Midwest 'Superstorm' Reveals Bulked Up Atmosphere

Even as tornado watches remain in effect, meteorologists are shaking their heads at the "Superstorm" that savaged the Midwest Tuesday, spawning twisters and other damaging winds and breaking records for its hurricane-like intensity.

The middle latitudes of the Northern Hemisphere are often a meteorological battleground this time of year between the declining forces of the summer's warmth and the resurgent cold of impending winter, just as spring often sees violent clashes of opposing seasonal patterns.But what happened this week was different in magnitude if not in kind.



Crossing Minnesota late Monday and Tuesday, low atmospheric pressure sank to 955 millibars -- the kind of intensity readings that forecasters are more accustomed to seeing in the eyes of hurricanes.
Meteorologist Larry Cosgrove in Houston said that unofficially "this disturbance may have sported the lowest barometric pressure in recorded history."

Meteorologist Jeff Masters at Weather Underground said the pressure reading was "the lowest pressure ever measured anywhere in the continental United States aside from the Atlantic Coast."

Masters observed something else:

"Yesterday's superstorm is reminiscent of the amazing low pressures reached earlier this year (Jan. 19-22) in the West, where virtually every site in California, Nevada, Utah, Arizona, southern Oregon, and southern Idaho -- about 10-15 percent of the U.S. land area -- broke their lowest on record pressure readings..."

"We've now had two remarkable extratropical storms this year in the U.S. that have smashed all-time low pressure records across a large portion of the counter. Is this a sign that these type of storms may be getting stronger. Well, there is evidence that wintertime extratropical storms have grown in intensity in the Pacific, Arctic, and Great Lakes in recent decades."

Earlier this year, Masters wrote that modeling studies simulating an atmosphere with greater concentrations of greenhouse gases "predict a future with fewer total winter storms, but a greater number of intense storms."

IMAGE: Red Cross workers walk away from a barn that was lifted off its foundation by a tornado Oct. 26, 2010, in Mount Pleasant, Wis. Credit: AP