Multi-day eruptions of the La Soufrière volcano in the West Indies

April 9th, 2021 |

GOES-16 Ash RGB images [click to play animation | MP4]

GOES-16 Ash RGB and SO2 RGB images [click to play animation | MP4]

GOES-16 (GOES-East) Ash RGB and SO2 RGB images (above) displayed signatures of two distinct eruptions of the La Soufrière volcano on the island of Saint Vincent in the West Indies on 09 April 2021. Signatures of high ash or SO2 concentrations appear as brighter shades of pink on the RGB images. Significant ash fall on parts of the island forced evacuations of some communities. The SO2 signature for the second eruption was much more pronounced and widespread.

The corresponding GOES-16 “Clean” Infrared Window (10.35 µm) images (below) showed that coldest cloud-top infrared brightness temperatures associated with the first eruption (which began shortly before 1250 UTC) were -62ºC, while the second and more explosive eruption (which began shortly after 1900 UTC) exhibited temperatures as cold as -78ºC.

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]

GOES-16 True Color RGB images created using Geo2Grid (below) showed the characteristic tan-colored hues of a volcanic cloud having significant ash loading.

GOES-16 True Color RGB images [click to play animation | MP4]

GOES-16 True Color RGB images (credit: Tm Schmit, NOAA/NESDIS/ASPT) [click to play animation | MP4]

A number of quantitative radiometrically-retrieved products are available from the NOAA/CIMSS Volcanic Cloud Monitoring site — some of which include Ash Height, Ash Probability, Ash Loading and Ash Effective Radius (below).

Ash Height product [click to play animation | MP4]

Ash Height product [click to play animation | MP4]

Ash Probability product [click to play animation | MP4]

Ash Probability product [click to play animation | MP4]

Ash Loading product [click to play animation | MP4]

Ash Loading product [click to play animation | MP4]

Ash Effective Radius product [click to play animation | MP4]

Ash Effective Radius product [click to play animation | MP4]

===== 10 April Update =====

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]

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Clean” Infrared Window (10.35 µm) images (above) displayed the volcanic cloud associated with numerous explosive eruptions that continued during much of the day on 10 April. The coldest cloud-top infrared brightness temperature of -84.8ºC occurred at 1058 UTC (and would have been missed by the routine 10-minute images over that area). This cold overshooting top infrared brightness temperature roughly corresponded to an altitude of 18.2 km, or 1.8 km above the tropopause according to 12 UTC rawinsonde data from Barbados (below).

Plot of 12 UTC rawinsonde data from Grantley Adams, Barbados [click to enlarge]

Plot of 12 UTC rawinsonde data from Grantley Adams, Barbados [click to enlarge]

GOES-16 True Color RGB images within +/- 30 minutes of the -84.8ºC infrared brightness temperature are shown below — an abrupt penetration of the existing volcanic cloud top was seen by the newly-developed overshooting top.

GOES-16 True Color RGB images [click to play animation MP4]

GOES-16 True Color RGB images [click to play animation | MP4]

GOES-16 Ash RGB images (below) indicated high concentrations of volcanic ash (brighter shades of pink) spreading out slowly around the island of Saint Vincent at lower altitudes, and being transported rapidly eastward at higher altitudes. To the north, light ash fall was limiting the surface visibility to 2-3/4 miles at Saint Lucia (TLPL) — while farther to the east heavier ash fall on the island of Barbados visibility was occasionally being restricted to around 1/2 mile (1000 meters) at Grantley Adams Airport (TBPB).

GOES-16 Ash RGB images [click to play animation | MP4]

GOES-16 Ash RGB images [click to play animation | MP4]

GOES-16 SO2 RGB images (below) showed that high concentrations of SO2 (shades of red to orange) were also being emitted during the series of eruptions.

GOES-16 SO2 RGB images [click to play animation | MP4]

GOES-16 SO2 RGB images [click to play animation | MP4]

GOES-17 (GOES-West) provided an oblique view of these volcanic clouds, which were very near the extreme limb of the satellite view — a comparison of GOES-17 and GOES-16 Full Disk sector “Red” Visible (0.64 µm) images for one of the more explosive events on 10 April is shown below. The magnification factor is identical in both sets of GOES images, though they are displayed in the native projection of each satellite. A similar comparison of 10-minute Full Disk sector GOES-17 and 1-minute Mesoscale sector GOES-16 Visible images is available here.

“Red” Visible (0.64 µm) images from GOES-17 (left) and GOES-16 (right) [click to play animation | MP4]

A toggle between True Color RGB images from GOES-16 and GOES-17 at 1930 UTC (below) further illustrates the parallax displacement associated with the large viewing angle from GOES-17.

True Color RGB images from GOES-16 and GOES-17, at 1930 UTC (credit: Tim Schmit, NOAA/NESDIS/ASPB) [click to enlarge]

True Color RGB images from GOES-16 and GOES-17, at 1930 UTC (credit: Tim Schmit, NOAA/NESDIS/ASPB) [click to enlarge]

===== 11 April Update =====

NOAA-20 VIIRS Day/Night Band (0.7 µm) image (credit: William Straka, CIMSS) [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm) image (credit: William Straka, CIMSS) [click to enlarge]

A nighttime NOAA-20 VIIRS Day/Night Band (0.7 µm) image (above) revealed mesospheric airglow waves propagating northeastward and eastward away from the volcano, which was still actively erupting every few hours.

The periodic violent eruptions continued into the daytime hours on 11 April — and GOES-16 Mid-level Water Vapor (6.9 µm) images (below) showed shock waves emanating radially outward from the initial volcanic cloud location following each eruption.

GOES-16 Mid-level (6.9 µm) Water Vapor images [click to play animation | MP4]

GOES-16 Mid-level (6.9 µm) Water Vapor images [click to play animation | MP4]

===== 13 April Update =====

GOES-16 "Clean" Infrared Window (10.35 µm) and Ash RGB images [click to play animation | MP4]

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

Eruptions continued on the morning of 13 April, as seen in GOES-16 Infrared and Ash RGB images (above).

A 4-day animation of GOES-16 Ash RGB images — covering the period from 1230 UTC on 09 April to 1230 UTC on 13 April — is shown below.

GOES-16 Ash RGB images, 09-13 April [click to play MP4 animation]

GOES-16 Ash RGB images, 09-13 April (credit Tim Schmit, NOAA/NESDIS/ASPB) [click to play MP4 animation]

Interpreting SAR data over the Bering Sea

April 8th, 2021 |

GOES-17 ABI Band 2 (0.64 µm) and Band 5 (1.61 µm) at 1740 UTC on 8 April 2021 (Click to enlarge)

The toggle above shows GOES-17 ABI Band 2 (“Red Visible” at 0.64 µm) and Band 5 (“Snow/Ice” at 1.61 µm) imagery at 1740 UTC on 8 April 2021. 60ºN and 170ºW lat/lon lines are included in yellow, as well as Nunivak Island.  There is evidence of sea ice extending from south of Nunivak northwestward;  visible 0.64 µm imagery  shows much greater reflectance compared to 1.61 µm snow/ice imagery.  It’s much harder to view the ice edge in the snow/ice channel because reflectances in that channel for ice and water are similar.

Compare the toggle above to the Sentinel-1A Synthetic Aperture Radar (SAR) image at 1735 UTC on 8 April 2021, shown below.   The stark wind difference (red vs. blue) in the SAR wind image below is in reality a change in ocean state, with ice over the red region and open water over the blue.  (Here is the Sea Ice analysis for 8 April from the Alaska Sea Ice Program (ASIP)).  Interpretation of SAR winds requires a knowledge of the presence of ice.

Sentinel 1-A analysis at 1735 UTC on 8 April 2021 (Click to enlarge)

Cyclone Seroja

April 5th, 2021 |

Himawari-8 ‘Target Area’ clean window infrared (10.41 µm) imagery, 1224 – 2018 UTC on 5 April 2021 (Click to animate)

Himawari-8 ‘Target Area’ imagery (with a 2.5-minute timestep) on 5 April show the evolution of Cyclone Seroja over the Timor Sea northwest of Australia. (Click here for an mp4 animation). Periodic bursts of deep convection (black and white in the color-enhancement) are apparent in the center of the storm. Analyses from the CIMSS Tropical Weather Site (link) show the storm in a region of warm Sea Surface Temperatures. Modest shear is present and it is changing the convective core of the storm in the animation above from circular to elongated over the 8-hour animation. However, strengthening is forecast.

Screen capture of SSTs over the Timor Sea, wind shear, and forecast path of Cyclone Seroja (Click to enlarge)

Visible imagery at sunrise on 6 April shows the evolution of the storm.

Himawari-8 visible (0.64 µm) imagery, 2152 – 2304 UTC on 5 April 2021 (Click to enlarge)

Himawari-8 imagery courtesy JMA. You can also view satellite imagery over the area from KMA.


Update 8 April


Himawari-8 imagery (10.41 µm), below, from 0300-1610 UTC on 8 April, show a large cirrus canopy initially over Seroja eroding (You can see the 0300 and 1610 UTC images alone toggling here) Can you tell from this infrared imagery where the storm center sits?

Himawari-8 clean window infrared (10.41 µm) (full disk) imagery, 0300 – 1610 UTC on 8 April 2021 (Click to animate)

This is certainly a case where microwave imagery can (and should!) be used to better pinpoint the circulation center.  ASMU-B imagery at 89 GHz (from here), below, storm-centered at 2307 UTC 7 April, 0207 8 April and 1143 UTC on 8 April show a storm center near 18ºS, 111.5ºE at around 1200 UTC on 8 April.  Here is the Himawari-8 Clean Window infrared at 1140 UTC.  Could you place the center near its microwave-suggested center using this infrared imagery?

AMSU-B imagery at 2307 UTC 7 April, 0206 8 April and 1143 8 April. Satellite Platform as indicated in the image. Click to enlarge)

Imagery from the CIMSS Tropical Website (link), below, show that Seroja on 8 April was traversing a region of low shear.  Sea surface temperatures at present under the storm are warm; however, the projected path of the storm is towards cooler ocean waters.  There is abundant upper-level divergence over the storm and to the northwest of Seroja as well.

Maps of atmospheric wind shear, sea-surface temperatures and upper-level divergence, ca. 1500 UTC on 8 April 2021. The path of the storm, and the projected path of the storm are also noted.

Radarsat-2 Synthetic Aperture Radar (SAR) wind data (from this website), shown below, from 1054 UTC on 8 April, can also be used to infer a circulation center.

Radarsat-2 SAR Data over Seroja, 1054 UTC on 8 April 2021 (Click to enlarge)

Heavy rainfall and flooding associated with Tropical Cyclone Seroja

April 4th, 2021 |

MIMIC Total Precipitable Water product [click to play animation | MP4]

MIMIC Total Precipitable Water product [click to play animation | MP4]

The incipient circulation of Cyclone Seroja moved very slowly across the island of Timor in Indonesia during the 03 April – 04 April 2021 period — and the MIMIC Total Precipitable Water product (above) depicted very high values over that area (just northwest of Australia).

At Kupang’s El Tari Airport, precipitation amounts included 547 mm (21.5 inches) during the 48 hours ending at 00 UTC on 05 April — with the heaviest amounts of 106 mm (4.2 inches) in 6 hours and 80 mm (3.1 inches) in 3 hours occurring during the 00-06 UTC period on 04 April when the pressure was falling as Cyclone Seroja began to slowly organize and intensify (below). Flash flooding affected much of the island, with multiple deaths being reported.

Time series plot of surface observations at El Tari Airport, Kupang [click to enlarge]

Time series plot of surface observations at El Tari Airport, Kupang, Indonesia [click to enlarge]

JMA 2.5-minute interval rapid scan Himawari-8 “Clean” Infrared Window (10.4 µm) images (below) revealed a few convective bursts — with cloud-top infrared brightness temperatures of -90ºC and colder (yellow pixels embedded within darker shades of purple) — in the vicinity of Kupang (station identifier WATT) between 04 UTC on 04 April and 00 UTC on 05 April.

JMA Himawari-8 “Clean” Infrared Window (10.4 µm) images [click to play animation | MP4]

JMA Himawari-8 “Clean” Infrared Window (10.4 µm) images [click to play animation | MP4]

A NOAA-20 VIIRS Infrared Window (11.45 µm) image at 0550 UTC visualized using RealEarth (below) showed one lone -90ºC pixel within a convective burst centered just north of Kupang.

NOAA-20 VIIRS Infrared Window (11.45 µm) image at 0550 UTC on 04 April [click to enlarge]

NOAA-20 VIIRS Infrared Window (11.45 µm) image at 0550 UTC on 04 April [click to enlarge]


CMORPH estimates of 7-day precipitation (available in RealEarth) over the region show 300-400 mm over West Timor, and values exceeding 700 mm (!!) over the adjacent ocean.

7-day CMORPH accumulation of precipitation ending 0000 UTC 5 April 2021 (Click to enlarge)