A hot half-year...
Posted August 7, 2012
It's no surprise to any of us that 2012 got off to a mild start with a winter that didn't seem all that winter-like in large part, and then some bursts of record-setting heat over central and eastern parts of the U.S. during the Spring, with March in particular shattering records and running far above normal, all thanks to frequent and persistent high pressure ridges aloft that formed over central portions of the nation and often extended eastward from there. Of course, large ridges centered over our part of the northern hemisphere would be expected to correspond, or teleconnect, to persistent troughiness and cooler than normal weather in some other locations, and that was the case, so that overall northern hemisphere temperatures were not that far off normal when averaged around the globe. Still, it made for quite the toasty start to the year both on a National basis and for the state of NC, as shown in the graphic above.
As seen there, we ended up with a 6-month average temperature for the contiguous U.S. that was 3.4 degrees above the long-term normal for 1981-2010, and this was the warmest average temperature for the nation in the 118 years for which data are available. For our state as a whole, the average temperature for Jan-Jun was 2.8 degrees above normal, again the warmest in the 118 year period or record, and finally, for the Raleigh-Durham airport, the average temperature for the first half of the year ran 3 degrees above normal, and as was the case for the larger areas, was the warmest observed so far, although for a shorter observation period of 68 years.
It will be interesting to see how the rest of the year plays out, and to what degree the warm pattern becomes moderated. The tendency for formation of hot high pressure ridges has backed off a little through July and early August, and while long-term projections from the Climate Prediction Center maintain a good chance of above normal temperatures for central (especially north-central) portions of the U.S., they do reduce the area covered by the higher chances, and for much of NC drop the chances of above and below normal temperatures to about equal by the middle of Fall, as shown in the second image, where the best chances for above normal temperature cover the northern plains and midwest.
The first month of the second half of the year is over with now - at the RDU airport, we ended up with an average temperature of 83.5 degrees, which was 3.5 degrees above normal. This was not a record, but only missed by a couple tenths of a degree, coming in second only to 2011, when the average July temperature was 83.7 degrees, and well ahead of the number three July on the list, which was 82.5 degrees in 1993. We're still a few days away from the new numbers and historical rankings being available and published for the state and nation.