It’s a busy day in North Alabama with NASA and NOAA aircraft in the region supporting a field campaign for GOES-16. Another instrument supporting activities is the North Alabama Lightning Mapping Array (NALMA), which observes total lightning (both intra-cloud and cloud-to-ground). SPoRT has been providing NALMA data to local forecast offices for 14 years and has used these data to serve as a proxy for the Geostationary Lightning Mapper on GOES-16 as part of the GOES-R Proving Ground. The images below show the total lightning activity across southern Tennessee and northern Alabama at 2138 and 2152 UTC on 22 April 2017. The main storm of interest is right along the Alabama-Tennessee border, just north of Huntsville, Alabama. The maximum number of flashes per 2 square kilometers in two minutes is about 50 flashes at 2138. In 14 minutes, that has jumped to nearly 150 flashes over two minutes highlighting a lightning jump. A long flash extending to the south towards Huntsville is also seen. This storm already had a severe thunderstorm warning active and the jump here indicates that the storm will maintain it’s intensity. The weather community will look forward to the Geostationary Lightning Mapper observations when they a made available in the next few months.
A methane explosion occurred last Friday, January 20, in rural northwest Alabama (story from WAFF-TV). NWS Huntsville provided decision support services to the incident, which posed significant risks to emergency personnel. The active pattern last weekend created additional concerns, since several rounds of rain and thunderstorms were forecast to move across the area (though fortunately the significant severe weather from that weekend remained well to the south).
One such event arrived Saturday morning as stratiform rain pushed back into the area. Forecasters noted that there were indications of cloud-to-ground lightning from the National Lightning Detection Network along the leading edge of the rainfall, so we leveraged flash extent density data from the North Alabama Lightning Mapping Array to investigate further. Strangely, when loaded as an image in AWIPS-2, this showed little.
It took some time to discover why. The flash rates were so low (1 flash per ‘scan’) that the FED image interpolation was smoothing the data below what the color curve could visualize. After the interpolation was turned off or the color curve edited again, the flashes were much more apparent, as seen in the following GIF loop from AWIPS.
Adding the full flash extent density information from the NALMA helped the forecasters to visualize the lightning threat beyond what was otherwise available in AWIPS. This helped when it came time to brief emergency personnel on the approaching threat.
This event also helps to reinforce the potential utility of the Geostationary Lightning Mapper (GLM) aboard GOES-16 as it becomes available this spring. However, forecasters will have to visualize the GLM data wisely. It will likely more important to view low flash rates for an IDSS or safety mindset, versus higher flash rate changes for severe weather. Even with total lightning, context is everything.
Herein is an example of the Tracking Meteogram Tool, which was developed by NASA SPoRT, being used to track and create a time series plot of the total lightning associated with a thunderstorm at the National Weather Service forecast office in New Braunfels, TX (Austin/San Antonio – EWX). The information gleaned by the time series plot from the tracking meteogram tool assisted in the warning decision making process.
For full disclosure, I have a background in total lightning and its operational uses in severe weather operations. My Master’s thesis at the University of Alabama in Huntsville was on the utility of total lightning and the lightning jump to assist in the quasi-linear convective system (QLCS) tornado warning decision process. Also, as a CIMMS research associate at the NWS Warning Decision Training Division, I developed a four-part series on best practices for using total lightning to assist in storm interrogation for various convective modes and severe hazards. I have been an intern at the NWS forecast office in New Braunfels, TX since May 2016.
On the evening of November 1st, 2016, there were isolated thunderstorms in the forecast across the Interstate 35 corridor between San Antonio and Austin, but severe weather of any sort was not anticipated across our area. The Storm Prediction Center convective outlook highlighted the eastern half of our CWA for possible thunderstorms, but did not have even a marginal risk area outlined.
On this particular shift, I was working the public service desk, while my colleague Nick Hampshire, a lead forecaster at EWX, was working the short-term forecast desk. Given my background in total lightning, I typically overlay the one minute 5 km by 5 km Earth Networks Total Lightning Detection Network (ENTLN) total lightning product on top of reflectivity for situational awareness purposes. Isolated showers and thunderstorms began initiating across the region around 6-7 pm that evening. These showers and storms were, as expected, fairly mundane and short lived, only producing light to moderate rainfall before the updraft was cut off and the storm dissipated. When the showers did manage to produce lightning, the lightning frequency was low and short lived.
Around 7:40 pm, a shower initiated east of Seguin, moving northward toward the cities of San Marcos and Austin. By the time it reached San Marcos around 8:20 pm, the shower began producing lightning. As the storm progressed northward toward the city of Austin, the total lightning flash rates continued to increase. To monitor the time series trend of the total flash rate, I used the Tracking Meteogram Tool and configured it to display the sum of the values, thereby plotting all the lightning being produced by the storm at any one time. I noticed a steady increase in the lightning flash rate that coincided with and even slightly preceded the strengthening of the storm as determined by radar signatures. A quick interrogation using radar and the standard environmental package from LAPS of the storm at around 8:51 pm showed 50+ dBZ echoes up to beyond the -30 degree Celsius level (~30,000 feet).
The total flash rate at this time was 46 flashes per minute, and the flash rate had increased from 34 flashes per minute at 8:47 pm to a local maximum of 47 flashes per minute at 8:52 pm. Given the radar signatures as well as the rapid increasing trend in total flash rate, Mr. Hampshire and I decided that a Significant Weather Advisory was warranted. In the text product, we mentioned pea to nickel sized hail associated with this storm. The SPS was issued around 8:52 pm. We received a few reports of pea sized hail in southwest Austin on social media shortly after 9 pm (2z).
This case demonstrated the value of total lightning and the tracking meteogram tool. Given the forecast and the atmospheric environment, severe weather was not anticipated. However, it was the large, rapid increase in total lightning that initially prompted my attention to this storm and caused me to delve further into interrogating the severe potential. Had I not had the total lightning information available to me, the Significant Weather Advisory almost certainly would have come out later and perhaps not at all. Granted, this storm did not meet severe criteria, but not having any product issued for pea sized hail when hail of any size was not in the forecast would not have been an ideal situation, and the value added from the total lightning was still noteworthy.
November 19th has been eagerly anticipated by the meteorological community as it is the launch of the next-generation GOES-R satellite. The satellite will carry a suite of space weather instruments as well as two Earth observing sensors. The Advanced Baseline Imager (ABI) will provide three times more channels to view the Earth, four times greater spatial resolution, and 5 times faster coverage. The ABI will provide new means to monitor atmospheric phenomena. Additionally, GOES-R will carry the first ever lightning observation sensor on a geostationary platform; the Geostationary Lightning Mapper (GLM). Numerous organizations, including NASA SPoRT, have been supporting the GOES-R Proving Ground for many years to aid the operational community in preparing for the new capabilities of GOES-R.
Specifically, NASA SPoRT has been formally involved with the Proving Ground since 2009, although much of our work prior to this point has provided relevant information with respect to GOES-R. SPoRT has been primarily involved in two activities. The first has been the assessment of and training for multi-spectral imagery, often called red-green-blue (RGB) composites. The RGB composites are used to combine multiple single channels into a single image in order to help emphasize phenomena that forecasters wish to monitor. This can range from air mass microphysics to atmospheric dust. This work has leveraged work by Europe’s EUMETSAT organization who first developed several of these RGB composites for their Meteosat Second Generation satellite. SPoRT has worked with NASA’s MODIS instruments from Aqua and Terra as well as the JPSS VIIRS instrument to create the respective RGBs from polar orbiting instruments. These snapshot demonstrations provided forecasters local examples of RGB composites to allow them to investigate these products prior to GOES-R’s launch. SPoRT has also coordinated with other product developers to help transition their early development work to National Weather Service forecasters. This included the University of Alabama in Huntsville’s GOES-R convective initiation product and the NESDIS quantitative precipitation product.
In additional to the ABI work, SPoRT has been integral to supporting total lightning (intra-cloud and cloud-to-ground) observations in operational applications. This dates back to 2003 with the first transition of experimental ground-based lightning mapping arrays that evolved into the pseudo-geostationary lightning mapper (PGLM) product in 2009 to provide operational training for the GLM. Since then, SPoRT has developed the GLM plug-in for the National Weather Service’s AWIPS system, has personnel serving as the National Weather Service liaison for the GLM, and have developed foundational training that is being provided to every forecaster in the National Weather Service.
SPoRT will continue to be actively engaged in GOES-R applications post launch. This will take the form of developing an applications library, or short 3-5 focused case examples, for both the ABI RGBs and the GLM. SPoRT will also participate in the formal applications training for RGBs and GLM that will be released to the National Weather Service. Lastly, SPoRT will be leading an operational assessment of the GLM with National Weather Service forecasters and associated emergency managers.
Here at the Huntsville, AL Weather Forecast Office (WFO) we’ve pointed out total lightning data’s operational utility a number of times in this blog. After all, the data have been a rather integral part of our severe weather operations for at least 13 years. Anyway…I’m going to do it again. I think it can be beneficial to reiterate the value of certain data sets from time to time, especially to reemphasize their operational utility to new members of the forecasting and research community and perhaps newcomers to the SPoRT blog.
This afternoon and evening was a somewhat typical summertime convective event for the Tennessee Valley. Showers and thunderstorms developed in the early afternoon and gradually increased in coverage and intensity during the mid to late afternoon hours. By the time I arrived on shift at about 3 pm CDT, a few thunderstorms were showing signs of intense updrafts (~50 dBZ at the -10C isotherm level), but were still not to the level of producing severe weather. Nevertheless, multiple outflow boundaries interacting with the hot, humid and unstable airmass caused decent coverage of shower and thunderstorm activity, especially in northeastern portions of Alabama during the mid afternoon into the early evening. A few thunderstorms contained strong updrafts, heavy rainfall, frequent lightning and wind gusts up to about 40 mph. The first of these started showing signs of strengthening in eastern portions of DeKalb County, AL shortly after 3 pm CDT. The first image below (image 1) shows a snapshot of total lightning data (flash extent density) from the North Alabama Lightning Mapping Array (NALMA) at 2014 UTC. Values at this time in the developing storm were just around 10 flashes per 2-minutes. By 2022 UTC however, flashes had increased to nearly 50 flashes per 2-minutes (Image 2).
Importantly, increases in total lightning activity are directly related to updraft strength within storm cells so it was no surprise that reflectivity values increased correspondingly. The next two images show the increases in Multi-radar Multi-sensor (MRMS) isothermal reflectivity (dBZ) at the -20 C level during the same period (Images 3 and 4).
Data such as the MRMS isothermal reflectivity when used in conjunction with other data such as total lightning (or flash extent density) allow for a good evaluation of updraft development within thunderstorms and their evolution through time. Environmental parameters on this day suggested that severe weather was not likely. Nevertheless, the strengthening updrafts were followed by wind gusts around 30 to 40 mph, which were recorded at a few of our surface observation sites. Special Weather Statements were used to address this marginal thunderstorm threat during the afternoon and evening. Interestingly, notice that the total lightning data at 2022 UTC (Image 2) indicated that the updraft in the northern cell in DeKalb County was perhaps the strongest at the time (due to higher values on flash extent density), while MRMS reflectivity values were higher at the same time in the southern cell (image 4). Subsequently, the northern cell strengthened and became the dominant cell over the next 30 minutes. On days such as this when there are often multiple thunderstorms ongoing at any one time, and this happens often here in the TN Valley in the summertime, total lightning data can be an effective situational awareness tool for evaluating storms that are undergoing strengthening and helping to provide proper focus for operational meteorologists.
NWS Huntsville is providing Impact-Based Decision Support Services (IDSS) to protect life and property at an outdoor sporting competition in the Decatur, Alabama area this week. A decaying Mesoscale Convective System (MCS) moved across north Alabama this afternoon, forcing a delay in the competition for several hours. While the North Alabama Lightning Mapping Array (NALMA) helped determine what to tell local emergency managers about the start of the lightning threat, the NALMA really shined in trying to figure out when the lightning threat would end.
The example images include NALMA Flash Extent Density data, which are represented by irregular pink and purple shapes displayed over the KGWX radar reflectivity. Both the 1949 and 2007 UTC indicate scattered very low flash rates extending over a broad area–including the Decatur area–suggesting occasional in-cloud flashes within the trailing stratiform region of the MCS. This is a known threat with MCSs, but it was not clear at the time how long the lightning threat would persist. Use of total lightning information from NALMA enabled NWS Huntsville staff to determine that the lightning threat would not subside until rain subsided.
With the launch of GOES-R and the Geostationary Lightning Mapper, these kinds of data will improve lightning-based IDSS across a much wider cross section of the CONUS.
The SPoRT Center regularly works to display unique data in products, such as total lightning from ground-based lightning mapping arrays (LMAs), in the Weather Service’s display system; AWIPS II. However, there is occasionally an opportunity to try a different method for specific operational applications. One of those opportunities came with the Morristown, Tennessee forecast office. Here, the collaboration was looking for a web-based visualization in order to better collaborate with emergency managers. Feedback to SPoRT requested the need for a real-time display that could animate the data, auto-update, and allow zooming to a feature that would not reset with an update. Additionally, there was a need to make this functional on mobile devices.
This has resulted in the test display shown here of the North Alabama Lightning Mapping Array flash extent density from July 1, 2015 from 1:30-4:00 PM (Central). Like the more traditional display in AWIPS II, this flash extent density highlights the main storm cores where the updraft is intensifying, shows the spatial extent of total lightning, and even highlights several long flashes into the stratiform region behind the main convection, as shown in the still images below. While the display is just in a development state now, it is demonstrating the potential for how to bring these data to emergency managers and Weather Service forecasters who may be in the field and not in the office, such as for special outdoor events.
The two images below show a still image from 2:14 PM (Central) of the total lightning flash extent density and the corresponding radar reflectivity.