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Definition and Properties: A "Squall
line" is a more or less straight alignment of thunderstorm
cells, high Cumulus or Cumulonimbus clouds. It is a linear arrangement
of convection, shown orthogonally to the image plane of "SquallLineScheme.jpg".
In connection with squall lines often strong winds of short duration
occur. These typically fast moving "lines" can reach lengths
between 20 and 1500 km. They can be part of a "Mesoscale Convective
System (MCS)". The "Squall lines" are often located
directly in front of cold fronts in a distance of 150 to 500 km
with parallel alignment. |
The images were taken at Morro Branco, approximately 100 km southeast
of Fortaleza at the Brazilian Atlantic Coast shortly after sunrise.
At the top the squall line is presented as a linear arrangement
of Cumulonimbus systems. Three Cb towers can be recognized in behind
each other. A fourth one was above the observer, beyond the horizon
there could be even more. The cloud bases were all at the same level
at the "lifting condensation level". The image in the
second row shows the falling rain of the front Cb tower in detail.
In the last three images views from the neighbourhood of the photographer
in different directions are shown. The squall line was surrounded
by various layered, cumulus and rotor clouds in a wide range. The
strong choppy wind which is characteristic for squall lines could
be also here clearly observed.
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The V-shaped cloud structure is normally associated with cold fronts that cross the Gulf of Mexico and Florida in late winter and early spring. Severe thunderstorms and tornadoes usually occur with this type of storm system. At the time this photograph was taken, weather stations across Florida reported severe thunderstorms, strong winds, hail, torrential rains, and numerous tornadoes.
Camera Parameters Olympus E-1 SLR with 14-54 mm objective. Exposure and Sensitivity choice (100 ASA) was performed automatically by the camera. The images were taken in the sRGB colour range with a resolution of 2560 x 1920 Pixel x 24 colours. Since the whole scenery was very dark, the shot noise of the CCD elements became slightly visible. It could be reduced by the noise reduction function of the camera. |
Lens aperture
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Time of exposure
|
Focal length
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SquallLine1.jpg |
5.6 |
1/200 |
27 |
SquallLine3.jpg |
5.6 |
1/320 |
54 |
SquallLine4.jpg |
6.3 |
1/200 |
14 |
SquallLine5.jpg |
6.3 |
1/200 |
25 |
SquallLine7.jpg |
6.3 |
1/200 |
14 |
SquallLine9.jpg |
5.6 |
1/250 |
38 |
SquallLine10.jpg |
4.5 |
1/160 |
37 |
SquallLine13.jpg |
5.0 |
1/200 |
31 |