Looking Ahead to Hurricane Season

Tropical Storm Ana at peak intensity (April 21, 2003)

More people start to wonder what kind of hurricane season is on tap as we get deeper into spring.  Hurricane season starts June 1 in the Atlantic Ocean and runs through November 30.  An average season features 10 named tropical storms, of which 6 becomes hurricanes and 3 of those grow into “major” hurricanes.  A major hurricane is at least a Category 3 on the Saffir-Simpson hurricane intensity scale with sustained winds of at least 111 mph.

Dating back to 1995, the Atlantic Ocean has seen a series of above average hurricane seasons every year except three.  Although two of those three seasons came in 2013 and 2014, that doesn’t indicate an end to the cycle of busier than average hurricane seasons.  In fact, the distinguished tropical meteorologists at Colorado State University say “we remain in an active era for Atlantic basin tropical cyclones since 1995 (despite the quiet seasons that occurred in 2013-2014).”  They also noted that some of the contributing factors that made the last two years quieter than average in the tropics have lessened.  The Atlantic Ocean Basin includes the Gulf of Mexico and Caribbean Sea.

It’s important to note, though, that a below average hurricane season does not mean it won’t be a damaging season.  For example, 1992 had only seven named tropical storms with just one major hurricane.  However, that major hurricane was Andrew which was the first Category 5 hurricane to make landfall in the United States since 1969 – and only the third on record.  It was the costliest natural disaster in U.S. History until Hurricane Katrina thirteen years later.

Since 1995, the Mid-Atlantic Region has seen a few significant storms including the remnants of Hurricane Fran in 1996, Floyd in 1999 and Isabel in 2003.  Floyd brought the Mid-Atlantic Region beneficial rainfall after what was a hot and dry summer that saw water restrictions in parts of the region.  Isabel was also the first of eight Category 5 hurricanes that formed in the Atlantic Ocean between 2003 and 2007.  Fortunately, none of them made landfall as Category 5 hurricanes.
 
September is the busiest month of the hurricane season when the ocean is typically the warmest and the atmospheric conditions are the most conducive.  The first tropical storm on record to form in April came in 2003.  Ana made history on April 21, 2003, when it was named a tropical storm in the central Atlantic Ocean.  Ana’s sustained winds remained below the threshold of 74 mph that would have made it a hurricane.  I will write another column with the official forecast for the 2015 hurricane season from the National Hurricane Center closer to the start of hurricane season.

April's Roller Coaster in the Nation's Capital

Great Falls, MD

April continues the trend of highly variable weather in the Mid-Atlantic Region that’s so common during the spring.  There have been some memorable examples of both summer and winter like temperatures combined with severe weather in the Nation’s Capital during the month of April over the last twenty years.

In the span of just 24 hours, the weather spanned two seasons in Washington, D.C., on April 9 and 10, 1995.  The high temperature on April 9 reached 84 degrees (D.C.’s average high on June 13).  Just a day later, the high temperature was only 54 degrees (D.C.’s average high on March 10).  Fortunately, there wasn’t any violent weather associated with this dramatic temperature swing in the DC Metro Region.  On April 9, 1996, the high temperature was only 44 degrees downtown (characteristic of February 1) while 2.5” of snow fell at Dulles Airport.  High temperatures were in the low 80s in the Nation’s Capital just three days later.

A significant tornado outbreak occurred from April 6 through April 9, 1998.  A total of 62 tornadoes touched down during this four day period, including one of the strongest on record.  On April 8, an F5 tornado touched down in Birmingham, AL, and caused 32 fatalities.  A much weaker tornado, an F0, developed in Chesapeake, VA, on April 9, 1998.

  

On April 19, 2013, two relatively weak tornadoes occurred in the DC Metro Region.  An EF0 tornado formed in Largo, MD, while an EF1 tornado was observed in Fredericksburg. VA.  Fortunately, they caused only minor damage.  This severe weather followed record heat that occurred the previous week when a record high of 91 was observed on April 10 at National Airport.  Dramatic swings in temperature can help create an atmosphere that’s conducive for thunderstorms. 

Starting in 2007, the Fujita Tornado Intensity Scale was updated and became the “Enhanced Fujita Scale.”  That means tornadoes are no longer ranked as F0 to F5, but rather EF0 to EF5.  NOAA climate records show April has the third highest monthly average number of tornadoes in the United States.  Fortunately, today’s weather will be nothing short of stellar with ample sunshine and comfortable temperatures in the Nation’s Capital.  That’s lucky for residents and tourists alike who are eager to spend time outdoors at the Cherry Blossom Festival, the National Zoo or doing any number of outdoor activities.

How Severe is the Drought in California?

Santa Barbara, California

The state of California has recently instituted a new series of water restrictions in the face of an ongoing, and increasingly dire, drought.  Dating back several years, the ongoing weather pattern has kept the storm track from bringing California its average annual rainfall.  Locally, the Mid-Atlantic Region has experienced times of drought such as in 1999 and 2007 when water restrictions were issued to limit watering lawns, washing cars and filling swimming pools.

However, the drought in California has lasted much longer than any recent drought locally and is growing more severe with each passing month.  In addition to rainfall, California also relies on mountain snowpack to get a large volume of its water.  The snow typically adds up in the mountains during the winter months as the moisture-laden storms enter the state from the Pacific Ocean.  California then has the luxury of a fresh water supply for most of the spring and the summer as the reserve of mountain snow slowly melts filling up reservoirs.

A major problem, though, has been the lack of snowfall during the last few winters.  Below average mountain snowpack means there’s less water in reserve for the typically drier late spring and summer months.  That’s also the growing season for California's farmers, as well as when people use more water for activities such as gardening and watering their lawns. 

To offset the lack of rainfall, the agricultural industry has been using well water and ground water at an increasing rate.  Although that’s provided some short-term relief for farmers, the groundwater has become an endangered resource since it hasn’t been able to replenish itself naturally.  According to NASA scientist, Jay Famiglietti, “The withdrawals far outstrip the replenishment.  We can’t keep doing this.”  In some places the water table has dropped as much as 50 feet according to the U.S. Geological Survey. 

The combination of drought conditions – including the lack of mountain snowpack – and rapid depletion of ground water recently led California Gov. Jerry Brown, to instruct “the State Water Resources Control Board to impose a 25 percent reduction on the state’s 400 local water supply agencies.”  That’s where the majority of California residents get their water from so that should have a large impact on water conservation.

Parts of California, including San Francisco, had above average rainfall in December 2014 but that did little to offset the ongoing drought.  According to the National Weather Service, the rainfall deficits in San Francisco and Los Angeles are both over 30 inches during the last four years.  The U.S. Drought Monitor Index shows most of California is experiencing extreme to exceptional drought conditions.  It will take a combination of above average rainfall in tandem with water conservation over an extended period of time to replenish the state’s water supply.

Although the DC Metro Region doesn’t currently have drought conditions, residents of the Mid-Atlantic can learn the importance of water conservation and living sustainably by observing the response to the water crisis in California.

Weather Quiz

Source: NOAA

Which state averages the most tornadoes in a given year?

A.  Maryland

B.  West Virginia

C.  Pennsylvania

D.  Virginia

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Answer to Weather Quiz question from March 25.

True.  The Nation’s Capital saw 1.4” of snow on March 25, 2013 and 1.7” of snow on March 25, 2014.  Washington, D.C. averages 1.3” of snow during the entire month of March.

What Kind of Weather Can You Expect in April?

Nationals Park, Washington, D.C.

Springtime is an especially beautiful time of the year in the Nation’s Capital. Following the second colder than average winter and third consecutive snowier than average March, the arrival of April and more spring-like temperatures is wonderful news for many. April features a variety of outdoors activities designed to help residents and tourists alike take advantage of the milder weather and the many sites around Washington, D.C. Some of these activities include Opening Day at Nationals Park this Monday, the National Cherry Blossom Festival and an assortment of Earth Day related events throughout the month.

There is a high degree of variability in the weather in the Mid-Atlantic Region during the month of April. For example, Washington, D.C.’s average high on April 1 is 62 degrees, but that rises to 71 degrees by April 30. Measureable snow has occurred downtown as late as April 28 when 0.5” fell in 1898. Record heat also occurs periodically such as on April 17, 2002, when it reached 95 degrees in Washington, D.C.  On April 8, 2007, there was a record low of 29 degrees in the Nation’s Capital.

Such dramatic changes in temperature often coincide with thunderstorms as the seasons continue to change. In fact, the month of April averages the third highest number of tornadoes, nationally, behind only the months of May and June according to NOAA’s National Climatic Data Center.  On April 3-4, 1974 one of the largest severe weather outbreaks on record occurred. Known as the “Super Outbreak,” there were 148 confirmed tornadoes across thirteen states from the Gulf Coast north to the Great Lakes. Tragically, these tornadoes caused 330 fatalities and injured over 5,400.

April has had some significant severe weather outbreaks more recently. On April 2, 2006, there were 86 confirmed tornadoes that caused 9 fatalities from Iowa to Tennessee. An even larger tornado outbreak occurred on April 27, 2011, when there were 292 tornadoes that claimed 230 lives. Such a high death toll underscores why severe weather awareness is so important. Last April ended on a wet note in the Mid-Atlantic Region with 4.43” of rain at National Airport from April 25 through April 30.  Dulles Airport saw even more rain with 5.69” during the same time period.

This should help illustrate the full range of weather that’s possible in this part of the country during the spring months.  So to keep apprised of the latest weather forecasts during the month of April and beyond, be sure to check out the WUSA9 weather homepage.