Moore Oklahoma Obliterated by F5 Tornado, 24 dead, at least 9 of them kids

[Admiral Yi]

No one home Meri.

[Baron von Schtinkenbutt]

Sigh.  It helps to actually read what I wrote.

The sirens only go off when a Tornado has been spotted, so it's very easy for one to come crashing down before someone has spotted it.

This is absolutely not true.  The definition you posted says this:

This is issued when a tornado is indicated by the WSR-88D radar or sighted by spotters

Indications of tornadic activity on the WSR-88D are usually not positive evidence that a tornado has actually formed, or is even guaranteed to form.  From a NOAA tech memo on issuing warnings using the WSR-88D:

The first guidelines for supercell tornadoes are the Lemon criteria (Fig. 20). These include the presence of a bounded weak echo region or a hook echo in conjunction with peak middle level reflectivities (16,000 to 39,000 ft) of 46 dBZ or greater, middle level overhang, and highest echo top over the low level reflectivity gradient. These radar signatures are all indicative of a strong rotating updraft. These signatures will form on the inflow part of the storm, usually on the southeast to southwest side.

A strong mesocyclone (Fig. 22) may be visible in the SRM Doppler data near where a hook echo is on the low level reflectivity data. A good example of a hook echo is seen in Color Plate B1 near Lancaster, Texas, just south of Dallas. Mid-level overhang above the low-level reflectivity gradient can be seen by comparing B1a and B1b. A strong mesocyclone can be seen in the same area. Lancaster was hit by a devastating tornado as this supercell storm moved through the town. All of these supercell features correlate well with the conceptual model of a classic supercell seen in Figs. 3 and 4c.

The WSR-88D Doppler radar algorithm generated tornado vortex signature (TVS) is also a feature that can be used to issue tornado warnings, although this feature is only triggered by the strongest of mesocyclones, and perhaps, may only be seen after the tornado has touched down.

Mini supercells are also listed in the supercell section because they will also have many of the same reflectivity features of the supercell. One difference is that the mesocyclone will be weaker in the SRM velocity data as compared to a supercell. However, the mesocyclone will be smaller in diameter for the mini supercell, so a lower rotational velocity in the mesocyclone may be considered for a tornado warning with a mini supercell. In mini supercells with mesocyclone diameters of 2.0 nm or less, the rotational velocities in Table 2 could produce tornadoes (OSF 1995).

None of that is definitive evidence of a tornado, with the possible exception of the TVS.  In fact, one of the goals of using the guidelines above with the algorithms in the WSR-88D is to get the warnings issued when tornado formation is imminent.  The estimated false alarm rate on warnings is currently about 75%.

On top of the above, the specific interpretation of radar indicators is up to the local NWS office, based on local patterns and conditions (emphasis theirs):

In the following discussion, references will be made to "strong mesocyclones." Each office will have to define what criteria will constitute a strong mesocyclone based on type of environment, distance from the radar, rotational velocity, diameter of the mesocyclone, time of year, type of storm, and local climatology of storms. For example, in Shreveport during the fall and winter months, a strong mesocyclone is considered to have (1) a velocity rotational signature in the low levels, (2) an SRM velocity of 50 kt or greater (or base velocity of 64 kt or greater), in either the inbound or outbound velocity, and (3) a rotational velocity of 36 kt or more. These may be changed as experience with the WSR-88D grows. (Criteria subject to change without notice!) When the environment is favorable for supercells and tornadoes, strong consideration should be given to issuing a tornado warning instead of a severe thunderstorm warning for moderate to strong mesocyclones (see Section 3.b and c).

The objective is to give people as much warning as possible.  At this time, the NWS obviously feels false alarms are preferable to false negatives, and so the majority of the time warnings are not issued with positive confirmation of tornadoes.  Hell, there are cases of actual tornadoes that the NSSL does not confirm until after the fact.

[CountDeMoney]

My sirens go off when a kitteh is sighted.  Mewnadic Activity.

[merithyn]

Sigh.  It helps to actually read what I wrote.

The sirens only go off when a Tornado has been spotted, so it's very easy for one to come crashing down before someone has spotted it.

This is absolutely not true.  The definition you posted says this:

This is issued when a tornado is indicated by the WSR-88D radar or sighted by spotters

Indications of tornadic activity on the WSR-88D are usually not positive evidence that a tornado has actually formed, or is even guaranteed to form.  From a NOAA tech memo on issuing warnings using the WSR-88D:

The first guidelines for supercell tornadoes are the Lemon criteria (Fig. 20). These include the presence of a bounded weak echo region or a hook echo in conjunction with peak middle level reflectivities (16,000 to 39,000 ft) of 46 dBZ or greater, middle level overhang, and highest echo top over the low level reflectivity gradient. These radar signatures are all indicative of a strong rotating updraft. These signatures will form on the inflow part of the storm, usually on the southeast to southwest side.

A strong mesocyclone (Fig. 22) may be visible in the SRM Doppler data near where a hook echo is on the low level reflectivity data. A good example of a hook echo is seen in Color Plate B1 near Lancaster, Texas, just south of Dallas. Mid-level overhang above the low-level reflectivity gradient can be seen by comparing B1a and B1b. A strong mesocyclone can be seen in the same area. Lancaster was hit by a devastating tornado as this supercell storm moved through the town. All of these supercell features correlate well with the conceptual model of a classic supercell seen in Figs. 3 and 4c.

The WSR-88D Doppler radar algorithm generated tornado vortex signature (TVS) is also a feature that can be used to issue tornado warnings, although this feature is only triggered by the strongest of mesocyclones, and perhaps, may only be seen after the tornado has touched down.

Mini supercells are also listed in the supercell section because they will also have many of the same reflectivity features of the supercell. One difference is that the mesocyclone will be weaker in the SRM velocity data as compared to a supercell. However, the mesocyclone will be smaller in diameter for the mini supercell, so a lower rotational velocity in the mesocyclone may be considered for a tornado warning with a mini supercell. In mini supercells with mesocyclone diameters of 2.0 nm or less, the rotational velocities in Table 2 could produce tornadoes (OSF 1995).

None of that is definitive evidence of a tornado, with the possible exception of the TVS.  In fact, one of the goals of using the guidelines above with the algorithms in the WSR-88D is to get the warnings issued when tornado formation is imminent.  The estimated false alarm rate on warnings is currently about 75%.

On top of the above, the specific interpretation of radar indicators is up to the local NWS office, based on local patterns and conditions (emphasis theirs):

In the following discussion, references will be made to "strong mesocyclones." Each office will have to define what criteria will constitute a strong mesocyclone based on type of environment, distance from the radar, rotational velocity, diameter of the mesocyclone, time of year, type of storm, and local climatology of storms. For example, in Shreveport during the fall and winter months, a strong mesocyclone is considered to have (1) a velocity rotational signature in the low levels, (2) an SRM velocity of 50 kt or greater (or base velocity of 64 kt or greater), in either the inbound or outbound velocity, and (3) a rotational velocity of 36 kt or more. These may be changed as experience with the WSR-88D grows. (Criteria subject to change without notice!) When the environment is favorable for supercells and tornadoes, strong consideration should be given to issuing a tornado warning instead of a severe thunderstorm warning for moderate to strong mesocyclones (see Section 3.b and c).

The objective is to give people as much warning as possible.  At this time, the NWS obviously feels false alarms are preferable to false negatives, and so the majority of the time warnings are not issued with positive confirmation of tornadoes.  Hell, there are cases of actual tornadoes that the NSSL does not confirm until after the fact.

A little late to the party there, aren't you, Mr. Stinkybutt?

[Caliga]

Also, just FYI, I'm a weather spotter for the NWS and they don't automatically call a tornado alert just because a spotter calls in a tornado sighting.  During severe weather sometimes people mistake scud formations for tornadoes.  Typically they'll issue an alert if someone phones in a report AND it matches up with radar observations, though.

[CountDeMoney]

http://www.okclostpets.com/

The "lost pets" section is 27 pages long by now...

[Ed Anger]

My sirens go off when a kitteh is sighted.  Mewnadic Activity.

A Squeenado.