Tornado emergency/PDS tornado watch

[STurner]

I have a few questions on how they issue PDS tornado watches and tornado emergencies. Like for instance, take our first two tornadoes to be rated EF5 on the new EF-scale which were Greensburg and Parkersburg. Greensburg was under no PDS tornado watch but received a tornado emergency as that large beast approached the community. On the other hand Parkersburg was under a PDS tornado watch but did not receive a tornado emergency. Is there reasons why one area may be under a PDS tornado watch but the other area receives a tornado emergency. Is there criteria that must be met before the NWS issues these rare types of events. A lot of people tend to believe that Greensburg was under a PDS tornado but was actually just a regular tornado watch. I believe it was tornado watch #227 which had a 50% of two or more tornadoes and a 30% chance of one or more EF2-EF5 tornadoes. I could be wrong on this but that is what I can remember. Also people should take any tornado watch or any tornado warning seriously because some scary things have happened even though a PDS watch or tornado emergency was not issued.

 

[Danny Neal]

http://www.stormtrack.org/forum/showthread.php?t=12361&highlight=tornado+emergency is a start

 

[Skip Talbot]

Watches and warnings are issued by separate entities. The Storm Prediction Center for the former and a locan weather service office for the latter. Its the met issuing the warning that is going to determine what text goes into that warning and this decision is made from current information. IE is there a large, damaging tornado heading for a populated area? The watch on the other hand is based on conditions that may not have produced tornadoes yet So the warning text really has nothing to do with what conditions were present or forecasted when a watch was issued. Also, you'll notice that SPC tends to issue PDS watches when there is a high risk or at least a 30% tornado outlook. Although Parkersburg only had a moderate on the convective outlook, the 15% hatched still denoted that strong tornadoes were possible.

 

[Dean Baron]

The Parkersburg tornado was wrapped in very heavy rain and forecasters had no ground verification of a large and violent tornado, atleast until chasers saw the damage as they drove thru Parkersburg. On the other hand, although the Greensburg tornado occurred after dark, chasers were still able to pick out a large tornado with help of the lightning illuminating the sky.

 

[STurner]

The Parkersburg tornado was wrapped in very heavy rain and forecasters had no ground verification of a large and violent tornado, atleast until chasers saw the damage as they drove thru Parkersburg. On the other hand, although the Greensburg tornado occurred after dark, chasers were still able to pick out a large tornado with help of the lightning illuminating the sky.

Thank you Dean that seems to clears up some of these things on tornado emergencies and PDS tornado watches. I dont know much about radar but did not know a rain-wrapped tornado may not show up clearly on radar even though it was violent. Was the tornado watch for Greensburg just a regular tornado watch because it took time for the cap to break or something to do with the dryline.

 

[Dean Baron]

Thank you Dean that seems to clears up some of these things on tornado emergencies and PDS tornado watches. I dont know much about radar but did not know a rain-wrapped tornado may not show up clearly on radar even though it was violent. Was the tornado watch for Greensburg just a regular tornado watch because it took time for the cap to break or something to do with the dryline.

I'm sure forecasters were able to pick out a strong area of rotation in the Parkersburg storm hence the tornado warning that was issued, but my guess as to why a tornado emergency wasnt issued for Butler county, IA is that the NWS hadnt received any reports from chasers/spotters/media about visually seeing a large/violent tornadoes prior to the storm hitting Parkersburg. The Greensburg storm I know less about, I wasnt looking at models/surface obs for this event. Im sure somebody could do a good job of explaining that setup/storm.

Also, keep in mind that there is certain criteria that must be met to issue a tornado emergency, one of the criteria is that the area impacted has to have a certain population. I dont know the population of Parkersburg or surrounding cities, but this may also be a reason why a tornado emergency was not issued.

 

[Danny Neal]

I'm sure forecasters were able to pick out a strong area of rotation in the Parkersburg storm hence the tornado warning that was issued, but my guess as to why a tornado emergency wasnt issued for Butler county, IA is that the NWS hadnt received any reports from chasers/spotters/media about visually seeing a large/violent tornadoes prior to the storm hitting Parkersburg. The Greensburg storm I know less about, I wasnt looking at models/surface obs for this event. Im sure somebody could do a good job of explaining that setup/storm.

Also, keep in mind that there is certain criteria that must be met to issue a tornado emergency, one of the criteria is that the area impacted has to have a certain population. I dont know the population of Parkersburg or surrounding cities, but this may also be a reason why a tornado emergency was not issued.

As noted in the other thread.....A tornado emergency is not an official NWS term. It is usually used by the forecaster to highlight the significance of the situation. On June 7th, a half mile wide multi vortex tornado moved into the SE side of the CHI metro area and a standard tornado warning was issued with 0 deaths and a few injuries. The warning stated large extremely dangerous tornado. Tornado emergencies aren't exactly necessary. As Greg Stumpf has said in the past, TE are used mainly for public service (police, fire, hospital) to alert them of the impending danger.

There is no correlation between PDS watches and tornado emergencies.

 

[Adam Lucio]

You cant classify the severity of an event BEFORE it happens. A forecaster or office shouldnt be criticized because an EF-5 happened on a day that was "only" a MDT risk. The weather will always do what it wants, not what we think is going to happen. Now if the forecaster said all would be sunny and and well that day....i could see that. Severe storms and tornadoes were in the forecast. Watches and warnings were issued. How severe the event is usually isnt known until live reports start coming in either during or after the event.

Unless Im missing something I would think a TE would be issued AFTER a tornado hits or devastates a populated area to call more emergency personel to the area.

On 10-18-07 Chad Cowan, Matt Fischer and I were right behind the EF-3 that tore through Nappanee, IN. A tornado emergency was issued and emergency personal started arriving one after another. To me it would have been silly to issue one before this happens but thats just me.

 

[Jeff Richardson]

Deciding whether to "hit the panic button" and go with a Tornado Emergency carries a heavy weight. I can clearly see why the mention of a Tornado Emergency would be used in situations such as the OKC metro (May '99) or Greensburg, KS (May '07) when a tornado of potentially violent intensity is approaching a populated area. On the other hand, last May a cluster of severe thunderstorms moved through the Tulsa metro area around 7:00 p.m. A local AM radio station renowned for their excellent news/weather coverage was preempting syndicated programming with a "Tornado Emergency" which turned out to be a EF-0 tornado doing minor damage in a Tulsa suburb. We were under a tornado watch, but it wasn't a PDS situation. In this case, I think the Tulsa NWS was correct in issuing a tornado warning for this particular cell which was rotating, but feel the one media source in question was either out for ratings or had a particularly sadistic streak to their live reporting that night. This example may stray a bit from the original post, but I thought it might be of interest to share a particular situation where media, probably of their own accord, stepped much too far out of bounds and lit the fuse under the hype bomb.

 

[Mike Smith]

I urge anyone interested in the TE topic to read the lengthy comments available via the link in Danny's (#2) post above. It covers both sides of the topic very well.