Sunday, December 27, 2015

Let's Hope This Is Nation's Worst Storm Of The Winter

Terrible destruction in Garland, Texas after
last night's tornado. Image from NBC DFW. 
As noted last night, fatal tornadoes struck some Dallas suburbs last night.

Latest reports are 11 people died in the Texas tornadoes. 

That brings to at least 25 the number of people killed by tornadoes and storminess in the Uniteds States since Dec. 23. I worry we will lose more today.

We awoke this Sunday morning to enormous parts of the country suffering from very dangerous weather.

For one thing, the tornado threat isn't over, and we've had quite enough fatal, dangerous tornadoes already in the past week, thank you very much. Today's severe storm and tornado threat is highest in eastern Texas, western Louisiana and southern Arkansas.

An enormous flood warning extends from eastern Oklahoma, through central Missouri, Illinois and into Indiana as torrential rains continue to pour down.  An even bigger area of flood watches surrounds this huge, roughly 700 mile long flood warning zone.

Tornado destruction near Dallas, from WFAA. 
Meanwhile, a blizzard is hammering New Mexico and northwestern Texas. Winds are gusting past 60 mph, visibility is zero and so is the wind chill. Drifts are approaching ten feet deep in some spots.

In Clovis, New Mexico, for instance, they were telling everyone to stay indoors or else. And for good reason.

Visibility was about zero in the blizzard, it was only 18 degrees, and the wind was gusting to 64 mph. Snow drifts were already eight feet high.

An ice storm is looming in central Oklahoma. Winter storm warnings and watches cover another enormous area from Kansas to the Upper Peninsula of Michigan. Other winter weather advisories are in effect today for parts of northern New England.


Bad, dangerous weather often strikes the United States in the winter. But this storm is covering a wider area with a wider assortment of hazards than is usual. This storm is a real humdinger.

A lot of people are asking: What is causing this havoc?

When you scratch the surface, the answer is easy: There's a big, powerful storm system in the middle of the country.  It's pulling lots of moisture from the Gulf of Mexico.  There's also a lot of unusual warmth to the east of the storm, which is helping fuel it. The storm is causing a lot of lift in the atmosphere and stirring up a lot of wind.

So you have a big storm.

Drill down on the investigation and it gets more and more complicated.  The extreme nature of the storm, including the unprecedented Christmas week heat in the eastern United States, makes you wonder if other factors are involved.

The short answer is, Yep.

El Nino is probably playing a role. That infamous polar vortex is also positioned in such a way as to encourage weird weather in the U.S. And maybe, just maybe, global warming is playing a bit part in this.

I liken the investigation into the causes of this stormy mess to any other investigation.  Lots of reasons come to the surface the more you dig.

For instance, imagine you're investigating why a house burned down.  Perhaps the direct cause is simple to find: There was a short in the wire on a string of lights on a Christmas tree, and that sparked the blaze.

Mystery solved, right?

Then you start thinking. Why was the wire on the tree frayed? Did somebody damage it, or was it a manufacturing flaw? Were the homeowners blissfully unaware of the damaged wire or did they choose to ignore it and hope for the best.

Why did the fire spread so quickly? Were there smoke alarms to give early alerts? Sprinklers? Was the construction of the house conducive to allowing the fire to spread so fast?

It can go on and on.

So it is with extreme weather events like the one plaguing the United States now.

Yes, it's caused by a strong storm system. But why is it so strong? And why is it causing such a wide variety of scary weather?

Look more carefully and El Nino becomes a prime suspect. It's the strongest on record and it's mucking up weather patterns world wide.

El Nino tends to strengthen the jet stream across the southern United States. That helps make storms more likely from California to Florida.

These El Nino storms can be stronger than your typical winter storms, and this one could be a prime example

Another suspect: Remember the "Polar Vortex"?

Despite the hype, it's a real thing, and it's a cold circulation or pool in the far northern hemisphere that's always there, and is strongest and most noticeable in the winter.

When the jet stream up north in Canada is extremely wavy, the polar vortex can get closer to the United States, or a piece of it can break off and plunge to or near to the Canadian border. That's when we get our nasty subzero cold waves.

This year, a good strong jet stream is keeping the polar vortex wound up tight and confined way up at or near the North Pole. It's nowhere near getting close enough to plunge a huge bunch of cold air into the United States.

Some typical cold air is in the western United States - after all it IS winter -- but it's not the purest, coldest Arctic air that comes with the Polar Vortex.

Digging deeper into our investigation on this storm, is global warming a suspect? Maybe, but it wasn't the ringleader in this mass of tornadoes, heat, floods, storms and blizzards.

The extreme weather in the United States very likely would have happened with or without global warming. And it's very hard to tease out one weather event like this one and point an accusing finger at global warming.

That's not to mean climate change isn't culpable. It's very plausible that global warming made the Christmas heat wave just a little hotter than it otherwise would have been, which enabled more record highs to be broken.

And, global warming can make precipitation events more extreme. After all, warmer air holds more moisture than colder air.  Maybe because of climate change, there might have been more moisture available to this storm to make the heavy rains even more torrential than they otherwise would have been.

Again, though, it's very hard for even people well above my pay grade to determine how much, if any, global warming had in making this week's weather so extreme. My suspicion is it helped a little.

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