Notable September Category 5 hurricanes

 

Hurricane Lee, Category 5  (Source: NOAA)

Hurricane Lee rapidly intensified into a powerful Category 5 hurricane on September 7 with peak sustained winds so far of 165 mph and a minimum central air pressure of 926 millibars.  Category 5 hurricanes feature sustained winds around the center of circulation – or the “eye” – of at least 157 mph.  Category 5 storms only form under the rarest of circumstances because they require ideal environmental and atmospheric conditions.  Here are some memorable September Category 5 Atlantic storms.

Hurricane Dorian (2019): Dorian made landfall in the Bahamas on September 1 as a Category 5 storm with sustained winds of 185 mph.  That tied it with the 1935 Labor Day hurricane, which made landfall in the Florida Keys, as the most intense landfalling hurricane in the Atlantic Ocean Basin.  It was the most intense based on wind speed and not air pressure.  Dorian’s minimum central air pressure of 910 millibars (mb) was the ninth lowest on record.

Hurricane Rita (2005): Rita was the third of four Category 5 hurricanes that occurred during the record-setting 2005 Atlantic hurricane season.  It reached its peak intensity on September 21 while in the Gulf of Mexico with maximum sustained winds of 180 mph and a minimum central air pressure of 895 mb.  Rita remains the fourth strongest Atlantic hurricane on record based on air pressure.  According to the National Hurricane Center, Rita weakened to Category 3 intensity with sustained winds of 120 mph before making landfall September 24 near the Louisiana and Texas state border.  Rita caused an estimated $28.3 billion worth of damages in 2023 dollars and ranks among the Top 15 costliest U.S. tropical cyclones, according to NOAA.

Hurricane Ivan (2004): Ivan was the strongest hurricane of a busier-than-average hurricane season.  It was a Category 5 storm that caused significant damage in Jamaica, the Dominican Republic, and the Cayman Islands.  Air pressure is considered a more accurate measure of hurricane intensity than wind speed, and at peak intensity Hurricane Ivan’s lowest air pressure was 910 millibars.  Its highest sustained winds reached 165 mph.  Fortunately, Ivan weakened to Category 3 intensity before it made landfall in Alabama on September 16.  It caused nearly $33.0 billion in U.S. damages (2023 dollars), according to NOAA.

Isabel (2003): Isabel reached its peak intensity on September 11 while over the open Atlantic, with maximum sustained winds of 165 mph and a minimum central air pressure of 915 millibars.  Isabel weakened to Category 2 status before its landfall in North Carolina on September 18.  Despite weakening, Isabel caused major flooding and damage across much of the Mid-Atlantic Region and northeastern United States, with an estimated cost of $9 billion (2023), according to NOAA.  In the D.C. Metro Region, Isabel caused approximately one million power outages. 

DC’s hot start to September

 

Cooler temperatures are on the way in the DMV  (Source: NOAA)

Temperatures in the nation’s capital will reach the 90s on five days this week.  That’s DC’s highest such total since September 2019, which finished with nine days in the 90s.  One record high was set at National Airport yesterday, with the potential for another today and tomorrow.

Washington, D.C. has averaged between three and four September days with highs in the 90s over the last 30 years.  It’s not unusual for the first week of September to feature the hottest weather of the month.  What is unusual, however, is the intensity of this week’s heat when multiple record highs will be set at DC’s three area airports (Reagan National, Dulles and BWI-Marshall).

The intensity of this week’s heat is also noteworthy as it followed DC’s first cooler than average August since 2017.  DC’s hottest temperature this year, 98° occurred on September 4.  That was also DC’s hottest temperature since June 17, 2022, when it was 99°.  Dulles Airport also tied its record high for the entire month of September when it was 99° on September 3 and 4.    

NOAA’s Climate Prediction Center expects cooler, more fall-like temperatures to return this weekend and continue through the middle of September.  That’s doesn’t mean the nation’s capital would be finished with 90° for the year. 

While any 90° heat in October is a very rare occurrence in the nation’s capital, it isn’t unprecedented.  There have been only six Octobers dating back to 1993 that DC residents have had temperatures in the 90s.  The most recent occurrence was on October 2, 2019.  The latest in the year Washingtonians have experienced 90° heat is October 11. 

Despite the historic heat over the first week of September, it’s too early to say whether this month will finish among DC’s warmest.  Either way, five of DC’s 10 warmest September’s have occurred just since 2010.

1.  77.1° (1980)
2.  76.5° (2019)
3.  76.0° (2016, 1930)
5.  75.5° (2018, 2010)
7.  75.4° (1998)
8.  75.0° (2005, 1970)
10.  74.9° (2015)

DC’s unofficial start to fall

 

NOAA's September temperature outlook

Last month finished as DC’s first cooler than average August since 2017.  It also featured a below average number of 90° August days with nine in the nation’s capital compared to the 30-year average of 11 – 12.  Last month also finished as slightly wetter than average with 3.71” of rain in Washington, DC.  NOAA’s August rainfall average for the nation’s capital is 3.25”.

September features some of the best weather of the year in the nation’s capital as fall officially gets underway.  Average daily high/low temperatures drop from 85°/69° on September 1 to 75°/59° by the end of the month.  The amount of daylight also continues to decline throughout September.  Sunset will occur at 6:53 p.m. on September 30.  The combination of reduced daylight and a lower sun angle contributes to the cooler average temperatures as September wears on. 

Five of DC’s 10 warmest September’s on record have occurred since 2005.  DC’s hottest September temperature on record is 104° on September 7, 1881.  Triple-digit heat during September is a rarity in the nation’s capital and has occurred only four times since 1871.  The most recent was 101° on September 2, 1980.  By comparison, DC’s coolest September temperature on record is 36° from September 23, 1904.

Although Washington, D.C. averages 3.93” of September rainfall, the amount of rain can fluctuate wildly year-by-year.  September can be a very wet month if decaying tropical systems bring appreciable rainfall.  Such was the case with Floyd in 1999, Isabel in 2003 and Florence in 2018.  This month can also be very dry in the Nation’s Capital.  The driest September on record in 2005 (0.11”) was followed by the wettest October on record (9.41”).

The cooler autumn weather that occurs as September wears on is a relief to many Washingtonians following the typically hot and humid summer conditions.  However, the first half of September often sees a continuation of summer-like heat in the DC Metro Area.  That’s going to happen over the next few days with near-record heat through the middle of the upcoming week. 

This September has an above average chance for warmer than average temperatures in the nation’s capital combined with an equal chance for above or below average rainfall, according to NOAA’s Climate Prediction Center.