Monday, September 10, 2012

About Severe Weather This Year

Severe weather this year has been rather noteworthy at times -- June's derecho, remnants of Isaac bringing a couple of tornadoes last week, to name two events. However, in terms of total numbers of events, it hasn't been significantly different from last year.

Pennsylvania, year-to-date, has seen fewer tornadoes (26 last year, 15 in 2010) than either of the last two years per preliminary data and has seen about the same number of total severe weather reports (650) as it did in 2011 (668).  While we still have over three months to go in the year, the severe weather potential in our region is starting to diminish.  We'll still have a few potential events between now and winter and the final tally of total severe reports will end up a notch higher than last year.  However, the number of tornado reports statewide (11) will probably end up below the total of past two years.  In fact, in our region there have been only two confirmed tornado touchdowns -- one in Mount Ephraim and the other in Camden, Delaware.  There was a funnel cloud sighting off of Toms River this past Saturday but reports (initially) showed that did not touch down.

Delaware's severe weather event tally (33 for the year) is similar to the tally of the past two years (32 last year, 30 in 2010).  Like last year, one tornado touched down in the state (last year's was from Irene and was in Lewes).  Delaware, due to its size, has one of the lower tallies on severe weather in the country but its tally here is not the lowest in the Lower 48.  Rhode Island (23 this year) outdoes it on a per-state basis but in terms of geography, the West is a lot less "severe" in terms of weather compared to east of the Rocky Mountains.  The combination of topography being less favorable for severe weather development, atmospheric patterns historically (a lack of Gulf of Mexico moisture), and more sparsely populated areas help limit the reports...although the latter is not a much inhibitor in the data...there simply is not as much severe weather from a wind or hail standpoint from the Rockies on west.

New Jersey's severe tally for this year (168) is just behind the total from last year (172).  Like last year, the Garden State has had one tornado touchdown (Middlesex County last year).  The state has averaged one tornado event per year for the last four years (going back to 2009).  The brunt of this year's severe weather came from the Derecho event on June 29th, with 53 reports across South Jersey as the storm swiped through South Jersey.  The majority of those 53 reports were wind, which is the common theme with severe weather reports around this part of the world if you didn't notice.  Hail only accounted for 20% of the 851 total reports between the three states, with the highest percentage in Pennsylvania (139/650, 21%).  Our 20% average for hail reports is below the national average for this year of 32% of severe reports coming from hail.

All of the data in this post comes from the Storm Prediction Center, which has a great database of severe weather reports that go back several years.  The database includes preliminary information so it's a bit more of an apples-to-apples comparison of years (which is how our comparison is year-to-year).  The numbers this year suggest that it's been a relatively active year but not one that's terribly skewed out of proportion to past years.  With the Fall severe season providing a secondary spike historically, we may end up with these numbers bumping a bit higher before year's end.