Subj : Wx Terms (S)(9)
To : All
From : Daryl Stout
Date : Wed Sep 20 2017 12:05 am
Stratospheric Ozone
In the stratosphere, ozone has beneficial properties where it forms an
ozone shield that prevents dangerous radiation from reaching the Earth's
surface. Recently, it was discovered that in certain parts of the world,
especially over the poles, stratospheric ozone was disappearing creating
an ozone hole.
Stratus
A low, generally gray cloud layer with a fairly uniform base. Stratus may
appear in the form of ragged patches, but otherwise does not exhibit
individual cloud elements as do cumulus and stratocumulus clouds. Fog
usually is a surface-based form of stratus.
Stream line
Arrows on a weather chart showing wind speed and direction. The head of
the arrow points toward where the wind is blowing and the length of the
arrow is proportional to the wind speed. Sometimes shows wind direction
and trajectory only.
Streamflow
In hydrologic terms, water flowing in the stream channel. It is often
used interchangeably with discharge.
STRFM
Stratiform
Striations
Grooves or channels in cloud formations, arranged parallel to the flow
of air and therefore depicting the airflow relative to the parent cloud.
Striations often reveal the presence of rotation, as in the barber pole
or "corkscrew" effect often observed with the rotating updraft of a Low
Precipitation (LP) storm.
Strike
For any particular location, a hurricane strike occurs if that location
passes within the hurricane's strike circle, a circle of 125 n mi
diameter, centered 12.5 n mi to the right of the hurricane center
(looking in the direction of motion). This circle is meant to depict the
typical extent of hurricane force winds, which are approximately 75 n mi
to the right of the center and 50 n mi to the left.
Sub-synoptic Low
Essentially the same as mesolow.
Sublimation
The transition of a substance from the solid phase directly to the vapor
phase, or vice versa, without passing through an intermediate liquid
phase. Thus an ice crystal or icicle sublimes under low relative humidity
at temperatures below 0�C. The process is analogous to evaporation of a
liquid.
Sublimation of ice
The transition of water from solid to gas without passing through the
liquid phase.
Subrefraction
The bending of the radar beam in the vertical which is less than under
standard refractive conditions. This causes the beam to be higher than
indicated, and lead to the underestimation of cloud heights.
Subsidence
1. A descending motion of air in the atmosphere occurring over a rather
broad area.
2. In hydrologic terms, sinking down of part of the earth's crust due to
underground excavation, such as the removal of groundwater.
Subsidence Inversion
A temperature inversion that develops aloft as a result of air gradually
sinking over a wide area and being warmed by adiabatic compression,
usually associated with subtropical high pressure areas.
Substation
A location where observations are taken or other services are furnished
by people not located at NWS offices who do not need to be certified to
take observations.
Subsurface Storm Flow
In hydrologic terms, the lateral motion of water through the upper layers
until it enters a stream channel. This usually takes longer to reach
stream channels than runoff. This also called interflow.
Subtle Heavy Rainfall Signature
This heavy rain signature is often difficult to detect on satellite. These
warm top thunderstorms are often embedded in a synoptic-scale cyclonic
circulation. Normally, they occur when the 500 mb cyclonic circulation is
quasi-stationary or moves slowly to the east or northeast (about 2 degrees
per 12 hours). The average surface temperature is 68�F with northeasterly
winds. The average precipitable water (P) value is equal to or greater
than 1.34 inches and the winds veer with height, but they are relatively
light. The heavy rain often occurs north and east of the vorticity maximum
across the lower portion of the comma head about 2 to 3 degrees north or
northeast of the 850 mb low.
Subtropical Cyclone
A non-frontal low pressure system that has characteristics of both
tropical and extratropical cyclones. This system is typically an
upper-level cold low with circulation extending to the surface layer and
maximum sustained winds generally occurring at a radius of about 100
miles or more from the center. In comparison to tropical cyclones, such
systems have a relatively broad zone of maximum winds that is located
farther from the center, and typically have a less symmetric wind field
and distribution of convection.
Subtropical Depression
A subtropical cyclone in which the maximum 1-minute sustained surface
wind is 33 knots (38 mph) or less.
Subtropical Jet
(Abbrev. STJ) - this jet stream is usually found between 20� and 30�
latitude at altitudes between 12 and 14 km.
Subtropical Storm
A subtropical cyclone in which the maximum 1-minute sustained surface
wind is 34 knots (39 mph) or more.
Suction Vortex
A small but very intense vortex within a tornado circulation. Several
suction vortices typically are present in a multiple-vortex tornado.
Much of the extreme damage associated with violent tornadoes (F4 and F5
on the Fujita scale) is attributed to suction vortices.
Sudden Commencement (SC)
In solar-terrestrial terms, an abrupt increase or decrease in the
northward component of the geomagnetic field, which marks the beginning
of a geomagnetic storm.
Sudden Impulse (SI+ or SI-)
In solar-terrestrial terms, a sudden perturbation of several gammas in
the northward component of the low-latitude geomagnetic field, not
associated with a following geomagnetic storm. (An SI becomes an SC if
a storm follows.)
Sudden Ionospheric Disturbance (SID)
In solar-terrestrial terms, HF propagation anomalies due to ionospheric
changes resulting from solar flares, proton events and geomagnetic storms.
SUF
Sufficient
Summation Principle
This principle states that the sky cover at any level is equal to the
summation of the sky cover of the lowest layer plus the additional sky
cover provided at all successively higher layers up to and including the
layer in question.
Summer
Typically the warmest season of the year during which the sun is most
nearly overhead. In the Northern Hemisphere, summer customarily includes
the months of June, July, and August.
Summer Solstice
The time at which the sun is farthest north in the Northern Hemisphere,
on or around June 21.
Sun Dog
See Parhelion
Sun Pillar
A bright column above or below the sun produced by the reflection of
sunlight from ice crystals.
Sun Pointing
Alignment of the radar antenna by locating the position of the sun in the
sky, which has an exactly known position given the radar's location and
the present time. This may be necessary to verify that when we think
we're pointing "north", we actually are! The sun's signal is usually
several dB above the background noise, and this technique is also
sometimes used to examine the receiver sensitivity.
Sunny
When there are no opaque (not transparent) clouds. Same as Clear.
Sunrise
The phenomenon of the sun's daily appearance on the eastern horizon as
a result of the earth's rotation. The word is often used to refer to
the time at which the first part of the sun becomes visible in the
morning at a given location.
Sunset
The phenomenon of the sun's daily disappearance below the western
horizon as a result of the earth's rotation. The word is often used to
refer to the time at which the last part of the sun disappears below
the horizon in the evening at a given location.
Sunspot
In solar-terrestrial terms, an area seen as a dark spot on the
photosphere of the sun. Sunspots are concentrations of magnetic flux,
typically occurring in bipolar clusters or groups. They appear dark
because they are cooler than the surrounding photosphere.
---
� Synchronet � The Thunderbolt BBS - wx1der.dyndns.org
