In general, the Pacific Ocean has had more tropical activity this season compared to the Atlantic Basin and that trend should continue in the near term. Sea surface temperatures are playing a role in this trend and they are currently warmer-than-normal in the vicinity of Hawaii with a major hurricane headed in that direction. Fortunately, Hurricane Lane is likely to not make a direct hit on the islands and it should undergo steady weakening in coming days due to increasing amounts of wind shear. Nonetheless, Hurricane Lane will be a formidable storm for the state of Hawaii with potential significant impact in terms of rainfall; especially, on the Big Island. This is very likely not going to be the last tropical threat for Hawaii this season as warmer-than-normal sea surface temperatures and a developing El Nino in the central Pacific Ocean will likely aid in the formation of additional systems in coming days.
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It was shortly after noon on August 24th in the year 79 A.D. and Mount Vesuvius sent a tall cloud of steam and ash high up into the atmosphere. The ancient Roman town of Pompeii near modern day Naples was soon covered in complete darkness and the thickness of the falling debris increased by about 6 to 8 inches per hour. The rocks which comprised the debris were up to 3 inches in diameter and fell with a speed of up to 100 miles/hour. This first phase of the eruption led to casualties primarily caused by roof collapses. After 12 hours of continuous explosive activity, the second phase of the eruption began and it was characterized by substantial flow of lava down the sloping Mount Vesuvius and this caused additional deaths and destruction. In fact, the eruption of Mount Vesuvius spewed 1.5 million tons of lava per second into Pompeii and surrounding towns. In a short period of time, two thousand people were killed, the small towns of Herculaneum, Oplonti and Stabiae were destroyed, and Pompeii was changed forever.
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The Atlantic Basin has been relatively quiet in recent days in terms of tropical activity and it continues to look like this will be a less active tropical season compared to 2017. One of the main factors that led us to an outlook for a less active tropical season back in the springtime was the large patch of colder-than-normal water at that time in the eastern Atlantic Ocean. This continues to exist and is quite likely an inhibiting factor for the formation or intensification of tropical activity in the tropical Atlantic and there are a couple other factors as well that are likely deterring activity. First, Saharan Desert (dry) air has persistently flowed westward from western Africa and into the tropical Atlantic and there are signs that this general pattern will continue into at least the near future. In addition, wind shear has been quite prominent across the tropical Atlantic in recent days and there are reasons to believe that this will continue to impede tropical activity in coming weeks. Don’t let your guard down; however, as all it takes is a direct hit by one storm to make it a memorable tropical season.
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In recent days, Arctic sea ice volume has been running at levels above the mean of the base period from 2004-2013 and it is above the levels seen during each of the past three years. Arctic sea ice extent has been relatively stable during the past decade or so albeit consistently at below-normal levels. This recent uptick in Arctic sea ice volume relative to prior years and the relative stability over the past decade or so in sea ice extent is related to long-term temperature trends in the Arctic region. Specifically, despite the fact that Arctic temperatures have often run at above-normal levels in the cold season during recent years, they have usually been running at nearly normal levels during the all-important summer melting season. Above-normal temperatures during the cold season in the Arctic are usually well below freezing which minimizes the overall impact on the melting of sea ice. The summer season is when temperatures are typically slightly above the freezing mark and any sustained warmer-than-normal conditions during those particular months would likely have an important impact on sea ice; however, this scenario has not been happening for many years.
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One of the most important stories in recent weeks in the world of weather and climate has been the abnormally cold waters of the northern Atlantic Ocean. This colder-than-normal patch of water just south of Greenland has been sustained for several weeks now and it is likely playing a role in Greenland’s extensive and abnormally high snow/ice pack for this time of year. In addition, this cold water just south of Greenland may be playing a role in overall colder-than-normal air temperatures in the Arctic region during their all-important summer melting season and the latest estimates of Arctic sea ice extent which compare favorably to recent years.
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One of the most widespread and destructive heat waves ever recorded in the US took place in the summer of 1936 which fell right in the middle of the hottest and driest decade ever for the nation. The decade of the 1930’s is renowned for the “Great Depression” and the “Dust Bowl”, both of which caused calamitous human suffering in this country. Not only were huge numbers of crops destroyed by the heat and lack of moisture in the “Dust Bowl” era, but thousands of lives were lost as a result of the heat, drought and economic hardship. Many of the all-time high temperature records that were set in the decade of the 1930’s still stand today. The heat wave experienced in 1936 began in late June, reached a peak in July, and didn’t really come to an end until September. This extreme heat wave was particularly deadly; especially, in high population areas where air conditioning was still in the early stages of development.
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The sun is blank today for the 15th straight day which is the longest stretch without sunspots since November 2009 when the sun was emerging from the deepest solar minimum in a century. This year the sun has been blank 52% of the time which is the most in a given year since the 71% that took place in 2009. The 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 - and the longest consecutive streak in 2008 reached 52 days according to spaceweather.com. All indications are that the upcoming solar minimum may even be even quieter than the last one. 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. In addition, there tends to be a drop in total solar irradiance with the approach of a solar minimum.
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The high temperature forecast in Death Valley, California for the next couple of days is an impressive 115°F or so, but this is rather pedestrian compared to the all-time record high that occurred on this date one hundred and five years ago. On July 10th, 1913, the weather observer at Greenland Ranch in Death Valley recorded a high temperature of 134°F. One hundred and five years later, this is still the highest air temperature ever reliably recorded on Earth. In addition to this all-time and worldwide high temperature record, the year of 1913 produced numerous other extreme weather events.
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The summer solstice has just passed and the days will grow shorter and shorter from here on out until the winter season gets underway. While winter is still a long way off, there are already some clues that can provide some insight as to what kind of weather we can expect around here in the Mid-Atlantic region. First, signs point to the formation of warmer-than-normal sea surface temperatures by the upcoming winter season in two key areas of the Pacific Ocean: 1) the central equatorial region and 2) the Gulf of Alaska. Second, there is little doubt that solar activity will remain on the low side through the upcoming winter season as we are rapidly approaching the next solar minimum phase from an already historically weak solar cycle #24. Finally, one important wintertime cold air source region for the Mid-Atlantic is Greenland and it is currently experiencing above-normal snow and ice cover. While this is in the speculation phase, all of these factors point to the possibility of cold and snowy conditions in the Mid-Atlantic region during the upcoming 2018-2019 winter season.
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The Atlantic Basin tropical season is still rather young having “officially” just begun a few weeks ago on June 1st, but there have been two factors so far that have suppressed activity and they may not let up anytime soon. First, sea surface temperatures have been running at below-normal levels in the all-important "breeding grounds" region of the tropical Atlantic Ocean in the region extending from the west coast of Africa to the Caribbean Sea. Second, there has been a persistent flow of dry air moving westward from the Sahara Desert region of Africa into this same "breeding grounds" region of the tropical Atlantic Ocean. Both of these factors tend to inhibit the formation of tropical storms or the intensification of storms that actually do manage to form.
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