Why no tornadoes this year???

[mcwell]

Forgive my lack of knowledge, just curious as to why there are so few tornadoes this year. Judging by what I've heard, March and April came in significantly lower than average. Is this due to the extreme cold causing so much snow in the upper Midwest? El Niño? Lack of gulf moisture? Please help a novice understand! And, do the extended models show any change in the weather patterns? (I'm living in Michigan and we're still waiting for Spring!!!)

Thanks for any input!

Mark

 

[Skip Talbot]

Yes, it's the combination of weather patterns we've been experiencing. The moisture scouring cold fronts and persistence of colder air being the main culprits lately. Others will cite the negative North Atlantic Oscillation index and Omega block we had coming into the season. We're less than a third of the way through the conventional plains severe weather season (it hasn't even begun for you in Michigan), and the season could easily come around. One third of chase season might be a dud, but some of the biggest years had a quiet April with a big May and June. I'll leave the crystal ball fortune telling of what the rest of the season will bring to others.

 

[Matt Hunt]

I'm certainly no expert, but I'll give my thoughts. The cold does have something to do with it. Mainly that almost weekly it seems there is a crashing cold front that extends all the way to the gulf, and depletes basically the entire CONUS of adequate moisture. Before that can be built back up, another cold front comes crashing down. With the most recent setup, the upper level trough was too far behind the surface low, at least here in the midwest on what was supposed to be a big day, and turned out to be a dud. I have yet to really see a good strong low level jet on any setup this year. I don't really know what affects the jet stream. From what I've heard, the temps in the Gulf are normal, not sure about the Atlantic & Pacific.

 

[Andy Wehrle]

The upper level trough and associated strong wind shear lagging behind the warm sector is a big one. That looks to continue to be an issue with upcoming patterns. 00z GFS 120 hour surface dewpoint/MSLP map looks very interesting from Oklahoma to Wisconsin until you look at the 500 mb wind/height map and see any southwesterly wind stronger than 30 kt well behind the cold front.

Of course things like that can change, but it just doesn't look too promising.

 

[Paul Knightley]

The entire northern hemisphere circulation has been very blocked of late. Indeed, since around 2007 blocking has become quite apparent at times. We've had some very cold winters over here, and cool, wet summers. The NAO was very negative during March this year - I think the NAO is really a local extension of the Arctic Oscillation, which has also been negative.

Of course, some blocking situations will lead to a western trough/eastern ridge set-up which persists, in the mean, for quite a long time (e.g. 2011). Other times, the blocking will assume a different regime - I suspect sea temps in the N Pacific modulate this to some degree.

The big question is, of course, why should high latitude blocking be more apparent? One reasonable hypothesis has to do with the huge decline in Arctic sea ice in the last 30 years, which in turn is due to warming in the Arctic; this then allows feedback to warm the Arctic further. A warmer Arctic should mean a weak jet stream - a weaker jet stream should mean more 'blockiness'. The downward trend in ice shows no sign of letting up, so perhaps we should expect more blocked patterns in the years to come - a big discussion point!

 

[STexan]

I think it's due to all of the government drone activity across much of the continental USA and the use of bio-fuels