Eruption of Anak Krakatau in Indonesia
JMA Himawari-9 Ash RGB images created using Geo2Grid (above) showed a major eruption of Anak Krakatau in Indonesia, which began around 1620 UTC on 04 September 2026. A middle-tropospheric volcanic ash cloud (depicted by shades of red to magenta) remained closer to the volcano — while an upper-tropospheric SO2 cloud (shades of yellow-green) moved rapidly west-southwestward.
After sunrise on 05 September, Himawari-9 True Color RGB images (below) showed the middle-tropospheric volcanic ash cloud as shades of brown, with pulses of brighter white upper-tropospheric volcanic cloud (a mixture of water vapor, ash and SO2) moving quickly westward away from the volcano. Ash eventually drifted northward over parts of the island of Sumatra, and eastward over parts of the island of Java.
A radiometrically-retrieved Ash Height product from the NOAA/CIMSS Volcanic Cloud Monitoring site (below) indicated that ash from the eruption likely reached maximum altitudes in the 18-20 km range (black enhancement).
A plot of rawinsonde data from Jakarta International Airport, located east of Krakatau on the island of Java (below) showed lighter and variable-direction winds in the mid-troposphere (within the 650-450 hPa pressure layer, or altitudes of 3.7-7.0 km), with stronger easterly winds in the upper troposphere (especially within the 300-200 hPa pressure layer, or altitudes of 9.7-12.5 km).
===== 06 September Update =====
On 06 September, Himawari-9 True Color RGB images (above) showed the hazy signature of residual lower-altitude volcanic ash across the region — although the ash was not as thick as on the previous day, so it did not exhibit the same shades-of-brown signature. Nearly 3000 flights were suspended from Jakarta International Airport during its 2-day closure after the eruption of Krakatau.
A NOAA-21 VIIRS Day/Night Band image at 0533 UTC on 06 September (below) included a cursor sample of the Jakarta International Airport (identifier WIII) METAR observation, which included Volcanic Ash (VA).
A plot of surface observation data from Jakarta International Airport (below) indicated that Volcanic Ash was reported beginning at 1900 UTC on 05 September, with the volcanic ash restricting surface visibility to 4-7 miles.
