Weather Quiz

 

Hurricane Matthew, October 2016 (Source: NOAA)

What two catastrophic Category 5 hurricanes tracked across the western Atlantic and Caribbean Sea in September 2017?

A.  Katrina, Wilma

B.  Isabel, Ivan

C.  Irma, Maria

D.  Dorian, Michael

Dangerous September Hurricanes

 

Hurricane Rita, September 2005 (Source: NOAA)

The tropical Atlantic has gotten more active since the calendar turned to September following the quietest August since 1997.  There have been some intense and destructive Atlantic hurricanes over the last two decades in September, such as the following.

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.  However, its maximum sustained winds of 185 mph tied it with Hurricane Gilbert (1988) and Hurricane Wilma (2005) for second highest wind speeds in an Atlantic hurricane.  Not only was Dorian the strongest hurricane on record to make landfall in the Bahamas, it was also a very slow moving storm that was both destructive and deadly.

Hurricane Irma (2017): Irma was another long-lasting Cape Verde hurricane that reached Category 5 intensity on two separate occasions.  At peak intensity, Irma had sustained winds of 180 mph and a minimum central air pressure of 914 mb (standard sea level air pressure is approximately 1,013 mb).  Irma left a deadly trail of destruction across much of the Caribbean and ultimately made landfall in Florida as a Category 4 hurricane.  It was the first Category 4 hurricane to make landfall in Florida since Charley in 2004.  Ultimately, Irma killed dozens in the United States and did $59.5 billion in damages in 2022 dollars.  It ranks as the sixth costliest natural disaster in U.S. history, according to NOAA.

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 with maximum sustained winds of 180 mph and a minimum central pressure of 895 mb.  Rita remains the fourth strongest Atlantic hurricane on record behind only Wilma, Gilbert and the unnamed 1935 Florida Keys hurricane.  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 $27.2 billion worth of damages in 2022 dollars and ranks among the Top 15 costliest U.S. natural disasters.

Hurricane Isabel (2003): Once a Category 5 over the open Atlantic, Isabel made landfall in North Carolina as a Category 2 hurricane on September 18.  Isabel tracked west of Washington, D.C. as it weakened and brought the D.C. Metro Area a significant amount of heavy rain and gusty winds.  Over one million power outages were observed around the Nation’s Capital, with significant coastal flooding in Old Town Alexandria, Virginia and in Annapolis, Maryland.   The highest tide in Annapolis reached 7.58 feet above normal, breaking the 1933 hurricane record.  Flooding in Georgetown occurred with flood stage reaching 11.3 feet above normal, which broke the 1933 hurricane surge record. 

D.C.’s Fall Transition

 

August 2022 finished as a warmer and drier than average month in the Nation’s Capital for the first time since 2019.  Not only did the month finish 1.0° warmer than average at Reagan National Airport, but it was even warmer at Dulles Airport, finishing 1.8° warmer than average (combining daily high/low temperatures).  It was also drier than average with 2.42” of rain, well below D.C.’s August average of 3.25”.

September features some of the nicest 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 fall throughout September and sunset will occur at 6:53 p.m. on September 30.  The combination of a reduced amount of daylight and a lower sun angle contributes to the cooler temperatures as September wears on. 

D.C.’s hottest September temperature on record is 104° on September 7, 1881.  Triple-digit heat during the month of 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, D.C.’s coolest September temperature on record is 36° from September 23, 1904.  Seven of the last 10 September’s have been warmer than average in the Nation’s Capital.  To add to that, 5 of D.C.’s 10 warmest September’s on record have occurred since 2005.

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.  D.C.’s driest September on record in 2005 (0.11”) was followed by the wettest October on record (9.41”).  There has been an even 50/50 split between wetter and drier than average September’s in the Nation’s Capital over the last 20 years.

The cooler autumn weather will be a relief to many Washingtonians following another warmer than average summer.  The first half of September often sees a continuation of summer-like heat in the D.C. Metro Area as summer weather only gradually gives way to fall.  Such was the case yesterday with a high of 91°.  September has an above average chance for warmer than average temperatures combined with an equal chance for above or below average rainfall, according to NOAA’s Climate Prediction Center.