Pyrocumulonimbus clouds over British Columbia and California

June 30th, 2021 |

GOES-17 “Red” Visible (0.64 µm, top), Shortwave Infrared (3.9 µm, middle) and “Clean” Infrared Window (10.35 µm, bottom) [click to play animation | MP4]

GOES-17 “Red” Visible (0.64 µm, top), Shortwave Infrared (3.9 µm, middle) and “Clean” Infrared Window (10.35 µm, bottom) [click to play animation | MP4]

GOES-17 (GOES-West) “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.35 µm) images (above) showed the explosive formation of large pyrocumulonimbus (pyroCb) clouds that were spawned by large wildfires in British Columbia, Canada on 30 June 2021. The 10.35 µm cloud-top infrared brightness temperatures rapidly cooled to the -50 to -60ºC range, easily surpassing the -40ºC pyroCb threshold — and pyroCb 3.9 µm cloud-top infrared brightness temperatures were warmer (darker shades of gray) than those of surrounding meteorological cumulonimbus clouds (due to the presence of smaller ice crystals and smoke particles, which were better reflectors of incoming solar radiation).

GOES-17 Fire Temperature RGB images (below) include surface reports plotted in yellow — note that the temperature reached 115ºF (46.1ºC) at Kamloops (CYKA), just southeast of the largest fire. In addition, farther to the southwest, surface observations at Lytton (CWLY) ceased as of 01 UTC (6 PM local time), as another wildfire began to destroy 90% of that town.

GOES-17 Fire Temperature RGB images, with surface reports plotted in yellow [click to play animation | MP4]

GOES-17 Fire Temperature RGB images, with surface reports plotted in yellow [click to play animation | MP4]

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GOES-17 “Red” Visible (0.64 µm, top), Shortwave Infrared (3.9 µm, middle) and “Clean” Infrared Window (10.35 µm, bottom) [click to play animation | MP4]

GOES-17 “Red” Visible (0.64 µm, top), Shortwave Infrared (3.9 µm, middle) and “Clean” Infrared Window (10.35 µm, bottom) [click to play animation | MP4]

On a smaller spatial and temporal scale, GOES-17 Visible, Shortwave Infrared and Infrared Window images (above) revealed the brief formation of a pyroCb that was produced by the Lava Fire in far northern California. A portion of the cloud top reached the -40ºC threshold (darker shades of blue) to qualify as a pyroCb.

Subtropical storm Raoni off the coast of South America

June 28th, 2021 |

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

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

GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed the circulation of Subtropical Storm Raoni (discussion issued by MARINHA) off the coast of Argentina/Uruguay on 28 June 2021.

In the corresponding GOES-16 “Clean” Infrared Window (10.35 µm) images (below), the coldest cloud tops exhibited infrared brightness temperatures around -50ºC (shades of yellow).

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

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

===== 29 June Update =====

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

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

GOES-16 Visible images (above) showed that Subtropical storm Raoni continued its northeastward motion, and was located off the coast of far southeastern Brazil on 29 June (12 UTC surface analysis | discussion).

GOES-16 Infrared images (below) indicated that Raoni was unable to maintain a persistent closed ring of cold clouds around its center.

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

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

A sequence of ASCAT surface scatterometer winds (source) from Metop-A and Metop-C (below) revealed swaths of wind speeds of 40 knots or greater within the northeastern and southwestern sectors of the system.

ASCAT winds from Metop-A and Metop-C [click to enlarge]

ASCAT winds from Metop-A and Metop-C [click to enlarge]

Tropical Depression Four off the South Carolina coast

June 28th, 2021 |

GOES-16 Red Visible (Band 2, 0.64 µm) imagery, 1056 -1431 UTC on 28 June 2021 (click to animate)

Update: Tropical Depression 4 strengthened to become Tropical Storm Danny at 1905 UTC on 28 June (link).

GOES-16 visible imagery (0.64 µm), above, from the morning of 28 June 2021, shows a compact low-level circulation east of South Carolina, steadily moving towards the coast. Deep convection with this system is offset to the east, suggestive of shear, and the shear analysis from the SSEC Tropical website, below, does show easterly shear over the system.

Wind shear analysis, 1200 UTC on 28 June 2021 (Click to enlarge)

VIIRS Day Night Band imagery, below, from Suomi-NPP at 0723 UTC on 28 June, a time with ample lunar illumination, shows convection over the center of the storm at that time.

Suomi-NPP VIIRS Day Night Band Visible (0.70 µm) imagery, 0723 UTC on 28 June 2021 (Click to enlarge)


The wind shear analysis from 1900 UTC, below, is more in line with what might be expected in a system with an exposed low-level circulation center.

Wind shear analysis, 1900 UTC on 28 June 2021 (Click to enlarge)

 

The National Hurricane Center initiated statements on this tropical system at 1500 UTC on 28 June 2021. Refer to those webpages (link) for further information. Tropical Storm warnings are in effect for parts of the South Carolina coast, from Edisto Beach to the S. Santee River.

SAR Winds over Lake Michigan compared with Radar winds

June 28th, 2021 |

RCM3 SAR winds over Lake Michigan, 1201 UTC on 28 June 2021 (Click to enlarge)

RADARSAT Constellation Mission 3 (RCM3) Synthetic Aperture Radar (SAR) wind data over southern Lake Michigan at 1201 UTC on 28 June, above (click to enlarge, taken from this website), shows a small region of strong winds just offshore of southeast Wisconsin and northeastern Illinois.  GOES-16 Band 2 visible imagery (clipped from the CSPP Geosphere website, click here for the direct link to the imagery — valid until mid-July) shows modest convection just off the Wisconsin/Illinois shorelines.

CSPP Geosphere visualization of GOES-16 Visible (Band 2, 0.64) imagery, 1200 UTC on 28 June 2021 (Click to enlarge)

Winds from the Sullivan WI (WFO MKX) radar, below, (courtesy John Gagan, SOO), show a similar structure. The challenge in comparing the SAR winds and the radar winds: The Sullivan radar beam in that location is about 5000 feet above the surface. Storm-relative velocities are about 20 kt.

1201 UTC WFO MKX Radar display showing Base Reflectivity (upper left), Storm Relative Velocities (upper right), ZDR (Lower left) and Base velocities (lower right).  Beam angle of 0.5 degrees. (Click to enlarge)