Weather Quiz

Satellite View of the Tropical East Pacific  (Source: NHC)

True or False.

Today is the first day of the Hurricane Season in the Eastern Pacific Ocean.

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Answer to the Weather Quiz question from April 30.

True.  April was the first warmer than average month of 2015 in Washington, D.C.  According to the National Weather Service, it was 2.6 degrees warmer than average.

Has May Been Warmer than Average?

Spring is a Beautiful time of year !

Many Washingtonians have been thrilled with the summer like warmth so far this month.  It has been at least 80 degrees in the Nation’s Capital every day since May 3.  In fact, today could be this year’s first day of 90 degree heat at National Airport.  The last time it was at least 90 degrees in Washington, D.C. was on September 11, 2014, when it was 91 degrees.  However, today’s record high of 93 degrees downtown should be safe, although, the record high of 89 degrees could be approached at Dulles Airport.

Yesterday’s high was 83, which is typical for June 11.  During the month of May, the warmest average high temperature in the Nation’s Capital is 80 degrees on May 31.  So to start the month with a string of ten days in the 80s is fairly remarkable.  High temperatures tomorrow will be much more seasonal in the mid-70s.  Although ten days with temperatures of at least 80 degrees is unusual in May in this part of the country, it isn’t unprecedented.

Three years ago, May was significantly warmer than average and included a nine day stretch with high temperatures of at least 80 degrees that began May 22.  May 2012 finished more than 5 degrees warmer than average and was a harbinger of what followed in June and July.  June 2012 saw the hottest June temperature on record in the Nation’s Capital (104 degrees on the June 29).  July 2012 set a new record for most days of triple digit heat (7) in a month including four consecutive 100 degree days in Washington, D.C.  May 2011 saw a similar ten day stretch of weather with highs of least 80 degrees before July 2011 became the hottest July on record at National Airport.

May has also been cooler and wetter than average in the not too distant past.  May 2005 featured only three days with high temperatures in the 80s and four days where high temperatures remained in the 50s (typical of March).  According to the National Weather Service, May 2003 had 23 days of rain that helped suppress temperatures.  It remains the coolest May in Washington, D.C. since 1967.  By comparison, this month is currently more than eight degrees warmer than average.  Although all but one day this month has featured warmer than average temperatures, this month’s streak of days in the 80s isn’t officially a heat wave.  A “heat wave” is defined as a minimum of three consecutive days of 90 degrees or greater.  The last “heat wave” to occur in the Nation’s Capital during the month of May came in 2013 (May 29-31).

There is no official correlation between a warmer than average May and what the weather will be like during the summer in the Nation’s Capital.  The summer-like pattern that’s been in place so far this month could remain in place giving Washingtonians a warmer than average summer as was the case in 2011 and 2012.  The weather pattern could also shift dramatically and become cooler and wetter than average as May 2003 and May 2005 were.  My colleagues and I on the WUSA 9 weather team will keep readers apprised of the latest forecasts for the rest of the spring and summer.

How Rare are Named Storms in May?

Tropical Storm Alberto (May 20, 2012)

Although hurricane season doesn’t begin in the Atlantic Ocean until June 1, named storms sometimes form before the season starts.  It happened again this week when the National Hurricane Center named “Ana” off the southeast coast of the United States.  Tropical storms and hurricanes are rare in June so named systems in May are rarer still.  The last time a tropical storm was named before the season began was in 2012.

Ana was initially a “subtropical” storm, meaning it has characteristics of both a tropical storm and an extratropical or non-tropical storm.  A tropical storm has the potential to grow into a hurricane if the sustained winds around the center increase to at least 74 mph, while a subtropical storm does not.  If a subtropical storm becomes a hurricane, that means it’s changed enough to become a fully tropical system.  A tropical storm or hurricane is a warm core system that derives its energy from warm ocean water as opposed to other sources such as temperature gradients the way non-tropical or mid-latitude storms do.  The National Hurricane Center has since determined that Ana has transitioned from a "subtropical" to a tropical storm.

Early or late in the hurricane season, it’s common for a cold front to become stationary over the Gulf of Mexico or off the southeast coast of the United States.  Both are favored areas for tropical development close to June 1 since the water warms more quickly there.  If the front lingers long enough then an area of low pressure sometimes forms.  Such was the case with Tropical Storm Ana this week.  Ana is not expected to become an intense system but will continue to bring gusty winds and rainfall to the southeast United States from Georgia to the Carolinas and southern Virginia.  The second named storm of 2015 will be "Bill."

On May 19, 2012, Tropical Storm Alberto formed in very similar location to Ana off the South Carolina coast.  It never became an intense system but did produce rough surf and gusty winds along the coast.  2012 was a unique season since a second named storm formed before the season began when Tropical Storm Beryl was named on May 26.  Beryl dissipated on May 30 and another four named storms – including the season’s first hurricane (Chris) – developed during the month of June. It’s quite rare for six named storms to form before the end of June.  Consequently, 2012 was the last busier than average hurricane season in the Atlantic Ocean with 19 named storms – almost double the seasonal average of 10 named storms.

The first April storm on record formed in 2003, when “Subtropical” Storm Ana was (ironically) named April 20 in the Central Atlantic Ocean.  My colleagues and I on the WUSA 9 Weather Team will continue to track the current version of Ana.

Summer Warmth Ahead of Schedule

May features ideal weather for all!  (Bethesda, MD)

Temperatures have finally turned the corner in the Nation’s Capital.  May has gotten off to a warmer than average start, following April which was the first warmer than average month of 2015 in Washington, D.C.  Today is poised to be the third consecutive day with high temperatures in the 80s across the DC Metro Region.  The high temperature reached 84 degrees yesterday for the third time this year.  However, today’s temperatures may be even warmer downtown making May 5 the warmest day yet of 2015.

The last time it was 85 degrees at National Airport (the official weather reporting site for Washington, D.C.) was more than seven months ago on September 27.  The average high for May 5 in the Nation’s Capital is 73 degrees so a high temperature of 85 would be significantly warmer than average.  However, 85 degrees is the average high for June 16 in the Nation’s Capital.  High temperatures are poised to climb to the mid to upper 80s in parts of the Mid-Atlantic Region today.

Although temperatures in the 80s aren’t expected on a daily basis until next month in the Nation’s Capital, a few days in the 80s are fairly typical in May.  That’s because May continues the transition from spring to summer and the weather pattern this week is very summer-like.  A large area of high pressure is sitting off the Southeast Coast of the United States pumping warm and increasingly humid air into the Mid-Atlantic Region.  Most Washingtonians would say today feels more humid out than it has the last few days as both dewpoints and relative humidity values are higher.  A cold front is approaching the DC Metro Region from the Great Lakes Region meaning the prospect of afternoon showers and thunderstorms has also increased today.

May typically sees bouts of showers and thunderstorms such as on May 8-9, 2008.  That’s when a severe weather outbreak impacted the Mid-Atlantic Region with confirmed tornadoes in Stafford County in northern Virginia as well as in Prince Georges County in Central Maryland.  Record rainfall was also observed downtown on May 9, 2008.  Fortunately, no injuries were reported.  But with today’s warmer temperatures and increased relative humidity, the atmosphere is more conducive to showers and thunderstorms as the cold front approaches.

Following the second consecutive colder and snowier than average winter in the Nation’s Capital, Washingtonians are relishing the June like temperatures that have enveloped the Mid-Atlantic Region so far this month.  Temperatures are expected to remain warmer than average for the rest of the week.  You can rely on my colleagues and I on the WUSA9 weather team for the latest forecast approaching the upcoming Mother’s Day Weekend. 

What Kind of Weather Should Washingtonians Plan for in May?

Glover Park, Washington, D.C.  (May 2015)

May typically features a wide variety of weather in the Mid-Atlantic Region.  The Nation’s Capital, in particular, has seen extremes from record heat to severe weather to even light snow during the month of May.  By and large, though, May features stellar weather ideal for the plethora of outdoor activities that are available for residents and tourists alike.  To read more about what kind of weather you can expect in May, check out this recent article I wrote for the WUSA9 website.