12:15 PM | The first hurricane of the Atlantic tropical season...likely headed towards Puerto Rico and Hispaniola...may reach its peak intensity during next 24 hours or so and then weaken

[Latest GOES satellite image of Hurricane Danny; courtesy NOAA/McIdas]

Friday 12:15 PM Discussion

Danny has become the first hurricane of the Atlantic Ocean tropical season and it has reached a strong category 2 status with sustained winds of 105 mph while moving WNW at 10 mph. This system started off earlier in the week as an “African-wave” moving from the east to the west pushed along by tropical trade winds. Danny strengthened noticeably in the overnight hours and its rather small eye has become better defined (see satellite image above).

While strengthening can continue over the next 24 hours or so – perhaps even allowing Danny to reach major hurricane category 3 status – there are signs that after that point in time some weakening is likely to take place. Currently, there is a weak trough over the western Atlantic and this should lift northward over the next couple of days allowing for a ridge to build westward and strengthen. As a result, Danny is likely to turn more westward in the near term and perhaps experience an increase in its forward speed. The current environment for Danny is that of light vertical wind shear, but as the ridge intensifies, there is likely to be increasing upper-level southwesterly flow and the overall vertical wind shear should increase after 24 hours or so. [Vertical wind shear can be defined as a change of wind direction with altitude where strong wind shear indicates significant wind direction changes in a given vertical column of air].

In addition, Danny is about to encounter an area of dry air which should inhibit its intensification along with the increasing vertical wind shear which is aided in part by El Nino conditions in the tropical Pacific Ocean. In fact, dry air from the Saharan Desert region of Africa extends all the way from the African coast to the Caribbean Sea. Danny, as indicated below by the arrow, is about to move into an area of drier air that originated over the Saharan Desert (dry Saharan air indicated by "yellows/oranges").

[Saharan air analysis; courtesy NOAA/CIMSS-University of Wisconsin]

Danny is expected to reach the Leeward Islands in about 3 days (Monday), near Puerto Rico in about 4 days (Tuesday) and then near the island of Hispaniola (Haiti/Dominican Republic) in about 5 days (Wednesday). Given the likely increase in vertical wind shear and its encounter with drier air, Danny may very well drop back to "weak hurricane" or even “tropical storm” status by the time it reaches Puerto Rico and Hispaniola. Looking down the road, another wave is moving off Africa's west coast and this tropical system could ultimately become more of a threat to the US than Danny (cloud mass at lower, bottom region of "Saharan air analysis" image). Stay tuned.

11:55 AM | Typhoon Soudelor to reach "super" status

[Close-up colorized IR image of Typhoon Soudelor; courtesy MTSAT]

[Full disk IR image of Typhoon Soudelor; courtesy MTSAT, University of Wisconsin]

Discussion

Sea surface temperatures in the western Pacific Ocean are running at warmer-than-normal levels and this combined with low wind shear is helping to fuel the intensification of Typhoon Soudelor - the strongest storm of 2015. Soudelor is likely to intensify rapidly over the next few days to rarely seen pressure levels and places like Taiwan and eastern China are keeping a close eye on it. The latest close-up colorized IR satellite image and full disk IR image (above) feature an impressive-looking eye with a well-balanced and symmetrical appearance to the overall storm. A computer forecast model called the Hurricane Weather Research and Forecast System (HWRF) is designed by NOAA to be specifically used for hurricanes and its operational version forecasts a minimum pressure of 908 millibars in 72-hours (plot below) which is equivalent to an amazing 26.81 inches (other models shown in the plot are somewhat weaker). The very latest European computer forecast model plows the storm directly into Taiwan late this week with a central pressure of 919 millibars (27.14 inches). Even if Soudelor begins to weaken prior to possible landfall in Taiwan and eastern China, it is still expected to be a significant typhoon and preparations are already being made for the storm from Shanghai to Taipei. [Click here for a video of the "close-up" view: http://www.ssd.noaa.gov/PS/TROP/floaters/13W/imagery/rbtop_lalo-animated.gif]

[Operational HWRF forecasts a minimum pressure of 908 millibars for Typhoon Soudelor in 72 hours; courtesy NOAA]

10:30 AM | Arctic sea ice showing great resiliency

Overview

There has been talk in the climate community over the past several years that the Arctic Ocean would be nearly ice-free by now, but sea ice in the Arctic region has actually shown great resiliency. Sea ice covers about 7% of the Earth’s surface and about 12% of the world’s oceans and forms mainly in the Earth’s polar regions (i.e., in the Northern Hemisphere’s Arctic Ocean and in the sea area around the Southern Hemisphere’s continent of Antarctica). While the Southern Hemisphere sea ice extent has been running consistently at above-normal levels in the past few years and often at record highs, the Northern Hemisphere has generally been at below-normal amounts. In this same time period; however, sea ice in the Arctic region has shown a great ability to recover which has confounded many global climate modelers and it has actually been in a general upward trend since reaching a low point in 2012 (example journal article on measured versus modeled discrepancies in sea ice data: http://www.hindawi.com/journals/amete/2015/481834/). Furthermore, in recent months the northern Atlantic Ocean has begun to show signs of a potential long-term temperature phase shift from warm-to-cold and this could very well lead to a significant further rebound in Arctic sea ice – perhaps eventually to the above-normal levels seen during the last cold phase.

[Sea surface temperature anomalies as of July 27, 2015; courtesy NOAA]

North Atlantic Sea Surface Temperature (SST) Change

The northern Atlantic Ocean switched sea surface temperature phases from cold-to-warm back in the mid 1990’s and this shift was directly correlated with the flipping of Arctic sea ice extent from above-normal to below-normal and it has generally been below-normal since that point in time. The sea surface temperature phase in the northern Atlantic Ocean is tracked by meteorologists with the Atlantic Multidecadal Oscillation (AMO) index and in recent months this number has been bouncing back-and-forth between negative (cold) and positive (warm) values suggesting a possible long-term phase change may indeed be taking place. An area of colder-than-normal sea surface temperatures (blue region in circled area) has expanded significantly in recent months across the northern Atlantic Ocean and temperatures in the Arctic region have run at normal-to-slightly below-normal levels (plot below, circled area; green line represents normal). [For more information on the possible Atlantic Ocean temperature phase shift: http://vencoreweather.com/2015/03/22/1230-pm-the-atlantic-ocean-is-showing-signs-of-a-possible-significant-long-term-shift-in-temperatures-from-warm-to-cold/].

Daily mean temperature and climate north of the 80th northern parallel, as a function of the day of year. Source: Danish Meteorological Institute (DMI) – Centre for Ocean and Ice; http://ocean.dmi.dk/arctic/meant80n.uk.php

Significant improvement in Arctic sea ice extent since 2012

One of the lowest points with respect to Arctic sea ice took place in the year 2012. During that year, Arctic sea ice bottomed out during the peak of the melting season (late summer) to levels not seen before in the satellite era (since 1979). Recent reports based on satellite observations, however, indicate the Arctic sea ice recovered noticeably in 2013 increasing by almost one-third – albeit from very low levels. For the last couple of months, Arctic sea ice has been running at levels higher than those seen during the past three years – although still at below-normal levels – and it has been running safely above the low point year of 2012 (“black” line in circled area below).

Source: Danish Meteorological Institute (DMI) – Centre for Ocean and Ice (sea ice extent 15% or greater)

Upward trend in Arctic sea ice volume since 2012

In addition to sea ice extent, an important climate indicator to monitor is sea ice volume as it depends on both ice thickness and extent. Arctic sea ice volume cannot currently be observed on a continuous basis as observations from satellites, submarines and field measurements are all limited in space and time. As a result, one of the best ways to estimate sea ice volume is through the usage of numerical models which utilize all available observations. One such computer model from the University of Washington is called the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS, Zhang and Rothrock, 2003) and it is showing an upward trend in Arctic sea ice volume since the low point was reached in 2012 following a long downtrend (circled area below). We’ll continue to monitor changes in coming months here at VencoreWeather.com with respect to the Arctic sea ice to see if the recovery from low levels continues and we’ll also watch the overall situation in the southern hemisphere.

Arctic sea ice volume from the University of Washington’s PIOMAS numerical model (Note – this model output data is updated on a monthly basis, details on the PIOMAS model are available at http://psc.apl.washington.edu/research/projects/arctic-sea-ice-volume-anomaly.

Paul Dorian

Vencore, Inc.

12:20 PM | An update on El Nino - it continues to strengthen and could end up rivaling some of the strongest events in recent history

Overview

El Nino conditions developed last year in the equatorial part of the Pacific Ocean and they have intensified significantly in the past few months. In fact, it appears that this El Nino may end up rivaling in strength the strongest such events in recent history which took place in 1972-1973, 1982-1983 and 1997-1998. This type of natural phenomenon features warmer-than-normal sea surface temperatures in the tropical Pacific Ocean while its counterpart called La Nina is correlated with colder-than-normal waters. Given the fact that the Pacific Ocean is by far the world’s largest, an El Nino can have significant ramifications on weather and climate in many parts of the world; especially, one that is strengthening into a such a strong event.

In the past 60 days, warmer-than-normal sea surface temperature anomalies (orange area) have spread westward from the west coast of South America into the central equatorial Pacific Ocean. Computer forecast models are in general agreement that this strengthening trend in the El Nino will continue for the next few months perhaps then followed by some weakening at the end of the year or early in 2016. Meanwhile, as El Nino intensifies in the equatorial Pacific Ocean, colder-than-normal sea surface temperatures have expanded significantly in the northwestern part of the Pacific Ocean as well as across the northern Atlantic Ocean (not shown) and this, in many ways, is equally as impressive as to what is occurring in the tropics.

Ramifications of a strong El Nino

The tropical region of the Pacific Ocean is perhaps the most important section of any ocean across the world in terms of weather and climate and strong El Nino conditions can have the following ramifications around the globe:

1) An El Nino in the summertime typically results in below-normal activity in the tropical Atlantic Ocean as it tends to generate stronger-than-normal upper level winds which act to suppress "African-wave" storm development. So far, the Atlantic tropical season has underperformed and that overall trend should continue.

2) An El Nino in the summertime typically results in normal-to-cooler-than normal temperatures across the Midwest and Northeast US. In fact, temperatures through the halfway point of summer have been relatively close-to-normal in the Mid-Atlantic’s I-95 corridor and longer term forecasts suggests a continuation of relatively moderate conditions well into the month of August.

[Note – both items 1 and 2 are described in detail in Vencore Weather’s 2015 Tropical Outlook: http://vencoreweather.com/2015/05/05/1000-am-2015-tropical-and-mid-atlantic-summertime-outlooks/]

3) An El Nino is likely to result in more rainfall compared to normal in the Southwest US which should alleviate drought conditions in California during the next 6-12 months or so. In fact, a significant rain event pounded southern California last weekend as the remains of a Pacific Ocean tropical system – aided by El Nino conditions - pushed into that region of the country.

[Oceanic Nino Index (ONI) values since 2000 (red=El Nino, blue=La Nina, black=neutral); courtesy NOAA]

4) An El Nino is likely to cause a spike in global temperatures. The table (above) lists the monthly “Oceanic Nino Index” since the year 2000 with El Nino events in red and La Nina conditions in blue. The last two El Nino events were rather moderate by comparison to the current one and both resulted in a short-term spike in global temperatures.

In the plot below, global temperature anomalies shown back to the year 2005 are in a jagged, but generally downward trend (data courtesy Ryan Maue, WeatherBell Analytics, Inc.). The circled areas (below) show the global temperature spikes associated with the most recent two El Nino events that occurred in 2006-2007 and 2009-2010. An important finding also revealed by this plot is that each of these two "El-Nino-induced" spikes was followed quickly by a sharp drop in global temperatures once the El Nino conditions subsided - and it is quite likely that the same thing will occur following this current El Nino.

[Global temperature anomalies from 2005 through today using NOAA's CFSR/CVSv2 data; data courtesy Ryan Maue at WeatherBell Analytics, weatherbell.com]

12:00 PM | Possible early clues for another snowy and cold winter in the Northeast US

Overview

The summer is just days old, but it is never too early to look for clues regarding possible weather conditions for the upcoming winter season. In reality, the long descent towards winter 2015-2016 has just begun as far as the sun is concerned with daylight hours now entering its gradual diminishing phase in this part of the world. There are, in fact, two regions in the all-important Pacific Ocean that may be providing us with signs as to what kind of weather we can expect here in the Northeast U.S. during the upcoming winter season.

One region is in the equatorial Pacific Ocean where El Niño conditions are currently quite concentrated near the northwest coast of South America. These warmer-than-normal sea surface temperatures, however, actually stretch in a general west-to-east fashion along the equator from the northwest coast of South America to the central Pacific Ocean (indicated below by arrow). Another area of interest lies across the northern Pacific Ocean where a couplet of warm and cold sea surface temperature (SST) anomalies currently exists (circled area). These two regions in the Pacific Ocean may very well be indications that we’re headed for another snowy and cold winter in the Northeast U.S.

[Recent SST global anomaly map; courtesy NOAA]

JAMSTEC SST anomaly forecast for the upcoming winter season

There are many reasons to believe that the current El Niño in the tropical Pacific Ocean will not only last into the latter part of 2015, but will actually strengthen throughout the summer months before most likely beginning a weakening phase near the end of 2015 or early in 2016 (for more info on this unfolding El Niño: http://vencoreweather.com/2015/05/14/915-am-strengthening-el-nino-in-the-tropical-pacific-ocean-to-have-global-ramifications/). Not only is the strength of an El Niño an important factor in terms of its potential impact on Northeast U.S. winter weather, but its location is critical as well. A reliable computer forecast model from Japan’s Agency for Marine Earth Science and Technology (JAMSTEC) predicts El Niño will shift from near the west coast of South America to the central Pacific Ocean by next winter (indicated below by arrow). This particular location for an El Niño in the central tropical Pacific Ocean has been correlated with snowy winters in the Northeast U.S. – most recently during the winters of 2002-2003 and 2009-2010.

[JAMSTEC predicted SST anomalies for winter 2015-2016; courtesy Japan’s Agency for Marine Earth Science and Technology]

In addition, the JAMSTEC SST anomaly prediction for next winter suggests there will be a continuation of the current couplet of warmer and colder-than-normal water in the northern Pacific Ocean (circled area above). The warmer-than-normal water south of the Alaska coastline has, in fact, persisted relentlessly for the past couple of years and has contributed to colder-than normal weather here in the Northeast US during the last couple of winters.

Consequences of the predicted SST anomaly pattern in the Pacific Ocean

During winter seasons, the sea surface temperature anomaly couplet in the northern Pacific Ocean generally has led to a persistent upper-level ridge of high pressure along the west coast of the US and Canada and an upper-level low in the north-central Pacific Ocean – usually an atmospheric combination that promotes colder-than-normal weather around here by allowing for the transport of Arctic air from northern Canada into the northern US. Meanwhile, an El Niño focused in the central Pacific Ocean often has been correlated with above-normal snowfall in the Northeast U.S. – most recently during the winters of 2003-2003 and 2009-2010. One of the possible reasons for this outcome is that warmer-than-normal sea surface temperatures in the tropical Pacific Ocean during wintertime tend to produce abundant moisture levels in the southern branch of the upper-level jet stream which is often a key player in Northeast U.S snowstorms.

Comparison with two snowy winters (2002-2003, 2009-2010)

Some rather amazing similarities exist between the JAMSTEC forecasted sea surface temperature anomalies for the upcoming winter season and the actual anomalies that took place during the snowy winters of 2002-2003 and 2009-2010. Not only do they both feature "centrally-based" El Niño’s in the tropical Pacific Ocean (indicated below by arrow), but they both have a noticeable SST couplet with a warm anomaly pattern tucked in near the Alaska coastline and a colder-than-normal region just to its southwest (circled area).

[Actual SST anomaly pattern during the winter seasons of 2002-2003, 2009-2010; courtesy NOAA]

What could change this preliminary snowy and cold winter outlook?

One way meteorologists track the strength of an El Niño is through an “oceanic Niño” index value. The latest 3-month running average of this index has risen from 0.2 in August/September/October of last year to 0.7 in March/April/May in this year. Generally, if this index rises above 2.0, the El Niño is considered to be in the “super strong” category. The last time a “super strong” El Niño actually took place was during 1997-1998, but there are some important differences between today's overall setup in the tropical Pacific Ocean and the situation back in the late 1990s. Specifically, there is a ring of warm water today surrounding much of the Australian continent and this usually has an inhibiting effect on the strength and longevity of an El Nino. If, however, a super strong El Niño were to develop by next winter across the central and eastern tropical Pacific Ocean, then this could very well flood much of the country including the Northeast U.S. with warmer-than-normal weather conditions. While I do expect this El Niño to become fairly strong – perhaps in the 1.5–2.0 index value range – I don't think it’ll rise to “super strong” levels seen last in the 1997-1998 time period and I also believe it’ll be focused in the central part of the tropical Pacific Ocean by next winter.

Concluding remarks

We’ll continue to monitor both the strength and location of the strengthening El Niño in the tropical Pacific Ocean over the next few months here at “vencoreweather.com”. As of right now, there are reasons to believe that there will be a centrally-based, moderately-strong El Niño as we head into the winter months of 2015-2016 along with a couplet of warm and cold anomaly water in the northern Pacific Ocean – all of which could lead to another snow-filled and cold winter in the Northeast U.S.

Paul Dorian

Vencore, Inc.

9:15 AM | Strengthening El Nino in the tropical Pacific Ocean to have global ramifications

Discussion

Overview

El Nino conditions began to develop last year in the equatorial tropical Pacific Ocean and all indications suggest rapid strengthening is now taking place. This type of natural phenomenon features warmer-than-normal sea surface temperatures in the tropical Pacific Ocean with its counterpart, La Nina, associated with colder-than-normal waters. Given the fact that the Pacific is by far the world’s largest ocean, an El Nino in its equatorial region can have significant ramifications on weather and climate in many parts of the world; especially, one that is strengthening rapidly and sustained.

In the past 30 days, sea surface temperature anomalies have changed noticeably off the west coast of South America as rapid warming has taken place (orange area in comparison map above). Computer forecast models are in general agreement that this strengthening trend will continue for the next few months perhaps followed by weakening in the overall El Nino later this year.

Ramifications of a strengthening El Nino

The tropical Pacific Ocean is perhaps the most important part of any ocean across the world and strengthening El Nino conditions can have the following ramifications around the globe:

1) An El Nino during the summertime typically results in below-normal activity in the tropical Atlantic Ocean as it tends to generate stronger-than-normal upper level winds which act to suppress "African-wave" storm development.

2) An El Nino during the summertime typically results in normal-to-cooler-than normal temperatures across the Midwest and Northeast US.

[Note – both items 1 and 2 are described in detail in Vencore Weather’s 2015 Tropical Outlook: http://vencoreweather.com/2015/05/05/1000-am-2015-tropical-and-mid-atlantic-summertime-outlooks/]

3) An El Nino is likely to result in more rainfall compared to normal in the Southwest US which could alleviate drought conditions in California during the next 6-12 months or so.

[Oceanic Nino Index (ONI) values for past 10 years (red=El Nino, blue=La Nina, black=neutral); courtesy NOAA]

4) Finally, an El Nino is likely to cause a spike in global temperatures. The table above lists the monthly “Oceanic Nino Index” for the past 10 years and there have been two El Nino episodes (arrow regions) in which an (red) index value of 1.0 was reached (moderate strength): "late 2006" and "late 2009 into early 2010". While I do not believe this El Nino will develop to "super" strong levels (i.e., index values of 2.5 or higher), I do believe it will strengthen to strong levels (i.e., 1.5 to 1.9) during the next few months from its current reading of 0.6 before weakening likely begins late in the year or early in 2016.

While there has been a jagged, and generally downward trend in global temperatures during the past 10 years according to NOAA's CFSR/CVSv2 data, in those months associated with these two El Nino episodes global temperatures actually spiked. The circled areas in the plot below show the “El Nino-induced” spikes in global temperatures associated with the "late 2006" and "late 2009/early 2010" moderate-strength El Nino events (data courtesy Ryan Maue at Weather Bell Analytics, NOAA). In addition, an important point to note is that in both of these El Nino events, global temperatures actually dropped sharply shortly after El Nino conditions subsided (circled regions).

[Global temperature anomalies from 2005 through 2014 using NOAA's CFSR/CVSv2 data; courtesy Ryan Maue at Weather Bell Analytics, weatherbell.com]

10:00 AM | 2015 Tropical and Mid-Atlantic Summertime Outlooks

Discussion

Overall Summary

The overall numbers are likely to be down this year in terms of the number of Atlantic Basin tropical storms, but the sea surface temperature pattern in the western Atlantic and Gulf of Mexico makes the U.S. east coast vulnerable to “home-grown” tropical hits. The major factors involved with this year’s tropical outlook include a strengthening El Nino in the central equatorial Pacific, colder-than-normal waters off of the west coast of Africa, and pockets of warmer-than-normal temperatures in the Gulf of Mexico and also just off the US east coast. As a result, there are likely to be fewer-than-normal “African-wave” type tropical systems that travel long distances across the tropical Atlantic this season and more in the way of “home-grown” type systems that develop much closer to the U.S. Typically, the “African-wave” type storm plays an important role during the peak months of the tropical season (August and September) while “home-grown” systems can be important early and late in a given tropical season.

In a normal Atlantic Basin tropical season, there are about 12 named storms with 6 or 7 reaching hurricane status and only 2 or 3 actually reaching major status (i.e., category 3, 4 or 5). This year there may be more on the order of 8-10 named storms with 3-5 reaching hurricane status, but despite these expected slightly below-normal overall numbers, the U.S. could actually see more tropical activity than normal due to the sea surface temperature pattern in the western Atlantic and Gulf of Mexico.

One final note of interest, amazingly and fortunately, the US mainland has not been struck by a major hurricane (i.e. category 3 or higher) since Hurricane Wilma in October 2005. Although the landfall record gets muddy before the early 20th century, this is the first time since hurricane record-keeping began in 1851 that the United States has gone so long without at least a category 3 landfall. The previous streak was eight years, from 1861 to 1868.

El Nino in the tropical Pacific Ocean

What goes on in the tropical Pacific Ocean does indeed have an effect on the tropical Atlantic Ocean. El Nino, which refers to warmer-than-normal waters in the equatorial Pacific Ocean, affects global weather patterns and it tends to produce faster-than-usual high-altitude winds over the tropical Atlantic Ocean. This increase in the upper atmospheric winds over the tropical Atlantic Ocean is usually an inhibiting factor for tropical storm formation in the Atlantic Basin as it tends to “rip apart” developing storms. Currently, there are numerous signs for strengthening of the current El Nino in the tropical Pacific Ocean over the next few months and this should inhibit storm formation in the tropical Atlantic Ocean. Specifically, numerous computer forecast models support the idea that the current relatively weak equatorial El Nino strengthens this summer into moderately-strong status.

[Computer model forecasts of El Nino; courtesy IRI, Columbia University, NOAA]

Atlantic Ocean, Gulf of Mexico sea surface temperature patterns

The main breeding grounds for Atlantic Ocean tropical systems are in the region between the west coast of Africa to the Caribbean Sea and the Gulf of Mexico. Above normal sea surface temperatures in this region generally help to intensify tropical waves that come off of the west coast of Africa and move westward in the trade winds. Similar to last year, there is a pocket of colder-than-normal sea surface temperatures off the west coast of Africa and this should inhibit the formation of tropical storms in that part of the tropical Atlantic Ocean. On the other hand, there are warmer-than-normal pockets of water just off the U.S. east coast and across much of the Gulf of Mexico, and these anomalous regions should aid in the development of “home-grown” type storms in nearby locations such as the Caribbean Sea, Gulf of Mexico or just off the Southeast U.S. coastline. [Sea surface temperature anomaly pattern (orange, yellow = warmer-than-normal; courtesy NOAA]

Mid-Atlantic Summer Outlook

I believe there is little chance for a hot, dry summer in the Mid-Atlantic region and the most likely scenario is for near normal rainfall amounts with a slight leaning towards the cool side of normal when it comes to temperatures in the June, July, August time period The strengthening of El Nino in the tropical Pacific Ocean will play a role in our summertime weather pattern which usually leads to cooler-than-normal conditions, and there are two other factors that should turn out to be meaningful. First, the record-breaking Great Lakes ice cover extent during the past winter season is generally a useful predictor of cooler-than-normal temperatures in the Mid-Atlantic region during the subsequent summer season. In fact, Great Lakes ice cover extent as of late April was 27% - the highest ever so late in the season – and there was still more than 5% coverage in early May across Lake Superior. This finding of generally cooler-than-normal summers in the Mid-Atlantic region following high ice cover winters in the Great Lakes region is not necessarily because of the actual ice cover, but rather due to the overall - and likely still on-going - weather pattern that created the anomalous ice cover in the first place and typically persists beyond the winter season. In addition, soil moisture content is relatively normal around here in the Mid-Atlantic region as we head into the month of May thanks to the snowy winter and recent spring rains. Normal-to-high soil moisture content tends to significantly reduce chances for summertime drought and excessive heat.

Paul Dorian

Vencore, Inc.

Extended Video Discussion

httpv://youtu.be/x8QZ3wxVGJM

8:45 AM | The sun is now virtually blank during the weakest solar cycle in more than a century

[Current image of the sun with virtually blank conditions; courtesy NASA/SDO]

Discussion

Overview

The sun is almost completely blank. 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 quiet again during what is likely to be the weakest sunspot cycle in more than a century. The sun's X-ray output has flatlined in recent days and NOAA forecasters estimate a scant 1% chance of strong flares in the next 24 hours. Not since cycle 14 peaked in February 1906 has there been a solar cycle with fewer sunspots. We are currently more than six years into Solar Cycle 24 and the current nearly blank sun may signal the end of the solar maximum phase. 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.

Solar maximum

The sun goes through a natural solar cycle approximately every 11 years. The cycle is marked by the increase and decrease of sunspots which are visible dark regions on the sun’s surface and cooler than surroundings. The greatest number of sunspots in any given solar cycle is designated as the “solar maximum" and the lowest number is referred to as the “solar minimum” phase.  The smoothed sunspot number (plot below) for solar cycle 24 reached a peak of 81.9 in April 2014 and it is looking increasingly likely that this spike will be considered to be the solar maximum for this cycle. This second peak in the cycle surpassed the level of an earlier peak that reached 66.9 in February 2012. Many solar cycles are double peaked; however, this is the first one in which the second peak in sunspot number was larger than the first peak. Going back to 1755, there have been only a few solar cycles in the previous 23 that have had a lower number of sunspots during its maximum phase.

[Sunspot numbers for the prior solar cycle (#23) and the current solar cycle (#24) with its two peaks highlighted; courtesy Hathaway, NASA/ARC]

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. By all Earth-based measures of geomagnetic and geoeffective solar activity, this cycle has been extremely quiet. However, while a weak solar cycle does suggest strong solar storms will occur less often than during stronger and more active cycles, it does not rule them out entirely. In fact, the famous "superstorm" Carrington Event of 1859 occurred during a weak solar cycle (#10) [http://vencoreweather.com/2014/09/02/300-pm-the-carrington-event-of-1859-a-solar-superstorm-that-took-places-155-years-ago/]. In addition, there is some evidence that most large events such as strong solar flares and significant geomagnetic storms tend to occur in the declining phase of the solar cycle. In other words, there is still a chance for significant solar activity in the months and years ahead.

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 very prolonged period of time (several decades) can have a cooling 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 (below). Both of these historical periods coincided with colder-than-normal global temperatures in an era now referred to by many scientists 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.

[400 years of sunspots with "minimum" periods highlighted; map courtesy wikipedia]

Outlook

The increasingly likely outcome for another historically weak solar cycle continues the recent downward trend in sunspot cycle strength that began over twenty years ago during solar cycle 22. If this trend continues for the next few cycles, then there would likely be increasing talk of another “grand minimum” for the sun which is an extended period of low solar activity. Some solar scientists are already predicting that the next solar cycle, #25, will be even weaker than this current one. However, it is just too early for high confidence in those predictions since many 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.

Paul Dorian

Vencore, Inc.

9:20 AM | Chile’s Calbuco Volcano Erupts Sending Massive Ash Plume Into Sky

[Calbuco as seen from the nearby city of Puerto Montt (southern Chile)]

Discussion

There was a massive double eruption on Wednesday by Chile’s Calbuco volcano – its first activity in 42 years - and it sent a massive ash plume high up into the sky (photo above from nearby town). This eruption could have an impact on worldwide climate depending on its duration and ultimate extent of the ash plume into high-levels of the atmosphere. Past history has shown that large volcanic eruptions can generate a year or so of global cooling. When enough ash and dust is ejected into the lower stratosphere, these particles then spread across the globe due by upper-level wind currents. These increased aerosols in the upper atmosphere can then act to reflect the incoming solar radiation back into space rather than allowing penetration into the troposphere and the warming the surface of the earth. The term that is often used that describes a period of time that results in cooling temperatures following a major volcanic eruption is “Volcanic Winter”. The most famous recent volcanic eruption that resulted in "Volcanic Winter" was Mount Pinatubo (Philippines) in 1991 which resulted in reduced global temperatures for the following 2-3 years. Way back in 1883, the explosion of Krakatoa (Indonesia) created volcanic winter-like conditions for the subsequent four years with unusual year-round cold and record snowfalls worldwide.

[Enhanced IR satellite image of the “volcano-produced” cloud]

The volcano is located about 600 miles south of Santiago, and just a few miles from the city of Puerto Varas. Evacuations were ordered for a 12-mile radius around the volcano. The eruptions happened after a series of earthquakes, the Chilean Interior Ministry reported. The column of smoke and ash rose more than 9 miles into the atmosphere and can be clearly seen in an enhanced IR satellite image (middle). Pyrocumulus clouds form when intense heat at the ground causes air to rise rapidly such as what can occur during volcanic eruptions or wildfires. In the case of exceptionally strong updrafts, pyrocumulonimbus clouds are possible, which can produce rainfall and lightning (bottom photo). Dust and ash particles that get thrown up into the atmosphere can separate into positively and negatively charged groups. Lightning can result when this charge separation becomes too great for air to resist the flow of electricity. The volcano may soon start oozing lava and cause the melting of ice, and ultimately floods, and a third major eruption is possible in the very near term.

[Lightning captured in photos on Wednesday night]

2:30 PM | Global sea ice areal extent running at slightly above-normal levels

[Yellow line represents the year-to-date Southern Hemisphere sea ice areal extent compared to all other years going back to 1979; data courtesy University of Illinois "cryosphere"; NOAA/NCEP Snow and Ice Data Center]

Discussion

Overall Summary

Southern Hemisphere sea ice areal extent continues to run near record high levels in the satellite data era (circled area above) for this time of year in records going back to 1979 whereas the Northern Hemisphere continues to run near record low levels in the same comparison time period (circled area on bottom plot). Overall, the global sea ice areal extent is currently running slightly above-normal at just under half a million square kilometers above the 1979-2008 mean (below).

[red line represents global sea ice areal extent compared to the 1979-2008 normal as represented by the “zero” line; data courtesy University of Illinois "cryosphere"; NOAA/NCEP Snow and Ice Data Center]

Southern Hemisphere Sea Ice

The rather remarkable period of consistently higher-than-normal sea ice areal extent in this part of the world actually began a few years ago. Back in 2011, the southern hemisphere sea ice areal extent was still at below-normal levels, but it has surged in recent years to the current 1.2 million square kilometers above the 1979-2008 mean.

Northern Hemisphere Sea Ice

The northern hemisphere sea ice areal extent is still below-normal relative to all years going back to 1979 although it is well above the lowest point set during 2012 and even above levels seen earlier this year. The northern hemisphere sea ice areal extent is currently 0.8 million square kilometers below-normal using the base period of 1979-2008 for comparison. The northern hemisphere sea ice areal extent has leveled off in the past 10 years or so at below-normal levels after dropping consistently from the mid 1990’s to the middle of the last decade. In the time period before the mid 1990’s, the sea ice areal extent was generally above-normal dating back to 1979.

The directional shift in the sea ice areal extent trendline that developed during the mid 1990’s in the northern hemisphere 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, Atlantic Ocean sea surface temperature anomalies play a critical role in the overall northern hemisphere sea ice areal extent. The AMO index flipped in phase during the mid 1990’s from negative (cold) to positive (warm) and the sea ice areal extent trendline changed direction right around that point in time.

The Atlantic Ocean is just recently showing signs of a long-term temperature phase shift back to cold and if that trend continues over the next couple of years then the northern hemisphere sea ice areal extent is quite likely to return to the above-normal levels seen prior to the mid 1990’s. (Click here for more information on the potential significant temperature phase shift in the Atlantic Ocean: http://vencoreweather.com/2015/03/22/1230-pm-the-atlantic-ocean-is-showing-signs-of-a-possible-significant-long-term-shift-in-temperatures-from-warm-to-cold/).

[Yellow line represents the year-to-date Northern Hemisphere sea ice areal extent compared to all other years going back to 1979; data courtesy University of Illinois "cryosphere"; NOAA/NCEP Snow and Ice Data Center]

Paul Dorian

Vencore, Inc.