30 October 2013
My friend Bob Henson at the National Center for Atmospheric Research has a great piece on Atmos News about Sandy today. NCAR has published some amazing high-resolution model runs of Sandy, and in some ways Sandy actually behaved like a tornadic super-cell. The model runs show that as Sandy approached a cold front, it tilted tubes of rotation air from the horizontal to the vertical. This same thing happens in super-cells, and meteorologists measure a term called storm relative helicity to rate the magnitude of this conversion.
The video below shows the cool air at the surface rising and releasing heat as it climbs into the storm. Sandy was a hybrid storm, acting like an intense nor’easter down low, but having a core of warm air aloft. As water condenses from vapor to liquid it releases heat and warms the air. Think of it this way, it takes heat to boil a pot of water dry, but when that steam condenses back to liquid, all that heat to boil it away is released back.
Yes indeed, energy is conserved.
Below the first, is another video of Sandy made with a model running at a resolution of 500 meters! This model took 58 hours to run on the
new NCAR Univ. of Illinois Cray supercomputer! The same model I use each day to forecast was used, but it runs at 12KM and 4KM resolution.
To run the model at a higher resolution would not give us a forecast for tomorrow until the day after, or longer! Running these high-resolution models after the fact may not help with forecasting Sandy, but it will help us to better forecast the next one.
There is no doubt that the rising sea level made Sandy worse. I think in many ways it was the first real reminder from Mother Nature that climate change is not just something that will affect our grand children, but is already changing our planet. A storm like Sandy will be notably worse in just 30 years. How we rebuild on the coastline now, will determine how many people lose their homes and livelihoods next time.
More on Sandy and more on the high-resolution model runs from Bob Henson at NCAR here. It truly is amazing how well we can model the atmosphere now compared to 30 years ago. When we have computers that can run at 500 meter resolution and produce a 48 hour forecast in 3-4 hours, then forecasting will indeed have entered a new age.