The Creation of Weather

Subchapters: The Source of Weather, The Weather Builders, The Elements, The Effects (mainly Surface Weather), Celestial Phenomena.

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 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 [...]


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 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 [...]


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 [...]


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 [...]


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 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 [...]


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 [...]


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 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 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 [...]