Geoscience Reference
In-Depth Information
1
Introduction
...
''
oh now feel it comin' back again
like a rollin' thunder chasing the wind
forces pullin' from the center of the earth again
I can feel it.''
Lyrics from Lighting Crashes by Live
1.1 BASIC DEFINITION OF SEVERE CONVECTIVE STORMS AND
SCOPE OF THE MATERIAL
Severe convective storms worldwide inflict damage to property and crops, disrupt
air, sea, and ground travel and outdoor activity, and, in the most extreme cases,
inflict injuries and even death. While the adjective ''severe'' generally refers to
weather phenomena that produce damage, what is damaging to one type of struc-
ture may not be damaging to another, owing to differences in the integrity of
construction and the nature of the underlying surface. In the U. S., ''severe''
weather associated with local storms (as opposed to storms that are much larger
in scale such as extratropical and tropical cyclones) is defined more precisely by
the Storm Prediction Center (SPC) of the National Weather Service (NWS) as
having one or more of the following: tornadoes, winds equal to or in excess of
25.8m s 1 (58mph), or hail 2.5 cm (1 inch) or greater in diameter, regardless of
whether or not there is actual damage; it is noted that prior to January 5, 2010
the minimum hail size criterion was only 1.9 cm (3/4 inch).
It is perhaps a shortcoming of the U. S. definition of severe weather that
flooding and lightning are not included, even though each of these also may be
responsible for damage, injuries, and death. To maintain a manageable focus,
however, this textbook discusses only the physics of the airflow and cloud and
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