Will October’s weather be frightful or delightful ?

 

The feel of fall is in the air !

September 2023 finished as a warmer and drier than average month in the nation’s capital.  DC’s average September temperature was a full degree above average largely due to the record-setting heat early in the month.  It was also slightly drier than average despite beneficial rainfall from the remnants of Tropical Storm Ophelia. 

Dulles Airport, meanwhile, had its sixth warmest September (2° above average) with its first instance of 100° September heat and finished with its 12^th wettest.  Dulles finished with 6.65” of September rainfall compared with only 3.60” at National Airport.  That helps illustrate how localized much of last month’s rain was, particularly with the remnants of Ophelia.

October is the second of three months of meteorological fall and often features some of the finest weather of the year with mild to warm days and crisp, cool nights.  Average daily high/low temperatures in the nation’s capital range from 75°/58° on October 1 to 64°/46° on Halloween.  D.C. warmest October temperature on record of 98° occurred four years ago today on October 2, 2019. 

D.C.’s coolest October temperature of 26° has occurred twice, most recently on October 31, 1917.  Temperatures at or below freezing in October are quite rare in the nation’s capital and none have occurred since October 20, 1992 (32°).  Eight of the last 10 Octobers have been warmer than average in Washington, D.C.

The nation’s capital averages 3.66” of rainfall with seven of the last 10 October’s having been drier than average.  Weakening tropical systems can sometimes impact the D.C. Metro Area in October with heavy rain and severe weather.  Such was the case with the remnants of Hurricane Opal in 1995 and post-Tropical Storm Sandy in 2012. 

Infrequently, D.C. Area residents can get an early taste of winter with light October snowfall.  Although the nation’s capital doesn’t see enough October snowfall to produce an average amount, a trace of snow (too little to measure) does occur every once in a while, with the most recent such occurrence in 2011.  D.C. earliest accumulating snowfall occurred on October 10, 1979 with 0.3” at National Airport.

NOAA’s Climate Prediction Center expects October 2023 to be a warmer and drier than average month in the nation’s capital.  That would be in contrast to last October that finished as DC’s coolest since 2003.

Atlantic tropical update

 

Saffir-Simpson Hurricane Wind Scale (Source: WUSA9)

Atmospheric and environmental conditions reach their annual peak for tropical storm and hurricane development across the Atlantic Ocean in September.  September 2023 has lived up to its billing as the most active month of the Atlantic hurricane season. 

Tropical Storm Rina developed on September 28 and that was the 18^th storm of 2023.  An unnamed subtropical storm developed in January giving 2023 a total-to-date of 18 storms (17 named), with 6 hurricanes and 3 “major” hurricanes.  A “major” hurricane has maximum sustained winds of at least 111 mph that makes it a Category 3 storm.

When NOAA issued its early August update to its seasonal hurricane forecast, they increased the number of storms from what was forecast at the start of the season in June.  The major question was would near-record high sea-surface temperatures offset the El Nino conditions that have developed?  The short-answer is, yes, given how busy the tropical Atlantic has been over the last six weeks.

When Rina was named a tropical storm, it became the 13^th named storm in the Atlantic since August 20.  According to a tweet from Colorado State University hurricane expert, Dr. Philip Klotzbach, “That's the most on record to form between August 20 - September 28, breaking old record of 12 Atlantic named storm formations set in 2020.”  Fortunately, not all of these storms were intense or had direct impacts on the United States.

However, Hurricane Idalia made landfall in Florida as a Category 3 storm and Tropical Storm Ophelia made landfall in North Carolina.  Ophelia’s remnants brought beneficial rainfall to the Mid-Atlantic Region.  Hurricane Lee also became the Atlantic’s first Category 5 hurricane since Lorenzo in 2019.  Fortunately, it had no direct impacts on the United States.  Lee weakened before it made landfall in Atlantic Canada as a strong extratropical, or non-tropical storm.

If no more named storms were to develop in 2023, then this season would finish with an above average number of named storms, but a near average number of hurricanes.  An “average” Atlantic hurricane season has 14 tropical storms, of which 7 develop into hurricanes with 3 major hurricanes.

If anything, though, the last few seasons have illustrated that October and November can still be active in the tropical Atlantic.  Hurricane Nicole made landfall in Florida as a Category 1 storm last November.  Meanwhile, Hurricanes Eta and Iota both reached Category 4 intensity in November 2020.  Hurricane Michael also made landfall in the Florida panhandle as a Category 5 storm in October 2018.  This illustrates why it’s important to monitor the tropics until the season ends on November 30.