What Caused All Of The Tornado Outbreaks In The Usa?

[Backtrack]

Just wondering if anyone can explain why so many tornadoes have formed in the USA this year.

Was it due to a rare weather system?

[Gray-Wolf]

Seems another 'controversial topic at present?

It is irresponsible not to mention climate change.

…

The environment in which all of these storms and the tornadoes are occurring has changed from human influences

(global warming). Tornadoes come from thunderstorms in a wind shear environment. This occurs east of the Rockies more than anywhere else in the world. The wind shear is from southerly (SE, S or SW) flow from the Gulf overlaid by westerlies aloft that have come over the Rockies. That wind shear can be converted to rotation. The basic driver of thunderstorms is the instability in the atmosphere: warm moist air at low levels with drier air aloft. With global warming the low level air is warm and moister and there is more energy available to fuel all of these storms and increase the buoyancy of the air so that thunderstorms are strong. There is no clear research on changes in shear related to global warming. On average the low level air is 1 deg F and 4 percent moister than in the 1970s.

From;

http://wonkroom.thin...onsible-denial/

I'd mooted worries in the past that more direct exchanges with the tropics/Arctic could lead to 'extreme' weather events in the N.Hemisphere and I still feel that this is a distinct possibility? The late cold across the N. US may well have had an impact in the ferocity of this storm system (along with the high

SST

's in the Gulf/Caribbean) but as the above points out if we have higher temps and more available moisture then the potential is there for bigger,stronger storms.

I'm sure this will not be universally accepted though!

EDIT: As for a 'rare event' folk are pointing back to another devastating storm system back in the 20thC so we will need to wait and see if this type of event starts to increase in it's occurance.

[chionomaniac]

These types of events are always more common in a declining La Nina ( aided and abetted by the state of the GWO ) and a set of circumstances all came 'right' to produce a large number of long tracked powerful tornados. I don't think global warming caused them at all.

[PersianPaladin]

Seems another 'controversial topic at present?

It is irresponsible not to mention climate change.

…

The environment in which all of these storms and the tornadoes are occurring has changed from human influences

(global warming). Tornadoes come from thunderstorms in a wind shear environment. This occurs east of the Rockies more than anywhere else in the world. The wind shear is from southerly (SE, S or SW) flow from the Gulf overlaid by westerlies aloft that have come over the Rockies. That wind shear can be converted to rotation. The basic driver of thunderstorms is the instability in the atmosphere: warm moist air at low levels with drier air aloft. With global warming the low level air is warm and moister and there is more energy available to fuel all of these storms and increase the buoyancy of the air so that thunderstorms are strong. There is no clear research on changes in shear related to global warming. On average the low level air is 1 deg F and 4 percent moister than in the 1970s.

From;

http://wonkroom.thin...onsible-denial/

I'd mooted worries in the past that more direct exchanges with the tropics/Arctic could lead to 'extreme' weather events in the N.Hemisphere and I still feel that this is a distinct possibility? The late cold across the N. US may well have had an impact in the ferocity of this storm system (along with the high

SST

's in the Gulf/Caribbean) but as the above points out if we have higher temps and more available moisture then the potential is there for bigger,stronger storms.

I'm sure this will not be universally accepted though!

EDIT: As for a 'rare event' folk are pointing back to another devastating storm system back in the 20thC so we will need to wait and see if this type of event starts to increase in it's occurance.

Nope.

Source:-

http://lwf.ncdc.noaa.gov/img/climate/research/tornado/tornadotrend.jpg

[Nick F]

I think La Nina maybe having quite a big influence on creating the rather active severe storm pattern over the US this April, convective activity over the Tropics has in turn been influencing the jet stream downstream across the USA - where an usually strong jet has been digging quite far south across the southern States. Very warm moist air has been drawn at the surface from the Gulf of Mexico across the Deep South while the strong westerly jet aloft together with a change in wind direction towards the surface has created strong vertical shear which has allowed strong thunderstorms to spawn the deadly tornadoes.

La Nina was also present during the historic highly active tornado seasons of 1974 and 1999. Though La Nina is not always present during some other active seasons, but tends to be a major influence in big outbreaks.

Global warming may have an influence in increasing the moisture content and warmth of the air across some parts of the world like the Gulf States, warm moist air of course the key ingredient for severe storms and tornadoes. And this April may have seen highest recorded tornadoes, though 1974 is up there too for tornado counts - depending on what period of days one uses.

[NL]

Heres an analysis of the 27th April outbreak, seems that all the optimum parameters were in place.

http://www.severestudios.com/april-27th-outbreak-meteorological-analysis

[johnholmes]

a very very simple explanation would be-the exceptionally cold upper vortex over winter and it being very slow to break down. Couple that with the, rather earlier than usual, bringing in somewhat colder air than normal from the north west, a flow of very warm very moist air off the Gulf, developing the jet more than normally and basic meteorology follows, or am I being too simplistic?

[Coast]

Here's what Joe Bastardi has to say in the linked Fox video:

http://video.foxbusiness.com/v/4667910/what-is-causing-the-spike-in-deadly-tornadoes/

Here is what he has to say about May:

http://video.foxbusiness.com/v/4667490/more-tornadoes-to-hit-south-in-may/?playlist_id=87185

[PersianPaladin]

Here's what Joe laminate floori has to say in the linked Fox video:

http://video.foxbusi...adly-tornadoes/

Here is what he has to say about May:

http://video.foxbusi...aylist_id=87185

I like how the forum allows you to say his name now

(but not me haha)

[Mesoscale]

Source:-

http://lwf.ncdc.noaa...ornadotrend.jpg

Strange pattern there, looks as if the amount of violent tornados has been falling in the last 20 years.

Joe has alot passion for this and he really knows what hes talking about.

[johnholmes]

Here's what Joe laminate floori has to say in the linked Fox video:

http://video.foxbusi...adly-tornadoes/

Here is what he has to say about May:

http://video.foxbusi...aylist_id=87185

I 'think' essentially he said much the same as I posted above the link C?

[Coast]

I 'think' essentially he said much the same as I posted above the link C?

Yep, I'm not sure who said it first, but you are both indicating the same thing!

[onlyME]

I think the right weather pattern created that much outbreaks.

Jetstream which is wobbling through USA and bringing cold and warm outbreaks and mixing the masses of air leads to atmospheric instability which is favorable for thunderstorms.