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Archive for the ‘Lightning Mapping Array’ Category

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.

methaneexplosion

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.

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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.

image2

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.

goes_r_launch_19nov16

GOES-R launching on November 19, 2016!

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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.

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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.

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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.

Demonstration total lightning web display

The North Alabama Lightning Mapping Array flash extent density animation from 1:30-4:00 PM (Central) on July 1, 2015 in a new demonstration web display.  State and county boundaries are in black, while interstates are blue and major U.S. highways are in red.  (Click for the full resolution image.)

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.

A still taken from the animation above at 2:14 PM (Central).  The main storm core and stratiform region lightning are highlighted.

A still taken from the animation above at 2:14 PM (Central). The main storm core and stratiform region lightning are highlighted. (Click for the full resolution image.)

 

The corresponding radar reflectivity at 2:14 PM (Central) for the still image above highlighting the locations of the total lightning features.

The corresponding radar reflectivity at 2:14 PM (Central) for the still image above highlighting the locations of the total lightning features. (Click for the full resolution image.)

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The Huntsville office has a long history of using total lightning information from the North Alabama Lightning Mapping Array (NALMA) for warning decision-making.  Since 2003, WFO Huntsville has been ingesting and receiving a source density product from NASA SPoRT.  However, recently, we decided to begin migrating to Flash Extent Density (FED) data; this is more consistent with the Geostationary Lightning Mapper, more consistent with recent operational research, and easier to convey and understand.  Typically we are trying to apply the “two-sigma” lightning jump algorithm suggested by Schultz et al. (2009, 2012).

On June 8, a weak front moved across the Huntsville forecast area, initiating development of strong to severe thunderstorms.  An 1800 UTC sounding from Redstone Arsenal indicated a relatively high threat for wet microbursts.

One of the storms moved across extreme southern Jackson and northern DeKalb Counties in northeast Alabama.  I was viewing the NALMA FED data and watched as the storm went from less than 10 flashes, to 40 flashes, in three “scans” (from 2214 to 2218 UTC).  (Interestingly, despite using SAILS with the KHTX radar, AWIPS-2 matched all three lightning images to a single 0.5-degree radar scan.)

2015-06-08-2214

Fig. 1: KHTX Reflectivity valid 2215 UTC and NALMA FED valid 2214 UTC 8 June 2015

Fig. 2: KHTX Reflectivity valid 2215 UTC and NALMA FED valid 2216 UTC 8 June 2015

Fig. 2: KHTX Reflectivity valid 2215 UTC and NALMA FED valid 2216 UTC 8 June 2015

Fig. 3: KHTX Reflectivity valid 2215 UTC and NALMA FED valid 2218 UTC 8 June 2015

Fig. 3: KHTX Reflectivity valid 2215 UTC and NALMA FED valid 2218 UTC 8 June 2015

Since we cannot get the formal lightning jump algorithm into AWIPS-2 at this time, forecasters need to do some quick mental math to decide if jumps such as these constitute a real jump.  I was certain this did (and later Excel work verified this) so I issued a severe thunderstorm warning, despite the storm being very close to the Georgia state border.

This storm produced structural damage in the Cartersville community near the state line shortly after the warning was issued, tearing the roof off of an apartment complex and downing trees and powerlines.  There was not much lead time (there rarely is with these kinds of storms) but this reinforces our past experience with total lightning–and reinforces that lightning may be especially useful during a challenging warm season warning environment.

 

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On the evening of Monday, October 6th, several severe thunderstorms producing large hail moved across the Tennessee Valley region.  I, along with another colleague, was on the radar desk for severe weather operations at the Huntsville, AL Weather Forecast Office.  Some thunderstorms in the region had already produced large hail up to the size of golf balls to our north.  As a vigorous short wave moved through the region, leading to increased lapse rates and deep layer shear, the threat for large hail was expected to continue into the early evening hours.  As usual here at the Huntsville WFO, total lightning data from the North Alabama Lightning Mapping Array (NALMA) were incorporated into our warning decision process.

At 548 pm CDT, my colleague  issued an initial severe thunderstorm warning for a storm cell located over northwestern portions of Jackson County, AL, primarily for the expectations of large hail.  Reflectivity from the KHTX radar and the initial polygon can be seen below in image 1.

Reflectivity0.5_JacksonCounty_Oct62014-7

Image 1.  KHTX 0.5 degree reflectivity (dBZ) with warning polygon issued at 2248 UTC (548 pm CDT) 6 Oct 2014. The black circle near the top center of the image is the KHTX “cone of silence”.

I had taken over warning responsibility for this severe thunderstorm by 6 pm and was having to decide whether or not to continue the warning when it expired at 615 pm CDT.  This storm was tracking very close to the KHTX radar (noted by the black circle) and it was difficult to make out some of its higher level features and characteristics (although the Advanced Radar for Meteorological and Operational Research (ARMOR) was also being utilized at this point).   The storm had wavered in intensity since the warning issuance and was only expected to be at the low-end of severe criteria.  Another factor complicating the warning decision was that this storm was tracking over an area with very low population density.  So, severe weather reports providing ground-truth were difficult to come by, and in fact, we had not received any yet allowing for verification of the warning.

Nevertheless, this is where the NALMA data came into play.  Just shortly after the severe thunderstorm issuance, source densities within the storm surged, with values reaching well over 400 sources (image 2) between 550 and 552 pm CDT.

Source density values from the North Alabama Lightning Mapping Array, 2-min period ending 552 pm CDT (2252 UTC) 6 October 2014.

Image 2. Source density values from the North Alabama Lightning Mapping Array, 2-min period ending 552 pm CDT (2252 UTC) 6 October 2014.

 

Over the next series of updates from the NALMA, source densities maintained relatively high values.  As late as 2302 UTC, when I was beginning to consider the continuance of the warning, source values were still around 400 or higher.  Afterward, values did gradually decrease.  However, with the understanding that hail production will take some time following the strengthening updraft and that severe weather may not manifest up to about 30 minutes (or longer in some cases) after sustained surges in total lightning, I decided to continue the warning (Image 3).  As the storm continued eastward, we finally received our first reports of one inch diameter hail in the town of Stevenson.  Interestingly, the hail accumulated to the depth of a few inches according to one report.

So, yet again, this was another case in which total lightning provided value-added data and significant help for an operational warning decision.

Stevenson

Image 3. KHTX 0.5 degree reflectivity with warning polygon (yellow), valid 617 pm CDT 6 October 2014. The town of Stevenson, AL is highlighted where one inch diameter hail was reported covering portions of Hwy 72.

 

 

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