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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While the Atlantic Basin experienced a very active tropical season in 2017, global activity was actually below-normal for the year by one type of measurement thanks to quiet seasons in the northern Pacific Ocean and throughout the Southern Hemisphere. The global “accumulated cyclone energy” as we close out the year is 78% of normal year-to-date and there are currently no named tropical storms around the world.
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This is looking like a relatively quiet week across the country compared to last, but next week could turn out to be quite active with storm threats and brutal cold air is likely to plunge into the US from way up north. The bitter cold air mass will first arrive in the Northern Plains by this weekend and then it should spread across much of the rest of the nation during the early part of next week. “Teleconnection” signals support the notion that it turns very cold next week in much of the nation and the new year is likely to start in the deep freeze for many areas.
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Solar cycle 24 has turned out to be historically weak with the lowest number of sunspots since cycle 14 peaked more than a century ago in 1906 and by some measures, it is the third weakest since regular observations began around 1755. This historically weak solar cycle continues a weakening trend in solar irradiance output since solar cycle 21 peaked around 1980 and the sun is fast-approaching the next solar minimum. The last solar minimum lasted from 2008 to 2009 and the sun was as quiet during that time as it has been since 1978. The sun is likely to enter the next solar minimum phase within three years or so. The sun has been spotless for 26% of the time in 2017 (90 days) and the blank look should increase in frequency over the next couple of years leading into the next solar minimum.
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A major pattern change is going to begin on Wednesday in the Mid-Atlantic region and it will result in a period of sustained colder-than-normal temperatures that will assure a much different December compared to the last five. This pattern change to cold will also include increasing chances for snow – perhaps as early as late this week or during the upcoming weekend – as an active upper-level trough forms in the eastern US associated with the initial cold blast.
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If you still have to put up outside Christmas lights and rake some more leaves then this weekend may be the last chance with seasonal temperatures in the Mid-Atlantic region. There are continuing strong signs for a major pattern shift in the central and eastern half of the nation that will bring some serious and sustained cold thanks to a combination of strong high-latitude blocking centered over Greenland, an intensifying upper-level trough in the central and eastern US, and strong high-pressure ridging along the west coasts of the US and Canada. The transition time period from the current mild weather pattern to this upcoming cold pattern looks like it will come around next Wednesday, December 6th with the arrival of a strong cold frontal system in the eastern states that will be followed by a wall of cold.
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Mount Agung on the Indonesian island of Bali is showing increasing signs of heading towards a full-scale eruption. For the last several months, Bali’s largest volcano Mount Agung has been rocked by hundreds of earthquakes and in recent days has begun to spew ash and smoke high up into the atmosphere over this tropical island. If there is indeed a major eruption in this part of the world, it could have a significant impact on global temperatures for up to a couple of years. Mount Agung is one of more than 120 active volcanoes across Indonesia in the so-called Pacific “ring of fire”.
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While we are celebrating a chilly Thanksgiving Day in the Mid-Atlantic region, Summit Station in Greenland will experience high temperatures around -40°F which continues the very cold and well-below normal trend for the month of November. Summit Station (also known as Summit Camp) is a high-altitude (10,551 feet) year-round research station in central Greenland and its exact coordinates actually can change since the ice sheet underneath is often on the move. In addition to the bitter cold, snow and ice accumulation throughout Greenland has been running at the high end of normal since the fall of 2016 - at times at or near record levels - and NASA/MODIS satellite imagery reveals significant growth in the Petermann Glacier from a low point reached five years ago. One of the important reasons for closely monitoring the snow and ice buildup on Greenland is that this region can be an important cold air source for the central and eastern US during the upcoming winter season.
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The sun is blank again today and this marks the 70th day of the year in which there have been no visible sunspots which makes up nearly a quarter of the time in 2017. Historically weak solar cycle 24 continues to transition away from its solar maximum phase and towards the next solar minimum. The last solar minimum was historically long and deep lasting from 2008 to 2010. The blank look to the sun will increase in frequency over the next couple of years leading up to the next solar minimum - probably to be reached in late 2019 or 2020. By one measure, the current solar cycle is the third weakest since record keeping began in 1755 and it continues a weakening trend since solar cycle 21 peaked in 1980. One of the impacts of low solar activity is the increase of cosmic rays that can penetrate into the Earth’s upper atmosphere and this, in turn, can impact clouds on Earth. In addition, there is reason to believe that low solar activity can play an important role in winter weather conditions in the central and eastern US as it is well-correlated with more frequent "high-latitude blocking" events.
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Three important cold air sources for the central and eastern US in the winter season include Canada, Greenland and Siberia and two of these areas have had quite an impressive increase in snowpack in recent weeks and the third is about to receive widespread accumulations. As the snowpack builds up in these particular areas this time of year, cold air masses are very likely to follow as the nights grow longer going into winter season.
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