Monday, May 20, 2013

Boiling over

Sometimes, it's not so thrilling to nail a forecast.

NOAA scientists predicted that the areas in the red boxes would experience tornadoes and the areas in the yellow boxes might experience tornadoes.  In preparation, geostationary weather satellites (the G in GOES stands for geostationary) were put in Super Rapid Scan* mode so that they could send down higher-resolution data in both spatial and temporal scales.

Hopefully, the faster scan and downlink rates bought people time to scramble to shelters and kept the casualty rates lower than they would have been without the precious few extra minutes of  warning.

Even though Scott Bachmier of the CIMSS Satellite Blog has been sequestered, his boss found some money to keep him blogging for public education.  He put together this incredible animation of Oklahoma on May 18, showing "overshooting" cloud tops.  In plain English, air parcels were tossed upwards with such tremendous force, their momentum carried them up above their thermodynamic stability level.  Watch this stereo animation.  The clouds literally boil over.

The animation for May 20 is similarly impressive.  In addition to the boiling behavior, look at the lines of waves emanating from the frontal region and extending to the southeast (bottom right) corners of the images.
That line of L's in the top color picture from Unisys (based on NOAA/NCEP predictions) stands for low pressure. That trough of low pressure is expected to remain stationary for several days and will continue to draw in warm, moist air from the gulf of Mexico--and generate tornadoes where they collide.

Imagine living through the devastation of the past three days in Oklahoma and knowing that you face three or more days of this.  How are you going to soothe your kids while not downplaying the very real danger?

USA Today put together a graphic overlay of the May 3, 1999 and May 20, 2013 tornadoes.

Is it just my imagination, or can you still see some of the scars of the 1999 tornado on the satellite image on this Google Map of Oklahoma tornado sites?

Perpetual drought and longer fire seasons in the southwest, longer tornado seasons in the midwest, longer hurricane seasons and more intense hurricanes in the southeast, and more nor'easter meets subtropical jet mega-snowstorms in the northeast are all signatures of a warming planet.  The physics of how a warmer overall global climate leads to an increase in the probability of these events is well understood.

* Animations such as these are possible only because images are scanned and beamed to earth every ~5 minutes.  Thus, each frame is taken about 5 minutes apart.  With satellite bandwidth, you have to rob Peter to pay Paul.  Imagery in the southern hemisphere was probably sacrificed for this.

When you think about it, it's incredible that photons fall on a detector out in space and then we get movies like this a little while later.


  1. That is some pretty scary stuff. It amazes me that people still choose to live there.

  2. Oh my goodness, I've just seen the news! That is a truly terrible storm!

  3. @Carolyn People don't choose to live in tornado alley in the same sense that people choose to live in a flood plain, earthquake fault or fire-prone corridor.

    Tornado alley covers a huge swath of the interior US, the flat midwest. The frontal lines move around so different areas are in extreme danger daily. Although some areas are more risky than others due to orientation of mountain ranges, the overall risk is shared by a remarkably large swath of our country.

    The flatness of the midwest that makes it such a good area for agriculture also make it prone to tornadoes. The great plains lower level jet that brings in the convective available potential energy (CAPE), also brings in the rain for crops.


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