Storm Reports for the first two weeks of November 2023 show that the all but one of the reports have occurred over lower Michigan, where large hail (1 to 1.5 inches in diameter) occurred shortly after sunrise on 6 November in Newaygo County (1423 UTC), Montcalm County (1440, 1443 UTC) and Kent County (1448 UTC). What satellite imagery could be used to monitor this out-of-season development? The airmass RGB animation, above, from 0801 – 1501 UTC, shows the orangish shading typical of an airmass with high potential vorticity impinging on western Lower Michigan. Is that orange region really a region where Potential Vorticity is elevated? The image below compares the 1200 UTC (6-h GFS forecast) of pressure on the 2 PVU (taken from this source) to the 1201 UTC Airmass RGB. Strong convection develops over Lake Michigan after 1200 UTC and moves into southwestern lower Michigan where the severe weather occurred around 1400 and 1500 UTC.

---

GOES-R provides Derived Stability Indices as one of its Level 2 Products. The clear-sky stability products include the Total Totals Index and the animation below shows the values along with the GOES-16 Clean Window infrared imagery. Values in excess of 45 occasionally appear in clear sky pixels over western lower Michigan as the stronger convection develops. Values are even larger to the west/southwest over Wisconsin where dynamic forcing is presumably less strong (given that convection did not develop there; here is a 6-h forecast of pressure on the 330 K surface along with cyclonic vorticity at 850 mb; note the strongest dynamics at 12 UTC are over northeast WI).

GOES-16 low-level water vapor imagery, below, shows the characteristic red signature sometimes associated with Elevated Mixed Layers (EMLs, features that are conducive to convection) moving towards lower Michigan. The weighting function from 45 N, 95W computed from 1200 UTC 6 November 2023 GFS data (here, taken from this source), shows a peak contribution from near 500 mb. The 1200 UTC Chanhassen Minnesota soundings (here, from this source), shows near dry-adiabatic conditions at 500 mb, i.e, a possible EML; if convection reaches that level, one might expect vigorous ascent.

GOES-16 Visible imagery, below, colored by the L2 cloud height product, shows both the convective texture of the clouds over Newaygo, Montcalm and Kent counties, and the relatively high heights of those clouds.

GOES-16 Cloud Top Heights, below, from 1401-1456 UTC, show the highest clouds tracking across southern Newaygo county and northern Kent and Montcalm counties from 1426 – 1451 UTC.

---

The visible imagery colored with the cloud-top height mimics what happens with the Sandwich RGB, shown below. For this RGBs, the default scaling from 0-255 was changed to 0-150 for this early morning/low light event. The cold cloud tops of the strongest convection are apparent, tracking in the same region of Newaygo/Montcalm/Kent counties between 1400 and 1500 UTC, when the severe weather was occurring.

---

A GOES-16 Mesoscale Domain Sector provided 1-minute imagery over the area — Visible and Infrared images that included time-matched (+/- 3 minutes) plots of SPC Storm Reports (in Newaygo/Montcalm/Kent counties) are shown below. In the vicinity of the hail reports, overshooting tops were evident in the Visible images and cloud-top 10.3 µm infrared  brightness temperatures were as cold as -60ºC (darker red enhancement).

---

Thanks to TJ Turnage, Science and Operations Officer (SOO) at the Grand Rapids MI forecast office, for alerting us to this event.

View only this post Read Less

GOES-16 (GOES-East) SO2 RGB and Ash RGB images (above) showed a remnant volcanic cloud from the 31 October Klyuchevskaya eruption as it moved over southern Saskatchewan, northern North Dakota and far northwestern Minnesota on 06 November 2023. The volcanic cloud exhibited brighter shades of orange-yellow in the SO2 RGB imagery, and darker shades of blue in the Ash RGB imagery — as seen in RGB comparisons over southern Saskatchewan (north of CWEN-CWVN) at 0301 UTC and northwestern North Dakota at 0801 UTC (below).

The 0301 UTC and 0801 UTC image times corresponded to Volcanic Ash Advisories that were issued by the Montreal VAAC and the Washington VAAC (below).

GOES-16 SO2 RGB and Ash RGB images at 1601 UTC (below) showed the volcanic cloud over far northwestern Minnesota (in the vicinity of KPKD).

The qualitative appearance on SO2 and Ash RGB imagery was suggestive of a volcanic cloud that was a mixture of SO2 and ash (with more SO2 than ash) — and a radiometrically-retrieved Ash Loading product from the NOAA/CIMSS Volcanic Cloud Monitoring site (below) indicated that the ash content of the cloud was relatively low (0.5-1.0 grams per square meter, violet).

View only this post Read Less

JMA Himawari-9 Ash RGB images created using Geo2Grid (above) showed the complex transport of Kyluchevskaya volcanic plumes — which were a mixture of ash (shades of pink to red-orange) and SO2 (brighter shades of yellow) — during the 3-day period from 31 October to 02 November 2023. Much of the transport was influenced by a middle-tropospheric closed low that was progressing from Kamchatka toward the Aleutian Islands (500 hPa analyses).

GOES-18 (GOES-West) Air Mass RGB images (below) also depicted the volcanic plume — the portions that were dominated by SO2 exhibited brighter shades of pink (since the Red component of this RGB uses the 7.3 µm spectral band, which is sensitive to SO2 absorption). Volcanic Ash Advisories cautioned aviation interests of ash extending to altitudes of 36000 ft.

While there were very few Pilot Reports (PIREPs) in the general vicinity of the volcanic plume — since aircraft were wisely avoiding the risk of an ash encounter — there were 3 PIREPs that mentioned Volcanic Ash (VA) (below).

One of the more explosive events during this prolonged eruption period began around 0220 UTC on 01 November. Radiometrically-retrieved Ash Height and Ash Loading products from the NOAA/CIMSS Volcanic Cloud Monitoring site are shown below — which indicated that the resulting ash-rich volcanic cloud reached heights of 10-12 km.

View only this post Read Less

GOES-18 (GOES-West) Dust RGB images (above) showed a plume of resuspended volcanic ash (brighter shades of violet) from Mount Aniakchak, which was being lofted by strong SE winds — gusting as high as 45 knots at Port Heiden — and transported NW across Bristol Bay on 26 October 2023. A Volcanic Ash Advisory was issued at 2130 UTC (below), cautioning pilots of hazardous airborne ash between the Surface and an altitude of 3000 feet.

While a subtle signature of the plume was also evident in GOES-18 Ash RGB imagery, it was a bit more obvious in the Dust RGB (below) — both RGBs use the same spectral bands and spectral band differences, but the individual RGB components are scaled differently (so an examination of both is advised, in order to determine which RGB is best to track this type of ash-related feature).

GOES-18 True Color RGB images from the CSPP GeoSphere site (below) provided a good view of the resuspended ash plume (shades of tan) as it moved NW across the water.

View only this post Read Less