Where has Hurricane Season Already Begun?

Hurricane Marie, Eastern Pacific Ocean (August 2014), Source: NOAA

Although hurricane season doesn’t begin in the Atlantic Ocean until June 1, it is already underway in the Eastern Pacific Ocean.  The area of the Pacific Ocean known as the “Tropical Eastern Pacific” is located north of the Equator, west of Mexico and east of Hawaii.  Hurricane season there starts two weeks earlier on May 15 and ends on the same date as in the Atlantic on November 30.

The National Hurricane Center in Miami monitors both the Atlantic Ocean Basin and the Eastern Pacific Ocean for tropical development.  That’s because systems that develop in both areas can affect the United States.  The Gulf Stream is a warm ocean current that allows tropical systems to maintain their intensity as they trek along the East Coast.  A good example of that is Hurricane Fran in 1996 that made landfall in North Carolina as a Category 3 hurricane.

On the West Coast of the United States the California Current has the opposite track of the Gulf Stream.  It keeps cooler water from the northern Pacific running along the California coast, which often precludes any tropical systems from making it that far north.  Tropical storms and hurricanes that form off the West Coast of Mexico can affect the United States in other ways such as creating rough surf when an intense storm develops.

The Eastern Pacific Ocean averages 15 named tropical storms, 8 of which become hurricanes and 3 of those become “major” hurricanes.  That’s compared to average in the Atlantic which are 11 named storms, 6 hurricanes and 2 “major” hurricanes.  A “major” hurricane is defined as at least a Category 3 on the Saffir-Simpson Hurricane Intensity Scale with sustained winds of at least 111 mph.  Although no named storms have developed yet this year in the Eastern Pacific Ocean, the Atlantic Ocean has already seen its first named storm of 2015.  Tropical Storm Ana made landfall in South Carolina on May 10 and brought heavy rain and winds.  The first named storm in the Eastern Pacific will be Andres.

While 2014 was a quieter than average season in the Atlantic Ocean, the Eastern Pacific Ocean had a much busier than average season.  The Eastern Pacific had 22 named storms, including 16 hurricanes of which 9 became “major” hurricanes last year.  In fact, the 16 hurricanes tied the Eastern Pacific record for most to develop in a season.  The most damaging Eastern Pacific hurricane last year was Odile, which made landfall in Cabo San Lucas, Mexico.

Mexico’s national weather organization, the Servicio Meteorológico Nacional, is calling for a busier than average 2015 season with 19 named storms, 11 hurricanes and 4 “major” hurricanes.  On the other end, tropical meteorologists at Colorado State University are calling for a below average hurricane season in the Atlantic Ocean with only 7 named tropical storms, 3 hurricanes and 1 “major” hurricane.

A Preview of Summer

Beautiful Spring Weather in Germantown, MD  (May 2015)

If you think this month has been warmer than average in the Mid-Atlantic, then you would be correct.  In fact, temperatures have been warmer than average on 13 of the first 16 days of the month in the Nation’s Capital.  That includes the first 90 degree day of 2015 in Washington, D.C., that came on May 12.  Through May 12, the month was an astounding 9 degrees warmer than average.

What’s helped make this May so warm was the stretch of 10 consecutive days with highs in the 80s.  That’s very unusual in May in the Nation’s Capital because the average high temperature doesn’t reach 80 degrees in Washington, D.C. until May 31.  Although no daily record highs have been set this month, the monthly average temperature (combining the daily high and low temperatures) at National Airport through yesterday was 71.2 degrees.  That would make this May the 5^th warmest on record.  The warmest May on record in the Nation’s Capital came in 1991 (when the average May temperature was 73 degrees).

Although today’s average high temperature is 76 degrees downtown, today’s actual high was 87 degrees at National Airport.  That’s the average high on June 24 in the Nation’s Capital.  Temperatures will return to more seasonal levels on Wednesday in the mid to upper 70s.  That will help keep this month’s average temperature among the warmest May’s on record.  According to NOAA’s Climate Prediction Center, the national temperature outlook for the next one to two weeks calls for continued warmer than average temperatures in the Mid-Atlantic Region. 

Until yesterday’s thunderstorms brought appreciable rainfall to the Mid-Atlantic Region, the DC Metro Region had been in the midst of an exceptionally dry month.  In fact, the Drought Monitor Index indicates that “abnormally dry” conditions exist across much of Eastern Pennsylvania and North Central Maryland.  Although May averages 3.99” of rain, National Airport has observed only 0.82” of rain so far this month (with the bulk of that occurring yesterday). 
  

Scattered thunderstorms are possible through Tuesday when a cold front will pass through the Mid-Atlantic Region ushering in more seasonal temperatures and less humid air for the second half of the work week.  Although scattered thunderstorms can bring heavy rain where they occur, no widespread rainfall is expected. 

According to the National Weather Service, May has to finish with an average temperature of at least 70.5 degrees to be the 5^th warmest on record in the Nation’s Capital.  My colleagues and I on the WUSA9 Weather Team will keep you apprised on the latest weather forecasts.