GOES-West imagery, above, from the CSPP Geosphere site, shows Hawaii in a tradewind regime (direct link to animation). The animation, from 0121 to 0556 UTC on 21 September 2023, shows the steady progression of cloud lines moving east-to-west, with embedded regions of apparent showers that generate outflow boundaries. At 0431 UTC, Sentinel-1A overflew the eastern Hawai’ian islands, and a high-resolution picture of the surface winds resulted (Data are available online as well: Normalized Radar Cross Section Data, and Winds). The three wind footprints are stitched together below.

Strong winds — nearly 30 knots — are associated with a modest looking (and decaying) convective cell just to the east of Maui. None of the convection in this scene reaches particularly high into the atmosphere; cloud top brightness temperatures are in the 5-10^o C range. The Hilo Sounding at 0000 UTC on 21 September 2023 shows a tradewind inversion top at 750 hPa, suggesting the clouds reached to about that level. (The strong winds of the Alenuihaha channel are also shown!) Note also the strong winds in the lee of the Big Island of Hawai’i.

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Sentinel orbits are such that exact repeats occur every 12 days. The Ocean Virtual Laboratory allows a user to track the overpasses.

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1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) included time-matched (+/- 3 minutes) plots of SPC Storm Reports — which showed severe thunderstorms that moved eastward and southeastward across parts of Kansas, Oklahoma and Texas on 19 September 2023.

1-minute GOES-16 “Clean” Infrared Window (10.3 µm) images (below) indicated that the coldest pulsing overshooting tops associated many of the storms exhibited infrared brightness temperatures in the -60 to -65ºC range (darker shades of red). These thunderstorms produced a tornado in Kansas, hail up to 2.75 inches in diameter in Texas and damaging winds up to 74 mph in Oklahoma.

5-minute CONUS Sector GOES-16 Visible images with overlays of the CAPE, Lifted Index and Total Precipitable Water derived products (below) showed that these storms intensified as they moved into a corridor of instability and moisture. CAPE values were as high as 1400 J/kg, LI values reached -6ºC and TPW values exceeded 1.60 in.

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Daily imagery from the CSPP Geosphere website above, at 0400 UTC from 12-19 September, show haze (highlighted by the blue arrows) moving across the Pacific Ocean. The haze is likely a by-product of the ongoing eruption at Kilauea. The initial burst of haze moved beyond the view of GOES-West by 19 September, but imagery shows other regions of haze are following behind. The haze has moved into the western Pacific, and has affected visibility in the northern Marianas Islands, as noted in the Forecast Discussion from the National Weather Service in Guam, shown below.

Multi-spectral satellite imagery from earlier this morning showed a
narrow band of haze reaching the Marianas along easterly trade-wind
flow pointing back to the Hawaii region. This haze has occasionally
dropped visibility at the Saipan airport earlier this morning, but
appears to have improved slightly in the afternoon hours. It is
likely that this haze originated from the recent Kilauea activity
from September 10th-16th of last week. High uncertainty remains to
exactly for how long this haze might persist, but it is expected to
be perceivable through at least Wednesday morning.

The image below, from the Guam NWS Facebook page, shows Garapan on Saipan.

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The progression of haze from Hawaii to the Marianas is more easily viewed in a map that includes both Hawaii and Guam. Daily views (all at 0400 UTC as in the animation above) of GOES-18 Band 1 (0.47 µm) imagery show the haze approaching the Marianas by 0400 UTC on 18 September.

The toggle below of GOES-18 and Himawari-9 Band 1 imagery, both at 0400 UTC on 17 September, shows the importance of view angle relative to the Sun in detecting the presence of haze. Haze that is apparent in GOES-18 imagery (near 160^oE) is not apparent in Himawari-9 imagery because of differences in view angle and the location of the Sun relative to the satellite.

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JMA Himawari-9 True Color RGB images created using Geo2Grid (above) helped to highlight the westward transport of hazy volcanic smog (vog) from Hawai`i to the Mariana Islands during the 13-18 September time period. A plot of surface report data from Saipan Island (below) indicated that the surface visibility dropped as low as 5-6 miles (from 2100-2200 UTC on 18 September, or 7-8 AM ChST on 19 September) when the vog arrived. The satellite imagery was certainly convincing, but HYSPLIT model back trajectories also helped to implicate Kilauea vog as the source of haziness observed at Saipan (with subsidence occurring during the period of long-range transport).

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Thanks to Brandon Aydlett, the Science and Operations Officer at Guam, for the alert on the haze.

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The GXI (GeoXO Imager) instrument to be flown on the GeoXO (Geostationary eXtended Observations) satellite, scheduled for launch in the mid-2030s, is intended to replace ABI data from the current set of GOES-R Satellites. One of the novel channels to be added to GXI senses infrared information at 5.15 µm, a wavelength at which absorption by water vapor occurs. As the weighting functions below show (source: this paper by Milller et al.), the wavelength is sensing information from far down in the atmosphere (in clear skies), much closer to the surface than the current water vapor infrared channels (bands 8-10, 6.19 µm, 6.95 µm and 7.34 µm) on the ABI (as shown here for a mid-latitude Summer atmosphere).

The animation below show simulated 5.15 µm and 7.3 µm imagery for a case in 2019. These 5.15 µm and 7.34 µm imagery are simulated using the Pressure layer Fast Algorithm for Atmospheric Transmittances (PFAAST) model applied to a 1-km ECMWF nature run (XNR1K). The spatial resolution is 2 km and imagery is courtesy of Zhenglong Li. Pay especial attention to the gradients in the low-level field (5.15 µm) at around 1215 UTC over the Gulf of Mexico and around 1545 UTC over the lower Mississippi River — regions highlighted by boxes. Note how such features are absent in the 7.3 µm, the water vapor channel on the ABI that senses infrared information from lowest down in the atmosphere. Convection subsequently develops within those boxes along these gradients that are apparent at 5.15 µm before they are at 7.34 µm. A conclusion might be: data from GXI will likely allow a forecaster to determine earlier where convection might subsequently develop.

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