How Will This October Be Remembered?

Autumn is a Beautiful Time of the Year

October is a transitional fall month that can be remembered for major events such as record warmth as in 2007 or Sandy in 2012.  More often than not, though, October is a fairly quiet weather month in the Mid-Atlantic Region.  This October has continued the 2016 trend of being drier than average.

The Nation’s Capital has an on-going rainfall deficit of 7.94” dating back to August 1, 2015.  Since January 1, the deficit is 4.96” since eight of the ten months of 2016 have featured below average rainfall.  There has been only 0.90” of rain at National Airport this month setting this October up to be the driest in Washington, D.C. since 2001 (0.69”).

There is a similar rainfall deficit at Dulles Airport which has a 7.68” rainfall deficit dating back to August 2015.  Only 0.6” of rain has occurred at Dulles Airport this month that would make this October their driest since 2000 (when only 0.06” of rain fell).  Temperatures this month have been significantly warmer than average in Washington, D.C. with an average monthly temperature (combining daily high and low temperatures) 3.4 degrees above average (through October 29).  The record warmth that occurred in the Mid-Atlantic Region when there were four consecutive days in the 80s (October 17 – 20) is a key contributor.  

The combination of warmer than average temperatures and below average rainfall the last several months have lead many fall weather enthusiasts to wonder what influence that will have on the fall foliage.  The above average temperatures in September and October have caused a slight delay of peak fall colors.  In the DC Metro Region, the leaves don’t typically reach their peak fall colors until late October and early November.  However, the dry weather typically causes leaves to fall more quickly than they otherwise would.  Whether or not any gusty winds occur can also influence how long the leaves remain on the trees.

It’s appropriate given how warm this month has been that record warmth is possible this afternoon as temperatures approach 80 degrees in the Nation’s Capital.  Today’s record high at National Airport is 82 degrees and 81 degrees at Dulles Airport (both from 1996) compared to the average high of 64 degrees for October 30.  However, temperatures will be more seasonal for Halloween tomorrow.  

According to the National Weather Service, the last time measureable rainfall occurred on Halloween in Washington, D.C. was in 2009.  The warmest Halloween Washingtonians have had in the last twenty years was in 2004 when it was 79 degrees while 2002 featured the coolest Halloween at 47 degrees.  Tomorrow’s temperatures in the Nation’s Capital will be more like last Halloween when it was 61 degrees.

Weather Quiz

Which day is normally warmer in Washington, D.C.?

A.  Halloween

B.  St. Patrick’s Day

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Answer to Weather Quiz question from October 10.

True.  2016 has featured the most active Atlantic hurricane season since 2012.

What Does NOAA’s Winter Outlook Look Like?

NOAA recently issued their seasonal forecast for the upcoming winter.  Unlike last winter’s El Nino, NOAA is expecting La Nina to influence this winter’s weather across the United States.  It is not, however, expected to be as significant as last winter’s El Nino event (the strongest El Nino since 1997-98).  La Nina is characterized by below average water temperatures in the east central Equatorial Pacific Ocean.  

La Nina conditions typically contribute to drier and warmer than average winters in the southern United States while parts of the northern United States experience wetter and cooler than average conditions.  Consequently, NOAA anticipates a greater than 50% chance of drier than average conditions this winter from Texas to Florida.  NOAA also says there is a greater than 40% chance of wetter than average conditions this winter in parts the northern Rockies and in the Great Lakes Region.

According to NOAA’s winter weather outlook, there is a greater than 50% chance of above average seasonal temperatures from Arizona to Texas.  That’s in addition to a greater than 40% chance for below average temperatures along parts of the U.S.-Canadian border this winter.  The Mid-Atlantic Region is in between these temperatures and precipitation projections with an “equal chance” for above and below average winter temperatures and precipitation.

It’s easy to see the variability from one winter to the next in the Nation’s Capital during just the last ten years.  During last winter’s El Nino event, Washingtonians experienced a warmer than average season with an average temperature of 42.0 degrees Fahrenheit (combining daily high and low temperatures) from December through February.  However, Washingtonians remember last winter not for the milder than average temperatures but for the 4th largest snowstorm on record when 17.8” of snow occurred in the Nation’s Capital on January 22-23.  That’s in contrast to the 1997-1998 El Nino winter when only 0.1” of snow fell in Washington, D.C.

The 2009-2010 winter was the snowiest on record in the Nation’s Capital when 56.1” of snow fell and that occurred during a moderate episode of El Nino.  By comparison, the warm (43.4 degrees average temperature) and relatively snow-free (2.0”) winter of 2011-2012 occurred during a moderate episode of La Nina.  An average winter in Washington, D.C. features an average temperature of 38.2 degrees and 15.4” of snow.  

Some important things to remember are that storm track is vital whether or not an episode of El Nino or La Nina exists.  In addition, there are many factors involved in issuing winter weather outlooks.  The phase of the “Oceanic Nino Index” which shows the presence of either El Nino or La Nina, along with the Arctic Oscillation and the Madden-Julian Oscillation are all important factors to consider.  

With so many factors involved in seasonal forecasts and an inherent amount of uncertainty in storm track, it’s vital to pay attention to the latest weather forecasts for your community.  That’s especially true in the DC Metro Region where a difference of a just a few miles can make a world of difference.  For example, while National Airport saw 17.8” of snow during January’s record storm, Dulles Airport saw 29.3”.  My colleagues and I on the WUSA9 weather team will continue to provide you with the latest weather updates.

What is “Indian Summer?”

Great Falls, MD (October 2016)

Washingtonians are in the midst of a major change in the weather pattern following their warmest October week in more than three years.  Today’s high temperatures of only 61 degrees made it the coolest day in Washington, D.C. since May 22 when it was 58 degrees.  61 degrees isn’t the average high in the Nation’s Capital until November 7.

Seven of the first nine months of 2016 have been warmer than average in Washington, D.C.  October has been no exception as temperatures have been 4.7 degrees above average through the 21^st.  That’s largely because of this week’s four consecutive days in the 80s at National Airport.  There haven’t been four or more consecutive October days at or above 80 degrees in Washington, D.C. since October 1 – 6, 2013.  Although no record highs occurred downtown, Dulles Airport saw four record highs and Baltimore had two records highs (officially observed at BWI Airport). 

This week’s warmest day was October 19 when it was 87 degrees at National Airport (Washington, D.C.’s average high on August 18).  That was the warmest October temperature in the Nation’s Capital since it was 91 degrees on October 6, 2013.  Some may wonder if this week’s warmth meets the official criteria for “Indian Summer.”  The National Weather Service defines Indian Summer as “An unseasonably warm period near the middle of autumn, usually following a substantial period of cool weather.”  Last weekend was cooler than average in the DC Metro Region with low temperatures in the 30s north and west of town.  So this week has featured some “Indian Summer” warmth in the DC Metro Region.

This year’s dry weather has continued with only 0.87” of rain over the first three weeks of the October (1.47” below average at National Airport).  By comparison, seven of the last ten Octobers in the Nation’s Capital have been wetter than average.  People may not mind the dry weather as much when they consider the Nor’easter that brought record rainfall and cold temperatures to the Nation’s Capital from October 15-18, 2009 and the severe weather that occurred on October 27, 2010.

People may wonder what typical Halloween weather is in the Nation’s Capital as October 31 draws closer.  Halloween’s average high and low temperatures at National Airport are 64 and 46 degrees respectively.  The last five Halloweens have featured near average temperatures with no measurable rainfall.  NOAA’s outlook for the next 1 to 2 weeks in the Mid-Atlantic Region is for a 33% to 40% chance of drier than average weather.  My colleagues and I on the WUSA9 Weather Team will keep you apprised of the latest weather forecasts.