2008-02-05 DISC: TX / AR / MO / IL / KY / TN / MS

I'm writing this post in regards to the comments about whether anything can be done to mitigate deaths in tornadoes amongst residents living in less than fortress buildings. I've surveyed a number of tornadoes in the southeast US and in the Plain states. Honestly the only difference I've seen is that the southeast US tornadoes typically occurred at night and were fast moving leaving someone with little recourse but to 'ride it out'. The demographics were similar for where people lived. A lot of people live in modular homes in both regions.

So the question I ask is how much can a homeowner do to make his/her structure more survivable? I really don't know the answer to this question because there are so few studies available.

Recent code changes in hurricane zones require mobile homes to have more frequent anchorings (I think 4' on center) and straps around the metal frames. The Lady Lakes tornadoes took everything above the frames of these new mobile homes. IOW, the next weakness of the mobile homes was exploited by the tornadoes: the cheaply connected stud walls.

I'm sure the better anchored frames may have allowed lives to be saved. Any homeowner who anchors his/her frame better takes one step up the ladder of survivability. But if everything's taken off above the frame, survivability is not likely to be very good. However, I've documented damaged mobile homes reduced to one wall where the occupants survived because of that wall. I'm more confident that it may not take much to allow at least one wall standing. What if the same homeowner who beefed up the frame anchoring added clips to the mobile home load path? Clips cost a single $. Add 150 of them and ideally you could get a big boost in survivability for relatively little cost. Now it's not always that simple to retrofit because you have to get behind the walls but I think the idea has been made.

Even with $150 worth of clips installed and a well anchored frame, a mobile home isn't going to be the fortress a concrete house may be but it could give you two steps up the ladder of survivability. Maybe more walls would be left behind. For someone barely able to make ends meet, perhaps $150 and a little sweat equity isn't so daunting.

Jim
 
60 dead now apparently,according to SPC. Another death from the jackson county,al EF4. Its only Feb folks,and so far this year 66 deaths..
 
Rich Thompson said:
Brandon,I believe the national false alarm rate for tornado warnings is ~75% for counties. I've only seen statistics for Jackson MS for one year several years back, when 11 tornadoes occurred and 99 warnings were issued (these numbers might be off a little). The JAN probability of detection was 100%, but the false alarm rate was 89%. Or, only 11% of their tornado warnings were accompanied by a tornado report somewhere in the county. We'll have to see how that changes with the polygon warnings.Rich T.
Click to expand...
Hi Rich, calling it a false alarm rate (FAR) to me is inaccurate, at least with the respect to the Dopper radar. The reason, the Doppler detects mesocycones not tornadoes, that's always been its job and in that respect it has a very high success rate. Unfortunately when the original project was lobbied it was being sold for wind shear, correct. That was justified off Fujita's original work concerning aircraft safety, down bursts and commercial planes falling out of the sky. It wasn't just about saving lives, it was about general trust from the public about commercial flying. Of course now we have on board radar in the expensive aircraft. Voices started saying these Dopplers will protect us against tornadoes....I remember certain people trying to tell the truth, but they were drowned out. Thus the billions of dollars was spent to upgrade the most populated areas of the nation first, finally getting down to isolated areas like Goodland. In the rare cases when we do see a tornado on the end of the hook what we are actually seeing is the debris ball; again much larger than the typical tornado. Even with the new and more powerful radars coming on line how does one see a 100-150 meter wide event at 65 miles distant. That is pretty much what we are asking that piece of equipment to do. Frankly I don't think it's possible even before we consider (a) curvature of the earth and (b) the +.05 degree tilt for environmental safety. With respect to the Doppler seeing the mesocyclone, we know that's accurate and as chasers we can verify it's rotating. For example, how many times have you sat on a rotating mesocyclone for 1-2 hours before that supercell produced a tornado. Remember the Hill City event last season? The supercell sat in that area for how many hours before it finally produced a condensation funnel to ground, at least four, would that be a fair assessment? Meanwhile, the Goodland Doppler sees a potentially tornadic mesocyclone the whole time and warning after warning is issued, most counting as false alarms. I wish the public understood the relationship between what the radar is doing (correctly) vs true tornadogenesis. Armchair chasing on Feb 5th I watched a lone supercell take over from a cluster in far NE LA, it was the first supercell of the day. It move into SE AR and immediately spun up a strong meso. In fact it had meso signatures early on and base reflectivity showed a classic supercell configuration. Yet that storm as threatening as it was traveled for at least 100+ miles I bet, before starting to produce real tornadoes. As it moved north other cells formed and trained that supercell finally moving into the Memphis-western TN region. It was there when they really let loose with tornado after tornado. To not put the warning on such a cell early would be tantamount to duplicating the infamous Fort Smith event where hours of warnings were issued prior to the destruction in that city...with no warning. Some supercells produce tornadoes within 30-45 minutes, others wait hours, but in the end the tornadoes are just as strong.
 
Gene Moore said:
Hi Rich, calling it a false alarm rate (FAR) to me is inaccurate, at least with the respect to the Dopper radar. The reason, the Doppler detects mesocycones not tornadoes, that's always been its job and in that respect it has a very high success rate.
Click to expand...

But the job of the meteorologist is to take doppler data, combine with other sources, and issue a warning... The FAR ratings are not a rating of 88D algorithms - it's a rating of what the end user gets.

I don't think 88D was sold as a wind shear project - everyone back then felt that a large majority of mesocylclones resulted in tornadoes. I do recall at least 50% being given out - now we realize it's 5%
 
Brandon Clement said:
There were well over 1000 tornado warnings issued for this outbreak yet there were 70 reported tornadoes, many of these we are finding out were long tracked tornadoes and multiple reports for the same tornado. This means the NWS is getting 4-6% of the warnings right and this was on a historic outbreak were the storms were actually producing tornadoes.
Click to expand...

There were nowhere near 1000 tornado warnings issued during the outbreak. The total was a little over 200 tornado warnings from 16 NWSFO's.

http://www.easternuswx.com/bb/index.php?s=&showtopic=155131&view=findpost&p=2507699

As for the central MS having a high FAR, well I think many tornado enthusiasts know that JAN issues far more tornado warnings for marginal/weak storms than almost all other WFO's in the country.
 
Jim Tang said:
There were nowhere near 1000 tornado warnings issued during the outbreak. The total was a little over 200 tornado warnings from 16 NWSFO's.

http://www.easternuswx.com/bb/index.php?s=&showtopic=155131&view=findpost&p=2507699

As for the central MS having a high FAR, well I think many tornado enthusiasts know that JAN issues far more tornado warnings for marginal/weak storms than almost all other WFO's in the country.
Click to expand...


The numbers I provided were from sometime around 1999. They have probably changed some since then (just a single year), and I know JAN has experienced more active years than the one quoted (all 11 tornadoes were F0-F1, I think). I don't know that I'd call JAN the most aggressive TOR warning office in the nation, however.

Rich T.
 
Gene Moore said:
Hi Rich, calling it a false alarm rate (FAR) to me is inaccurate, at least with the respect to the Dopper radar. The reason, the Doppler detects mesocycones not tornadoes, that's always been its job and in that respect it has a very high success rate. Unfortunately when the original project was lobbied it was being sold for wind shear, correct. That was justified off Fujita's original work concerning aircraft safety, down bursts and commercial planes falling out of the sky. It wasn't just about saving lives, it was about general trust from the public about commercial flying. Of course now we have on board radar in the expensive aircraft. Voices started saying these Dopplers will protect us against tornadoes....I remember certain people trying to tell the truth, but they were drowned out. Thus the billions of dollars was spent to upgrade the most populated areas of the nation first, finally getting down to isolated areas like Goodland. In the rare cases when we do see a tornado on the end of the hook what we are actually seeing is the debris ball; again much larger than the typical tornado. Even with the new and more powerful radars coming on line how does one see a 100-150 meter wide event at 65 miles distant. That is pretty much what we are asking that piece of equipment to do. Frankly I don't think it's possible even before we consider (a) curvature of the earth and (b) the +.05 degree tilt for environmental safety. With respect to the Doppler seeing the mesocyclone, we know that's accurate and as chasers we can verify it's rotating. For example, how many times have you sat on a rotating mesocyclone for 1-2 hours before that supercell produced a tornado. Remember the Hill City event last season? The supercell sat in that area for how many hours before it finally produced a condensation funnel to ground, at least four, would that be a fair assessment? Meanwhile, the Goodland Doppler sees a potentially tornadic mesocyclone the whole time and warning after warning is issued, most counting as false alarms. I wish the public understood the relationship between what the radar is doing (correctly) vs true tornadogenesis. Armchair chasing on Feb 5th I watched a lone supercell take over from a cluster in far NE LA, it was the first supercell of the day. It move into SE AR and immediately spun up a strong meso. In fact it had meso signatures early on and base reflectivity showed a classic supercell configuration. Yet that storm as threatening as it was traveled for at least 100+ miles I bet, before starting to produce real tornadoes. As it moved north other cells formed and trained that supercell finally moving into the Memphis-western TN region. It was there when they really let loose with tornado after tornado. To not put the warning on such a cell early would be tantamount to duplicating the infamous Fort Smith event where hours of warnings were issued prior to the destruction in that city...with no warning. Some supercells produce tornadoes within 30-45 minutes, others wait hours, but in the end the tornadoes are just as strong.
Click to expand...

Gene,

I can't really speak for the motivations of the folks that started the whole WSR-88D project. However, by the time I joined the NWS in '92, the primary focus was on "20 minutes of lead time" for tornadoes. That's where our problems started.

The earlier Doppler radars were not collecting data unless a "big" day was expected, thus the early storm samples may have been biased toward high-end mesocyclones and tornadoes. Hence the old "50% of mesocyclones produce tornadoes" statistic. We've come to realize the fraction that produce tornadoes is much smaller, likely somewhere in the 10-20% range (depends on how you define a meso).

Gene is correct - the 88D almost never resolves an actual tornado, thus it's not fair to "blame" the radar for everything. In reality, the decision thresholds and situational awareness of the warning meteorologists play the biggest role in POD and FAR.

Rich T.
 
This thread is a great discussion of Tuesday's events. Thanks, everybody, for making it so interesting and informative to read! :)

Jason and I have returned from our damage survey of the single, long-tracked tornado that affected Pope County through Sharp County, Arkansas on Feb. 5th, 2008. We surveyed the damage path from Atkins, AR in Pope County, through Shirley, AR in Van Buren Co.

Unfortunately, daylight and roads available, coupled with extreme traffic congestion in Clinton did not allow us to follow the damage path of this tornado any further than approximately >10 miles northeast of Shirley, AR in Van Buren County and consequently this is where our own damage survey had to cease. We did not get to view the damage in the Mountain View/Zion/Highland areas.

Our preliminary impression of the damage by this tornado is somewhat lower than we had expected given the news reports etc. in the days preceding this one. There is, of course, a large amount of tree damage - however, about 85% of the tree damage we encountered was simply a case of the “blow-down”, there was a complete lack of denuded and debarked trees in all but a very select few cases. The majority of the trees we saw were shallow-rooted evergreen trees that had simply been blown over in their original place, with turf-ball still in place around the roots at base.

There were two or three instances along our survey journey that unearthed questionable high-end EF-3/low-end EF-4 damage to brick homes. One was in a rural setting southwest of Cleveland, AR, and the other was a foundation that was missing a home in Clinton, AR. We will have to review the photographic data that we collected prior to forming a firm opinion on the ratings these structures displayed, however. It does, however, seem very likely to us that this was one single tornado - given the frequency of tree damage encountered along many single track back roads that we ventured into. At various points in time road passage was difficult.

More later, including images.

KL
 
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Pretty remarkable tornado for sure

I went back on list of the long tracked tornadoes since 1950 and found one that may get the asterisk. According to Storm Data (March 1990), the C. Nebraska long tracked F4 tornado on March 13, 1990 had a 124 mile damage track. In contrast, Tom Grazulis' green book mentions this was 124 miles consisted of different "tornado family" members.

At any rate, its remarkable how a tremendous violent tornado can remain in such balance to create such a long damage track. This especially in a colder winter type severe wx setup with the main 850mb jet displaced over towards the Mississippi River and points eastward (where 0-3km SRH was shown to be well over 500 ms/s2 by early evening). The benefits and support were certainly there with the main 700/500mb wave pivoting the NW 1/3 of Arkansas and the 90-100 kts. of wind at 500mb. :rolleyes:
 
The only other recent extremely impressive tornado (with regard to path length) that comes to my mind is the Stockton MO tornado of 5-4-03, with a path length of ~83 miles. 120+ miles is unbelievable. The 00Z Little Rock sounding showed ~1800j/kg MLCAPE which was obviously more than sufficient amidst the strong environmental wind fields. The temp profile was also "cool" with a 3km deep moist layer and a relatively impressive 125j/kg 0-3km MLCAPE... not terribly dissimilar to the thermo environment on 5-04-03. Seems to me a lot of the nastiest tornadoes vastly prefer a cool profile rather than having a significant elevated mixed layer. (e.g. Greensburg)
 
Hey Brian,

That's interesting about that central NE storm with the 124 mile long track that may be one single tornado. I hadn't heard of that one - maybe I need to do some more research.

I'd edge away carefully from thinking that Tuesday's AR tornado maintained it's intensity for any significant length of time, however. It was certainly impressive to see a damage path continue uninterrupted for so far - but from our survey of the path today it was apparent that the vast majority of damage was in the EF-0 - EF-2 range. The track varied in width at several points - it was wide at Atkins, narrower at points northeast of there. Most notably however was the fact that - at points northeast of Atkins and southwest of Clinton, it was sometimes very hard to determine the damage path - the circulation appears to have got very diffuse and weak. It was still fairly wide - but the level of damage it was inflicting was greatly reduced compared to east of Atkins. Sometimes all we saw were some snapped twigs here and there. So - I would assert that this tornado went through several stages and morphs along it's path - and maybe have been multi-vortex in structure northeast of Atkins for a time. EF-4 damage is extremely hard to come by - as is EF-3. Mostly the tremendously long path consisted of nothing more than downed trees and sheet metal wrapped around fenceposts.

KL
 
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