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Susan Kieffer can be contacted at s1kieffer at gmail.com

Wednesday, February 2, 2011

Monster storms: Australia and U.S.

Images compiled from MODIS on NASA's Terra satellite

January 31, 2011
In the previous post, I discussed the huge cyclone in Australia, but I thought our readers would be interested in comparing and contrasting with what is going on in the US this week.  The images aren't directly comparable because they are taken with different instruments, and the destructive potential is in now way reflected by these maps, but "you get the message: these are big storms!"  The image at the left is the largest storm that has hit the U.S. since the 1950's. It's been affecting 30 states with snow, sleet, freezing rain and rain.  This image was compiled from three images, captured on Jan. 31 at 10:30, 12:05 p.m. and 1:45 p.m. Eastern Time to form the mosaic shown here.  Sensors did not collect data in the white gaps. More infomation is here.

Cyclone Yasi superposed on the USA
Factoid: A cyclone is an atmospheric system characterized by rapid inward circulation of air masses around a low-pressure center.  Cyclones circulate counterclockwise in the Northern Hemisphere, and clockwise in the Southern hemisphere. In the Atlantic, cyclones are called hurricanes; in the Pacific, typhoons.

In wondering about the size of storms, I (with help) found this Q and A on a NovaWednesdays with Dr. Marshall Shepherd of NASA Goddard Space Flight Center:

Q: Is there an upper size limit to how big hurricanes can get? Could there theoretically be a hurricane that is, say, twice or three or ten times the size of Katrina?

Q: Is there a upper size limit to how big hurricanes can get? Could there theoretically be a hurricane that is, say, twice or three or 10 times the size of Katrina?

Shepherd: There is likely an upper size limit on hurricanes before they become unstable, but I can't quote you a magic number as this would be a theoretical study that would have to be done with a model. Even with category 5 storms, we see a point at which they cannot sustain such intensity for long periods of time. The storm will go through various eyewall-replacement or other weakening processes. Additionally, the upper level wind environment and ocean surface temperature/roughness processes are so dynamic that nature has imposed a self-regulating mechanism on the storms.

1 comment:

Brian Davis said...

I wonder what Dr. Shepherd would think of hypercanes. True, they would require theoretically some very extreme conditions, and are anything but large (the eye is actually very small), but in some very real sense (*if* they can truly exist) they would certainly qualify as "bigger" in terms of wind speed for instance.