There are 40 names in this directory beginning with the letter M.Macroburst
Large downburst with a 2.5 mile or greater outflow diameter and damaging winds lasting 5 to 20 minutes.
Mamma Clouds
Also called mammatus, these clouds appear as hanging, rounded protuberances or pouches on the under- surface of a cloud. With thunderstorms, mammatus are seen on the underside of the anvil. These clouds do not produce tornadoes, funnels, hail, or any other type of severe weather, although they often accompany severe thunderstorms.
Mean Sea Level (MSL)
The average height of the sea surface, based upon hourly observation of the tide height on the open coast or in adjacent waters that have free access to the sea.
Mean Temperature
The average of a series of temperatures taken over a period of time, such as a day or a month.
Mercury Barometer
An instrument that measures barometric pressure by measuring the level of mercury in a column.
Mesocyclone
A storm- scale region of rotation, typically around 2- 6 miles in diameter and often found in the right rear flank of a supercell (or often on the eastern, or front, flank of an HP storm). The circulation of a mesocyclone covers an area much larger than the tornado that may develop within it.
Mesolow (or Sub- synoptic Low)
A mesoscale low- pressure center. Severe weather potential often increases in the area near and just ahead of a mesolow.
Mesonet
A regional network of observing stations (usually surface stations) designed to diagnose mesoscale weather features and their associated processes.
Mesoscale
Size scale referring to weather systems smaller than synoptic- scale systems but larger than single storm clouds. Horizontal dimensions generally range from around 50 miles to several hundred miles. Squall lines are an example of mesoscale weather systems.
Mesoscale Convective Complex (MCC)
A large mesoscale convective system, generally round or oval- shaped, which normally reaches peak intensity at night. The formal definition includes specific minimum criteria for size, duration, and eccentricity (i.e., "roundness"), based on the cloud shield as seen on infrared satellite photographs:
Mesoscale Convective System (MCS)
A complex of thunderstorms which becomes organized on a scale larger than the individual thunderstorms, and normally persists for several hours or more. MCSs may be round or linear in shape, and include systems such as tropical cyclones, squall lines, and MCCs (among others). MCS often is used to describe a cluster of thunderstorms that does not satisfy the size, shape, or duration criteria of an MCC.
Mesosphere
A layer of the atmosphere separated by the ionosphere above and the stratosphere below extending from about 50km- 80km above the Earth's surface. The air temperature in mesosphere decreases with height.
Metamorphism
Changes in the structure and texture of snow grains which results from variations in temperature, migration of liquid water and water vapor, and pressure within the snow cover
METAR
A weather observation near ground level. It may include date and time, wind, visibility, weather and obstructions to vision, sky condition, temperature and dew point, sea level pressure, precipitation amount and other data used for aircraft operations.
Meteorologist
A person who studies meteorology. Some examples include research meteorologist, climatologist, operational meteorologist, TV meteorologist.
Mid - Latitudes
The areas in the northern and southern hemispheres between the tropics and the Arctic and Antarctic circles.
Millibar
A metric unit of atmospheric pressure. 1 mb = 100 Pa (pascal). Normal surface pressure is approximately 1013 millibars.
Mist
Consists of microscopic water droplets suspended in the air which produce a thin grayish veil over the landscape. It reduces visibility to a lesser extent than fog.
Model
A mathematical representation of a process, system, or object developed to understand its behavior or to make predictions. The representation always involves certain simplifications and assumptions.
Moderate Risk (of severe thunderstorms)
Severe thunderstorms are expected to affect between 5 and 10 percent of the area.
Moisture Convergence
A measure of the degree to which moist air is converging into a given area, taking into account the effect of converging winds and moisture advection. Areas of persistent moisture convergence are favored regions for thunderstorm development, if other factors (e.g., instability) are favorable.
Monsoon
A persistent seasonal wind, often responsible for seasonal precipitation regime. It is most commonly used to describe meteorological changes in - southern and eastern Asia.
Morning Glory
An elongated cloud band, visually similar to a roll cloud, usually appearing in the morning hours, when the atmosphere is relatively stable. Morning glories result from perturbations related to gravitational waves in a stable boundary layer.
Multicell Cluster Thunderstorm
A thunderstorm consisting of two or more cells, of which most or all are often visible at a given time as distinct domes or towers in various stages of development.
Multivortex Tornado
A tornado in which two or more condensation funnels or debris clouds are present at the same time, often rotating about a common center or about each other. Multiple- vortex tornadoes can be especially damaging.
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Macroburst
Large downburst with a 2.5 mile or greater outflow diameter and damaging winds lasting 5 to 20 minutes.
Mamma Clouds
Also called mammatus, these clouds appear as hanging, rounded protuberances or pouches on the under- surface of a cloud. With thunderstorms, mammatus are seen on the underside of the anvil. These clouds do not produce tornadoes, funnels, hail, or any other type of severe weather, although they often accompany severe thunderstorms.
Mean Sea Level (MSL)
The average height of the sea surface, based upon hourly observation of the tide height on the open coast or in adjacent waters that have free access to the sea.
Mean Temperature
The average of a series of temperatures taken over a period of time, such as a day or a month.
Mercury Barometer
An instrument that measures barometric pressure by measuring the level of mercury in a column.
Mesocyclone
A storm- scale region of rotation, typically around 2- 6 miles in diameter and often found in the right rear flank of a supercell (or often on the eastern, or front, flank of an HP storm). The circulation of a mesocyclone covers an area much larger than the tornado that may develop within it.
Mesolow (or Sub- synoptic Low)
A mesoscale low- pressure center. Severe weather potential often increases in the area near and just ahead of a mesolow.
Mesonet
A regional network of observing stations (usually surface stations) designed to diagnose mesoscale weather features and their associated processes.
Mesoscale
Size scale referring to weather systems smaller than synoptic- scale systems but larger than single storm clouds. Horizontal dimensions generally range from around 50 miles to several hundred miles. Squall lines are an example of mesoscale weather systems.
Mesoscale Convective Complex (MCC)
A large mesoscale convective system, generally round or oval- shaped, which normally reaches peak intensity at night. The formal definition includes specific minimum criteria for size, duration, and eccentricity (i.e., "roundness"), based on the cloud shield as seen on infrared satellite photographs:
Mesoscale Convective System (MCS)
A complex of thunderstorms which becomes organized on a scale larger than the individual thunderstorms, and normally persists for several hours or more. MCSs may be round or linear in shape, and include systems such as tropical cyclones, squall lines, and MCCs (among others). MCS often is used to describe a cluster of thunderstorms that does not satisfy the size, shape, or duration criteria of an MCC.
Mesosphere
A layer of the atmosphere separated by the ionosphere above and the stratosphere below extending from about 50km- 80km above the Earth's surface. The air temperature in mesosphere decreases with height.
Metamorphism
Changes in the structure and texture of snow grains which results from variations in temperature, migration of liquid water and water vapor, and pressure within the snow cover
METAR
A weather observation near ground level. It may include date and time, wind, visibility, weather and obstructions to vision, sky condition, temperature and dew point, sea level pressure, precipitation amount and other data used for aircraft operations.
Meteorologist
A person who studies meteorology. Some examples include research meteorologist, climatologist, operational meteorologist, TV meteorologist.
Mid - Latitudes
The areas in the northern and southern hemispheres between the tropics and the Arctic and Antarctic circles.
Millibar
A metric unit of atmospheric pressure. 1 mb = 100 Pa (pascal). Normal surface pressure is approximately 1013 millibars.
Mist
Consists of microscopic water droplets suspended in the air which produce a thin grayish veil over the landscape. It reduces visibility to a lesser extent than fog.
Model
A mathematical representation of a process, system, or object developed to understand its behavior or to make predictions. The representation always involves certain simplifications and assumptions.
Moderate Risk (of severe thunderstorms)
Severe thunderstorms are expected to affect between 5 and 10 percent of the area.
Moisture Convergence
A measure of the degree to which moist air is converging into a given area, taking into account the effect of converging winds and moisture advection. Areas of persistent moisture convergence are favored regions for thunderstorm development, if other factors (e.g., instability) are favorable.
Monsoon
A persistent seasonal wind, often responsible for seasonal precipitation regime. It is most commonly used to describe meteorological changes in - southern and eastern Asia.
Morning Glory
An elongated cloud band, visually similar to a roll cloud, usually appearing in the morning hours, when the atmosphere is relatively stable. Morning glories result from perturbations related to gravitational waves in a stable boundary layer.
Multicell Cluster Thunderstorm
A thunderstorm consisting of two or more cells, of which most or all are often visible at a given time as distinct domes or towers in various stages of development.
Multivortex Tornado
A tornado in which two or more condensation funnels or debris clouds are present at the same time, often rotating about a common center or about each other. Multiple- vortex tornadoes can be especially damaging.