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 Caldor 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]

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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.

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.

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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.

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.

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GOES-16 “Clean” Infrared Window (10.35 µm) and “Red” Visible (0.64 µm) images [click to play animation | MP4]

1-–minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (above)  showed that Hurricane Ida gradually developed an eye, as the Category 1 storm intensified to Category 2 by 1800 UTC on 28 August 2021.

DMSP-17 SSMIS Microwave (85 GHz) image at 1235 UTC [click to enlarge]

Microwave (85 GHz) images from DMSP-17 (above) and DMSP-16 (below) — from the CIMSS Tropical Cyclones site — provided 2 views of the eye and eyewall structure at 1235 UTC and 2205 UTC, respectively.

DMSP-16 SSMIS Microwave (85 GHz) image at 2205 UTC [click to enlarge]

Ida was moving across very warm water (SST | OHC) — and was forecast to pass over an area of very high Ocean Heat Content associated with a warm eddy that was shed from the Gulf of Mexico’s Loop Current. Ida was also moving through an environment of low wind shear (below), which favored further intensification as it continued to approach the Louisiana coast.

GOES-16 Infrared images, with contours of deep-layer wind shear at 20 UTC [click to enlarge]

===== 29 August Update =====

GOES-16 “Clean” Infrared Window (10.35 µm) and “Red” Visible (0.64 µm) images [click to play animation | MP4]

Ida reached Category 4 intensity at 0600 UTC on 29 August; 1-minute GOES-16 Infrared and Visible images (above) depicted a well-defined eye during the hours leading up to the hurricane making landfall along the coast of Louisiana at 1655 UTC.

GMI Microwave imagery at 1510 UTC (below) portrayed a closed eye, with the heaviest precipitation located within the eastern semicircle of Ida.

GMI Microwave (85 GHz) image at 1510 UTC [click to enlarge]

A closer view of 1-minute GOES-16 Visible images (below) revealed the presence of low-level mesovortices within the eye of Ida — a feature often observed with high-intensity tropical cyclones. The mesovortices persisted as the hurricane moved inland, as Ida was slow to weaken. Just east of the eye, Galliano (KGAO) reported wind gusts as high as 85 knots (plot | text), before observations ceased after 21 UTC (presumably due to power outages).  A separate mesonet station at Galliano recorded a wind gust of 122 mph (NWS New Orleans tweet | plot); a ship reported a wind gust of 194 knots (tweet).

GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

The MIMIC Total Precipitable Water product (below) showed that Ida was transporting rich tropical moisture northward across the central Gulf of Mexico coast of the US, raising a threat for flooding rainfall. 

MIMIC Total Precipitable Water product, 28-29 August [click to enlarge]

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