1:00 PM | Superstorm about to impact the Bering Strait and it will have ramifications on our weather

[Depiction of the forecasted wind field associated with this superstorm near Alaska; courtesy earth.nullschool.net]

Discussion

One of the most intense storms ever is about to move over the Bering Sea and it will have an impact on our weather in the eastern US in coming days. The Bering Sea is one of the stormiest parts of our planet, but it has rarely seen a storm like this and there is a chance that it could feature atmospheric pressure not seen this low in many decades in this part of the world.

Computer forecast models have been signaling for days that the remains of Typhoon Nuri will undergo a transition over the next few days into an extratropical storm as it moves away from Japan. As it does, unusually strong upper-levels winds across the North Pacific will help to intensify the system in a dramatic fashion – perhaps from around 970 millibars today to 925 millibars by tomorrow night. In fact, if it bottoms out at 925 millibars tomorrow night then it would tie the record for the lowest pressure ever recorded in the Bering Sea. The current record holder is 925 millibars and was set in October 1977 (in Dutch Harbor, Alaska). Note- as a point of reference, the lowest pressure recorded with Hurricane Sandy was 940 millibars. The storm will bring howling winds of up to 80 mph or so to the Aleutian Island chain and to the western part of the Alaskan mainland. Seas are forecast to build to at least 50 feet in the southwest Aleutians and perhaps even higher than that in the Bering Strait.

As far as possible ramifications on our weather…many times we’ve talked about “teleconnections” here at "VecnoreWeather.com" in which an event on one part of the world has an effect on another part of the world several days later. Indeed, this deep trough of low pressure developing in the Northern Pacific will likely translate downstream into a deep trough across the central and eastern US in coming days. In fact, it appears the reincarnation of Typhoon Nuri and some other atmospheric factors will lead to multiple rounds of Arctic air outbreaks into the Midwest and eastern US during the remainder of the month of November. One such major cold air outbreak is destined to reach the Mid-Atlantic region around Wednesday of next week.

11:30 AM | *Major cold wave invades the nation next week as overall weather pattern looks increasingly winter-like*

[Arctic Oscillation index: actual (black), forecast (red); courtesy NOAA]

Discussion

A couple of weeks ago, Vencore Weather put out the 2014-2015 Winter Outlook calling for a cold and snowy winter in the Mid-Atlantic region with a quick start including some notable cold and snow in December - well that last part of the winter outlook may just have to be revised slightly as the unfolding weather pattern could actually bring the real start of winter to this month rather than waiting for December.

To begin with, the Arctic Oscillation (AO) index which was highlighted in the Winter Outlook discussion is about to tank once again into deep negative territory which is suggestive of “high-latitude blocking” in the upper atmosphere of the higher latitudes and this usually is followed by Arctic air outbreaks into the northern US. Indeed, blocking in the higher latitudes will force an Arctic air mass to plunge into the mid-section of the country by next Tuesday and that impressive major cold air outbreak will likely reach the Mid-Atlantic region at mid-week. Next week’s early season Arctic air outbreak will be backed up by a monster high pressure system of 1040 millibars or higher and has the potential to produce record-breaking cold in much of the eastern half of the nation.

In addition to the AO, another important factor for our potential winter weather is the snowpack across Eurasia and the entire northern hemisphere as we approach the winter season. Indeed, at the end of October, the snowpack levels were quite impressive in our usual cold air source regions. Statistics gathered by the Rutgers Snow Lab in New Jersey show that the end-of-October snowcover is the 3rd highest in the last 47 years for the northern hemisphere and 2nd highest across Eurasia in that same time period. All of this bodes well for cold and snow in the northeastern US during the upcoming winter as described in detail in the Winter Outlook discussion. The plot below displays the northern hemisphere snowcover as of November 2nd for 2014 (right) and 2007 (left) - notice the significantly higher amounts of snow throughout Eurasia (white area) and even on this side of the north pole at this crucial time of year heading into the winter season.

[Northern hemisphere snowcover comparison for 2007 and 2014; data courtesy University of Illinois "cryosphere"]

2014-2015 Winter Outlook: http://vencoreweather.com/2014/10/15/1200-pm-2014-2015-winter-outlook-by-vencore-weather-looks-cold-and-snowy-for-the-mid-atlantic-region/

10:00 AM | 2014 - another down year in the US for tornadoes, hurricanes, extreme heat, wildfires and drought

Discussion

Overview Whether you’re talking about tornadoes, hurricanes, extreme heat, wildfires or drought, there is good news this year in that similar to last year, these extreme weather-related events are down in the U.S. compared to normal and, in the case of land falling major hurricanes, to historically quiet levels.

Tornadoes To begin with, the number of tornadoes in the US this year is on pace to be one of the lowest totals in the last ten years and well below the 9-year average (2005-2013) of 1478. The table below lists the number of tornadoes in the US for this year (preliminary count through 11/03) and full-year totals going back to 2005 [Data source: NOAA, http://www.spc.noaa.gov/climo/online/monthly/newm.html; http://www.spc.noaa.gov/wcm/]

Hurricanes As far as hurricanes are concerned and keeping in mind that the Atlantic Basin tropical season isn't quite over yet, the 2014 hurricane season has generally been a quiet one for the continental U.S. and below normal for the Atlantic Basin as a whole. As of November 3rd, there have been eight named storms this year in the Atlantic Basin - Arthur, Bertha, Cristobal, Dolly, Edouard, Fay, Gonzalo and Hanna. Six of these storms became hurricanes and two reached major hurricane status (category 3 or higher), but only Arthur impacted the continental US (Outer Banks of North Carolina). In terms of Accumulated Cyclone Energy, or ACE, this tropical season in the Atlantic Basin is only 67% of normal when using the 1981-2010 time period for comparison (Data source: Dr. Ryan Maue at Weather Bell Analytics; http://models.weatherbell.com/tropical.php). ACE is a commonly-used metric for activity because it is not dependent on exact numbers of named storms or hurricanes, but rather is based on both the intensity and longevity of all tropical storms and hurricanes (so a long-lived tropical storm could contribute as much ACE as a short-lived storm that reached hurricane intensity).

An interesting stat with respect to US hurricanes has to do with the fact that we are currently in the longest period since records began 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 the record-breaking year of 2005 - let’s hope this historic stretch continues. October 24th marked the 9th anniversary of the last major hurricane hit in the US, the last one being Wilma in the southwestern part of Florida. Florida has, in fact, quite amazingly now gone through their longest stretch ever without a hurricane of any kind – nine years as of October 24th – with the next longest streak in records dating back to 1851 being just five seasons from 1980-1984. In 2004 and 2005 alone, seven hurricanes hit Florida (Charley, Frances, Jeanne, and Ivan in 2004; Dennis, Katrina, and Wilma in 2005).

By the way, just as another point of comparison, in 1954 the US was hit by 3 major hurricanes in less than 10 weeks.

[Running 9 year mean in Florida]

Extreme Heat In addition to tornadoes and hurricanes, extreme heat is also down across the US this year when looking at frequency of 90 degrees days at all of the US Historical Climate Network (HCN) stations going back to the late 1800’s and this continues a long-term downward trend since the 1930’s. In fact, the percentage of US HCN stations to reach 90 degrees so far this year (through 10/24) has been the smallest on record. The most widespread heat occurred in 1931, when more than 98% of stations reached 90 degrees.

(Data source: NOAA, USHCN reporting stations; Steve Goddard, http://stevengoddard.wordpress.com/2014/10/25/us-having-its-coolest-year-on-record/ )

This year also continues a downward trend in the frequency of 100 degree days since the 1930’s as seen in the chart below. The five summers with the highest number of 100 degree days across the US are as follows: 1936, 1934, 1954, 1980 and 1930.

(Data source: NOAA, US HCN reporting stations; Steve Goddard)

Wildfires As far as wildfires are concerned, the amount of acres burned across the US was the lowest in the last eleven years through October 10th and the number of wildfires was the second lowest in that same time period – both well below the 2004-2013 average (table below).

(Data source: National Interagency Fire Center; http://www.nifc.gov/fireInfo/nfn.htm, http://www.nifc.gov/)

Drought Finally, despite the fact that much of California is suffering through severe drought, 63% of the country had no drought conditions as of October 28th and this is even higher than one year ago at this same time when about 48% of the country had no drought conditions (data source: http://droughtmonitor.unl.edu/Home/TabularStatistics.aspx; Roger Pielke, Jr). This actually continues a longer-term trend which shows a rather benign look to the Palmer Drought Severity Index in the last several years across the contiguous US (values generally between +1 and -1 since around 2001). The most severe drought conditions in the contiguous US occurred during the middle 1930's and then again in the middle 1950's when the Palmer Drought Severity Index dropped below -3.

Paul Dorian/Meteorologist VencoreWeather.com on Facebook, Twitter and liveweatherblogs.com paul.b.dorian@vencore.com

9:30 AM | Some amazing early season snow and cold

[Record or near record lows from yesterday and this morning; data courtesy coolwx.com]

Discussion

Heavy snow fell this weekend throughout the Great Smoky Mountains National Park which straddles the border region between Tennessee and North Carolina with up to nearly two feet reported in some of the highest elevation locations (e.g., 22 inches at Mt LeConte, TN). Heavy snow was also reported on sections of the Blue-Ridge Parkway connecting the Shenandoah National Park in southwestern Virginia to the Great Smoky Mountains National Park. Up to six inches of snow fell around Asheville, North Carolina while 3 inches were measured in Boone, North Carolina. Seven inches fell near Marshall, North Carolina (elevation 2280 feet) and up to 3 inches blanketed Bluefield, West Virginia.

Perhaps the most amazing feature about this weekend’s early season snow and cold was that accumulating snow fell in lower elevation locations across South Carolina and even was seen all the way to the coastline where Charleston saw its earliest snow on record. Columbia, South Carolina recorded its earliest snowfall ever (see picture below) with as much as 4.5 inches measured just southwest of the capital city. There have been only two other Novembers since the 1800s with snow accumulation in the city according to the National Weather Service. The previous benchmark for earliest snowfall in Columbia, SC was November 9, 1913.

[Snow-covered Columbia, South Carolina]

As the powerful storm that contributed to all of this early season snow and cold exited off to the northeast late yesterday, significant snow fell throughout much of Maine with a foot measured at Bangor and there was even some small snow accumulation in and around the Boston metro region. Bangor (12 inches) and Caribou (10.1 inches), Maine both set their record earliest double-digit snowfall days, besting records from Nov. 15, 1962 and Nov. 20, 1945, respectively, according to the National Weather Service office in Caribou.

In addition to the snow, cold was record-breaking in many southeastern US locations this weekend and into this morning. The plot above displays the widespread record or near record low temperature locations (blue circled regions) from yesterday morning and this morning (data courtesy coolwx.com). Some examples of record-setting cold on Sunday included Macon, Georgia at 29 degrees, Vero Beach, Florida at 41 degrees and Tampa, Florida recorded its lowest high temperature for the date at 67 degrees breaking a record held there since 1895. More record lows were set this morning in the Southeast US including Ocala, Florida at 37 degrees.

12:00 PM | 2014-2015 Winter Outlook by Vencore Weather...looks cold and snowy for the Mid-Atlantic region

Discussion

Looks like the Mid-Atlantic region - and much of the eastern half of the nation - is going to experience another cold and snowy winter…

Overview Last winter, much of the eastern half of the nation including the Mid-Atlantic region suffered through colder-than-normal conditions with the most severe cold relative-to-normal centered over the Upper Midwest and Great Lakes. The phrase “polar vortex” became part of the vernacular when it came to talking about the winter weather in the central and eastern US. Most of the same area also experienced above-normal snowfall with Philadelphia’s International Airport recording it 2nd snowiest ever at 68” - second only to 2009-2010 when 78.7” piled up. Reagan National Airport in Washington, DC had its 9th snowiest winter ever with 32”, and Central Park in New York City measured well-above normal amounts of 57.4”.

There are several factors listed below that point to another cold and snowy winter in the Mid-Atlantic region which would give us “back-to-back” cold and snowy winters – not all that uncommon in this part of the country (e.g., 1976-1977/1977-1978; 1983-1984/1984-1985):

1. Strong positive (warm) sea surface temperature anomaly in the northern Pacific Ocean 2. A weak-to-moderate “centrally-based” El Nino (warm) in the tropical Pacific Ocean 3. Favorable conditions for “high-latitude blocking” (low solar activity, above-normal and "expanding" autumnal snowpack, October Arctic Oscillation index signal)

Pacific Ocean sea surface temperature (SST) anomalies Last winter featured a strong positive anomaly in sea surface temperatures in the northern Pacific Ocean and all indications are that this same anomalous pattern will continue through the upcoming winter season. Meanwhile, farther south in the tropical Pacific, there is a new feature for this winter as weak-to-moderate El Nino conditions (i.e., warmer-than-normal SSTs) have developed and should last through the winter season before perhaps withering away later next year. Currently, the center of the above-normal sea surface temperature pattern in the tropical Pacific is close to the west coast of South America; however, computer forecast models (e.g. CFSv2, JAMSTEC) suggest the weak-to-moderate El Nino should become “centrally-based” during the winter season with the warmest waters relative-to-normal shifting from the eastern Pacific to the central Pacific.

The combination of a “centrally-based” El Nino in the tropical Pacific along with the warm anomaly in the northern Pacific is likely to lead to an upper air pattern that consistently features high pressure ridging along the west coast of North America and low pressure troughing in the eastern US. This kind of upper air pattern typically allows for the frequent penetration of cold, Canadian air masses into the central and eastern US from northern Canada - as was the case quite often last winter. The similarities are truly remarkable between the expected Pacific Ocean SST anomaly pattern for this upcoming winter (warm pocket up north and "centrally-based" weak-to-moderate El Nino near the equator) and the actual one that occurred during the fifteen coldest winters in the past 60 years (see video discussion for details).

[CFSv2 SST anomalies forecast for Jan-Feb-Mar 2015; courtesy NOAA]

“High-latitude blocking” and low solar activity In addition to the sea surface temperature anomaly pattern in the Pacific Ocean, “high-latitude blocking” is another important factor with regard to winter weather forecasting in the central and eastern U.S. “High-latitude blocking” is generally characterized by persistent high pressure in northern latitude areas such as Greenland and this typically leads to cold air outbreaks into the central and eastern U.S from northern Canada. Research has shown that low solar activity tends to be correlated with high-latitude blocking patterns and despite the fact that we are in the solar maximum phase of solar cycle 24, it is actually a period of relatively low solar activity as this solar max is one of the weakest in many decades - perhaps even the weakest in more than a century – and low solar activity is expected to continue through the winter season.

“High-latitude blocking” and the northern hemisphere snowpack Some research studies have documented a connection between northern hemisphere snowpack during fall seasons and “high-latitude blocking” patterns in following winter seasons. Specifically, if snowpack is above-normal and consistently expanding during the fall season in many of our cold air source regions (e.g. Canada, Greenland, Siberia) then there is an increased chance for more frequent “high-latitude blocking” patterns in subsequent winter months. North America snow cover extent actually reached record highs at the end of September in records dating back all the way to 1967 (data courtesy Rutgers snow lab at http://climate.rutgers.edu/snowcover/chart_anom.php?ui_set=1&ui_region=namgnld&ui_month=9) and the entire northern hemisphere had its 3rd highest levels at the end of the month.

[North American snow cover anomalies at end of September (record high); courtesy Rutgers snow lab]

As far as October is concerned, the snow coverage in Eurasia (Asia in particular) is off to the races. The all-important cold air source region of Siberia has experienced consistent expansion (southward of 60°N) of its snowpack during October and research has correlated this type of autumnal snowfall in this precise part of the world with more frequent wintertime “high-latitude blocking” patterns in following winter months. In many parts of Siberia, the snow cover has rapidly advanced in recent days to levels not seen at this stage of the autumn season since at least the year 2000.

[Expansion of Siberian snow cover (in white) from early-to-mid October; courtesy NOAA]

The Arctic Oscillation index and its October signal for “high-latitude blocking” High-latitude blocking can be tracked by meteorologists through indices known as the Arctic Oscillation (AO) and its closely-related cousin called the North Atlantic Oscillation (NAO). When the AO is positive, for example, surface pressure is low in the polar region and this helps the mid-latitude jet stream to blow strongly and consistently from west-to-east keeping Arctic air locked up in the polar region. When the AO index is negative, there tends to be high pressure in the polar regions (i.e., “high-latitude blocking”), weaker zonal winds, and greater movement of polar air into the middle latitudes. While the AO index and its closely-related cousin called the North Atlantic Oscillation (NAO) are primarily used during the winter season, trends in October can provide important clues about the ensuing winter season.

Indeed, earlier in October, the AO plunged into negative territory not seen during the month of October in over a decade. The map below shows the observed AO index value (in black) as it bottomed out at -4 on October 9th before an upturn. The lowest level ever seen for the AO index in the month of October which was -5.09 recorded on October 18th, 2002. In fact, the last time the AO was lower than -3.5 during the month of October was in 2002 and there have only been five times where the AO index has been below -4.0 during the month of October. As it turns out, when we look at the winters since 2002 that experienced an AO index below -2 during the month of October, almost every one (6 out of 7) experienced above-normal snowfall in the Mid-Atlantic region and below-normal temperatures. For example, snowfall in New York City for these particular 7 winters had an average snowfall total of 40 inches compared to the normal amount of ~25 inches and only one of those winters included below-normal snowfall. The AO and NAO indices are likely to spend much of the time this winter in negative territory indicative of frequent “high-latitude blocking” patterns. By the way, the all-time low for the AO index in any month came during the brutally cold month of January 1977 when it bottomed out at a value of -7.43.

[Arctic Oscillation index (actual black; forecast red); courtesy NOAA]

The bottom-line Much of the eastern two-thirds of the nation should experience another colder-than-normal winter season with the western-third of the nation (Denver-to-Los Angeles) likely to be warmer-than-normal. Overall temperatures in the Mid-Atlantic region should end up about 1.5-3.0 (degrees Celsius) below-normal for the winter season (November through March) and similar chill relative-to-normal can be expected all the way down to the Gulf coast.

Snowfall should be at least ten inches above normal amounts in the Mid-Atlantic region this winter with more than 25 inches likely in the DC metro region, more than 30 inches in and around Philly, and more than 35 inches in the New York City metro region. The winter is likely to get off to a quick start with some notable cold and snow following what is likely to be a relatively mild beginning to the month of November in the Mid-Atlantic region.

Video

httpv://youtu.be/41CDNlIzvRA

12:45 PM | "Long-lost" satellite images shed new light on global sea ice...enormous holes found in the Arctic ice back in the 1960's...Antarctica sea ice reached record highs and lows just two years apart

[Hurricane Gladys as seen by NASA’s Nimbus 1 satellite in September 1964; courtesy NASA]

Discussion

Overview NASA launched the first of seven Nimbus spacecraft to study Earth from space in August 1964 and fifty years later experts at the National Snow and Ice Data Center in Boulder, Colorado are recovering long-lost images from old Nimbus data tapes and black-and-white film. The preliminary findings from long-lost images from the 1960’s have produced some big surprises with respect to global sea ice. In much the same way archeologists dig up artifacts that can rewrite history, these long-lost satellite images have to potential to rewrite our knowledge of ever-changing global sea ice cycles.

The Nimbus program Fifty years ago NASA launched the first in a series of Earth-observing satellites that revolutionized how scientists study Earth’s weather systems, environment and atmosphere. The Nimbus satellites were a series of seven Earth-observation satellites launched over a 14-year time period from 1964 to 1978, one of which did not achieve orbit. In total, the satellites provided Earth observations for 30 years and collectively carried a total of 33 instruments, including ozone mappers, the Coastal Zone Color Scanner instrument and microwave and infrared radiometers. The Nimbus series were the first meteorological satellites to provide day and night local area coverage every 24-hours, repeated at the same time daily. This “sun-synchronous” orbit became the norm for satellites in subsequent years. Nimbus were also the first satellites to provide day and nighttime pictures of intense hurricanes as viewed from space which initiated the use of satellite technology to provide hurricane warnings (example image above). Many at NASA's Goddard Space Flight Center (Greenbelt, MD) regard Nimbus as the "granddaddy of the current Earth-observing fleet" and the overall program as a "smashing success and a huge return on investment".

Nimbus satellite observations were transmitted as an analog signal and then burned onto film and stored in canisters labeled only by orbit number (i.e., no indication of geography). The only way to retrieve this imagery data into usable format by specific land area was to scan all of it which meant 250,000 images. Now the satellite imagery data is completely digital and can be managed and manipulated by scientists in order to get a look at the past. Initial work with the newly-digitized satellite data has been performed for the 1964-1969 time period and now the year 1970 is being analyzed.

Global Sea Ice In terms of global sea ice, our current satellite data records are quite good for a little more than the past 30 years or so. Pushing it back another 15 or 20 years could be crucial in the understanding of global sea ice cycles which have been occurring throughout history. Indeed, early findings have been quite surprising with respect to both the Arctic and Antarctica sea ice extent. According to NASA scientists, while there was more ice compared to today, there have been “enormous holes" found in the Arctic ice that "we didn’t expect and can’t explain” in a decade considered to be colder-than-normal (i.e., the 1960's). The Antarctica sea ice extent findings are perhaps even more amazing. Using these long-lost satellite images, it appears that the Antarctica sea ice extent reached record high levels in 1964 only to be followed by record low amounts just two years later in 1966, and the earliest maximum sea ice extent was seen in 1969. As is often the case with more data, it often leads to more questions than answers. Video discussion on this by NASA scientists at http://www.youtube.com/watch?v=bvGIE1y3cXA.

1:15 PM | Important October clue about a possible snowy winter - the plunging Arctic Oscillation (AO) index

[GFS model forecast of the Arctic Oscillation (AO) index to the middle of October]

Discussion

There is an index called the Arctic Oscillation (AO) which is defined by surface atmospheric pressure patterns and it is tracked closely by meteorologists during winter seasons as it can provide clues as to whether Arctic air has the potential to be transported from the northern latitudes to the middle latitudes. When the AO is positive, for example, surface pressure is low in the polar region and this helps the mid-latitude jet stream to blow strongly and consistently from west-to-east keeping Arctic air locked up in the polar region. When the AO index is negative, there tends to be high pressure in the polar regions, weaker zonal winds, and greater movement of polar air into the middle latitudes. While the AO index and its closely-related cousin called the North Atlantic Oscillation (NAO) are primarily used during the winter season, trends in October can provide important clues about the soon-to-follow winter season. Indeed, the AO is about to plunge into territory not seen during the month of October in over a decade and there is an outside chance it reaches record low territory for the month of October.

The map above shows the observed AO index value (black) up to the current date and then the forecasted values (in red) to the middle of the month. The AO is forecasted to plunge over the next couple of weeks to around -5 (legend at left) which is very close to the lowest level ever seen for the AO index in the month of October which was -5.09 recorded on October 18th, 2002. In fact, the last time the AO was lower than -3.5 during the month of October was in 2002 and there have only been five times where the AO index has been below -4.0 in October. By the way, the all-time low for the AO index came during the brutally cold month of January 1977 with a value of -7.43.

As it turns out, when we take a look at the winters since 2002 that featured an AO index below -2 during the month of October, almost every one (6 out of 7) experienced above normal snowfall in much of the Mid-Atlantic region and usually below-normal temperatures as well. Stay tuned…Vencore Weather winter outlook coming in November.

12:30 PM | Southern hemisphere sea ice areal extent reaches record high in satellite era; northern hemisphere continues at well below normal levels, but above the low point set two years ago

[Yellow line represents 2014 southern hemisphere sea ice areal extent; courtesy University of Illinois "cryosphere" and NOAA/NCEP]

Discussion

Overall Summary The amazing recent expansion of Southern Hemisphere sea ice areal extent has continued and it has just reached an all-time high in the satellite data era which began 35 years ago in 1979 (above). This is the time of year when the southern hemisphere usually reaches its highest extent for the year (i.e., just ended their winter season) and the high for this year has also surpassed the all-time high during the past 35 years of record-keeping. The northern hemisphere sea ice areal extent – now near the low point of the year (i.e., just ended their summer season) - continues at well below normal levels, but it is above levels seen two years ago which were the lowest minimum amounts recorded since 1979. Overall, given the recent surge in the southern hemisphere to record levels, the global sea ice areal extent has spiked into “above-normal” territory (below).

[red line represents 2014 global sea ice areal extent relative to normal at zero line; courtesy University of Illinois "cryosphere" and NOAA/NCEP]

Southern Hemisphere Sea Ice The remarkable period of increasing sea ice areal extent in this part of the world has actually been occurring for the past few years with only a few brief exceptions to that overall upward trend. Back in 2011, the southern hemisphere sea ice areal extent was at below-normal levels, but it is currently running nearly 1.7 million square kilometers above the 1979-2008 mean (courtesy University of Illinois "cryosphere" web site with data originating from NOAA/NCEP Snow and Ice Data Center).

Northern Hemisphere Sea Ice The northern hemisphere sea ice areal extent is still well below normal relative to all years going back to 1979 although it is noticeably above the lowest point set two years ago at this same time of year (plot below). The northern hemisphere sea ice areal extent is about 1.2 million square kilometers below normal using the base period of 1979-2008 for comparison. The northern hemisphere sea ice areal extent has generally trended lower since the mid 1990’s reaching primarily below-normal levels after the turn of the century. In the past several years, however, there has been a leveling off of that downward trend in terms of sea ice areal extent at those below-normal levels.

In the time period before the mid 1990’s, the sea ice extent was generally above-normal dating back to 1979. The directional shift in 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, the Atlantic Ocean has a significant impact on northern hemisphere sea ice areal extent and the AMO index flipped in phase during the mid 1990’s from negative (cold) to positive (warm) and the trend changed direction at that point in time. Once the northern Atlantic sea surface temperatures flip back to cooler-than-normal values – perhaps in the next few years - the northern hemisphere sea ice areal extent should return to the normal or above-normal levels seen prior to the mid 1990’s.

[Yellow line represents 2014 northern hemisphere sea ice areal extent; courtesy University of Illinois "cryosphere" and NOAA/NCEP]

10:45 AM | Hottest August ever...not so fast according to satellite observations

Discussion

Overview NASA’s Goddard Institute of Space Studies (GISS) released a report earlier this week suggesting that August was the hottest August ever recorded on a global basis in its 134 years of record keeping dating back to the year 1880 (actually the initial report was quickly revised by NASA making it the second hottest August ever in their dataset). The global temperature anomaly map (below) from NASA displays the global temperature anomalies for August 2014 versus the 1981-2010 averages with the overall anomaly calculated at +0.31°C. The “yellow/orange/red” areas on the map represent those areas with temperatures above the 1981-2010 averages and the “blue/purple” regions experienced below average temperatures. Other datasets, however, which rely primarily on satellite observations for temperatures as compared to thermometer-based measurements, show a strikingly different story with respect to where August 2014 stands historically in terms of August global temperature anomalies.

[NASA global temperature anomalies for August 2014]

NASA’s GCHN and ERSST dataset and some known problems The NASA global land and ocean temperature anomalies are a merged product of the Global Historical Climatology Network (GCHN) which relies on ground-level thermometer-based temperature measurements from 6000 weather stations around the world and the Extended Reconstructed Sea Surface Temperatures (ERSST) for ocean temperatures. There are some known problems associated with thermometer-based datasets that include poor data coverage in significant portions of the polar regions and also the need for data “adjustments” at many weather stations in order to eliminate urban heat island (UHI) effects.

Data Sparse regions An important problem related to thermometer-based temperature measurements around the world is that there are several sparse data regions located away from developed countries, which are concentrated on the land masses and in the northern hemisphere mid-latitudes. While these developed areas have a dense network of weather stations, temperature monitoring equipment is scarce in some parts of the Amazon, Africa, Antarctica, and Arctic. In the Arctic, particularly, the absence of solid land means there are large areas without weather stations. NASA addresses this problem by “filling” in the gaps with data from the nearest land stations, up to a distance of 1200 kilometers (746 miles) away. In this way, the NASA analysis achieves near total coverage in the Arctic. This approach by NASA may either overestimate or underestimate Arctic warming and the same concerns hold true for Antarctica and the other data sparse regions. Indeed, NASA scientists suggest "there's no doubt that estimates of Arctic warming are uncertain, and should be regarded with caution," when describing this particular approach of “in-filling” (http://www.giss.nasa.gov/research/news/20110113/).

For the month of August, this “in-filling” of data by NASA in the large data sparse region of Antarctica resulted in an area of very high temperature anomalies – in fact, the highest “relative-to-normal” temperatures (4-7°C) seen anywhere across the globe – and this could be an overestimate of the warming in that region; especially, given the fact that sea ice areal extent surrounding the continent expanded to or near record levels almost on a daily basis throughout the month (http://arctic.atmos.uiuc.edu/cryosphere/antarctic.sea.ice.interactive.html; yellow curve on plot represents 2014). Also, in this data sparse region of Antarctica, there exists the somewhat unlikely scenario of the month’s coldest temperature anomaly (purple region) in close proximity to the just described warmest anomaly (circled area on map). One final note with respect to data sparse regions, NOAA’s National Climatic Data Center (NCDC) uses this same GCHN dataset for historical global monthly temperature comparisons and they do not use this “in-filling” approach, but simply keep areas that have no data coverage as “missing data” regions in their calculations resulting in large portions around the world not having any impact on the monthly global temperature anomaly.

Urban Heat Island effects In addition to the problem of data sparse regions for thermometer-based temperature measurements around the world, there is the added problem of urban heat island (UHI) effects that presents difficulties in historical temperature comparisons. In numerous weather station locations, the local surrounding areas have changed dramatically over time from rural to urban-like (i.e., more asphalt, concrete) and this change is known to have an important “artificial warming” effect on overall temperatures. The biggest “artificial warming” impact from UHI effects is during nighttime hours when winds are relatively weak and materials such as concrete and asphalt act to slow down the cooling process. It is important to eliminate UHI effects from thermometer-based datasets used for historical temperature comparisons in order to accurately evaluate climatic trends. As a result, NASA applies “adjustments” to numerous urban and near-urban weather stations within the GCHN dataset in order to minimize or eliminate these UHI effects (http://data.giss.nasa.gov/gistemp/). Applying the correct “adjustments” to thermometer-based temperature measurements is a difficult task taken on by NASA (and NOAA) in order to reduce or eliminate urban heat island effects. Many complex questions must be answered such as “what is the correct magnitude for the “adjustment”, how far away from urban stations do “adjustments” need to be made, and “how do you change the “adjustments” for a particular location from decade-to-decade (Las Vegas and Phoenix, for example, changed significantly from the 1930’s to the 1960’s to the 1990’s). (For more information on UHI effects visit http://en.wikipedia.org/wiki/Urban_heat_island).

Satellite observations of lower tropospheric temperatures In today’s world, approximately 99% of all observations used in weather and climate analysis come from remote sensing techniques and primarily from satellites. Satellite measurements of the Earth’s microwave emissions are a crucial element in the development of an accurate system for long-term monitoring of atmospheric temperature. Special sensors (microwave sounding units) aboard satellites have orbited the Earth since the late 1970’s allowing scientists to calculate temperatures of the atmosphere in the lower troposphere. While satellite observations are not without some of their own limitations, they provide nearly complete global coverage and homogeneous data quality at much higher densities than attainable with in situ observations. In situ observations also suffer from non-uniform temporal coverage and undocumented changes in the instrumentation used that can lead to local biases and increased uncertainty. Finally, satellite-derived temperatures don’t require the “UHI adjustments” often required with conventional weather station temperature measurements.

UAH and RSS – two temperature datasets that rely on satellite observations Two datasets that rely on satellite observations for lower tropospheric temperatures include the UAH and RSS. The record-keeping for these two datasets goes back to 1979, which is when the satellite-observations data-keeping era began. The UAH is a product of the Earth System Science Center of the University of Alabama in Huntsville (UAH) and has relied on the NASA Aqua AMSU satellite in recent years. The UAH lower troposphere temperature data are for latitudes of 85°S to 85°N which represents more than 99% of the surface of the globe. The UAH results for the month of August in terms of where it stands historically were noticeably different than NASA’s findings. Specifically, the UAH lower troposphere global temperature anomaly for August 2014 was calculated at +0.20°C and there are seven hotter Augusts compared to this year in just the 35 years of data going back to 1979. (For more information on UAH data: http://nsstc.uah.edu/climate/).

Like the UAH lower troposphere temperature data, Remote Sensing Systems (RSS) calculates lower troposphere temperature anomalies from microwave sounding units which, in this case, are aboard a series of NOAA polar-orbiting satellites. The RSS lower troposphere temperature data are for latitudes of 70°S to 82.5°N. The RSS results for August global temperature anomalies are dramatically different than NASA’s findings. The RSS lower troposphere global temperature anomaly for August 2014 was calculated at +0.193°C and there are thirteen hotter Augusts in the 35 years of data going back to 1979. In fact, while still above normal compared to the base period 1981-2010, RSS data shows August 2014 to be the 7th coolest August since 1995. (For more information on RSS data: http://www.remss.com/missions/amsu/).

The complete record for the RSS, UAH and NASA global temperature anomalies for each and every August going back to the year 1979 is presented in Table 1 (below) using 1981-2010 as the base period for comparison.

Table 1: August global temperature anomalies (°C) where “bold, red” indicates those previous Augusts that were hotter than this August

[RSS, UAH, NASA: using base period for comparison of 1981-2010]

RSS data (courtesy Remote Sensing Systems): http://data.remss.com/msu/monthly_time_series/RSS_Monthly_MSU_AMSU_Channel_TLT_Anomalies_Land_and_Ocean_v03_3.txt

UAH data (courtesy Dr. Roy Spencer, Dr. John Christy and University of Alabama at Huntsville): http://www.nsstc.uah.edu/data/msu/t2lt/uahncdc_lt_5.6.txt

NASA data using GHCN-v3 1880-08/2014 + SST: ERSST 1880-08/2014: http://data.giss.nasa.gov/gistemp/maps/

12:30 PM | Solar flare prompts a geomagnetic storm warning for September 12th

[Current solar image with circled area showing the active sunspot region that produced a solar flare on Tuesday; courtesy spaceweather.com]

Discussion

An active sunspot region officially called AR2158 erupted on Tuesday, September 9th, producing an explosion that lasted more than 6 hours. This long duration solar flare peaked with a classification of M4 (medium-sized) on the intensification scale for solar storms. Long-duration solar flares tend to produce bright coronal mass ejections (CMEs) and this one was no exception. The Solar and Heliospheric Observatory (SOHO) observed a CME racing out of the blast site at nearly 1000 km/s (2.2 million mph; see video). NOAA's solar wind model is forecasting this CME to deliver a glancing, but potent blow to earth’s magnetic field by early on Friday, September 12th (see video). This could result in beautiful auroras visible late tomorrow night/early Friday across the northern tier of the US so sky watchers should be on alert. One final note, active sunspot region AR2158 will be in a position that is directly facing the Earth over the next few days; consequently, any additional ejections can result in an eventual direct impact on the Earth's upper atmosphere.

Video

httpv://youtu.be/XdgM4zfc67k