Annual average temperatures for Washington, D.C., 1871 - 2012 compared to 1981 - 2010 baseline average.
This entry notes some weather related items, in particular this entry by Matt Rogers on the Capital Weather Gang site on Thursday:
"Done deal: Washington, D.C. to complete warmest year on record in 2012"
The link is here.
Summary from the article (with additional content added):
Also, my December and annual climate information for Washington, D.C. (KDCA) comes from this site run by Sterling (LWX).
Washington, D.C. (as measured at Reagan Washington National Airport climate station (KDCA)) will likely break "by a landslide" the warmest year on record. In particular, it is likely* to finish at or about 61.5 degrees Fahrenheit (F) for an annual average. This surpasses the previous warmest year by +1.3F (1991: 60.2F).
*There are still four days left in the year, so it may change slightly.
The current 30-year normal (1981 - 2010) annual average temp. for KDCA is 58.2F, so the 61.5F corresponds to +3.3F.
Think about what a 5F warming would entail -- D.C. would have a climate more akin to Atlanta, Georgia. I hates Atlanta, Georgia (but that's a separate issue).
Washington, D.C., records stretch back to 1871, the year when official weather records were first systematically kept by the Signal Service, the original precedessor to the National Weather Service.
The Washington, D.C., monthly anomalies in 2012 were stunning in how sustained they were above normal -- with 11 of the 12 months above normal
Washington, D.C., monthly temperature anomalies from the 30-year average for that month. Only November was below normal. March averaged +10.0F above normal at 56.8F.
Through December 27th, KDCA is averaging +6.3F above normal at 46.4F. Of note, the "normal" here is for the first 27 days of December, so it is not a full monthly record. The full monthly normal is 39.7F versus the first 27 days which is 40.1F (thus, the average drops another 0.4F in that time).
Of note, the warmest December on record is 45.6F in 1984 or +5.9F. (NOTE: This is a correction to what I stated in previous entries that it was 45.5F, which occurred in 1971, 1982, and 2001. I need to correct those.)
Here is the year-long plot of 2012 temperature anomalies versus the normal "sine wave" chart. Note how persistent temperatures were above normal for the year.
Some other excerpts:
* "2012's exceptional warmth stands out most when you consider the previous 9 warmest years are all clustered within 0.9F of one another, whereas 2012 is 1.3F above 1991, the second warmest year."
* "Of the top 10 warmest years on record, 40 percent have occurred since 2002, and 60 percent occurred betweem 1973 and 1998. [In addition,] 2010, 2011, and 2012 make up three of the top 6 warmest years."
Geopotential height anomalies - prevailing pattern in 2012 -- over North America showing the "negative PDO" pattern (see below).
The article goes on to link this warmth in part to a strongly negative Pacific Decadal Oscillation (PDO). But it also links this to both regional urbanization (heat island effect) and global climate change -- as well as moving the climate recording station to its current location (in, I believe, 1941) from the previous location at 24th and M Streets NW.
I'm not sure about that last point -- if anything, summers would be a tad cooler at KDCA.
As for the PDO, it is one of multiple oscillation patterns on different time and spatial scales -- e.g., NAO / AO, ENSO, and MJO -- whose frequencies and intensities will likely change as a result of overall global warming.
Anyway, December is not likely to end up the warmest on record because it is going to be chilly the next four days and that +6.5F anomaly is likely to erode by a significant amount.
To the GOP Teabaggers: A few colder-than-normal days does NOT therefore "prove" fantasies about global cooling" no matter what Fox News or AM rightwing hate radio tells you.
Light Snow for Saturday?
There is a chance of snow -- albeit light -- on Saturday. The current Sterling - LWX snow forecast map ACTUALLY has D.C. in the 1 to 2 inch range, rather than -- as Gary observed -- with the 1" contour just touching the western / northernmost part of the Capital Beltway. (Oh, yes, KDCA has had 0.2" so far this month as a result of what fell on Christmas Eve day.)
Sterling (LWX) snow forecast map issued 1239AM EST 28 December 2012 valid through 600PM 29 December 2012.
I would look more intently at the impending trivial weather system, but the stupid NCEP MAG site remains down with a poor substitute in place. NWS / NCEP Central Operations is aware of the problem and posted a useless bureaucrat-ese message about how they "will continue to provide enhancements to this site as quickly as possible."
Record Warm 2012 for United States
Also, the U.S. is still on track for its warmest year on record -- surpassing 1998. You may read a great deal about that here.
Here are two key charts that are adaptions by ClimateCentral.org of data from NOAA (NWS) as maintained by NCDC and other sources.
Contiguous U.S. temperatures from 1895 - 2012 with the last 21 days of December estimated based on the 117 year average.
2012 monthly year-to-date anomalies for the contiguous U.S. using NOAA data and compiled by ClimateCentral.org. December shows the different possible outcomes assuming different temperature regimes from coldest to warmest Decembers.
OK, that's all for now. As you can see, it is crazy late again as I post this -- and I need to be ready for work by 930AM if only because (as I noted in my previous entry) the water is going out tomorrow all day. At least I don't have to be home -- I was able to reschedule the cable technician visit to Jan. 5th (and it was a good thing because the first person at RCN did not follow the right procedure in setting it up).
I intend to post at least two entries over the weekend including my Christmas day pics of Glen Burnie, and prior to that my Friday night musical entry.