Historical Storm Corridors
Historical storm corridors depict the event impact which was forecast
to occur during the 10 minute period immediately following the valid time
of the corridor.
Historical storm corridors can be viewed by clicking the Storm Corridors
layer within the Storm History layer menu.
Historical storm corridors are available for the past hour - out to
the past seven days. Set your custom filter to display any or all storm
types or only those with a minimum probability and size of hail. A sliding
24 hour window can be viewed at one time. The corridors are color-coded
based on the type of activity which was detected in the storm cell by
NEXRAD at the valid time.
|
Heavy
Rain |
Intense precipitation, strong wind and/or small hail has
been detected. |
|
Severe
Hail |
An event having at least a 25% probability of severe hail
with a diameter of 1" (2.5 cm) or greater has been detected. Note: The NWS has recently changed the
definition of Severe Hail from .75" to 1". |
|
Dangerous
T-Storm |
A strong thunderstorm with a mesocyclone (rotation aloft)
having an index of 1 or greater has been detected. |
|
Possible
Tornado |
A thunderstorm with a tornadic vortex signature (TVS) has
been detected. |
Corridors are available at the four tightest zoom levels. Information
is available by clicking the Get Details icon
and hovering over the displayed corridor.
|
Detected Activity |
Definition |
|
Hail |
The probability of hail and/or severe hail and the maximum
size expected. |
|
Mesocyclone |
Rotation detected at multiple levels in a storm and the
stringent wind and wind shear criteria are met. Strength is categorized
using an index of 1 - 6+. |
|
Tornadic Vortex Signature (TVS) |
Indication of a possible tornado. Strong wind shear has
been detected in a very small area and is usually associated with a potential
tornadic circulation within a thunderstorm. |
The following radar reported index value representing the strength of
a mesocyclone signature is used within storm corridors.
|
Value |
Descriptor |
Definition |
|
0 |
None |
No mesocyclone |
|
1 - 2 |
Weak |
Weak mesocyclone detected |
|
3 - 5 |
MDT |
Moderate mesocyclone detected |
|
6+ |
Strong |
Strong mesocyclone detected |
|
255 |
Error Condition |
Error condition |
|
Full Length |
10 minute forecast period |
|
Half Length |
5 minutes (depicted as dashed line) |
|
Width |
One mile (1.6 km) |
|
Deviation Angle |
Five degrees |
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