Normalized Burn Ratio (NBR) Imagery in AWIPS…

Landscapes that have succumbed to wildfires, or burn scars, present especially difficult hydrologic forecasting challenges for National Weather Service (NWS) Offices since they can be conducive to the development of flash flooding and debris flows.  While the relationship between burn severity and this threat is rather complicated and dependent on a number of factors, determining the severity of the burned landscape can be important.  In order to assess this threat, professionals from a range of disciplines comprising Burned Area Emergency Response (BAER) Teams conduct intensive field surveys at the burn site.  BAER Teams conduct surveys as soon as team logistics and conditions allow, including containment levels of the wildfire (50% to 80% in many cases).  However, the threat for the development of debris flows and flash flooding can occur before these assessments can be made and as the wildfire is still actively burning.  Additionally, surveys are not conducted at all burn scars, especially in non federally-owned lands.  Traditionally, satellite imagery of burn scars has been used to help remedy this gap in knowledge about burn severity at any given location.  This imagery utilizes contrasting spectral properties between burned areas and healthy vegetation from a combination of Near-IR (~0.86 µm) and Shortwave IR (~2.25 µm) bands.  Imagery from Landsat and other high-resolution instruments has commonly been sought and used in associated analyses, but passes from high-resolution imagers can be infrequent, and cloud cover cover can obscure a single pass.  Thus, waiting periods for this type of imagery can be days to weeks depending on temporal availability of satellite passes and weather conditions.  To help with this issue, NASA SPoRT has developed the generation of NBR imagery in real-time in the Automated Weather Interactive Processing System (AWIPS) using data from the GOES-16 and GOES-17 satellites (Image 1).  Additionally, imagery from the VIIRS instrument aboard S-NPP has also been developed and transferred to AWIPS on an experimental basis.

Image 1. GOES-16 NBR imagery ((0.86 µm – 2.25 µm) / (0.86 µm + 2.25 µm)) overlaid with part transparent Visible (0.64 µm) imagery, 1751 UTC 8 Nov 2019

The compromise with GOES imagery is the lack of higher-resolution and thus detail observed in other imagery, yet analysis of a few fires so far this past fire season has indicated good agreement between GOES and VIIRS imagery.  A few examples are posted below.  Based on the color scale used, healthy/undisturbed vegetation is indicated by green colors, while burned areas appear in colors ranging from brighter yellows to oranges to reds.  The difference in resolution between the 0.86 and 2.25 µm bands in GOES-17 imagery causes “false” signatures along bodies of water.

Image 2. Woodbury Fire burn scar, GOES-17 NBR 1936 UTC 1 July 2019 (left), S-NPP NBR 1936 UTC 1 July 2019 (right), along with 2019 Fire Perimeters (black outlines)


Image 3. Kincade Fire burn scar, GOES-17 NBR 2101 UTC 7 Nov 2019 (left), S-NPP NBR 2057 UTC 7 Nov 2019 (right), along with 2019 Fire Perimeters (black outlines)


Image 4.  Recent So. California fire burn scars, GOES-17 NBR 2056 UTC 7 Nov 2019 (left), S-NPP NBR 2057 UTC 7 Nov 2019 (right), along with 2019 Fire Perimeters (black outlines)

While BAER Teams and Incident Meteorologists (IMETs) have also expressed a desire to have these types of imagery outside of AWIPS, in GIS-friendly formats, the advantage of making the imagery available in AWIPS is that forecasters can overlay it with other relevant hydrologic data sets that may help forecasters to better estimate the threat for flooding and debris flows.  Another advantage of having data generated from GOES is the high temporal resolution of the data, allowing near-continuous analysis of burn scar development as the fire is ongoing (provided clear sky conditions from clouds or smoke).

Image 5. Sample loop of the Woodbury Fire in AZ, GOES-17 NBR overlaid with partial transparent visible (0.64 µm) imagery, 2101-2251 UTC 17 June 2019.  Notice the burn scar that has already developed in western parts of the burn area (orange/yellow colors), while smoke can be seen emanating from the ongoing fire in NE parts of the fire complex (red colors).

While related development work is continuing, the SPoRT team will be discussing the potential use of this imagery with collaborative NWS offices, especially in the West CONUS,  for the next wildfire season.

-Kris W.



Reconstructing a Rare Bolt from the Blue Event Using Multiple Lightning Datasets

Reconstructing a Rare Bolt from the Blue Event Using Multiple Lightning Datasets

Written by Chris Schultz

On August 20, 2019, much of the Midwest was impacted by several rounds of severe thunderstorms.  These electrically active thunderstorms produced wind damage across Iowa, Illinois, Indiana, Ohio, Kentucky, and Missouri. However, it wasn’t the large flash rates that got the attention of those of us in SPoRT, but a rare bolt from the blue event that occurred nearly 50 miles (76 km) outside any surface precipitation.

During the 40 minutes leading up to the lightning event, the closest thunderstorm activity was located approximately 50 miles south of Dittmer, MO, across parts of Phelps, Dent, Washington, St. Francois, and Ste. Genevieve Counties (Fig. 1A).   Between 400 pm and 440 pm CDT zero lightning flashes occurred in Franklin, Jefferson, Warren, or St. Charles Co., MO (Fig. 1B).

Figure 1 – A- Radar reflectivity at 0.4 degrees elevation at 2140 UTC from KLSX in Weldon Spring MO, and  B- NLDN lightning detections between 21:00:00 and 21:40:16 UTC (4:00:00-4:40:00 pm CDT).

Then at 4:40:15 pm CDT, a positive lightning flash was observed by Vaisala’s National Lightning Detection Network well outside of any precipitation (Fig. 2).  This flash was positive polarity, was approximately 136 kiloamps, and located in an area that had not observed any lightning in the previous 40 minutes. This +CG flash was accompanied by 5 additional incloud flash detections, and one negative cloud to ground flash detection by the NLDN.  All 7 detections occurred within 1 second of each other, indicating that they were part of the same lightning event.  However, the question remained, where did this flash originate? Radar and previous lightning data from the NLDN indicate that there are 2-3 areas of thunderstorm activity to the south of this location which could be a possible origination point. But there wasn’t a definitive prospect because the NLDN point locations are spatially separated by several miles. 

Figure 2 – Radar reflectivity at 0.4 degrees elevation at 2140 UTC from KLSX in Weldon Spring MO (A) and NLDN lightning detections at 21:40:15 UTC (4:40:15 pm CDT).

Bringing in Geostationary Lightning Mapper Flash Extent Density data product for the same point in time (Fig. 3), there is a better idea of which thunderstorm this flash originated from.  There is a distinct lightning path from the thunderstorms over Dent and Phelps Counties in up to the NLDN flash locations in Jefferson and Franklin Counties. This single flash travelled nearly 57 miles (~ 92 km) from its original start location to the ground location, and actually propagated further north into Warren and St. Charles Counties.  

Figure 3 – GOES GLM Flash Extent Density overlaid on 0.64 µm ABI data at 2141 UTC (441 pm CDT).

Taking a vertical slice of the radar data between the parent thunderstorm and the location where the flash came to ground, there is a distinct path of precipitation aloft between 20,000 and 30,000 ft (Fig. 4).  Thus the lightning traveled through an anvil region before coming to ground approximately 41 miles (76 km) outside of the main precipitation near the surface.  Large bolt from the blue events have been reported in the literature previously (e.g., Kuhlman et al. 2009, Weiss et al. 2012, Lang et al. 2016). This flash was also a unique event because any lightning safety protocols would not have been in place for the location due to the absence of lightning within 6 miles during the previous 40 minutes.

Figure 4 – A vertical cross section of reflectivity from KLSX at 2140 UTC (440 pm CDT)

When GLM data are combined with ground based lightning networks like the NLDN or Earth Networks Total Lightning Network, the GLM Flash Extent Density can be used to connect point locations and determine where additional electrification may be present aloft that is not readily apparent at the surface.

SPoRT LIS Shows Dry Soils During High Plains Blowing Dust Event…

Yesterday while working on some Dust RGB related training materials, I was looking at the RGB in AWIPS and noticed a dust event unfolding in real-time in the central High Plains.  The loop below shows Dust RGB imagery, generated by GOES-East, yesterday, 28 Jan 2019 during the late morning and early afternoon hours.  The loop is centered over NE Colorado and SW Nebraska where you’ll see the blowing dust develop and spread southeastward.  In case you’re not too familiar with this type of imagery, the dust is represented by the magenta colors.  It’s also possible to observe some of the individual dust streaks or plumes within the larger blowing dust event, which help to show their locations of origin.  (By the way, sorry about the loss of image fidelity when saving from AWIPS to an animated GIF).

Image 1.  GOES-East Dust RGB imagery, approx. 1737-2002 UTC, 28 Jan 2019. The blowing dust is defined by the magenta colors, near the center of the imagery.

Research has shown that it takes the right combination of factors to loft dust particles sufficiently to generate these larger scale blowing dust events, partly based on soil moisture and winds.  The SPoRT LIS 0-10 cm volumetric soil moisture (VSM) analysis at 18 UTC indicated very low values in the blowing dust source region, with VSM percentages generally around 12-16% (Image 2).  The METAR observations also indicate sustained winds were 35-40 knots with stronger gusts over 40 knots at one locations in the area.

Image 2. SPoRT LIS volumetric soil moisture (background colors) overlaid with surface METAR plots (yellow figures), valid at 18 UTC, 28 Jan 2019.

This last image is a snapshot of the Dust RGB taken at 1902 UTC, overlaid with surface visibility and ceiling observations.  Notice that at station KHEQ in far northeastern Colorado, a ceiling of 100 ft and visibility of 7 SM was reported, which was likely due to the blowing dust.

Image 3. GOES-East Dust RGB and ceiling and visibility observations from ground observation stations at approximately 19 UTC, 28 Jan 2019.

Some SPoRT collaborative NWS offices in the West CONUS have utilized LIS VSM values to locate areas where the probability of blowing dust events is heightened under the proper conditions.  However, SPoRT is looking into opportunities to better predict where these events will occur.

Fog at Sunrise with RGBs using Visible Imagery

Fog at Sunrise with RGBs using Visible Imagery


Nighttime Microphysics RGB via GOES-16 at 1122 UTC, 13 August 2018 over the Southeast U.S.

During the early morning of 13 August 2018, clear skies resulted in wide spread low clouds and fog over the East/Southeast.  The image above is the Nighttime Microphysics (NtMicro) RGB via GOES-16 at 1122 UTC or 7:22 and 6:22 AM for Eastern and Central times respectively.  At this time the low clouds and fog in shades of cyan are still apparent, but soon this coloring will fade as solar reflectance at sunrise will influence the shortwave IR used in the RGB and therefore, the NtMicro will be rendered ineffective (see mp4 animation).  Typically, visible imagery is used at sunrise to continue to monitor fog in small-scale valleys, often with a lack of in situ observations.  The new capabilities of GOES-16 provide new RGBs for daytime use that include the 0.64 micron visible channel.  The Natural Color RGB, originally developed by EUMETSAT is available within AWIPS (as ‘Day Land Cloud’), and it uses the visible channel in it’s blue component.  Below is a slide show of the NtMicro, Natural Color and Visible RGBs just after sunrise (1222 UTC).  Note that the Natural Color RGB (also see mp4 animation) shows the fog and water clouds in gray while ice clouds are in cyan.  The Natural Color RGB can be used through the day to monitor the microphysics of cloud tops due to the use of the 1.61 micron channel, and it also provides qualitative land surface information via the 0.87 micron channel.   A legacy ‘Visible’ RGB (also see mp4 animation) that uses the visible in the red and green components (‘Day Land Convection’ within AWIPS), also provides value to monitor fog after sunrise as it depicts warm clouds in yellows and cold clouds in grays to white in daytime.

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Geostationary Lightning Mapper (GLM) observes three tropical cyclones in the eastern Pacific

The large field of view of the Geostationary Lightning Mapper (GLM) offers forecasters a new way to monitor tropical cyclones.  In particular, the GLM will offer the opportunity to monitor total lightning (i.e., cloud-to-ground and intra-cloud) trends over the entire life cycle of the system.

The past few days have offered a very interesting opportunity with three tropical cyclones in the eastern Pacific basin; Tropical Storm Greg, Hurricane Hilary, and Tropical Storm Irwin.  The movie covers from 1310 UTC on July 23 through 1610 UTC on July 24.  A few features are interesting to point out.  First, notice the amount of lightning activity and diurnal change associated with the storms across Mexico (upper right of movie) versus the activity with the three tropical systems.  Also, check out the location of the lightning in tropical systems and whether it is in the central core or the outer bands.

Figure 1 is a still from the linked mp4 movie that is approximately 37 megabytes in size.


Figure 1:  A still image from 0600 UTC on 24 July 2017 showing Tropical Storms Greg and Irwin as well as Hurricane Hilary in the eastern Pacific basin.  The cyclones are viewed with ABI at the full disk, 15 minute temporal resolution (and intentionally darkened to make the lightning observations stand out) and the GLM 8 km, 5 minute group densities. (Please click on image to enlarge.)

[37 MB] GLM group density over three tropical cyclones

NOTE:  NOAA’s GOES-16 satellite has not been declared operational and its data are preliminary and undergoing testing. Users receiving these data through any dissemination means  (including, but not limited to, PDA and GRB) assume all risk related to their use of GOES-16 data and NOAA disclaims any and all warranties, whether express or implied, including (without limitation) any implied warranties of merchantability or fitness for a particular purpose.