Sun. Oct 20th, 2019

One thing’s Rotten in D.C., and It Isn’t These Rain Totals

Reposted from Superior Climate Information Weblog

By Chris Martz | July 9, 2019

It appears as if day by day, there’s somebody linking extraordinary and not-so-ordinary climate occasions to the “local weather disaster.” Dare I say that we should always truly do some fact-checking first.

“Nope, we all know the reply already. Local weather change causes all climate occasions, huge and small, regular and uncommon.”

But, whereas my italicized quote is meant to be humorous, that sort of mentality has embedded itself into our actuality.
On Monday, July eight, Democratic congresswoman Alexandria Ocasio-Cortez (AOC) said that “Unprecedented flooding is shortly turning into a brand new regular. Regardless of that, Republicans are tripling down on fossil fuels w/no plan to transition off them, or make the crucial infra investments we have to prep for the local weather disaster. Every day of inaction places extra of us in peril.”

The irony of her assertion - when was the final time a politician truly cared in regards to the folks they signify? Okay, okay, I’m going to stay to the science!
The congresswoman additionally said that excessive climate or weather-related occasions like flooding and wildfires have gotten worse as a result of “local weather disaster.” (I’m utilizing “local weather disaster” as a way to be extra scientifically exact, like The Guardian said they’d do with their articles. That was pure sarcasm).

Unprecedented flooding is shortly turning into a brand new regular.

Regardless of that, Republicans are tripling down on fossil fuels w/no plan to transition off them, or make the crucial infra investments we have to prep for the local weather disaster.

Every day of inaction places extra of us in peril.

— Alexandria Ocasio-Cortez (@AOC) July eight, 2019

Her reference to “unprecedented flooding” was fueled off of headlines detailing flooding within the Washington, D.C. space (the place I stay and forecast the climate). Certainly, she was proper within the sense that the flooding on Monday was spectacular, however the traditional scaremongering tactic of blaming fossil gas emissions on the occasion is simply plain pseudoscience and superstition, and doesn’t root itself in actuality.
In response to the Nationwide Climate Service workplace in Sterling, Virginia, official observations from Reagan Nationwide Airport point out that three.44 inches of rain fell Monday, July eight. This rainfall was not solely a file for the date (previous file was 2.16 inches from 1958), it was a little bit over 92% of D.C.’s common July month-to-month whole rainfall of three.73 inches!

WHEN IT RAINS, IT POURS! At this time’s rainfall whole @Reagan_Airport was three.44 inches, which not solely broke the previous every day file of two.16 inches (1958) by 1.28 inches, it was additionally a little bit over 92% of the common July month-to-month rainfall in D.C., which is three.73 inches Unbelievable!

— Chris Martz Climate 🇺🇸 (@ChrisMartzWX) July eight, 2019

All of this was brought on by a posh of slow-moving thunderstorms that rolled by means of the realm Sunday night and Monday morning (I can verify since I stay within the space). This was not brought on by magic CO₂ fairy mud within the ambiance.
Flash floods from thunderstorms usually happen when thunderstorm cells are slow-moving, or when completely different thunderstorm cells transfer over the identical space again and again.¹ The severity of a flash flood - when it comes to how briskly it develops and the way excessive the water ranges get - depend on elements just like the length of the rain, the rainfall depth and terminal velocity of raindrops, and/or soil moisture.¹ Sunday night and Monday morning, the storms had been slow-moving and rainfall depth was excessive. As well as, final yr (2018) was the wettest yr on file in Washington, D.C. with 66.28 inches of precipitation falling on town.² 2019 has additionally been a reasonably moist yr, with 27.12 inches of rain falling to date.² Thus, soil moisture stays excessive, and in consequence, extra water from rain or runoff can’t seep into the bottom, creating a better threat for flash floods.

Determine 1. Whole precipitation January – December in Washington, D.C. 1872 – 2018,

So, with that mentioned, does her declare about “unprecedented flooding” in D.C. maintain any water? Spoiler alert, it doesn’t!
Earlier than I present the statistics, her assertion doesn’t even make any sense. If every new flood is “unprecedented,” then that’s climatologically not “regular.” So how can it turn out to be regular? Possibly she implies that flash/inland/river flooding is the brand new regular? In that case, that’s nonetheless unsuitable. Two strikes in a row AOC, the third is OUT.
Washington, D.C. has a protracted historical past of flash flood occasions, river flooding, and heavy rainfall occasions, most of which aren’t even noteworthy as a result of they occur so usually, particularly the throughout spring and summer season as daytime heating and excessive dew factors act as “set off mechanisms” to provoke thunderstorm growth within the afternoon hours.

Heavy Rainfall Occasions

Meteorologist Kevin Williams of Rochester, New York made word that of the highest ten heaviest 24-hour rainfalls in D.C., solely two of the ten have occurred this century. Of the eight heaviest 24-hour rainfalls to be formally recorded in D.C. throughout the 20th century, seven of them occurred previous to 1975, and 5 occurred previous to 1970.

Listed below are the 10 heaviest 24 hour rainstorms on file in D.C. Fascinating that eight of the ten occurred throughout the earlier century.

— Kevin Williams (@wxbywilliams) July eight, 2019

So, clearly, heavy rainfall occasions in D.C. should not a brand new factor. What about precise floods?

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

David Birch, a buddy of mine and a widely known photo voltaic researcher within the local weather group despatched me this hyperlink Monday afternoon, which has a listing and outline of a few of Washington, D.C.’s largest flood occasions in reminiscence.
So, let’s break it down.
1. The “Nice Recent Flood” of Might 1771 was devastating to the Virginia colony and Washington, D.C. space.³ ⁴ The Virginia Gazette reported, “…From the mountains, to the Falls, the low Grounds have been swept of just about each Factor priceless; and the Soil is a lot injured that it’s thought to not be of Half its former Worth, and an amazing Half is solely ruined…³

2. On June 2, 1889 the Potomac River crested 12.5 toes above flood stage. Many streets, together with Pennsylvania Avenue had been flooded (Determine 2).⁴

Determine 2. Pennsylvania Avenue flooded on June 2, 1889 in Washington, D.C. Photograph credit score: Library of Congress.

three. The Flood of March 17-19, 1936 was certainly one of Northern Virginia’s, Maryland’s, and D.C.’s worst pure disasters in historical past.⁵ This flood is commonly famous because the “Document Flood of 1936,” “Nice Potomac Flood,” or the “St. Patrick’s Day Flood of 1936.”⁵
March of 1936 was fairly heat in Washington, D.C., averaging three.5°F above regular for the month, regardless of frequent drastic temperature swings from the 40s to the 70s and again.²
Most of Japanese West Virginia, Northern Virginia, and Maryland had obtained their complete March month-to-month common rainfall by mid-month.⁵ Whereas a lot of the rainfall occasions had been comparatively small, the excessive frequency of them that March allowed stream water ranges to extend.
The storm that induced the key flooding was on St. Patrick’s day in 1936, when a deepening low within the Carolinas pushed southeast winds and moisture into the area inflicting intense rainfall.⁵ Whereas most areas in and across the D.C. space noticed lower than two inches of rain, areas to the west, just like the Blue Ridge Mountains obtained nicely over 4 inches of rain in that two day interval.⁵ The record beneath is from the Nationwide Climate Service. You possibly can see simply how spectacular these two-day totals had been (Determine four).

Determine three. Two-day rainfall totals from the March 1936 storm.

four. The “Document Flood of 1942” unfolded over an eight-day interval; October 11-18.⁴ Throughout this occasion, D.C. picked up over six inches of rain, and floodwaters reached the steps of the Jefferson Memorial (Determine four).⁴

Determine four. Jefferson Memorial steps flooded in October 1942 flood.

5. The Flash Flood of August 11, 2001 was one for the books (Determine 5). What’s odd about this flash flood occasion was that it occurred in a slender band stretching from Warrenton, Virginia to Washington, D.C.⁴ Some storm experiences from D.C. and close by communities famous that upwards of seven inches of rain fell that day.⁴ Reagan Nationwide Airport solely obtained zero.92 inch of rain throughout the occasion.²

Determine 5. Flash flood of August 11, 2001.

Climate vs. Local weather

Individuals like Consultant Cortez appear to have a really tough time greedy the elemental variations between climate and local weather, which is the truth that climate relies on short-term atmospheric situations and local weather relies long-term tendencies.

Any particular person climate occasion - no matter how excessive it’s and whether or not or not it’s unprecedented - can merely not be used as proof for OR in opposition to adjustments in Earth’s local weather system. The ambiance - as we all know - may be very chaotic in nature and any kind of maximum climate occasion is sure to occur at a while or one other however world common temperature change.

When you have a look at the tendencies in world decrease tropospheric temperature since 1979, you’ll see that they’ve undoubtedly gone up, but we’ve all the time had floods (hear that AOC?), we’ve all the time had hurricanes, we’ve all the time had tornadoes, wildfires, dust-devils, droughts, warmth waves, chilly waves, thunderstorms, blizzards, and monsoon seasons. Whereas the frequency and/or depth in such occasions might or might not alter in both route because of adjustments within the local weather, as a result of they’ve all the time occurred, as a result of they’re susceptible to occur, and since there’s a scarcity of enough world long-term information, this can be very tough and conceited to pinpoint one climate occasion as proof of a “local weather disaster.”

Flash flood occasions just like the one which occurred on Monday in D.C. are related to thunderstorms, that are thought of “extreme convective storms.” In response to the Nationwide Academy of Sciences (NAS), there may be little or no proof to hyperlink thunderstorms to man-made local weather change, world warming, the local weather disaster, or ecological breakdown - whichever approach you’d prefer to name it.⁶

Determine 6. Local weather change and excessive climate – Nationwide Academy of Sciences (NAS).

If I had been to sum up this nonsense in a single sentence I’d say, “There’s one thing rotten in D.C., and it isn’t these rainfall totals, it’s clueless politicians.”


[1] “Thunderstorm Hazards – Flash Floods” Nationwide Climate Service. Accessed July 9, 2019.
[2] xmACIS2. Accessed July 9, 2019.
[3] Yeck, Joanne. “The Nice Recent of 1771.” Slate River Ramblings… March 13, 2017. Accessed July 9, 2019.
[4] Ambrose, Kevin. “Floods – Washington Space Floods.” Accessed July 9, 2019.
[5] “1936 Flood Retrospective.” Nationwide Climate Service. Accessed July 9, 2019.
[6] “Local weather Change and Excessive Climate.” Penn State Division of Meteorology and Atmospheric Science. Accessed July 9, 2019.

Posted by Chris Martz Climate at
9:06 PM

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