Extreme Winter Weather Event Artic(hoke) Will Last — And Last — And Last

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The low between Russia and Alaska has deepened with the absorption of Typhoon Nuri. Analysis courtesy of NOAA

The low between Russia and Alaska has deepened with the absorption of Typhoon Nuri. Analysis courtesy of NOAA

Decoded Science has named this Extreme Winter Weather Event: Artichoke. Though Artichoke may bring record cold temperatures and early-season snow, it will likely be remembered more for its duration and extent.

Super-Typhoon Nuri Reinforced And Amplified The Weather Pattern

After passing Japan, Super-Typhoon Nuri transitioned into one of the most powerful extra-tropical storms on record, with a central pressure of 924 mb. Nuri has been absorbed by the persistent low pressure feature over western Alaska, with an accompanying ridge (high pressure) over the western US and adjacent waters.

Conforming to the predominant wavelength, another dip in the jet stream over the eastern US has become more pronounced.

The result of all this is that a lobe of the polar vortex, which normally resides over Hudson Bay, will camp in south-central Canada, with its influence pervading the eastern US from the Rockies to the Atlantic coast and deep into the south.

As large features in the pressure field become amplified like this, they tend to move very little. The high pressure becomes an omega block and the dips in the jet stream become closed lows. The result will be a long period of blustery weather in about the same places that suffered under last winter’s brutal conditions.

Freezing Temperatures From Artichoke’s Frigid Fingers

As this freezing cold front passes, temperatures will tumble spectacularly:

  • Denver: The high temperature was 73 yesterday and will be  28 tomorrow — a change of 48 degrees in 48 hours.
  • Billings, Montana: The high temperature on Saturday was 69 degrees. Tomorrow’s high will be 13, a change of 56 degrees in three days. Today will be the first of six consecutive days with the high temperature more than 20 degrees below normal.

Here are some indications of the long-lasting effects of artichoke distilled from the forecasts of The National Weather Service, Accuweather, and The Weather Channel:

  • Boston: Eleven consecutive days with the high temperatures five or more degrees below normal.
  • Atlanta: Ten consecutive days with the high temperature ten or more degrees below normal.
  • Minneapolis: Thirteen consecutive days with the high temperature ten or more degrees below normal, including seven in a row at least 17 degrees below normal.
  • Chicago: Twelve consecutive days with the high temperature 10 or more degrees below normal.
  • New York: Eleven consecutive days with the high temperature seven or more degrees below normal.
  • Dallas: Fourteen consecutive days with the high temperature seven or more degrees below normal, including seven in a row at least 16 degrees below normal.
  • Omaha: Fourteen consecutive days with the high temperature nine or more degrees below normal.

A Band Of Heavy Snow Herald’s Artichoke’s Arrival

As the cold air moves south through the Plains and Midwest, a small wave of low pressure will ripple eastward along the boundary between warm and cold air. Up to a foot of snow could fall in a band through central Minnesota and northern Wisconsin, including metropolitan Minneapolis.

Later in the life of Artichoke, when the cold air is well established over the eastern states, the jet stream might acquire the familiar shape that is the precursor to a nor’easter. Though it will probably be too warm to snow in the mid-Atlantic, New England could get plowable amounts of snow.

The Weather Channel’s Winter Storm Names

Tropical cyclones have been given names for many decades. In November of 2012, The Weather Channel began naming winter storms. This practice has been ridiculed as a publicity stunt by Accuweather, and the names have been shunned by the National Weather Service.

Decoded Science applauds The Weather Channel’s effort to make identification of extreme weather situations simpler, regardless of the commercial underpinnings of the idea. However, the initial rollout was clumsy and often incomprehensible.

Tropical systems are named according to strict objective criteria, primarily wind speed. The Weather Channel’s criteria for winter storms were vague, and in the end the decision was made by a show of hands among the senior staff.

During the 2013-14 winter, Decoded Science adopted The Weather Channel’s designations, with a few exceptions, for the sake of simplicity of communication.

This year, The Weather Channel has adopted a more stringent set of criteria; but they have passed the buck. A storm will now be named when the National Weather Service has issued winter storm warnings over an area which either measures more than 400,000 square kilometers (about the size of Montana), or contains more than two million people. However, the ‘senior staff’ can still overrule the objective criteria.

The National Weather Service has now issued winter storm warnings in a large swath of the northern plains and Upper Midwest. The extent of the warnings exceeds both of the Weather Channel’s criteria, and The Weather Channel has duly named Winter Storm Astro.

What’s With The Name, Artichoke? What’s Wrong With Astro?

The practice of naming storms, tropical or extra-tropical, after people poses the risk of stigmatizing thousands who, through no fault of their own, will be forever associated with a particular storm. Decoded Science will, therefore, use other categories than real names of people for purposes of referring to extreme weather events.

We have named extreme events after animals in the summer and fall, and this winter we will name them after vegetables. It’s hard to stigmatize a vegetable, though President George H.W. Bush tried to do so by declaring: I do not like broccoli.

How Long Will Artichoke Last?

One of the more reliable forecasting models shows that Artichoke will still cover the eastern United States a week from today. Forecast courtesy of NOAA

One of the more reliable forecasting models shows that Artichoke will still cover the eastern United States a week from today. Forecast courtesy of NOAA

According to most long-range forecasts, Artichoke will keep the eastern United States in an Arctic chokehold (groaning allowed) for at least a week, probably twelve days, and possibly longer. As a result, Artichoke is not directly comparable to Astro, which is simply a snow event in the upper midwest.

When Artichoke Is Gone, Will There Be Other Frozen Vegetables?

The configuration in the jet stream of low pressure between Alaska and Russia, high pressure over the western US and eastern Pacific, and low pressure over the eastern US has been resilient to any attempts by waves in the jet stream to disrupt it.

Decoded Science has suggested that the pattern is anchored by anomalously warm water over the Gulf of Alaska.

Barring a major change in the overall pattern of high and low pressure systems across the Pacific, we should have enough vegetables for a nice stew by midwinter. The next one will be called Broccoli, whether Mr. Bush likes it or not.

Global Warming and Cold Weather

Though no single event can be linked to global warming, extreme weather events of unusual duration such as Artichoke are consistent with it. And a very large number of individual events can lead to the inductive conclusion that climate change is a fact beyond any reasonable doubt.

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