Tropical Cyclone Dorian become a hurricane on 28 August 2019. By the early morning of the 29th, the Dorian remained a category 1 hurricane as it advanced to the northwest, north of Puerto Rico.
GOES-East IR imagery and Sea Surface Temperature derived product with NHC forecast track overlay show the hurricane expected to continue through very warm waters as it approaches the Florida East Coast (Fig 1). Temperatures are between 29C and 30C along the track, or around 85F.
Figure 1: 29 August 2019 GOES-East 5-min IR, 1-hr SST, NHC forecast track. Full res
A 1-min mesoscale sector from GOES-East was available over the system. The high resolution imagery aids forecasters in identifying the center of circulation, as well as in tracking thunderstorm activity. Visible imagery with a semi-transparent GLM Flash Extent Density overlay at sunrise on the 29th clearly showed the center of circulation, with areas of thunderstorms, some strong, embedded in the outer bands (Fig 2).
Figure 2: 29 August 2019 GOES-East 1-min VIS, GLM FED. Full res
Zoom in view on center of circulation at sunrise Fig 3).
Figure 3: 29 August 2019 GOES-East 1-min VIS zoom in on Dorian center of circulation. Full res
The strong thunderstorm just northeast of the center of circulation exhibited high flash rates (see Fig 2) as well as persistent overshooting tops and even an above anvil cirrus plume, much like we see with strong thunderstorms over the CONUS (Fig 4).
Figure 4: 29 August 2019 GOES-East 1-min VIS zoom in on strong thunderstorm northeast of Dorian center of circulation. Full res
Thunderstorms developed along a SW-NE oriented boundary draped across north-central Oklahoma during the early evening hours of 26 Aug 2019. The storms quickly grew upscale into a Mesoscale Convective System (MCS), and tracked south through central Oklahoma during the night, producing strong/damaging wind gusts and large hail.
One-minute visible imagery from GOES-East clearly shows convergence along a boundary, development of towering cu along the boundary, and eventual convective initiation (Fig 1), all in real-time. Storms quickly reached the equilibrium level and developed overshooting tops (OTs) and above anvil cirrus plumes, indicating particularly robust updrafts. Given the time of day around sunset, the shadows cast on the anvil provide additional insight into the vertical extent of the OTs.
Figure 1: 26 August 2019 GOES-East 1-min VIS. Full res
GOES-East IR imagery showed rapid cooling of cloud tops as well as the development of overshooting tops (Fig 2). One method for viewing GOES imagery and GLM fields together in one display is to create a GLM contour color table. Since GLM fields are not gridded data in AWIPS, one cannot easily change it to a contoured field. However, the user can create a color table that implements contours at chosen thresholds instead of a constant fill. This display allows one to view VIS or colored IR imagery and GLM FED data in one display, not needing to make the GLM field semi-transparent. The GLM color table in this example includes three thresholds: 1 Flash/5-min (blue), 25 Flashes/5-min (Cyan), 100 Flashes/5-min (Yellow). For the most part, these solid color contours stand out and do not interfere with the IR colors.
Figure 2: 26 August 2019 GOES-East IR, GLM FED contours. Full res
Very deep convection developed over the western Mexico near the Gulf of California during the late afternoon hours of 20 August 2019, lasting into the early evening. This area of convection produced overshooting tops with IR brightness temperatures less than -90C (Fig 1)!
Figure 1: 20 August 2019 GOES-East IR of storms over western Mexico. Full res
Analyzing a nearby sounding, these storms developed in an extremely moist environment (TPW=2.49″), very strong instability (MLCAPE = 4660 j/kg) and a very high equilibrium level (around 16.5 km). Based on the sounding, the -90C observed IR brightness temperatures likely put the OTs over 17.5 km above the surface!
Figure 2: 00Z 21 August 2019 observed sounding over western Mexico. Full res
Corresponding visible imagery of one of the storms is equally impressive. The final frame shows an OT penetrating deep across the equilibrium level casting an obvious shadow on the anvil (Fig 3).
Figure 3: 20 August 2019 GOES-East VIS of convection over western Mexico. Full res
Finally, a VIS/IR comparison of a -90C OT (FIg 4).
Figure 4: 2356Z 20 August 2019 GOES-East VIS and IR of convection over western Mexico. Full res
A severe thunderstorm developed quickly in the Pueblo, CO area during the early evening of 10 August 2019. GOES-16 imagery and lightning data provided clues to a rapidly intensifying thunderstorm with the potential to be strong to severe. While the environment was not all that supportive of large hail, steep low-level lapse rates and anomalously high Total Precipitable Water (TPW) values (~130% of normal) indicated the potential for strong downdraft wind gusts and heavy rainfall. Indeed, there were reports of heavy rain with this storm, as well as a 76 mph wind gust recorded at KPUB Pueblo ASOS (Fig 1). One-minute satellite imagery was available to forecasters during this event.
Figure 1: 10 August 2019 5-min PUB ASOS data, during period of satellite animations below. Higher res
Analyzing 1-min visible and IR imagery from GOES-East over a 99-min period, we see several areas of cu initiate in the moist environment just west of Pueblo before organizing into into a single strong updraft (Fig 2 and 3). The updraft quickly reaches the tropopause and spreads out radially. An overshooting top is first apparent around 0000Z, while an above anvil cirrus plume starts to become noticeable after 0015Z.
Figure 2: 10 August 2019 GOES-East 1-min VIS imagery with heavy rain and 76 mph wind gust LSRs overlaid. Higher resFigure 3: 10 August 2019 GOES-East 1-min IR imagery with heavy rain and 76 mph wind gust LSRs overlaid. Higher res
The sandwich RGB combines the VIS and IR into a single image (Fig 4) into a single high-resolution qualitative product.
Figure 4: 10 August 2019 GOES-East 1-min Sandwich RGB imagery with heavy rain and 76 mph wind gust LSRs overlaid. Higher res
Looking at semi-transparent GLM Flash Extent Density (5-min accumulation updating every 1-min) gridded product overlaid on the VIS, we diagnose a rapid increase in total lightning between 2335Z and 2344Z (7 fl/5-min to 31 fl/5-min), or a lightning jump (Fig 5). This jump is an indicator of a strengthening updraft and often a precursor to hazardous weather at the surface. Cloud tops cooled from -45C to -64C during the same 9-min period. Lightning activity remained relatively stable through around 0000Z, while cloud tops continued to cool. Between 2345Z and 0000Z (after the lightning jump and during the continued cloud top cooling), very heavy rainfall (at least ~0.5 inches in 15 min) and gusty winds (estimated around 50 mph) were reported with this storm, in addition to improved presentation in radar imagery.
Figure 5: 10 August 2019 GOES-East 1-min visible imagery and GLM Flash Extent Density (5-min accumulation updating every 1-min) with heavy rain and 76 mph wind gust LSRs overlaid. Higher res
A second lightning jump occurred between 0002Z and 00009Z when FED increased from 23 fl/5-min to 56 fl/5-min). Cloud top temperatures bottomed out at around -76C at this time as well. During this lightning jump, very strong winds associated with the storm were measured at the surface, including the first severe wind gust of 59 mph at 0008 UTC, the first significant severe gust of 75 mph at 00010 UTC, and maxing out at 76 mph at 0016 UTC. The storm advanced into primarily rural areas thereafter, with lightning activity slowly dropping off, and cloud tops warming. See graph of IR and GLM trends for this storm in Figure 6, made using the AWIPS Tracking Meteogram Tool.
Figure 6: 10 August 2019 graph of 10.35 um IR min brightness temperature over time (top) and GLM 5-min Flash Extent Density over time (bottom). Higher res
A line of severe storms progressed southeast across the upper midwest during the early evening hours on 5 August 2019. One-minute visible imagery from GOES-East provided an excellent view of storm top features and trends, including numerous overshooting tops and above anvil cirrus plumes, indicating active and exceptionally strong updrafts. Overlaying a semi-transparent 1-min GLM Flash Extent Density, we have even more information about individual updraft trends, augmenting the visible imagery whose details are still noticeable. Trends in the GLM lightning field tell us which updrafts are increasing in intensity, and which are decreasing, sometimes slightly prior to those trends becoming apparent in satellite and radar imagery. The GLM gridded lightning fields are on the same grid as the ABI data, so share the same degree of parallax. Also noted are periodic long flashes extending well away from the main updraft regions, indicating the potential for distant cloud-to-ground lightning strikes.
Figure 1: 5 August 2019 GOES-16 ABI 1-min VIS, semi-transparent GLM 1-min Flash Extent Density. For GLM, Blue to Yellow indicates increasing lightning activity. Full res
A large brush fire developed and spread quickly during the afternoon of 11 July 2019 on the Hawaiian island of Maui, and continued to spread through the evening. By 05Z, the fire was reported to have burned 3,000 acres. The wildfire was captured by GOES-West, which includes the Hawaiian islands in the southwest corner of its 5-min CONUS sector.
The fire first becomes apparent in the 3.9 um shortwave IR imagery over the west-central portion of the island at 2051 UTC, and quickly heats to a brightness temperature of 127C in its hottest pixel (Figure 1). Compare this to a temperature of 41C over the same pixel just prior to wildfire initiation. The fire quickly expands and spreads to the southeast during the afternoon. The fire slows its movement and cools slightly during the evening.
Figure 1: 11 July 2019 GOES-West 3.9 um shortwave IR imagery. Full res
Photos on social media showed a large smoke plume associated with this wildfire, which was also captured by GOES-West 0.64 um visible imagery (Figure 2). The smoke was observed pooling in the lower elevations within the center part of the island, while also being advected to the southwest in the mid levels. An intense updraft is apparent within the smoke field over the fire between 0221 UTC and 0331 UTC.
Figure 2: 11 July 2019 GOES-West 0.64 um visible imagery. Full res
The natural true color RGB imagery available in AWIPS provides an image similar to what one would see from outer space. In lieu of a green band on ABI, the green component in this RGB is approximated by combining the 0.47 um, 0.64 um, and 0.86 um bands. Of course, the 0.47 um band is used for the blue component of the RGB, and 0.64 um for the red component. In this case, the brown smoke stands out against the white clouds, green land, and blue ocean.
Figure 3: 11 July 2019 GOES-West Natural True Color RGB imagery. Full res
GOES-West GLM data recently became available to several NWS offices. This, of course, benefits western US NWS WFOs and offices with Pacific forecasting duties. Recall that GLM gridded products are reformatted to the 2 km ABI fixed grid, so share the same parallax as the ABI imagery (shifted away from nadir). With GOES-East at 75.2W, and GOES-West at 137W, the “cutoff” for “better” GLM data (less parallax, better detection efficiency) is at 106W (equal distance from both satellite subpoints). Offices west of 106W should use GOES-West GLM, and offices east of 106W should use GOES-East GLM (see Fig 1).
Figure 1: GOES-West and GOES-East CONUS sector coverage with respective VIS and GLM imagery from 6 Jul 2019. Relevant lines of longitude are highlighted. Full res
A comparison between GOES-East and -West GLM FED and ABI VIS data over eastern Montana (near 106W) using ENI point data as a constant (with assumed very little parallax) shows a similar degree of parallax between the two satellites (Fig 2). Of course, from the East point of view, the GLM and ABI data are displaced to the north and west, while that from the West point of view are displaced to the north and East.
Figure 2: 4 July 2019 GOES-East and GOES-West ABI VIS and GLM FED comparison, ENI CC and CG point lightning data, over eastern Montana. Full res
Another example from northeast California (120.5W), well west of 106W and closer to GOES-West subpoint, shows similar parallax between the two satellites meridionally (Fig 3). Zonally, however, there is significantly less parallax displacement in the GOES-West data (minor shift to the east) than in the GOES-East data (bigger shift to the west). Additionally, the nearer GOES-West is able to detect more flashes, and the GOES-East pixels are stretched further away from the satellite sub-point.
Figure 3: 6 July 2019 GOES-East and GOES-West ABI VIS and GLM FED comparison , ENI CC and CG point lightning data, over northeast California. Full res
Analyzing GOES-East GLM data over the northeast US (near 75W and 38N), we observe no parallax in the east-west direction, but significant displacement to the north (Fig 4).
Figure 4: 6 July 2019 GOES-East ABI VIS and GLM FED, ENI CC and CG point lightning data, over the northeastern US. Full res
Now looking further south (~15N) but still near 75W, northern displacement is much less, with ENI and GLM detentions very similar in location (Fig 5). The west-east parallax remains negligible.
Figure 5: 6 July 2019 GOES-East ABI VIS and GLM FED, ENI CC and CG point lightning data, over the western Caribbean Sea. Full res
One final example, this time from GOES-West, shows parallax with lightning associated with Hurricane Barbara remnants just south of Hawaii. Being south of 20N but between 150W and 160W (well west of the 135W subpoint), the parallax appears negligible to the north, but a shift to the west is apparent. (Fig 6). Both ENI and GLD lightning data are used in this case to ensure data quality in this remote area.
Figure 6: 9 July 2019 GOES-West ABI IR and GLM FED, ENI and GLD point lightning data, south of Hawaii. Full res
Currently, only GOES-West GLM data within the GOES-West CONUS ABI sector are sent to WFO AWIPS (covers the western 1/3 of CONUS). Similarly, only GOES-East GLM data within the GOES-East CONUS sector is sent to WFO AWIPS (covers the full CONUS). Figures 7 and 8 show GLM coverage over the CONUS from both satellites, respectively for the same time period on 3 July 2019.
Figure 7: 3 July 2019 GOES-East IR (gray), GOES-East GLM FED (color overlay). White vertical line is 106W. Full res Figure 8: 3 July 2019 GOES-West IR (lighter gray overlay), GOES-East IR (darker gray underlay), GOES-West GLM FED (color overlay). Note the GLM data is not available outside of the West CONUS sector. White vertical line is 106W. Full res
Therefore, while all CONUS offices are covered by GOES-East GLM data, only offices in the western 1/3 of the CONUS receive GOES-West GLM over their area of responsibility. If GOES-East GLM suffers a data outage, the eastern 2/3 of the US will be left without any GLM data. If GOES-West GLM suffers an outage, all of the CONUS will still have access to GLM data from GOES-East.
Fortunately, there are plans to extend GOES-West GLM coverage in AWIPS eastward to near Kentucky in the coming weeks.
