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Arctic Oscillation

Over the past couple weeks I have been trying to show all the variables which go into a winter forecast.  Today will be a discussion on the Arctic Circle and Climatology.  The feature image is of my own creation…

The Arctic Oscillation (AO) is a large scale mode of climate variability, also referred to as the Northern Hemisphere annular mode. The AO is a climate pattern characterized by winds circulating counterclockwise around the Arctic at around 55°N latitude. When the AO is in its positive phase, a ring of strong winds circulating around the North Pole acts to confine colder air across polar regions. This belt of winds becomes weaker and more distorted in the negative phase of the AO, which allows an easier southward penetration of colder, arctic airmasses and increased storminess into the mid-latitudes.

Overall, if the atmospheric pressure is high in the Arctic, it tends to be low in the northern middle latitudes, such as northern Europe and North America. If atmospheric pressure is low in the middle latitudes it is often high in the Arctic. When pressure is high in the Arctic and low in mid-latitudes, the Arctic Oscillation is in its negative phase. In the positive phase, the pattern is reversed.

Meteorologists and climatologists who study the Arctic pay attention to the Arctic Oscillation, because its phase has an important effect on weather in northern locations. The positive phase of the Arctic Oscillation brings ocean storms farther north, making the weather wetter in Alaska, Scotland, and Scandinavia and drier in the western United States and the Mediterranean. The positive phase also keeps weather warmer than normal in the eastern United States, but makes Greenland colder than normal.

In the negative phase of the Arctic Oscillation the patterns are reversed. A strongly negative phase of the Arctic Oscillation brings warm weather to high latitudes, and cold, stormy weather to the more temperate regions where people live. Over most of the past century, the Arctic Oscillation alternated between its positive and negative phase. For a period during the 1970s to mid-1990s, the Arctic Oscillation tended to stay in its positive phase. However, since then it has again alternated between positive and negative, with a record negative phase in the winter of 2009-2010.

Semipermanent Patterns

The semipermanent patterns listed below are centers of action in the Arctic atmosphere, influencing weather patterns in the Arctic and around the world.

  • Aleutian Low: This semipermanent low-pressure center is located near the Aleutian Islands. Most intense in winter, the Aleutian Low is characterized by many strong cyclones. Traveling cyclones formed in subpolar latitudes in the North Pacific usually slow down and reach maximum intensity in the area of the Aleutian Low.
  • Icelandic Low: This low-pressure center is located near Iceland, usually between Iceland and southern Greenland. Most intense during winter, it weakens and splits into two centers in summer, one near Davis Strait and the other west of Iceland.
  • Azores High: The Azores High is a high-pressure pattern that forms in the subtropical Atlantic Ocean. Although it occurs outside the Arctic Ocean, it is linked to the Icelandic Low through the North Atlantic oscillation.
  • Siberian High: The Siberian High is an intense, cold anticyclone that forms over eastern Siberia in winter, associated with frequent cold air outbreaks over east Asia.
  • Beaufort High: The Beaufort High is a high-pressure center over the Beaufort Sea present mainly in winter.
  • North American High: The North American High is a relatively weak area of high pressure that covers most of North America during winter. This pressure system tends to be centered over the Yukon, but is not as well-defined as its continental counterpart, the Siberian High.

The Arctic region acts as a heat sink for the Earth: the Arctic loses more heat to space than it absorbs from the sun’s rays. In contrast, lower latitudes get more heat than they lose to the atmosphere. Warm air and water move into the Arctic from tropical and temperate regions. Some of this heat then escapes through the Arctic atmosphere. Over a whole year, the heat gain in lower latitudes gets balanced out, on average, by heat loss in the polar regions.


We are getting our first soaking rains since August (we had 4.52 inches that month).  We have had 1.46 inches from midnight to 7am) which brings our total to 2.91 for the month – these are Otsego measurements.

Low pressure will track south of Lower Michigan today with rain tapering off to showers by the afternoon. A few light showers will linger for Thursday then fair weather is expected for Friday before our next soaker comes in for later in the weekend.

Still no sign of frost in the forecast through the 27th, we may have to wait until early November.  I think it is safe to say we won’t be seeing any more 80° days, the 70s will be few and far between and the 60s will be more dominate with a few 50° sprinkled in.  I still think we will see a colder air pattern later in November.

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Barry in Zeeland
Barry in Zeeland

Thanks for posting all this info Michael! I hope there’s not a quiz at the end! 2.02 inches of rain here, one of our larger rainfall totals for the year.

ROCKY (Rockford)
ROCKY (Rockford)

I love a negative AO. Bring on the polar vortex this winter and well over 100 inches of SNOW!