GLM is coming: Preparations

Creating demonstration data and products to train forecasters for GLM has presented unique challenges.  Aside from the Optical Transient Detector (OTD) and the Lightning Imaging Sensor (LIS), no other space-based platform had similar capabilities to the GLM.  Furthermore, the OTD and LIS were low-Earth orbiting instruments and would only view a small portion of the Earth for no more than a couple minutes at a time.  This prevented their use as a demonstration data set as forecasters would need to see how total lightning (the combination of intra-cloud and cloud-to-ground) evolved with time.  That put the focus on ground networks, which could observe the entire life cycle of a storm.  The ground networks, unfortunately, lacked the ability to observe total lightning (or the capability was not yet available).  The exception was the ground-based lightning mapping array.

The lightning mapping array (LMA) was developed by New Mexico Tech and evolved out of earlier systems, some of which were tested at Kennedy Space Center.  By operating in the very high frequency end of the electromagnetic spectrum (~80 GHz), the LMAs could observe the entire lightning channel within a cloud.  Primarily designed for lightning research, these would become instrumental in the training activities for the GOES-R Proving Ground and the GLM.  This is because the LMAs were capable of observing total lightning.  Their accuracy was extremely good and they have been used for ground verification for OTD and LIS and will do so again for GLM.  Their primary disadvantage is a very short range; generally no more than 200 km from the center of the network.  Figure 1 shows the physical relationship of total lightning to a storm updraft as well as the lightning jump concept.

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Figure 1:  The top two panels show the total lightning density (left) and radar reflectivity at ~20 thousand feet (right) and 1442 UTC.  The radar elevation corresponds to the mixed phase region.  Total lightning is produced by a strong, voluminous updraft extending into the mixed phase region.  This is a non-linear relationship so the strongest updrafts will produce the most lightning.  This physical connection can be harnessed by forecasters as shown in the lower left (total lightning density at 1450 UTC) and right (radar reflectivity at 20 thousand feet at 1452 UTC).  The total lightning shows a “bull’s eye” feature indicating rapid intensification, or lightning jump.  This preceded the radar update at 1452 UTC showing the updraft now extending into the mixed phase region.  This allowed the total lightning to provide additional information on the intensification of this storm and the rapid increase indicates that severe weather is imminent.  Also, the total lightning information shows the spatial extent of the lightning that can be used for safety applications.

The Melbourne, Florida forecast office was the first office to use total lightning data from a local lightning detection and ranging network (very similar to an LMA) in the late 1990s.  This was a combined effort by the forecast office, Massachusetts Institute of Technology (MIT), MIT Lincoln Lab, and NASA Marshall Space Flight Center.  The data became extremely popular with the office and the Lightning Imaging Sensor Demonstration and Display (LISDAD) system was instrumental in investigating the uses of total lightning in real-time.

In 2002, NASA’s Marshall Space Flight Center had installed the research oriented North Alabama Lightning Mapping Array (NALMA).  By March 2003, the NASA SPoRT team, in collaboration with the Huntsville weather forecast office, had made NALMA data available in the National Weather Service display system; AWIPS.  The Huntsville forecast office would then go on to issue its first warning using total lightning data that May.  NASA SPoRT would extend collaborations with a handful of other forecast offices using NALMA as well as the NASA owned Washington D.C. LMA in the late 2000s.

By 2008, the GOES-R Proving Ground was accelerating its efforts with training and hands-on activities, such as the Hazardous Weather Testbed in Norman, Oklahoma.  This required a demonstration product for GLM that could be used in real-time.  The Marshall Space Flight Center had developed the GLM proxy that was derived from NALMA to test data processing algorithms for the GLM.  The drawback was that it could not be run in real-time.  However, in 2009 NASA SPoRT produced the pseudo-GLM (PGLM) product (Figure 2).  It was not an exact replica of future GLM observations, but it represented a reasonable facsimile that allowed for hands-on training that let forecasters better learn about total lightning and its relation to storms intensity and severe weather.

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Figure 2:  An example of the pseudo-GLM flash extent density product derived from the Washington D.C. lightning mapping array during the derecho event of 2012.  The radar reflectivity (right) shows a strong line of storms approaching Washington D.C.  The greatest reflectivities (and likely strongest storms) are towards the northeast.  The pseudo-GLM (left) shows that it has update sooner than the radar, but also emphasizes the northeastern end of the line.  In fact, over 110 flashes are observed in two minutes at one location, highlighting the strongest overall storm.  The convection to the southwest is weaker as evidenced by the lack of pseudo-GLM observations.

NASA SPoRT, thanks to funding via the GOES-R visiting scientist program, was able to reach out to each of the other LMAs that were in operation across the country (and one in Canada!).  By 2014, almost a dozen LMAs were collaborating.  This allowed for the PGLM to be produced for numerous locations as well as expand partnerships to over a dozen forecast offices, three center weather service units, and the Aviation Weather Center.  Figure 3 shows the approximate domain and collaborating organization for each available LMA.  Combined, the collaborations between the forecasters, LMA owners, and the testbeds allowed for a wide variety of feedback discussing operational uses and visualization concepts.  Much of this has directly supported my own efforts as the GLM satellite liaison for the ongoing work in the Satellite Foundational Course for GOES-R, preparing for operational applications training, and the 2017 summer assessment.

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Figure 3:  The approximate domain of the 11 collaborating lightning mapping arrays that have been used as part of the GLM preparations for the GOES-R Proving Ground.  The numbers correspond to the list at top showing the owners of the collaborative network.

Next up in the “GLM is coming” series is a post describing the GLM instrument itself as we await in initial release of GLM data.

Lightning Jump in the North Alabama Lightning Mapping Array

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.

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Total lightning observations from the North Alabama Lightning Mapping Array at 2138 UTC on 22 April 2017.

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Total lightning observations from the North Alabama Lightning Mapping Array at 2152 UTC on 22 April 2017.

Total Lightning and IDSS in Stratiform Precipitation

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.

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A loop of Multi-Radar/Multi-Sensor radar imagery from 1144 UTC to 1222 UTC, 21 January 2017, with flash extent density data from the North Alabama Lightning Mapping Array overlaid in white.  The methane incident is denoted by the yellow dot in northwest Alabama, and a 10-mile range ring is indicated by the yellow circle.

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.

Utilizing Total Lightning and the Tracking Meteogram Tool to Assist in the Warning Decision Making Process

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.

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Storm Prediction Center (SPC) Convective Outlook product issued at 1z on November 2nd, 2016 (8 pm CDT on November 1st, 2016).

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).

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4-panel display of reflectivity at different tilts from KEWX radar at 8:51 pm CDT on November 1st, 2016 (0151 UTC on November 2nd, 2016).

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).

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1 minute ENTLN total lightning 5 km grid with tracking meteogram tool (left) and time series plot of total lightning for the storm of interest from 0133 UTC (8:33 pm CDT) to 0204 UTC (9:04 pm CDT) on November 2nd, 2016 (November 1st, 2016)

 

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Radar loop from KEWX from 0054 UTC (7:54 pm CDT) to 0210 UTC (9:10 pm CDT) on November 2nd, 2016 (November 1st, 2016)

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.

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Tweet posted from the NWS Austin/San Antonio twitter account shortly after the storm had passed through Austin, dropping pea sized hail.

 

NASA SPoRT Helps Prepare for GOES-R

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.

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MODIS Dust RGB demonstrating a future capability of the GOES-R ABI. Dust (magenta) can be seen approaching Las Vegas, Nevada.

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.

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Sample of the pseudo-geostationary lightning mapper demonstration product in AWIPS being used for training on the Geostationary Lightning Mapper.

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.

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GOES-R launching on November 19, 2016!

Total Lightning Data Use During Summertime Convection…

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).

Total Lightning (per North Alabama Lightning Mapping Array), 23 July 2016 2014 UTC

Image 1. Total Lightning (per North Alabama Lightning Mapping Array), 23 July 2016 2014 UTC

Image 2.

Image 2.  Total lightning (per NALMA), 23 July 2016 2022 UTC

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).

Image 3. Multi-radar Multi-sensor isothermal reflectivity (dBZ) 23 July 2016 2014 UTC

Image 3. Multi-radar Multi-sensor isothermal reflectivity (dBZ) at -20 C over portions of NW Alabama and NW Georgia, 23 July 2016 2014 UTC

 

Image 4.

Image 4.  Multi-radar Multi-sensor isothermal reflectivity (dBZ) at -20 C over portions of NE Alabama and NW Georgia, 23 July 2016 2022 UTC

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.

Total Lightning Highlights Trailing Stratiform Threat for IDSS

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.

KGWX Radar Reflectivity and North Alabama Lightning Mapping Array, valid 1949 UTC 14 July 2016

KGWX Radar Reflectivity and North Alabama Lightning Mapping Array, valid 1949 UTC 14 July 2016

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.

KGWX Radar Reflectivity and North Alabama Lightning Mapping Array, valid 2007 UTC 14 July 2016

KGWX Radar Reflectivity and North Alabama Lightning Mapping Array, valid 2007 UTC 14 July 2016

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.