A 2-panel comparison of GOES-16 (GOES-East) “Red” Visible (0.64 µm) and Shortwave Infrared (3.9 µm) images (above) showed the smoke plumes and thermal anomalies or “hot spots” (darker black to red pixels) associated with a flare-up of wildfires in western British Columbia on 17 August 2018.

A sequence of Shortwave Infrared (3.7 µm) images from Terra / Aqua MODIS and Suomi NPP / NOAA-20 VIIRS (below) revealed the diurnal changes in areal coverage and intensity of the thermal signature of the fires.

Toggles between Visible and Shortwave Infrared images from Terra MODIS (1912 UTC), NOAA-20 VIIRS (1950 UTC) ans Suomi NPP VIIRS (2129 UTC) are shown below (note: the NOAA-20 images are incorrectly labeled as Suomi NPP). It is interesting to note the impact that the smoke plume had on the air temperature at Quesnel (CYQZ) — because the smoke layer was optically dense enough (VIIRS True Color image) to significantly reduce incoming solar radiation, the temperature was as much as 14-18ºF (8-10ºC) cooler than Prince George (CYXS) to the north and Williams Lake (CYWL) to the south.

Farther to the east in Alberta, thick smoke caused very poor air quality in cities like Edmonton and Grande Prairie (photo 1 | photo 2). Daily composites of Suomi NPP VIIRS True Color RGB images from 11 August to 17 August (below) revealed the transport of smoke across British Columbia, Alberta and Saskatchewan.

A time series of surface reports from Edmonton, Alberta covering the period 14-17 August (below) showed that smoke restricted the surface visibility there to 1.5 miles on 15 August and 17 August.

===== 19 August Update =====

* GOES-17 images shown here are preliminary and non-operational *

A 2-panel comparison of GOES-17 Near-Infrared “Cloud Particle Size” (2.24 µm) and Shortwave Infrared (3.9 µm) images during the 7-day period of 13-19 August (above) showed the diurnal changes in thermal signatures of the ongoing British Columbia wildfires. The nighttime thermal signatures seen on the 2.24 µm images (brighter white pixels) result from the fact that this spectral band is located close to the peak emitted radiance of very hot features such as active volcanoes or large fires (below).

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The active eastern Pacific Hurricane season continues, as Lane has formed. Suomi NPP and NOAA-20 overflew the system early on 17 August 2018. The toggle above, from NOAA-20’s VIIRS Instrument, shows both the Day Night Band 0.70 µm visible Image and the 11.45 µm infrared channels. Lack of lunar illumination means that only Earthglow is making clouds visible; a distinct eye is not present. The step animation below between the NOAA-20 11.45 µm infrared and, 50 minutes later, Suomi NPP’s 11.45 µm Infrared, right at the limb of the scan, also show no distinct eye.

In fact, however, an eye was likely present at this time. As noted in the National Hurricane Center’s 0900 UTC Discussion (Link), “Recent microwave images show a well-defined low-level eye, but this feature is not yet apparent in geostationary satellite images.”  AMSR-2 (Advanced Microwave Scanning Radiometer 2) estimates of Convective Precipitation and Surface Rainfall in the toggle below (data from 1003 UTC) show a distinct eye.  AMSR-2 is a microwave instrument that flies on JAXA’s GCOM satellite;  microwave views of tropical cyclones are able to penetrate the cirrus shield that is commonly present, revealing important information about the low-level structure of a developing system.

Polar Orbit tracks are available here. For the latest information on Hurricane Lane, refer to the National Hurricane Center or to the CIMSS/SSEC Tropical Weather Website. Imagery from Polar Orbiters are available at this site that shows data from an antenna in Honolulu.

Thank you to William Straka, CIMSS, for the imagery.

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GOES-17 Data shown in this post are preliminary and non-operational!

A Strong thunderstorm developed over Nebraska on 15 August (read more below), depositing baseball-sized hail in Arthur County. This storm was sampled by a GOES-16 Mesoscale sector, and the 1-minute imagery allowed views of the rotating updraft (Link). The stereoscopic view above, from the GOES-16 and GOES-17 CONUS sectors, shows the development and evolution of the storm at 5-minute increments (Click here for animated gif). To view the storm in three dimensions, cross your eyes until you view 3 images, and focus on the image in the middle. This storm develops the above-anvil cirrus plume that has been shown to be associated with severe weather, as in this case.

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1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed the development of thunderstorms which produced large hail and damaging winds across parts of southwestern South Dakota and western/central Nebraska (SPC Storm Reports) on 15 August 2018. The dominant storm in Nebraska exhibited a well-defined Above Anvil Cirrus Plume (AACP), which is often an indicator of a storm producing severe weather such as tornadoes, large hail or damaging wind (reference). Also note the slow-moving parallel bands of boundary layer wave clouds or “billow clouds” in northwestern Nebraska — this is a signature of warmer air flowing along the top of a low-level temperature inversion (caused by a pool of cold outflow from earlier thunderstorms). A stereoscopic view of this convection (using GOES-16 and GOES-17 visible images) can be seen here.

The corresponding GOES-16 Mid-level Water Vapor (6.9 µm) images (below) better revealed the broad circulation of a middle-tropospheric low that was centered over South Dakota (500 hPa analysis).

GOES-16 “Clean” Infrared Window (10.3 µm) images (above) showed that the coldest cloud-top infrared brightness temperatures associated with thunderstorm overshooting tops were around -60ºC (darker red enhancement) — slightly warmer than that of the tropopause on rawinsonde data from North Platte, Nebraska (below).

Regarding the AACP feature, in this case the plume was colder than the adjacent underlying thunderstorm anvil, as seen in a toggle between GOES-16 Visible and Infrared images at 0005 UTC — when the storm produced a wind gust of 70 mph at the surface (below). The temperature profile and lapse rate of the upper tropospheric/lower stratospheric air directly above the thunderstorm overshooting top will have an influence on whether an AACP is warmer or colder than the underlying thunderstorm anvil surface.

Finally, when trying to correlate the location of storm-top satellite image features with reports of hail/wind/tornadoes at the surface, it is important to factor in the effect of parallax. The GOES-16 satellite (positioned over the Equator at 75.2º W longitude) viewing angle for the North Platte area is 54 degrees — which has the effect of shifting the apparent location of storm-top features to the northwest of their true location over the Earth’s surface. The pair of image toggles shown below demonstrate how the “parallax-corrected” (northwest-shifted) location of the hail or wind reports more closely aligns with the cold overshooting top (orange to red enhancement) associated with the strongest storm updraft at that time.

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