How Does November Compare?

Today marks the end of November as well as the end of meteorological fall (the three month period that began September 1).  This fall has seen the continuation of the very warm and dry weather that dominated much of July and August in the Mid-Atlantic Region.  That has caused the rainfall deficit to balloon during the fall months.

Despite hot and dry months in July and August, Washington, D.C.’s annual rainfall deficit on September 1 was only 1.47”.  However, since September 1, the rainfall deficit at National Airport has ballooned to 6.40” as of November 29.  The latest Drought Monitor Index shows moderate drought conditions across much of the region.  Through November 28, only 0.26” of rain fell the entire month at National Airport.  According to the Capital Climate blog, that tied for the driest November 1 – 28 on record in Washington, D.C.  In fact, the Nation’s Capital was poised to break the 1981 record (0.29”) for driest November until yesterday. 

Some much needed rainfall occurred yesterday, with more in the forecast throughout the day today that will prevent Washingtonians from breaking the 1981 record.  Nevertheless, DC’s combined rainfall through November 29 of 3.78” for the fall season (September 1 – November 30) has positioned 2016 to be the driest fall since 2001.  As dry as it’s been this fall in the Mid-Atlantic Region, the conditions could have been worse for agricultural interests had they occurred during the spring or summer months.

Temperatures this month have been warmer than average with a monthly average temperature of 52.3 degrees at National Airport (combining daily high and low temperatures) through November 29.  November’s average temperature in Washington, D.C. is 49.6 degrees and is based on National Weather Service data from 1980-2010.  The warmest temperature in Washington, D.C. this month was 83 degrees on November 3, which set a new daily record high.  The coldest temperature to occur in the city this month was 32 degrees on November 23, while the more rural Dulles Airport’s coldest November temperature was 20 degrees (also on November 23).

NOAA’s outlook for December calls for a near average temperatures and precipitation in the Mid-Atlantic Region.  Unlike a year ago when a major El Nino contributed to a warm and wet December, an episode of La Nina has developed.  While La Nina also impacts global weather patterns, the current La Nina isn’t very strong.  My colleagues and I on the WUSA9 weather team will continue to keep you posted on the latest weather forecasts. 

Driest Observed Novembers in Washington, D.C. (measured at National Airport)

1.  0.29” (1981)
2.  0.37” (1965)
3.  0.53” (1917)
4.  0.55” (2001, 1922)
6.  0.60” (2012, 1908)
8.  0.76” (1936)
9.  0.79” (1890)
10.  0.80” (1903)

Weather Quiz

Prior to Hurricane Otto last week, when was the last time a tropical storm or hurricane tracked from the Atlantic across Central America to the Pacific Ocean?

A.  1950

B.  1985

C.  1996

D.  2005

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Answer to Weather Quiz question from November 17.

B.  St. Patrick’s Day.  The snowiest Thanksgiving on record in Washington, D.C. was in 1989 (1.6”).  By comparison, the snowiest St. Patrick’s Day in the Nation’s Capital came recently in 2014 when 3.9” of snow fell.  For more details, check out my Thanksgiving column.

Atlantic Hurricane Season

Hurricane Otto at peak intensity on 11/24/16 (Source: NASA)

The 2016 Atlantic hurricane season ends this Wednesday and has been one of the most significant in years.  There was a total of 15 tropical storms and seven of these intensified into hurricanes.  Three of these hurricanes became “major” hurricanes, Category 3 or greater on the Saffir-Simpson Scale.  NOAA’s forecast for the season was accurate as it called for 12 to 17 tropical storms, 5 to 8 hurricanes and 2 – 4 major hurricanes.

A contributing factor NOAA scientists pointed too in their seasonal forecast for 2016 was the dissipation of last winter’s major El Nino combined with the expected arrival of a weak episode of La Nina.  Consequently, this season saw the highest number of named storms in the Atlantic Ocean since 2012 and the most major hurricanes since 2011.  Conditions in the tropical east Pacific (off the west coast of Mexico) were a little quieter this season as no Category 5 hurricanes developed for the first time since 2013.

Hurricane Matthew was the strongest hurricane to develop this season in the Atlantic Ocean.  Matthew was the first Category 5 hurricane since 2007 and caused considerable damage in the Caribbean.  It also brought record flooding to the southeast U.S. coast from Florida to North Carolina.  Matthew developed a few weeks after Hermine became the first hurricane to make landfall in Florida since 2005.  A key streak remains intact, though, as no major hurricane has made landfall in Florida since Wilma in October 2005.  Although Matthew was at one point a Category 5 hurricane, it weakened to Category 1 status before making landfall in South Carolina on October 8.

Some other interesting storms occurred in 2016.  For instance, Alex reached hurricane intensity on January 14 over the east central Atlantic.  Alex was the first Atlantic hurricane in January since Alice in 1955.  On November 24, Hurricane Otto reached its peak intensity as a strong Category 2 with sustained winds of 110 mph while in the southwest Caribbean Sea.  Dr. Phil Klotzbach, Colorado State University said Hurricane Otto was “…the strongest Atlantic hurricane this late in the season since 1934.”  Hurricane Otto also was only the fifth tropical cyclone since 1950 to cross Central America from the Atlantic to the Pacific Ocean and first since Tropical Storm Cesar in 1996.

Hurricane season in the northeastern Pacific Ocean also ends this week and there aren’t any new tropical storms on the horizon.  The World Meteorological Organization meets every year after hurricane season ends to determine if any hurricane names should be retired.  A tropical storm or hurricane name is retired if the storm is particularly damaging or deadly (such as “Andrew,” “Katrina” and “Wilma”).  Names that are retired are replaced on the cyclical list of hurricane names with a different name that starts with the same letter.

A Warm or a White Thanksgiving?

Source: National Park Service

Longtime Washingtonians know that the weather in November has many similarities to March’s weather.  Both months experience high variations in temperature and types of precipitation.  November is the first of five consecutive months that Washington, D.C. averages measurable snowfall (0.5”), while March is the fifth (1.5”).

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.  High temperatures today are going to be near the seasonal average of 55 degrees in the Nation’s Capital, while last Thanksgiving was a tad warmer with a high temperature of 64 degrees.

There have been some large swings in the Thanksgiving weather for the DC Metro Region over just the last 20 years.  The warmest Thanksgiving on record in the Nation’s Capital occurred on November 22, 2007, with a record high temperature of 77 degrees at both National and Dulles Airports.  Meanwhile, the coldest Thanksgiving DC residents endured in recent times occurred on November 28, 1996, when the high/low temperatures were 35/26 degrees.  More recently, on November 23, 2000, Thanksgiving was also quite cold with temperatures of only 38/27 degrees at National Airport.  You have to go back a little further in history to find the snowiest Thanksgiving on record in the Nation’s Capital.  That occurred on November 23, 1989, when 1.6” of snow fell at National Airport.

There have been similar fluctuations in temperature and precipitation types on St. Patrick’s Day.  Although the record high for March 17 in Washington, D.C. is 88 degrees (1945), there have been two significantly warmer than average St. Patrick’s Days in the last 20 years.  In 1999, the high temperature in the Nation’s Capital reached 76 degrees and it was 75 degrees in 2012.  By comparison, D.C.’s snowiest St. Patrick’s Day on record occurred in 2014 when 3.9” of snow fell at National Airport.  That snowstorm spanned two days (March 16-17, 2014) and brought 7.2”, making it the tenth largest March snowstorm on record in Washington, D.C.  The average high and low temperatures in the Nation’s Capital on St. Patrick’s Day are 56/38 degrees.

Fortunately, no extreme temperatures are expected the rest of the month in the Mid-Atlantic Region.  Also, no appreciable precipitation is expected over the coming days.  While people with outdoor activities planned will be pleased, the moderate drought conditions that now exist across most of the DC Metro Region will only continue.