Ferguson Fire in California forms a pyrocumulonimbus cloud

July 15th, 2018 |
GOES-16

GOES-16 “Red” Visible (0.64 µm, left), Shortwave Infrared (3.9 µm, center) and “Clean” Infrared Window (10.3 µm, right) images [click to play MP4 animation]

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

The Ferguson Fire in central California produced a pyrocumulonimbus (pyroCb) cloud during the afternoon hours on 15 July 2018. GOES-16 (GOES-East) “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.3 µm) images (above) showed that the high-altitude portion of the pyroCb cloud then drifted northeastward toward the California/Nevada border, where cloud-top infrared brightness temperatures cooled to near -55ºC (orange enhancement) as it crossed the border around 0005 UTC on 16 July.

A comparison of Visible images from GOES-15 (0.63 µm), GOES-17 (0.64 µm) and GOES-16 (0.64 µm) is shown below — with the imagery displayed in the native projection of each satellite. Images from GOES-16/17 are at 5-minute intervals, while images from GOES-15 are every 5-15 minutes depending on the operational scan schedule of that GOES-West satellite. GOES-17 was at its post-launch checkout position of 89.5ºW longitude, so it offered a more direct view of the pyroCb cloud.

Visible images from GOES-15 (0.63 µm, left), GOES-17 (0.64 µm, center) and GOES-16 (0.64 µm, right) [click to play animation]

Visible images from GOES-15 (0.63 µm, left), GOES-17 (0.64 µm, center) and GOES-16 (0.64 µm, right) [click to play animation]

A toggle between NOAA-19 Visible (0.63 µm), Shortwave Infrared (3.7 µm) and Infrared Window (10.8 µm) images (below) showed the pyroCb cloud southwest of the California/Nevada border at 2327 UTC. In spite of a minimum cloud-top infrared brightness temperature of -59ºC (red enhancement), note the darker (warmer) appearance of the cloud on the 3.7 µm image — this is due to reflection of solar radiation off the smaller ice particles of the pyroCb anvil. The -59ºC temperature roughly corresponded to an altitude of 13 km or 42.6 kft on the 00 UTC Reno, Nevada rawinsonde report (plot | data)

NOAA-19 Visible (0.63 µm), Shortwave Infrared (3.7 µm) and Infrared Window (10.8 µm) images [click to enlarge]

NOAA-19 Visible (0.63 µm), Shortwave Infrared (3.7 µm) and Infrared Window (10.8 µm) images [click to enlarge]

A time lapse of the pyroCb was created by Sierra Fire Watch (below).

Time lapse [click to play YouTube video]

Time lapse [click to play YouTube video]

Mesoscale Convective Vortex generated by monsoon thunderstorms in Arizona

July 9th, 2018 |

As mentioned by NWS San Diego, monsoon thunderstorms that developed over Arizona spawned a small Mesoscale Convective Vortex (MCV). The animation below shows nighttime GOES-16 (GOES-East) “Clean” Infrared Window (10.3 µm) images, followed by daytime GOES-16 “Red” Visible (0.64 µm) images — the center of the MCV circulation briefly exhibited an “eye-like” appearance just after 16 UTC (south of the California/Mexico border).

GOES-16

GOES-16 “Clean” Infrared Window (10.3 µm) and “Red” Visible (0.64 µm) images, with hourly plots of surface reports [click to play MP4 animation]

A 1-km resolution NOAA-19 Infrared Window (10.8 µm) image at 1132 UTC (below) showed a more detailed view of the small cluster of thunderstorms responsible for the MCV — the convection produced 0.68″ of rainfall near Yuma KNYZ in far southwestern Arizona, and generated an outflow boundary which produced wind gusts to 46 mph at Thermal, California KTRM (NWS statements).

NOAA-19 AVHRR Infrared Window (10.8 µm) image [click to enlarge]

NOAA-19 AVHRR Infrared Window (10.8 µm) image [click to enlarge]

A toggle between 1-km resolution NOAA-15 and NOAA-18 Visible (0.63 µm) images (below) revealed the emergence of the eye-like MCV center in far northern Baja California (just southeast of Campo, California KCZZ) at 1547 UTC.

NOAA-15 and NOAA-18 Visible (0.63 µm) images [click to enlarge]

NOAA-15 and NOAA-18 Visible (0.63 µm) images [click to enlarge]

Mesoscale Convective System in the Plains

June 11th, 2018 |

GOES-16

GOES-16 “Clean” Infrared Window (10.3 µm) images, with plots of SPC storm reports [click to play MP4 animation]

A Mesoscale Convective System (MCS) developed over eastern Nebraska early in the evening on 11 June 2018, then propagated southward across the Plains during the subsequent overnight hours. GOES-16 (GOES-East) “Clean” Infrared Window (10.3 µm) images with plots of SPC storm reports are shown above; a Mesoscale Sector was positioned over the region, providing images at 1-minute intervals.

A closer look over Kansas using Infrared imagery from polar-orbiting satellites (below) revealed some very cold cloud-top infrared brightness temperatures, which included -87ºC on MODIS, -90ºC on VIIRS and -92ºC on AVHRR.

POES AVHRR, Terra/Aqua MODIS and Suomi NPP VIIRS Infrared images, with plots of SPC storm reports [click to enlarge]

Metop-B AVHRR, Terra/Aqua MODIS and Suomi NPP VIIRS Infrared images, with plots of SPC storm reports [click to enlarge]

The coldest air temperature on 00 UTC rawinsonde data from Dodge City and Topeka, Kansas (below) was -69.5ºC (at altitudes of 14.6 km/49,900 feet at Dodge City, and 17.6 km/57,700 feet at Topeka) — so in theory air parcels and cloud material within a vigorous overshooting top could have ascended a few km (or thousands of feet) beyond those altitudes to exhibit an infrared brightness temperature of -92ºC.

Plots of rawinsonde data from Dodge City and Topeka, Kansas [click to enlarge]

Plots of rawinsonde data from Dodge City and Topeka, Kansas [click to enlarge]

A toggle between re-mapped versions of the GOES-16 ABI and Metop-B AVHRR Infrared imagery over Kansas at the time of the very cold cloud-top infrared brightness temperature (below) revealed 2 important points: (1) with improved spatial resolution (1 km for AVHRR, vs 2 km *at satellite sub-point* for ABI) the instrument detectors sensed much colder temperatures (-92.6ºC with AVHRR vs -81.2ºC with ABI), and (2) due to parallax. the GOES-16 image features are displaced to the northwest. In addition to the isolated cold overshooting top in south-central Kansas, note the pronounced “Enhanced-V” storm top signature in far northeastern Kansas.

Comparison of GOES-16 ABI and Metop-B AVHRR Infrared images [click to enlarge]

Comparison of GOES-16 ABI and Metop-B AVHRR Infrared images [click to enlarge]

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PyroCumulonimbus cloud in Colorado

June 9th, 2018 |

GOES-16

GOES-16 “Red” Visible (0.64 µm, left), Shortwave Infrared (3.9 µm, center) and “Clean” Infrared Window (10.3 µm, right) images, with hourly plots of surface reports [click to play MP4 animation]

GOES-16 (GOES-East) “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.3 µm) images (above) showed the formation of a small pyroCumulonimbus (pyroCb) cloud spawned by the 416 Fire in southwestern Colorado on 09 June 2018. A Mesoscale Domain Sector was positioned over the region, providing images at 1-minute intervals.

On Shortwave Infrared imagery, the thermal anomaly or “hot spot” appeared as a large cluster of red pixels — and the top of the pyroCb cloud took on a darker gray appearance than nearby high-altitude ice crystal clouds (due to enhanced solar reflectance off the smaller ice crystals of the pyroCb anvil). On 10.3 µm imagery, cloud-top infrared brightness temperatures cooled to around -50ºC (bright yellow enhancement) as the pyroCb drifted northeastward.

NOAA-19 AVHRR Visible (0.63 µm), Shortwave Infrared (3.7 µm) and Infrared Window (10.8 µm) images, with plots of 22 UTC surface reports [click to enlarge]

NOAA-19 AVHRR Visible (0.63 µm), Shortwave Infrared (3.7 µm) and Infrared Window (10.8 µm) images, with plots of 22 UTC surface reports [click to enlarge]

On 1-km resolution NOAA-19 AVHRR Infrared Window (10.8 µm) imagery at 22:07 UTC (above), the minimum cloud-top brightness temperature was -53ºC — this temperature roughly corresponded to an altitude of 11.6 km according to 00 UTC rawinsonde data from Grand Junction, Colorado (below).

Plots of rawinsonde data from Grand Junction, Colorado [click to enlarge]

Plots of rawinsonde data from Grand Junction, Colorado [click to enlarge]