GOES-East Day-Snow-Fog RGB imagery played an important role in operational decision-making at NWS Norman, OK (OUN) when forecasting fog and low stratus progression on 03 Jan 2021. Making this situation particularly difficult was the presence of snow cover beneath the thin low cloud/fog deck, as cloud features could not be easily discerned in visible satellite imagery alone. From OUN, “Since the area of fog/stratus was so thin, you could see the snowpack through the deck, making it even more difficult to discern on visible satellite. The RGB allowed the liquid cloud to “pop out” so we could see the development and dissipation trends.”
The forecaster on shift mentioned that the GOES-East RGB imagery influenced operational decision-making related to TAFs as well as the temperature forecast. Specifically, “Use of the Day Snow-Fog RGB was critical in my forecast for the KOKC TAF, along with hourly temperatures west of OKC. While we did have a TEMPO group of IFR conditions at KOKC for a couple of hours due to uncertainty and potential impact, the dense fog and stratus dissipated on the western and northern edge of the OKC runway complex. The high res models forecasted this area to persist through the afternoon across the OKC metro to the KOUN terminal area, but with the aid of the RGB trends, we were confident that it would not make it past the western parts of OKC.”
First, GOES-East 0.64 um imagery reveals, to an extent, low clouds evolving atop snow cover (Fig 1). Given the similar appearance between the low cloud cover and snow cover and semi-transparency of the cloud cover, the precise location and edges of the cloud cover is difficult to discern throughout the evolution.
Now viewing the Day-Snow Fog RGB, the low clouds pop as shades of light blue against the background of red (snow cover) and green (bare ground), allowing for it’s precise location to be more easily tracked in space and time (Fig 2).
Similarly, Day Cloud Phase Distinction RGB imagery can be utilized to discern low clouds (light blue) over snow cover (green) and bare ground (darker blue) with more clarity than VIS alone (Fig 3).
Bill Line (NESDIS and CIRA), Kevin Brown (NWS/OUN), Randy Bowers (NWS/OUN)
An active synoptic pattern brought a wide variety of weather to portions of the central US during the day on 23 Dec 2020. From GOES-East water vapor imagery, one can diagnose a series of guilty shortwave troughs: one lifting northeast across the midwest, and the other on its backside digging southeast into the southern high plains (Fig 1).
The western shortwave trough sent a cold front south down the central/southern high plains during the morning, with gusty northerly winds developing in its wake. Given the dry antecedent conditions, widespread blowing dust developed, first across southeast Colorado, and spreading south into western Kansas and the TX/OK Panhandles.
GOES-East 1-min imagery was available over the region, capturing the blowing dust evolution through the day. During the morning, the lofted dust was clearly evident in 1-min animations of both the Geocolor and DEBRA-Dust products (Fig 2 and 3).
A 2-min VIS feature-following zoom animation provides a unique perspective of dust plume relative evolution, including periodic cumulus cloud development atop the blowing dust (Fig 4).
Combining the Geocolor and DEBRA-Dust products for the duration of the daytime allows for the lofted dust to be highlighted within a more natural looking animation (Fig 5).
In the absence of DEBRA-Dust in AWIPS, a similar product can be made by combining geocolor (or single-band VIS) with the SWD as an overlay and applying a varying transparency color table around the values for lofted dust (Fig 5b).
Finally, the Dust-Fire RGB captured the dust (relatively bright green) well, along with a few wildfire hot spots (red) in its path (Fig 6). Clouds (and very cold land) appear as various shades of blue.
NWS Amarillo issued a great tweet highlighting the blowing dust in GOES-East Geocolor imagery:
The blowing dust was captured in slightly higher detail in SNPP and NOAA-20 VIIRS geocolor imagery:
To the northeast, on the backside of the eastern shortwave, gusty north winds forced areas of blowing snow. The blowing snow can be diagnosed in an RGB similar to the Day-Snow Fog RGB, but replacing the 0.86 um band with the higher resolution 0.64 um band for the red component, and making other minor adjustments. This RGB is introduced for regions of blowing snow in South Dakota (Fig 7) and ND/MN/Canada (Fig 8). Kudos to Carl Jones (NWS Grand Forks, ND) for pointing out these areas of blowing snow.
Widespread strong to severe thunderstorms developed across Argentina during the day on 18 December 2020. To capture the phenomena, a GOES-East meso-sector (-1) was positioned over the region, per a international request via the NESDIS Satellite Analysis Branch, which read, “Possible explosive cyclogenesis over central Argentina may bring heavy rains with possible severe thunderstorm and high surface winds”. GOES-East Full Disk water vapor imagery captured the evolution of a compact shortwave trough moving onshore in western South America and helping to spark widespread thunderstorm development (Fig 1).
A long duration (5-min-updating) IR-Window animation of the full mesoscale sector captures the evolution of the thunderstorms from the early day into the early nighttime (Fig 2). Not only are widespread thunderstorms detected, but an outflow boundary/cold front is analyzed racing north in the wake of the thunderstorms, adjacent to the high terrain, over the northwest portion of the sector (diagnosed as a sharp transition to relatively light gray, or cool, brightness temperatures).
First focusing on convective initiation for some of the most impressive, in appearance, thunderstorms, the Day Cloud Phase Distinction RGB, (at 1-min resolution) captured the trend from growing cu field (cyan clouds), to glaciation (cyan => green), to failed updraft attempts and orphan anvils (red/yellow) (Fig 2).
Playing the full animation, successful convective initiation is observed shortly thereafter (Fig 3). Note, the RGB shown was modified from the default recipe, which quickly reaches the max threshold for the reflectance components during the summer. In this example, the green (0.64 um) component max was raised to 105%, while the blue (1.61 um) component max was raised to 65%. After making the adjustment, cloud top texture becomes apparent.
Following initiation, thunderstorms quickly matured and developed impressive storm top signatures, including rapidly expanding anvil, abundant texture, overshooting tops, and long-lived above anvil cirrus plumes, per 1-min VIS (Fig 4). In this example, a color table focusing on higher reflectance was utilized in order to best capture the storm top detail.
Over the same region and time period, a 1-min VIS-IR sandwich overlay provides more insight about the storm top features by adding brightness temperature information (Fig 5).
Now turning attention to activity near the outflow/cold front progression and lofted dust was apparent along and behind the boundary per 0.64 um VIS (Fig 6) and daytime Geocolor imagery (Fig 7). The DEBRA Dust product highlighted regions of most likely dust (Fig 8). The blowing dust along and behind the boundary apparent in the imagery acts as a fluid tracer of the dense air as it flows within the valley and interacts with higher terrain. Video of the blowing dust was captured from the region (see here and here).
A Dust-Fire RGB not only shows the blowing dust (bright green), but also indicates wildfire hot spots (isolated pixels of bright red) in the scene (Fig 9). A large hot spot is detected in the southeast portion of the scene early in the period, while two smaller hot spots are found in the left center portion of the scene ahead of the cold front and blowing dust. Deep convection appears as blue, drier boundary layer as medium green, and a relatively moist boundary layer as medium-dark red.
Finally, a longer VIS-IR transition animation captures the full evolution of the boundary and related blowing dust into the evening (Fig 10).
A mid-December winter storm brought significant snowfall to the northeast US, including totals over 40″ (Fig 1)!
GOES-East Water Vapor imagery from Sunday evening through Thursday morning captured the evolution of the shortwave trough, a key ingredient to the major winter storm, across the nation (Fig 2). An overlay of RAP analysis fields helps one to correlate the synoptic scale features apparent in the water vapor imagery with those in the upper level analysis. For example, the sharp temperature gradient on the southern periphery of the wave (cold on south side, warm on north side) represents the location of upper level jet winds. Additionally, the shortwave is easily identified given the cyclonic circulation apparent in animations, but also via the couplet of warm/dry descending air and cool/moist ascending air
A IR-VIS/IR Sandwich transition procedure from GOES-East shows the evolution of the system along the east cost during the evening of the 16th into the morning of the 17th, with the surface low circulation becoming exposed during the daytime (Fig 3). The overlay of RAP analysis MSLP adds quantitative information about surface pressure trends and .
GLM imagery captured a few instances of lightning within areas of ongoing snow (thundersnow) during the overnight hours, including in W PA and SE PA early in the evening/animation, and then in NH by early morning and late in the loop. Abundant lightning was detected with thunderstorms off the coast along the front (Fig 4).
During the day of the 17th, numerous interesting features could be diagnosed in the GOES-East Day Cloud Phase Distinction RGB imagery (Fig 5). Surface features in clear sky areas include melting snow in Maryland, snow cover extent, and snow cover over forested areas vs that over non-forested areas. As for cloud features, low clouds and fog (liquid clouds), including over snow, can be differentiated from high/glaciated clouds and potential areas of snowfall. The precise location of the surface low can be tracked, along with nearby and abundant gravity waves which can imply turbulence. Further, individual/narrow snow bands are diagnosed across E NY, CT, RI, and MA.
A comparison for one time period between the DCPD RGB and MRMS composite reflectivity demonstrates the ability of the RGB to capture individual snow bands, which can be especially valuable as a compliment and in the absence of radar (Fig 6).
GOES-East 1-min mesoscale sectors were centered over the storm system during it’s evolution. One-minute visible imagery provided a detailed (spatially and temporally) view of the surface low circulation and adjacent cloud top gravity waves as it moved offshore (Fig 7).
A series of shortwave troughs brought strong winds and a pair of widespread blowing dust events to E NM and W TX on Dec 13 and Dec 15, 2020. The first event saw the lofted dust begin in E NM, and expanding east into W TX during the day in response to a compact and quick moving shortwave trough digging across the region per 6.2 um water vapor imagery (Fig 1). Imagery for the Dec 13 case comes from the CIRA Slider, while Dec 15 imagery comes from AWIPS and CIRA Slider.
The blowing dust was captured well in GOES Geocolor imagery, and as has been discussed in previous blog posts, diagnosis in the western US is better in GOES-West imagery during the early day, and GOES-East imagery during the late day (Fig 2-3).
A product not discussed much on this blog, but is available on the CIRA Slider, and upon request, in NWS offices AWIPS, is the DEBRA Dust product from CIRA (Fig 4). The product is effective in drawing attention to regions of potential blowing dust, prompting further interrogation.
The next blowing dust event occurred, primarily across W TX, after another shortwave and associated jet streak tracked across the area, captured again in WV imagery and also analyzed in RAP 500 mb height field and 250 mb wind field (Fig 5). Dry descending air is observed and an intensifying 120+ knot jet max analyzed across W TX during the time of strong surface winds and blowing dust.
The following GOES-East imagery has been discussed in numerous dust posts on this blog, and includes Geocolor (Fig 6), DEBRA Dust (Fig 7), SWD-IR Combo (Fig 8), and Dust-Fire RGB (Fig 9). Each of these displays has proven effective in reliable blowing dust detection. While Geocolor provides high resolution daytime detection option and DEBRA-Dust a high resolution day/night option (but with some false alarm), SWD-IR combo and Dust-Fire RGB (which incorporates the SWD), provide day/night dust detection (at slightly lower spatial resolution), along with cloud classification. The Dust-Fire RGB has the added benefit of incorporating wildfire hot spot detection, which often develop during such high wind events. This particular SWD-IR procedure includes the SWD as the gray scale bottom layer, Clear Sky Mask as the middle layer, and cold IR BTs as the color top layer, in order to isolate the blowing dust feature (darkest gray) from clouds, while also including cloud temperature information. All methods require the forecaster to do some degree of analysis and interpretation in order to make a determination on whether the feature is dust.
Exemplifying the multiple dust detection methods available to and used by operational forecasters, NWS offices across the region shared various imagery on social media during the events:
Low relative humidities and strong wind gusts combined with very dry fuels resulted in the rapid development and growth of wildfires in southern California overnight on 12/2 – 12/3 2020. In fact, widespread wind gusts greater than 60 mph were reported, with a peak gust of 95 mph measured at Big Black Mountain. GOES-West 3.9 um imagery captured the wildfire development and evolution through the evening (Fig 1). The display also includes surface observations, which captured very nearby wind gusts to 46 knots. RAP RH analysis indicated widespread humidities below 15%, with values dipping as low as 5% near the wildfires.
VIIRS Day Night Band Near Constant Contrast Imagery, available in AWIPS, also captured the glow associated with the southern California Wildfires as they developed (Fig 2). Raising the “Max” value in the colormap range for NCC considerably (in this case to 30), allows the bright glow of the wildfires to stand out against the less bright city lights. During this evening, there were two passes of SNPP and one pass of NOAA-20 over this location, allowing for three images within a ~ 1 hour and 40 minute timespan. The VIIRS imagery is compared with a GOES-West SWIR image, exemplifying the significant amount of detail added from 750 m VIIRS DNB over 2 km (at nadir) ABI SWIR. The glow from the wildfires appears as very light gray to white, while city lights are a medium gray, in this example.
A shortwave trough ejecting out of the Great Basin east into the central US plains sent a cold front south through the southern high plains during the afternoon/evening of 11 Nov 2020. Gusty winds developing ahead of and behind the front resulted in widespread blowing dust across the region. Widespread wind gusts in excess of 45 mph were reported, along with visibility reductions generally to around four miles, and in some cases, to near zero. The video below depicts the blowing dust during the afternoon in far east-central Colorado.
GOES-West water vapor imagery from the previous evening through the day on the 14th reveals the influencing trough as it tracked through the region (Fig 1).
Blowing dust already developed during the late morning and early afternoon across northeast Colorado. Lofted dust was captured well in an animation of 500 m visible imagery with a cold 10.3 um IR BT overlay in order to mask out clouds (Fig 2). The 500 m nadir resolution is adequate to pinpoint the source points of the many individual dust plumes, similar to smoke emanating from a wildfire hot spot.
The lofted dust was also captured during the day in the Day Land Cloud RGB which incorporates the 500 m VIS channel in addition to 0.86 um Veggie band and 1.6 um snow/ice band, allowing it to capture surface/near-surface features well and differentiate ice and water clouds (Fig 3).
GOES-East Geocolor imagery provided perhaps the best depiction of the blowing dust during the daytime (Fig 3b). Further, 1-min imagery was available over the region during the event, allowing for a more detailed characterization to the dust evolution versus the 5-min conus imagery.
Similar animations capture afternoon blowing dust developing across southern Colorado, including dust collecting along the south-bound cold front as it tracked into the PHs (Fig 4-5).
Dust was similarly lofted across E NM and W TX in dry conditions with strong westerly winds (Fig 6-7).
A GOES-East Geocolor animation captures the full daytime evolution of blowing dust across the southern High Plains.
While GOES-East visible imagery provided better detection of blowing dust during the afternoon/evening due to increasing forward scattering, GOES-West contributed a better depiction during the morning. Two areas of very active morning blowing dust are shown from the GOES-West perspective: southern Colorado just south of la Junta, and far southwest TX (Fig 8-9).
The blowing dust continued after dark (after 2311 UTC) across much of the same region, particularly along and behind the the cold front pushing south out of KS into the PHs. IR only animations also captured the blowing dust evolution. The advantage of the IR-only imagery products is that dust can continue to be diagnosed after dark, in addition to during the day.
The evolution of blowing dust during the day into the night is shown first in the SWD, using a simple linear grayscale color table, with IR Window cold BTs overlaid (Fig 10). This simple display reveals areas of likely blowing dust into the night (dark gray to black), along with cloud top temperature trend information.
The default AWIPS Dust RGB, which incorporates the SWD along with the Split Cloud Top Phase and IR Window channel, captures the dust (pink) evolution into the night along with cloud top phase information (Fig 11).
Tweaks to that RGB, similar to those outlined in this blog post, help to make the lofted dust more easily diagnosable (dark cyan; Fig 12).
Finally, another RGB discussed here allows for dust (bright green) tracking in addition to wildfire hotspot detection (Fig 13). In this case, there did not appear to be any active fires in the region during the time period.
750 m VIIRS True Color imagery captured the early evolution of the blowing dust from 1930 UTC (SNPP) to 2020 UTC (NOAA-20) across E CO (Fig 14) and W TX (Fig 15).
Finally, an even higher resolution view (10 m) of the blowing dust is captured by the Sentinal-2 mission. These data are only available over a given point every few days, and are not as quickly available to forecasters as the NOAA satellite data, but provide a very high resolution, confirming view after the fact in some cases. The images shared in Figures 16 and 17 show the very early stages of lofted dust (1753 UTC) across southern Wyoming (east of Cheyenne) and southeast Colorado (south of La Junta). The source points of the lofted dust are clearly evident in this imagery.
The following tweets from NWS Amarillo presents photo of the impending blowing dust in the Texas Panhandle, along with a satellite view (GOES Dust RGB) representing the extent of blowing dust and its forecast evolution.
A previous blog post documented the explosive growth of the East Troublesome Fire during the day of Oct 21 through the late evening. The fire had spread east to near the Continental Divide, west of Rocky Mountain National Park (RMNP), slowing by late that night.
During the morning of 22 Oct, NWS BOU forecasters monitoring the wildfire hot spot in GOES-East imagery noted an eastward movement of the far eastern portion of the fire, northeast of Grand Lake and west of Estes Park, possibly across the Continental Divide (Fig 1).
An image captured by BOU forecasters shows the Fire Radiative Power product in relation to the most recent burn scar shapefile and other local geographic features and towns (Fig 2). Accounting for the surface parallax (from GOES-East, surface features are displaced to the north and west at this location/elevation by several km), fire associated with the easternmost hot spot would actually be situated to the southeast, just east of the Divide and west of Bear Lake in RMNP.
Accounting for surface parallax, BOU believed that the hot spot may have advanced east across the Continental Divide during this period. Based on this development as diagnosed in GOES-East imagery, BOU forecasters alerted (via phone call) RMNP dispatch (and Laminar County) to the possibility that the fire had pushed east across the Divide into western RMNP. They were unaware of fire growth into the park at the time, and would go on to call out fire partners to investigate. Although it took a while to get confirmation, it would be confirmed that the fire had indeed crossed over the Continental Divide.
A cold front would soon push west into the I-25 corridor and eventually to Estes Park, dropping temperatures and raising humidity’s with a light east wind. The moist stable layer may have made it west up to the fire, putting a damper on fire behavior. GOES Natural Color Fire imagery from the early afternoon showed low stratus draped across the eastern Colorado plains, while the wildfire continued to burn hot west of the Divide in the presence of still dry and windy conditions (Fig 3). Also diagnosed in the imagery was a thick smoke plume with pyrocu spreading well east over the stratus deck. The smoke plume masked the hot spot in RMNP for the rest of the afternoon/evening.
During the evening of the 22nd, the glow associated with the fire in western RMNP could be diagnosed in (terrain corrected) VIIRS Day Night Band imagery (Fig 4).
This is a great example of a forecast office utilizing GOES imagery to provide potentially life saving IDSS to core partners.
Bill Line, NESDIS and CIRA (with input from NWS BOU)
The East Troublesome Fire, in Grand County, Colorado near Grand Lake and west of Rocky Mountain National Park, experienced substantial growth during the afternoon/evening of 21 October 2020. Dry environmental and fuel conditions, along with gusty winds, caused the fire to grow from 19,086 acres to 125,602 acres during the 1-day timeframe per Inciweb (see maps below).
GOES-East imagery captured the rapid growth of the associated hot spot signature. Throughout the event, NWS Boulder shared GOES-East imagery of the fire on social media to help inform the public of it’s evolution as it quickly spread east. A couple examples are shown below.
VIIRS imagery from the early afternoon captured the wildfire as it began it’s rapid growth (Fig 1). The Fire Radiative Power product provided a high resolution view of the heat associated the fire, highlighting a particularly active zone over the northeast portion of the fire (which would go on to continue to expand east rapidly). The underlay of VIIRS True Color imagery shows the associated smoke plume with pyrocu developing near the hot spot. This imagery is available online from the JSTAR mapper.
The daytime evolution of the wildfire is shown through the GOES-East Natural Color Fire RGB in Figure 2. The rapid growth of the wildfire hot spot is observed to begin after 2000 UTC, with the large smoke plume extending well east. Ashfall was abundant across downstream locations such as Fort Collins and Loveland. Pyrocumulus clouds were also present with the smoke plume. The large burn scar associated with the Cameron Peak Fire, north of Estes Park, is apparent, along with several other smaller burn scars throughout the scene.
A VIS-IR-SWIR combo animation extending after sunset highlights the development of the smoke plume, including eventual cooling of pyrocu to as cold as -60C after dark (Fig 3).
Long animations of GOES-East SWIR and Fire Temperature RGB show the full evolution of the wildfire hot spot growth on the 21st from Noon through around midnight (Fig 4-5). Steady growth/heating is observed through teh afternoon, before the rapid acceleration east after dark to near the Continental Divide. west of Rocky Mountain National Park.
Similar time periods but zoomed out images provide another perspective of the large growth and massive size of the fire (Fig 6-7).
The fire becomes so hot in areas that the signal in SWIR channel becomes saturated. This is a situation where the Fire Temperature RGB becomes a little more useful for those wishing to monitor fire heating trends the most active/hottest regions of the wildfire. Figure 8 from 0131 UTC compares SWIR with Fire Temperature RGB, exemplifying the power of the RGB to reveal more detailed temperature information after the SWIR channel becomes saturated. While the SWIR saturates, the Fire Temp RGB shows progressively hotter regions from red to yellow to white through it’s inclusion of the 2.2 um and 1.6 um bands, in addition to the SWIR.
GOES-West similarly displayed the evolution of the wildfire through the afternoon/evening (Fig 9).
A couple hours after midnight, SNPP and NOAA-20 VIIRS DNB NCC imagery revealed the glow of the now very large hot spot associated with the East Troublesome Fire, as well as the most active areas (Fig 10). The massive size can be compared with the City of Denver to the east.
The VIIRS Fire Radiative Power Product, shown earlier in this post, is also available at night, and shown in Figure 11. Again, the product provides a higher resolution view of the current location of the wildfire, along with the hottest areas.
Wildfires remained active across northern Colorado by 20 Oct 2020. The Cameron Peak Fire, west of Fort Collins, had grown to over 200,000 acres, the largest wildfire in Colorado recorded history.
Viewing GOES-East SWIR imagery over northern Colorado during the morning of Oct 20, a hot spot is barely apparent from the Cameron Peak Fire, just west of Fort Collins (Fig 1-2 top). From the SWIR and other channels, one easily finds that this is due to cloud cover. However, the western US has the benefit of overlapping 5-min (CONUS/PACUS) imagery from GOES-East and GOES-West satellites. Upon viewing GOES-West SWIR imagery, a hot spot associated with the Cameron Peak Fire is readily apparent through the morning (Fig 1-2 bottom).
Viewing Natural Color Fire RGB imagery, the quasi-stationary cloud masking the hot spot in GOES-East imagery is obviously situated to the east of the wildfire in GOES-West imagery, allowing for a clear view of the hot spot (Fig 3-4). This is a good visualization of parallax, and how clouds will appear situated at different locations relative to the surface in reality, and between GOES-East and GOES-West.
It is important for forecasters in the west to remember that they have two options for 5-min geostationary imagery, and that there are situations where one may provide additional insight over the other.