Today at 16:55 UTC, NOAA decommissioned NOAA-19, the most recently launched of the remaining legacy NOAA POES spacecraft. NOAA-19 launched on February 6th, 2009 and become operational on June 2nd, 2009. For the last 16 years, NOAA-19 has provided routine weather observations of the entire globe from low-earth orbit.

The AVHRR visible/IR imager and AMSU-A/MHS set of microwave sounders were both functioning well on NOAA-19 in its final days. However, due to a spacecraft battery failure on August 9th, the decision was made to accelerate the decommissioning timeline by about 6 days. The HRPT direct broadcast system on the spacecraft started to falter on August 11th, so the final daytime overpass of Wisconsin by NOAA-19 (with valid science data) was received by SSEC’s Madison antenna at 15:56 UTC on August 10th. Below is a selection of the AVHRR Level 1 imagery from that pass, along with AVHRR Level 2 Sea Surface Temperature retrievals from CSPP ACSPO, and AMSU-A/MHS Level 2 Total Precipitable Water and Rain Rate products from CSPP MiRS.

		[Inactive]
AVHRR Band 1: “Red Visible” [0.63 µm]	AVHRR Band 2: “Vegetation Near-IR” [0.86 µm]	AVHRR Band 3A: “Snow/Ice Near-IR” [1.61 µm]
AVHRR Band 3B: “Shortwave IR Window” [3.74 µm]	AVHRR Band 4: “Legacy IR Window” [10.8 µm]	AVHRR Band 5: “Dirty IR Window” [12.0 µm]
ACSPO AVHRR Sea Surface Temperature	MiRS AMSU-A/MHS Total Precipitable Water	MiRS AMSU-A/MHS Rain Rate

Today’s activity follows NOAA-18’s decommissioning on June 6th. NOAA-15, the last operating spacecraft in the POES series, is slated to be turned off during the week of August 18th.

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10-minute Full Disk scan GOES-19 (GOES-East) Nighttime Microphyscics RGB images from the CSPP GeoSphere site (above) showed a signature of the Ariane-62 rocket condensation cloud (darker shades of blue) following the launch of EUMETSAT Metop-SGA1 from Europe’s Spaceport (Guyana Space Center) at Kourou, French Guyana about 3 hours after sunset on 12 August 2025 (the launch time was 0037 UTC on 13 August). The ascending rocket booster condensation cloud was initially apparent in the 0040 UTC image, followed by the lower-altitude condensation cloud originating from near the launch site (which spread out along and near the coast).

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1-minute Mesoscale Domain Sector GOES-19 (GOES-East) Infrared images (above) showed thunderstorms that produced very heavy rainfall — with 4 sites reporting over 11 inches across parts of the Milwaukee metro area (text list | radar-estimated rainfall) during the 12-hour period from early in the evening on 09 August into the early morning hours on 10 August 2025. The development of new storms west of the Milwaukee area (after 0300 UTC) then trained eastward across areas affected by previous convection, further enhancing rainfall totals and leading to significant flash flooding. GLM Flash Points revealed that abundant lightning activity was associated with these thunderstorms — and some thunderstorm overshooting tops exhibited infrared brightness temperatures as cold as -77ºC (denoted by shades of white embedded within dark black regions).

At Milwaukee International Airport, the 24-hour rainfall total of 5.74″ (on 09 August) and the 48-hour rainfall total of 6.91″ (from 09-10 August) were both the second-highest on record for that location. 1-hour precipitation amounts at METAR sites across the metro area were as high as 2.02″ at Milwaukee International Airport KMKE at 0600 UTC (below) — most of Milwaukee County was under a Flash Flood Warning at the time. Other notable 1-hour precipitation amounts included 1.68″ at Milwaukee Timmerman Airport KMWC (at 0800 UTC), 0.97″ at KMKE (at 0400 UTC) and 0.93″ at Waukesha County Airport KUES (at 0300 UTC). These rainfall rates were high enough to occasionally reduce the surface visibility to 1 mile or less at KMKE, KMWC and KUES.

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A plot of rawinsonde data from Davenport, Iowa at 0000 UTC on 10 August (above) revealed a Total Precipitable Water value of 1.90″ — which was above the 90th percentile for all 10 August / 0000 UTC soundings at that site (below). The presence of such a moist atmosphere was a key ingredient contributing to the heavy rainfall across southern Wisconsin. Furthermore, according to the rawinsonde data plot, the coldest cloud-top infrared brightness temperatures seen in 1-minute GOES-19 imagery (-77ºC) represented a significant overshoot of the Most Unstable (MU) air parcel’s Equilibrium Level (EL).

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In addition to the aforementioned heavy rainfall, during the afternoon hours on 09 August (around 2100 UTC, or 4 PM local time) two hikers were injured by a lightning strike near the Ice Age Trail in Palmyra, with one requiring hospitalization (media report). GOES-19 Visible and Infrared images that included contours of LightningCast Probability (below) indicated that lightning probabilities rapidly increased across that general area, reaching 90-100% over Palmyra about an hour before the lightning strike incident. There were also distinct clusters of GLM Flash Points in the vicinity of Palmyra around and shortly after 2100 UTC.

A time series of GOES-19 LightningCast Probability and GOES-19 GLM-detected lightning at and within 5-10 miles of the closest airport to Palmyra (Waukesha County Airport KUES) also displayed the rapid increase in LightningCast Probability, which began around 1930 UTC (below).

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Elevated smoke levels have been present in the upper Midwestern United States for well over a week, but recent synoptic-scale pattern shifts have started to bring in clearer (albeit warmer and more humid) air from the south. The following animation shows GOES-19-observed aerosol optical depth (AOD) for 1400 UTC (9:00 AM local time) for each day between 25 July and 8 August 2025. Even as far back as the beginning of this loop, Wisconsin, Michigan, and the western Great Lakes are shown to have very high levels of smoke.

The smoke has not disappeared from the midlatitudes of the northern hemisphere; it has simply propagated out to sea. The same aerosol optical depth product (this time viewing a larger portion of the GOES-19 disk) shows that very high levels of aerosol remain. While the air over the midwestern United States is in better shape, the same cannot be said for the northeastern United States and the maritime provinces of Canada. (Note: the high AOD in the lower right hand corner, behind the SSEC logo, is Saharan dust that has blown off into the Atlantic.)

The poor air quality observed by satellite can be verified by looking at a contemporaneous map of in situ air quality observations. The following image depicts PM2.5 s observed by the global network of in situ PurpleAir sensors. While not a governmental network, PurpleAir has the advantage of transcending national borders. There is clearly a strong relationship between the satellite-identified regions of high AOD and surface-based data.

This change in air quality was largely driven by shifts in the synoptic scale flow. Consider the two 500 mb charts displayed side by side. The one on the left is from 1200 UTC on 2 August 2025 while the right is from the same time but on 8 August 2025. For the earlier map, when air quality was at its worst for the Midwest, a high amplitude ridge was present over the western United States and the prairies of Canada. Temperatures were cool and dew points were lower than typical for early August, but the air was originating from the Canadian wildfires and advecting smoke into the central United States. Contrast that with the later map. A ridge is now present over the upper midwest, bring with it heat and humidity, but also air from smoke-free regions.

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