Sandy – A Decade After the Disaster

 

"Sandy" nearing landfall in New Jersey (Source: NOAA)

Today is the 10^th anniversary of “Superstorm” Sandy’s landfall in New Jersey.  The former hurricane reached its peak intensity several days earlier as a Category 3 hurricane with sustained winds of 115 mph and a minimum central air pressure of 940 millibars.  That also made it the strongest hurricane of the 2012 Atlantic hurricane season. 

Shortly before its landfall in New Jersey, Sandy moved over cooler water and into an increasingly unfavorable environment for a tropical storm or hurricane.  Consequently, the structure of the storm changed and Sandy was declared a “non-tropical” or “post-tropical” storm.  That led to a great deal of confusion for many residents of the Mid-Atlantic and northeastern United States who thought Sandy was no longer a threat once the hurricane watches and warnings were discontinued. 

Sandy was dubbed a “Superstorm” and made landfall at the equivalent of a Category 1 hurricane with sustained winds of 80 mph and a minimum central pressure of 946 millibars.  As Sandy transitioned to a non-tropical storm, the wind field and rain shield associated with it both increased in diameter.  That allowed for a larger area to be impacted. 

Sandy had the second-lowest pressure of any storm to come ashore north of Cape Hatteras, N.C.  Atlantic City, Baltimore, Philadelphia, and Trenton all set records for the lowest air pressure reading, according to NOAA.  The lower the air pressure is, the stronger the storm is and higher the winds tend to be with a stronger pressure gradient (a greater difference in air pressure over a shorter geographic distance produces higher wind speeds).  Record flooding occurred in New Jersey, New York City and on Long Island, N.Y. with epic storm surges.  Tens of thousands were left without electricity or heat for weeks.  Record rainfall totals also occurred in the D.C. Metro Area with two-day rainfall totals (October 29-30).

October 29:  DCA (National Airport): 3.85” / Dulles Airport (IAD): 4.26” / BWI: 5.51”

October 30:  DCA: 0.84” / IAD: 1.00” / BWI: 0.92”

There were eye-popping snowfall totals as Sandy pushed further inland and into the higher elevation of the Appalachian Mountains.  In West Virginia, for example, Richwood saw 36” of snow, Snowshoe got 32” and Davis had 28”.   In all, Sandy did an estimated $81.9 billion in damages (2022 dollars) and is the fourth most destructive “hurricane” in U.S. history, behind only Katrina, Harvey and Maria.  Sandy also claimed almost 150 lives in the United States.

D.C.’s Rare October Weather

 

October 2022 got off to an unusually cool and wet start in the Nation’s Capital.  However, October is well-positioned to finish as a drier than average month.  October being both cooler and drier than average in the Nation’s Capital is relatively rare with only one such month over the last decade. 

Nine of the first 11 days of October were cooler than average in D.C.  The high temperature of only 55° on October 4 set a record for coolest daily high temperature.   That was the first such record in the Nation’s Capital since May 9, 2020.   D.C.’s average high on October 4 is 74° and a high of 55° isn’t “average” until late-November.  The low temperature of 38° on October 19 was D.C.’s coldest October temperature in nearly four years since October 22, 2018 (also 38°).

There have been some warmer than average days in the Nation’s Capital this month, but they haven’t been as common as in recent October’s.  D.C.’s high of 81° on October 7 guaranteed this month will be the seventh consecutive October with 80° warmth.  By comparison, Washingtonians basked in eight days of 80° warmth during the unusually warm October 2021.   Despite a few mild days this week, an expected cool down later this week will guarantee this October will finish as D.C.’s first cooler than average October since 2015.

Rainfall has been spotty this month with a total of 1.75” in the Nation’s Capital through October 5.  However, since then D.C. had a combined rainfall total of only 0.87”, giving the Nation’s Capital a monthly total of 2.62”.  Given NOAA’s 8-14 day outlook for below average precipitation in the D.C. Metro Area, Washington, D.C. will fall well short of its October rainfall average of 3.66”.  That will make this D.C.’s first cooler and drier than average October since 2015.

NOAA’s early outlook for November predicts the Nation’s Capital will see warmer and drier than average weather during the first one to two weeks.  That would be the opposite of last November that began with six cooler than average days.  November is the third and final month of meteorological fall.  Average temperatures and the amount of daily sunlight decrease throughout the month.

Looking Ahead to Winter

 

Average high temperatures in Washington, D.C. range from 75° on October 1 to 64° on Halloween.  However, there have only been six warmer than average days this month in the Nation’s Capital through October 21.  That’s put this month in a strong position to finish as D.C.’s first cooler than average October since 2015.  Average monthly temperatures (combining daily high and low temperatures) in the Nation’s Capital have been 4.7° cooler than average so far this month with near average rainfall. 

Some may wonder if a cooler than average October combined with La Nina conditions is a reliable indicator of what the upcoming winter will be like.  October weather by itself is not a good indicator of the looming winter’s weather.  October 2015, for example, while cooler and drier than average, preceded a warmer than average winter season in the Nation’s Capital.  December 2015 finished as D.C.’s warmest on record and that set the trend for the entire 2015-2016 winter.  Should October 2022 finish as a cooler and wetter than average month, it would be the first such occurrence in the Nation’s Capital since 2011. 

However, the 2015-2016 winter season featured a strong episode of El Nino so the overall weather pattern was a lot different than what NOAA expects for the upcoming 2022-2023 winter season.  NOAA’s Climate Prediction Center released an update on October 13 in which they said there’s a 75% chance La Nina conditions will continue through the 2022-2023 winter season.  The 2011-2012 winter could be a better analog to this autumn since it also featured a moderate episode of La Nina. 

La Nina features the unusual cooling of the waters in the tropical east Pacific Ocean (off the west coast of Mexico).  That’s the opposite of El Nino which features the warming of the waters off the west coast of Mexico.  A La Nina winter in the D.C. Metro Region tends to be warmer and drier than average.  Such was the case during the 2011-2012 winter season when December, January and February saw a combined total of only 2.0” of snow in Washington, D.C.  By comparison, the Nation’s Capital averages 13.7” of annual snowfall according to NOAA. 

The last two winters have also featured moderate intensity La Ninas with below average snowfall in the Nation’s Capital.  There are many factors that go into forecasting seasonal weather, with the presence of La Nina or El Nino being only one, so it isn’t possible to base a seasonal forecast entirely on that.  In any event, this October is well-positioned to finish as D.C. coolest in at least seven years.