The National Weather Service has launched a new initiative entitled "Weather-Ready Nation", which is designed to increase the public's ability to recognize severe weather conditions
and to take the appropriate actions to remain safe and secure. The NWS is now offering a free online training course for this new initiative.
Some in-person training courses are available in the Memphis, Tennessee area.
Other weather-related courses are available HERE.
Local National Weather Service Offices
Local National Weather Service offices provide localized weather alerts and forecasts. Individual NWS offices can be selected from the list below
for additional information about a specific locale.
NOAA Weather Radio Stations
SKYWARN Severe Weather Spotter Network
SKYWARN
is a network of trained volunteer severe weather spotters who provide accurate eyewitness severe weather reports to their local National Weather Service office. Join now! Online Training (2 Hrs)Local Training (by State)
Ham radio operators play an important role in emergency weather situations, often providing a vital link to storm-stricken communities without power or telephone service.
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A Glossary of Weather-Related Terms Click on a term for an explanation.
Atmospheric Pressure
Atmospheric pressure, also known as barometric pressure, is the force-per-area that the atmosphere exerts upon every object which is exposed to the air. At sea level, the average pressure
is defined as 1 Atm (Atmosphere). Pressure can be quantified in several units of measure. All of the following values are equivalent to one another.
1 Atm (Atmosphere)
14.7 PSI (Pounds per Square Inch)
29.9213 inHg (Inches of Mercury)
760 mmHg (Millimeters of Mercury)
1013.25 mbars (Millibars)
101.325 kPa (Kilopascals)
The table below displays the mathematical operations necessary to convert between the various units of measure for atmospheric pressure.
Pressure Scale Conversion Equations
Atm=PSI/14.7
Atm=inHg/29.9213
Atm=mmHg/760.0
Atm=mbars/1013.25
Atm=kPa/101.323
PSI=Atm*14.7
PSI=inHg/2.035
PSI=mmHg/51.7
PSI=mbars/68.93
PSI=kPa/6.893
inHg=Atm*29.9213
inHg=PSI*2.035
inHg=mmHg/25.4
inHg=mbars/33.864
inHg=kPa/3.3864
mmHg=Atm*760
mmHg=PSI*51.7
mmHg=inHg*25.4
mmHg=mbars/1.333
mmHg=kPa*7.5
mbars=Atm*1013.25
mbars=PSI*68.93
mbars=inHg*33.86
mbars=mmHg*1.333
mbars=kPa*10
kPa=Atm*101.325
kPa=PSI*6.893
kPa=inHg*3.386
kPa=mmHg/7.5
kPa=mbars/10
Blizzard
A blizzard is an extremely severe snowstorm which possesses the following characteristics for a period of 3 hours or longer: sustained wind speeds or frequent gusts to 35 miles an hour or greater,
and considerable falling or blowing snow which frequently reduces visibility to less than 1/4 mile. Blizzards can be incredibly large, often covering hundreds or thousands of square miles,
and occur most often in temperate, polar, or mountainous regions during the winter.
Climate
Climate is the prevailing state of atmospheric conditions for a particular region over a considerable period of time.
The metrics used for climate study include temperature, atmospheric pressure, precipitation, humidity, wind, and any other meteorological phenomena deemed necessary.
Climate conditions have always been dynamic and properly contextualized evidence suggests that human activity has had a negligible effect on worldwide climate.
Cyclone
A cyclone is a spiraling air mass which circulates around a strong central region of low atmospheric pressure. Cyclones in the northern hemisphere rotate counterclockwise while cyclones
in the southern hemisphere rotate in a clockwise direction. Hurricanes which form in the Indian Ocean are referred to as cyclones. Tornadoes are often referred to colloquially as cyclones.
Derecho
A derecho is a widespread straight-line wind storm that is associated with a group of fast-moving severe thunderstorms. Derechos can cause hurricane-force winds, tornadoes, heavy rains, and flash floods. Derechos are a warm-weather phenomenon, occurring mostly in summer, especially during June, July, and August in the Northern Hemisphere.
Dew Point
The dew point is the temperature to which air must be cooled to become saturated with water vapor (assuming air pressure and moisture content are constant).
When further cooled, the airborne water vapor will condense to form liquid water (dew). When air cools to its dew point through contact with a surface that is colder than the air,
water will condense on the surface. When the temperature is below the freezing point of water, the dew point is called the frost point, as frost is formed rather than dew.
Downburst
A downburst is a strong wind system that emanates from a high-altitude point and blows downward until it contacts the surface of the earth.
The high-velocity winds then blow radially in straight lines in all directions from the point of contact with the ground.
Microbursts and macrobursts are downbursts at very small and very large scales, respectively.
Microbursts pose an extreme danger to aviation because their small size (less than 2.5 miles in diameter) makes them difficult to detect in a timely manner.
Eye/Eyewall
The eye is the relatively calm circular central region of hurricanes and strong tropical cyclones. It is typically 19 to 40 miles in diameter. It is surrounded by the eyewall,
a ring of extremely high-velocity winds which cause much of the damage done by hurricanes. The lowest barometric pressure occurs in the eye and can be as much as 15 percent lower than the pressure outside the storm.
Flood
Flood ... Flood Stage ... Flash Flood ...
Gale
X
Haboob
Haboob
Heat Index
Heat Index
Humidity
Humidity
Hurricane
A hurricane is a class of ocean-generated storms with strong circulating winds which have sustained wind speeds of at least 74 MPH (Miles Per Hour)
around a central eye of calmer winds. Storms of this type are known as hurricanes if they occur in the Atlantic Ocean or eastern Pacific Ocean. They are called typhoons if they occur in the central or
western Pacific Ocean. In the Indian Ocean, they are referred to as cyclones. Hurricanes names are available here.
Hurricanes are classified into five categories using the Saffir-Simpson wind speed scale as shown in the table below. Hurricanes are classified as "major" if they are a Category 3 or higher.
Saffir-Simpson Hurricane Scale
Sustained Wind Speed (MPH)
Classification
Less Than 39
Tropical Depression
39 - 73
Tropical Storm
74 - 95
Category 1 Hurricane
96 - 110
Category 2 Hurricane
111 - 129
Category 3 Hurricane
130 - 156
Category 4 Hurricane
Greater Than 156
Category 5 Hurricane
More information about the Saffir-Simpson scale is available here.
More information about hurricanes is available at the National Hurricane Center.
Monsoon
X
Nor'Easter
X
Storm Surge
X
Temperature
Temperature is a measure of the amount of heat in an object relative to a reference scale.
There are four standard temperature scales: Fahrenheit, Celsius (formerly known as Centigrade), Kelvin, and Rankin. The Fahrenheit and Rankin scales
are linearly related and the Celsius and Kelvin scales are linearly related. Absolute zero, the temperature at which all particle motion ceases, is -459.67°F, -273.15°C, 0°K, and 0°R.
The table below shows the equations needed to convert between all of these temperature scales.
Temperature Scale Conversion Equations
Find \ From
From °F
From °C
From °K
From °R
Find °F
F = ( 1.8C ) + 32
F = ( 1.8K ) - 459.67
F = R - 459.67
Find °C
C = ( F - 32 ) / 1.8
C = K - 273.15
C = ( R - 491.67 ) / 1.8
Find °K
K = ( F / 1.8 ) + 255.37
K = C + 273.15
K = R / 1.8
Find °R
R = F + 459.67
R = ( 1.8C ) + 491.67
R = 1.8K
Tornado
A tornado is a class of violent storms with strong circulating winds which have 3-second wind gusts of at least 65 MPH (Miles Per Hour).
The strength of tornadoes is classified on the Enhanced Fujita Scale by an examination of the damage caused by the storm. Tornadoes are more prevalent in the United States than anywhere else in the world.
The states of Iowa, Nebraska, Kansas, Oklahoma, and Texas are collectively known as "Tornado Alley" because of the number of tornadoes which form in those states.
The table below shows the Enhanced Fujita Scale and the now-deprecated Original Fujita Scale.
Enhanced-Fujita Tornado Scale
Enhanced Fujita Scale
Original Fujita Scale
EF #
3-Second Gust (MPH)
F #
3-Second Gust (MPH)
EF0
65-85
F0
45-78
EF1
86-110
F1
79-117
EF2
111-135
F2
118-161
EF3
136-165
F3
162-209
EF4
166-200
F4
210-261
EF5
Over 200
F5
262-317
More information about the Enhanced Fujita Scale can be found here.
Tropical Depression
A tropical depression ...
See the "Hurricane" entry for a more complete wind speed chart.
Tropical Storm
A tropical storm ...
See the "Hurricane" entry for a more complete wind speed chart.
Tropical Wave
A tropical wave ...
See the "Hurricane" entry for a more complete wind speed chart.
