Weather Quiz

Hurricane Joaquin's Track  (Source: NOAA)

Under ideal environmental conditions, Hurricane Joaquin developed into a powerful Category Four hurricane last week in the Atlantic Ocean.  Joaquin was the strongest hurricane to form in the Atlantic Ocean since.

A.  1998

B.  2005

C.  2010

D.  2012

---

Answer to Weather Quiz question from September 25.

True.  The last Category 5 hurricane to form in the Atlantic Ocean was Hurricane Felix in 2007.

Major October Hurricanes: Past and Present

Hurricane Opal making landfall in October 1995  (Source: NOAA)

Although September is the busiest month of the hurricane season, the season continues until the end of November.  Many damaging and deadly hurricanes have occurred across the Atlantic Ocean Basin in October.  On this date 20 years ago, the remnants of an infamous hurricane left its mark on the Mid-Atlantic Region.

2014:  Hurricane Gonzalo formed in mid-October and was the strongest hurricane of the 2014 season.  At peak intensity, Gonzalo had sustained winds of 145 mph with a minimum air pressure of 940 millibars, making it a solid Category Four hurricane.  It’s important to note that air pressure is a more accurate measure of the intensity of a hurricane than wind speed.  The lower the air pressure, the stronger the storm is.  Standard sea level pressure is approximately 1013 millibars, so 940 millibars is symbolic of a strong area of low pressure.  Although Gonzalo weakened to a Category Two storm before passing over Bermuda, it still caused roughly $400 million in damage.

2002:  Hurricane Lili came ashore in Louisiana as a Category 1 on October 3.  Lili caused extensive damage totaling $860 million in 2002.  At its strongest, Lili was a Category Four hurricane – like Gonzalo – with maximum sustained winds of 145 mph and a minimum central air pressure of 938 millibars.  Lili was the first hurricane to make landfall in the United States since Floyd in 1999.

1998:  Mitch was upgraded to hurricane status on October 24 in the western Caribbean Sea.  Due to favorable environmental conditions, Mitch quickly intensified into one of the most intense hurricanes on record.  At peak intensity, Hurricane Mitch was a Category Five monster with sustained winds of 180 mph and a minimum air pressure of 905 millibars.  Although Mitch weakened before impacting Central America, it still caused devastating flooding in Nicaragua and Honduras.  NOAA’s estimated death toll for Hurricane Mitch was approximately 11,000.  Mitch was the first Category Five hurricane to form in the Atlantic Ocean since Andrew in 1992. 

1995:  This was one of the busiest hurricane seasons on record, with a total of 19 named tropical storms, 10 of which became hurricanes and of those, 5 became major hurricanes in the Atlantic Ocean.  The strongest hurricane of the season was Hurricane Opal.  At peak intensity, Opal was a very dangerous Category Four hurricane with sustained winds of 150 mph and a minimum air pressure of 916 millibars.  To some, that air pressure might seem unusually low for a Category Four hurricane.  The National Hurricane Center noted that Opal had the lowest air pressure of any Atlantic hurricane on record that did not become a Category Five.  

Fortunately, Opal weakened to a Category Three hurricane before making landfall near Pensacola, Florida on October 4.  In fact, on October 5, 1995, Opal’s remnants passed through the Mid-Atlantic Region where they caused three tornadoes in the DC Metro Region – one each in Anne Arundel, Prince George’s and Charles Counties in Maryland. 

Trading a Hurricane for a Nor'Easter?

Hurricane Joaquin poised to remain offshore (Source: NOAA)

Although Hurricane Joaquin has been the major weather story this week, it is poised to track far enough east that no direct impact will be felt across the East Coast.  That said, widespread coastal erosion is expected to continue through the weekend.  According to the National Hurricane Center, Joaquin is the most intense hurricane to form anywhere in the Atlantic Ocean since Hurricane Igor in 2010 and has had a significant impact on the Bahamas. Joaquin is also the strongest hurricane to effect the Bahamas since Frances in 2004.

Ironically, the early season Nor’Easter that’s been buffeting millions of people up and down the East Coast with heavy rain and gusty winds has siphoned off some of the moisture from the hurricane.  While some of Joaquin’s outer rain bands have impacted our coastline, the Nor’Easter has helped protect the United States from a landfall by Joaquin.  Nevertheless, flooding has occurred over a huge area as far south as Georgia and north to New England.  

As gloomy as the weather has been the last few days, conditions could have been much worse had Joaquin made landfall in the United States.  For example, Hurricane Isabel brought heavy rains, significant coastal flooding and caused 1.4 million power outages across the DC Metro Region in 2003.  Many people are also still recovering from Sandy nearly three years ago, so Joaquin remaining offshore is an especially good thing.

More rain has occurred in the Mid-Atlantic Region this week than in the previous two months combined.  From August 1 through September 28, only a scant 1.66” of rain fell in the Nation’s Capital, while 3.56” has occurred since Tuesday.  Just yesterday, the National Weather Service confirmed a weak EF-0 tornado touched down on Tuesday, September 29 in Laurel causing minor damage.  In addition to the heavy rain that’s occurred this week, temperatures have been much cooler than average.  Thursday’s high temperature in Washington, D.C. was 63 degrees, while yesterday and today have both had high temperatures of only 58 degrees compared to an average high of 73 degrees.

The dramatic change in the weather pattern this week from being warm and dry in August and much of September to being so cool and wet is not unprecedented.  October is a transitional month for much of the United States, as the throes of autumn envelop much of the country with cooler temperatures and occasional coastal storms.  In fact, this Nor’Easter could have brought the Mid-Atlantic significant snowfall had it developed in the winter.

What Can Washingtonians Expect in October?

Where will Hurricane Joaquin track next?  (Source: NOAA)

The last four months has featured highly variable weather in the Nation’s Capital. May and June were among the warmest on record, while June was also the second wettest in Washington, D.C. That rainy trend continued through the first half of July, but since then there has been significantly below average rainfall.  From August 1 through September 28, there was a rainfall deficit of more than four inches in the Nation’s Capital.

This week, the pendulum has swung the other way to a very rainy weather pattern for much of the eastern United States. Widespread rainfall totals of more than an inch across the Mid-Atlantic Region occurred September 29.  That kept September 2015 from being among the driest on record, but September finished with an average temperature (combing daily highs and lows) of 74.9 degrees that made it the 7^th warmest on record in Washington, D.C.

Longtime Washingtonians will remember how quickly the weather pattern can change from being very dry to wetter-than-average.  September 2005 was the driest on record in the Nation’s Capital with only 0.11” of rain (compared to an average of 3.72”).  It was followed by the wettest October on record with a monthly total of 9.41”.

According to the National Weather Service, the average high temperature on October 1 in Washington, D.C. is 74 degrees, but that falls to 64 degrees by Halloween. October averages 3.4” of rain in the Nation’s Capital and has seen a trace of snow as recently as October 29, 2011!  Although uncommon, 90 degree heat has occurred in early October as recently as in 2013, when it was 91 degrees at National Airport on October 6^th.

October can also see prolific rainfall and flooding from the remnants of a tropical system. The remnants of Hurricane Opal brought the Mid-Atlantic Region appreciable rainfall and some weak tornadoes in early October 1995.  The rainy weather pattern we’re currently in will continue into the weekend.  The track of Hurricane Joaquin looms large over the forecast for the DC Metro Region and much of the eastern United States. 

Joaquin is currently a Category 4 hurricane near the Bahamas and could impact the eastern United States over the weekend and early next week.  The prospect of a tropical storm or hurricane in this part of the country will remind longtime Washingtonians of past storms like Floyd in 1999, Isabel in 2003 and Irene in 2011.  However, there is still a great detail of uncertainty in the track, timing and intensity of the storm. My colleagues and I on the WUSA9 weather team will keep you posted.