Thursday 15 August 2013

Climate change news

Mangled Jet Stream to Collide with Tropical System over Southeastern US for Major Rain Event?


14 August, 2013



(Image source: NOAA)

In the southeast this year, rain follows rain follows rain. Now a tropical system may be preparing to add its own moisture to the already very wet mix.
The river of upper level airflow called the Jet Stream begins an almost due south movement at the Arctic Circle near the Northwest Territory and Canadian Arctic Archipelago. The atmospheric river dives down over Central Canada and into the Great Lakes region. Continuing ever southward, it finally encounters a wall of warmer air setting up near the south Tennessee border where it speeds up and turns eastward, joining another Jet Stream flow coming in over the Rockies.
Riding along these convergent Arctic and Pacific Jet Stream flows are a number of wet and stormy impulses. Because this deep north to south dip has been in place over the Eastern and Central US for much of the summer, storm after storm has continued to impact a large region from Missouri to New Jersey southward through the Carolinas and then again southwestward along through Georgia and the Gulf Coast states. This persistent stormy pattern, a result of a slow, wavy, stuck Jet Stream, which is, in turn, caused by sea ice and snowfall loss in the Arctic, has pushed rainfall totals 20 inches or more above the yearly normal in some locations. It has delivered extraordinarily moist storms that dump inches of rainfall in just a few hours. And it resulted in some regions of Missouri receiving four months worth of rainfall in just one week.
In the above water vapor image, provided by NOAA, you can see the storms riding along the south frontal boundary of this Jet Stream trough through the Dakotas, Montana, Nebraska and Colorado then down into Texas, turning eastward through the Gulf Coast States and then surging north along the US East Coast.
Yesterday, this pattern delivered a powerful storm complex to Pennsylvania and New Jersey — flooding roads, knocking out power and dumping as much as six inches of rain. Now, the Jet Stream has driven further south, pushing the frontal boundary over the Gulf Coast and US Southeast.

Mangled Jet Stream trough over eastern US.
But as if the convergent flows of the Jet Stream delivering very powerful storms, as if the stuck weather pattern keeping this storm-delivering trough over the Eastern US for months, and as if the human-added atmospheric heat amping up the hydrological cycle and spurring more intense rain events were all not enough, we now have a large, moist tropical weather system moving in and threatening to become entangled in an already very wet pattern.
As of this morning, the National Hurricane Center had issued an advisory for a tropical system in the western Caribbean predicting a 60% likelihood of tropical storm formation over the next several days. The system is a large, sprawling and disorganized mass of thunderstorms and moisture moving toward the north-west at 10 to 15 mph. A circulation appears to be trying to form in a region near the densest thunderstorms. The system is predicted to move toward the northwest until it is eventually captured by the frontal boundary at the leading edge of our deeply sagging Jet Stream. Should this mix-up occur, a tropical weather system and potential tropical cyclone will have again combined with an Arctic originating air-mass over the Eastern US, setting the stage for a rather intense and widespread rainfall event.
If there are some reading this analysis and thinking that it rhymes somewhat with set up for Superstorm Sandy, they wouldn’t be entirely off the mark. Until recently, it was less likely that tropical systems would combine with polar originating air masses over the US. The troughs originated and faded rapidly, only infrequently coming into dramatic collisions. But now, with the Jet Stream increasingly settling into a stuck pattern (spurred by human caused warming and sea ice loss) and seeming to favor trough development over the continental US and not over the ocean, such collisions are far more likely.
With the current system, unlike Sandy, rain appears to be the primary concern for now — not storm hybridization, expansion, and superstorm development. These are not on the radar. But we are still very early in storm development and we don’t yet know how powerful the slowly organizing tropical system will become. What we have right now is a large, and potentially strengthening package of tropical moisture setting its sights on an already soaked US southeast.

Very Moist Developing Cyclone Setting Sights on Southeastern US.
So the risks at the moment are for a potential major flooding event on the five to seven day horizon as the tropical system continues to track northwestward until it is pulled into the stormy flow of the Jet Stream trough. At that point, it is predicted to dump a heavy load of moisture and rain over the US southeast.
Current predictions from NOAA reflect uncertainty in storm development and track and, at the moment, call for 3-5 inches of rainfall from the Gulf Coast States through Georgia and the Carolinas over the next 5-7 days. Local amounts, however, could be much higher, on the order of 8 inches or more. Such an event would intensify an already severe flood problem over this large area, likely resulting in major and widespread flooding.

NOAA rainfall predictions over the next week.
(Image source: NOAA)
Any significant wind field of 40 mph or more would also likely result in a mass of fallen trees. The ground in this region is saturated with moisture, making it harder for tree root systems to grip the soil. So it takes much less wind to blow them down. Widespread power outages due to trees falling over power lines is, therefore, also a potential threat for this system.
Given the current position of the Jet Stream and uncertainty over potential storm strength and track, this situation could rapidly develop into a dangerous event for the southeastern US or we could end up with a storm system making landfall closer to Texas and Mexico. So we’ll be closely watching storm strength and path over the coming week.
UPDATE:
Tropical weather system 92 L is starting to exhibit some cyclonic turning:

92 L Shows Cyclonic Turning
Links:

Why Do I Call it a Mangled Jet Stream? Learn More Here.


A Song of Flood and Fire: One Million Square Kilometers of Burning Siberia Doused by Immense Deluge




14 August, 2013

About a week and a half ago, I reported on a great burning event in which a massive region of Russian Siberia erupted in hundreds of wildfires blanketing it in a sea of smoke clearly visible in the NASA Aqua Satellite record. Today, reports from Interfax/Radio Russia describe an immense flood emergency in which over 1 million square kilometers of Russia’s Yakutia region have been submerged by a catastrophic rain event.
From the Interfax report:
It is a unique situation in the sense that it has spread over more than 2,000 kilometers if one looks from west to east, while its depth or width is more than 500 kilometers,” Vladimir Stepanov, head of the National Crisis Management Center of the Emergency Ministry, told a news conference in Moscow.
According to the report, hundreds of villages in this, thankfully, sparsely populated region have been inundated by water putting hundreds of thousands of people in amongst a swirling flood. According to reports from Russian government, the region is now the site of a massive and major rescue operation. As of August 11, the operation composed an army of 20,000 personnel — a force that is likely to have greatly swelled as this major climate disaster expanded through today.

A Song of Flood and Fire
As of late July, heavy rainfall had emerged in a dense band along eastern Russia and bordering north China. This band of dense and heavy moisture rose north over an ocean heat dome that was setting off very dangerous high temperatures over the region of Southeast China even as it was baking a large region of ocean, heating a vast expanse of the surface waters to above 30 degrees Celsius. The added moisture and heat content provided fuel for low pressure systems skirting the high.
By early August, major flooding had begun to occur in this eastern region as very heavy storms sprang up over this large area.
We can see the development of this massive storm system starting on August 4th in the image below:
Russia August 4 — Heavy Rains to the East, Massive Fires to the West
(Image source: NASA/Lance-Modis)
In the above image, we are looking down on the Earth from a shot taken above the North Pole. The region we are looking at is Siberian Russia and Yakutia which dominates the central section of the image. Toward the lower left are the Laptev and East Siberian sections of the Arctic Ocean. Toward the central and upper left is Eastern Russia (Kamchatka), Mongolia, and extreme north China. In the upper right corner is central Asia.
Note the very dense region of clouds and rain pulsing up from the Pacific Ocean and overlaying Kamchatka and southern Yakutia. The storm at this point is vast and its cloud coverage immense. But it is just getting started.
Russia August 7 — Low Pressure Emerges From Central Asia
(Image source: NASA/Lance-Modis)

By August 7, the storms had sagged toward the south, drifting slowly eastward along the monsoonal flow. Occasional pulses of moisture rose northward from the Pacific to refresh and intensify this storm and cloud flux. This action brought the Pacific and monsoonal storms in direct contact with a hungry low pressure system rising up out of Central Asia and moving from the southwest toward the northeast. By August 7 we can begin to see this storm system entraining the massive volume of moisture associated with the Pacific storm pulse and monsoonal flows.
The storm was emerging over a region of Yakutia that had experienced a massive and terrifying explosion of very energetic wildfires. The air was heavily laden with particles of dense smoke from a great burning that had intensified since late July. There the moisture erupted into a powerful deluge that by August 11th had broken flood records set as far back as 1896. By that time, more than 20,000 personnel had been mobilized to help deal with the floods as hundreds of homes and scores of roadways were inundated.
Russia August 11 — Deluge Fully Formed Over Yakutia
(Image source: NASA/Lance-Modis)
As of August 11, we see a massive and fully formed storm complex directly over Yakutia. The storm has now fully entrained the dense smoke cover belched out by the hundreds of fires, some of which were still burning throughout the region. It was also still drawing in moisture from the Pacific storms and monsoonal flow over south Russia, Mongolia and northern China. A second arm of the storm stretched northward linking the storm with the Arctic. With a strong south and north linkage, the storm had accessed energy to maintain strength and intensity for an extended period.
The large storm system continued to churn through Yakutia and by today, August 14th, a massive region covering 1 million square kilometers was inundated by floodwater. What we see in the satellite shot for today are not one, not two, not three, but four rivers of moisture linking the major storm system that has inundated Yakutia
Russia August 14 — Rivers of Moisture Collide
(Image source: NASA/Lance-Modis)
The first river of moisture is a continuation of the Pacific flow rising up along the southeast Russian coast, the second is the monsoonal flow moving from west to east to combine with this Pacific flow. A third flow feeds into the storm from Europe as it rides along parallel and to the north of the more southerly monsoonal flow. A final river of moisture rides up the from the storm, linking it to the Arctic and likely sharing energy and instability with that cold and dynamic region.
With a second low developing to the west of the first and moving along in its shadow and with moisture continuing to feed into these storm systems from the monsoonal flow to the south, it appears that rainy conditions will persist for the already inundated Yakutia region over the next few days at least. And if this pattern continues as predicted, it may well come to rival the great Pakistani floods of 2010.
Fires Still Burn Near the Flooded Lands
One, rather odd, feature of this major flood and fire event is that large areas of wildfires are shown to still be burning throughout Russia. Though the onrushing deluge clearly put out some of the major fires burning in north and central Yakutia, still other major fire complexes continue to burn — some of which remain very near to flooded regions.
In the below MODIS shot a major fire complex is still visible in a region of Russia to the west and south of areas most heavily affected by flooding:
Fires Burn in One Part of Russia as Another Part Floods.
(Image source: NASA/Lance-Modis)
These fires are burning directly in the shadow of the second storm system with their smoke trails feeding into the storm along its southerly inflow.
Conditions in Context
Earlier this year, drought and heatwaves blanketed Siberia and Yakutia. But late July, this region had begun to erupt in a series of extraordinary wildfires that blanketed almost all of northern and eastern Russia in very dense smoke. By early August what is perhaps the worst rainstorm in the history of this area of Russia had begun to form. As of the writing of this article, on August 14, major storms and flooding continued with no immediate end in sight.
Major heatwaves and droughts in extreme northerly regions of Siberia are an anomalous event linked to human caused climate change. Rapid sea ice and snow cover retreat combine with temperatures that are warming at a rate of .5 degrees C each decade over this region to increase the likelihood of such extreme events. Methane and organic carbon stores in the thawing tundra steadily release under this heat forcing and likely provide an amplifying feedback to summer heating events by locally providing more greenhouse gas emission and also providing another fuel store that is available to wildfires. In some of these wildfires, there are reports coming in that fires burn as far as 3 feet into the ground, taking out root systems and stumps along with the trees that burn above ground. Reports of burning ground have also been trickling in (Hat tip to Colorado Bob)
Such burn events are anomalous enough. But for a flood that covers a 1 million square kilometer area to immediately follow in the wake of such amazingly large and widespread fires is anything but normal. Atmospheric patterns that link major weather systems and increase their intensity can be attributed to the formation of powerful heat dome high pressure systems along with weakened and meandering Jet Stream waves. Rising atmospheric heat caused by human warming adds to the density and strength of heat domes (identified as becoming more intense by meteorologist Stu Ostro). Meanwhile erosion of the Jet Stream caused by reduced snow and sea ice cover (identified by Dr. Jennifer Francis) is implicated in a host of problems including more intense and persistent droughts and storm events along with the increased likelihood that weather systems will link up as north to south weather patterns deepen, back up, slow down, and elongate.
A massive ocean heat dome to the south over the Pacific adjacent to China and sea ice and snow cover remaining near record lows must be taken into account when looking at features that likely contributed to the extreme swings from drought, heatwave and fire to massive deluge and flood in Russia.
One last point to consider as a likely contributor is the fact that for each degree (Celsius) of human-caused temperature change, the hydrological cycle amplifies by about 8 percent. This means that rates of evaporation and rainfall are now about 6 percent more intense than they would be in the world of the 1880s. When combined with powerful new weather features like a mangled Jet Stream and immense heat dome high pressure systems, an amped up hydrological cycle further inflates an already extreme environmental condition.
Links and Credits:
Hat Tip to Commenter Steve


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