Volcanic eruptions and potential impact on severe weather

[Vicky Redwood]

Is anyone able to explain the reasons why it is thought that volcanic eruptions might have an impact on severe weather? Just picking this up from Mount Redoubt being mentioned in a thread and its potential interference with the 2009 chase season.

Any links to any research / informed discussions would be appreciated for both sides of the story please.

 

[Andrew Ryan]

I don't know of any studies about that connection between volcanic eruptions and severe weather/tornadoes. I think people fear that after the eruption, the ash will limit the amount of solar radiation for a couple of months. This would cause cooler temperatures, when warm temperatures (and solar radiation) are needed for severe weather.

But we will have to wait and see how (if this eruption occurs) this will effect the weather patterns.

 

[Andrew McDonald]

I'm pretty sure the eruption of Mt Pinatubo in the Phillipines (SE Asia) in the early 90's (June 1991) reduced average global temperatures by about 0.5 degrees celcius (0.9f) - Wikipedia. Given that this wouldn't have affected the main severe weather months in the US (May/June), if you take a very simplistic approach and look at the number of tornadoes in 1992, May saw some pretty low numbers (137) but June picked up with 399. April was also pretty low with just 53 tornadoes. Whether this was, in any way, related to the eruption of Mt Pinatubo, who knows?

Rather than looking at tornado numbers specifically, if you consider the potential impacts of lower surface temperatures arising from an eruptions ipmact on solar radiation, there are a number of possibilities. You could see lower instability levels, however, on the other hand, lower air temperatures could see smaller T/Td spreads which in turn could result in more tornadoes. There are many other possible outcomes. The GoM may not warm up as much and thus air coming up from the gulf could be on the cooler side. So many possibilities. I'd still chase unless the whole of the US was blanketed in a cirrus-like ash cloud.

 

[Richard Dickson]

I understand the ash rising to tremendous heights and possibly forming layers to block solar radiation thus cooling the atmosphere. Wouldn't that same ash also contribute more condensation nuclei as it descended into lower elevations and therefore create more opportunity for moisture to help fuel any storms if the rest of the severe storm making criteria was present? Being a 'wrong bettor' at the craps table, I think there might be an increase in severe weather after an eruption.