1-minute Mesoscale Domain Sector GOES-18 (GOES-West) Infrared Window images (above) showed Category 2 Hurricane Lowell as its center moved northeastward (track) and passed about 40 miles west of the Hawaiian island of Ni’ihau on 08 September 2026. While sparse, 1-minute GOES-18 GLM Flash Points did indicate that some intermittent lightning activity was present. A well-defined eye was no longer discernible in GOES-18 Infrared Window imagery during the time period shown.

Tendrils of transverse banding were very apparent within the southwestern and western quadrants of Lowell (below), embedded in the anticyclonic outflow at high altitudes. (Transverse banding is a satellite signature often associated with aircraft turbulence, as discussed in these blog posts.)

A closer view of 1-minute GOES-18 Infrared Window images (below) allowed for a better depiction of the peak wind gusts that occurred on the island of Kaua’i — which included 92 mph at RAWS site Puu Lua, and 73 knots (84 mph) at METAR sites Lihue (PHLI) and Kekaha (PHBK). A list of wind gusts across the other Hawaiian islands included 80 mph in Maui County and 75 mph in Honolulu County.

The coldest cloud-top infrared brightness temperature associated with one of Lowell’s convective bursts was -85.02 C at 0639 UTC (below).

According to a plot of rawinsonde data from Lihue at 0600 UTC on 08 September (below), the -85 C cloud-top infrared brightness temperature roughly corresponded to the the Most Unstable (MU) air parcel’s Maximum Parcel Level (MPL), located around 110 hPa or 16.3 km.

Also of note in the Lihue sounding shown above was the Precipitable Water (PW) value of 2.70 inches — which, according to a climatology of Lihue sounding PW (below) was a new record daily maximum PW for 08 September, and also may have been the highest PW on record for Lihue (eclipsing the previous record of 2.47 inches).

The MIMIC Total Precipitable Water product (below) showed that Lowell was drawing rich tropical moisture northward into its circulation from the Intertropical Convergence Zone, as the hurricane eventually turned northeastward (track) to pass over the far western part of the Hawaiian island chain.

A Metop-C AMSU Rain Rate derived product at 0804 UTC (below) did happen to show a ragged eye-like structure associated with Lowell at that time, just southwest of Ni’ihau. Rainfall across the Hawaiian Islands was as high as 21.11 inches at Kilohana on Kaua’i.

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As previously documented on this blog, Hurricane Lowell first reached Category 5 intensity on 02 September.

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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.

Large #eruption of #Krakatau #volcano (#Indonesia) started at ~16:30 UTC on Sept 4, and is continuing as of 13:00 UTC on Sept 5. #NOAA-20 OMPS satellite data showing injection of ~0.2 Tg SO? into the upper troposphere by 06:50 UTC on Sep 5.

— Prof. Simon Carn (@simoncarn.bsky.social) 2026-09-05T13:45:18.892Z

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.

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1-minute Mesoscale Domain Sector GOES-18 (GOES-West) Visible images (above) revealed mesovortices within the eye of Hurricane Lowell as it reached Category 5 intensity over the Central Pacific by 2100 UTC on 02 September 2026. Plots of 1-minute GOES-18 GLM Flash Points highlighted the intermittent lighting activity within the surrounding eyewall.

A larger-scale view of 1-minute GOES-18 Infrared Window images (below) showed that the coldest cloud-top infrared brightness temperatures were in the -75 to -80 C range (brighter white pixels embedded within dark black regions).

Products from the CIMSS Tropical Cyclones site indicated that Lowell was moving through an environment of low deep-layer wind shear (above) and was traversing warm Sea Surface Temperatures (below) — two factors that were favorable for Lowell’s rapid intensification (DMINT | SATCON).

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1-minute Mesoscale Domain Sector GOES-19 (GOES-East) Visible and Infrared Window images (above) showed Tropical Storm Edouard as it made landfall in far southwestern Louisiana at 1920 UTC on 01 September 2026. Plots of 1-minute GOES-19 GLM Flash Points highlighted the intermittent lightning activity associated with Edouard. Pulses of overshooting tops exhibited infrared brightness temperatures in the -75 to -80 C range (brighter white pixels embedded within dark black regions). At inland METAR sites, the peak wind gust was 60 kts (69 mph) at Beaumont/Port Arthur, Texas — with a peak wind gust of 90 mph south of Port Arthur.

Edouard was moving through an environment of low deep-layer wind shear (below), a factor which favored intensification.

Sea Surface Temperatures across the northwestern Gulf of Mexico were also very warm (below) — and water temperatures just off the Gulf Coast (where Edouard intensified to a Tropical Storm shortly before making landfall) were 31 C.

An AMSR Microwave image at 1908 UTC (below) indicated that the eyewall of Edouard was not fully closed at that time.

A MIMIC Total Precipitable Water image at 2200 UTC (below) showed that significant moisture had already moved inland across southeast Texas as Edouard was making landfall.

1-minute GOES-19 Infrared Window images that included overlays of Flood Watch/Warning/Advisory polygons (below) displayed several Flash Flood Warnings (red polygons) and even a Flash Flood Emergency (bold red polygon). Up to 17 inches of rainfall occurred across southeast Texas during the 24-hour period ending at 12 UTC on 02 September, and over 24 inches during the 48 hours ending at 12 UTC on 03 September.

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