Extreme Weather in October 2013?
October has certainly been a notorious month for producing intense storms in the past few years. In 2011, a massive Nor’easter on October 29 – 30th dumped significant snow on Pennsylvania and northern New Jersey with upwards of 1 foot in the higher elevations. Areas in interior New England even topped two feet from the storm, with over 3 million people without power in the Northeast. Then, on October 28 – 29, 2012, Sandy devastated the New Jersey Coastline, delivering hurricane force gusts all the way into Pennsylvania and dumping feet of snow in West Virginia. So the big question is, “What will October 2013 bring?”
Although the Northeast will start out on a tranquil note, the weather pattern certainly looks to change toward the end of October. In particular, a ridge is expected to build over the western US states (+PNA) along with a large dome of high pressure over Greenland (-NAO/AO). The set-up will likely squeeze cold air out of the arctic into the troughiness over the eastern US. This "blocking" pattern is shown in the graphic below and will probably persist through mid-November:
The amplified pattern above is also a more stormy one compared to normal and is more conducive for coastal storms on the Eastern Seaboard. Interestingly, snow cover in the arctic is running above normal and is expected to increase over the next few weeks. In addition, arctic sea ice extent is much greater than last year and not far below the 30 year average. These two factors indicate a large cold pool of air is present and will likely be able to drop into the eastern US from time to time.
Whether the cold can team up with a strong storm will be the key. When looking back on past years which evolved in the same manner (analog years), each contained a strong pre-season snowstorm signal, all between late October and mid-November. These analogous years certainly add confidence to the storm potential.
History has shown that significant snowfall is not out of the question in October. In fact, three out of the last five years have produced measurable snow in Eastern Pennsylvania and New Jersey, including points north. Whether this is a long term trend is yet to be seen, but as for 2013, the early winter storm trend is definitely more favored.