Subj : Wx Terms (M)(4)
To : All
From : Daryl Stout
Date : Mon Aug 14 2017 07:24 am
Middle Clouds
(or Mid-Level Clouds) - A term used to signify clouds with bases between
6,500 and 23,000 feet. At the higher altitudes, they may also have some
ice crystals, but they are composed mainly of water droplets. Altocumulus,
altostratus, and nimbostratus are the main types of middle clouds. This
altitude applies to the temperate zone. In the polar regions, these
clouds may be found at lower altitudes. In the tropics, the defining
altitudes for cloud types are generally higher.
Middle Latitudes
1) The latitude belt roughly between 35 and 65 degrees North and South.
Also referred to as the temperate region.
or
2) With specific reference to zones of geomagnetic activity, "middle
latitudes" refers to 20� to 50� geomagnetic.
Mie Scattering
Any scattering produced by spherical particles whose diameters are
greater than 1/10 the wavelength of the scattered radiation. This type
of scattering causes the clouds to appear white in the sky. Often, hail
exhibits in this type of scattering.
Millibar
A unit of atmospheric pressure equal to 1/1000 bar, or 1000 dynes per
square centimeter.
MIN
Minimum (or) Minute
Minimum Discernible Signal
In a receiver, it is the smallest input signal that will a produce a
detectable signal at the output. In radar terms, it is the minimal
amount of back scattered energy that is required to produce a target
on the radar screen. In other words, MDS is a measure of the radar's
sensitivity.
Minimum Temperature
This is the lowest temperature recorded during a specified period of
time. The time period can be 6, 12 or 24 hours. The most common
reference is to the daily minimum temperature, or "low."
Minor Flooding
A general term indicating minimal or no property damage but possibly
some public inconvenience.
Minor Tidal Overflow
Minor flooding caused by high tides that results in little if any damage.
MINT
minimum temperature
MISC
Miscellaneous
MISG
Missing
Misoscale
The scale of meteorological phenomena that ranges in size from 40
meters to about 4 kilometers. It includes rotation within a thunderstorm.
Mist
A visible aggregate of minute water particles suspended in the atmosphere
that reduces visibility to less than 7 statute miles, but greater than or
equal to 5/8 statute miles. It does not reduce visibility as much as fog
and is often confused with drizzle.
Mixed Layer
An atmospheric layer, usually the layer immediately above the ground, in
which pollutants are well mixed by convective or shear-produced
turbulence.
Mixed Precipitation
Any of the following combinations of freezing and frozen precipitation:
snow and sleet, snow and freezing rain, or sleet alone. Rain may also be
present.
Mixing Depth
Vertical distance between the ground and the altitude to which pollutants
are mixed by turbulence caused by convective currents or vertical shear
in the horizontal wind.
Mixing Heights
The height to which a parcel of air, or a column of smoke, will rise, mix
or disperse. A column of smoke will remain trapped below this height.
Mixing Ratio
The ratio of the weight of water vapor in a specified volume (such as an
air parcel) to the weight of dry air in that same volume.
MJO
Madden-Julian Oscillation- Tropical rainfall exhibits strong variability
on time scales shorter than the seasonal El Ni�o-Southern Oscillation
(ENSO). These fluctuations in tropical rainfall often go through an entire
cycle in 30-60 days, and are referred to as the Madden-Julian Oscillation
or intraseasonal oscillations. The intraseasonal oscillations are a
naturally occurring component of our coupled ocean-atmosphere system.
They significantly affect the atmospheric circulation throughout the
global Tropics and subtropics, and also strongly affect the wintertime
jet stream and atmospheric circulation features over the North Pacific
and western North America. As a result, they have an important impact on
storminess and temperatures over the United States. During the summer
these oscillations have a modulating effect on hurricane activity in both
the Pacific and Atlantic basins.
MLCAPE
Mean Layer CAPE - CAPE calculated using a parcel consisting of Mean Layer
values of temperature and moisture from the lowest 100 mb above ground
level. See Convective Available Potential Energy (CAPE).
MLLI
Mean Layer Lifted Index - Lifted Index (LI) calculated using a parcel
consisting of Mean Layer values of temperature and moisture from the
lowest 100 mb above ground level. See Lifted Index (LI).
MLLW
(Mean Lower Low Water) - A tidal datum. The average of the lower low
water height of each tidal day observed over the National Tidal Datum
Epoch. For stations with shorter series, simultaneous observational
comparisons are made with a control tide station in order to derive the
equivalent datum of the National Tidal Datum Epoch.
MLW
(Mean Low Water) - A tidal datum. The average of all the low water
heights observed over the National Tidal Datum Epoch. For stations
with shorter series, simultaneous observational comparisons are made
with a control tide station in order to derive the equivalent datum
of the National Tidal Datum Epoch.
MNLY
Mainly
MOBY
Marine Optical Buoy. It measures solar radiation to calibrate satellite
ocean color instruments.
Model Output Statistics
(abbrev. MOS) - the Hydrometeorological Center (HPC) produces a short
range (6 to 60 hours) MOS (Model Output Statistics) guidance package
generated from the NGM, GFS, and ETA models for over 300 individual
stations in the continental United States. These alphanumeric messages
are made available at approximately 0400 and 1600 UTC for the 0000 and
1200 UTC forecast cycles, respectively. Model Output Statistics are a
set of statistical equations that use model output to forecast the
probability of precipitation, high and low temperature, cloud cover,
and precipitation amount for many cities across the USA. The
statistical equations were specifically tailored for each location,
taking into account factors such as each location's climate.
Moderate Flooding
The inundation of secondary roads; transfer to higher elevation
necessary to save property -- some evacuation may be required.
Moderate Risk (of severe thunderstorms)
Severe thunderstorms are expected to affect between 5 and 10 percent
of the area. A moderate risk indicates the possibility of a significant
severe weather episode. See high risk, slight risk, convective outlook.
Moist Adiabat
The line on a Skew T-Log P chart that depicts the change in temperature
of saturated air as it rises and undergoes cooling due to adiabatic
expansion. As saturated air rises, the temperature changes at a rate of
0.55 degrees Celsius per 100 meters (2-3 degrees Fahrenheit per 1,000
feet). Contrast with a dry adiabat.
Moist Adiabatic Lapse Rate
(abbrev. MALR)- The rate at which the temperature of a parcel of
saturated air decreases as the parcel is lifted in the atmosphere. The
moist adiabatic lapse rate (abbreviated MALR) is not a constant like the
dry adiabatic lapse rate but is dependent on parcel temperature and
pressure.
Moist-adiabatic
(Also known as saturation-adiabatic process.) An adiabatic process for
which the air is saturated and may contain liquid water. A distinction
is made between the reversible process, in which total water is
conserved, and the pseudoadiabatic or irreversible moist adiabatic
process, in which liquid water is assumed to be removed as soon as it
is condensed.
Moisture
Refers to the water vapor content in the atmosphere, or the total water,
liquid, solid or vapor, in a given volume of air.
Moisture Advection
Transport of moisture by horizontal winds.
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.
Moisture Equivalent
In hydrologic terms, the ratio of the weight of water which the soil,
after saturation, will retain against a centrifugal force 1,000 times
the force of gravity, to the weight of the soil when dry. The ratio is
stated as a percentage.
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