8.6.07

SOUNDING THE ALARM. State Line commentator Jiblog claims he's not thinking about Alexandra Steele out of her beachwear.
I'm trying to coin a term. Meteorology porn is my preferred, but I'm cool with meteorological masturbation, too. Either term would apply to the situation we experienced today in Wisconsin. For 48 hours, meteorologists have been in heat over a strong weather system heading this way that they expected to spawn widespread severe weather across the state today. As this afternoon got closer, they seemed to approach climax, and the voyeuristic media was whipped into an apocalyptic frenzy. Unfortunately for both, it was largely much ado about nothing. A few areas got some nasty storms, but this was ultimately no worse than any typical June storm system. The weather forecasting needs an embarrassing term for their behavior on days like today, and I'd be happy to tag them with either of the ones above.
(Via Owen at Boots and Sabers.)

The expectations that morning were for something spectacular. In north central Wisconsin, there was serious property damage. In the State Line, it was pretty much the weather reporters getting worked up over very little.

The meteorologist at Northern Illinois University, Gilbert Sebenste, added a lengthy explanation of what happened to his daily weather forecast. As the forecast page is updated daily, I'm taking the liberty of quoting the statement in full.

On Wednesday just after noon, I went with my 5th high risk of severe that I have ever posted in my nearly 9 years at NIU. I don't post those lightly, as it can and does cause great concern. But there was certainly a valid concern for it: one of the strongest, and possibly THE strongest, low pressure system for so late in the season was going to move into northern Illinois Thursday evening (it's even tough to get a system this strong in winter). To say all the ingredients were there for a severe weather outbreak was understating the obvious: a strong cold front and dryline acting as a focus for low-level lift to help initiate storms;plenty of low level moisture; unheard of wind speed shear for this time of year; sunshine to warm things up; and adequate directional shear for tornadoes.

It wasn't just me thinking this, either. As Thursday morning dawned, the Storm Prediction Center was going for a high risk as well. By late morning, they had increased their damaging wind probability for DeKalb to 60%, large hail to 35%, and tornado to 15%, with a 10% or greater chance of a "strong" event, featuring softball-sized hail, 80 to 90 MPH winds, and tornadoes that tear communities to shreds for our area.

And the local National Weather Service office in Romeoville was solidly on board with this idea as well. In fact, they put out unprecedented statements that flew across our weather wires and into email inboxes across campuses, stating that 80-90 MPH winds were expected from the severe storms with high probability. They even had two live reports on NOAA All-Hazards Radio, at 11 AM and 4 PM...that's never been done before. They had conference calls with all emergency management officials in northern Illinois and northwest Indiana. In Wisconsin, most grade/high schools declared a half-day and had students go home at noon or 2 PM, the first time that has ever happened anywhere in the country, as far as I know, to that extent. Businesses and even staff at the Iowa Welcome Center in Bettendorf posted signs on locked doors that essentially said: "we are outta here!". The 10 hour-long tornado watch that was issued for DeKalb Thursday afternoon noted that this was a "particularly dangerous situation", wording generally reserved for only the most intense outbreaks expected. And while 180+ severe weather reports were received, including 14 tornado reports, most of the damage was minor. In fact, much of the damage in northern Illinois that occurred was not from thunderstorms, but from the storm system's intense winds. And by noon, supercells were already developing across central Iowa, with tornado warnings already out. And we in the forecaster trench just had the same thought: "here we go!".

So what went wrong?

Obviously, all the ingredients were there. And to be honest, seeing discussions with professors and meteorologists across the country, it's difficult to pinpoint an answer. But the problems were so difficult to see that it certainly wasn't seen in forecasts or in real-time until late in the afternoon.

Three things have come up which MAY explain why it wasn't as bad as expected. First, the National Weather Service in the Quad Cities was asked to launch weather balloons frequently, and they did. They had balloons up at 1 PM, 3 PM and 7 PM. What one sees in those soundings is that warmer air aloft came in and helped "cap" the activity as it moved away from the cold front. Second, the front itself was slow to move. Because of the incredibly strong winds, storms that formed on the cold front or dryline moved away from their low level source of lift very quickly, at 60 MPH or faster. As they formed, they became severe very quickly. But when they quickly moved away from their low level forcing source, they started to shrivel and die. Storm chasers in Iowa noted this yesterday.

Finally, the main upper lift went north into northern Wisconsin and didn't leave much along the rest of the front. It should have been enough, but it obviously wasn't. As a result, the most severe activity DID occur in northern and central Wisconsin, as videos showing softball-sized hail near the Wisconsin Dells and tornadoes seen between pine trees from frightened home camcorder owners in the area can attest.

That is not to say that if this scenario ever happens again, it could be much worse. Every storm system, regardless of its intensity, can produce surprises...this one kind of produced a "good" surprise by not being as bad as we thought it would be. But I have no regrets about pulling the high risk trigger, and neither did anyone else. When you have a stick of dynamite with a lit fuse, always assume the worst unless things turn out not as bad as they could have been. And it also means that as forecasters, we aren't perfect. Believe me, we don't like to watch our forecasts go down in flames. We don't like to frighten or scare people. Our technology, our data, is far from perfect. And forecasters are human; our knowledge of what goes on above our heads is limited. Grant us the grace when it rains on your parade...and when it doesn't. We'll be learning from this one, to be sure...as we do with many systems that move across our area each year.

Until then, I'm just glad that my community is still in one piece. A few up in Wisconsin were definitely not as fortunate, and my thoughts and prayers go out to them.

Put briefly, all the conditions were in place for a widespread weather event. No doubt there will be material for several scholarly articles based on the forecast and the events. But before one criticizes the weather service for being too cautious, one ought think about a loss function. Suppose the weather service had missed the indicators of a severe storm, and large numbers of people died. The Children's Blizzard tells the tale of one such nineteenth-century omission and the recriminations that followed.

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