Subj : Weather Glossary (N)
To : All
From : Daryl Stout
Date : Mon Jul 15 2019 12:02 am
This weather glossary contains information on more than 2000 terms,
phrases and abbreviations used by the National Weather Service (NWS)...
the government agency who makes weather forecasts, and issues weather
advisories, watches, and warnings, for the United States, and its
territories.
Many of these terms and abbreviations are used by NWS forecasters to
communicate between each other and have been in use for many years and
before many NWS products were directly available to the public. It is the
purpose of this glossary to aid you in better understanding NWS products.
***
N
North
Nacreous Clouds
Clouds of unknown composition that have a soft, pearly luster and that
form at altitudes about 25 to 30 km above the Earth's surface. They are
also called "mother-of-the-pearl clouds."
Nadir
The point on any given observer's celestial sphere diametrically opposite
of one's zenith.
NAM
The operational North Amercian Meso (NAM, formerly Eta) is run four times
per day (00,06,12,18Z), all cycles run to 84-h.
Nanotesla (nT)
A unit of magnetism equal to 10-9 tesla, equivalent to a gamma
(10-5 gauss).
NAO
North Atlantic Oscillation - the NAO is a large-scale fluctuation in
atmospheric pressure between the subtropical high pressure system located
near the Azores in the Atlantic Ocean and the sub-polar low pressure
system near Iceland and is quantified in the NAO Index. The surface
pressure drives surface winds and wintertime storms from west to east
across the North Atlantic affecting climate from New England to western
Europe as far eastward as central Siberia and eastern Mediterranean and
southward to West Africa.
NAO Index
This index measures the anomalies in sea level pressure between the
Icelandic low pressure system and the Azores high pressure system in the
North Atlantic Ocean.
When the NAO is in its is positive phase (+NAO), the northeastern United
States sees an increase in temperature and a decrease in snow days; the
central US has increased precipitation, the North Sea has an increase in
storms; and Norway along with Northern Europe has warmer temperatures and
increased precipitation.
When the NAO is in its negative phase (-NAO), the Tropical Atlantic and
Gulf coast have increased number of strong hurricanes; northern Europe is
drier, and Turkey along with other Mediterranean countries has increased
precipitation.
National Ambient Air Quality Standards
In the United States, national standards for the ambient concentrations
in air of different air pollutants designed to protect human health and
welfare.
National Climatic Data Center
The agency that archives climatic data from the National Oceanic and
Atmospheric Administration, as well as other climatological organizations.
National Digital Forecast Database
(NDFD)- The National Weather Service's NDFD provides access to gridded
forecasts of sensible weather elements (e.g., wind, wave height) through
the National Digital Forecast Database (NDFD). NDFD contains a seamless
mosaic of digital forecasts from NWS field offices working in
collaboration with the National Centers for Environmental Prediction
(NCEP). The database is made available to all customers and partners from
the public, private and academic sectors. Those customers and partners
may use this data to create a wide range of text, graphic, gridded and
image products of their own.
National Fire Danger Rating System
A uniform fire danger rating system used in the United States that
focuses on the environmental factors that impact the moisture content
of fuels. Fire danger is rated daily over large administrative areas,
such as national forests.
National Flood Summary
This NWS daily product (abbreviated FLN) contains nationwide information
on current flood conditions. It is issued by the Hydrometeorological
Information Center of the Office of Hydrology.
National Hurricane Center
One of three branches of the Tropical Prediction Center (TPC). This
center maintains a continuous watch on tropical cyclones over the
Atlantic, Caribbean, Gulf of Mexico, and the Eastern Pacific from 15 May
through November 30. The Center prepares and distributes hurricane
watches and warnings for the general public, and also prepares and
distributes marine and military advisories for other users. During the
"off-season" NHC provides training for U.S. emergency managers and
representatives from many other countries that are affected by
tropical cyclones. NHC also conducts applied research to evaluate and
improve hurricane forecasting techniques, and is involved in public
awareness programs.
National Hurricane Operations Plan
(NHOP) - The NHOP is issued annually by the Federal Coordinator for
Meteorological Services and Supporting Research. It documents
interdepartmental agreements relating to tropical cyclone observing,
warning, and forecasting services. National Hurricane Center (NHC),
Central Pacific Hurricane Center (CPHC), and the JTWC serve as the
principal offices in coordinating the day-to-day activities of the NWS
in support of the Plan in their region of responsibility.
National Severe Storms Laboratory
This is one of NOAA's internationally known Environmental Research
Laboratories, leading the way in investigations of all aspects of
severe weather. Headquartered in Norman OK with staff in Colorado,
Nevada, Washington, Utah, and Wisconsin, the people of NSSL, in
partnership with the National Weather Service, are dedicated to
improving severe weather warnings and forecasts in order to save
lives and reduce property damage.
National Weather and Crop Summary
A product of the National Agricultural Statistics Service,
Agricultural Statistics Board, and U.S. Department of Agriculture.
It contains weekly national agricultural weather summaries,
including the weather's effect on crops; summaries and farm progress
for 44 states and New England area.
Natural Control
In hydrologic terms, a stream gaging control which is natural to the
stream channel, in contrast to an artificial control structure by man.
Nautical Dawn
The time at which the sun is 12 degrees below the horizon in the
morning. Nautical dawn is defined as that time at which there is just
enough sunlight for objects to be distiguishable.
Nautical Dusk
The time at which the sun is 12 degrees below the horizon in the
evening. At this time, objects are no longer distinguishable.
Nautical Mile
A unit of distance used in marine navigation and marine forecasts. It
is equal to 1.15 statue miles or 1852 meters. It is also the length of
1 minute of latitude.
Nautical Twilight
The time after civil twilight, when the brighter stars used for
celestial navigation have appeared and the horizon may still be seen.
It ends when the center of the sun is 12 degrees below the horizon,
and it is too difficult to perceive the horizon, preventing accurate
sighting of stars.
Navigation Methods
In hydrologic terms, there are three basic methods of providing and
managing inland waterways -
1) Run-of-the-River: no provision of upstream storage;
2) Slack-Water: locks and dams provide slack water or pools with
adequate depth for the draft of heavy barges and area to prevent
excessive velocities;
3) Canalization: in lieu of a series of dams on the river a canal with
locks adjoins the river.
NAVTEX
An international automated medium frequency (518 kHz) direct-printing
service for delivery of navigational and meteorological warnings and
forecasts, as well as urgent marine safety information to ships. It
was developed to provide a low-cost, simple, and automated means of
receiving this information aboard ships at sea within approximately
200 nautical miles of shore and is an element of the Global Maritime
Distress and Safety System (GMDSS). NAVTEX stations in the U.S. are
operated by the U.S. Coast Guard. There are no user fees associated
with receiving NAVTEX broadcasts. The International System uses the
frequency of 518 kHz worldwide and optional National Systems use
frequencies of 490 and 4205.5 kHz. Safety messages on 518 kHz have
to be in the English language worldwide but broadcasts on the 490 and
4209.5 kHz frequency can be in the local language.
NAVTEX Forecast
(NAV) - A National Weather Service marine forecast combining various
Coastal Waters and Offshore forecasts, optimized to accommodate
transmission via NAVTEX.
NBND
Northbound
NC
1. No change
2. North Carolina
NCAR
National Center for Atmospheric Research
NCCF
NOAA Central Computer Facility
NCDC
National Climatic Data Center
NCEP
National Centers for Environmental Prediction. A part of the National
Weather Service which provides nationwide computerized and manual
guidance to Warning and Forecast Offices concerning the forecast of
basic weather elements.
NDBC
National Data Buoy Center
NDFD
(National Digital Forecast Database) - The National Weather Service's
NDFD provides access to gridded forecasts of sensible weather elements
(e.g., wind, wave height) through the National Digital Forecast
Database (NDFD). NDFD contains a seamless mosaic of digital forecasts
from NWS field offices working in collaboration with the National
Centers for Environmental Prediction (NCEP). The database is made
available to all customers and partners from the public, private and
academic sectors. Those customers and partners may use this data to
create a wide range of text, graphic, gridded and image products of
their own.
NE
Northeast
Neap Tide
A minimum tide occurring at the first and third quarters of the moon.
Nearshore Forecast
(NSH) - National Weather Service seasonal marine forecasts for an area
of the Great Lakes extending from a line approximating mean low water
datum along the coast or an island, including bays, harbors, and sounds,
out to 5 nm. These forecasts are normally issued from Daylight Savings
Time approximately April 7 through December 31, though the dates may be
shortened or extended based on local/regional requirements.
NEC
Necessary
NEG
Negative
Negative Vorticity Advection
(Abbrev. NVA) - the advection of lower values of vorticity into an area.
Negative-tilt Trough
An upper level system which is tilted to the west with increasing
latitude (i.e., with an axis from southeast to northwest). A
negative-tilt trough often is a sign of a developing or intensifying
system.
NELY
Northeasterly
NERN
Northeastern
NESDIS
National Environmental Satellite, Data, and Information Service. NESDIS
collects, processes, stores, analyzes, and disseminates various types
of hydrologic, meteorologic, and oceanic data. NESDIS is also
responsible for the development of analytical and descriptive products
so as to meet the needs of its users.
Net All-Wave Radiation
The net or resultant value of the upward and downward longwave and
shortwave radiative fluxes through a plane at the earth-atmosphere
interface; a component of the surface energy budget.
Net Rainfall
In hydrologic terms, the portion of rainfall which reaches a stream
channel or the concentration point as direct surface flow.
Neutral Line
The line that separates longitudinal magnetic fields of opposite
polarity.
Neutral Stability
An atmospheric condition that exists in unsaturated air when the
environmental lapse rate equals the dry adiabatic rate, or in saturated
air when the environmental lapse rate equals the moist adiabatic rate.
NEWD
Northeastward
NEXRAD
NEXt Generation RADar. A NWS network of about 140 Doppler radars
operating nationwide.
NGM
The Nested Grid Model, a 48-hour numerical model of the atmosphere run
twice daily by NCEP.
NGT
Night
NHC
National Hurricane Center - one of three branches of the Tropical
Prediction Center (TPC). This center maintains a continuous watch on
tropical cyclones over the Atlantic, Caribbean, Gulf of Mexico, and the
Eastern Pacific from 15 May through November 30. The Center prepares
and distributes hurricane watches and warnings for the general public,
and also prepares and distributes marine and military advisories for
other users. During the "off-season" NHC provides training for U.S.
emergency managers and representatives from many other countries that
are affected by tropical cyclones. NHC also conducts applied research
to evaluate and improve hurricane forecasting techniques, and is
involved in public awareness programs.
NHOP
(National Hurricane Operations Plan) - The NHOP is issued annually by
the Federal Coordinator for Meteorological Services and Supporting
Research. It documents interdepartmental agreements relating to
tropical cyclone observing, warning, and forecasting services. National
Hurricane Center (NHC), Central Pacific Hurricane Center (CPHC), and
the JTWC serve as the principal offices in coordinating the day-to-day
activities of the NWS in support of the Plan in their region of
responsibility.
Nieve Penitente
A spike or pillar of compacted snow, firn or glacier ice, caused by
differential melting and evaporation. The pillars form most frequently
on low-latitude mountains where air temperatures are near freezing,
dew points are much below freezing and insolation is strong. Penitents
are oriented individually toward the noon-day sun, and usually occur
in east-west lines.
Night
The period of the day between dusk and dawn.
NIL
None
Nimbostratus
(abbrev. NS)- A cloud of the class characterized by a formless layer
that is almost uniformly dark gray; a rain cloud of the layer type, of
low altitude, usually below 8000 ft (2400 m).
NLY
Northerly
NM
Nautical Miles
NMBR
Number
NMC
National Meteorological Center
NML
Normal
NMRS
Numerous
NOAA
National Oceanic and Atmospheric Administration
NOAA Weather Radio
"The voice of the National Weather Service" - NOAA Weather Radio
broadcasts National Weather Service warnings, watches, forecasts
and other hazard information 24 hours a day. It is provided as a
public service by NOAA. The NOAA Weather Radio network has more
than 480 stations in the 50 states and near adjacent coastal waters,
Puerto Rico, the U.S. Virgin Islands and U.S. Pacific Territories.
It operates between 162.40 and 162.55 Megahertz on the Public Service
Band.
NOAA Weather Wire
Mass dissemination via satellite of National Weather Service products
to the media and public.
Noctilucent Clouds
Wavy, thin, bluish-white clouds that are best seen at twilight in
polar latitudes. They form at altitudes about 80 to 90 km above the
Earth's surface.
Nocturnal
Related to nighttime; occurring at night.
Nocturnal Inversion
Used interchangably with Radiational Inversion; a temperature inversion
that develops during the night as a result of radiational cooling of
the surface. Because the immediate surface (lower Boundary Layer) cools
much more rapidly during radiational cooling conditions than the air
just above (upper Boundary Layer), a temperature inversion can be
created overnight, but typically erodes quickly after sunrise.
Nocturnal Jet
This wind speed maximum occurs just above the nocturnal inversion at
night. It is typically found in the south central United States during
the late spring and summer months. It is important in the development
of Mesoscale Convective Complexes (MCC) or Mesoscale Convective Systems
(MCS).
Nocturnal Thunderstorms
Thunderstorms which develop after sunset. They are often associated
with the strengthening of the low level jet and are most common over
the Plains states. They also occur over warm water and may be
associated with the seaward extent of the overnight land breeze.
NOGAPS
Navy Operational Global Atmospheric Prediction System; a 144-hour
numerical model of the atmosphere run by the U.S. Navy twice daily.
NOHRSC
In hydrologic terms, the National Operational Hydrologic Remote Sensing
Center. An organization under the National Weather Service Office of
Hydrology (OH) that mainly deals with snow mapping.
Non-Uniform Sky Condition
A localized sky condition which varies from that reported in the body
of the report.
Non-Uniform Visibility
A localized visibility which varies from that reported in the body of
the report.
Nonattainment Area
An area that does not meet ambient air quality standards.
Normal
The long-term average value of a meteorological paramater (i.e.,
temperature, humidity, etc.) for a certain area. For example,
"temperatures are normal for this time of year" means that temperatures
are at or near the average climatological value for the given date.
Normals are usually taken from data averaged over a 30-year period
(e.g., 1971-2000 average), and are concerned with the distribution of
data within limits of common occurrence.
Normal Water Surface Elevation
In hydrologic terms, the lowest crest level of overflow on a reservoir
with a fixed overflow level (spillway crest elevation). For a reservoir
whose outflow is controlled wholly or partly by movable gates, siphons,
or other means, it is the maximum level to which water may rise under
normal operating conditions, exclusive of any provision for flood
surcharge.
Normal Year
A year during which the precipitation or stream flow approximates the
average for a long period of record.
North Atlantic Oscillation
(Abbrev. NAO) - the NAO is a large-scale fluctuation in atmospheric
pressure between the subtropical high pressure system located near the
Azores in the Atlantic Ocean and the sub-polar low pressure system near
Iceland and is quantified in the NAO Index. The surface pressure drives
surface winds and wintertime storms from west to east across the North
Atlantic affecting climate from New England to western Europe as far
eastward as central Siberia and eastern Mediterranean and southward to
West Africa.
North Pacific High
A semi-permanent, subtropical area of high pressure in the North Pacific
Ocean. It is strongest in the Northern Hemispheric summer and is
displaced towards the equator during the winter when the Aleutian Low
becomes more dominate. Comparable systems are the Azores High and the
Bermuda High.
North Wall
The north side boundary of the Gulf Stream generally extending northeast
from Cape Hatteras where the Gulf Stream turns northeast.
Northern Lights
Common name for Aurora Borealis; the luminous, radiant emission from the
upper atmosphere over middle and high latitudes, and centred around the
earth's magnetic poles. These silent fireworks are often seen on clear
winter nights in a variety of shapes and colours.
Nor'easter
A strong low pressure system that affects the Mid Atlantic and New
England States. It can form over land or over the coastal waters. These
winter weather events are notorious for producing heavy snow, rain, and
tremendous waves that crash onto Atlantic beaches, often causing beach
erosion and structural damage. Wind gusts associated with these storms
can exceed hurricane force in intensity. A nor'easter gets its name from
the continuously strong northeasterly winds blowing in from the ocean
ahead of the storm and over the coastal areas.
Nowcast
A short-term weather forecast, generally out to six hours or less. This
is also called a Short Term Forecast.
NR
Near
NRN
Northern
NRW
Narrow
NS
Nimbostratus- A cloud of the class characterized by a formless layer that
is almost uniformly dark gray; a rain cloud of the layer type, of low
altitude, usually below 8000 ft (2400 m).
NSSFC
National Severe Storm Forecast Center
NSSL
National Severe Storms Laboratory - this is one of NOAA's internationally
known Environmental Research Laboratories, leading the way in
investigations of all aspects of severe weather. Headquartered in Norman
OK with staff in Colorado, Nevada, Washington, Utah, and Wisconsin, the
people of NSSL, in partnership with the National Weather Service, are
dedicated to improving severe weather warnings and forecasts in order to
save lives and reduce property damage.
Numerical Forecasting
A computer forecast or prediction based on equations governing the
motions and the forces affecting motion of fluids. The equations are
based, or initialized, on specified weather or climate conditions at a
certain place and time.
Numerical Weather Prediction
Same as Numerical Forecasting; a computer forecast or prediction based
on equations governing the motions and the forces affecting motion of
fluids. The equations are based, or initialized, on specified weather
or climate conditions at a certain place and time.
Numerous
A National Weather Service convective precipitation descriptor for a
60 or 70 percent chance of measurable precipitation (0.01 inch).
NVA
Negative Vorticity Advection - the advection of lower values of vorticity
into an area.
NW
Northwest
NWD
Northward
NWLY
Northwesterly
NWP
Numerical Weather Prediction
NWR
NOAA Weather Radio - "the voice of the National Weather Service" - NOAA
Weather Radio broadcasts National Weather Service warnings, watches,
forecasts and other hazard information 24 hours a day. It is provided as
a public service by NOAA. The NOAA Weather Radio network has more than
480 stations in the 50 states and near adjacent coastal waters, Puerto
Rico, the U.S. Virgin Islands and U.S. Pacific Territories. It is found
from 162.40 to 162.55 Megahertz on the Public Service Band.
NWRD
Northwestward
NWRN
Northwestern
NWS
National Weather Service. An agency of the Federal Government within
the Department of Commerce, National Oceanic and Atmospheric
Administration, which is responsible for providing observations,
forecasts and warnings of meteorological and hydrological events in
the interest of national safety and economy.
NWSH
National Weather Service Headquarters
NWSO
National Weather Service Office
NXT
Next
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