10:15 AM | Weakest solar cycle in a century

[current solar image courtesy NASA]

Discussion

Overview We are now about halfway through the solar maximum phase of the current solar cycle, 24, but it is remarkably weak relative to previous cycles. In fact, solar cycle 24 is on a pace that would make it the weakest cycle in one hundred years. Not since solar cycle 14 which peaked in 1906 have we experienced such a weak solar cycle. Solar cycle 24 began after an unusually deep solar minimum that lasted from 2007 to 2009. In fact, in 2008 and 2009, there were almost NO sunspots, a very unusual situation that had not happened for almost a century.

Consequences of a weak solar cycle First, the weak solar cycle has resulted in rather benign “space weather” in recent times with generally weaker-than-normal geomagnetic storms. Research suggests that this is likely due to reduced magnetic field strength inside the coronal mass ejections that shoot off the sun’s surface. The milder space weather reduces drag on satellites which makes it easier to keep them in orbit; however, it also allows space junk to last longer which can pose problems for operational satellites.

Second, it is pretty well understood that solar activity has a direct impact on temperatures at very high altitudes in a part of the Earth’s atmosphere called the thermosphere. This is the biggest layer of the Earth’s atmosphere which lies directly above the mesosphere and below the exosphere. Thermospheric temperatures increase with altitude due to absorption of highly energetic solar radiation and are highly dependent on solar activity.

Finally, if history is a guide, it is safe to say that weak solar activity for a prolonged period of time can have a negative impact on global temperatures in the troposphere which is the bottom-most layer of Earth’s atmosphere - and where we all live. There have been two notable historical periods with decades-long episodes of low solar activity. The first period is known as the “Maunder Minimum”, named after the solar astronomer Edward Maunder, and it lasted from around 1645 to 1715. The second one is referred to as the “Dalton Minimum”, named for the English meteorologist John Dalton, and it lasted from about 1790 to 1830. Both of these historical periods coincided with below-normal global temperatures in an era now referred to by many as the “Little Ice Age”. In addition, research studies in just the past couple of decades have found a complicated relationship between solar activity, cosmic rays, and clouds on Earth. This research suggests that in times of low solar activity where solar winds are typically weak; more cosmic rays reach the Earth’s atmosphere which, in turn, has been found to lead to an increase in certain types of clouds that can act to cool the Earth.

Outlook The increasingly likely outcome for a weak solar cycle continues the recent downward trend in sunspot cycle strength that began over twenty years ago with solar cycle 22. If this trend continues for the next couple of cycles, then there would likely be more talk of another “grand minimum” for the sun. Some solar scientists are already predicting that the next solar cycle, 25, will be even weaker than this current one. However, it may be just a bit too early for high confidence in these predictions since some solar scientists believe that the best predictor of future solar cycle strength involves activity at the sun’s poles during a solar minimum and the next solar minimum is still likely several years away.

Video

httpv://youtu.be/QN_iIyqy9G0

12:15 PM | Global sea ice areal extent at highest level since 1994; southern hemisphere continues on an amazing run

Discussion

The southern hemisphere sea ice areal extent continues its recent impressive run at daily record high levels when compared to all prior years in the satellite record-keeping era which began in 1979. This stretch of daily record high sea ice areal extent in the southern hemisphere has actually been occurring for the past several weeks. In fact, the southern hemisphere sea ice areal extent has had quite an amazing run during the past few years from below normal levels to the current well above normal values (above map courtesy University of Illinois "cryosphere"). On a global basis, sea ice areal extent is currently above normal and, in fact, has now reached levels not seen since around 1994 - thanks in large part to the happenings in the southern hemisphere.

The northern hemisphere sea ice areal extent is still below normal for this time of year although it has gained significantly compared to one year ago. In general, the northern hemisphere sea ice areal extent has been at below normal levels since the mid 1990’s. Two distinct trend lines can be seen in the northern hemisphere sea ice areal extent dating back to 1979. First, the northern hemisphere sea ice areal extent featured an “above normal” and general “sideways” trend until the mid 1990’s and then, following that point in time, there has been an overall downward trend to the current below normal values. This directional change in trend during the mid 1990’s correlates quite well with a northern Atlantic Ocean sea surface temperature cycle that is tracked by meteorologists through an index called the Atlantic Multidecadal Oscillation (AMO). Indeed, the Atlantic Ocean has a significant impact on northern hemisphere sea ice and the AMO index flipped in phase during the mid 1990’s from negative (cold) to positive (warm), and the northern hemisphere sea ice areal extent has been in a general downward trend ever since. Once the northern Atlantic Ocean sea surface temperatures flip back to cooler-than-normal values – perhaps 5 or 10 years from now - the northern hemisphere sea ice areal extent should return to the normal or above normal levels seen prior to the mid 1990’s.

Video

httpv://youtu.be/wSV_VPvbj_g

12:00 PM | 2013-2014 Winter Outlook for the Mid-Atlantic Region

Video

httpv://youtu.be/KMh5WcZwBCo

Discussion

Looks like the Mid-Atlantic region is leaning towards the colder and snowier side of normal for the upcoming winter of 2013-2014…

Recap of last winter Last winter featured warmer-than-normal conditions in the Mid-Atlantic region during December and January, but then temperatures slid to slightly below normal during February and well below normal in March. Perhaps the most memorable feature from last winter is that there, in fact, were no memorable snowstorms. While several small snow accumulation events did occur in the region, there were no significant storms last winter with anything above 4 inches or so. This winter, however, should feature some episodes in which the timing will be just right between cold air outbreaks, an active southern jet, and storminess to produce significant snow events.

There are three major factors that will play an important role in the winter weather around here:

1) Lack of a strong El Nino/Southern Oscillation (ENSO) signal in the tropical Pacific Ocean 2) Low solar activity that frequently leads to high latitude blocking and, in turn, Arctic air outbreaks for the central and eastern US 3) Above normal snowpack across the Northern Hemisphere

Neutral ENSO signal in the tropical Pacific Ocean All indications are that the sea surface temperature (SST) anomalies in the tropical Pacific Ocean will stay rather close to neutral during the upcoming winter season. It is very likely that there will be not be a strong El Nino (warmer-than-normal SSTs) or La Nina (colder-than-normal SSTs) any time soon in the tropical Pacific Ocean and that tends to open the door for a bigger influence around here from another part of the world such as in the northern latitudes and the North Atlantic Ocean. A strong signal from the tropical Pacific Ocean would typically become the dominating factor with respect to Mid-Atlantic winter weather no matter what takes place elsewhere around the world; however, with a neutral signal expected this winter, it is time to look elsewhere.

Low solar activity and high latitude blocking Research has shown that low solar activity tends to lead to the formation of a blocking pattern in the high latitudes (e.g., Greenland) during winter months which, in turn, leads to numerous Arctic air outbreaks into the central and eastern US from central Canada. While we are actually in a period of solar maximum for the current solar cycle, #24, it happens to be one of the weakest solar cycles in many decades and low solar activity is expected to continue this winter. Indeed, a look at numerous analog years with low solar activity reveals an unmistakable signal for high latitude blocking during winter months. This type of blocking pattern can be tracked through an index called the North Atlantic Oscillation (NAO) which would typically turn negative in times of high latitude blocking, and I expect that to happen frequently during this upcoming winter season as this may turn out to be the most important factor of all.

Above-normal snowpack in the Northern Hemisphere An important source region for cold air in this part of the US during the winter season is Eurasia - on the other side of the North Pole - and studies have shown that when snowpack increases in that part of the world during the month of October, and is above normal at the end of the month, then Arctic cold air outbreaks are sure to follow during the subsequent winter months in the central and eastern US. Indeed, snow cover in Eurasia increased dramatically during October reaching above normal levels by the end of the month. In fact, the Eurasian snowpack reached the 4th highest level in the past 46 years and the entire Northern Hemisphere snow cover reached the 7th highest level in that same 46 year period.

Summary of Winter Outlook for the Mid-Atlantic Region: The Mid-Atlantic region will lean towards the colder and snowier side of normal with temperatures some 0.5 to 1.0 degrees below normal for the winter season (November through March) and snowfall at 100-140% of normal. Normal snowfall amounts (which should be the minimal amounts this winter) are as follows: 15” at DCA, 21” at BWI, 21” at PHL, 29” at Central Park, NY

12:15 PM | Possible CME impact on Halloween Day

Discussion

As October comes to an end, the sun continues to be speckled with active sunspot regions generating numerous solar flares and the result will be a series of coronal mass ejections (CMEs) that will sweep past the Earth over the next few days. The first few of these are expected to deliver only glancing blows to the Earth’s atmosphere between now and tomorrow night, but a more direct hit is likely on Thursday, October 31st (Halloween Day). This more direct hit is the result of an eruption from Earth-facing sunspot AR1882 that occurred on Monday and reached solar flare M4-classification. High-latitude sky watchers should be on alert for possible auroras on Halloween Day (likely cloudy in the Mid-Atlantic region). Additional solar flares are possible in the next few days that could have an impact on the Earth’s upper atmosphere as multiple sunspot regions are still in Earth-facing locations.

2:30 PM | *Major activity on the sun*

Discussion

Solar activity remains high and intensifying. There is now a new sunspot called AR1882 which rotated over the sun’s eastern limb earlier today and it appears to have erupted with two X-class solar flares (most intense classification). Other sunspot regions called AR1875 and AR1877 have continued to erupt with lesser flares as they rotate towards the sun’s western limb. One of the X-class flares with the new sunspot region was bracketed by two erupting magnetic filaments each located hundreds of thousands of kilometers away from AR1882 which means the flare may been part of an interconnected global solar eruption. More solar flares are in the offing as these three sunspot regions, AR1875, AR1877 and the new AR1882 are on the Earthside of the sun and capable of additional solar eruptions.

12:45 PM | Global sea ice update...Arctic region gaining considerable ground from a year ago and southern hemisphere at record high for this time of year in terms of areal extent

[Data maps from the Naval Research Laboratory show the change in Arctic ice thickness from one year ago (bottom) to the current levels (top) with a substantial increase]

Discussion

The southern hemisphere sea ice areal extent continues to run at record highs for today’s date as has been the case for the past couple of weeks using records that go back to 1979 when satellite observations began. In an unusual fashion, the southern hemisphere just recently reached a peak in sea ice areal extent which is a couple of weeks past the normal time of year for this to occur. The southern hemisphere is now heading into their warm season and the areal extent will continue to drop in magnitude.

Meanwhile, the northern hemisphere sea ice areal extent is still running at below normal levels; however, it has increased significantly from last year’s record low amount and its thickness has also grown considerably from one year ago. There have been two distinct trend lines in the northern hemisphere sea ice areal extent dating back to the beginning of satellite era and there seems to be a direct connection with an oceanic cycle in the north Atlantic involving sea surface temperatures. The Arctic region north of the Atlantic Ocean is open to the warmer waters from the south because of the way the ocean currents flow. These warmer waters can flow into the Arctic and prevent sea ice from forming in the North Atlantic. The northern Atlantic Ocean sea surface temperatures are tracked by meteorologists through an index called the Atlantic Multidecadal Oscillation (AMO) and the two distinct trend lines for northern hemisphere sea ice areal extent are quite well correlated with a flip in phases of the AMO in the mid 1990’s from negative (colder water) to positive (warmer water). Specifically, the northern hemisphere sea ice areal extent featured a general sideways trend at above normal levels from 1979 to the mid 1990’s and then, following that flip in the AMO, there has been an overall downward trend to the current below normal values. These oceanic cycles can last for two or three decades and I believe that when the northern Atlantic sea surface temperatures flip back to cooler-than-normal values – perhaps 5 or 10 years from now - the northern hemisphere sea ice areal extent will return to normal or above normal levels - much like it was before the mid 1990’s while the AMO was negative.

Video

httpv://youtu.be/1uEX9isbBEc

1:00 PM | Suddenly active sun could produce significant solar flares in the next couple of days

Discussion

The sun has become much more active in recent days and there are now two huge sunspot regions directly in the line of fire with the Earth. Sunspot AR1875 is a fast-growing sunspot region that has developed a “beta-gamma-delta” magnetic field that harbors energy strong explosions. NOAA forecasters estimate a 30% chance of M-class solar flares and a 5% chance of X-class solar flares during the next 24 hours or so. Scientists classify solar flares according to their x-ray brightness in the wavelength range 1 to 8 Angstroms. There are 3 categories: X-class flares are big; they are major events that can trigger planet-wide radio blackouts and long-lasting radiation storms. M-class flares are medium-sized; they can cause brief radio blackouts that affect Earth's polar regions. Minor radiation storms sometimes follow an M-class flare. Compared to X- and M-class events, C-class flares are small with few noticeable consequences here on Earth. Yesterday, sunspot region AR1875 produced a M4-class solar flare and it has actually grown in size some since then.

We are currently over four years into Solar Cycle 24 and it has been on a pace that would make it the smallest sunspot cycle since Cycle 14 which peaked in February 1906. However, this cycle is now in a period of solar maximum and there has been some thought that a sharp uptick in activity could occur as we progressed through the year. We’ll continue to monitor the situation and report on any significant coronal mass ejection (CME) that might occur over the next few days.

11:50 AM | 2013 - a year with minimal extreme weather events in the US

Discussion

There have been many forecasts in the news in recent years predicting more and more extreme weather-related events in the US, but for 2013 that prediction has been way off the mark. Whether you’re talking about tornadoes, wildfires, extreme heat or hurricanes, the good news is that weather-related disasters in the US are all way down this year compared to recent years and, in some cases, down to historically low levels.

Tornadoes To begin with, the number of tornadoes in the US this year is on pace to be the lowest total since 2000 and it may turn out to be the lowest total in several decades. The table below lists the number of tornadoes in the US for this year (through 10/17) and also for each year going back to 2000. (Source: NOAA, http://www.spc.noaa.gov/climo/online/monthly/newm.html)

Year         # of Tornadoes 2013                    771 2012                   1119 2011                   1894 2010                   1543 2009                   1305 2008                   1685 2007                   1102 2006                   1117 2005                   1262 2004                   1820 2003                   1374 2002                    938 2001                   1219 2000                   1072

Wildfires Second, the number of wildfires across the US so far this year is on pace to be the lowest it has been in the past ten years and the acreage involved is at the second lowest level in that same time period (table below). (Source: National Interagency Fire Center; http://www.nifc.gov/)

2013            Fires: 40,306           Acres: 4,152,390 2012            Fires: 67,774           Acres: 9,326,238 2011            Fires: 74,126           Acres: 8,711,367 2010            Fires: 62,471           Acres: 3,233,461 2009            Fires: 78,792           Acres: 5,921,786 2008            Fires: 80,094           Acres: 5,254,109 2007            Fires: 85,822           Acres: 9,321,326 2006            Fires: 96,358           Acres: 9,871,939 2005            Fires: 66,552           Acres: 8,686,753 2004            Fires: 63,608           Acres: 8,097,880 *2013 data through 10/16

Extreme Heat In addition to wildfires, extreme heat is also way down across the US this year. In fact, the number of 100 degree days across the country during 2013 is not only down for this year, but it is perhaps going to turn out to be the lowest in about 100 years of records (chart below).

(Source: NOAA, USHCN reporting stations; through August)

The five summers with the highest number of 100 degree days across the US are as follows: 1936, 1934, 1954, 1980 and 1930. In addition to the vast reduction in 100 degree days across the US this year, the number of high temperature records (ie hi max and hi min records) is way down compared to a year ago with 22,965 records this year as compared with 56,885 at this same time last year. (Source: NOAA, http://www.ncdc.noaa.gov/extremes/records/; through 10/17).

Hurricanes Finally, as far as hurricanes are concerned and keeping in mind that the season isn't over yet, there have been only two hurricanes so far this year in the Atlantic Basin (Humberto and Ingrid) and they were both short-lived and weak category 1 storms. Also, the first forming hurricane this year occurred at the second latest date going back to the mid 1940’s when hurricane hunters began to fly. Overall, the tropical season in the Atlantic Basin has been generally characterized by short-lived and weak systems.

In addition, this suppressed tropical activity has not been confined to just the Atlantic Ocean. The eastern Pacific Ocean has had no major hurricanes this season meaning there has been no major hurricane in either the Atlantic or eastern Pacific which only occurred one other year in recorded history – 1968. This is actually quite extraordinary since the two basins are generally out of phase with each other i.e. when one is inactive the other is active.

One of the best ways to measure “total seasonal activity” in the tropics is through an index called the Accumulated Cyclone Energy (ACE) which is a metric that accounts for both intensity and duration of named tropical storms. Indeed, the ACE for this tropical season so far in the Atlantic Basin is only 29% percent of normal (through 10/17) when compared to the climatological average from 1981-2010 and it is the 7th lowest since 1950. Elsewhere, the ACE across the northern hemisphere is only 58% of normal and global ACE is 62% of normal. (Source: Dr. Ryan Maue at Weather Bell Analytics; http://models.weatherbell.com/tropical.php)

Finally, another interesting stat with respect to hurricanes has to do with the fact that we are currently in the longest period since the Civil War Era without a major hurricane strike in the US (i.e., category 3, 4 or 5). The last major hurricane to strike the US was Hurricane Wilma during late October of that record-breaking year of 2005 - let’s hope this historic stretch continues. By the way, just as a point of comparison, in 1954 the US was hit by 3 major hurricanes in less than 10 weeks.

9:00 AM | Global sea ice update and the connection between the Atlantic Ocean and the Arctic

Discussion

The northern hemisphere sea ice areal extent has increased significantly from last year’s record low amount and is above four other recent years (2007, 2008, 2010, 2011), but it remains below normal for this time of year. Meanwhile, the southern hemisphere continues at above normal levels and recent measurements suggest it has reached the highest level in decades. On a global basis, sea ice areal extent is currently relatively close to normal with the northern hemisphere near its low point for the year (winter approaching) and southern hemisphere near its high (summer approaching).

Two distinct trend lines can be seen in the northern hemisphere sea ice areal extent dating back to the beginning of satellite era observations in 1979 and there seems to be a direct connection with an oceanic cycle in the north Atlantic involving sea surface temperatures. The Arctic region north of the Atlantic Ocean is open to the warmer waters from the south because of the way the ocean currents flow. These warmer waters can flow into the Arctic and prevent sea ice from forming in the North Atlantic. The northern Atlantic Ocean sea surface temperatures are tracked by meteorologists through an index called the Atlantic Multidecadal Oscillation (AMO) and the two distinct trend lines for northern hemisphere sea ice areal extent are quite well correlated with a flip in phases of the AMO in the mid 1990’s from negative (colder water) to positive (warmer water). Specifically, the northern hemisphere sea ice areal extent featured a general sideways trend at above normal levels from 1979 to the mid 1990’s and then, following that flip in the AMO, there has been an overall downward trend to the current below normal values. These oceanic cycles can last for two or three decades and I believe that when the northern Atlantic sea surface temperatures flip back to cooler-than-normal values – perhaps 5 or 10 years from now - the northern hemisphere sea ice areal extent will return to normal or above normal levels - much like it was before the mid 1990’s while the AMO was negative.

In addition to “areal extent”, “volume” is an important parameter to monitor with respect to sea ice to determine possible long-term climatic trends, but it is harder to measure. In fact, there are no Arctic-wide or Antarctic-wide measurements of the volume of sea ice, but it can be estimated for the Arctic using the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) developed at the University of Washington Applied Physics Laboratory/Polar Science Center. PIOMAS blends satellite-observed sea ice concentrations into model calculations to estimate sea ice thickness and volume and comparisons with submarine, mooring, and satellite observations help to increase the confidence of the model results. In general, the overall trends seen for the modeled sea ice volume in the northern hemisphere seem to correlate pretty well with the observed trends seen for areal extent dating back to the beginning of the satellite era. Namely, similar to sea ice areal extent, the volume features a general sideways trend at above normal levels from 1979 to the middle 1990’s and then a downward trend began at that time when the AMO flipped to a positive phase. We’ll continue to monitor all of this at "thesiweather.com" over the weeks and months to come as we head into the northern hemisphere winter season.

Video

httpv://youtu.be/VraJH6M08pg

11:30 AM | The sun has gone eerily quiet

Discussion

The main driver of all weather and climate, the entity which occupies 99.86% of all of the mass in our solar system, the great ball of fire in the sky – has gone eerily quiet. The sun is currently virtually spotless despite the fact that this is supposed to have been a period of elevated sunspot activity during the solar maximum of solar cycle 24.

We are currently over four years into Solar Cycle 24 and it continues to “underwhelm” and be on a pace that would make it the smallest sunspot cycle since Cycle 14 which peaked in February 1906. There is a growing feeling that, based on the recent inactivity, the peak may have already happened during the latter part of 2011 - much earlier than originally forecasted. Another theory suggests that there may be a “double-peak” solar maximum for this cycle which would mean there could be a sharp spike in sunspot activity still to come later this year or in 2014, but there certainly have been no signs of that in recent days.

Solar cycle 24 began after an unusually deep solar minimum that lasted from 2007 to 2009 which included more spotless days on the sun compared to any minimum in almost a century. While a weaker solar cycle does not rule out the threat for strong solar storms, it does suggest that they will occur less often than during the stronger and more active cycles. The increasingly likely outcome for a weak solar cycle continues the recent downward trend in sunspot cycle strength that began over twenty years ago with solar cycle 22. In addition, there are some solar scientists who are already predicting that the next cycle, 25, will be even weaker than the current one. According to some research studies, weak solar cycles with extended lengths may actually have a downward effect on global temperatures in the medium and longer range. Weak solar cycles tend to last longer than the strong ones. There have been historical periods with minimal sunspot activity that lasted for several decades such as from the mid 1600’s to the early 1700’s when the so-called “Maunder Minimum” occurred and this period was quite cold globally. We’ll continue to periodically report on the latest solar activity here at “thesiweather.com” to monitor any important changes that may unfold.

Video

httpv://youtu.be/r11ApCwhc-k