Caldor Fire approaches South Lake Tahoe

August 31st, 2021 |
Suomi NPP and NOAA-20 (as indicated) VIIRS Day Night Band visible (0.7 µm) imagery, 11-31 August 2021 (Click to enlarge). Sacramento CA is at the western edge of the imagery, and Reno NV is along the northern boundary.

Day Night Band imagery collected from the VIIRS-Today website, above, shows night-time snapshots of the Caldor Fire (discussed previously here, here and here on this blog) as it formed and moved towards Lake Tahoe in August 2021. On 31 August, the last day of the animation, the fire was close enough to the city of South Lake Tahoe that evacuation orders for that town have been issued.

The longer animation, below, shows the evolution of the Caldor Fire and the Dixie Fire complex as well (and is an update to this blog post).

Suomi NPP and NOAA-20 (as indicated) Day Night Band Imagery, 9 July – 31 August 2021 (Click to enlarge)

VIIRS imagery can also be used to outline burn scars from the fire. The ‘False Color’ RGB image below, from 30 August 2021 (from this url at VIIRS Today), depicts just how large the burn scar (the brownish region in the imagery) from the Dixie Fire is.

NOAA-20 False Color imagery from 30 August 2021 (Click to enlarge)

Smoke plumes continue from Northern California wildfires

August 30th, 2021 |

GOES-17 True Color RGB images [click image to play animation | MP4]

GOES-17 (GOES-West) True Color RGB images created using Geo2Grid (above) showed the diurnal variation of smoke from the Dixie Fire and the Calfor Fire in Northern California on 30 August 2021. Early in the day, smoke from the previous day of fire activity that had settled into valleys was apparent — however, as daytime heating continued this valley smoke was ventilated and mixed to higher altitudes, with new smoke plumes eventually developing as the fire activity ramped up once again. Occasional brighter-white pyrocumulus clouds were produced over the hottest portion of the larger fires.

===== 31 August Update =====

GOES-17 True Color RGB images [click image to play animation | MP4]

GOES-17 (GOES-West) True Color RGB images created using Geo2Grid (above) showed the diurnal variation of smoke from the Dixie Fire, Caldor Fire and Tamarack Fire in Northern California on 31 August 2021. Early in the day, smoke from the previous day of fire activity that had settled into valleys was evident — but as daytime heating continued, this valley smoke was ventilated and mixed to higher altitudes, with new smoke plumes eventually developing as the fire activity ramped up once again. Occasional brighter-white pyrocumulus clouds were produced by the larger, hotter fires.

In a toggle between Suomi NPP VIIRS True Color RGB and False Color RGB images (below), recent fire burn scars appear as darker shades of reddish-brown while currently active and hot fires appear as brighter shades of pink in the False Color image. 

Suomi NPP VIIRS True Color RGB and False Color RGB images [click to enlarge]

Suomi NPP VIIRS False Color RGB images 5 days apart — 26 August and 31 August — (below) revealed changes in fire burn scar size and active fire locations across that region.

Suomi NPP VIIRS False Color RGB images on 26 August and 31 August [click to enlarge]

A closer view of Suomi NPP VIIRS True Color RGB and False Color RGB mages centered on the Caldor Fire (below) showed that a large active fire was located just a few miles south of South Lake Tahoe, California. 

Suomi NPP VIIRS True Color RGB and False Color .RGB images [click to enlarge]

 

Tropical Storm Kate loses convection

August 30th, 2021 |
GOES-16 Visible (0.64 µm) Imagery, 0930 – 1900 UTC on 30 August 2021 (Click to play animation)

The animation above, of GOES-16 Visible (0.64 µm) imagery, shows Tropical Storm Kate at sunrise with convection near the storm center and to its east. (An overnight image from Suomi NPP’s Day Night Band, below, taken from NASA Worldview, also shows convection near the storm center.) As the day progresses, however, the obvious surface circulation moves northward and the convection near the surface collapses.

Suomi NPP Day Night Band Visible (0.7 µm) imagery over Tropical Storm Kate, 30 August 2021 (Click to enlarge)

The shear analysis from the CIMSS Tropical Website, below, shows why the convection is displaced to the east of this storm. Strong westerly shear is present.

200-850 shear analysis over Tropical Storm Kate, 1900 UTC on 30 August 2021 (Click to enlarge)

Day Night Band imagery after Ida

August 30th, 2021 |
Suomi NPP (0740 UTC) and NOAA-20 (0830 UTC) VIIRS Day Night Band visible (0.7 µm) imagery on 30 August 2021 (Click to enlarge)

Day Night Band imagery from the VIIRS (Visible Infrared Imaging Radio-Spectrometer) instrument on Suomi NPP and NOAA-20 allows satellite-borne estimates of power outages after strong storms. The imagery from Suomi NPP (0740 UTC) and NOAA-20 (0830 UTC) (orbital paths can be viewed here) shows a sharp reduction in the amount of light normally present over southeast Louisiana. This is especially true around the city of Houma, in eastern Terrebonne Parish. Lafourche Parish also looks devoid of man-made light sources.

Of course, interpretation of this signal will always be complicated by thick clouds and rainfall, two things that ably attenuate man-made light as it moves up towards the satellite. GOES-16 10.3 Clean Window imagery for the same times as above, below, shows that much of the high cloudiness with the storm had moved north of metropolitan New Orleans by the times of the images above. New Orleans International Airport (KMSY) reported no rain after 0600 UTC (although ceilings remained low: between 500 and 800 feet); clouds were likely thick.

GOES-16 ABI Band 13 Clean Window infrared (10.3 µm) at 0741 and 0831 UTC on 30 August 2021 (Click to enlarge)

What does southeast Louisiana typically look like? The image below, from 28 August (clipped from the VIIRS Today site), shows the Gulf Coast region from Houston TX (bright feature near the left edge) to Mobile and Pensacola on the right.

Suomi NPP Day Night Band, 28 August 2021 (Click to enlarge)