The Importance of Research Field Campaigns in Understanding Sub-Daily Forecasting (Credit: NOAA National Severe Storms Laboratory)
DISCUSSION: Field campaigns in the atmospheric sciences play a vital role in allowing forecasters and researchers to obtain further knowledge on the evolution of the state of the atmosphere. This is especially true in situations where high impact weather is expected to occur over densely populated areas. This year, The National Severe Storms Laboratory launched the Targeted Observations by Radars and Unmanned aerial surveillance of Supercells (TORUS) experiment designed to investigate the dynamics of ongoing severe thunderstorms and how their evolution may lead to the potential formation of tornadoes. The focus of the TORUS experiment is within the planetary boundary layer – the lowest layer in the atmosphere influenced by the frictional force of the wind, and how its constant changes could impact nowcasting and forecasting of ongoing severe weather threats. Much like the Mesoscale Convective Experiment (2013) and Plains Elevated Convection At Night (2015) experiment, an overarching goal of TORUS was to advance the current knowledgebase of supercells and how changes in their intensity as a function of the surrounding environment can help enhance or degrade a public forecast while also serving as extra information to ingest into weather models for enhanced predictability at relatively short time scales. The combination of ground-based equipment and techniques along with the use of NOAA’s Lockheed P-3 Orion “Hurricane Hunter” should return plenty of information.
Normally, the National Weather Service Weather Forecast Offices (NWS WFOs) launch radiosondes at 1200 and 0000 UTC (e.g., 8 AM/8 PM EDT) to sample the overall atmospheric profile and obtain valuable information for the prediction of severe storms. One particular case in where forecasters benefitted from the additional data supplied by TORUS was with the most recent high risk severe weather day on 20 May. The mobile soundings provide extra atmospheric data at unconventional times in the day that are the stepping stone to potential modifications for a forecast. For instance, a TORUS sounding taken near Vinson, OK at around 1930 UTC (2:30 PM CDT) showed a highly unstable environment and highly favorable for the development of significant supercells that could have led to long-track, violent tornadoes. Compared to a more traditional 1200 UTC sounding, that meant that over seven hours had elapsed which is ample timing for the environment to change considerably. Ultimately, this was not the case across much of central and southern Oklahoma on 20 May for which the reasoning is still up for much debate to this date, but it is information like these soundings that give forecasters a leg up on making the necessary quick decisions with a rapidly changing environment.
Even with the ability to interrogate the atmosphere with mobile soundings, it also elucidates more questions and unknowns for researchers to grasp onto moving forward. For example, why did the 20 May severe weather outbreak not materialize as expected despite environmental parameters suggesting an outbreak akin to the 27 April 2011 tornado outbreak over the Deep South states of Mississippi and Alabama? Or, how is it that “lower” severe weather risks issued by the Storm Prediction Center lead to more active days? These are good questions to ponder about and while mobile soundings may not provide the entire story to the eventual growth and while the world of research to operations (commonly known as R2O) has much to learn about sub-daily (and even sub-hourly) forecasts, field campaigns like TORUS provide the necessary benefits for forecasters and researchers alike to gain a richer understanding of quickly evolving atmospheric conditions.
More about the TORUS experiment can be found here.
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Sounding credit: Manda Chasteen
© 2019 Meteorologist Brian Matilla
DISCUSSION: In looking back to August 2017 and the Atlantic hurricane season, there is no debate that one of the events which stood out among the rest quite a bit was Hurricane Harvey. Hurricane Harvey is arguably most remembered for its impacts with respect to the major flooding the storm delivered in and around the city of Houston, Texas. However, the other major aspect of Hurricane Harvey which made headlines for quite a while was how the storm rapidly intensified from a Category 3 to a Category 4 just before making landfall in southeast Texas. There continued to be substantial interest in this topic which inspired and ultimately led to more comprehensive research on the issue from both academic institutions as well as various weather and climate research agencies. The main conundrum is the fact that as hurricanes approach shallower coastal waters and continue to induce substantial oceanic mixing, this brings up much cooler water which often helps to weaken the storm or stabilize any further intensification. However, this is not what transpired with Hurricane Harvey and hence, the reason for why much further research was needed. One such example of this research came from a research group over at Texas A&M University.
In this research, “They found the Bight was warm all the way to the seabed before Harvey arrived. Strong hurricane winds mix the ocean waters below the storm, so if there is any cold water below the warm water at the surface, the storm's growth will slow. But there wasn't any cold water for Harvey to churn up as it neared the coast, so the storm continued to strengthen right before it made landfall, according to the study's authors.
"When you have hurricanes that come ashore at the right time of year, when the temperature is particularly warm and the ocean is particularly well-mixed, they can absolutely continue to intensify over the shallow water," said Henry Potter, an oceanographer at Texas A&M and lead author of the new study in the American Geophysical Union's Journal of Geophysical Research: Oceans.
The researchers don't yet have enough temperature data to say if the Texas Bight was unusually warm in 2017. But the findings suggest hurricane forecasters may need to adjust the criteria they use to predict storm intensity, according to Potter. Forecasters typically use satellite measurements and historical data to make intensity predictions, but Harvey's case shows they need data collected from the ocean itself to know exactly how much heat is there, where that heat is located in the water column and if it's easily accessible to the storm, Potter said.”
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© 2019 Meteorologist Jordan Rabinowitz
The Subtle Yet Fundamental Differences Between Deterministic and Probabilistic Weather Forecasting (credit: National Weather Service and Tropical Tidbits)
DISCUSSION: For many years, weather forecasting has proven challenging for forecasters and researchers. Marked by consistent improvement yet continual obstacles, the nature of forecasting any type of weather event from benign showers to a full-scale severe weather outbreak is loaded with stochasticity. But at the core of weather forecasting, two schools of thought dominate the practice: deterministic and probabilistic forecasting. Each one of these is subtly different at the surface, but fundamentally they have their characteristic differences.
Deterministic forecasts are based specifically on a given value or range for an area at a given time (e.g., temperature at morning rush hour or evening commute). This is the kind of product we are used to seeing on forecast bulletins and on local news media. Examples of a deterministic forecast include the first tweet above with a range of values for potential ice accumulation over central Oklahoma. A precise value or time is important for the general public as it gives people a frame of reference for what to expect.
Probabilistic forecasts take on a different approach and instead focus on the likelihood that a parameter of any weather event is likely to exceed or occur in a given area. There are indeed various tools that facilitate the growth and understanding of improving forecast accuracy through probabilistic forecasting methods. Mentioned in a previous article with more detail, ensembles are different iterations with parameters tuned slightly differently to reflect differing outcomes. This approach sacrifices a specific (or range) number in exchange for a probability of occurrence beyond a certain threshold (ex: probability of rainfall total greater than 0.01 inches suggested by the second tweet above). Yes, it may seem tricky given that it’s different than the accustomed way, but it is meant to illustrate the difference and carries an emphasis of its own regard.
Agencies like NOAA’s National Severe Storms Laboratory are leading projects such as the Warn-on-Forecast experiment which utilizes sophisticated and refined modeling and data collection techniques to generate weather forecasts based greatly on probability of occurrence. What is the ultimate goal? Forecasters could utilize the added information and produce more accurate forecasts and respond quicker to developing hazards. This in turn could lead to a greater chance of saving life and property in the event of hazardous weather phenomena like tornadoes, flash floods, and large hail by providing ample watch/warning times to the public.
It’s safe to say that as forecasting techniques become more refined with time, these two schools of thought will continue to branch out in technicality and carry a bigger impact in their own regard. What do you think about the differences between the two? Would you rather prefer a deterministic forecast with say a total range of rainfall in a given day, or a probabilistic forecast with a message of likelihood that it will rain/storm on a given day or time? Let us know in the comments!
Image credit: Tropical Tidbits
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© 2019 Meteorologist Brian Matilla
DISCUSSION: According to NASA and NOAA the year 2018 was the fourth warmest on record, coming in at around 0.8 degrees C above the 20th century average. This year also began with La Niña conditions in place over the eastern Tropical Pacific Ocean. These conditions held well into the spring and early summer, then during the fall weak El Niño conditions developed. In spite of the warm year globally, much of the central USA experienced cool conditions in March and April 2018, followed by a warm May and June. Also, a strong cold spell dominated much of the central USA from mid-October through November.
The phenomenon described last year, the pool of warm oceanic water in the Northeast Pacific known colloquially as “the blob” (e.g. Bond et al. 2015, Pinhero et al. 2019), was present again this year. But, the “blob” did not make much news in 2018, see last year’s publication for more on this event.
Here, we perform an overview the blocking occurrences in 2018 using the University of Missouri blocking event archive (http://weather.missouri.edu/gcc). We will examine the blocking occurrences for each region of the Northern Hemisphere (NH) and Southern Hemisphere (SH) separately, and discuss a few recent trends in blocking activity.
a.The Northern Hemisphere
As noted in last year’s installment, the number of blocking events that occur annually has been higher since about 2000 than the previous 30-year period (1970- 1999), and a new publication (Lupo et al. 2019) will highlight these trends. During 2018, 50 blocking events occurred over the entire NH, which is higher than last year’s total (40) and quite a bit higher than the mean early 21st century occurrences (38). Since we typically expect +/- 8.5 events, 2018 was a “blocky” year. The persistence of 2018 blocking events was similar to their climatological mean for early 21st century blocks (about 9 days), and their intensity was close to the climatological mean strength as well.
Over the Atlantic Region (80 degrees W – 40 degrees E longitude) in 2018, there were 22 blocking events that occurred and this is almost 40% more than the regional mean. We have stated that the occurrence of blocking can be episodic, and during 2018, 13 of these Atlantic Region blocking events occurred over Eastern Europe and Western Russia. Three of these occurred during October and November in particular. The first one during mid-October caused a strong warm spell across much of Eastern Europe and Western Russia (Fig. 1a), and in some places the warmth was record setting. The latter two blocking events occurred during November and were about two weeks in duration each. The first of these was a moderately strong event, while the second was classified as strong. These events led to warmer than normal conditions over northeastern Europe and cooler than normal conditions from Ukraine to the Urals (Fig. 1b) during the month of November.
Within the Pacific Region (140 degrees E- 100 degrees W), the 2018 blocking occurrence (13) was close to the climatological normal (12) in number and duration (9-10 days). For the second straight year, most of these blocking events (11) occurred over the Northeast Pacific, but unlike last year, these were distributed throughout the year. One event occurred during mid-October (9-19 October), and combined with the Atlantic Region event described above, resulted in a very cold month for the western 2/3 of North America (Fig. 1a). Thus, North America was caught in the middle of a NH simultaneous blocking episode, which is not exactly rare. However, when the impact North America tend to anchor in persistent cool conditions. Also, Nunes et al. (2017) and references therein show extreme cold over North America is typically associated with blocking in the eastern Pacific Region. As we stated last year, the re-emergence of the Pacific Region “ridiculously resilient ridge” provided the impetus for more Pacific blocking. This also caused more blocking to occur throughout 2018 in the east Pacific. This prevalence for blocking over the eastern Pacific in 2018 led to Alaska experiencing a very warm year as seen in Fig. 1. The early winter saw very little snow over the interior of Alaska.
Figure 1. The Northern Hemisphere surface temperature anomaly (oC) for a) mid-October, 2018 (left), and b) November 2018 (right).
In 2018, it was the Continental Region (Weidenmann et al. 2002) that experienced more than double the number of events that during the previous year (2017). This was nearly 50% more than typical as well. These 15 blocking events were sprinkled over the Asian Continent throughout the year, and for the second year in a row, none occurred over North America in 2018. But, as shown in many studies, the occurrence of blocking over North America is comparatively rare.
a.The Southern Hemisphere
In the SH, there were 27 events during 2018 which is the most since record began to be kept in 1970. This breaks the record previously set in 2013 (24), and this is about a 65% greater frequency of occurrence over the annual climatological value (16.5). Weidenmann et al. (2002) demonstrated that most blocking events occur in the South Pacific and during the months of May and June. The record setting year was paced by the occurrence of 19 events over the South Pacific, and seven over the Indian Ocean sector. Normal for these two regions is 12 and three events, respectively. Like last year, the normal peak time only involved five SH block occurrences (late fall - May and June). Also, following 2017, the spring period from October to December saw six block occurrences. This time of the year is very quiet normally in the SH with respect to blocking activity. Most of the blocking events (16) occurred over the southwest Pacific from Australia to New Zealand and near the dateline throughout the year. This resulted in very warm temperatures over the western Pacific in 2018 (Fig. 2a), and Australian heat was often in the news in late 2018 into early 2019. Additionally Argentina and Brazil were cooler than normal.
The SH blocking of 2018 was a little less persistent than typical, the mean event lasting for seven days (compared to eight typically). During the year, only three events persisted for more than 10 days. These were a 17-day event near Australia in October, and two events (10 and 12 days) during the month of May. One of these May events occurred over the western Pacific and the other over the eastern Pacific. This double blocking event resulted in a temperature pattern for a 12 day period that mimicked the year overall in general (Fig. 2). Note than much of South America experienced cooler winter season temperatures at this time. In spite of the increased occurrence of SH blocking in 2018, the intensity of these events was very close to the climatological mean.
Figure 2: The Southern Hemisphere surface temperature anomaly (oC) for a) all of 2018 (left), and b) 24 May – 5 June 2018 (right).
In summary, for the third consecutive year, the number of blocking events globally was up (77 events). During 2018, there were 26% more blocking events globally than in 2017 (61) and this difference was accounted for by positive anomalies in both hemispheres. Only the NH Pacific and SH Atlantic showed blocking occurrences near the climatological norm, all other regions discussed were greater than normal. This year there were not any blocking events occurring in either hemisphere that made it onto the list of the top 20 strongest or persistent blocking events on record. Also, the duration and intensity of blocking in both hemispheres were very consistent with those which have occurred since 2000. Finally, blocking episodes were at least partly responsible for anomalous warm temperature conditions over Eastern Europe (especially the fall), the northeast Pacific and Alaska, and the entire western Pacific from Australia to New Zealand during 2018. Blocking also brought cooler conditions to the central USA and South America during their respective fall seasons, and over western Russia up to the Urals during the fall.
Bond, N.A., Cronin, M.F., Freeland H, and Mantua, N., 2015: Causes and impacts of the 2014 warm anomaly in the NE Pacific. Geophysical Research Letters, 42, 3414-3420. DOI: 10.1002/2105GL063306, 2015.
Lupo, A.R., A.D. Jensen, I.I. Mokhov, A.V. Timazhev, T. Eichler, and B. Efe, 2019: Changes in global blocking character during the most recent decades, Under Review, Atmosphere, January, 2019.
Pinheiro, M.C., Ullrich, P.A., and Grotjahn, R., 2018” Atmospheric blocking and intercomparison of objective detection methods: Flow field characteristics. Under Review, Climate Dynamics, January, 2019.
Wiedenmann, J.M., A.R. Lupo, I.I. Mokhov, and E. Tikhonova, 2002: The Climatology of Blocking Anticyclones for the Northern and Southern Hemisphere: Block Intensity as a Diagnostic. Journal of Climate, 15, 3459-3473.
Anthony R Lupo is a professor of Atmospheric Science specializing in the study of blocking anticyclone and jet stream dynamics at the University of Missouri and contributor to The Global Climate and Weather Center.
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© 2019 Meteorologist Anthony Lupo
DISCUSSION: In order for cloud droplets to form, they must have something to condense onto in our atmosphere (e.g., grain of dust, sea salt, etc.) Thus, it is thought that aircraft, for example, can aid cloud formation by emitting particles in their exhaust in addition to water vapor. However, scientists in Finland conducted a study where they found a different way for aircraft to potentially enhance precipitation processes. The picture above (image credit: Michael Bryant-Mode) is a dramatic illustration of the potential interaction between aircraft and clouds.
We have to first understand some basic ideas about precipitation formation before understanding the results of the study. When cloud droplets or cloud ice crystals first form, they are too small to fall as precipitation. In a pure liquid or pure frozen cloud, bigger droplets/crystals fall faster than smaller ones, collide with and stick to the smaller droplets/crystals, and eventually become large enough to fall as precipitation. In our atmosphere, water often doesn't freeze at 32 degrees Fahrenheit, but can exist in liquid form down to -40 degrees Fahrenheit (i.e., supercooled water). Thus, clouds can and often do contain a mixture of ice and liquid water. In this situation, the ice grows at the expense of the liquid, and this growth process is often much quicker than if the cloud was pure ice or pure liquid.
Imagine there is a cloud of supercooled liquid water (no ice) through which an aircraft flies. As the plane's wings and/or propeller moves through the air, the pressure and density of the air change such that temperature rapidly drops in a small area. This temperature decrease can result in the freezing of some of the supercooled water which can then trigger the accelerated ice growth process described above. These large ice crystals can then fall faster, collide with other smaller ice crystals, and grow even faster. Thus, even if aircraft produced no exhaust, the study from the Finish scientists indicated that 6-14 times more precipitation could be produced over a small area than if no aircraft flew through the cloud.
This is an example of another way that human activity can potentially influence the weather, perhaps in a way that we haven't thought of before.
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© 2019 Meteorologist Dr. Ken Leppert II
The Essence of True Weather Forecasting: Understanding the Inner Workings of a Weather Model (credit: Colin Zarzycki)
DISCUSSION: When it comes to weather forecasting, the first-order explanation involves the following process: Determine the region of interest, select an appropriate dataset, run a numerical model with the dataset to generate outputs, and create a forecast based on the model output. That may be the most straightforward answer but in truth, there is a plethora of information that lies within each individual step that would make this article become excessively long if driven into with such detail. However, as models become more complex and with the advent of supercomputing powerhouses such as Cheyenne (National Center for Atmospheric Research), broaching this topic has many useful insights and applications for a greater public understanding.
The Weather Research and Forecasting (WRF) model is currently the flagship numerical weather prediction engine that is capable of ingesting large quantities of data from a currently-operational model and in turn produces a forecast based on many billions of calculations of the physical and atmospheric governing equations. These model datasets range from a fine-scale, regional model such as the North American Model (NAM, which can use a grid scale of as small as 3km) to a coarser-scale yet fully global-coverage model such as the Global Forecast System (GFS, usually 0.25 degrees). On the time scale, one could utilize a more transient, rapidly-updating model such as the High Resolution Rapid Refresh (HRRR; updates each hour) to the less frequent but more comprehensive data from the European Center for Medium-range Weather Forecasting model (ECMWF; updates every 12 hours). The options are abundant, and through the help of powerful tools that can retrieve and process data from satellites and ground-based data, WRF also has the ability to perform calculations using these extra pieces of information. All in all, the central goal of such a powerful forecasting model is to provide as clear a depiction of the state of the atmosphere in the present and future through the help of weather model data and observations.
In many cases, forecasters often derive their outlook from a series of different outcomes known as an ensemble forecast. In general, ensembles are a group of forecasts that use a slightly different set of conditions in order to get a better understanding of the. These changes can range from the way that WRF utilizes a different atmospheric physics scheme to the way that WRF. WRF is re-run multiple times with subtle changes to the initial conditions, and that can yield vastly different forecasts which is where the element of uncertainty in forecasting comes into play. Bear in mind that the atmosphere is a dynamic fluid and changes are consistently occurring, so it is essential to understand and judge the forecasts appropriately. However, power still lies within the forecaster’s skill to interpret the most reasonable forecast given the expected changes in the short-term, and that holds valid when using multiple model products. A great example of this was the most recent “snow squall” that impacted portions of the Mid-Atlantic states of Pennsylvania and New York. The consensus between the 12km NAM and the 14km Community Atmosphere (CAM) model both showed snow in their forecast, but due to inherent differences in the techniques between the two models, the CAM was able to resolve, or show the development of, a squall-like feature in the forecast several hours in advance. It once again highlights the importance of analyzing multiple products to develop a precise forecast, but the availability of such vast options means more potential for forecasters to make sound decisions for short-term weather forecasts.
So what’s the future of weather forecasting and forecast models? It’s still a fresh research topic for researchers and forecasters alike and is applicable to many facets of daily and sub-daily forecasting. Model configurations at different space and time scales have potentially differing outcomes and greater computing power and increasingly efficient techniques will give forecasters the knowledge they need to issue more accurate forecasts in the coming years. Will we see a new system supersede WRF in the near-future? Possibly, as change is essential to the improvement of weather forecasting. But the recent improvements are a welcome sign for the near-future.
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© 2019 Meteorologist Brian Matilla
Ice core drilling helps scientists study past climate. Scientists that study past climate are called paleoclimatologists. Some paleoclimatologists drill out cores of ice from glaciers in the north and south poles to determine the temperatures of past years. Drilling out a core of ice shows different layers of snow, ice, and bubbles depending on the temperature of the time that a certain layer was at the surface.
NASA explains where these ice cores originate. Ice sheets and glaciers form from accumulating snowfall. Each year a new snowfall accumulation falls on top and compresses the previous year’s snow. Eventually, this compression of snow overtime is what makes a glacier. NASA also states that in some areas these layers result in ice sheets that are several miles thick.
According to the American Geosciences Institute (AGI), each ice layer shows the past temperature of the air. Scientists use the bubbles of oxygen molecules in the ice to determine what the temperature was for each layer of ice. Oxygen isn't the only gas that creates bubbles in the ice. Allegra LeGrande of NASA states that “scientists can directly measure the amount of greenhouse gases that were in the atmosphere at that time by sampling these bubbles.” Other gases found in ice cores include carbon dioxide and methane. Aerosols are also found within the ice such as, dust, ash, pollen, sea salts, and other chemicals/toxins.
The picture below is an ice core that was drilled out of Mount Hunter, Alaska by Bradley R. Markle as part of the Denali Ice Core Project. The discolored layers of the ice have bedrock and pebbles incorporated into the ice.
Overall, the study and drilling of ice cores help scientists understand how climate and the content of the atmosphere changed over thousands of years.
© 2019 Weather Forecaster Brittany Connelly
DISCUSSION: All over the world every day, there are a multitude of different factors which go into how various numerical model forecasts get generated. All the way from surface observations, to weather balloons, and on to aircraft data, there is a plethora of atmospheric data which is pumped into weather forecast models to help generate more realistic and near-term and longer-term forecast output. This is a result of the fact that, the more data and the greater the density of various data which being injected into the initial conditions of a numerical forecast model, the more accurate the forecast output will typically be.
The other major data component which is included as part of making projections with output from numerical forecast models which most people do not think about are those data resources which emanate from ocean-going ships. The primary data source which is most commonly referred to as “ship track” has to do with shipping vessels reporting atmospheric state-variables such as temperature, pressure, moisture, wind direction, and wind speed to archiving data systems over land. Moreover, since there is far more ocean on planet Earth than there is land, this leads to there ultimately being a substantial amount of data which comes in from “ship tracks.”
As shown in the graphic above (courtesy of Meteorologist Zack Labe from University of California-Irvine), you can clearly see how widely dispersed the shipping tracks were between 2004 and 2005 alone across the Northern Hemisphere. However, in looking to the Southern Hemisphere, you can see how there were substantially fewer shipping tracks archived during that 1-year period. Hence, it goes without saying that there is far much more shipping tracks data which is fed into both regional, synoptic, and global scale numerical forecast models across the Northern Hemisphere. This is also not surprising since most of the people which live on Earth preside within the Northern Hemisphere. Thus, it just goes to show how shipping tracks can tell someone a lot more than “meets the eye.”
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© 2018 Meteorologist Jordan Rabinowitz
DISCUSSION: There is no debate whatsoever that meteorological research has come quite a long way over the past 40 to 50 + years since the start of the modern remote sensing era. Having said that, there are still many mysteries concerning various details of the atmosphere and its many phenomena it creates that remain unknown (and/or possibly undetected) to atmospheric scientists around the world. One such example of an atmospheric phenomenon which remains somewhat alluring to atmospheric scientists around the world are gravity waves observed across the cloud-top expanse of intense tropical cyclones.
The primary reason for why gravity waves emanating from the inner cores of intense tropical cyclones have remained mysterious until more recent years (i.e., years since late 2016 when the GOES-16 or GOES-East satellite imager was launched into orbit) is due to the fine-scale at which this phenomenon occurs in real life. More specifically, prior to the years in which the GOES-East satellite imager was in active status, such a fine-scale atmospheric cloud-based phenomenon was nearly impossible to ever observe in real-time and study to any legitimate extent. However, with the advent of the GOES-16 satellite imager as well as its Western Pacific counterpart by way of the Himawari-8 satellite imager, atmospheric scientists have completely changed the game in terms of the high resolution at which atmospheric features can now be studied.
In getting to intense tropical cyclone-based gravity wave formation (one such example of which is captured above in association with Super Typhoon Meranti which occurred back in September 2016 over in the Western Pacific Ocean), such gravity waves which effectively look like “ripples in a pond” which emerge from the center of intense tropical cyclones form as a result of intense inner to outer pressure gradients. To be more precise, as a given tropical cyclone intensifies rapidly, there is a corresponding rapid change in pressure from the inner to outer parts of a tropical cyclone. This increasingly rapid change in atmospheric pressure from the center outwards generates a wave-like response which realizes in the form of gravity waves. Thus, this just goes to show how the current state-of-the-art satellite era has changed the way in which we observe Earth’s atmosphere.
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© 2018 Meteorologist Jordan Rabinowitz
DISCUSSION: There is little to no debate throughout the global atmospheric science community that hurricane forecasting has undergone a substantial and noticeable amount of improvement over the last thirty to forty years plus. Both with respect to being able to better anticipate the forward track of developing an intense tropical cyclones to also being able to predict their intensity as well as maximum intensity father in advance, there is no argument that atmospheric science has made tremendous strides in being able to better anticipate critical changes within tropical cyclones. Having said that, over the past ten to twenty years or so, operational hurricane forecasters over the NWS National Hurricane Center have developed ways to make even greater strides than many other regions of the world. This is due to an incredibly intelligent and experienced collective team of research and operational forecasters on hand as well as direct access to state-of-the-art numerical forecast model resources.
More specifically, many of the better tropical cyclone forecasts from around the globe have emerged in the wake of the introduction of ensemble forecast methods. Ensemble forecasting is a mode and an approach to operational forecasting wherein the forecaster in question utilizes a forecast model whose sole job is to effectively modify specific properties of model conditions at the start of the run to create various forecast solutions which add up to what is referred to as an ensemble. By then blending the respective future track and intensity results from the collection of different individual ensemble members, this then facilitates a better idea of the more likely range of possible solutions for the future of a given tropical cyclone event.
In the case of the current highest concern across the tropical Atlantic Ocean which happens to be Tropical Storm Florence, operational forecasters have been and will continue to integrate ensemble forecast approaches quite heavily right up to the point of landfall to have the best possible edge on the range of possibilities for the future track and intensity of what will more-than-likely soon again be Hurricane Florence. Moreover, it looking at the graphic attached above (courtesy of Meteorologist Sam Lillo from the University of Oklahoma), you will see how it is noted that the intensity forecast out to 5 days for Tropical Storm Florence happens to be the highest intensity forecast out through a 5-day period over the past twenty years. More importantly, this reflects how overall forecast confidence has evolved and changed over that time-span with the advent of higher-resolution regional as well as global models combined with infused ensemble forecasting techniques as well.
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© 2018 Meteorologist Jordan Rabinowitz
In 2016, NASA introduced the Cyclone Global Navigation Satellite System (CYGNSS). Instead of one big satellite in the sky that passes over an area twice a day, the CYGNSS are eight little satellites that work together as a constellation. These eight small satellites are low to Earth’s surface and orbit on a single launch vehicle, recording the ocean surface winds. This project, fully introduced in 2016, was created to gather more information about hurricanes, since there is no other type of instrument to gather information on the ocean so close to the eye of a tropical cyclone, hurricanes or typhoon. Since there are multiple satellites measuring just the tropics, it allows these regions to get a better picture. Each satellite passes over a region every 12 minutes, which produces a new image every few hours, compared to every few days. This fast imaginary allows scientists to get a better understanding of these rapidly changing storms.
The information that is being measured and recorded from the CYGNSSnot only allows scientists to get a better understanding of these storms but allows them to see things that they have never been able to see before. Along with the microwave signal that the CYGNSS uses to detect wind speeds, the CYGNSS also has a built-in Global Positioning Satellite, GPS (the same one used in cars), which reduces the choppiness of the ocean to help determine the wind speeds over the ocean surface. The GPS can also pick up reflections of standing water and the amount of moisture in the soil. Putting all of this information together, scientists can detect floods, a common occurrence during hurricanes.
Since hurricanes can have very rapid intensification, the old instruments used to observe them would only produce new information every two to three days, which meant that scientists were missing a lot of information. The CYGNSS allows scientists to receive data every 12 hours. This information can show how quickly an area floods during a hurricane. Since the GPS in the CYGNSS is able to pick up reflections of standing water, scientists can discover flooded areas caused by hurricanes.
This new information that is produced from the CYGNSS is groundbreaking. Since it is still new, more and more information is being discovered daily about how powerful this new satellite system really is. Scientists can spot flooding in areas that are hit by hurricanes or by overflow from rivers. Just recently scientists have been able to spot rivers off the Amazon River. Without the CYGNSS, satellites were not capable of capturing these rivers; this is due to the distance between ground and satellite. Being so close to Earth’s surface, they are able to find standing water through clouds and vegetation. The rivers they are able to see coming off the basin of the Amazon river are only hundreds of meters wide. CYGNSS principal investigator, Chris Ruf said: “When I saw the first land images of inland water bodies, I was amazed at their quality.” He continues by saying that the thought of being able to see these types of things in the past just seemed to impossible, but the high-resolution images that the CYGNSS produces are outstanding.
While all of this is still really new information, it’s something that will be useful going forward to help predict and assesses storms.
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© 2018 Weather Forecaster Allison Finch
New Improvements to the ECMWF Forecasting Package for Summer 2018 (credit: European Centre for Medium-range Weather Forecasting)
DISCUSSION: With ever-increasing processing power being made available by the world’s top scientific research supercomputers, forecasters and researchers alike are keen to stay on the cutting edge of forecasting accuracy and reliability. The European Centre for Medium-range Weather Forecasting (ECMWF) has recently announced that several new upgrades and improvements are being introduced in the latest release of the ECMWF Integrated Forecasting Package (IFS) cycle 45r1. The IFS uses a sophisticated four-dimensional data assimilation scheme (e.g., latitude-longitude-altitude-time) and is fed information from a combination of observational data and model outputs which leads to generate high-resolution forecasts. Forecasts within the IFS are further separated into two classes: a high resolution forecast and an ensemble-based forecast.
New meteorological content is being introduced in IFS cycle 45r1 that will potentially enhance forecasting skill and quality. One of the biggest improvements in this cycle is the introduction of a three-dimensional coupled ocean-atmosphere scheme with data obtained from the Nucleus of European Modeling of the Ocean (NEMO) dataset version 3.4. Because the ocean and atmosphere work consistently in tandem, coupling of the ocean-atmosphere interface is important when considering accurate simulations of future conditions. The existing NEMO-IFS scheme has also been upgraded to allow for a full ocean-atmosphere coupling in the tropics, with partial coupling in the extratropics.
Another significant improvement is with regards to the bathymetry model, which has been upgraded to use the National Oceanic and Atmospheric Administration’s ETOPO1 (1 arc-minute) locked topography-bathymetry dataset. This dataset is a significant improvement from the predecessor dataset in that many biases in estimated bathymetrical depth have been corrected for and many erroneous measurements have been addressed. The importance of this is that the wave model within the IFS can tap into this improved data and forecast accuracy of wave heights can be greatly improved as a result. The figures at the top of this article shows the adjustments to the bathymetry with ETOPO1 data compared to the predecessor dataset in both the high-resolution and ensemble wave models.
So what do these improvements mean for us? Recalling the spirit of a coupled ocean-atmosphere interface, many improvements to the upper air forecasts are expected. Understanding more about our upper-air dynamics will provide more clues on predictability of. Near-surface temperature and precipitation biases also receive an improvement on the predecessor cycle, especially in the tropical regions and over Europe. On the tropical cyclone front, intensity error has been decreased by as much as 10% over the first 5 days of a forecast and up to a 20% reduction in error beyond day 5. This is an important topic that is stressed upon global forecasters for hurricane intensity changes, especially since rapid intensification processes in tropical cyclones continue to be a challenge for forecasters and researchers alike.
While it is still currently in the open testing phase, these new upgrades are expected to be released in just a few days (June 5th, 2018). For a complete description on the new improvements, additions, and preliminary findings with the new IFS cycle besides those mentioned in this article, check out the ECMWF documentation here.
Image credit: European Centre for Medium-range Weather Forecasting
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© 2018 Meteorologist Brian Matilla
A Comparison of Men and Women Weathercasters: Education, Positions, and Presence in Local TV (Credit: American Meteorological Society)
Discussion: A study recently published in the Bulletin of the American Meteorological Society evaluated the presence, position, and education of women weathercasters in local TV. The purpose of the study was to “determine updated numbers that reflect whether women are gaining more positons and influence in local TV weather broadcasting compared to the past”. This was evaluated by examining if a correlation exists between how many female weathercasters hold meteorological degrees and are chief meteorologist. Finally, it examined if there was a correlation between having a meteorological degree and working in a larger market.
Altogether, the data were obtained between February 27 and October 20, 2016, and represented 2,040 weathercasters. Of that total, 1,444 were men and 596 were women. Local TV station personnel and websites across the U.S. provided the data for this study. Additionally, an up-to-date list of local network affiliates and regional cable channels from 210 U.S. markets was compiled via the website NewsBlues. From station websites, weathercaster biographies provided personal information including the level of education, whether or not that individual earned a degree, and their position at the station. Finally, personnel from each station provided more detailed, short biographies on news and weather team members to fill in any informational gaps.
Images 1 & 2. Data of weathercaster degrees from the recent study.
This study was one of the first to compare the number women and men weathercasters holding meteorology degrees. When polling the educational backgrounds, as seen in image 1, the majority of both male and female degrees were meteorology undergraduate degrees (778 men and 282 women). Interestingly enough, both male and female meteorology degrees were more common in smaller markets (seen in image 2). The next most common educational backgrounds included communication/journalism degrees, professional meteorology certificates such as the American Meteorological Society and National Weather Association Seals of Approval for TV Weathercasting, meteorology master’s degrees, and other science degrees.
Images 3-5. Data of the four most common positions by gender from the recent study.
Image 6. Data of chief meteorologists from the recent study.
The four most common positions of weathercasting are evening, morning, weekend, and daytime. As seen in images 3 and 5, This study found that most women weathercasters, 44%, worked the least desired and least prestigious time slot, the weekend shift. The next 37% of women worked mornings. There is a huge imbalance in the male to female ratio of evening weathercasters. 45% of men weathercasters hold this prime-time shift (images 4 and 5) while only 14% of women weathercasters work evenings (image 3). This percentage was actually lower than a previous study in 2008 that found nearly a third of women weathercasters worked in the evening/prime-time shift. Similarly, out of all chief meteorologists, only 8% are female (image 6).
Overall, this study found that the total percentage of women weathercasters in local TV has increased. Even so, women are underrepresented in the field as they mainly work undesired weekend shifts. Much fewer women than men have meteorological degrees, hold evening positions, and hold high-ranking positions including chief meteorologist. Finally, it may be useful to explore additional contributing factors for to further comprehend the results of this study.
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© 2018 Weather Forecaster Amber Liggett
DISCUSSION: In light of a gradually warming planet, there is a globally increasing concern that there could be an issue related to gradually increasing tropical cyclone intensity. This is chiefly due to the fact that as the Earth continues to experience amplified net warming over time due to an increasingly more amplified greenhouse effect, this will consequently catalyze greater global oceanic warming. The reason for this is due to the fact that well over half (50%) of the world's heat is stored in the world's oceans. Therefore, with warmer ocean's, this results in a corresponding increase in the magnitude of warmer upper-ocean heat energy which is made available on a seasonal basis to developing tropical storms.
Therefore, one of the growing concerns is that (even with all other atmospheric factors being equal such as the Coriolis force which helps dictate at what latitudinal positions tropical storms can form at) with a gradually warming planet, there would be increasing amounts of low/mid-level water vapor present. Thus, with warmer oceans, there is an inherently greater threat for potentially stronger tropical cyclones in the coming years and decades to come. Hence, it will be interesting to see if atmospheric researchers eventually make a more conscious effort to look into whether it would be advantageous to establish a slightly different (possibly with an increased intensity category) hurricane intensity scale to compensate for these factors. For the time being, the global atmospheric science community is in fairly solid agreement that the current Saffir-Simpson Hurricane Wind Intensity Scale will likely continue to be the way to go as it has worked for the global scientific and non-scientific communities alike up to this point.
To learn more about the article which inspired this article, click here!
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© 2018 Meteorologist Jordan Rabinowitz
DISCUSSION: “People generally want to know three things about any hurricane: when and where it will make landfall, and how bad will it be.” To be able to forecast and provide the public with all this information, it takes a lot of people, time, and effort to collect the data needed. This past hurricane season was ranked the fifth-most active season since records began in 1851, with 17 named storms. Regarding research during the last hurricane season, the National Hurricane Center (NHC) issued seven rapid intensification forecasts, and of which, six were correct. Periods of rapid intensification indicate that the maximum sustained winds associated with a tropical cyclone have increased by at least 30 knots (35 mph), or above, within a 24-hour period. But what is it that makes the associated hurricane research so important?
The amount of information and research on just one single hurricane can be an overwhelming amount, making the amount of information on all hurricanes mind boggling. It is this information that is collected and referenced both during and after a given tropical storm. This allows the National Oceanic and Atmospheric Administration as well as the National Hurricane Center to create models and forecasts for the public.
To understand how various hurricane research protects the public, you must understand the basics of a hurricane. Most hurricanes which form within the Tropical Atlantic basin develop within the Caribbean Sea and/or the North Atlantic Ocean. Often times, the most destructive tropical cyclones form off the coast of western Africa when thunderstorms travel westward and gradually develop an area of lower pressure near the center of the predominant convection. The localized change in minimum central pressure within the developing tropical storm catalyzes an increase in the inward rotation of the wind flow towards the center of the developing circulation.
While traveling across the warm waters over the course of what is most often several days, these storms can become very dangerous. The National Oceanic and Atmospheric Administration and NASA can collect data on these hurricanes from a combination of both satellites and aircraft. They collect information about the rainfall rates, surface wind speeds, cloud heights, environmental temperature, ocean heat, and humidity. Each of these things effect how the storm is going to evolve and how it may ultimately end up impacting people living in given regions being threatened by said storm.
One of the instruments that is deployed from aircraft(s) that fly into hurricanes is referred to as a Dropsonde. According to NASA, a Dropsonde is an 11-inch long tube that is light and flimsy. It includes a parachute to slow it down and is ejected from one such un-manned aerial vehicle which is known as the Global Hawk. While it falls, it both measures and collects formation about vertical profiles of temperature, humidity, as well as both wind speed and direction. Upon collecting this critical information, the dropsonde immediately transmits the information back to a computer.
One of the most important measurements is the wind speed. This is due to the fact that upon a hurricane hitting land, the storm surge is a direct result of how the strong the winds are. Without being able to predict strong winds in advance, affected areas can’t prepare and evacuate accordingly. The storm surge flooding can often generate life-threatening situations when not forecasted properly. Back in the day when there was a major lack of geostationary satellites and aircraft to help forecast such events, hurricanes were a much greater threat to society due to the greater lack of a more accurate predictability factor.
As someone may infer, scientific research has made substantial progress in how we forecast hurricanes. However, it is crucial to continue researching/learning more about hurricanes.
(Citied: NASA, National Weather Service, NOAA, Hurricane Hunters Association)
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© 2018 Weather Forecaster Allison Finch
DISCUSSION: As the research world wraps up neat global atmospheric events from throughout the course of 2017, one of the more interesting subjects to review is the importance of atmospheric blocking events. There is no debate that atmospheric blocking events have a profound impact on the larger-scale atmospheric flow regimes which evolve both on the synoptic-scale (i.e., spatial coverage on the order of thousands of kilometers) and the planetary scale (i.e., a spatial coverage on the order of hundreds of thousands of kilometers). Therefore, both direct and indirect impacts of atmospheric blocking events can often have incredibly far-ranging impacts on regional as well as continental weather events (and trends thereof). Attached above is a neat discussion (courtesy of Dr. Anthony Lupo of the University of Missouri) which helps to break down the duration of 2017 in the context of atmospheric blocking events and corresponding issues therein.
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© 2018 Meteorologist Anthony Lupo
Matt Bolton (my intern graduate and now professional colleague) and I have been discussing, for years, public understanding of weather. The discussion grew out of our hurricane and other research efforts, pre-college-level weather camp programs, and interactions with social scientists at professional weather conferences…Toward this end, Matt has just posted a survey (Fig. 1) to further his research…To read the full story, click here - http://www.weatherworks.com/lifelong-learning-blog/?p=1438
© 2017 H. Michael Mogil
DISCUSSION: Carbon dioxide levels hit a global record high in 2016, according to a study published by the World Meteorological Organization in the Greenhouse Gas Bulletin. Concentrations of the greenhouse gas reached 403.3 parts per million (ppm) in 2016, resulting in an increase from 400.0 ppm the prior year. Since the Industrial Revolution began around 1750, carbon dioxide concentrations have risen 145%. The study notes that “the last time concentrations were this high was at least 3 million years ago.”
It was concluded that the concentration of carbon dioxide was so high because of a combination of human activity and a particularly strong El Niño event. Although carbon dioxide emissions did slow in 2016, the El Niño event made droughts more intense and restricted vegetation from absorbing carbon dioxide from the atmosphere. Temperatures will continue to climb by the end of the century without rapids cuts in carbon dioxide and other greenhouse gas emissions.
The study can be found here.
For information on other ongoing research and other meteorological processes visit the Global Weather and Climate Center.
©2017 Meteorologist Nicholas Quaglieri
CASPER - Coupled Air Sea Processes and Electromagnetic ducting Research (Credit: Naval Postgraduate School, Monterey)
DISCUSSION: CASPER the Coupled Air Sea Processes and Electromagnetic ducting Research is a Multidisciplinary University Research Initiative (MURI) sponsored by the U.S. Office of Research and the Department of Defense. The principle investigator of CASPER is Professor Qing Wang from Monterey’s Naval Postgraduate School (NPS).
According to NPS the research objective of CASPER is to “fully characterize the Marine Atmospheric Boundary Layer (MABL) as it’s related to electromagnetic wave propagation (EM) in coastal environments.” CASPER goes on to provide details on the blending altitude sampling concept which will allow researchers to obtain critical information on, “upper ocean, surface layer, boundary layer mean profiles and boundary layer turbulence.”
Research conducted allowed students to deploy a Sensor Hosting Autonomous Remote Craft (SHARC) off the coast of California to investigate these processes. Data collected could prove to be invaluable as the US Navy wishes to further strengthen their understanding of atmospheric effects on EM.
Processes such as boundary layer mean profiles and boundary layer turbulence assist researchers like meteorologists to investigate the air layers near the surface which may be affected by the diurnal heat cycle, moisture and momentum transfers.
For information on other ongoing research and other meteorological processes visit the Global Weather and Climate Center.
©2017 Meteorologist Jessica Olsen
“Research Plan Overview.” CASPER: Overview, met.nps.edu/~qwang/casper/research/overview.php.
DISCUSSION: Attached above is a neat follow-up article to the earlier discussion (courtesy of Meteorologist Anthony Lupo from the University of Missouri) on research pertaining to atmospheric blocking events. This is a very interesting article which will give you powerful insights into the statistics surrounding global blocking events and characteristics thereof. Be sure to open the document attached above to learn more about the year of 2016 from the perspective of global atmospheric blocking events.
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©2017 Meteorologist Anthony Lupo
Insight into the Research On a Snowfall Measurement Product! (credit: Meteorologist Sheldon Kusselson)
DISCUSSION: In light of the very recently concluded winter storm which impacted many parts of the north-central United States, here is a neat piece of research work which conducted by Meteorologist Sheldon Kusselson and others which collaborated with him. Note that this product is produced by microwave sensors onboard polar orbiting satellites that sense snow in the cloud at an average resolution of 25kms and then converts to a snow-water equivalent. Many meteorologists benefit from this particular product on a relatively consistent basis during forecasts concerning winter storms.
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©2016 Meteorologist Sheldon Kusselson
DISCUSSION: Ever wonder Hurricane Sandy (October 2012) and many other events around the world unfolded in the way in which they did? Many of these events occurred in the vicinity of middle-to-upper atmospheric phenomena known as atmospheric blocking events. There is a lot of debate about what they are and Dr. Anthony Lupo (Professor at the University of Missouri) helps to break it all down in the article attached below!
To learn more about other interesting current research work being down both within and beyond the scope of the GWCC community, be sure to click here!