Join us below at 1 P.M. Eastern time on Tuesday, October 30 for a live 30-minute online chat with climate scientist Noah Diffenbaugh of Stanford University, who will discuss Sandy--the tropical cyclone that has caused 20 deaths and left more than seven million people in the U.S. Northeast without power. Diffenbaugh will answer questions about the storm as well as the role of climate change in severe storms and this storm.  We invite you to post chat questions in advance in the comments below.

CHAT TRANSCRIPT

Lloyd
Welcome to the Scientific American chat. We'll be live for the next 30 minutes w/Stanford University climate scientist Noah S. Diffenbaugh. Diffenbaugh is an expert on climate modeling and prediction.

Lloyd
I'm Robin Lloyd, Scientific American's news editor. We welcome questions from all of you participating in this chat.

Diffenbaugh
Hi everyone! I'm excited to join the discussion!

Lloyd
Dr. Diffenbaugh, how surprised were you by the intensity of this storm? Has your research done anything to predict such intensity?

Diffenbaugh
This is certainly a rare storm, largely because of the co-occurrence of a tropical and extratropical storm. The co-occurrence is what is so rare. That co-occurrence is really a result of variability in the atmosphere and ocean.

Lloyd
So the extratropical was the front that came down from the Arctic? And the tropical storm was the one that came up from the south via the Caribbean?

Diffenbaugh
Yes, the tropical storm was Sandy (now 'post-tropical storm Sandy').

Lloyd
Why was Sandy such a huge storm?

Diffenbaugh
The extra-tropical storm coming 'down' from Canada interacted with the tropical storm to 'steer' the tropical storm. Here is a nice discussion by Prof. Adam Sobel of Columbia: http://bit.ly/TLbDdo

Diffenbaugh
There is also a high pressure center over the North Atlantic interacting. My view is that this storm can teach us a lot about the vulnerability of people and ecosystems to severe storms and also about the physics of these storms because we have a lot of instrumentation now.

But in terms of the frequency of these kinds of storms, we have strong evidence that storm surge will increase (on average) with sea level rise. We also have strong evidence that the precipitation intensity is likely to increase with global warming. But whether global warming will cause more of these 'perfect' storms is not something that we know.

Josue Viv
What made NHC decide a couple hours before landfall that this was no longer a tropical system, even though it still had a warm core?

Diffenbaugh
The hurricane scale is based on the physical properties, not the expected damage. A lower category hurricane can cause severe damage, particularly if it strikes a vulnerable location. So once the physical properties are not on the scale, the storm is 'downgraded.’

Markfischetti
Some scientists say the storm 'down' from Canada was Jet Stream influenced by NAO, or 'blocking pattern. Comments?

Lloyd
Welcome, Mark Fischetti. Mark is our senior editor for energy/sustainability at Scientific American. Good question re: NAO.

Diffenbaugh
Markfischetti: Yes, the 'long wave pattern' influences extratropical storm track. The pattern of high and low pressure in the atmosphere is what creates that long wave pattern, and the pressure pattern in influenced by the NAO. This storm is a case where the particular configuration of the atmospheric pressure played a key role in the storm turning westward and making landfall in the Northeast.

3 Comments

1. 1. pmagn 12:32 PM 10/30/12

   Test

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2. 2. pmagn 01:14 PM 10/30/12

   I just had a thought which I am going to throw out here... Can super storms like this generate low frequency seismic waves or pressure pulses which trigger earthquakes locally or remotely (for example on the west coast)?
   
   This could be one mechanism which is involved when we get sudden climate change like GW as it has been noted in the geological record that earthquakes, volcanoes and seismic activity does increase with the changing climate.

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3. 3. olgalg 04:54 PM 10/30/12

   Hey guys. I missed the hangout. I have yet to see it come through on your G+ page. If you could share the link...that would be amazing. I'd love to learn about the science behind the storm.
   
   Thanks!
   
   Olga

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