Severe weather: Was it a tornado?

Source: 9Reports viewer submission
Source: 9Reports viewer submission

BATON ROUGE, LA (WAFB) - Saturday's severe-weather outbreak (June 4, 2011) came with several neighborhood reports of possible tornadic activity -- 9REPORTS.com even received one snapshot from the Zachary area that certainly had the look.

As of Sunday afternoon, there was no supporting evidence of a tornado anywhere within the greater Baton Rouge metro area during Saturday afternoon's busy weather. So, for the record books, the issue is probably closed: no tornado. But …

Over the years I've learned that more often than not, the wind damage we experience in our viewing area is due to straight-line winds: winds that rapidly descend out of thunderstorms and spread outwards when they hit the ground. These winds can be just as destructive as tornadoes, and often produce a broader path of destruction.

On the other hand, I've also learned that we probably get a number of small, short-lived twisters that don't show up clearly on Doppler radar. In fact, they may not really show up at all. Yes, in some cases, a tornado goes "unconfirmed," mainly because there is just not enough evidence for positive confirmation by the National Weather Service (NWS). Remember, we can say this or that, but it the NWS that has the final say when it comes to "was it or wasn't it?"

In a few instances over the years, I've also learned (sometimes the hard way!) not to argue when one of my fellow south Louisiana residents says, "Jay it was a tornado, and I don't care what that $%#@& radar says!"

On the face-value of it, wind-damage is damage, regardless of the cause. Any good weather scientist will tell you that tornado activity is under-counted, especially in less populated, rural areas -- so some of the wind damage reported on the news may indeed be tornadic damage, just not CONFIRMED tornado damage.

There's just something 'special' about claiming that it was a twister. It gets our blood up, not unlike the reaction I see in people when a tropical system enters the Gulf. In south Louisiana, we are ALL weather experts of one degree or another, particularly when it comes to severe weather!. I know that some of my insurance friends will emphatically deny this, but the "T" word gets a few of them jumping just a little bit quicker! (Agents, save the unflattering e-mails -- you know what I mean!)

Okay, so let's take a quick look at tornado 'climatology' for our area.

For tornado history and statistics, the best resource is the National Climatic Data Center (NCDC) archives. I ran a search on NCDC's "Storm Events" archive, which dates back to 1950. I limited the search to East Baton Rouge (EBR) Parish. Why? Mainly because that's where the denser population is for our viewing area -- and the more people, the less likely a tornado will go unreported. (And yes, you've got me: doing it for the entire viewing area would have taken me twenty times longer, at least!)

We need to remember that it wasn't until the 1970s that the NWS started SERIOUS tornado record-keeping and verification. We also need to consider two additional points:

- funnels aren't tornadoes and don't get archived, and

- what doesn't get reported doesn't get archived.

Given our caveat, here are some points determined from the NCDC archive:

- There have been 34 confirmed tornadoes in EBR Parish since 1950, with 27 reported for the period 1971-2011 (the 'better' recording period).

- Fortunately, there is only one tornado-related fatality on record for EBR Parish, in Zachary (06/07/2001). By comparison, there have been 3 EBR lightning fatalities in just the past 6 years.

- Of all EBR tornadoes, only three have been rated as 'F3' tornadoes, with no 'F4' or 'F5' events. (The F2-F5 range for EBR tornadoes is probably reliable through the entire archive period back to 1950; big tornadoes are unlikely to go undetected and unconfirmed.)

- 9 of the 27 EBR twisters (since 1971) 'hit' between 9PM-6AM: in the dark and during sleep hours, the most likely time to catch residents unaware. This includes the Zachary fatality, which occurred at 5:24AM (06/07/2001)

Probably the best historical example of a metro BR area tornado outbreak is the morning event of June 8, 1989. Over the course of roughly two hours (between about 5:00 and 7:00 AM), there were two confirmed touchdowns in EBR Parish and a total of a dozen touchdowns recorded across an area extending from Iberville to Tangipahoa parishes. In the end:

... two fatalities (Iberville Parish) and nearly 100 reported injuries over 5 parishes (58 in EBR Parish)

... over $11 million in estimated damages (1989 dollars)

For the state as a whole, Louisiana averages roughly 25-30 tornadoes each year, but the year-by-year numbers vary wildly, ranging from under 10 to nearly 80. Peak activity, statewide, comes in April and May, with those two months accounting for roughly one-third of all tornadoes. But twisters have occurred in every month.

For south Louisiana, possibly the biggest threat for tornadic development -- and sometimes forgotten -- is the spawning of tornadoes during tropical events. The best, and most recent, examples came during 2008's hurricanes GUSTAV and IKE, which combined to generate something on the order of three dozen south Louisiana tornadoes. Indeed, the Zachary fatality in June 2001 was linked to weather spawned by the mega-rainmaker Allison

On another point: Saturday's eruption of severe weather is just another indicator of the value of having a NOAA Weather Radio, Contrary to the opinion of some, properly functioning, properly programmed NOAA Weather Radios save lives. Don't take my word for it: ask the NWS, ask your local, parish or state emergency management officials, ask your local fire department.

Take Saturday's event: how many of you were in front of the TV on a Saturday afternoon? But an alarm from your NOAA Weather Radio would have alerted you to the developing weather situation and helped you to make timely decisions. For a few bucks, I think it's worthwhile. Just think about it …

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