Thursday, December 31, 2015

What's Behind the Unusual Weather this December?


Severe Weather Reports (12-23-15)  Source: NOAA



December will go down in the record books as one of the warmest on record across the eastern United States.  This month is also distinctive due to an unusual amount of severe weather.  Although December averages approximately two dozen tornadoes nationwide, December 2015 has had more than 80 tornadoes.  To learn why, check out this story I posted on the WUSA9 website.

Tuesday, December 29, 2015

How Warm Was Christmas?


Balmy Christmas Morning Temperatures, Bethesda, MD

Temperatures have been more than 11 degrees warmer than average in Washington, D.C. through December 28.  This month has had 14 days with high temperatures in the 60s or warmer – which is more characteristic of April than December – in addition to another 10 days with high temperatures in the 50s.  December’s highest average daily high temperature in the Nation’s Capital is 52 degrees on the first of the month.  However, by December 7 daily average highs fall to the 40s where they remain for the rest of the month.

Temperatures have been warmer than average on all but two days so far this month.  For example, it’s been in the 70s on three days this December officially at National Airport.  That’s the highest such total Washingtonians have enjoyed since there were four days in the 70s in December 2001.  Those longing for snow on Christmas Day were faced with a high temperature of 69 degrees – 25 degrees warmer than the average high in the Nation’s Capital.  Washington, D.C. was appreciably warmer than it was in Phoenix on Christmas where it was only 61 degrees.

Aside from skiers, not many people have been complaining as the lack of wintery precipitation made travel easier across the eastern United States.  Washington, D.C. set two record highs this month while Baltimore had five record highs this month.  Conversely, significant winter weather has affected many areas of the western United States, as New Mexico, Texas and the mountains of California have had prolific amounts of snow. 

However, such unusual weather is bound to correct itself.  NOAA’s temperature outlook for early-2016 is calling for an equal chance of above or below average temperatures in the Mid-Atlantic Region.  The seven-day forecast my colleagues and I on the WUSA9 weather team are preparing includes more average temperatures in the mid 40s starting on January 1, 2016
 
New Record Highs (Degrees Fahrenheit)

December 24:

Washington, D.C. (National Airport): 71
Dulles Airport, Sterling, Virginia: 71
Baltimore, Maryland (BWI Airport): 71




December 27:

Baltimore, Maryland (BWI Airport): 69

Friday, December 25, 2015

Weather Quiz


Fresh Snow in Bethesda, MD


When was the last time measureable snow occurred on Christmas in Washington, D.C.?


A.  2009

B.  2002

C.  1993

D.  1989




Answer to Weather Quiz question from December 8:

C.  2005.  Epsilon became a Category 1 hurricane on December 2.

Wednesday, December 23, 2015

Record Christmas Warmth


NOAA's Severe Weather Outlook for December 23


It would be an understatement to say that NOAA’s December outlook for above average temperatures across the eastern United States has come to fruition.  Multiple record highs have been set this month coupled with a lack of snowfall across the eastern two-thirds of the United States.  Many typically snowy winter cities such as Buffalo and Rochester, NY only recently saw their first measureable snows of the winter – considerably later than average.

El Nino has recently helped bring the western United States some much needed rainfall and mountain snows.  Meanwhile, many eastern cities – including Washington, D.C., Baltimore and New York City – are in the midst of one of their warmest Decembers on record.  What’s helped bring such unusual warmth this month has been the irregular position of the jet stream.  The jet stream – a river of air in the atmosphere that helps steer guide storms and air masses – has been uncharacteristically far north over the eastern United States.  That’s allowed for the unseasonal warmth on and off since Halloween – while much of the western U.S. has been cooler and wetter than average.  

Today, there is an area of low pressure in the central United States that’s going to use this significant temperature gradient – between colder than average in the western United States and upper Midwest to warmer than average in the eastern U.S. – to produce a large swath of severe weather from the Gulf Coast to the Ohio Valley.  Severe weather is rare in December, but not unprecedented.

Although residents of the Mid-Atlantic Region are in their fourth consecutive warmer than average December – this month is poised to be the warmest one yet.  Through December 22, Washington, D.C. has been more than 8 degrees warmer than average.  While warmer than average December weather will disappoint those wishing for a snowy Christmas, there could be a shift in the weather pattern to feature more winter-like or at least more seasonal temperatures.  Such was the case the last two winters when December was warmer than average in the Washington, D.C. – Baltimore corridor, but January, February and March were all colder than average.  

Washingtonians will be hard-pressed to see temperatures below freezing the rest of the year.  Not only have the last six weeks featured above average temperatures during the day, but nighttime temperatures have also been unusually balmy.  Although it was 32 degrees once in November in the Nation’s Capital, the first below freezing temperature didn’t occur downtown until December 19.  NOAA’s January outlook calls for at least a 33% chance of above average temperatures to continue in the Mid-Atlantic Region.


Record Highs in Jeopardy (Degrees Fahrenheit)


December 24:

Washington, D.C. (National Airport): 69 (1933)
Dulles Airport, Sterling, Virginia: 66 (1982)
Baltimore, Maryland (BWI Airport):  65 (1990)



December 25:

Washington, D.C. (National Airport):  72 (1964)
Dulles Airport, Sterling, Virginia:  71 (1982)
Baltimore, Maryland (BWI Airport):  72 (1964)



December 27:

Washington, D.C. (National Airport): 72 (1971)
Dulles Airport, Sterling, Virginia: 73 (1971)
Baltimore, MD (BWI Airport): 65 (1949)