DC’s Record Setting November

November 2018 will finish as DC’s first colder and wetter than average November since 2002.  This month also broke DC’s 1877 record (7.18”) for wettest November with 7.57”.  That put 2018 less than an inch away from the 1889 record (61.33”) for wettest calendar year with 60.45” of rain since January 1.

  

The Nation’s Capital averages 3.17” of rain in November, but has more than doubled that amount with 7.57” of rain this month.  That’s more rain than Washingtonians saw during the previous four (2014-2017) Novembers combined.  The Nation’s Capital averages 3.05” of rain in December so setting a new record for wettest calendar year is likely.  DC’s official weather reporting site is National Airport and that’s often important to remember since conditions can sometimes vary quite a bit between National Airport and other weather reporting sites, like Dulles Airport. 

Having a wetter than average November also raised the total of wetter than average months this year to eight.  Only January, March and October were drier than average.  DC Area residents also saw measurable November snow this month for the first time since 1996.  The 1.4” of snow on November 15 is almost triple DC’s November snowfall average of 0.5”.  According to NOAA, Washingtonians have seen more snow this November than in any November since 1989.

November’s warmest day in the Nation’s Capital was November 1 (76°), while this month’s coldest temperature was 28° on November 23.  In fact, the high/low temperature of 35°/28° on November 23 produced a daily average temperature of 31.5° and made for DC’s coldest November day since November 19, 2014.  With a monthly average temperature (combining daily high/low temperatures) of 46.7° through November 29, this month will finish approximately 3° colder than average (49.6°). 

Some may wonder if there is a correlation between a colder and wetter than average November and the upcoming winter season.  Looking at DC’s 10 wettest November’s prior to 2018, seven were also colder than average.  However, only two of the seven subsequent winters were snowier than average (1877-1878 and 1932-1933).  The facts do not support a correlation.  NOAA currently expects near average temperatures and precipitation in December.

How Does the 2018 Atlantic Season Compare ?

2018 Atlantic Hurricane Season (Source: NOAA)

The final day of the 2018 Atlantic hurricane season is on Friday, November 30.  Hurricane season in the Atlantic Ocean Basin runs from June 1 through November 30 and includes the Atlantic Ocean, Gulf of Mexico and Caribbean Sea.  This season will finish with 15 tropical storms, seven of which became hurricanes including two “major” hurricanes.  That’s slightly above the seasonal average of 12 tropical storms, six hurricanes and three major hurricanes. 

A system becomes a tropical storm and is given a name when sustained winds around the center of the storm reach 39 mph.  Once sustained winds reach 74 mph it is upgraded to hurricane status.   A “major” hurricane has sustained winds of 111/+ mph and is classified as a Category 3 or higher on the Saffir-Simpson Scale.

The first named Atlantic storm of 2018, Alberto, made landfall in the Florida panhandle on May 28.  Although it was initially a subtropical storm, Alberto became a tropical storm by the time it made landfall.  Alberto was also one of six storms this season that spent time as a subtropical storm.  

The strongest hurricane of the season was Michael in early October.  It was a high-level Category 4 hurricane at peak intensity, with sustained winds of 155 mph (a Category 5 hurricane has sustained winds of 157/+ mph) and a minimum central air pressure of 919 millibars.  Hurricane Michael was the first Category 4 hurricane on record to make landfall in the Florida panhandle.  It also had the third lowest air pressure of any landfalling hurricane in the United States – behind only the unnamed 1935 Florida Keys Labor Day hurricane and Hurricane Camille in 1969. 

Hurricane Florence was the other major hurricane of the 2018 season.  It weakened below major hurricane status before it made landfall but caused devastating flooding across parts of the Mid-Atlantic and southeastern United States.  For the first time since 2014, the month of November will not have a named storm in the Atlantic Ocean Basin.

The 2016, 2017 and 2018 Atlantic hurricane seasons were remarkably similar in terms of total number of named storms.  The three-year period finished with an average of nearly 16 tropical storms, eight hurricanes and four major hurricanes.  Hurricane Matthew in 2016 as well as Irma and Maria reached Category 5 intensity last year. 

Saturday’s Rainfall Produces More Records

The combination of Saturday afternoon’s heavy rain and below average temperatures made for a miserable weather day for the DC Metro Area.  It also resulted in a slew of weather records and inched 2018 closer toward setting a new record for wettest year overall.  The 1.42” of rain yesterday at National Airport was the 22^nd day of 2018 that at least an inch of rain fell.  That broke the previous record of 21 such days from 1878.

A total of 7.11” of rain has occurred in Washington, D.C. so far this month putting November 2018 only 0.07” behind the 1877 record for DC’s wettest November (7.18”).  By comparison, the Nation’s Capital averages only 3.17” of rain in November, so we’ve more than doubled that total with the potential to break the monthly record tomorrow.  Our eight previous Novembers (2010 – 2017) all happened to be drier than average.

Meanwhile, Dulles Airport has had 7.45” of rain so far this month and that’s good for second wettest November behind only 1963 (7.83”).  Overall, Dulles Airport has had 60.75” of rain since January 1, making 2018 its second wettest year on record behind only 2003 (65.69”).  BWI Airport has had 7.72” of rain so far this month and that’s already made this month Baltimore’s wettest November on record, according to the National Weather Service.  BWI Airport – Baltimore’s official weather reporting site – also set a new record for highest annual rainfall total.  Since January 1, BWI has had 64.86” of rain, eclipsing the previous record of 62.66” of rain from 2003.

With the rest of November and the entire month of December remaining, there’s a strong likelihood that Washington, D.C. and Dulles Airports will join BWI Airport with 2018 becoming their wettest years on record.  DC is only 1.33” of rain away from reaching that benchmark.  NOAA recently issued its monthly outlook for December and it calls for near average precipitation in the Mid-Atlantic Region.  Since Washingtonians average 3.05” of rain in December, that would be more than enough to make 2018 DC’s wettest year on record.

It’s remarkable that Washington, D.C. is even having this conversation for wettest year on record considering the dry 31-month period from August 2015 through March 2018.  During that time, all but seven months were drier than average and that produced a total rainfall deficit of 16.42”.  By comparison, the six-month period from April 1 through October 31 produced a rainfall surplus of 20.63” – more than eliminating the accrued rainfall deficit from the previous 31 months.

Washington, D.C.’s Five Wettest Novembers (Source: NOAA)

1.  7.18”  (1877)
2.  6.70”  (1963)
3.  6.43”  (1932)
4.  6.33”  (1952)
5.  6.05”  (1972)

Average: 3.17”

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Washington, D.C.’s Five Wettest Years (Source: NOAA)

1.  61.33” (1889)

2.  60.83” (2003)

3.  60.09” (1878)

4.  58.17” (1886)

5.  57.54” (1948)

Average: 39.74”

Thanksgiving in Washington, D.C.

November 2018, Cabin John Park, Maryland

This Thanksgiving will be one of DC’s coldest in recent memory.  Although today’s high temperature of 42° occurred just after midnight, temperatures this afternoon will remain in the 30s across much of the DC Metro Area.  That would be colder than average for the height of winter in January, much less late November.  Today’s average high temperature in Washington, D.C. is 55° but temperatures will be significantly colder than that.  These frigid temperatures are easily the coldest so far this fall season. 

The last time high temperatures on Thanksgiving remained below 40° in Washington, D.C. was 18 years ago on November 23, 2000 when the high temperature was only 38°.  By comparison, DC’s warmest Thanksgiving on record occurred 11 years ago on November 22, 2007 with a high temperature of 77°.

Last week’s snow is long gone.  However, accumulating snow has occurred six times on Thanksgiving in Washington, D.C., with the most recent in 1989.  A total of 1.9” of snow was measured at National Airport on November 23, 1989.  November and December 1989 were both exceptionally cold and snowy months in the Nation’s Capital and remains the last time Washington, D.C. had both a white Thanksgiving and Christmas.

This month’s average temperature (combining daily high and low temperatures) in DC is 1.8° below average through November 21.  November has also been significantly wetter than average with 5.69” of rain so far.  So far this month two days have had more than an inch of rain at National Airport (DC’s official weather reporting site), which is rare so late in the year.  Saturday is poised to be another very wet day in the DC Metro Area. 

If the Nation’s Capital has another day with at least an inch of rain before December 31, then it would be the 22^nd such day of 2018.  It would set a new record for most days in a calendar year with an inch or more of rain.  November 2018 is already DC’s ninth wettest on record with 5.69” of rain and that also makes it DC’s wettest since 1972.  The good news is the weather will be sunny and dry, albeit very cold, for Thanksgiving today and shopping tomorrow.

Washington, D.C.’s Five Coldest Thanksgiving’s by Low Temperature (Source: NOAA)

1.  30°: November 27, 1930
2.  33°: November 28, 1901
     33°: November 26, 1903
3.  35°: November 23, 1989
     35°: November 28, 1996

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Washington, D.C.’s Five Warmest Thanksgiving’s by High Temperature (Source: NOAA)

1.  77°: November 22, 2007
2.  75°: November 22, 1979
     75°: November 20, 1941
     75°: November 30, 1933
3.  73°: November 24, 1927

Hurricane Season Nearing an End

Hurricane Michael, October 2018  (Source: NOAA)

The 2018 Atlantic hurricane season has been a memorable one for being both costly and deadly.  An “average” Atlantic hurricane season features 12 tropical storms, of which six become hurricanes, including three major ones.   Hurricane season began on June 1 and NOAA’s forecast was for a near to slightly busier than average season.  A total of 15 tropical storms, featuring eight hurricanes and two major hurricanes, have formed in the Atlantic Ocean Basin in 2018.  The Atlantic Ocean Basin includes the Atlantic Ocean, Caribbean Sea and Gulf of Mexico.  

The first named storm of the season, “Alberto” developed on May 25 and was initially classified as a “subtropical” storm.  It had characteristics of both a tropical storm that feeds off warm tropical ocean water and a subtropical area of low pressure that also gains energy from a strong temperature gradient.  Eventually, Alberto became a purely tropical storm and made landfall on the U.S. Gulf Coast.  Alberto was the first of six named Atlantic storms this season that spent time as subtropical storms. 

The first major Atlantic hurricane of 2018, Florence, developed near the Cape Verde Islands off the West Coast of Africa.  At peak intensity, it had sustained winds of 140 mph and a minimum central air pressure of 939 millibars.  Fortunately, Hurricane Florence weakened below major hurricane status before making landfall near the North and South Carolina border.  However, Florence was a slow-moving storm that dumped a copious amount of rainfall over much of North and South Carolina, as well as southern Virginia.  The remnants of Florence also brought heavy rainfall to the DC Metro Area on September 17.  

Hurricane Michael developed in early October and was the strongest Atlantic hurricane of 2018.  It was a borderline Category 4/Category 5 storm at peak intensity, with sustained winds of 155 mph and a minimum central air pressure of 919 millibars.  Michael was the first Category 4 hurricane on record to make landfall in the Florida panhandle and caused catastrophic damage in the southeastern United States.  It was still a Category 3 hurricane when it crossed into the state of Georgia, making it the first major hurricane anywhere in the state since 1898.  The names “Florence” and “Michael” are all but certain to be retired by the World Meteorological Organization for being destructive and deadly storms.

There haven’t been any tropical storms or hurricanes in the Atlantic Ocean Basin since Hurricane Oscar lost its tropical characteristic over the colder waters of the North Atlantic Ocean on Halloween.  November is usually a quiet month in the tropics as environmental conditions are generally unfavorable for tropical storm formation.  On the rare occasion a tropical storm or hurricane develops in November, it is usually found in the western Caribbean Sea or Gulf of Mexico.  Hurricane season ends on November 30.

Setting Records in the Nation’s Capital

November 15 Snow in Poolesville, Maryland  (Courtesy: Ashley Adams)

Thursday’s snowfall in the DC Metro Area was its first measurable November snowfall since 1996.  A total of 1.4” fell at National Airport, breaking the November 15 record of 0.2” from 1906.  Meanwhile, 3” of snow was reported at Dulles Airport that shattered its previous November 15 record of a trace of snow that occurred most recently in 1995.  The American Meteorological Society (AMS) defines a trace of precipitation as “…an unmeasurable (less than 0.01 in.) quantity…”

A common misconception among Washingtonians is that November snowfall is a rarity.  The fact is that the Nation’s Capital averages 0.5” of snow in November.  Washington, D.C. has had snow in 15 of the past 30 Novembers from 1987 – 2017.  However, only a trace of snow occurred in 11 of those 15 winters.  That helps illustrate that while snow isn’t uncommon in DC during the month of November, measurable snowfall is rarer.  According to the National Weather Service, yesterday’s snow was DC’s largest November snow since 1989 when 3.5” occurred.  Longtime Washingtonians may recall that DC’s snowiest November occurred in 1987 (11.5”).

Yesterday’s precipitation was significant for another reason as well.  The total of 1.15” of rain (and liquid snow equivalent) that occurred in DC pushed the total to 58.53” since January 1.  That made 2018 DC’s fourth wettest year on record, with six more weeks to go.  Also, a total of 5.67” of rain has fallen at National Airport (DC’s official weather reporting site) since November 1.  That ranks among DC’s 10 wettest Novembers on record.

Select November 15 Snow Totals (Source: National Weather Service)

DC

National Zoo – 2”

Maryland

Clarksburg – 5.2”
Frederick – 5.0”
Rockville – 2.7”
BWI Airport – 1.7”


Virginia

Leesburg – 5.0”
Dulles International Airport – 3.0”
Wolf Trap – 2.7”
National Airport – 1.7”

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Washington, D.C.’s Ten Wettest Novembers (Source: NOAA)

1.  7.18”  (1877)
2.  6.70”  (1963)
3.  6.43”  (1932)
4.  6.33”  (1952)
5.  6.05”  (1972)
6.  6.03”  (1889)
7.  6.00”  (1948)
8.  5.77”  (1970)
9.  5.33”  (1988)
10.  5.29”  (1926)

Average: 3.17”

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Washington, D.C.’s Five Wettest Years (Source: NOAA)

1.  61.33” (1889)

2.  60.83” (2003)

3.  60.09” (1878)

4.  58.17” (1886)

5.  57.54” (1948)

Average: 39.74”

Can Fall Weather lead to Snowy Winters ?

Given the slew of winter weather outlooks recently issued for the Nation’s Capital, it’s a good time to analyze whether fall weather is a reliable indicator of what the upcoming winter will be like.  September and the first half of October were significantly warmer than average in Washington, D.C., while the second half of October was appreciably cooler than average.  While September was much wetter than average, October was the first drier than average month in the Nation’s Capital since March.

On the other hand, November 2018 has already exceeded its monthly average amount of rainfall in Washington, D.C.  While November’s average temperature (combining daily high/low temperatures) has been within 0.1° of average through November 13, NOAA expects cooler than average temperatures over the second half of the month.  That would make November 2018 a cooler and wetter than average month in Washington, D.C.

The 10 snowiest winters on record in the Nation’s Capital span three centuries, ranging from 1891-1892 to 2009-2010.  Five of the 10 autumns prior to DC’s 10 snowiest winters were wetter than average, so that does not point to a trend.  However, the preceding autumns do share some commonalities.  Eight of the 10 autumns prior to DC’s 10 snowiest winters were cooler than average.  Washington, D.C. also had snow in eight of those 10 Novembers.  

The Nation’s Capital averages 0.5” of snow in November, but having a colder than average November with snow doesn’t necessarily mean anything about the upcoming winter.  For example, more than 80% of DC’s near average seasonal snowfall total (15.3”) for the 1989-1990 winter occurred prior to December 31 and that includes the 3” of snow that occurred in November 1989.  Meanwhile, the rest of the 1989-1990 season had below average snowfall.  Conversely, the 0.5” of snow that fell in November 1995 foreshadowed the 1995-1996 winter that became DC’s third snowiest on record.

Since DC’s snowiest November on record in 1987, Washingtonians have had a trace or more of snow in 15 of the last 30 Novembers.  However, 23 of the last 30 winters have had below average snowfall.  Three of DC’s snowiest winters (1957-1958, 2002-2003 and 2009-2010) occurred during a moderate to strong episode of El Nino.  Two of the three preceding autumns prior to those winters were wetter and cooler than average in the Nation’s Capital.  

NOAA expects a moderate episode of El Nino to develop this winter.  El Nino winters have a more active southern branch of the jet stream and that often translates to wetter than average weather in the southern United States.  On occasion, a coastal storm can develop and head up the east coast.  If there is sufficient cold air in place, then the DC Metro Area could see significant snowfall.  The January 2016 blizzard, which tied for DC’s fourth largest snowstorm on record, also occurred during an El Nino winter.

As a whole, the fall 2018 season is poised to finish warmer and wetter than average in Washington, D.C.  With the arrival of the anticipated El Nino, it will be interesting to see what happens during the upcoming winter.  My colleagues and I on the WUSA9 Weather Team recently issued our 2018-2019 winter weather outlook.

Washington, D.C.’s Ten Snowiest Winters (Source: National Weather Service)

1.  56.1” (2009-2010)
2.  54.4” (1898-1899)
3.  46” (1995-1996)
4.  42.5” (1921-1922)
5.  41.7” (1891-1892)
6.  41” (1904-1905)
7.  40.4” (2002-2003), (1957-1958)
9.  40.3” (1960-1961)
10.  37.7” (1978-1979)