As we know full well here in the Mid-Atlantic region, there have been an unusual frequency of late winter and early spring cold air outbreaks leading to consistently below-normal temperatures during March and April. This extended period of unusual cold has also impacted other parts of the nation including the Ohio Valley, Great Lakes, central and northern Plains, and parts of the Southeast US. The late season cold has also had an inhibiting effect on the tornado season so far across much of the US with overall numbers way down compared to normal. In fact, the state of Oklahoma – right in the heart of tornado alley – is about to set a record for their latest first tornado ever.
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While consistently at below-normal levels since the mid 1990’s, Arctic sea ice extent has stayed relatively stable during the past decade or so. This recent stability in Arctic sea ice extent is likely due mainly to the fact that temperatures have been regularly near-normal during the all-important summer season and peak melting time of the year. Temperatures have often run at above-normal levels during the cold season in the Arctic, but during those particular months, conditions are usually well below freezing which minimizes the impact on the melting of sea ice. In the summer season, Arctic temperatures are slightly above the freezing mark from a climatological viewpoint and this is the time of year when sustained warmer-than-normal conditions could have an important impact on sea ice extent, but it just hasn’t been happening that way in an extended period of time.
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The sun is blank today for the 10th straight day and it has been without sunspots this year more than half the time as the current solar cycle (#24) heads towards the next solar minimum. The last time the sun was this blank in a given year on a percentage basis was 2009 during the last solar minimum when 71% of the time was spotless. That last solar minimum actually reached a nadir in 2008 when an astounding 73% of the year featured a spotless sun - the most spotless days in a given year since 1913. All indications are that the upcoming solar minimum may be even quieter than the last one which was the deepest in nearly a century. One of the natural consequences of low solar activity is the weakening of the solar wind and its magnetic field which, in turn, allows for the intensification of cosmic rays and easier access to Earth.
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The sun is blank today for the 10th straight day and it has been without sunspots this year more than half the time as the current solar cycle heads towards the next solar minimum. Solar cycle 24 is currently on pace to be the weakest sunspot cycle with the fewest sunspots since cycle 14 peaked in February 1906. Solar cycle 24 continues a recent trend of weakening solar cycles which began with solar cycle 21 that peaked around 1980. The last time the sun was this blank in a given year on a percentage basis was 2009 during the last solar minimum when 71% of the time was spotless. That last solar minimum actually reached a nadir in 2008 when an astounding 73% of the year featured a spotless sun - the most spotless days in a given year since 1913.
All indications are that the upcoming solar minimum which is expected to begin in 2019 may be even quieter than the last one which was the deepest in nearly a century. One of the natural impacts of decreasing solar activity is the weakening of the ambient solar wind and its magnetic field which, in turn, allows more and more cosmic rays to penetrate the solar system. The intensification of cosmic rays can have important consequences on such things as Earth’s cloud cover and climate, the safety of our astronauts exploring in space, and lightning.
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High-latitude blocking refers to an atmospheric pattern in which higher heights (and pressure) compared to normal sets up in high latitude regions such as Greenland or northern Canada and it can remain in place for an extended period of time leading to a large-scale obstruction of surface weather systems. High-latitude blocking tends to be more likely during periods of low solar activity and that is certainly the case now as (weak) solar cycle 24 heads towards the next solar minimum. During the latter stages of winter, this type of setup can result in a persistent colder-than-normal weather pattern for the central and eastern US and perhaps stormy conditions as well. All signs point to a strong high-latitude blocking pattern to develop later this week across the North America side of the North Pole and this virtually ensures winter will not go down without a fight in March in the central and eastern US. This change in the overall pattern will also likely result in the generation of a powerful ocean storm late this week just off the Mid-Atlantic coastline and it will likely be a slow mover.
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There has been a major stratospheric warming event over the past couple of weeks with a displacement of the polar vortex to lower latitudes and over the next several days a significant high-latitude blocking event will unfold leading to way above normal heights over places like Greenland and northeastern Canada. These large-scale atmospheric events are having an impact on weather patterns all across the Northern Hemisphere. They will be contributing factors to the extreme cold that is about to invade Europe from the east (Siberia) and to a cold pattern that looks like it will develop across much of the US during March which may feature a nor'easter during the transition period late next week.
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While the South Pacific has held its breath over the fate of Bali’s roaring Mount Agung, another volcano in the vicinity has been letting off its own steam. Mount Sinabung is among more than 120 active volcanoes in Indonesia, which is prone to seismic upheaval due to its location on the Pacific "Ring of Fire," an arc of volcanoes and fault lines encircling the Pacific Basin. The volcano in North Sumatra, which has been active since 2010 after centuries of dormancy, had its strongest eruption in five years on Monday morning.
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There is abundant very cold air around in the Northern Hemisphere (e.g., Arctic dips to -76°F) as we reach the mid-point of February and snowfall has been very impressive in recent days from British Columbia-to-Chicago-to-Paris-to-Moscow, but unless the atmospheric flow pattern changes, this abnormal cold and potential snow won’t necessarily come to the eastern US. In fact, the weather pattern in the eastern US has featured multiple mild spells in recent days and little in the way of snowfall for the immediate I-95 corridor, and the overall mild weather pattern looks like it will continue for the next week-to-ten days. After that, however, there are numerous signs that suggest there will be a crucial change to the overall atmospheric pattern over the Northern Hemisphere and this will likely allow for multiple cold air outbreaks to once again be directed into the eastern US.
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One of the ways to monitor the potential for wintertime Arctic air outbreaks in the central and eastern U.S. is to follow what is happening in the stratosphere over the Northern Hemisphere. Sudden Stratospheric Warmings (SSWs) are large, rapid temperature rises in the winter polar stratosphere, occurring primarily in the Northern Hemisphere, and these events have been found to set off a chain of events in the atmosphere that ultimately can lead to Arctic air outbreaks for the central and eastern US that drop southward from northern Canada. Indeed, there is a significant stratospheric warming event now unfolding that will soon result in a dominant polar vortex center over North America - somewhat similar to a major SSW event that took place in January 1985. In that particular year, the major SSW event was soon followed by a period of extreme cold in the central and eastern US.
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We are now experiencing warmer-than-normal weather conditions in the eastern US and there will be mild spells right into the first week of February, but the signs are increasing for a return to a cold pattern next month and it may very well last for an extended period of time. The MJO is a tropical disturbance that propagates around the global tropics and it will be transitioning into “phases” during the month of February that are conducive to colder-than-normal weather in the eastern US. In addition, stratospheric warming will unfold over the next week or so in the polar region of the Northern Hemisphere and this can set off a chain of events in the atmosphere that ultimately results in colder-than-normal weather for the eastern US. There are other signals as well that support the notion of a return to colder-than-normal in the eastern US and it very well could stick around for awhile.
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