A Wet Month Comes to a Close

 

August 2021 will finish as a warmer and significantly wetter than average month in Washington, D.C. That’s despite a cool and almost fall-like start to the month.  In fact, temperatures on six of the first seven days of August were cooler than average.  Washingtonians didn’t see the first 90° August day until August 6. 

This month’s weather has been streaky.  Following the cool start, Washingtonians had a 7-day heat wave from August 8 – August 14.  The tail end of that heat wave coincided with the start of a stretch of nine consecutive days with measurable rainfall from August 13 – August 21.  During those nine days, a total of 6.92” of rain accumulated at National Airport.  Most of that rainfall occurred on two days when a combined total of 4.66” fell on August 14 and August 20.

This rainy stretch of weather helped prevent daily high temperatures from soaring as evidenced by only three days in the 90s during the nine-day period.  Washingtonians know triple-digit heat can occur at any point during the month.  But the frequent clouds and rainfall have prevented any such weather this month.

Showers and thunderstorms have been an almost daily occurrence in the D.C Metro Area this month.  The nature of summertime showers and thunderstorms is for them to often be spotty and localized.  That means while some areas can see appreciable rainfall, others not far away see little or no rain.  For example, through August 30, National Airport had 9.07” of rain.  Meanwhile, Dulles Airport had only 4.91”.  However, Dulles Airport will also finish with a wetter than average August for a fifth consecutive year.  Average monthly temperatures at Dulles Airport will also finish warmer than average for a fourth consecutive year. 

The average monthly temperature at National Airport (combining daily high/low temperatures) will finish more than 1° above average.  August 2021 will be D.C.’s fourth consecutive warmer than average August.  The hottest temperature in the Nation’s Capital this August was 96° that occurred on three consecutive days (August 11 – 13).  Meanwhile the coolest day this month was August 7 with a high/low temperature of 77°/69°.

Wettest August’s in Washington, D.C.  (Source: National Weather Service)

1.  14.41” (1928)
2.  14.36” (1906)
3.  14.31” (1955)
4.  12.93” (1875)
5.  9.91” (1933)
6.  9.75” (1905)
7.  9.49” (1942)
8.  9.17” (1967)
9.  9.07” (2021)
10.  9.00” (1948)

Ida Makes History

 

Hurricane Ida making landfall, 8-29-2021 (Source: WUSA9)

Hurricane Ida earned a rather dubious distinction yesterday.  Not only did Ida make landfall in Louisiana on August 29 – the 16^th anniversary of Hurricane Katrina – but its sustained winds were even stronger than Katrina’s at landfall.  Ida made landfall as a Category 4 hurricane with sustained winds of 150 mph and a minimum central air pressure of 930 millibars (mb).  By comparison, standard sea level air pressure is 1013.25 mb. 

Ida’s tied with Hurricane Laura (2020) and an unnamed 1856 hurricane that also had 150 mph sustained winds as the strongest hurricanes to ever make landfall in Louisiana based on wind speed.  While Katrina was a Category 5 hurricane over the open Gulf of Mexico, it weakened to Category 3 intensity with 125 mph sustained winds before it made landfall.  Since Katrina was so powerful over the Gulf, it generated a storm surge that was even larger and more destructive than it would normally be in a Category 3 hurricane.

Ida weakened to a tropical storm today as it continues to track further inland bringing flooding rainfall, damaging winds and isolated tornadoes in its path.  Even after Ida is no longer a tropical system, its remnant moisture will continue to have far-reaching impacts in areas well inland.  Flash flood watches have been issued for much of D.C. Metro Area in anticipation of heavy rain expected on Wednesday into Thursday.  Following a very wet second half of August, additional rainfall is not welcome news in the Nation’s Capital.

Hurricane Ida joined a memorable list of destructive Atlantic hurricanes over the last 20 years that have started with the letter “I.”  Some of those storms include Irma (2017), Irene (2011), Ike (2008), Ivan (2004), and Isabel (2003).  Irma, Ivan and Isabel were all Category 5 hurricanes, but weakened prior to making landfall in the United States.  Ivan set the record for spawning the most tornadoes of any tropical system in U.S. history.  Meanwhile, Irma ranks among the five costliest natural disasters on record.

All of those previous “I” storms had their names subsequently retired by the World Meteorological Organization for being both destructive and deadly.  Ida will likely see its named retired and replaced next spring when the WMO meets to discuss the 2021 Atlantic hurricane season.

With all natural disasters, there’s both a human toll as well as a cost in terms of property damage.  It will take some time, however, to determine how costly Hurricane Ida has been.  Hurricane Ida made 2021 the fifth consecutive season at least one major hurricane has made landfall in the United States.

Weather Quiz

 

True or False.

August 2021 will finish as one of the Top 10 rainiest on record in the Nation’s Capital.