DC Says Good-Bye to a Wild November 2020

 

Today’s heavy rain across the DC Metro Area and severe weather potential (primarily east of town) remind me of some of November’s more recent severe weather outbreaks.  Less common than earlier in the year, severe weather still occurs in November as the transition from fall to winter continues.  Severe weather is defined as a thunderstorm that contains one or more of the following: hail 1” in diameter or greater, wind gusts of 58/+ mph, or a tornado.

November 15, 2020: 

The DC Metro Area had a rare severe weather outbreak that was concentrated in the northern suburbs.  A severe thunderstorm watch was issued in the late afternoon for much of the DC Metro Area.  The primary threat during this outbreak was severe, damaging wind gusts with a series of storm reports.  Fortunately, no injuries or widespread power outages were reported in the DC Area.

November 17, 2013:

One of the more significant November severe weather outbreaks in recent memory occurred seven years ago.  This outbreak covered a large area from the Tennessee Valley to the Great Lakes Region to the Mid-Atlantic.  Over 100 confirmed tornadoes occurred from Tennessee to Michigan, with a deadly EF3 tornado in Kentucky that claimed three lives. 

November 16, 2010:

This event was concentrated on the East Coast from South Carolina to New York.  The dominant type of severe weather was severe wind gusts.  There was, however, a confirmed EF-1 tornado in Baltimore, Maryland.  Three injuries were reported from the tornado, which had wind speeds between 86-110 mph. 

Tornado intensity is ranked on the Fujita Scale that was originally created in the 1970s.  However, it was updated and became the "Enhanced Fujita Scale" or “EF Scale” in 2007.  The National Weather Service changed the criteria for severe hail in January 2010.  Prior to this, hail 0.75"/+ (penny-sized) in diameter was considered severe.  However, in order to reduce confusion and the number of severe thunderstorm warnings, the criteria for severe hail was raised to 1”/+ (quarter-sized). 

November 14-16, 2006:

There were over 200 reported cases of severe weather, including 40 tornadoes between November 14 and November 16.  The impact ranged from Louisiana to upstate New York.  Although 168 of the 217 severe weather reports were for wind, one of the tornadoes was especially deadly.  On November 15, the town of Riegelwood, North Carolina suffered eight fatalities during a tornado that destroyed several homes.

 

DC’s Warm and Wet November

 

November 2020 will finish as DC’s first warmer and wetter than average November since 2009.  Through November 28, there have been 21 warmer than average days so far this month with near average temperatures today and above average temperatures tomorrow.  This month’s average monthly temperature, combining daily high and low temperatures, is more than 4° above average. 

The month of November is the third and final month of meteorological fall that began on September 1.  It’s also the first of five consecutive months that DC averages measurable snowfall.  Accumulating November snowfall has become a rarity in the DC Metro Area, with only one such occurrence over the last two decades.  Also, below average November rainfall has become more common in recent years.  This month will be only the second wetter than average November in the Nation’s Capital over the last decade.

There has been 3.75” of rain since November 1 – more than half an inch above DC’s November average of 3.17”.  A developing area of low pressure will bring roughly an inch of rain tomorrow.  This month could finish as one of DC’s 10 wettest on record.  Most of DC’s monthly rainfall total of 3.75” occurred in just the two-day period of November 11-12 (2.91”).  That helps illustrate that while this has already been a wetter than average November, there have also been long stretches of dry weather.

This month has also been quite warm, with seven days of highs in the 70s – tied for DC’s sixth highest total of 70° November days on record.  DC’s record for most 70° November days is 12, which occurred in 1975.  Having such mild weather this month couldn’t be more dissimilar than last November, which finished as DC’s coldest since 1996.  November 2019 was also DC’s first since 2010 without any 70° temperatures.

With above average temperatures today and tomorrow, there’s a good chance November 2020 will finish as either DC’s third or fourth warmest on record.  Despite a colder than average start to December this week, NOAA’s Climate Prediction Center expects the warmer average weather that’s dominated DC’s November weather headlines to continue.  However, as longtime Washingtonians know, the right ingredients only need to come together once to create a major winter storm in an otherwise mild winter. 

DC’s Warmest Novembers (Source: National Weather Service)

1.  54.8° (2001)
2.  54.4° (1979, 1975)
4.  54.3° (1985)
5.  54.0° (1931)
6.  53.7° (2015)
7.  53.3° (1994)
8.  53.1° (2003, 1999)
10.  52.6° (2016)
11.  52.4° (2011)
12.  52.2° (2009, 1978)
14.  52.0° (1990)
15.  51.8° (1982, 1977, 1946)

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DC’s Wettest November’s  (Source: National Weather Service)

1.  7.57”  (2018)
2.  7.18”  (1877)
3.  6.70”  (1963)
4.  6.43”  (1932)
5.  6.33”  (1952)
6.  6.05”  (1972)
7.  6.03”  (1889)
8.  6.00”  (1948)
9.  5.77”  (1970)
10.  5.33”  (1988)

Thanksgiving Weather in the Nation’s Capital

 

Longtime Washingtonians know that the weather in November has many similarities to March.  Both months experience high variations in temperature and types of precipitation with occasional severe weather.  November is also the first of five consecutive months that Washington, D.C. averages measurable snowfall.

Some may wonder why Thanksgiving falls on a different date every year.  Federal law proclaimed it a national holiday to be celebrated on the fourth Thursday of November and it will fall on November 26 this year.  DC’s average high/low temperatures on November 26 are 54°/38°.  However, unlike recent Thanksgiving’s in the Nation’s Capital that have been chilly and dry, this Thanksgiving will be warm and wet with rain during the first half the day and highs in the 60s. 

The last time high temperatures on Thanksgiving remained below 40° in Washington, D.C. was 20 years ago on November 23, 2000 when the high temperature was only 38°.  By comparison, DC’s warmest Thanksgiving on record occurred 13 years ago on November 22, 2007, with a high temperature of 77°.

Although Washington, D.C. averages 0.5” of snow during November, accumulating snow has become a rarity during the month, with only one such occurrence in the last two decades.  However, looking at DC’s overall weather records, snow occurred six times on Thanksgiving 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 exceptionally cold and snowy months and remain the last time Washington, D.C. had both a white Thanksgiving and Christmas.

November 2018 was a very cold and wet month in the Nation’s Capital, with 1.4” of snow on November 15.  That snow was gone by Thanksgiving Day, and it turned out to be DC’s wettest November on record.  While this November will finish as a wetter than average month, it hasn’t been wet enough to rank among DC’s 10 wettest.  November 2020 has been unusually warm though, and the warm weather on Thanksgiving will only serve to accentuate that. 

Washington, D.C.’s Five Coldest Thanksgiving’s by High 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 a Close

 

Hurricane Iota, November 2020 (Source: NOAA)

The 2020 Atlantic hurricane season has been an epic one with a record number of named storms.  A total of 30 named tropical storms developed, of which 14 became hurricanes, including seven major hurricanes.  The 30 named storms surpassed the previous record of 28 from 2005.  However, there were 15 hurricanes in 2005 with seven major (Category 3 or higher) ones.

This season began early (before June 1) for a sixth consecutive year, with two named storms in May.  That’s unlike 2005 which didn’t see the first tropical storm until the second week of June.  The 2005 season didn’t end until the first week of January, when the final named storm (Tropical Storm Zeta) weakened on January 6.  The tropical Atlantic, including the Gulf of Mexico and Caribbean Sea, is fairly quiet now, so it remains to be seen whether or not the 2020 season will continue past its official end on November 30 as it did in 2005. 

Even if no more named storms develop, 2020 would have the distinction of seeing the highest number of tropical storms and hurricanes (12) make landfall in the United States.  This high number of landfalls was largely a function of where the bulk of this season’s tropical storms and hurricanes developed.  Many of them developed in the Gulf of Mexico/Caribbean Sea or off the southeast Coast of the United States – not far from the U.S. coastline.  By comparison, only eight named storms (five hurricanes and three tropical storms) directly impacted the United States in 2005.

While 2005 and 2020 will both finish with a nearly identical number of major hurricanes, the Atlantic had four Category 5 hurricanes in 2005, compared to only one this season.  That helped 2005 finish with the highest amount of Accumulated Cyclone Energy or “ACE” (a metric used to measure the energy used by a tropical cyclone during its lifetime) of any season since the satellite era began in 1966.  This season is currently in sixth place with 180 units of ACE.

Another key difference between this season and 2005 is how the majority of the named storms for the first half of the season were relatively weak.  The first major hurricane of 2020, Hurricane Laura, didn’t develop until late August.  By comparison, the 2005 season had two major hurricanes in July, including Hurricane Emily that became the earliest Atlantic Category 5 hurricane on July 16.  Only two of the first 25 named storms this season became major hurricanes (Laura, Teddy).  However, four of the last seven named storms have become major hurricanes. 

When Hurricane Iota reached Category 5 intensity on November 16, it became the latest in the season a Category 5 has developed in the Atlantic Ocean.  Iota was also the first Category 5 hurricane with a name from the Greek Alphabet and, along with Hurricane Eta, made 2020 the first November on record that the Atlantic had two major hurricanes.  Not only was Hurricane Iota the strongest hurricane of the season, but was the second strongest November hurricane in the Atlantic, overall, behind only the 1932 hurricane that made landfall in Cuba.  Its peak intensity was with 175 mph and a minimum central air pressure of 915 millibars (mb) compared to 160 mph / 917 mb for Iota.

It remains to be seen whether or not Hurricane Iota will be the final named storm of the 2020 Atlantic hurricane season.  But, this season will not finish as one of the costliest on record for the United States.  That’s despite the high number of landfalling systems, primarily because the majority of the storms that made landfall were not that strong unlike 2005 and other, more recent, seasons like 2017. 

Weather Quiz

 

True or False.

Even if there’s no more rain before the end of the month, November 2020 will still finish as DC’s first warmer and wetter than average November since 2009.