Wednesday, May 28, 2008

Why ask why?

So the question of the day appeared to be: Why have so many tornado's occurred this year. As is typical with the hype, the "answers" given were not surprising. Early season, "rare" tornado outbreaks upped the numbers. The La Nina event was also cited as playing a role in the location of the jet stream.

Severe storms require instability and vertical wind shear AND they need to be co-located if only for a few hours usually in the late afternoon. The other ingredient in this concoction is the cap, or lid. This lid serves a dual purpose: it prevents the release of this instability so naturally the instability increases as the water vapor mixing ratio and surface temperature increases AND it helps determine downdraft characteristics. This latter part is not so well understood. I will blog on that some other time.

Tornado outbreaks occur in dynamically active patterns associated with a large scale or perhaps shorter trough (low pressure). With troughs come developing fronts and the clash of air masses OR simply different air masses. Since 2005 the moisture and dynamics have not been often colocated and when the dynamics appear to be present the moisture is missing in action. This has made chasing storms rather difficult, and thus observing tornado's difficult. More than a few storm chasers, myself included, have felt disenfranchised by the atmosphere. Until this year. The moisture is plentiful. The dynamics appear in spurts regularly.

I also must say that tornado season appears to be rather consistent about being inconsistent. Some years April seems more active than May or May more active June, but I doubt there is a trend there.

The death toll this year is not surprisingly high. Rather we should remark how low the death toll has been in recent memory. Tornado's are powerful and no matter the warning lead time, someone somewhere will be surprised. We are fortunate that the country is not one giant piece of habitated concrete otherwise tornado's would almost always kill someone. The real test of our science is to sample many tornado's with radar, get good surface wind speed and acceleration measurements, and correlate that data to observed damage.

The problem with damage however is that not every house is built well, or new, or has the same code. Damage in this case is relative. This is why Tim Marshall and many others led the charge for a new tornado rating scale. It was disappointing to not hear anyone speak about housing construction when the new scale went into effect, the news widely reported that wind speeds were lower because we knew more. True. We do know more ... about how crappy some homes were built (find any number of articles on Hurricane Andrew), how old others were, and how powerful some tornado can be. But we still need to know more so mitigation of damage leads to saving lives too.

Which leads back to why have so many tornado's occurred this year. There are more people to observe them, even in rural areas. There are more storm chasers. We are more well informed about storm potential. More people are paying attention, especially small town EM's. I was amazed that Parkersberg had just recently installed another siren. After the destruction in IA in November 2005 near Ames, IA and I think the F3's in 2004 or 2003 in IA, every small town should find the money or being given federal help to get a siren. Maybe the sirens will work, maybe they wont. Who cares. If 1 life was saved, it was worth it.