Hurricane Trends

Category 1 Hurricane Irene nearing landfall in NC on 8/27/2011  (Source: NOAA)

From now until early October is climatologically the most active part of the Atlantic hurricane season, which runs through the end of November.  This season has already seen seven named tropical storms and three hurricanes, but no major ones.  The National Hurricane Center has been monitoring a tropical wave the last few days as it heads through the Bahamas, but it hasn’t developed into a tropical storm.

Scientists with NOAA and Colorado State University recently updated their seasonal forecast for the remainder of the 2016 Atlantic hurricane season with the expectation for an average to slightly busier than average season.  An “average” season sees approximately 10 tropical storms, six hurricanes and two major hurricanes, so there are still a few storms to go to meet that criteria.  That’s shouldn’t be a problem, though, as we enter what is typically the most active portion of the hurricane season.

The Atlantic Ocean has seen an uptick in tropical storm and hurricane development since 1995.  While the last few seasons have seen a near average number of tropical storms and hurricanes, there has been a significantly higher than average number of storms over the last two decades.  From 1995 through 2015, there was an average of approximately 15.4 tropical storms, 7.4 hurricanes and 3.5 “major” hurricanes (Category 3 or higher on the Saffir-Simpson hurricane scale with sustained winds at/above 111 mph).  During the same twenty-year span, there were nine Category 5 hurricanes – as strong as hurricanes get.

Several damaging and deadly hurricanes have impacted the United States since 2005 – including Ike in 2008, Irene in 2011 and Sandy in 2012 (which was officially declared a “post-tropical” system when it made landfall in the United States).  However, none of these were major hurricanes.  The fact that Ike, Irene and Sandy all rank among the costliest natural disasters in U.S. history illustrates that a hurricane doesn’t have to be “major” to have significant impacts.  A tropical system doesn’t even have to be a hurricane to be damaging.  For example, Tropical Storm Allison made landfall in Texas and caused record flooding across much of the U.S. Gulf Coast in 2001.  Allison was the first of only two tropical storms to have its name retired by the World Meteorological Organization for being especially damaging or deadly. 

Although a number of catastrophic storms have developed during the last 20 years, there has been a noticeable downturn in the number of significant tropical storms and hurricanes that have impacted the United States in recent years.  This can be partly attributed to simple luck that storms haven’t made landfall in the United States as frequently in the last decade as they did through 2005.  Scientists also point to global weather events such as an episode of El Nino or La Nina which can lead to an above or below average hurricane season.  The next tropical storm that develops in the Atlantic Ocean will be named “Hermine.”

Weather Quiz

Current Satellite Perspective of the Tropical Atlantic  (Source: NOAA)

What was the last hurricane to make landfall in the United States?

A.  Irene

B.  Wilma

C.  Ike

D.  Arthur

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Answer to Weather Quiz question from August 14.

Although August 2016 has featured the most triple digit heat in the Nation’s Capital (3 days) since 1930, Washingtonians have still had more triple digit heat in July than any other month by a wide margin.

The End of Summer?

A Great Place to Cool Off, Great Falls, Virginia

Although we’re in the midst of a glorious three-day stretch of September-like weather, the end of meteorological summer doesn’t officially arrive until August 31.  This summer has been unique and can be broken up into two different periods.  From June 1 through July 4, there was a noticeable absence of extreme heat with only five days at or above 90 degrees.  Since July 5, the Nation’s Capital has had 40 of the last 49 days at or above 90 degrees.  

This very hot stretch of weather not only produced Washington, D.C.’s sixth warmest July on record, but also yielded the first triple-digit heat since 2012.  Part of July’s hot finish was DC’s longest stretch of consecutive days at or above 95 degrees (seven) since the record streak of 12 in 2012. August has featured an even more impressive stretch of hot weather.  Not only have there been multiple days of triple-digit heat in August for the first time since 2002, but rarer still were three consecutive days of triple-digit heat (August 13 – 15).  Prior to this month, the last time there were three consecutive August days at/above 100 degrees in Washington, D.C. was in 1930.

Part of what made the summers of 2010 to 2012 so hot across much of the eastern United States was the increased amount of urbanization.  That led to warmer overnight low temperatures and contributed to some of the warmest months on record in the Nation’s Capital.  This summer has tied the 2011 record (six) of number of days where low temperatures remained at or above 80 degrees. 

Through August 21, Washington, D.C.’s average high temperature this month was 92.7 degrees.  National Weather Service records indicate that’s above the August’s record average high temperature of 92 degrees from 1980.  However, the several days this week with high temperatures in the 80s will lower that number.  Nevertheless, this August remains poised to finish as one of the warmest on record in the Nation’s Capital and many eastern cities.

Washington, D.C. averages 36 days at or above 90 degrees in a given year and 2016 has already had 45 such days.  The record for most 90 degree days in a given year is 67 which occurred in 2010 and 1980.  My colleagues and I on the WUSA9 weather team expecting more 90 degree heat in the Nation’s Capital later in the week, so the August total of 17 such days will only grow.

Most August days at/above 90 degrees in Washington, D.C. (DCA – Source: NWS)

1.  22 (1980)
2.  21 (1943)
3.  20 (1988, 1983)
5.  19 (2002, 1995, 1966)
8.  18 (1900)
9.  17 (1968, 1872)  --> 2016 (Through August 21)

Atlantic Hurricane Update

Hurricane Earl nearing Belize on 8-3-16  (Source: NASA)

Tropical Storm “Fiona” developed in the Atlantic Ocean this week, but hasn’t been a particularly memorable or intense system.  So far this season there have been a total of six tropical storms, including two minimal (Category 1) hurricanes.  Earlier this month, atmospheric scientists at NOAA and Colorado State University both updated their seasonal hurricane forecasts.

A team of Colorado State University scientists called for an additional 11 tropical storms, 4 hurricanes and 2 major hurricanes.  A “major” hurricane is defined as a Category 3 or higher storm on the Saffir-Simpson Scale and is characterized by 111/+ mph sustained winds.  NOAA updated its forecast saying there’s a 70% chance for a seasonal total of 12 – 17 tropical storms, 5 – 8 hurricanes and 2 – 4 major hurricanes.  That includes the six tropical storms and two hurricanes that have already developed.  An average hurricane season in the Atlantic Ocean includes approximately 10 tropical storms, six hurricanes and two major hurricanes.

This has been an interesting season in the Atlantic Ocean so far.  Distinguished atmospheric scientist, Dr. Philip Klotzbach, of Colorado State University noted that tropical storm Danielle became the earliest fourth named tropical storm on record when it developed on June 20.  However, following the fast start to the season July didn’t see a single named storm.  An increased amount of wind shear in the tropics helped create unfavorable conditions for tropical storm development.  Tropical storms and hurricanes require warm water and calm winds – or an absence of wind shear to develop.

There are a few other significant things going on in the tropics.  There hasn’t been a hurricane in the Gulf of Mexico in nearly three years since Hurricane Ingrid in September 2013, which recently set a new record.  There have been several tropical storms, though, in the nearly three years since Ingrid – including tropical storm Colin that made landfall in Florida earlier this year.

Also, the United States hasn’t had a landfall from a major hurricane in nearly 11 years, since Wilma in October 2005.  That shattered the previous record of six years (1979 – 1985) with a landfalling major hurricane.  Wilma was also the last hurricane – of any intensity – to make landfall in Florida.  Although, there have been more than two dozen (27) major hurricanes in the Atlantic Ocean since Wilma but the United States has been fortunate that none have made landfall.  While, significant hurricanes like Ike in 2008 and Irene in 2011 have made landfall in the United States, they were not “major” at their time of landfall.

Coastal population and development continue to rise and the longer the streak goes without a major hurricane, the likelihood of complacency among coastal residents will increase.  It’s important to remember the lessons of major past hurricanes such as Charley in 2004 and Katrina in 2005 and be prepared when the streak comes to an end.