A look at weather extremes and the big-picture climate connections.

Records Fall Across Country as Temperatures Soar

The weird winter of 2011-12 has given way to a truly odd March weather pattern, with a big dip, or "trough", in the jet stream out west, and a large ridge of high pressure in the East which is allowing warm air to flow from the South all the way up into Canada. Yesterday alone, 117 record daily high temperatures were set, along with 74 records for warm overnight low temperatures. This compares to just four daily cold high temperatures and two cold overnight low records.

More records are likely to be set during the next 7-to-10 days, especially from the Midwest to the Ohio Valley, Mid-Atlantic, and Northeast. These regions can expect high temperatures to run 20 to 30 degrees F above average for this time of year.

Daily high temperature records set or tied on March 12, 2012. Credit: NOAA/NCDC. Click on the image for a larger version.

In the New York City area, five of the six climate recording sites set high temperature records yesterday, including Central Park, La Guardia Airport, and Newark, NJ.  The high of 71°F in Central Park was enough to topple a daily record that had stood for more than a century. Records were also broken in Albany, NY and nearby areas, and even as far north as Burlington, VT and Bangor, ME.

While record-breaking temperatures may take a brief break for the next day or two, computer model projections show that unusually warm air will once again affect much of the country east of the Rocky Mountains from midweek this week through next week. From the Rockies westward, however, cool and stormy conditions are likely, as powerful storm systems bring mountain snow and valley rains to the Pacific Northwest, northern California, and intermountain West. This is great news for skiers as well as water managers, particularly in California where drought conditions have set in after a very dry winter.

Computer model projection for the 500mb height anomalies, valid on Wednesday, March 14. Credit: Penn State E-Wall. Click on the image for a larger version.

The computer model projection shown to the right shows an important indicator of how unusually mild the air is likely to be, based on the height of an atmospheric pressure surface, in this case the 500 millibar level. The average air pressure near the surface is around 1000mb, and the 500mb pressure level is typically located around 20,000 feet.

The height of a pressure surface varies with the temperature of the air mass below it, so meteorologists look at the "height" maps to get a sense of how warm or cool an air mass is. In this map, which shows the departures from average of 500mb heights, you can clearly see the cool weather in the West, associated with lower than average 500 mb heights, and the large expanse of unusually warm air east of the Rockies and up into Canada, where that big reddish blob of above average heights is located. 

In recent years, some meteorologists have noted an increased occurrence of large height anomalies, which are often associated with extreme weather events, and may even be related in some ways to global warming.

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Comments

By Rebeca S. Long (30303)
on July 15th, 2012

Climate change due to increase of global warming.

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