12 days after its powerful eruption on 17 April, 10-minute JMA Himawari-9 AHI Infrared Window (10.4 µm) images (above) showed another explosive eruption of Mount Ruang in Indonesia on 29 April 2024. The coldest cloud-top infrared brightness temperatures reached -90C (internal yellow pixels) at 1850 UTC, immediately after the eruption onset. Concentric cloud-top gravity waves were also evident. Volcanic ash was reported at Menado (station identifier WAMM) beginning at 0000 UTC on 30 April, which restricted the surface visibility to 3-4 miles.

The cloud-top gravity waves were more apparent in higher-resolution Himawari-9 Red Visible (0.64 µm) images (below).

A toggle between Himawari-9 Visible and Infrared images at 2150 UTC on 29 April (below) showed that the primary volcanic plume (produced by the strong updraft associated with the explosive eruption) exhibited warmer infrared brightness temperatures — indicating that it had penetrated the local tropopause and extended into the lower stratosphere.

A plot of rawinsonde data from Menado, Indonesia at 0000 UTC on 30 April is shown below.

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1-minute Mesoscale Domain Sector GOES-16 (GOES-East) Visible/Infrared Sandwich RGB images (above) showed thunderstorms that produced tornadoes, large hail and damaging winds (SPC Storm Reports) across eastern Nebraska and western Iowa on 26 April 2024.

1-minute GOES-16 Visible/Infrared Sandwich RGB images with an overlay of GLM Flash Extent Density (below) showed the lightning activity associated with this convection — which included some notable lightning jumps as tornadic thunderstorms moved through the Omaha area (producing the EF3-rated Elkhorn tornado) beginning about 2040 UTC.

A larger-scale view using 1-minute GOES-16 “Clean” Infrared Window (10.3 µm) images (below) also showed the storms that affected western and central Iowa after sunset. The coldest infrared brightness temperatures of thunderstorm overshooting tops were around -60C (darker black enhancement).

Cursor samples displayed a few select Tornado Local Storm Reports across eastern Nebraska and western Iowa from 1955-2305 UTC on 26 April (above) and across western and central Iowa from 0025-0159 UTC on 27 April (below).

A larger-scale view of 1-minute GOES-16 Infrared images that included an overlay of GLM Flash Extent Density is shown below.

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High Pressure over the Great Lakes on 25 April meant a spectacular true-color view of the 5 Great Lakes (apologies to Lake Champlain) by the VIIRS instruments on NOAA-20. A similar view was recorded at 1755 UTC by Suomi-NPP, shown below.

Clear skies also meant a determination of Lake Surface Temperatures, shown below (compare these to Monday, although note the scale here is 32 to 59^oF v. 32 to 50^oF on Monday). Relatively cool waters persist in eastern Lake Erie, Lake Superior is uniformly cold (37 to 38^oF), and a curious warm ring has developed over southern Lake Michigan, 10^oF warmer at its center than the surrounding lake waters!

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AWIPS-ready JPSS Tiles are created from data downloaded at the Direct Broadcast antenna at CIMSS (processed by CSPP software) and are available from an LDM feed at CIMSS. Data are also available as imagery at this ftp site, and here.

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Sometimes, warm water observations occur because of the reflection of solar radiation (although that should be accounted for in ACSPO algorithms as sunglint location can be calculated). In this case you don’t see glint in the True Color, and the I04 imagery (shorwave infrared, at 3.74 µm) doesn’t show spectacular warmth. The GOES-16 Land Surface Temperature does show a warm eddy moving westward across the Lake however, at fairly high speed! That earns this post the “What the heck is this?” tag!

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Has this type of warm-water feature appeared in Lake Michigan before? The answer is yes: such isolated warm water features are often associated with areas of very light winds — usually beneath the center of high pressure at the surface — which allows the relatively calm water surface to warm more rapidly. These areas of light winds will exhibit a darker appearance in Visible imagery — or in this case on 25 April, Near-Infrared imagery (above). The warmest VIIRS Sea Surface Temperature value was 52.73ºF, near the apparent center of the surface high pressure (judging by the model surface wind barbs). Details of 2 similar Lake Michigan events are available in previous blog posts here and here.

Although it was about 6 hours earlier than the NOAA-20 VIIRS images, an overpass of RCM-3 provided Synthetic Aperture Radar (SAR) imagery (source) which displayed lighter wind speeds (darker shades of blue) in southern Lake Michigan (below).

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The animation below shows GOES-16 Hourly Land Surface Temperature fields from 1400 UTC 25 April 2024 through 0200 UTC 26 April 2024. That important central Lake Michigan observation appears to be part of the Great Lakes Observing System (link). A curious aspect of the in situ observations is that they are cooler than the sensed surface temperature as the warm lens of water moves through (up through 1900 UTC), but at 2000 and 2100 UTC, the buoy temperatures are warmer than the satellite-derived product.

Data from the Spotter Buoy are available here. Data include observed significant wave heights and pressure, and Lake Temperatures. The monthly temperature trace is shown below, highlighting the intense character of this feature. (Daily and Weekly traces are also available). Data from Buoy 45214 are also available at the NDBC site: here are plots of water temperature and significant wave height.

Significant wave heights during this time were minimal — generally less than 1 foot. The barometric pressure at the buoy started falling around 1500 UTC. (Direct wind observations at the buoy site are not available).

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An extended dry period over the Marianas Islands was broken (at least temporarily) on 24 April when training thunderstorms dropped more than 5 inches of rain at the Guam airport. The US Drought Monitor data for the Marianas is shown below. Guam and Saipan both show extreme drought. Before the rain on 24 April, Guam year-to-date rains were 50% of normal. Persistent drought over the islands means that the heavy rains that fell likely did not percolate into the soil, instead becoming run-off. The airmass RGB above shows the evolution of the strong storms especially between 1800 and 2230 UTC. (Click here for a slower animation during that time). Visible imagery after sunrise (below) shows the strong thunderstorms as well.

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MetopB overflew Guam shortly after 0000 UTC on 24 April, as shown below. Surface winds at that time show stronger trades approaching from the east. Note that Metop-B viewed this region of the Pacific twice on 24 April, once at 0010 UTC, and once at 2350 UTC as shown in this image of the MetopB orbits on 24 April; (source) the left-most swath and the swath over Guam are from the early overpass; the other two swaths are from the later overpass.

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Himawari-9 data are available in RealEarth. The loop below shows the clean window infrared imagery (Band 13, 10.4 µm) from 1800 to 2200 UTC on 23 April. The coldest cloud tops occurred around 2020/2030 UTC. Cloud-top warming was widespread after 2130 UTC.

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The Direct Broadcast antenna at the forecast office on Guam received data from a variety of polar orbiting satellites, including MetopB/MetopC. Rain rate data derived (using CSPP software) from data on the microwave sounders (AMSU-A/MHS) on board those satellites is shown below. Values are not particularly large by 0000 UTC on the 24th, compared to the values to the south in the ITCZ, for example. It continues to show light rainfall diagonally across Guam however.

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