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Monday, July 8, 2019

Something's Rotten in D.C., and It Isn't Those Rain Totals

By Chris Martz | July 9, 2019



It seems as if every day, there's someone linking ordinary and not-so-ordinary weather events to the "climate crisis." Dare I say that we should actually do a little fact-checking first. 
"Nope, we know the answer already. Climate change causes all weather events, big and small, normal and rare."

 Yet, while my italicized quote is supposed to be funny, that kind of mentality has embedded itself into our reality. 

On Monday, July 8, Democratic congresswoman Alexandria Ocasio-Cortez (AOC) stated that "Unprecedented flooding is quickly becoming a new normal. Despite that, Republicans are tripling down on fossil fuels w/no plan to transition off them, or make the critical infra investments we need to prep for the climate crisis. Each day of inaction puts more of us in danger."
The irony of her statement － when was the last time a politician actually cared about the people they represent? Okay, okay, I'm going to stick to the science!

 The congresswoman also stated that extreme weather or weather-related events like flooding and wildfires have gotten worse due to the "climate crisis." (I'm using "climate crisis" in order to be more scientifically precise, like The Guardian stated they would do with their articles. That was pure sarcasm).
Her reference to "unprecedented flooding" was fueled off of headlines detailing flooding in the Washington, D.C. area (where I live and forecast the weather). Indeed, she was right in the sense that the flooding on Monday was impressive, but the usual scaremongering tactic of blaming fossil fuel emissions on the event is just plain pseudoscience and superstition, and doesn't root itself in reality.

 According to the National Weather Service office in Sterling, Virginia, official observations from Reagan National Airport indicate that 3.44 inches of rain fell Monday, July 8. This rainfall was not only a record for the date (old record was 2.16 inches from 1958), it was a little over 92% of D.C.'s average July monthly total rainfall of 3.73 inches!
All of this was caused by a complex of slow-moving thunderstorms that rolled through the area Sunday evening and Monday morning (I can confirm since I live in the area). This was not caused by magic CO₂ fairy dust in the atmosphere. 

 Flash floods from thunderstorms generally occur when thunderstorm cells are slow-moving, or when different thunderstorm cells move over the same area over and over again.¹ The severity of a flash flood － in terms of how fast it develops and how high the water levels get － depend upon factors like the duration of the rain, the rainfall intensity and terminal velocity of raindrops, and/or soil moisture.¹ Sunday evening and Monday morning, the storms were slow-moving and rainfall intensity was high. In addition, last year (2018) was the wettest year on record in Washington, D.C. with 66.28 inches of precipitation falling on the city.² 2019 has also been a pretty wet year, with 27.12 inches of rain falling so far.² Thus, soil moisture remains high, and as a result, excess water from rain or runoff can't seep into the ground, creating a higher risk for flash floods.
Figure 1. Total precipitation January - December in Washington, D.C. 1872 - 2018,
So, with that said, does her claim about "unprecedented flooding" in D.C. hold any water? Spoiler alert, it doesn't!

 Before I show the statistics, her statement doesn't even make any sense. If each new flood is "unprecedented," then that's climatologically not "normal." So how can it become normal? Maybe she means that flash/inland/river flooding is the new normal? If so, that's still wrong. Two strikes in a row AOC, the third is OUT.

 Washington, D.C. has a long history of flash flood events, river flooding, and heavy rainfall events, most of which are not even noteworthy because they happen so often, especially the during spring and summer as daytime heating and high dew points act as "trigger mechanisms" to initiate thunderstorm development in the afternoon hours.


Heavy Rainfall Events

 Meteorologist Kevin Williams of Rochester, New York made note that of the top ten heaviest 24-hour rainfalls in D.C., only two of the ten have occurred this century. Of the eight heaviest 24-hour rainfalls to be officially recorded in D.C. during the 20th century, seven of them occurred prior to 1975, and five occurred prior to 1970. 
So, obviously, heavy rainfall events in D.C. are not a new thing. What about actual floods?

Some Select Flash Floods & River Flooding in D.C. 

David Birch, a friend of mine and a well-known solar researcher in the climate community sent me this link Monday afternoon, which has a list and description of some of Washington, D.C.'s largest flood events in memory.

 So, let's break it down.

 1. The "Great Fresh Flood" of May 1771 was devastating to the Virginia colony and Washington, D.C. area.³ ⁴ The Virginia Gazette reported, "...From the mountains, to the Falls, the low Grounds have been swept of almost every Thing valuable; and the Soil is so much injured that it is thought not to be of Half its former Value, and a great Part is entirely ruined...³

 2. On June 2, 1889 the Potomac River crested 12.5 feet above flood stage. Many streets, including Pennsylvania Avenue were flooded (Figure 2).⁴
Figure 2. Pennsylvania Avenue flooded on June 2, 1889 in Washington, D.C. Photo credit: Library of Congress.
3. The Flood of March 17-19, 1936 was one of Northern Virginia's, Maryland's, and D.C.'s worst natural disasters in history.⁵ This flood is often noted as the "Record Flood of 1936," "Great Potomac Flood," or the "St. Patrick's Day Flood of 1936."⁵

 March of 1936 was pretty warm in Washington, D.C., averaging 3.5°F above normal for the month, despite frequent drastic temperature swings from the 40s to the 70s and back.²

 Most of Eastern West Virginia, Northern Virginia, and Maryland had received their entire March monthly average rainfall by mid-month.⁵ While most of the rainfall events were relatively small, the high frequency of them that March allowed stream water levels to increase. 

 The storm that caused the major flooding was on St. Patrick's day in 1936, when a deepening low in the Carolinas pushed southeast winds and moisture into the region causing intense rainfall.⁵ While most areas in and around the D.C. area saw less than two inches of rain, areas to the west, like the Blue Ridge Mountains received well over four inches of rain in that two day period.⁵ The list below is from the National Weather Service. You can see just how impressive those two-day totals were (Figure 4).
Figure 3. Two-day rainfall totals from the March 1936 storm.
4. The "Record Flood of 1942" unfolded over an eight-day period; October 11-18.⁴ During this event, D.C. picked up over six inches of rain, and floodwaters reached the steps of the Jefferson Memorial (Figure 4).⁴

Figure 4. Jefferson Memorial steps flooded in October 1942 flood.
5. The Flash Flood of August 11, 2001 was one for the books (Figure 5). What's odd about this flash flood event was that it occurred in a narrow band stretching from Warrenton, Virginia to Washington, D.C.⁴ Some storm reports from D.C. and nearby communities noted that upwards of seven inches of rain fell that day.⁴ Reagan National Airport only received 0.92 inch of rain during the event.²
Figure 5. Flash flood of August 11, 2001.



Weather vs. Climate

People like Representative Cortez seem to have a very difficult time grasping the fundamental differences between weather and climate, which is the fact that weather is based on short-term atmospheric conditions and climate is based long-term trends. 

Any individual weather event － regardless of how extreme it is and whether or not it's unprecedented － can simply not be used as evidence for OR against changes in Earth's climate system. The atmosphere － as we know － is very chaotic in nature and any type of extreme weather event is bound to happen at some time or another notwithstanding global average temperature change. 

If you look at the trends in global lower tropospheric temperature since 1979, you'll see that they have undoubtedly gone up, yet we've always had floods (hear that AOC?), we've always had hurricanes, we've always had tornadoes, wildfires, dust-devils, droughts, heat waves, cold waves, thunderstorms, blizzards, and monsoon seasons. While the frequency and/or intensity in such events may or may not alter in either direction due to changes in the climate, because they have always happened, because they're prone to happen, and because there's a lack of sufficient global long-term data, it is extremely difficult and arrogant to pinpoint one weather event as evidence of a "climate crisis."

Flash flood events like the one that occurred on Monday in D.C. are associated with thunderstorms, which are considered "severe convective storms." According to the National Academy of Sciences (NAS), there is very little evidence to link thunderstorms to man-made climate change, global warming, the climate crisis, or ecological breakdown － whichever way you'd like to call it.⁶

Figure 6. Climate change and extreme weather - National Academy of Sciences (NAS).
If I were to sum up this nonsense in one sentence I'd say, "There's something rotten in D.C., and it isn't those rainfall totals, it's clueless politicians."
REFERENCES

[1] "Thunderstorm Hazards - Flash Floods" National Weather Service. Accessed July 9, 2019. https://www.weather.gov/jetstream/flood.

 [2] xmACIS2. Accessed July 9, 2019. https://xmacis.rcc-acis.org/.

 [3] Yeck, Joanne. "The Great Fresh of 1771." Slate River Ramblings... March 13, 2017. Accessed July 9, 2019. https://slateriverramblings.com/2017/03/13/the-great-fresh-of-1771/.

 [4] Ambrose, Kevin. "Floods - Washington Area Floods." WeatherBook.com. Accessed July 9, 2019. https://www.weatherbook.com/flood.html.

 [5] "1936 Flood Retrospective." National Weather Service. Accessed July 9, 2019. https://www.weather.gov/lwx/1936Flood.

[6] "Climate Change and Extreme Weather." Penn State Department of Meteorology and Atmospheric Science. Accessed July 9, 2019. https://www.e-education.psu.edu/meteo3/l10_p9.html.
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2 comments:

  1. DaveAndrewsJuly 9, 2019 at 3:08 AM

    Good stuff. Very interesting. Providing some balance to the alarmist AOC et al.

    ReplyDelete

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