Pyrocumulonimbus cloud in northwestern Canada

July 12th, 2022 |

GOES-17 “Red” Visible (0.64 µm, top left), Shortwave Infrared (3.9 µm, top right), “Clean” Infrared Window (10.35 µm, bottom left) and Fire Temperature RGB (bottom right) images [click to play animated GIF | MP4]

1-minute Mesoscale Sector GOES-17 (GOES-West) “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm), “Clean” Infrared Window (10.35 µm) and Fire Temperature RGB images (above) showed a wildfire just southwest of Yellowknife (CYZF) in Canada’s Northwest Territories, which produced a pyrocumulonimbus (pyroCb) cloud during the afternoon hours on 12 July 2022.

This large fire burned very hot, with 3.9 µm Shortwave Infrared brightness temperatures reaching 138.71ºC — which is the saturation temperature of ABI Band 7 detectors. The coldest pyroCb cloud-top 10.35 µm Infrared Window brightness temperatures were around -49ºC (lighter shades of blue).

Dry (and dusty) air over the Caribbean

July 12th, 2022 |
Hourly True Color imagery over the Caribbean, 1300 – 2000 UTC on 12 July 2022

CSPP True Color imagery (link) above suggests a region of apparent dust over the eastern Caribbean Sea. That is, there is a hazy look to the imagery that persists even as the region of sun glint moves past. Suspended dust in the tropical Atlantic is known to suppress convection. Other products besides true-color imagery can be used to show dry the air (qualitatively and quantitatively) over the Caribbean. For example, the toggle below (from this site) of the Saharan Air Layer analysis (via the Split Window Difference) and the Airmass RGB shows very dry air south of Hispaniola and Puerto Rico — orange in the Split Window Difference, and also an orange tint to the Airmass RGB.

Saharan Air Layer analysis and Airmass RGB, 1800 UTC on 12 July 2022 (Click to enlarge)

Air over the eastern Caribbean also shows large values of Aerosol Optical Depth (from the AerosolWatch site); the enhanced values are most likely a result of suspended dust from the Sahara. AOD is not computed in the region of sun glint — that’s the cause of the smooth curved line that arcs through extreme eastern Cuba.

Aerosol Optical Depth at 1950 UTC on 12 July 2022 (Click to enlarge)

Total Precipitable Water (TPW) from the MIMIC site (link) shows dry air over the eastern Caribbean (and over much of the tropical Atlantic Ocean north of 10oN). Total precipitable water derived from gridded NUCAPS fields (here), and relative humidity at 700 mb (here), also show dry air over the eastern Caribbean; they are also shown in a toggle with NUCAPS Quality Flags below.

MIMIC Total Precipitable Water, 2000 UTC on 11 July – 1900 UTC 12 July 2022 (click to enlarge)
Gridded NUCAPS Fields: Quality Flags, Relative Humidity at 700 mb, Total Precipitable Water, 1744 UTC on 12 July 2022 (click to enlarge)

An interesting feature in the animation at the top of this blog post is the development of convection over Hispaniola, over the topography, even in the presence of fairly dry air. NUCAPS analyses of 500-mb air temperature (here), show a cold pocket of air over Puerto Rico and Hispaniola, helping the development of convection there.

When assessing the environment of a region with sparse conventional data, such as the Atlantic (or Pacific) Ocean, or the Caribbean Sea, take advantage of information that satellite observations can give you.