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118 articles on 14 shelves, every word of them readable here. No account, no paywall, and no trip to somebody else’s website to finish the paragraph.
7 articles
How the air is built, what holds it up, and where the energy that moves it comes from.
Air Pressure
The scientific unit of pressure is the Pascal (Pa), named after Blaise Pascal (1623-1662). One pascal equals 0.01 millibar or 0.00001 bar. Meteorology has used the millibar for air pressure since 1929.
7 min read
Layers of the Atmosphere
The envelope of gas surrounding the Earth changes from the ground up. Five distinct layers are identified by temperature, composition, movement and density.
3 min read
Precipitation
In order for precipitation (rain, snow, hail, etc. to form, particularly over a large area, several ingredients are necessary. First, there must be a source of moisture. The primary moisture sources in the U.S.
6 min read
The Atmosphere
The articles on these shelves come from NOAA’s National Weather Service JetStream, a work of the U.S. federal government and therefore in the public domain (17 U.S.C. § 105). They are reproduced here in full, unaltered in substance, so that nobody has to leave to read them. Each one links back to its original. StormSync Academy is not affiliated with NOAA or the National Weather Service.
The atmosphere surrounds the Earth and holds the air we breathe; it protects us from outer space; and holds moisture (clouds), gases, and tiny particles.
2 min read
6 articles
Reading the sky: how cloud forms, why it takes the shapes it does, and what each one is telling you.
Clouds
Clouds are the visible aggregate of minute particles of water and/or ice that form when water vapor condenses in the atmosphere.
1 min read
How Clouds Form
Water is always present in Earth’s atmosphere in some form. However, water molecules on their own are too small to bond together in the formation of cloud droplets.
2 min read
NWS Cloud Chart
Prior to the availability of high-resolution satellite images, a weather observer would identify the types of clouds present and estimate their height as part of the weather observation.
3 min read
Ten Basic Clouds
John "Dr. Lightning" Jensenius, retired NWS Meteorologist, created a PDF "Cloud Book" called Clouds Outside my Window.
6 min read
The Color of Clouds
The color of a cloud depends primarily upon the color of the light it receives. The Earth's natural source of light is the Sun which provides white light.
5 min read
The Four Core Types of Clouds
Cirro-form The Latin word "cirro" means curl of hair. Composed of ice crystals, cirro-form clouds are whitish and hair-like.
3 min read
9 articles
The planetary-scale machinery — circulation cells, jet streams, climate zones and El Nino.
Climate Zones
The climate is the reoccurring average weather found in any particular place, measured over 30 year intervals.
2 min read
Climate vs. Weather
Climate and weather both describe phenomena in the Earth’s atmosphere, but the basic difference between them is time.
3 min read
Effects of ENSO in the Pacific
Normally, sea surface temperature is about 14°F (8°C) higher in the Western Pacific than the waters off South America.
2 min read
El Niño/Southern Oscillation (ENSO)
One of the most prominent aspects of our weather and climate is its variability.
3 min read
Global Atmospheric Circulations
Global Atmospheric Circulation is the movement of air around the planet. It explains how thermal energy and storm systems move over the Earth's surface.
3 min read
Global Weather
Variations in the Earth’s surface (such as water, ice, mountains, forests, bare rock, etc. absorb or reflect this heat energy differently.
1 min read
Inter-Tropical Convergence Zone
The Inter-Tropical Convergence Zone (ITCZ) appears as a band of clouds consisting of showers and occasional thunderstorms that encircles the globe near the equator.
4 min read
The Jet Stream
The strength of the wind increases toward the core of the jet stream. It also does not reside at any one particular height but can extend across hundreds of mile wide and 1,000s of feet in height.
5 min read
Weather Impacts of ENSO
As the position of the warm water along the equator shifts back and forth across the Pacific Ocean, the region with the greatest evaporation of water into the atmosphere also shifts with it.
3 min read
10 articles
The other half of the weather system: currents, waves, tides, sea breezes and the marine layer.
Layers of the Ocean
Epipelagic Zone This surface layer is also called the sunlight zone and extends from the surface to 200 meters (660 feet). It is in this zone that most of the visible light exists.
3 min read
Ocean Circulations
In January 1992, a container ship near the International Date Line, headed to Tacoma, Washington, from Hong Kong, lost 12 containers during severe storm conditions.
3 min read
Rip Current Safety
National Weather Service and National Sea Grant Program, in partnership with the United States Lifesaving Association, are working together to raise awareness about the dangers of rip currents and how to protect yourself.
2 min read
Rip Currents
Rip currents are powerful, channeled currents of water flowing away from shore. They typically extend from the shoreline, through the surf zone, and past the line of breaking waves.
2 min read
Sea Water
One of the most well known qualities of the ocean is that it is salty. The two most common elements in sea water, after oxygen and hydrogen, are sodium and chloride.
3 min read
The Marine Layer
Strong downward motion from upper level high pressure squashes the marine layer and keeps is confined to the coast. Inland temperatures are high.
1 min read
The Ocean
Understanding the ocean and its relationship to weather is critical as more than half of the world's population lives within 60 miles (100 km) of the ocean.
1 min read
The Sea Breeze
The ocean's ability to absorb and store energy from the sun is huge. This is due to.
5 min read
Tides
Tides are another type of wave motion – a change in the ocean water level that typically reaches a high and low twice a day, about six hours apart (called a semi-diurnal tide).
5 min read
Waves
The wind not only produces currents, it creates waves. As wind blows across the smooth water surface, the friction or drag between the air and the water tends to stretch the surface.
5 min read
15 articles
Ingredients, life cycle and hazards — hail, damaging wind, flash flooding, tornadoes and derechos.
Bow Echoes
Derechos typically are associated with bands of showers or thunderstorms that assume a curved or bowed shape.
3 min read
Derechos
A derecho is a widespread, long-lived windstorm associated with a band of rapidly moving showers or thunderstorms.
1 min read
Derechos: Keeping Yourself Safe
The National Weather Service does not issue "derecho warnings" as, by their definition, derechos are wind events produce by severe thunderstorms.
3 min read
Ingredients for a Thunderstorm
All thunderstorms require three ingredients for their formation.
3 min read
Life Cycle of a Thunderstorm
The building block of all thunderstorms is the thunderstorm cell. The thunderstorm cell has a distinct life-cycle that lasts about 30 minutes.
1 min read
Notable Derechos
The following are a few of the more historic derechos over the past 2 decades.
5 min read
Staying Ahead of the Storms
Severe weather rarely happens without any warning.
8 min read
Thunderstorm Hazards - Damaging Wind
While wind damage from thunderstorms often makes people think of tornadoes, damaging “straight-line” winds are actually much more common than tornadoes.
5 min read
Thunderstorm Hazards - Flash Floods
More deaths occur from flooding than any other weather hazard except heat. Why? Because most people fail to realize the power of water.
3 min read
Thunderstorm Hazards - Hail
Hail is precipitation that is formed when updrafts in thunderstorms carry raindrops upward into extremely cold areas of the atmosphere.
3 min read
Thunderstorm Hazards - Tornadoes
Tornadoes have often been said to sound like a thousand locomotives or planes. If a tornado threatens, follow these safety rules.
7 min read
Thunderstorms
The figure above shows the average number of thunderstorm days each year throughout the U.S. (The graphic defines a day of thunderstorms as two lightning flashes within a 10 nmi (18.5 km) radius).
1 min read
Types of Derechos
Derechos can be categorized into three main types: serial, progressive, and hybrid. These categories are largely based on the overall organization and behavior of the thunderstorms producing the derecho.
2 min read
Types of Thunderstorms
Also called a "pulse" thunderstorm, the ordinary cell consists of a one-time updraft and one-time downdraft.
6 min read
Where and When do Derechos Occur
All the weather we experience at ground level is governed by the weather pattern in the atmosphere, and derechos are no different.
3 min read
6 articles
How a flash is built, what thunder actually is, and the safety rules that come out of both.
Frequently Asked Questions
Technically, there is none. In general, the term "thundershower" tends to denote a fairly weak storm with light to moderate rainfall and low levels of lightning activity.
5 min read
How Lightning is Created
The conditions needed to produce lightning have been known for some time. However, exactly how lightning forms has never been verified, so there is room for debate.
4 min read
Lightning
Lightning has been seen in volcanic eruptions, extremely intense forest fires, surface nuclear detonations, heavy snowstorms, and large hurricanes. However, it is most often seen in thunderstorms.
1 min read
Lightning Safety
If you see lightning, count the number of seconds until you hear thunder. Divide the number of seconds by five to get the distance in miles (divide by 3 for kilometers) to the lightning strike or bolt.
8 min read
The Positive and Negative Side of Lightning
The previous section describes what is called "negative lightning" because it is the transfer of negative charge from the cloud to the ground.
3 min read
The Sound of Thunder
Thunder is the acoustic shock wave resulting from the extreme heat generated by a lightning flash. It is produced the same way regardless of whether lightning is positive or negative.
2 min read
8 articles
Structure, classification, naming, hazards and the forecast products the Hurricane Center issues.
Cyclone Hazards & Safety
Taping windows provides absolutely no protection. It is a myth that taping windows will prevent them from breaking when impacted by windborne debris.
10 min read
Hurricane Damage Potential
The Saffir-Simpson Hurricane Wind Scale is a 1 to 5 categorization based on the hurricane's intensity at the indicated time.
3 min read
National Hurricane Center Tropical Cyclone Forecast/Advisory
The Tropical Cyclone Forecast/Advisory is issued when meteorological data indicates that a tropical or subtropical cyclone has formed.
2 min read
Tropical Cyclone Classification
Tropical cyclones with an organized system of clouds, and thunderstorms with a defined circulation and maximum sustained winds of 38 mph (61 km/h) or less, are called "tropical depressions".
8 min read
Tropical Cyclone Introduction
One rare exception to the lack of tropical cyclones near the equator was Typhoon Vamei which former near Singapore on December 27, 2001.
6 min read
Tropical Cyclone Names
2005 was the most active Atlantic hurricane season in recorded history. There were a record total of 29 tropical storms and one subtropical storm.
8 min read
Tropical Cyclone Structure
The main parts of a tropical cyclone are the rainbands, the eye, and the eyewall.
5 min read
Tropical Weather Systems
The tropics refers to the region of Earth around the equator. The weather here is, on average, hot and humid.
1 min read
6 articles
What the WSR-88D transmits, what comes back, and how to read reflectivity and velocity honestly.
Doppler Radar
The Next Generation Weather Radar system is a network of 160 high resolution Doppler radars around the world, operated jointly by the National Weather Service, Federal Aviation Administration, and the Department of Defense.
1 min read
How radar works
All modern weather radars are Doppler radars. Therefore, the old-time radar sweeping line is no longer applicable.
5 min read
Radar Images: Precipitation Estimation
One of the more widely used products that the WSR-88D radars produce are the precipitation estimation products.
2 min read
Radar Images: Reflectivity
The dBZ values equate to approximate rainfall rates indicated below.
8 min read
Radar Images: Velocity
Velocity is the second of the three base products that are produced by pulsed Doppler radars and is used to indicate the motion and speed of targets.
10 min read
Volume Coverage Patterns (VCP)
In order to scan as much of the atmosphere as possible, the WSR-88D employs a volumetric scanning strategy in which the antenna not only scans near the ground, but raises through multiple elevation angles to obtain data in the vertical.
8 min read
3 articles
The electromagnetic spectrum, the atmospheric window, and the satellites that watch through it.
Electromagnetic waves
Electromagnetic waves are a form of radiation that travel though the universe. They are formed when an electric field (Fig. 1 red arrows) couples with a magnetic field (Fig.1 blue arrows).
2 min read
The Atmospheric Window
The first section in JetStream, The Atmosphere, provided information about the Earth-Atmosphere energy balance.
1 min read
Weather Satellites
The world's first meteorological satellite was launched from Cape Canaveral on April 1, 1960.
5 min read
7 articles
Radiosondes, parcel theory, stability and the Skew-T Log-P diagram, worked through.
Parcel Theory
“Warm air rises” is common knowledge. While it is correctly understood that warm air rises because it is lighter than cooler air, the density difference alone doesn’t explain why it rises.
3 min read
Radiosondes
In order to understand the dynamic processes that result in the weather we experience, we need to know what is happening through the entire atmosphere.
3 min read
Skew-T Examples
Radiosonde observations provide the condition of the atmosphere above the launch site (typically within 25 miles/40 km) at the time of launch.
3 min read
Skew-T Log-P Diagrams
Once the radiosonde observation is plotted, the Skew-T will show the temperature, dew point, and wind speed/direction.
4 min read
Skew-T Plots
As radiosonde balloons ascend, they record the temperature and relative humidity at certain prescribed pressure levels (called the mandatory levels) and anytime a significant change occurs in the temperature, humidity, or wind.
2 min read
Stability and Instability
Parcel stability, explained with a bowl and a ball: why some air returns to where it started and some keeps going.
2 min read
Upper Air
The term "upper air" refers to the earth's atmosphere above about 5,000 feet (1,500 meters). It is from the upper air that we get our rain and drought, wind and calm, and heat and cold at the Earth's surface.
1 min read
12 articles
Constant-pressure charts level by level, wave patterns, thickness, and what the models do with them.
Basic Wave Patterns
The wave patterns that recur on upper-level charts, and what each one means for the weather underneath it.
4 min read
Common Features of Constant Pressure Charts
One thing all upper air charts have in common are the height lines (contours) themselves. These lines represent the altitude (in meters) of various significant pressure levels.
3 min read
Constant Pressure Charts: 200 mb
The air pressure everywhere on this constant pressure chart is 200 millibars. The lines represent the height, in meters, of the altitude of 200 mb.
1 min read
Constant Pressure Charts: 300 mb
The air pressure everywhere on this map is 300 millibars. The lines represent the height, in meters, of the altitude where the air pressure is 300 mb.
2 min read
Constant Pressure Charts: 500 mb
The 500 millibar constant pressure charts is the mainstay of the upper air charts. If meteorologists could only look at one chart, the 500 mb level chart would, by far, be the top choice.
2 min read
Constant Pressure Charts: 700 mb
700 mb is considered by many to be the top of the lower atmosphere.
2 min read
Constant Pressure Charts: 850 mb
This pressure level is near an elevation of 5,000 feet, although it ranges from 3,800 feet (1,170 meters) to 5,200 feet (1,590 meters).
1 min read
Constant Pressure Charts: Thickness
While typically plotted on surface charts, the thickness contours are derived from constant pressure charts. Thickness is the measurement of the distance (in meters) between any two constant pressure surfaces.
3 min read
Constant Pressure vs. Constant Elevation
Both at the surface and in the upper atmosphere, meteorologist constantly refer to "high" and "low" pressure systems. However, we look at them from two different perspectives.
2 min read
Longwaves and Shortwaves
The hemispheric weather patterns are governed by mid-latitude (23.5°N/S to 66.5°N/S) westerly winds which move in large wavy patterns.
4 min read
Upper Air Charts
Any time there is a rapid change in a particular weather element, we will say the "gradient" is large. It is near these large gradients where the weather is most active.
1 min read
Weather Models
The motion of air in the atmosphere is extremely complicated. From large-scale synoptic motion we see high and low pressure systems at the surface and ridges and troughs in the air aloft.
4 min read
9 articles
Air masses, fronts, wind, the station plot, and reading a surface map the way a forecaster does.
Air Masses
An air mass is a large body of air with generally uniform temperature and humidity. The area over which an air mass originates is what provides its characteristics.
4 min read
Heat Index
The highest dew points, and therefore the highest heat indices, are usually found near warm bodies of water.
5 min read
How to read Surface Weather Maps
Weather maps come in a myriad of styles, each providing different levels of information. However, there are some common features typically found in all of these images.
6 min read
Norwegian Cyclone Model
If you track low-pressure areas and temperature gradients where fronts form, especially in winter, you will often notice that these systems undergo a particular cycle.
2 min read
Origin of Wind
Wind is simply air in motion. Usually in meteorology, when we are talking about the wind it is the horizontal speed and direction we are concerned about.
4 min read
Surface Weather Plots, Decoded
Some surface maps show station weather plots – a collection of symbols depicting the weather occurring at a weather observing station at a specific time.
4 min read
Types of Weather Phenomena
Precipitation is any form of water particle, whether liquid or solid, that falls from the atmosphere and reaches the ground. The different types of precipitation are.
4 min read
Wind Chill
Fact: Although solar radiation is less direct in the winter, it is still strong enough to cause damage to skin. Also, snow cover reflects skin-damaging radiation, thereby magnifying the danger.
7 min read
Z-Time (Coordinated Universal Time)
All aspects of meteorology are based upon a world-wide 24-hour clock called Zulu time (Z), more commonly called Coordinated Universal Time (UTC).
7 min read
13 articles
Generation, propagation, inundation, detection and warning — and what a community does about it.
Detection, Warning, and Forecasting
A tsunami warning center is a vital part of a tsunami warning system. They have been established around the world with the primary goal of saving lives.
5 min read
Historical Context
We live on a geologically active planet where earthquakes and tsunamis have always occurred, within all oceans and impacting all continents.
3 min read
Tsunami Dangers
Tsunamis can easily knock people off their feet and float vehicles...
3 min read
Tsunami Generation: Earthquakes
Earth's surface is made up of tectonic plates, which are large slabs of solid rock that fit together like puzzle pieces. These plates meet at plate boundaries and are in constant motion.
3 min read
Tsunami Generation: Landslides
Relating to tsunami generation, "landslide" is a general term that describes a number of types of ground movement, including rock falls, slope failures, debris flows, and slumps.
2 min read
Tsunami Generation: Volcanoes
Tsunamis generated by volcanoes, both above and below water, are infrequent. Additionally, a volcano must be near the coast or not far below the sea surface to generate a significant tsunami.
1 min read
Tsunami Generation: Weather
Air pressure disturbances often associated with fast-moving weather systems, like squall lines, can also generate tsunamis.
2 min read
Tsunami Inundation
The amount of time it takes a tsunami to reach a coast depends on the location of the source of the tsunami relative to where it may strike land. Therefore, tsunamis are often referred to as local or distant.
3 min read
Tsunami Locations
Tsunamis can be generated in all of the world's oceans, inland seas, and in any large body of water. They have caused damage and deaths in coastal areas all around the world and can strike any coast.
3 min read
Tsunami Preparedness: Communities
Of all Earth's natural hazards, tsunamis are among the most infrequent. Major tsunamis do not happen often, but when they do, they can have a significant impact on life and property.
3 min read
Tsunami Preparedness: Individuals
Tsunami warning centers and coastal communities play critical roles in protecting the public from tsunamis, but ultimately it is up to YOU to know how to protect yourself and your loved ones.
4 min read
Tsunami Propagation
Tsunami speed can be computed by taking the square root of the product of the acceleration of gravity, which is 32.2 feet (9.8 meters) per second squared, and water depth.
1 min read
Tsunamis
The word "tsunami," pronounced (soo-NAH-mee) comes from the Japanese characters meaning "harbor wave."
1 min read
7 articles
Who issues the forecast: the offices, the centers, and how somebody gets a job in them.
Center Weather Service Units
The Center Weather Service Units monitor and provide weather forecasts and advisories to the nation's 21 Air Route Traffic Control Centers (ARTCC).
1 min read
Educational Requirements for Careers in the National Weather Service
Interested in a career with the National Weather Service (NWS) or other agency in the federal government?
3 min read
NWS Weather Forecast Offices
Local NWS Weather Forecast Offices monitor local weather around the clock.
2 min read
National & Regional Offices
The National Weather Service is comprised of a national headquarters and six regional offices.
1 min read
National Centers for Environmental Prediction
The National Centers for Environmental Prediction (NCEP) is comprised of nine distinct Centers.
2 min read
National Weather Service
"to provide for taking meteorological observations at the military stations in the interior of the continent and at other points in the States and Territories...and for giving notice on the northern (Great) Lakes and on the seacoast by…
2 min read
River Forecast Centers
Hydrology is the science of water on Earth – where it occurs and how it circulates through the hydrologic cycle as precipitation, runoff, evaporation, and groundwater.
7 min read