NOAA’s composite forecast for the jet stream for June 1-7 shows that it has flattened out and is situated unusually far to the north. Forecast courtesy of NOAA.
The weather pattern — we’ve named it ‘Government’ because it moves so slowly — that has plagued the plains, midwest , and southeast for several weeks with tornadoes, hail, flooding rain, and lightning, has reached a crescendo with historic flooding in Texas and Oklahoma.
Following more potential flooding today in Texas, Arkansas, Louisiana, and southern Missouri, Government’s effects will ease off later this week, followed by a period of respite.
Forecasts indicate that this might be just a recess, rather than a permanent adjournment.
As of Sunday, Oklahoma City had over 18 inches of rain in May, easily surpassing the record for May and the less than 15 inches that was the previous single-month record set in June of 1989. Observations go back to 1890.
Getting Through Memorial Day
The surface analysis for 9 p.m. CDT on Friday, May 22, shows a southeast flow from the Gulf of Mexico which provided the moisture for flooding rains in Texas and Oklahoma. Analysis courtesy of NOAA.
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Weather Pattern Government amended its agenda slightly over the weekend, producing flash floods as copious moisture from the Gulf of Mexico at low- and mid- levels of the atmosphere conspired with the lift associated with a curl in the jet stream.
With the rains moving east, Texas and Oklahoma could see some sunshine today. This would increase the risk of afternoon severe thunderstorms and the possibility of tornadoes.
What Is A Flash Flood And How Does It Happen?
Under normal weather conditions, water is well-behaved. The hydrologic cycle begins with evaporation from surfaces of land and water. The atmosphere can hold only a limited amount of water vapor, and when saturated air is lifted, the water vapor condenses and returns to the surface of the earth as precipitation. Most of the precipitation eventually drains back into the sea.
Natural and manmade drainage systems, rivers and storm drains, routinely hold all the water that falls.
If the rain is very heavy compared to the average, the drainage systems can be overwhelmed, and the water can end up in places where it is unwelcome, such as city streets and people’s houses.
The ground can absorb some precipitation, but when rain falls over a period of weeks, the ground becomes saturated and any additional rain runs off immediately.
That is what has happened in this flood event. In many parts of Texas and Oklahoma, the rains accumulated to levels never seen in May, and in some cases, never seen in any month.
The Danger Of Flash Floods
A car is easily swept away by water only a couple of feet deep. Photo courtesy of NOAA.
When water overflows a riverbank or overwhelms a storm drain, the water level can rise rapidly, often inundating roadways. About half of all flooding fatalities take place in motor vehicles. A car can be swept away by water only a couple of feet deep, because the vehicle is buoyant until it fills with water, which can take several minutes. Drivers routinely assume that gravity will keep the car anchored to the road, but that is not the case.
The National Weather Service has the slogan “Turn around, don’t drown,” which refers to any occasion on which the depth of the water is unknown.
Where houses have been built in low-lying areas, water can rise to the rooftops in a matter of minutes. In the current flood event, many residents were saved by helicopter from the roofs of their houses.
Government’s Warm Side
What goes up must come down, and this is true of undulations in the jet stream. Weather Pattern Government is characterized by a deep trough (dip) in the western United States. The opposite phase of this wave is a ridge (bulge) in the east. Under this ridge, a heat wave is likely to occur. It is a modest one by midsummer standards, since the summer maximum of temperature is over a month away, but temperatures will reach 90 degrees in Washington on Tuesday, and continue to run ten to fifteen degrees above normal in the southeast and mid-Atlantic through the week.
The Jet Stream Pattern Flattens Out
By midweek, the jet stream trough will have weakened, the rains decreased, and generally things will have quieted down.
The flattening of the jet stream means less severe weather, though afternoon heating will still produce seasonal thunderstorms and the possibility of a tornado. The forecast position is farther north than usual, so to the south, the warm air will remain in place.
Is It Climate Change?
No single event will prove or disprove that the climate is changing. But an accumulation of anecdotal evidence leaves less doubt all the time.
This flooding in Texas occurs where there has been a drought for several years. One of the hallmarks of global warming/climate change appears to be persistent weather — what you see is what you get for a long time. Weather Patterns like Government — unchanging for weeks, months, or years — have been increasingly common in the 21st century.
A slow, steady change of climate is relatively easy to deal with. Lengthy bouts of extreme weather like the flooding in the plains this week: not so easy.
© Copyright 2015 Jon Plotkin, All rights Reserved. Written For: Decoded Science
Chris used an important word — nonlinearly. It’s not clear how the changes will take place. I don’t know what E.A,’s problem is. If the change is linear, say the temperature rises slowly by 5 degrees everywhere in the next century, everybody can just move poleward a couple hundred miles.
Kevin, I don’t see how you can say the pattern in May wasn’t unusual. Oklahoma City had its rainiest month — not just its rainiest May — ever. I’d say that’s unusual. And who says a scientist can’t use common phrases like ‘appears to be?’ I stand on my First Amendment rights.
Quote: “A slow, steady change of climate is relatively easy to deal with.” Really? The whole problem with global warming is that it will seriously disrupt weather patterns society has come to depend on over centuries, and will cause rising sea levels and much worse storm surges, etc.
Weather pattern named Government, I love it! More fuel for the Jade Helm conspiracy theorists in Texas.
A 2015 study published in the science journal Nature, reported: 18% of the moderate daily precipitation extremes over land are attributable to the observed temperature increase since pre-industrial times, which in turn primarily results from human influence. For 2 °C of warming the fraction of precipitation extremes attributable to human influence rises to about 40%. Likewise, today about 75% of the moderate daily hot extremes over land are attributable to warming. It is the most rare and extreme events for which the largest fraction is anthropogenic, and that contribution increases nonlinearly with further warming. http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2617.html
While our world warms, climate patterns shift, and weather events become more extreme, the republicans in the U.S. Congress reject science and are willing to put our future generations at risk for the sake of fossil fuel sponsors or some political agenda.
Join the efforts to confront and replace them. We need to elect pragmatic law makers willing to face reality and deal with it in our long-term best interests. For our part, apathy/inaction effectively advocates for more of the same irresponsible behaviors. We can’t afford it.
ExhaustingHabitability(dot)org
Jon: Your analysis and commentary was informative and entertaining… right up to the last section. What you are leaving out is that the weather pattern we are seeing in Texas right now is not that unusual — we just haven’t seen it for a while. When I first moved to Texas in the early 1990’s, May rains and floods were common. The past decade has been a cyclical shift toward warmer, drier weather. This year has broken the cycle and returned to the wetter, hopefully slightly cooler summers.
As a scientist you should know better than to use phrases like “an accumulation of anecdotal evidence” and “appears to be.” This shows that you are analyzing the evidence as you want it to be, not as it is.
sure, this cycle has been seen before. the fact that cyclical weather occurs is not the issue. it’s the intensity of the cycle that he’s talking about: the fact that the amount of rainfall is so much more than what you saw in the 1990’s.
the other point is that perhaps one ought not wait for something to be ‘proven’ to begin taking action: if a pattern develops, the ultimate outcome of which may be unacceptable to us, it might be better to begin some action to help interrupt that pattern, rather than to wait for that pattern to “prove itself” by waiting for it to come to completion.
Standard denial rhetoric. Pretend nothing different is really happening, even though the Earth is accumulating 250 trillion joules per second of heat energy, most of which goes into the oceans. This is energy the climate didn’t have before, and it’s caused by man-made CO2 buildup.
And of course, you made no mention of the vast amounts of ice being lost from glaciers and the poles. Will you claim that those are just random changes that happen now and then? Little ol’ Man can’t have nuthin’ to do with it, eh?