November 2013: Colder than normal and slightly dry

December 2, 2013

November 2013 didn’t feel like November with several wintry blasts after a briefly mild beginning.  The month averaged 3 degrees F below normal (exactly the same as last year, tying with 2008 too for coldest of the 2000s), and we achieved several cold weather milestones.

November 2013 saw three days with high temperatures below 40F (11/24, 11/25, 11/3o), which was the most since 1956.  The two-day period one week ago (Sunday, the 24th -Monday, the 25th) was the coldest since 1970.  The high temperature of 34 that Sunday (Nov. 24) was the coldest high in November since 1987.

Related: Abnormal cold to close November: possibly coldest in decades

Here is how all three major reporting stations shook out for the past month with regard to temperature and precipitation:

allthree

Dulles was the coldest compared to normal, but National picked up the most rain.  It is interesting that all three airports were within .13″ of each other, which is more common in the winter months when large-scale  weather patterns prevail instead of localized features such as thunderstorms. Normal rain at the three airports is 3-3.5″.

Here is more on both temperature and precipitation for the month that was November 2013:

Temperatures in detail

While the average temperature for November 2013 and 2012 were the same, this year’s version saw colder days by mid-to-late month than last year.  We had five days with lows in the 20s, while last year had none.  Here is the day-by-day year-on-year comparison for reference:


Both years saw days that were warmer than normal, but 2013 had a few more overall even though its colder days were colder.  The standard deviation on temperatures was about five degrees last year, but was closer to eight degrees this year.  You can definitely see that on the chart above with 2013 looking much more like a heart monitor than 2012!  In terms of rankings for the 2000s, you can see the range of coldest to warmest Novembers here:


The triple play of coldest Novembers are on the left including the last two years, while the warmest November was twelve years ago back in 2001 with the average monthly temperature being just a bit over eight degrees warmer than this year’s outcome, an impressive range.

For official temperature records, we had a couple cold ones.  Baltimore’s high of 32F on Sunday November 24th tied with 1880 for the coldest high on that date.  Dulles also had a high of only 32F that day, which beat the 1971 record of 36F.

Precipitation

November was on track to be a much drier-than-normal month, but then a heavy rain system last week brought the local water tables back into balance.  In fact, Dulles set a daily record rainfall of 1.72″ on Tuesday, Nov. 26th, beating 1996′s 1.02″.

The chart below shows how November 2013 fared against the other years of the 2000s (it was the 57th wettest all-time):


All-in-all, 2013 was really in the middle of the pack compared to other Novembers of this new century, but it was quite a bit wetter than last year’s result.  You can track the daily rainfall events compared to last year below and can see that if we hadn’t had that bigger storm last week, we’d probably have performed as one of the driest Novembers of the 2000s instead.


November’s middle-of-the-road result has kept the year-to-date precipitation anomaly running in surplus (+2.02″).

Related: What is Washington, D.C.’s weather like in November?

The weather pattern

November had a  fascinating weather pattern.  Conditions over the North Pole and over the North Atlantic were the type that usually favor warmer weather over eastern North America.  Factors such as a positive Arctic Oscillation (+AO) and a North Atlantic Oscillation (+NAO) would have led most forecasters to expect a warmer-than-normal November.  But pulsing upper level ridging in the North Pacific into the Alaska area kept forcing Polar air masses south into the U.S. to drive the colder regime.  This situation is known as a negative Eastern Pacific Oscillation (-EPO), and it literally stole the show this past month as shown below.

novemberupperlevel

December 2013

The -EPO pattern described above is expected to still drive colder air masses into the Lower 48 over the next two weeks, but these cold air masses may struggle a bit more to reach the East Coast than they did in November due to the development of some Southeastern U.S. warm upper level ridging.  The current thinking is that the first half of December should be quite variable (there are concerns about mixed precipitation next week) with a slight colder-than-normal result ultimately, but warmer pattern changes are possible in the second half of the month as Alaskan upper level ridging may retreat to the Bering Sea or even Northeast Asia, which would considerably diminish its influence on our area.  So we may be able to define December as a colder-leaning start and a warmer-leaning finish, but confidence is still quite low on the second half of the month yet.

The National Weather Service only has the D.C. area in the EC category meaning equal chances for above, below, or normal temperatures and precipitation just like they did last month.  This is unfortunately not very helpful for our area.  You can see their depiction here.

For further information

The National Weather Service publishes nice monthly assessments usually within a week of the close of each month (should be available shortly):

You can click on your closest airport location here:

Reagan National (DCA)

Dulles Airport (IAD)

Baltimore-Washington (BWI)

Capital Weather Gang’s Ian Livingston contributed to this post.

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Jason Samenow · December 2, 2013