Yesterday we saw scattered rain showers with a few peeks of the sun. Our high temp was 70.5° and we saw a low of 62°. Our rainfall total for Otsego was .78 of an inch from the current system moving out.
With winter on the horizon, I suppose it is a good time to post explanations of how Arctic systems work and how it can affect our weather. Not seeing cold and snow or even a freeze in the near term as temps remain 10 to 15 degrees above normal.
Patterns in Arctic Weather and Climate
The map of sea level pressure for October 1 to 30, 2010, shows a high-pressure system centered over the Beaufort and Chukchi sea and Greenland, and low pressure over the Kara and Barents seas. This pattern tends to bring warm air from lower latitudes into the Arctic. —Credit: National Snow and Ice Data Center courtesy NOAA/ESRL PSD
The unique geography of the Arctic leads to unique weather patterns that reappear in the region year after year. Some weather patterns, such as cyclones or anticyclones, are common outside the Arctic. The Arctic Oscillation is an atmospheric circulation pattern that occurs over the mid-to-high latitudes of the Northern Hemisphere, including the Arctic.
Weather patterns that recur or persist over multiple seasons are called semipermanent highs and lows because these patterns show up in long-term averages of the regional weather.
Cyclones and Anticyclones
Cyclones, or low-pressure systems, are circular weather patterns that rotate in a counterclockwise direction. In a cyclone, air moves upwards in the center of the pattern, bringing stormy wet weather. In the Arctic, cyclones occur year-round, but they tend to happen more in certain places depending on the time of year. Semipermanent lows in the Arctic include the Aleutian Low, a low-pressure center that experiences many cyclones and storms in the winter, and the Icelandic Low, a low-pressure center located near Iceland.
Left: Cyclone, Right: Anticyclone
—Credit: M. Ritter/University of Wisconsin Stevens Point
Anticyclones are the opposite of cyclones, high-pressure systems that rotate in a clockwise direction. An anticyclone known as the Beaufort High recurs year after year, sitting over the Beaufort Sea and Canadian Archipelago in winter and spring. An anticyclone also frequently appears over Siberia, known as the Siberian High.
Polar Lows
Cyclone over the Arctic Ocean.
—Credit: NASA/MODIS
Polar lows are small, intense cyclones that form over the open ocean during the cold season. From satellite imagery, polar lows can look much like a hurricane, with a large spiral of clouds centered around an eye—for this reason, they are sometimes called Arctic hurricanes. Polar lows range in size from around 100 to 500 kilometers (62 to 310 miles) in diameter. Wind speeds average around 50 miles per hour, although they can occasionally reach hurricane strength (64 miles per hour).
Polar lows tend to form when cold Arctic air flows over relatively warm open water. The storms can develop rapidly, reaching their maximum strength within 12 to 24 hours of formation, but they dissipate just as quickly, lasting on average only one or two days.
Semipermanent Highs and Lows
Weather maps show the circulation and pressure patterns over one or several days. But maps of sea level pressure can also be averaged over several months or years, to show the average circulation patterns in the atmosphere. These averaged maps remove some of the variability caused by day-to-day weather changes, instead of showing longer-term patterns that can affect weather and climate both within and outside of the Arctic.
Researchers compare the relative strengths of semipermanent highs and lows and report these comparisons in indices such as the North Atlantic oscillation and the Arctic oscillation. These indices have been linked to variability in temperatures and to sea ice conditions in the Arctic.
Explore Further: Semipermanent Patterns list some important semipermanent patterns.
Arctic Oscillation
The Arctic Oscillation refers to an opposing pattern of pressure between the Arctic and the northern middle 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 phases. 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.
Left: Effects of the Positive Phase of the Arctic Oscillation. Right: Effects of the Negative Phase of the Arctic Oscillation. —Credit: J. Wallace, University of Washington.
Explore Further: 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 the 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.
- Drying out into Wednesday An area of high pressure builds into the Great Lakes Region today into Wednesday. Subsidence associated with this feature supports the column drying out. Low level moisture and shallow lift to start the day today could lead to a few sprinkles for southern parts of the CWA. Later in the day and into Wednesday the RH values drop off. This will result in the clouds breaking up. Wednesday should feature some sun to start the day but clouds will be thickening up in the afternoon. - Showers return Wednesday night then wet into Friday A weakening mid level low tracks in from the south during this time. It will be drawing up some Gulf moisture with PWAT values topping 1.5 inches. Bufkit overviews show deeper moisture around during this time and some lift...especially Thursday afternoon. A weak 850 mb LLJ is shown to be aimed at Southern Lower MI at 00z Friday Slight instability arrives as well so a thunderstorm or two cannot be ruled out. Models are in relative agreement on this scenario. We will feature increasing POPs Wednesday night into Thursday afternoon and then hold the relatively high POPs into Friday. - Above normal temperatures into the weekend The mid to upper level flow will generally feature a southerly component through the period here in the Great Lakes Region. This will act to aim any cold air masses away from the area. With above normal temperatures at 925 mb to 850 mb the surface temperatures in the area will stay warmer than normal for this time of the year. For Grand Rapids...normal high/low temps today are 66/46. Easterly flow into Wednesday should act to support the highest max temps along and west of US-131.
Winter = the best season in MI! Hands down and no competition!
Arctic patterns! Now we are talking! I can’t wait till the Polar Vortex appears and sticks with us for weeks on end this winter! Wouldn’t that be awesome?