Complete topics list

Chapter

The Creation of Weather

The Source of Weather

The Sun

The Sun, apparently active for the past 4.6 billion years, is responsible not only for the existence of weather, but for the mere existence of life on Earth. The main [...]

Structure of the Sun

The sun is structured in five zones or layers, which ordered from in-to-out, are: The core – it has an estimated temperature of 27 million Fahrenheit degrees (14 million Celsius degrees) [...]

Radiation

Radiation is an important factor in the process of turning solar energy into weather. Generally speaking, it is defined as energy that is transmitted in the form of rays, waves [...]

Solar Wind

Solar wind is a stream of particles (mostly high-energy protons) which are ejected from the upper atmosphere of the Sun and move radially from it. The Sun's atmosphere is a [...]

The Earth

In the Solar System, the Earth is the third planet of eight considering its distance from the Sun. It is one of the smallest, with a radius of about 3.945 [...]

Structure of the Earth

The story starts five billion years ago, when the immense amount of caloric energy generated by a high-velocity bombardment of meteorites and comets melted the entire planet. Different processes led to [...]

Rotation

Earth's rotation can be defined as the rotatory motion of the Earth with respect to its center of mass. While traveling around the Sun, our planet is spinning west to [...]

Revolution

Revolution is defined as the rotatory motion of a celestial body around another. The complete revolution of the Earth’s orbit around the sun takes 365 ¼ days, which explains the [...]

Tilt

The Earth’s tilt is the angle at which the Earth’s axis is leaning with respect to the Sun. The Earth’s axis is not perpendicular to its orbital plane: it [...]

Magnetic Field

It is defined as a magnetic shell that surrounds the planet. It is asymmetrically shaped, as it is delimited by the pressure of the solar wind, in the direction of [...]

Van Allen Belts

The Van Allen Belts were discovered in the late 1950s, and surround the Earth representing two regions of a particularly high concentration of charged particles. The inner belt occupies a [...]

The Atmosphere

The atmosphere is the gaseous area –the whole mass of aeriform fluid- that surrounds the planet, which controls the climate and ultimately determines the quality of life on Earth.

Where action takes place...

The atmosphere is made of: oxygen ozone water vapor nitrogen noble gases visible and non visible solid particles Oxygen and nitrogen constitute about 99 percent of it. Water vapor in humid regions can occupy up to 3% [...]

Depth and Structure

The atmosphere is structured in five concentric spherical thermal layers or "-spheres", separated by narrow transition zones or "-pauses-". The upper boundary at which gases merge into space lies at [...]

Absorption and Reflection

Absorption and reflection are two of the processes that occur to solar radiation as it passes through the atmosphere; solar radiation is modified due to its interaction with gases and [...]

The Weather Builders

Moisture, Pressure & Temperature Control the Air

These three physical properties, pressure, temperature and humidity, are basic weather builders, determining by themselves and by their interaction how air is going to behave. Changes in moisture, pressure and [...]

Atmospheric pressure

The atmospheric pressure is the force exerted on any point of Earth’s surface by the weight of the column of air above it. Air molecules have volume, weight, mass and [...]

Temperature

When heat enters a substance, energy comes into it as well. That energy can be used to increase the rate of movement (kinetic energy) of the molecules, which would cause [...]

Humidity

Life in the planet is possible because of the presence of water. Air contains moisture, that is, water vapor, which absorbs energy very well and prevents Earth’s heat from escaping [...]

Air Masses (upper level)

Knowing about air masses provides interesting information about the kind of weather to expect. An air mass can be defined as a large body of air that has relatively uniform characteristics, [...]

Types of Air Masses

According to the source region, air masses are classified as: P – Polar Air Masses, originated in polar latitudes, located pole-ward of 60 degrees north and south. T – Tropical Air Masses, [...]

Pressure Systems (upper level)

Air pressure is a measure (in millibars) of the force exerted by air on every point of Earth’s surface. The concept of pressure system refers to a region of the [...]

Basic concepts

Pressure system: “individual cyclonic-scale feature of atmospheric circulation commonly used to denote either a high or a low, less commonly a ridge or trough”. Cyclone - also named as depression, or [...]

Internal dynamic of highs and lows

Air rotates around highs in an anticyclonic (clockwise in the Northern Hemisphere) direction while spiraling outward from the high pressure center. Such spreading out of the air is known as [...]

Semipermanent Highs and Lows

They are areas of high pressure (anticyclones) and low pressure (cyclones) that tend to persist at a particular latitude belt throughout the year, averaged over long periods of time. Semi-permanent [...]

Creation of fronts

A front is the relatively sudden transition zone between air masses. Fronts are not permanent features; they form and intensify in a process known as frontogenesis. The arrival of a new [...]

Troughs & Ridges

A ridge is an axis or line of high atmospheric pressure, depicted on a weather map as a rise in an isobar; a system of nearly parallel isobars, approximately u-shaped, [...]

Airflow Patterns (general circulation of winds aloft)

The air moving above the rotating Earth is called wind. There are surface winds and "planetary winds aloft", the latter of which is part of the Earth's general circulation of [...]

Circulation Cells

Back in the 1680s, Edmond Halley (1656-1742), discovered the key element of the planet’s global circulation: warm air near the equator rises, it flows out toward the poles at high [...]

Coriolis Force

It is an apparent force, due to the rotation of the Earth, which acts normal to, and to the right of the velocity of a moving particle in the Northern [...]

Prevailing Westerlies

The Westerlies are global-scale, dominant mid-latitude winds that blow from the subtropical high pressure belt toward the polar front. They come from the west, which characterize the mid-latitudes both north [...]

Jet Stream

The jet stream is a flat tubular quasi-horizontal current of air, generally near the tropopause, whose axis is along a line of maximum speed and which is characterized by strong [...]

Ocean Currents

An ocean current can be defined as a horizontal movement of seawater at the ocean's surface. Ocean currents are driven by the circulation of wind above surface waters. The surface layer [...]

The Elements

Precipitation

Precipitation is any form of water falling from the atmosphere to the Earth’s surface. It is the process by which atmospheric water becomes surface, or subsurface water. The term "precipitation" [...]

How do droplets form?

Water is available on the Earth in the following three forms: vapor, liquid and solid. A phase change (water changing from one state to another) is possible only if heat [...]

Formation Models of Precipitation

Most clouds do not precipitate. In fact, most water droplets in clouds have such a small size that they do not fall to the surface. There are two models, developed by [...]

Forms of precipitation

We have stated that, from a meteorological point of view, precipitation is water in some form, falling out of the air, and settling on the surface of the Earth. We [...]

Precipitation Measurement

Precipitation quantity or precipitation amount is the depth of water in any of its forms (rain, snow, etc.) that has fallen over a given period; it is measured in a [...]

Cloud Seeding

Cloud seeding is a form of weather modification. It can be used to disperse fog, suppress hail, or control winds, but it is most often used to increase precipitation. Cloud seeding [...]

Clouds

A cloud is a hydrometeor, seen as an aggregate of minute particles of liquid water or ice, or of both, suspended in the free air, usually not touching the ground. [...]

Formation of clouds

Clouds are created by condensation or deposition of water above the Earth's surface. In general, any air mass that becomes saturated (relative humidity becomes 100%) develops clouds. Saturation can occur due to: cooling moisture gain (from Earth´s surface [...]

Classification of clouds

Clouds are classified according to appearance and height. Based on appearance, there are two major types: Clouds of vertical development, cumuliform, formed by the condensation of rising unstable air –heaped clouds-. Clouds that [...]

Winds (mainly surface)

Wind: air in motion relative to the surface of the Earth. Vertical components of atmospheric motion are relatively small, so the term is used to denote almost exclusively the horizontal [...]

Formation of winds

Different forces acting in the atmosphere are involved in wind formation: Gravity - makes cold dense air to sink and when it impacts on the ground, it spreads horizontally. Pressure - differences [...]

Types of winds

There are different types of winds: Light air: Light air in the Beaufort wind scale is a wind with a speed from 1 to 3 knots (1 to 3 MPH or 2 [...]

Measurements

Beaufort wind scale: - A system of estimating and reporting wind speeds using a numerical scale ranging from 0 (calm) to 12 (hurricane). - The purpose for this system was to allow [...]

The Effects (mainly Surface Weather)

Fronts

Fronts are the narrow zone of division between air masses of differing characteristics (temperature and humidity). They form where two large air masses collide at the Earth's surface. Two air masses [...]

Types of fronts

Cold front: Occurs when a dense cold air mass moves towards an area of warmer weather; cold air displaces lighter warmer air, pushing it upward; the front is the leading edge [...]

Highs & Lows

High: an area of the atmosphere where the pressure is high relative to that in the surrounding region at the same level. It is always associated with anti-cyclonic circulation (clockwise [...]

Air flow and circulation

The pressure is high at the surface where air is slowly descending. In fact, a high is an area of sinking air. As air descends, it warms, which inhibits the [...]

Storm Track

It is the path followed by a cyclonic disturbance, for example, a center of low atmospheric pressure, a severe thunderstorm, or a tornado. It also roughly corresponds to the mean trajectory [...]

Storms

Storms are organized areas of disturbed weather, especially those affecting the Earth's surface, implying inclement and possibly destructive weather. They can be considered: As a complex of pressure, wind, clouds, precipitation, etc. [...]

Types of storms

Thunderstorm A thunderstorm is a local storm, invariably produced by a cumulonimbus cloud and always accompanied by lightning and thunder, usually with strong gusts of wind, heavy rain, and sometimes with [...]

Tropical Cyclones

It is any cyclone of non frontal synoptic scale, originated over tropical or subtropical waters, that presents an organized convection and a cyclonic circulation characterized by surface winds. Being one of [...]

Favorable conditions for formation of fronts

Warm ocean waters (at least 80°F or 26.5°C). An atmosphere potentially unstable to moist convection. Thunderstorm activity. Relatively moist layers near the mid-troposphere. A minimum distance of at least 300 mi (500 km) from [...]

Characteristics of a Tropical Cyclone

The surface winds spiral inward cyclonically, becoming almost circular near the center. The cloud and rain patterns are distinctive in each storm. Spiral bands in the outer vortex. Most intense rain and winds [...]

Classification of Tropical Cyclones

Tropical disturbance: light surface winds with indications of cyclonic circulation. Tropical depression: a closed wind circulation and maximum sustained speed of 23-39 MPH (37 to 62 KPH) surface winds. Tropical storm: cyclone [...]

Hurricanes and Typhoons

A hurricane is a very severe tropical cyclone. Characteristics: A diameter of 310 miles (500 km). Winds of 75 MPH (118 KPH) or more. Winds blow drawing a large spiral around a center of [...]

Storm Surge

Rise and onshore surge of seawater as the result of the winds of a storm, and secondarily of the surface pressure drop near the storm’s center. Large crest of water, 50 [...]

Floods & Droughts

The extremes of flood and drought occur within the context of climate, a context that is both local and global. The cadence of wet and dry years is difficult to [...]

Floods - causes, types and effects

Flood is the overflowing of the normal confines of a body of water, usually a stream, or the accumulation of water over areas that are not normally submerged. During the past [...]

Droughts - causes, types and effects

Drought is a period of abnormally dry weather long enough to cause a serious hydrological imbalance. It can be defined as a deficiency of precipitation over an extended period of [...]

Related phenomena: El Niño and La Niña

These ocean-atmospheric systems responsible for noticeable cyclical changes in the temperature of water surface in the Pacific Ocean are the kind of event that can change the location of areas [...]

Celestial Phenomena

Celestial Phenomena

Near sunrise and sunset, in a clear day, the sky can adopt a particularly beautiful coloration. Virtually every color of the spectrum shows up at these times of the day [...]

Types of celestial phenomena

Different types of celestial phenomena: Rainbow Rainbows are colored, circular (or nearly circular) concentric arcs, ranging from violet to red, formed by refraction or diffraction of solar or moon light on water [...]

Chapter

The Climates of the World

Climate Changes

Future Climate

A great number of scientists that gather climate data, use computer models to simulate future climate, and not surprisingly, they do not agree on what is coming ahead. Climate change is [...]

The Ozone Hole

The Ozone Hole is a characteristic severe depletion of stratospheric ozone that occurs each spring over the Antarctic continent. Although it is known as the Ozone Hole, “hole” gives the [...]

The Greenhouse Effect

There are certain gases in the atmosphere, called greenhouse gases, which permit the income of solar radiation but restrict the outward flow of infrared radiation, storing the heat by absorbing [...]

Air pollution

Air pollution is defined as the presence of substances in the atmosphere, generally contaminants, particularly those that do not occur naturally (anthropogenic air pollution), that substantially alter or degrade the [...]

International initiatives

International Initiatives regarding Future Climate: The creation (in 1988) of the Intergovernmental Panel on Climate Change is a proof of the international concern on future climate. The reports produced by this [...]

Recording Climate Changes

Having enough and accurate information about climate in the past, and the constant changes it has been undergoing, is a real challenge for scientists, as it cannot be done directly, [...]

Recording methods

Recording climate change methods: Tree rings - In a horizontal cross section cut from a tree trunk, variable width of rings are observed; these were produced by seasonal growth. The combination [...]

Through Time & Its Reasons

Change is the only constant. It has been going on in the planet for an estimated 4.5 billion years, since its creation.

Climate Change

Climate change is any systematic change in the long-term statistics of climate elements (e.g. temperature, winds, atmospheric pressure) which is persistent over several decades or more. In a timeframe, there is a [...]

Causes of Climate Change

Ice Ages Astronomical perturbations Geological perturbations Ocean Conveyor Belt Human activities 1. Ice Ages Let’s draw an imaginary time line and try to situate the different events of the planet’s history, from more than 120 million [...]

Climate Zones

Climate Zones around the World

Climatic classification is the division of the Earth's climates into a worldwide system of contiguous regions; each one of them is characterized by a relative homogeneity of the climatic elements, [...]

Classification of climate zones

Tropical Humid Climates (A): Location: on or near the Equator, as the Amazon Basin in South America, central Africa and Southeast Asia. Classification Criteria: 1) the mean temperature of the coldest [...]

Regions

While climate classification can tell us what is expected in a given location, averaged over a lengthy period of time, the following flashes suggest how the weather evolves in a [...]

Difference between Climate & Weather

Weather and climate are not the same, and they should not be confused. Definition of Weather: state or condition of the atmosphere at a given place at a particular time, as [...]

Geographical & Seasonal Variances

Geographical & Seasonal Variances

In the evaluation of natural climate variability (geographical and seasonal) some factors stand out because of their impact on global climate: “El Niño” and its counterpart “La Niña”, Monsoon circulations [...]

El Niño and La Niña

Although its history goes back at least to the year 1500, it was not until the late 90s when most people around the world had heard about the existence of [...]

Monsoons

Monsoon: seasonal wind, actually a global scale seasonal thermal direct circulation caused by the configuration of land and ocean, in southern Asia and some other locations in the world. This winds, [...]

Ocean Currents

Ocean current: movement of ocean water characterized by regularity, either of a cyclical nature or, more commonly, a continuous stream flowing along a definable path. The major ocean currents are [...]

Chapter

Weather Forecasting

Weather Forecasting

Areas of Forecasting

Every morning, millions of people around the world, are curious about what the weather will be like that day. Depending on where you live and what you do, the weather [...]

Most common areas of weather forecasting

The most common areas of weather forecasting are: Agricultural Forecasts: For a farmer, the information included in a regular forecast (temperature, humidity, cloud cover, probability of precipitation) is not enough. Apart from [...]

Data Gathering

Meteorologists use a variety of tools to help them gather information about weather and climate. Some of these tools allow meteorologists to gather data about what is happening near Earth's [...]

What is a weather forecast?

A Weather Forecast is a deterministic or probabilistic statement of expected meteorological conditions for a specific period and for a specific area or portion of air space. It is [...]

Instruments

There are a few properties of the atmosphere which are key elements for weather determination: temperature, humidity and air pressure. A set of tools or instruments have been created -some [...]

Distribution

The demand for customized forecasts has been growing steadily. Commercial meteorological companies offer a wide variety of tailored forecasts for specific applications. Among these special applications are forecasts produced for [...]

Newspapers

Weather information started to be available for the masses when in the late 1800s, the New York Times began publishing a small section that summarized the previous day’s weather and [...]

Radio

In 1922, the first radio broadcasted weather forecast went on air, transmitted by the BBC; short time after, hundreds of radios around the world were broadcasting weather information. Radio stations are [...]

Television

With pioneer attempts in 1936 and 1941, television exploded in the 1950s, and weather forecasts became part of the daily broadcast. The first “weatherperson” was a cartoon, and then this [...]

Internet

The Internet is a mechanism for world-wide information dissemination, in every term. It presents both a challenge and opportunity for weather forecast companies. It has limitations: It is not a good medium [...]

Cell Phones

The latest technological advances allowed the existence of this new source of weather information distribution; there are many companies around the world offering this service on your cell phone. This [...]

Interpretation

The elaboration of a weather forecast is no easy task. It is quite obvious that the atmosphere is highly complex place, a space lacking in linear behavior. The latest technological [...]

Forecast elaboration process

The elaboration of a weather forecast is no easy task. It is quite obvious that the atmosphere is a highly complex place, a space lacking in linear behavior. Forecast elaboration process: Weather [...]

A bit of history...

The bases for modern weather prediction were founded by the scientists from late 1600s into the 1800s. Among others, Newton and Boyle announced the basic rules that control the expansion [...]

Supercomputers

Practically every country in the world has its own national weather service, but not many have full-blown global weather models, focused at a single location where supercomputers are present. Supercomputers [...]

Basic forecasted elements

Temperature: the quantity measured by a thermometer, expressed in degrees, Celsius, Kelvin or Fahrenheit, according to the scale. In a weather forecast, low and high temperatures are indicated. In a [...]

Short and Long Range forecasts

There is a spectrum of outlooks that extend from one or two hours to a year or more ahead. The most common types are: nowcasts, short, medium and long-range forecasts. Nowcasts [...]

Chaos Theory and Butterfly Effect

Edward Norton Lorenz, an American pioneer in the chaos theory says that every improvement in the understanding and processing of meteorological data can make weather forecast more accurate, but only [...]

Dangerous weather

One of the main responsibilities of the National Weather Services around the world is to warn the public about hazardous weather conditions, such as floods, severe thunderstorms, tornadoes, snow and [...]

Maps & Symbols

A weather map is a graphical representation of relevant meteorological information. The weather map that we see on a newspaper or on TV is quite different from a technical synoptic [...]

Weather Maps

It is considered a weather map, any graphical display of the distribution of meteorological data over a given area. Also called synoptic charts or weather charts, they are geographical maps on [...]

Weather Icons and Symbols

Symbols and icons are not the same. On a weather map we may find both coexisting. An icon is a sign which refers to the object that it denotes merely by [...]

How to read a weather map...

The features that appear on a typical weather map (which represents surface weather) are: High and Low Pressure Areas - designated by a capital and large blue H or red L, [...]

Chapter

Weather Trivia

History of Meteorology

History of Meteorology

Humankind has been always fascinated by celestial phenomena, and observed them since the beginning of times. Meteorology, as a “branch of knowledge” started virtually when early men look up to [...]

Chronological review

From those beginning of orally transmitted knowledge to the latest satellite images, many fundamental events took place. Here there are many of the most transcendent ones, in a chronological order: C1060 [...]

Weather Extremes

Major Disasters

Extremes in weather such as floods, droughts, storms and other extreme weather events are part of the natural variability in climate. Extreme weather: weather phenomena that are at the extremes of [...]

World Weather Disasters

Hereunder, there is a quite vast list of world weather disasters, according to different criteria, being the main three the number of fatalities, economical losses and peculiarity of the phenomena [...]

Records

Weather extremes are the highest and, in some cases, the lowest value of a climatic element (typically temperature and precipitation) observed during a given interval or during a given month [...]

World Weather Records

Highest temperature: 136º F (57.8º C), El Azizia, Libya, on Sept. 13, 1922. Highest average annual mean temperature: 94º F (34.4º C), in Dallol, Ethiopia. Hottest summer average in Western Hemisphere: 98º [...]

Weather Safety & Health

Illnesses related to weather:

There are a number of illnesses whose appearance and development are related to weather elements. Colds, allergies, heat and cold-related illnesses as well as S.A.D. and skin cancer are some [...]

Colds and Influenza Virus

Colds and the influenza virus (commonly named as flu) are usually related to autumn and winter; they are linked to cold weather or to sudden temperature changes. These are two [...]

Allergies

Allergies - Symptoms of seasonal allergic rhinitis: sneezing watery eyes runny noses congestion and itchiness in the nose, roof of mouth, throat, eyes and ears. Allergic rhinitis or hay fever, are triggered by allergens, substances that [...]

Heat-related illnesses

Heat-Related Illnesses- Extreme heat can kill by taxing the human body beyond its abilities to shed heat by circulation and sweating. When this happens, heat-related illness may develop. These include: Heat [...]

Cold-related illnesses

Cold related illnesses: When exposed to cold temperatures or a cool, damp environment for prolonged periods, your body's control mechanisms may fail to keep your body temperature normal. Cold weather can [...]

Skin cancer and other UV related disorders

Skin cancer: It is the most common form of human cancer. Since the 80's, we have become aware of the health threats posed by ozone depletion, which decreases our atmosphere's natural protection [...]

Seasonal Affective Disorder

The end of long sunny days, bright colors and green leaves, the arrival of cold blasts of wind and snow produce in some people depressing thoughts, which are a possible [...]

Precautions to take during:

In hazardous weather conditions, taking precautions and safety actions is key to prevent people from dying or getting seriously hurt. The first safety tip is not to underestimate the power [...]

In case of thunderstorm and lightning

You should... Monitor the radio, listening for severe thunderstorm watches and warnings. Go to a small interior room on the lowest floor of your residence, school or office. Stay away from windows. If time [...]

In case of tornadoes...

At home: You should have an identified place to take shelter (underground area –basement- otherwise, an interior room). Stay away from windows. You should have an emergency alert weather radio, if available in [...]

In case of Hurricanes...

You MUST stay away from the ocean during a hurricane warning or hurricane, so move on to land. If you live in an evacuation area, you should know your home’s susceptibility [...]

In case of Floods...

Stay away from areas subject to flooding: streams, creeks, and low areas. In urban areas, stay away from underpasses. Do not attempt to cross flooded areas in a car or truck: If [...]

In case of Rip Current...

Learn how to swim and know your ability to swim in ocean waters and strong currents. If possible, always swim at beaches staffed by lifeguards or beach patrols and heed their [...]

In case of Snowstorms...

Prepare a Winter Storm Plan: Have extra blankets at hand. Ensure that each member of your household has a warm coat, gloves or mittens, hat, and water-resistant boots. Assemble a Disaster Supplies Kit [...]

In case of Avalanche...

Learn to recognize avalanche terrain and heed avalanche warnings. Avoid these areas. Prepare to travel in a group at all times. Every member needs proper equipment including a checked transceiver, shovel [...]

Weather Tidbits

Non-Scientific Ways to predict Weather

People have been building their knowledge about weather since the beginning of time, basically through observation, until the arrival of modern technology. Scientific investigation allowed the production of forecasts with a [...]

Animal behavior

Animals respond to changes in the atmosphere (e.g.: a pressure drop), which take place before a change in weather occurs (e.g.: rain). Ants - when they move to higher ground, it [...]

Sayings and Proverbs

When looking at weather proverbs, once again we should keep in mind that they not based on scientific studies, but on someone´s observations; they can eventually have local value. For ages, [...]

Farmer's Almanac

The Farmer’s Almanac is a classic in many countries. Apart from providing a guide on planting and harvesting, it includes weather forecasts, especially long range weather forecast as Farmer’s Almanacs [...]

Weather Funnies

Almost every topic in life can be subject of jokes and funny stories. Weather is not the exception and neither are weathermen. In some countries, especially in regions of severe [...]

Weather Jokes

Some Weather Jokes: What did one tornado say to another? "Let's blow this town!" Did you hear about the weather forecaster who quit her job after making a wrong forecast? She said [...]

Funny Stories

It was autumn, and the Indians on the remote reservation asked their new Chief if the winter was going to be cold or mild. Since he was a new Indian [...]