Subj : Wx Terms (M)(3)
To   : All
From : Daryl Stout
Date : Sat Oct 14 2017 12:05 am

Mesoclimate
The climate of a small area of the earth's surface which may differ from
the general climate of the district.

Mesocyclone
(abbrev. MESO)- 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. Properly used, mesocyclone is a radar term;
it is defined as a rotation signature appearing on Doppler radar that
meets specific criteria for magnitude, vertical depth, and duration. It
will appear as a yellow solid circle on the Doppler velocity products.
Therefore, a mesocyclone should not be considered a visually-observable
phenomenon (although visual evidence of rotation, such as curved inflow
bands, may imply the presence of a mesocyclone).

Mesohigh
A relatively small area of high atmospheric pressure that forms beneath
a thunderstorm. It is usually associated with an MCS or its remnants.

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.
Mesolow should not be confused with mesocyclone, which is a storm-scale
phenomenon.

Mesonet
A regional network of observing stations (usually surface stations)
designed to diagnose mesoscale weather features and their associated
processes.

Mesopause
The top of the mesosphere, corresponding to the level of minimum
temperature in the atmosphere found at 70 to 80 km.

Mesoscale
Size scale referring to weather systems smaller than synoptic-scale
systems but larger than storm-scale systems. Horizontal dimensions
generally range from around 50 miles to several hundred miles. Squall
lines, MCCs, and MCSs are examples of mesoscale weather systems.

Mesoscale Convective Complex
(abbrev. MCC)- MCC - Mesoscale Convective Complex. A large Mesoscale
Convective System (MCS), 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:

* Size: Area of cloud top -32 degrees C or less: 100,000 square
kilometers or more (slightly smaller than the state of Ohio), and area
of cloud top -52 degrees C or less: 50,000 square kilometers or more.

* Duration: Size criteria must be met for at least 6 hours.

* Eccentricity: Minor/major axis at least 0.7.

MCCs typically form during the afternoon and evening in the form of
several isolated thunderstorms, during which time the potential for
severe weather is greatest. During peak intensity, the primary threat
shifts toward heavy rain and flooding.

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.

Mesoscale Discussion
When conditions actually begin to shape up for severe weather, SPC
(Storm Prediction Center) often issues a Mesoscale Discussion (MCD)
statement anywhere from roughly half an hour to several hours before
issuing a weather watch. SPC also puts out MCDs for hazardous winter
weather events on the mesoscale, such as locally heavy snow, blizzards
and freezing rain (see below). MCDs are also issued on occasion for
heavy rainfall, convective trends, and other phenomena, when the
forecaster feels he/she can provide useful information that is not
readily available or apparent to field forecasters. MCDs are based on
mesoscale analysis and interpretation of observations and of short
term, high resolution numerical model output.

The MCD basically describes what is currently happening, what is expected
in the next few hours, the meteorological reasoning for the forecast, and
when/where SPC plans to issue the watch (if dealing with severe
thunderstorm potential). Severe thunderstorm MCDs can help you get a
little extra lead time on the weather and allow you to begin gearing up
operations before a watch is issued. The MCD begins with a numerical
string that gives the LAT/LON coordinates of a polygon that loosely
describes the area being discussed.

Mesoscale High Winds
These high winds usually follow the passage of organized convective
systems and are associated with wake depressions or strong mesohighs.

Mesosphere
The atmospheric shell between about 20 km and about 70 to 80 km,
extending from the top of the stratosphere (the stratopause) to the
upper temperature minimum that defines the mesopause (the base of the
thermosphere).

MET

1) Meteorological

2) MOS (Model Output Statistics) guidance based on Environmental
Modeling Centers ETA model

METAR
An international code (Aviation Routine Weather Report) used for
reporting, recording and transmitting weather observations.

Meteogram
A graphical depiction of trends in meteorological variables such as
temperature, dew point, wind speed and direction, pressure, etc. The
time series meteogram can be constructed using observed data or
forecast data.

Meteoric Water
Water derived from precipitation.

Meteorologist
A person who studies meteorology. There are many different paths within
the field of meteorology. For example, one could be a research
meteorologist, radar meteorologist, climatologist, or operational
meteorologist.

Meteorology
The science dealing with the atmosphere and its phenomena. A distinction
can be drawn between meteorology and climatology, the latter being
primarily concerned with average, not actual, weather conditions.

METRO
Metropolitan

MeV
Mega (million) electronvolt. A unit of energy used to describe the total
energy carried by a particle or photon.

MEX
1) GFS Model Guidance

2) Mexico

MI
1) Mile

2) Michigan

MIC
Meteorologist In Charge

Microbarograph
A instrument designed to continuously record a barometer's reading of
very small changes in atmospheric pressure.

Microburst
A convective downdraft with an affected outflow area of less than 2 miles
wide and peak winds lasting less than 5 minutes. Microbursts may induce
dangerous horizontal/vertical wind shears, which can adversely affect
aircraft performance and cause property damage.

Microclimate
The climate of a small area such as a cave, house, city or valley that
may be different from that in the general region.

Micron
Unit of length equal to one thousandth (1/1000) of a millimeter; one
millionth (1/1000000) of a meter (1x10-6 m).

Microscale
Pertaining to meteorological phenomena, such as wind circulations or
cloud patterns, that are less than 2 km in horizontal extent.

Microwave
A type of electromagnetic radiation with wavelengths between those of
infrared radiation and radio waves.

Microwave Burst
In solar-terrestrial terms, a radiowave signal associated with optical
and/or X-ray flares.

MID
Middle

Mid-Flame Wind
Wind measured at the midpoint of the flames, considered to be most
representative of the speed of the wind that is affecting fire behavior.

Mid-Latitude Areas
Areas between 30� and 60� north and south of the Equator.

Mid-level Cooling
Local cooling of the air in middle levels of the atmosphere (roughly 8 to
25 thousand feet), which can lead to destabilization of the entire
atmosphere if all other factors are equal.



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