Strong convection developed over southern Lake Michigan early in the morning on 5 August, as depicted in the animation above. Multiple pilot reports of moderate turbulence occurred in/near the developing convection. Gravity waves developed on the upwind side of the deep convection, shown in the enhancement above as darker blue (that is, warmer brightness temperatures); the circulation with the gravity waves had an observable effect on approaching clouds as well. Note, for example, how the convection initially on the eastern central Lake Michigan shoreline (highlighted by the black arrow in the animation below) dissipates as it moves under the gravity wave structure. Clouds moving in from the northwest also change abruptly as they encounter the gravity wave barrier (and its vertical circulation).

Weighting Functions from the 1200 UTC Detroit Rawinsonde site, below (source), show contributions to the signal in the Band 8 water vapor imagery originating from a layer between 500 and 200 hPa.

The strong convection formed in the exit region of a 100-knot jet at 200 mb as shown in the analysis below. Note the large scale difluence in the region: north-northwest winds (40 knots) at Lincoln, IL; Northwest winds at 55 knots at Detroit MI; West winds at 65 knots in Maniwaki, QB!

The CIMSS Turbulence Product — that predicts via a Machine-learning algorithm the likelihood of Moderate or Greater (MOG) turbulence — increased markedly as the convection developed, as shown below.

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GOES-16 Visible imagery, below (from the CSPP Geosphere site), also shows the gravity waves, and their interaction with/affect on convection.

I am grateful to Greg Mann and TJ Turnage, Science and Operations Officers (SOOs) in Detroit and Grand Rapids, respectively, for their comments on this event (and for letting me know about it!)

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MIMIC Total Precipitable Water fields, above (source), for the 24 hours ending at 1700 UTC 4 August 2024, show the cyclonic spin (and ample moisture) associated with Tropical Storm Debby as the system moves northward from Cuba into the eastern Gulf of Mexico. (A tropical disturbance is also present south of Mexico in the tropical Eastern Pacific.) Abundant moisture is also present off the southeast coast of the USA, and as Debby moves north (landfall as a hurricane is predicted Monday morning in Florida’s Big Bend region; for the latest on Debby, consult the website of the National Hurricane Center), the storm’s circulation will draw that moisture inland. Very heavy rain is anticipated from Florida northeast into the Carolinas.

Scatterometry from OSCAT-3 on India’s OceanSat-3 and from ASCAT on EUMETSAT’s Metop-C, below, (available here) captured the changes in the circulation between 0515 UTC and 1607 UTC on 4 August 2024. At 0515 UTC, the strongest winds were on Debby’s eastern flank. Unfortunately, Metop-C (and Metop-B, not shown) did not sample that part of the storm during the day on 4 August.

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The animation below shows half-hourly imagery from 0406 – 1836 UTC on 4 August, bracketing the times of the Scatterometry overpasses above. Debby shows an increase in organization by the end of the animation, with the development of a central core of convection (albeit small!). Dry mid-level air is suggested to the west of the storm by the yellow enhancement in the water vapor imagery and the general lack of convection over the central Gulf of Mexico, but the dry air does not appear to be affecting the evolution of the system.

A GOES-16 mesosector (#2) has been positioned over the storm. One-minute imagery, below, for the hour ending 1850 UTC on 4 August 2024 (combined with GLM observations of Flash Extent Density) show the slow increase in organization of the storm.

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For the latest information on Debby, refer to the webpages of the National Hurricane Center. The SSEC/CIMSS Tropical Weather website also contains storms information. You can find more information as well at the websites of National Weather Service offices in Tallahassee, Jacksonville, Charleston (SC), Columbia, Atlanta and Wilmington (NC) . NOAA’s Weather Prediction Center is issuing excessive rainfall graphics for the storm as well, with 16-20 inches of rain predicted from Savannah GA to northeast of Charleston SC.

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The Park Fire developed to the northeast of Chico California on 24 July. Day Night Band visible (0.7 µm) imagery, below (from here), shows the fire over the course of the next four days. It grew very quickly on the 25th and 26th. It appears that by the overnight hours on the 28th that the fire was not burning quite so intensely. The fire persisted through the 29th however.

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Geosphere True Color imagery (direct link to animation, starting with just a bit of pre-sunrise Night Microphysics to highlight regions where active burning continues) show an extensive smoke pall associated with the fire. The True Color imagery also hints at the large burn scar from the fire.

This website shows model forecasts of smoke. The predictions valid at 1000 UTC on 28 July 2024, below, show near-surface smoke and total column integrated smoke. The smoke plume from the Park Fire is moving northeastward into central Canada. Most of the smoke beyond California and Nevada has been lofted away from the surface.

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The NGFS Real Earth display of the GeoColor imagery and detected fire pixels for 27 and 30 July 2024, shown below, shows the reduction in the size of the active fire.

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The toggle below of NOAA-20 False Color imagery derived from VIIRS imagery at this website, between 22 and 29 July 2024, shows a very large burn scar (in brown) from the Park Fire. Burn scars from previous fires are also scattered throughout the image.

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A clear night over the Great Lakes — associated with a large High Pressure System, shown below in the 0600 UTC Surface Analysis — allowed a high-resolution view of Lake Surface Temperatures. There are thin filaments of colder waters hugging different coastlines: the eastern shore of Lake Michigan, the western shore of the Upper Peninsula of Michigan, the southern shore of Manitoulin Island in northern Lake Huron. In these regions, off-shore winds are likely causing deeper (colder) sub-surface waters to upwell. The National Weather Service in Duluth noticed a similar event on 23 July (link to Twitter/X).

Do you think those surface temperatures are warmer than normal as a whole? The purple enhancement over Lake Superior shows temperatures cooler than 60^oF. Michigan and Huron show temperatures around 70^oF (green) except for Saginaw Bay, where it’s in the mid-70s. Western Lake Erie is 77-78 ^oF; Lake Ontario is around 75^oF at its warmest point. GLERL maintains line plots of basin-wide averages: Superior, Michigan, Huron, Erie and Ontario. All five lakes are warmer on 25 July than the long-term average.

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