire Center


Bureau of Land Management


Best Management Practices


Bureau of Reclamation


Blanket Purchase Agreement


An opening through the dam resulting in partial or total failure of the dam


Construction and Demolition


Clean Air Act

Cape Verde Islands

A group of volcanic islands in the eastern Atlantic Ocean off the coast of West Africa. A “Cape Verde hurricane” originates in this area.


Capability Assessment for Readiness


Chief, Aerial Reconnaissance Coordination, All Hurricanes. The 53rd Weather Reconnaissance Squadron’s Air Force Reserve civilians who bridge the gap between the Hurricane Specialists at NHC and the flying squadron. Each day, they publish the Tropical Cyclone Plan of the Day.

Case Management

A systems approach to provision of equitable and fast service to applicants for disaster assistance. Organized around the needs of the applicant, the system consists of a single point of coordination, a team of on-site specialists, and a centralized, automated filing system.

Case Management File

A centralized data bank of all applicant activities. Data entered into this bank creates a chronological history of everything that has taken place with an applicant from the time they apply for assistance until they have received all monies and their file has been closed.


Crisis Action Team


Categorical Exclusion


Chemical, Biological Incident Response Force


Coastal Barrier Resources Act


Chemical, Biological, Radiological, Nuclear or High-Yield Explosive


Coastal Barrier Resources System


Crisis Counseling


Commodity Credit Corporation


Consultation Coordination Officer


Casualty Collection Point


Community Development Block Grant


Centers for Disease Control, U.S. Public Health Service


Catastrophic Disaster Response Group

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The vertical axis or core of a tropical cyclone. It is usually determined by cloud vorticity patterns, wind and/or pressure distributions.

Center/Vortex Fix

The location of the center of a tropical or subtropical cyclone obtained by reconnaissance aircraft penetration, satellite, radar, or synoptic data

Central North Pacific Basin

The region north of the Equator between 140W and the International Dateline. The Central Pacific Hurricane Center (CPHC) in Honolulu, Hawaii is responsible for tracking tropical cyclones in this region.


Council of Environmental Quality


Comprehensive Environmental Resource Compensation and Liability Act


Code of Federal Regulations


Central Intelligence Agency


Critical Infrastructure Assurance Office




Critical Infrastructure Protection


Chairman of the Joint Chiefs of Staff


Conditional Letter of Map Amendment


Conditional Letter of Map Revision


Conditional Letter of Map Revision Based on Fill

Closest Point of Approach

Point where hurricane eye makes closest contact to shore without actually making landfall


Consequence Management


Consequence Management Advisory Team


Crisis Management Team

Coastal Flood Warning

A warning that significant wind-forced flooding is expected along low-lying coastal areas if weather patterns develop as forecast

Coastal Flood Watch

An announcement that significant wind-forced flooding is expected along low-lying coastal areas if weather patterns develop as forecast


Continuity of Government

Cold Front

The leading edge of an advancing cold air mass that is underrunning and displacing the warmer air in its path. Generally, with the passage of a cold front, the temperature and humidity decrease, the pressure rises, and the wind shifts (usually from the southwest to the northwest in the Northern Hemisphere). Precipitation is generally at and/or behind the front, and with a fast-moving system, a squall line may develop ahead of the front. See occluded front and warm front.

Comprehensive EAP Exercise

An in-depth exercise of an EAP that involves the interaction of the dam owner with the state and local emergency management agencies in a stressful environment with time constraints. Functional and full-scale EAP exercises are considered comprehensive EAP exercises.


Concept of Operations Plan


Potential loss of life or property damage downstream of a dam caused by floodwaters released at the dam or by waters released by partial or complete failure of the dam. Includes effects of landslides upstream of the dam on property located around the reservoir.


Continental United States


Continental United States Army


Atmospheric motions in the vertical direction resulting from surface heating and the subsequent rising of warm air. This lifting mechanism is capable of generating the rising motions necessary for clouds and precipitation to form.


Wind movement that results in a horizontal net inflow of air into a particular region. Convergent winds at lower levels are associated with upward motion. Contrast with divergence.


Continuity of Operations

Cost Estimating Format (CEF)

A forward pricing methodology for estimating the total cost of repair for large permanent projects, by use of construction industry standards. The format uses a base cost estimate and design and construction contingency factors, applied as a percentage of the base cost.


Community Rating System


Customer Service


Chemical Stockpile Emergency Preparedness Program


Combined Travel Authorization


Clean Water Act


Checkwriter System


An atmospheric circulation (low-pressure system) with rotating and converging winds, in which the center has a relative pressure minimum. It usually has a diameter of 2000 to 3000 kilometers. When developing, a cyclone typically consists of a warm front pushing northward and a cold front pushing southward with the center of low pressure (cyclone center) located at the junction of the two fronts. Cyclones in the Northern Hemisphere rotate counter-clockwise while Southern Hemisphere cyclones rotate clockwise.


Disaster Application Center


Disaster Assistance Employee

Dam Failure

Catastrophic type of failure characterized by the sudden, rapid and uncontrolled release of impounded water. It is recognized that there are lesser degrees of failure and that any malfunction or abnormality outside the design assumptions and parameters which adversely affect a dam’s primary function of impounding water is properly considered a failure. Such lesser degrees of failure can progressively lead to or heighten the risk of a catastrophic failure. They are, however, normally amendable to corrective action.


Disaster Assistance Management Accountability System


Domestic Strategy and Support Directorate

Data Buoys

Buoys placed throughout the Gulf of Mexico and along the Atlantic and Pacific coasts of the United States that relay information on air and water temperature, wind speed, air pressure and wave conditions via radio signals


Defense Coordinating Element


Defense Coordinating Officer


Deputy Disaster Recovery Manager


The act based on the President’s decision that a major disaster qualifies for federal assistance under the Stafford Act


Describes a decrease in the central pressure of a low-pressure system or an area of cyclonic circulation. Although it usually describes the action of a pressure system on a constant pressure chart, it also means a surface low is increasing in cyclonic circulation and acquiring more energy. It is the opposite of filling.


In meteorology, another name for an area of low pressure, a low or trough. It also applies to a stage of tropical cyclone development and is known as a tropical depression to distinguish it from other synoptic features.


Domestic Emergency Support Team


Deputy Federal Coordinating Officer


Disaster Field Office


Department of Homeland Security


Department of Homeland Security, Border and Transportation Security Directorate


Department of Homeland Security, Emergency Preparedness and Response Directorate


Department of Homeland Security, Information Analysis and Infrastructure Protection Directorate


Defense Intelligence Agency


Disaster Information System Clearinghouse


Can apply to a low or cyclone that is small in size and influence. It can also apply to an area that is exhibiting signs of cyclonic development, or to a stage of tropical cyclone development, known as a tropical disturbance to distinguish it from other synoptic features.


Disaster Medical Assistance Team


Disaster Mortuary Response Team, National Disaster Medical System


Debris Management Task Force


Department of Commerce


Department of Defense


Department of Defense Directive


Department of Defense Instruction


Department of Energy


Department of the Interior


Department of Justice


Department of Labor


Directorate of Military Support, Department of Defense

Doppler Radar

Weather radar that measures direction and speed of a moving object, such as drops of precipitation, by determining whether atmospheric motion is horizontally toward or away from the radar. Using the Doppler effect, it measures the velocity of particles.


Department of State


Department of Transportation


Defense Production Act of 1950


Defense Priorities and Allocation System


Department of Public Works


Disaster Recovery Center


Deputy Regional Director


Disaster Relief Fund


Disaster Recovery Manager


Dam Safety Program Management Tools


Dam Safety Program Performance Measures


Damage Survey Report


Defense Threat Reduction Agency


Disaster Welfare Inquiry


Environmental Assessment


Executive Associate Director, Response and Recovery Directorate (FEMA)


Emergency Action Plan

EAP Exercise

An activity designed to promote emergency preparedness; test or evaluate EAPs, procedures, or facilities; train personnel in emergency management duties; and demonstrate operational capability. Exercises consist of the performance of duties, tasks, or operations very similar to the way they would be performed in a real emergency. However, the exercise performance is in response to a simulated event.


Emergency Alert System

Easterly Wave

An inverted, migratory wave-like disturbance or trough in the tropical region that moves from east to west, generally creating only a shift in winds and rain. The low-level convergence and associated convective weather occur on the eastern side of the wave axis. Normally, it moves slower than the atmospheric current in which it is embedded and is considered a weak trough of low pressure. It is often associated with possible tropical cyclone development and is also known as a tropical wave.

Eastern North Pacific Basin

The region north of the Equator east of 140W. The National Hurricane Center in Miami, Florida, is responsible for tracking tropical cyclones in this region.


Emergency Broadcast System


Emergency Coordinator


Emergency Communications Staff


Essential Elements of Information


Emergency Education Network


Emergency Information and Coordination Center (FEMA)


Emergency Information and Media Affairs


Environmental Impact Statement


Environmental Justice

El Nino

A warming of the Pacific Ocean currents along the coasts of Peru and Ecuador near the Equator that is generally associated with dramatic changes or shifts in the weather patterns of the region. A major El Nino event generally occurs every 3 to 7 years and is associated with changes in the weather patterns worldwide, including hurricanes.


Environmental Liaison Officer


Emergency Management


Emergency Management Assistance Compact


Any occasion or instance for which, in the determination of the President, Federal Assistance is needed to supplement state and local efforts and capabilities to save lives and to protect property and public health and safety, or to lessen or avert the threat of a catastrophe in any part of the United States.

Emergency Broadcast System

A federally established network of commercial radio stations that voluntarily provide official emergency instructions or directions to the public during an emergency.

Emergency Alert System (EAS)

A system designed to permit government officials to issue up-to-date and continuous emergency information and instructions to the public in case of a threatened or actual emergency. It is replacing the Emergency Broadcast System.

Emergency Management Agency

The state and local agencies responsible for emergency operations, planning, mitigation, preparedness, response and recovery for all hazards. Names of emergency management agencies include: Division of Emergency Management, Comprehensive Emergency Management, Disaster Emergency Services, Civil Defense Agency, Emergency and Disaster Services.

Emergency Operations Center (EOC)

The location or facility where responsible officials gather during an emergency to direct and coordinate emergency operations, to communicate with other jurisdictions and with field emergency forces, and to formulate protective action decisions and recommendations during an emergency.

Emergency Public Information

Information disseminated primarily, but not unconditionally, at the time of an emergency including actions, instructions and direct orders.

Emergency Public Shelter

Generally a public school or other such structure designated by county or city officials as a place of refuge. A volunteer group such as the American Red Cross or Salvation Army usually manages a shelter.

Emergency Work

Work which must be done immediately to save lives and to protect improved property, public health and safety, or to avert or lessen the threat of a major disaster. Emergency work frequently includes clearance and removal of debris and temporary restoration of essential public facilities and services.


Emergency Management Institute


Emergency Management Planning and Assistance


Emergency Management Performance Grant


Emergency Medical Services


Emergency Manager’s Weather Information Center


Executive Order


Emergency Operations Center


Emergency Operations Plan


Environmental Protection Agencies


Emergency Planning and Community Right-to-Know Act


Emergency Public Information and Communications Advisory Committee


Emergency Preparedness Liaison Officer


Electric Power Research Institute


The geographic circle at 0 degrees latitude on the earth’s surface. It is an equal distance from the North and South Poles and divides the Northern Hemisphere from the Southern.


Emergency Relief (FHWA Assistance Program)


Economic Resources Board


Elevation Reference Mark


Emergency Response Team


Advance Element of the Emergency Response Team (FEMA)


Endangered Species Act


Engineering Study Data Package


Emergency Support Function


Emergency Support Team (FEMA)

Evacuation Time

The lead-time that a populated coastal area must have to safely relocate all residents of vulnerable areas from an approaching hurricane. This time can also be perceived as the necessary amount of time between the local official evacuation order and the arrival of sustained gale force winds (40 mph) and/or flooding.

Explosive Deepening

A 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

Extent of Evacuation

The identification of vulnerable people who must evacuate based on estimated damage and/or homes susceptible to hurricane force winds


A term used in advisories and tropical summaries to indicate that a cyclone has lost its tropical characteristics. The term implies both poleward displacement of the cyclone and the conversion of the cyclone’s primary energy source from the release of latent heat of condensation to baroclinic (the temperature contrast between warm and cold air masses) processes. It is important to note that cyclones can become extratropical and still retain winds of hurricane or tropical storm force.

Extratropical Cyclone

A 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 hundreds of kilometers. These cyclones form outside the tropics, the center of storm is colder than the surrounding air, and have fronts and the strongest winds in the upper atmosphere.


The center of a tropical storm or hurricane characterized by a roughly circular area of light winds and rain-free skies and the lowest pressure. An eye will usually develop when the maximum sustained wind speeds exceed 78 mph. It can range in size from as small as 5 miles to up to 60 miles (20-50 km) but the average size is 20 miles. In general, when the eye begins to shrink in size, the storm is intensifying.

Eye Wall

An organized band of convection surrounding the eye, or center, of a tropical cyclone. It contains cumulonimbus clouds, severest thunderstorms, heaviest precipitation and strongest winds.


Federal Aviation Administration


Any publicly or privately owned building, works, system or equipment, built or manufactured, or an improved and maintained natural feature. Land used for agricultural purposes is not a “facility.”


Financial Accounting and Reporting System


Field Assessment Team




Flood Boundary and Floodway Map


Federal Bureau of Investigation


Federal Communications Commission


Federal Communications Manager


Federal Coordinating Officer


Food and Drug Administration


Flood Disaster Protection Act


Floodway Data Table

Feeder Bands

In tropical parlance, the lines or bands of thunderstorms that spiral into and around the center of a tropical system. Also known as outer convective bands, a typical hurricane may have three or more of these bands. They occur in advance of the main rain shield and are usually 40 to 80 miles apart. In thunderstorm development, they are the lines or bands of low-level clouds that move or feed into the updraft region of a thunderstorm.


Federal Emergency Management Agency


Federal Energy Regulatory Commission


Federal Emergency Support Coordinator


Final Flood Elevation Determination


Flood Hazard Boundary Map


Federal Highway Administration


Federal Insurance Administration


Used in describing the history of a low-pressure system or an area of cyclonic circulation, it means an increase in the central pressure of the system. Although it usually describes the action of a pressure system on a constant pressure chart, it also means a surface low is decreasing in cyclonic circulation and losing its characteristics. The opposite of deepening.


Federal Insurance and Mitigation Administration


Flood Insurance Rate Map


Flood Insurance Study


Foreign Intelligence Surveillance Act

Flood Hydrograph

A graph showing, for a given point on a stream, the discharge, height or other characteristic of a flood with respect to time.

Flood Plain

Any land area susceptible to being inundated by water from any source. Normally the regulatory flood plain is characterized by the designation “100-year,” meaning there is a 1% chance of flooding per year. The flood plain is often referred to as flood prone areas.

Flood Routing

A process of determining progressively over time the amplitude of a flood wave as it moves past a dam or downstream to successive points along a river or stream.

Flood Stage

The level of a river or stream where overflow onto surrounding areas can occur

Flood Warning

The expected severity of flooding (minor, moderate or major) as well as where and when the flooding will begin


A general and temporary condition of partial or complete inundation of normally dry land areas from the overflow of inland or tidal water, or rapid accumulation or runoff of surface waters from any source


Flood Mitigation Assistance


Food and Nutrition Services


FEMA Operations Center


Freedom of Information Act


Finding of No Significant Impact

Force Account

An applicant’s own labor forces and equipment


A statement of expected future occurrences. Weather forecasting includes the use of objective models based on certain atmospheric parameters, along with the skill and experience of a meteorologist. Also called a prediction.

Forward Speed

The rate of movement (propagation) of the hurricane eye in miles per hour or knots


Federal Radiological Emergency Response Plan


The boundary between two dissimilar air masses


Federal Response Plan


Forest Service


FEMA Switch Network


Federal Supply Service


Federal Tort Claims Act


Full-Time Equivalent


Federal Telecommunications Equipment

Fujiwhara Effect

A binary interaction where tropical cyclones within a certain distance (300-750 nautical miles depending on the sizes of the cyclones) of each other begin to rotate about a common midpoint


Federal Water Pollution Control Act


U.S. Fish and Wildlife Service


Fiscal Year

Gale Warning

A warning of 1-minute sustained surface winds in the range 39 to 54 mph (34 to 47 knots) inclusive, either predicted or occurring not directly associated with tropical cyclones


Governor’s Authorized Representative


FEMA’s Office of General Counsel

Geostationary Operational Environmental Satellites (GOES)

Family of NWS weather satellites, which orbit 22,300 miles above the earth and maintain a velocity that allow them to remain over a fixed place above the equator. Images are available to forecasters every 30 minutes.


Geographic Information System


Global Positioning System

Greenwich Mean Time (GMT)

The name of the twenty-four hour time scale that is used throughout the scientific and military communities. Standard Time begins at Greenwich, England, which is the Prime Meridian of Longitude. The globe is divided into twenty-four (24) time zones of 15 degrees of arc, or one hour in time apart. To the east of this meridian, time zones are numbered 1 to 12 and prefixed with a minus (-), while to the west, the time zones are also numbered 1 through 12 but prefixed with a plus (+). Other names for this time measurement are Universal Time Coordinate (UTC) and Zulu (Z).


General Services Administration


Hydraulics and Hydrology

Hazard Mitigation

Any cost-effective measure that will reduce the potential for damage to a facility from a disaster event

Hazard Potential

A situation which creates the potential for adverse consequences such as loss of life, property damage or other adverse impacts. Impacts may be for a defined area downstream of a dam from flood-waters released through spillways and outlet works of the dam, or waters released by partial or complete failure of the dam. They may also be for an area upstream of the dam from effects of backwater flooding or effects of landslides around the reservoir perimeter.


Hazardous materials


Hazards United States


The water immediately upstream from a dam. The water surface elevation varies due to fluctuations in inflow and the amount of water passed through the dam.


Hurricane Evacuation Study


High Frequency


Health and Human Resources


Department of Health and Human Services


Household hazardous waste

High Wind Advisory

Announcement issued by the National Weather Service for sustained winds exceeding 25 mph (19 knots)

High Wind Watch/Warning

Issued by the National Weather Service when either of the following occurs or is expected to occur in the near term: 1) Sustained surface winds (1-minute average) of 40 mph (35 knots) or greater, lasting for 1 hour or longer; or 2) Sustained winds or gusts of 58 mph (50 knots) or greater for any duration.

High-Pressure System

An area of relative pressure that has diverging winds and a rotation opposite to the earth’s rotation. This is clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. Also known as an anticyclone, it is the opposite of an area of low pressure or a cyclone.


Health Insurance Portability and Accountability Act of 1996


Hazard mitigation


Hazard Mitigation Grant Program


Hazardous Materials Response Unit




Homeland Security Advisory System


Homeland Security Council


Homeland Security Presidential Directive


U.S. Department of Housing and Urban Development


The amount of water vapor in the air


A tropical cyclone in the Northern Hemisphere with sustained winds of 74 mph (64 knots) or greater in the North Atlantic Ocean, Caribbean Sea or Gulf of Mexico. These winds blow in a large spiral around a relatively calm center of extremely low pressure known as the eye. Around the rim of the eye, winds may gust to more than 200 miles per hour. The entire storm, which can be up to 340 miles (550 kilometers) in diameter, and dominates the lower atmosphere and ocean surface over tens of thousands of square miles. Hurricanes draw their energy from the warm surface water of the tropics (usually above 27 Celsius) and latent heat of condensation, which explains why hurricanes dissipate rapidly once they move over cold water or large land masses.

Hurricane Advisory

Notice, issued by the National Hurricane Center and numbered consecutively for each storm, describing the present and forecasted position and intensity of a hurricane. Advisories are issued at six-hour intervals at midnight, 6 am, noon and 6 pm, Eastern Daylight Time. Bulletins provide additional information. Each message gives the name, eye position, intensity and forecast movement of the storm.

Hurricane Clips

A structural bracing device used on the installation of roofs which reinforce the joints of a house and give a stronger connection to wood-to-wood roofing trusses than just nails. In many coastal communities, hurricane clips are enforced as a code restriction for new homes.

Hurricane Eye

The relatively calm area near the center of the storm. In this area, winds are light and the sky is often partly covered by clouds.

Hurricane Eye Landfall

When the eye, or physical center of the hurricane, reaches the coastline from the hurricane’s approach over water.

Hurricane Hunters

The 53rd Weather Reconnaissance Squadron of the U.S. Air Force Reserve, based out of Keesler Air Force Base in Biloxi, Mississippi. As a part of the 403rd Air Wing, the crew flies Lockheed WC-130 aircraft into tropical storms and hurricanes to gather meteorological data for the National Hurricane Center.

Hurricane Liaison Team

A team of FEMA, NWS, state and local emergency management officials which respond to the National Hurricane Center prior to the landfall of a hurricane in the Atlantic Ocean, Caribbean Sea or Gulf of Mexico. The primary purpose of the team is to assist in coordinating the latest advisories from the NHC to the federal, state and local emergency management agencies.

Hurricane Local Statement

A public release prepared by local National Weather Service Field Offices in or near a threatened area, giving specific details for its county/parish warning area on: 1) weather conditions; 2) evacuation decisions made by local officials; and 3) other precautions necessary to protect life and property.

Hurricane Path or Track

Line of movement (propagation) of the eye through an area

Hurricane Season

The portion of the year having a relatively high incidence of hurricanes. The hurricane season in the Atlantic, Caribbean and Gulf of Mexico runs from June 1 to November 30. The hurricane season in the Eastern Pacific basin runs from May 15 to November 30. The hurricane season in the Central Pacific basin runs from June 1 to November 30.

Hurricane Warning

A warning added to a hurricane advisory that sustained winds of 74 mph (64 knots) or higher associated with a hurricane are expected in a specified coastal area within 24 hours or less. A hurricane warning can remain in effect when dangerously high water or a combination of dangerously high water and exceptionally high waves continue, even though winds may be less than hurricane force. A warning is used to inform the public and marine interests of the storm’s location, intensity and movement. The NHC chooses a distance of approximately 300 miles.

Hurricane Watch

An announcement added to a hurricane advisory that hurricane conditions pose a possible threat to a specified coastal area within 36 hours. A watch is used to inform the public and marine interests of the storm’s location, intensity and movement.

Hurricane/Tropical Storm Probabilities

Issued to allow citizens to realistically assess the threat of a hurricane or tropical storm hitting their community. The probabilities are defined as the chance in percent that the center of the storm will pass within approximately 65 miles of 44 selected locations from Brownsville, Texas, to Eastport, Maine.


Individual Assistance


Individual Assistance Officer


International Boundary and Water Commission


Increased Cost of Compliance


Interagency Committee on Dam Safety


International Commission on Large Dams


Incident Command System


Individual and Family Grant


Integrated Financial Management Information System


FEMA Office of Inspector General


Interagency Incident Management Group

Immediate Needs Funding (INF)

An advance of grant funds to assist with payment of emergency work within the first 60 days after a disaster strikes. The amount of funding is normally 50% of the federal share of emergency costs as identified during the preliminary damage assessment.

Improved Property

A structure, facility or item of equipment that was built, constructed or manufactured. Land used for agricultural purposes is not improved property.


Information Management System

Inches of Mercury (Hg)

The name comes from the use of mercurial barometers that 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.

Inflow Design Flood

The flood flow above which the incremental increase in water surface elevation due to failure of a dam or other water impounding structure is no longer considered to present an unacceptable threat to downstream life or property. Also refers to the flood hydrograph used in the design of a dam and its appurtenant works particularly for sizing the spillway and outlet works and for determining maximum temporary storage, height of dam and freeboard requirements.

Inland High Wind Warning for Hurricane Force Winds

Announcement issued when winds of 74 mph (64 knots) or greater are predicted to occur within 12 hours

Inland High Wind Watch for Hurricane Force Winds

Announcement issued when winds of 74 mph (64 knots) or greater are predicted to occur within 24 hours


Immigration and Naturalization Service


Occurs when a rising air parcel becomes less dense than the surrounding air. Since its temperature will not cool as rapidly as the surrounding environment, it will continue to rise on its own. Contrasts with stable air.

Intertropical Convergence Zone (ITCZ)

The axis dividing the southeast trades from the northeast trades, toward which the surface winds tend to converge. The easterly trade winds of both hemispheres converge at an area near the equator called the Intertropical Convergence Zone (ICTZ), producing a narrow band of clouds and thunderstorms that encircle portions of the globe.

Inundation Map

Delineates areas that would be flooded as a result of a dam failure


Information Sharing and Analysis Center


White House Incident Support Group


The line drawn on a weather map connecting points of equal barometric pressure


Information technology


FEMA’s Information Technology Services Directorate

Jet stream

Relatively strong winds concentrated within a narrow current in the atmosphere


Joint Forces Headquarters (Homeland Security)


Joint Field Office


Joint Information Center


Joint Interagency Intelligence Support Element


Joint Operations Center


Joint Terrorism Task Force

Kickoff Meeting

The initial meeting between an applicant and the Public Assistance Coordinator. At this working session, the applicant turns in a list of damages and receives comprehensive information about the Public Assistance program and detailed guidance for their specific circumstances.




A unit for the measurement of speed in the nautical system. It is the nautical “miles per hour.”


Lowest adjacent grade (to a structure)


Local Area Network


The term used to describe where the hurricane eye actually passes over land, usually used to describe the continental States rather than islands in the Caribbean.

Large Project

An eligible project, either emergency or permanent work, with a damage dollar value of $52,000 or greater.


The location north or south in reference to the equator, which is designated at zero (0) degrees. Parallel lines that circle the globe both north and south of the equator. The poles are at 90 degrees North and South latitude.


The side of an object or obstacle, such as a ship’s sail, a mountain or a hill, furthest away from the wind, and therefore, protected from the direct force of the wind. The opposite of windward.


Local Emergency Operations Center


Lead Federal Agency


Letter of Final Determination


Local Hire


Limited Map Maintenance Program

Local Action Statement

A release prepared by a National Weather Service Forecast Office in or near a threatened area giving specific details for its area of responsibility


Letter of Determination Review




Letter of Map Amendment


Letter of Map Change


Letter of Map Revision


Letter of Map Revision Based on Fill


The location east or west in reference to the Prime Meridian, which is designated as zero (0) degrees longitude. The distance between lines of longitude are greater at the equator and smaller at the higher latitudes, intersecting at the earth’s North and South Poles. Time zones are correlated to longitude.


A region of low pressure

Low-Level Invest

An investigative mission for tropical disturbances to: 1) determine the existence or non-existence of a closed circulation (winds blowing in a complete circle); 2) supply weather observations in required areas; and 3) determine the vortex center, if any. These missions are flown at 500 to 1500 feet.

Low-Pressure System

An area of a relative pressure minimum that has converging winds and rotates in the same direction as the earth. This is counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. Also known as a cyclone, it is the opposite of an area of high pressure, or a anticyclone.


Statute Mile


Miscellaneous and Incidental Expenses


Meters Per Second


Mission Assignment


Military Assistance to Civil Authorities


Military Assistance for Civil Disturbances


Multi-Agency Coordination System

Maximum Envelope of Water (MEOW)

Describes the predicted areas inundated and amount of storm surge for a particular area during the landfall of a hurricane. Used in the SLOSH Model.

Maximum Envelope of Wind (MEOW)

Describes the predicted areas inundated and amount of wind for a particular area during the landfall of a hurricane. Used in the Inland Wind Model.



Mean Sea Level

The heights of the sea surface midway between its average high and low water positions.


Maximum Envelope of Water or Maximum Envelope of Winds


Mobile Emergency Response Support

Millibar (MB)

A metric measurement of atmospheric pressure used by the National Weather Service. Standard surface pressure is 1,013.2 millibars.


Metropolitan Medical Response System


Memorandum of Agreement


MERS Operations Center (FEMA)


Memorandum of Understanding


Management Profile


Miles per hour


Map Service Center


Military Support to Civil Authorities


Military Support to Civilian Law Enforcement Agencies


Model State Emergency Health Powers Act


Mine Safety and Health Administration


Mitigation Directorate


Mount Weather Emergency Assistance Branch


National Advisory Health Council


National Aeronautics and Space Administration

National Centers for Environmental Prediction (NCEP)

As part of the National Weather Service, the centers provide timely, accurate and continually improving worldwide forecast guidance products. Some of the centers include the Aviation Weather Center, the Climate Prediction Center, the Storm Prediction Center and the Tropical Prediction Center. Formerly known as NMC.

National Hurricane Center (NHC)

A branch of the Tropical Prediction Center under the National Weather Service, it is responsible for tracking and forecasting tropical cyclones over the North Atlantic, Caribbean, Gulf of Mexico and the Eastern Pacific.

National Oceanic and Atmospheric Administration (NOAA)

An administration of the U.S. Department of Commerce, it is the parent organization of the National Weather Service. It promotes global environmental stewardship, emphasizing atmospheric and marine resources.

National Weather Service (NWS)

A primary office of the National Oceanic and Atmospheric Administration responsible for all aspects of observing and forecasting atmospheric conditions and their consequences, including severe weather and flood warnings

Nautical Mile

A unit of length used in marine navigation equal to a minute of arc of a great circle on a sphere. One international nautical mile is equivalent to 1,852 meters or 1.151 statue miles. Refer to a sea mile.


National Warning System


National Oil and Hazardous Substances Pollution Contingency Plan


National Defense Authorization Act


National Disaster Medical System


FBI’s National Domestic Preparedness Office


National Dam Safety Information Technology Committee


National Emergency Coordination Center (FEMA)


National Earthquake Hazards Reduction Program


National Emergency Management Agency


National Emergency Management Information System


National Emergency Operations Center


National Environmental Policy Act


Nuclear Emergency Support Team


National Emergency Training Center

NEXRAD (Next Generation Weather Radar)

A network of advanced Doppler radars implemented in the United States between 1992 and 1996 which detects the location and intensity of precipitation extending to a range of 143 miles from the radar site. NEXRAD Doppler radar is highly sensitive and can detect precipitation from very light rain and snow up to the strongest thunderstorms with accuracy and detail. Sometimes, however, the radar’s extreme sensitivity will cause ground clutter and other non-precipitation echoes to be displayed in the vicinity of the radar site.


National Fire Academy


National Fire Information Council


National Flood Insurance Fund


National Flood Insurance Program


National Flood Insurance Reform Act


National Fire Incident Reporting System


National Guard Bureau


National Hurricane Center


National Historic Preservation Act


National Inventory of Dams


National Institute of Health


National Imagery and Mapping Agency


National Infrastructure Protection Center


Nuclear Incident Response Team


Nautical mile


National Marine Fisheries Service


National Medical Response Team


National Network Operations Branch


National Network Operations Center


National Oceanic and Atmospheric Service

NOAA Weather Radio

A 24-hour continuous broadcast of existing and forecasted weather conditions, operated and broadcast by the local field offices of the National Weather Service


Negotiations Operations Center


Notice of Interest


North America Aerospace Defense Command

North Atlantic Basin (sometimes called the Atlantic Basin)

The Atlantic Ocean north of the equator, the Caribbean Sea and the Gulf of Mexico


To inform appropriate individuals about an emergency condition so they can take appropriate action


National Performance of Dams Program


National Park Service


National Process Serving Center (FEMA)


Nuclear Regulatory Commission


National Resources Conservation Service


National Reconnaissance Organization


National Response Plan


FEMA’s Office of National Security Affairs


National Security Agency


National Security Council


National Security Telecommunications Advisory Committee


National Teleregistration Center (FEMA)


National Plan for Telecommunications Support in Non-Wartime Emergencies


National Voluntary Organizations Active in Disaster


National Weather Service


National Weather Service Forecasting Office

Occluded Front

The front formed by a cold front overtaking a warm or stationary front and lifting the warm air above the earth’s surface


Office of Emergency Preparedness


Other federal agencies


FEMA’s Office of Financial Management


Office of Management and Budget


FEMA’s Office of Policy and Regional Operations


Otherwise protected areas


FEMA’s Operations Support Directorate


On-Scene Commander (FBI), On-Scene Coordinator (EPA)


Occupational Safety and Health Administration


Office of Surface Mining


Office of Science and Technology Policy


Public Assistance

P Affairs O

Public Affairs Officer

P Assist O

Public Assistance Officer


Public Affairs


Private Branch Exchange


Personal Computer-Time and Attendance Report


Preliminary Damage Assessment


Presidential Decision Directive 39

Permanent Work

Work that must be performed through repairs or replacement to restore an eligible facility on the basis of its pre-disaster design, use and current applicable standards


Principal Federal Official Representative


Permanent full time


Public Health Service Act


Public Information Officer


Physical map revision


Purchase Officer

Polar-Orbiting Satellite

A satellite whose orbit passes over both of the earth’s poles. Compare with a geostationary satellite.

Post-Storm Report

A report issued by a local National Weather Service office summarizing the impact of a tropical cyclone on its forecast area. These reports include information on observed winds, pressures, storm surges, rainfall, tornadoes, damage and casualties.


Plant Protection Act


Prevention Preparedness Council

Pre-Eye Landfall Time

The time before actual hurricane eye landfall within which evacuation cannot be carried out because of earlier effects, such as the inundation of evacuation routes from the storm surge or rainfall and the arrival of sustained gale force winds. It is composed of the time of arrival of sustained gale-force winds or the time roadway inundation from storm surge/rainfall begins, whichever comes first.

Preliminary Damage Assessment (PDA)

A survey to determine the impact and magnitude of damage caused by the disaster and the resulting unmet needs of the public sector and community at large. The PDA is the basis for estimating total disaster-related damage and evaluating the need to request a Presidential declaration of disaster.

Preliminary Report

A report summarizing the life history and effects of an Atlantic or eastern Pacific tropical cyclone. It contains a summary of the cyclone life cycle and pertinent meteorological data, including the post-analysis best track (six-hourly positions and intensities) and other meteorological statistics. It also contains a description of damage and casualties the system produced, as well as information on forecasts and warnings associated with the cyclone. NHC writes a preliminary report on every tropical cyclone in its area of responsibility.

Present Movement

The best estimate of the movement of the center of a tropical cyclone at a given time and given position. This estimate does not reflect the short-period, small scale oscillations of the cyclone center.


The force per unit area exerted by the weight of the atmosphere above a point on or above the earth’s surface. Also known as atmospheric pressure or barometric pressure.

Private Nonprofit Organization (PNP)

Any non-governmental agency or entity that currently has either an effective ruling letter from the U.S. Internal Revenue Service granting tax exemption, or satisfactory evidence from the state that the non-revenue producing organization or entity is a nonprofit one organized or operating under state law.

Pro A

Programmatic Agreement

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Probability of Tropical Cyclone Conditions

The probability, in percent, that the cyclone center will pass within 50 miles to the right or 75 miles to the left of the listed location within the indicated time period when looking at the coast in the direction of the cyclone’s movement.


A logical method of performing work required as a result of the declared event

Project Formulation

A technique for determining small projects by consolidating like work items into one project, to expedite approval and funding and to facilitate project management

Project Officer (PO)

An emergency management employee with demonstrated experience and training in management of large and complex repair projects

Project Worksheet (PW)

A form used to document the damage and develop the scope of work for repair of a damage site


Preferred Risk Policy


FEMA’s Preparedness, Training and Exercises Directorate


Preparedness, Training and Exercises

Public Assistance (PA)

Supplementary federal assistance provided under the Stafford Act to state and local governments or certain private, nonprofit organizations, other than assistance for the direct benefit of individuals and families

Public Assistance Coordinator (PAC)

An emergency management employee who is responsible for providing continuity of service to an applicant in the Public Assistance program

Public Information Officer

A person appointed by a County Emergency Operations Center to be responsible for the formulating and coordinating of the dissemination of emergency public information with both the electronic and written media, ensuring that accurate information is being released to the general public


Principle User Processor


Resource and Recovery


Radio Amateur Civil Emergency Service

RADAR (Radio Detection and Ranging)

An electronic instrument using ultra high-frequency radio waves to detect distant objects and measure their range by how they scatter or reflect radio energy. Precipitation and clouds are detected by measuring the strength of the electromagnetic signal reflected back. Doppler radar and NEXRAD are examples.


Radiological Control Team


Precipitation in the form of liquid water droplets greater than 0.5 mm. If widely scattered, the drop size may be smaller. It is reported as r in an observation. The intensity of rain is based on rate of fall: very light (r–) means that the scattered drops do not completely wet a surface; light (r-) means it is greater than a trace and up to 0.10 inch an hour; moderate (r) means the rate of fall is between 0.11 to 0.30 inch per hour; heavy (r+) means over 0.30 inch per hour.

Rapid Deepening

A decrease in the minimum sea-level pressure of a tropical cyclone of 1.75 mb/hr or 42 mb for 24 hours


Residential Condominium Building Association Policy


Resource Conservation and Recovery Act


Regional Director


Radio Emergency Associated Communication Team


Regional Emergency Coordinator

Reconnaissance (RECCO) Code

An aircraft weather reconnaissance code that has come to refer primarily to in-flight tropical weather observations, but actually signifies any detailed weather observation or investigation from an aircraft in flight


A term used in an advisory to indicate that a vector drawn from the preceding advisory position to the latest know position is not necessarily a reasonable representation of the cyclone’s movement


Regional Environmental Officer


Regional Emergency Operations Center


Radiological Emergency Preparedness

Results Act

Government Performance and Results Act

Request for Public Assistance (Request)

The official notification of intent to apply for public assistance monies following declaration of a disaster. It is a short form that asks for general identifying information about an applicant.


Regional Operations Center


Response and Recovery; also FEMA’s Response and Recovery Directorate


Rapid Response Information System


Regional Response Team


Response Task Forces


Reimbursable Work Authorization


Salaries and Expenses


Special Agent-in-Charge

Saffir-Simpson Damage-Potential Scale

A scale from 1 to 5, developed in the early 1970s by Herbert Saffir, a consulting engineer, and Robert Simpson, then Director of the National Hurricane Center, to measure the intensity of a hurricane. The scale categorizes potential damage based on barometric pressure, wind speeds and storm surge. Scale numbers are available to public safety officials when a hurricane is within 72 hours of landfall. Scale assessments are revised regularly as new observations are made. Public safety organizations are kept informed of new estimates of the hurricane’s disaster potential.


Superfund Amendments & Reauthorization Act


Severe Acute Respiratory Syndrome


Used in reference to the manufactured objects that orbit the earth, either in a geostationary or a polar manner. Some of the information that is gathered by weather satellites, such as GOES9, includes upper air temperatures and humidity, recording the temperatures of cloud tops, land and ocean, monitoring the movement of clouds to determine upper level wind speeds, tracing the movement of water vapor, monitoring the sun and solar activity, and relaying data from weather instruments around the world.

Satellite Pictures

Pictures taken by a weather satellite, such as GOES-9, that reveal information, such as the flow of water vapor, the movement of frontal systems and the development of a tropical system. Looping individual pictures aids meteorologists in forecasting. Pictures can be taken is as a visible shot, which is best during times of visible light (daylight) or as an IR (infrared) shot, which reveals cloud temperatures and can be taken day or night.


Small Business Administration


Soldier & Biological Chemical Command (U.S. Army)


State Coordinating Officer


Special Direct Facility


Safety Evaluation of Existing Dams


State Emergency Operations Center

Severe Thunderstorm Warning

Issued to indicate that severe thunderstorms have been sighted or indicated on radar

Severe Thunderstorm Watch

Issued to indicate that conditions are favorable for lightning, damaging winds greater than 58 miles an hour, and hail and/or heavy rainfall.


Special Flood Hazard Area


Standard Flood Hazard Determination Form


Standard Flood Insurance Policy


Senior FEMA Official

Shelter Period

The period in which people are forced to evacuate their homes. This time may vary from several hours to a couple of days, depending upon the severity of the hurricane.


State Historic Preservation Office


A physical wind barrier that is affixed over the outside of windows and/or doors to protect these vulnerable areas during a tropical storm. These products are classified by the styles of panel (accordion or rolling) and are manufactured from steel, aluminum, plastic or plywood.


Strategic Industries and Economic Security


Strategic Information and Operations Center


Situation Report


Sea, Lake and Overland Surges for Hurricanes. A computerized model that is able to estimate the overland tidal surge heights and winds that result from hypothetical hurricanes with selected characteristics in pressure, size, forward speed, track and winds. The resultant tidal surge is then applied to a specific locale’s shoreline, incorporating the unique bay and river configurations, water depths, bridges, roads and other physical features. The model estimates open coastline heights as well as surge heights over land, thus predicting the degree of propagation or run-up of the surge into inland areas.

Small Craft Advisory

An advisory issued for marine interests, especially for operators of small boats or other vessels. Conditions include wind speeds between 20 knots (23 mph) and 34 knots (39 mph). Issued up to 12 hours ahead of conditions.

Small Project

An eligible project, either emergency or permanent work, with a damage dollar value of less than $52,000


Standard Mitigation Measures Agreement


State Management of Small Disasters


Standard Operating Procedures

Special Considerations

Factors that must be addressed before federal grant money can be obligated to repair or restore damaged facilities. These factors include, but are not limited to, general and flood insurance, historic preservation, environmental protection and hazard mitigation.

Special Marine Warning

A warning for hazardous weather conditions, usually short and not adequately covered by existing marine warnings. Such conditions include sustained winds or gusts of 35 knots or more for 2 hours or less.


An emergency management employee with demonstrated technical expertise in a defined specialty

Spiral Rainbands

Bands of thunderstorms that spiral inward towards the center, where they wrap themselves around the eye


A sudden increase of wind speed by at least 18 miles per hour (16 knots) and rising to 25 miles per hour (22 knots) or more and lasting for at least one minute

Stafford Act

Robert T. Stafford Disaster Relief and Emergency Assistance Act, Public Law 93-288, as amended

Standard Surface Pressure

The measurement of one atmosphere of pressure under standard conditions. It is equivalent to 1,013.25 millibars, 29.92 inches of mercury, 760 millimeters of mercury, 14.7 pounds per square inch, or 1.033 grams per square centimeter.

State of Emergency

A declaration made by the Chief Elected Official of a state, county or city government which entails a heightened level of activation and mobilization of staff to protect property and lives


Statutory Exclusion

Stationary Front

The boundary between two air masses, neither of which is replacing the other

Statute Mile

Commonly known as a ground mile


Sniper Tactical Operations Center


An individual low-pressure disturbance, complete with winds, clouds and precipitation. Examples include thunderstorms, tornadoes or even tropical cyclones. The name is associated with destructive or unpleasant weather.

Storm Surge

An abnormal rise in sea level accompanying a hurricane or other intense storm, and whose height is the difference between the observed level of the sea surface and the level that would have occurred in the absence of the cyclone. Storm surge is usually estimated by subtracting the normal or astronomic high tide from the observed storm tide. Note that waves on top of the storm surge will create an even greater high-water mark.

Storm Tide

The actual level of seawater resulting from the astronomic tide combined with the storm surge. If the storm comes ashore during astronomical low tide, the surge will be decreased by the amount of the low tide. If the storm makes landfall during astronomical high tide, the surge will be that much higher.

Storm Tracks

The path or tracks generally followed by a cyclonic disturbance


The region between the tropical and temperate regions, an area between 35 and 40 degrees North and South latitude. This is generally an area of semi-permanent high pressure, and is where the Azores and North Pacific Highs may be found.

Subtropical Cyclone

A low pressure system that develops over subtropical waters that initially has a non-tropical circulation but in which some elements of tropical cyclone cloud structure are present. Subtropical cyclones can evolve into tropical cyclones.

Subtropical Depression

A subtropical cyclone in which the maximum sustained surface wind speed (using the U.S. 1-minute average) is 38 mph (33 knots) or less

Subtropical High

A semi-permanent high-pressure region near 30 degrees latitude

Subtropical Storm

A subtropical cyclone in which the maximum sustained surface wind speed (using the U.S. 1-minute average) is 39 mph (34 knots) or more


The width of the path of the hurricane. Usually this path area is about 125 miles wide with 75 miles to the right of the eye and 50 miles to the left of the eye.


Department of Solid Waste Management

Synoptic Scale

The size of migratory high and low pressure systems, such as hurricanes, in the lower troposphere that cover a horizontal area of several hundred miles or more. Contrasts with macroscale, mesoscale and storms.

Synoptic Surveillance Track

Weather reconnaissance mission flown to provide vital meteorological information in data-sparse ocean areas as a supplement to existing surface, radar and satellite data. Synoptic flights better define the upper atmosphere and aid in the prediction of tropical cyclone development and movement.


Threatened and Endangered


Technical Assistance Contractor


Training Aids for Dam Safety


Tropical Analysis and Forecast Branch (TPC)


The water immediately downstream from a dam. The water surface elevation varies due to fluctuations in the outflow from the structures of a dam. Tailwater monitoring is an important consideration because a failure of a dam will cause a rapid rise in the level of the tailwater.


Threat Countermeasures and Incident Management Directorate


Tropical Depression


Temporary duty


Technical Evaluation Contractor


Technical Escort Unit


Temporary housing


Temporary Housing Officer


Tribal Historic Preservation Officer (refers to activities on native American tribal lands)


The sound that follows a flash of lightning and is caused by sudden expansion of the air in the path of the electrical discharge


A local storm produced by a cumulonimbus cloud, always with lightning and thunder, and usually accompanied by strong gusts of wind, heavy rain and sometimes hail


Territorial Logistics Center


Tactical Operations Center


A violently rotating column of air in contact with and extending between a convective cloud and the surface of the earth. It is the most destructive of all storm-scale atmospheric phenomena. They can occur anywhere in the world given the right conditions, especially after the landfall of hurricanes.


Tropical Prediction Center

Trade Winds

The wind system, occupying most of the tropics, which are northeasterly in the Northern Hemisphere and southeasterly in the Southern Hemisphere.


Travel, Reporting and Information Processing System

Tropical Cyclone

A general term for all cyclone circulations originating over tropical waters. Its characteristics include a warm-core, non-frontal pressure system of synoptic scale that originates over the tropical or subtropical waters and has a definite organized surface. Used to define wind circulations rotating around an atmosphere which includes tropical depressions, tropical storms and hurricanes. The strongest winds of this cyclone are typically near the Earth’s surface.

Tropical Cyclone Plan of the Day

A coordinated mission plan that tasks operational weather reconnaissance requirements as required. Describes reconnaissance flights committed to satisfy both operational and research requirements, and identifies possible reconnaissance requirements for the succeeding 24-hour period.

Tropical Depression (TD)

A tropical cyclone in which the maximum sustained surface winds (1 minute average) are 38 miles per hour (33 knots) or less. Characteristically having one or more closed isobars, it may form slowly from a tropical disturbance or an easterly wave which has continued to organize. At this point, it gets a cyclone number, starting with TD01 at the beginning of each storm season.

Tropical Disturbance

A discrete system of clouds, showers and thunderstorms (organized convection) that originate in the tropics. Generally 100 to 300 miles in diameter and originating in the tropics or subtropics, disturbances have a non-frontal migratory character, and maintain their identity for 24 hours or more. It may or may not be associated with a detectable perturbation of the wind field. An upper level of low pressure causes this to occur. Approximately 100 of these types of events occur annually during hurricane season.

Tropical Prediction Center

A division of the National Centers for Environmental Prediction, the Center issues watches, warnings, forecasts and analyses of hazardous weather conditions in the tropics for both domestic and international communities which include the Atlantic, Caribbean, Gulf of Mexico and Eastern Pacific. The National Hurricane Center is one of its branches.

Tropical Storm (TS)

A tropical cyclone in which the maximum sustained surface wind speed (1 minute average) is within the range of 39 to 73 mph (34 to 63 knots). At this point, the system is given a name to identify and track it. In the Atlantic/Caribbean/Gulf of Mexico basin, the names start with A each season.

Tropical Storm Warning

A warning issued by the National Hurricane Center for tropical storm conditions including possible sustained winds within the range 39 to 73 mph (34 to 63 knots) which are expected in a specified coastal area within 24 hours or less.

Tropical Storm Watch

An announcement issued by the National Hurricane Center for specific areas that a tropical storm or a forecast of tropical storm conditions poses a possible threat to coastal areas generally within 36 hours. A tropical storm watch normally should not be issued if the system is forecast to attain hurricane strength.

Tropical Wave

Another name for an easterly wave, it is an area of relatively low pressure (trough) moving westward through the trade wind easterlies. Generally, it is associated with extensive cloudiness and showers, and may be associated with possible tropical cyclone development.


The region of the earth located between the Tropic of Cancer, at 23.5 degrees North latitude, and the Tropic of Capricorn, at 23.5 degrees South latitude. It encompasses the equatorial region, an area of high temperatures and considerable precipitation during part of the year.


Tropical storm


Technical Support Branch (TPC).


Tennessee Valley Authority


A hurricane that occurs in the Pacific Region of the Philippines or the China Sea


Urban Areas Security Initiative, provides direct funding for high threat areas


Unified Command

Universal Time Coordinate (UTC)

One of several names for the twenty-four hour time that is used throughout the scientific and military communities. Other names for this time measurement are Greenwich Mean Time (GMT) or Zulu Time (Z). See Greenwich Mean Time for more information.


The process by which water rises from a lower to a higher depth, usually as a result of divergence and offshore currents. It influences climate by bringing colder, more nutrient-rich water to the surface. This is a vital factor of the El Nino event.


Urban Search & Rescue


U.S. Army Corps of Engineers


U.S. Air Force


U.S. Bureau of Reclamation


United States Code Annotated


U.S. Coast Guard

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U.S. Food and Drug Administration


United States Fire Administration


United States Forest Service


U.S. Fish and Wildlife Service


United States Government Interagency Domestic Terrorism Concept of Operations Plan


U.S. Geological Survey


U.S. Navy


United States Society on Dams


Universal Time Coordinate


The pre-funding verification that proposed or completed work projects meet statutory and regulatory compliance


Voluntary Agent


Any circular or rotary flow in the atmosphere that possesses vorticity

Vortex Fix

The location of the surface and/or flight level center of a tropical or subtropical cyclone obtained by reconnaissance aircraft penetration


The measurement of the rotation of a small air parcel. It has vorticity when the parcel spins as it moves along its path. Although the axis of the rotation can extend in any direction, meteorologists are primarily concerned with the rotational motion about an axis that is perpendicular to the earth’s surface. If it does not spin, it is said to have zero vorticity. In the Northern Hemisphere, the vorticity is positive when the parcel has a counterclockwise, or cyclonic, rotation. It is negative when the parcel has clockwise, or anticyclonic, rotation.

Warm Front

The leading edge of an advancing warm air mass that is replacing a retreating relatively colder air mass. Generally, with the passage of a warm front, the temperature and humidity increase, the pressure rises, and although the wind shifts (usually from the southwest to the northwest in the Northern Hemisphere), it is not as pronounced as with a cold frontal passage. Precipitation, in the form of rain, snow or drizzle, is generally found ahead of the surface front, as well as convective showers and thunderstorms. Fog is common in the cold air ahead of the front. Although clearing usually occurs after passage, some conditions may produced fog in the warm air. See occluded front and cold front.


An announcement that is issued when severe weather: 1) has developed; 2) is already occurring and reported; or 3) is detected on radar. Warnings state a particular hazard or imminent danger, such as tornadoes, severe thunderstorms, flash and river floods, hurricanes, etc.

Weather Surveillance Radar (WSR-88D)

The newest generation of Doppler radars. These radar units, with help from a set of computers, show very detailed images of precipitation and other phenomena, including air motions within a storm.


Weather Forecast Office


The direction from which the wind is blowing. Also known as the upwind side of an object. It is the opposite of the downwind or leeward side.


Weapon of Mass Destruction


Weapons of Mass Destruction Civil Support Team


World Wide Web


Write Your Own


Zulu Time

Zulu Time (Z)

One of several names for the twenty-four hour time that is used throughout the scientific and military communities. Other names for this time measurement are Universal Time Coordinate (UTC) or Greenwich Mean Time (GMT). See Greenwich Mean Time for more information.