2.5-minute Target Sector JMA Himawari-9 AHI Infrared images (above) showed Cyclone Narelle as it was rapidly intensifying over the Coral Sea on 18 March 2026 — becoming a Category 2 storm by 1200 UTC, a Category 3 storm by 1800 UTC and a Category 4 storm by 0000 UTC (ADT | SATCON). The coldest cloud-top infrared brightness temperatures were in the -90 to -95C range.

Himawari-9 Infrared / Water Vapor Difference images (below) exhibited large difference values — highlighting cloud tops that were significantly overshooting the tropopause.

Himawari-9 Infrared images with an overlay of Deep-Layer Wind Shear (below) indicated that Narelle was moving through an environment of modest shear — which, along with warm Sea Surface Temperatures favored further intensification.

Comparing DMSP SSMIS Microwave images at 0622 UTC (above) and 2004 UTC (below), the eyewall had become more consolidated and the eye diameter contracted a bit during that time period (signatures of an intensifying tropical cyclone).

===== 19 March Update =====

A Radar Constellation Mission (RCM-1) Synthetic Aperture Radar (SAR) wind speed image at 0847 UTC on 19 March (above) depicted a maximum of 130 kts in the SW quadrant of Narelle.

A nocturnal NOAA-21 (mislabeled by AWIPS as NPP) VIIRS Day/Night Band image (above) revealed concentric mesospheric airglow waves (reference) propagating outward from Category 4 Cyclone Narelle as the storm was just east of Australia’s York Peninsula.

2.5-minute Himawari-9 Infrared images (above) suggest that Category 4 Cyclone Narelle made landfall along Australia’s York Peninsula just after 2100 UTC on 19 March. During the hours preceding landfall, pulses of overshooting tops exhibited infrared brightness temperatures of -90C and colder (yellow pixels embedded within darker purple regions).

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Just north of Libya on the afternoon of 17 March 2026, a large cyclone can be seen forcing a significant amount of dust from the Sahara to the Mediterranean. This true-color view from EUMETSAT’s Meteosat Third Generation (MTG) Flexible Combined Imager (FCI) depicts this situation beautifully. Since MTG-FCI has three visible channels, it is able to produce true color products with fewer assumptions than the GOES-R series of satellites has to rely upon in order to produce similar-looking imagery. This image is from 1230 UTC and is provided courtesy of EUMETSAT’s Eumetview.

Of particular interest is the large dust band that has been pulled from Libya and Egypt into the air over the sea. The Dust RGB can be used to denote where dust is prevalent. The following image is for the same time. Areas in magenta are associated with dust, and it’s obvious how widespread the dust is.

An interesting question is: what kind of storm is this, exactly? A medicane (a portmanteau of “Mediterranean” and “Hurricane”) is a certain type of cyclone that exhibits some characteristics of a tropical storm, including a warm core and an eye, that separates it from a more traditional mid-latitude cyclone. These are able to use the relatively warm waters of the Mediterranean to develop like a traditional tropical system would, but generally at a much lower intensity. It is March, of course, so the sea surface temperatures are still cool. The 15-16 C temperatures are on the low end of what has been observed with medicanes, but is still possible as much of the dynamical driving is done by upper-level cold air. The ASCAT Winds show a maximum wind speed approaching 40 knots, though it is not clear if the center of the storm is truly calm or if there’s just an observational gap there.

Looking at the animation, there is definitely an eye-like structure at the center of the storm, which is not seen in a standard midlatitude cyclone due to the low-level convergence of those systems.

The 700 hPa temperature field from the ECMWF model from 1200 UTC on the 17th also seems to indicate a hint of a warm core to the system, as can be seen in the bottom center of the graphic below.

Together, these factors have caused some European meteorological centers to officially label this a Medicane. Depending on which agency you listen to, it’s either called Samuel (France, Andorra) or Jolina (Italy).

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5-minute CONUS Sector GOES-19 (GOES-East) Visible images with an overlay of GLM Flash Extent Density (above) showed the signature of a high-altitude bolide that was moving from southwestern Lake Erie toward far northern Ohio during the 5-minute period ending at 1301 UTC on 17 March 2026. This bolide created a sonic boom that was heard in several communities.

GLM gridded products such as Flash Extent Density are plotted to correspond to a mean cloud top height — which is about 10 km over CONUS. Non-gridded GLM parameters such as Groups (below) include a parallax correction that maps them to the surface — which if removed, shifts the Group locations to the north so that they more closely correspond to the location of the Flash Extent Density signature.

A map of fireball reports from the American Meteor Society site (below) displayed the large area from which this event was seen. A closer view indicated that the bolide likely traveled along a north-to-south trajectory. More details on the asteroid that caused the fireball is available here.

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5-minute GOES-19 (GOES-East) Visible, Near-Infrared “Cirrus”, Mid-level Water Vapor and Clean Infrared Window images (above) displayed a set of curved contrails that formed south-southeast of Dallas/Fort Worth — created by 2 passenger aircraft in holding patterns, before eventually landing at Houston’s George Bush Intercontinental Airport (KIAH) — which then drifted southeast toward the Texas coast on the morning of 16 March 2026.

The curved contrails were also seen in GOES-19 True Color RGB images from the CSPP GeoSphere site (below).

Flight track maps from FlightAware showed the holding pattern ovals taken by 2 United Airlines flights (at altitudes of 32000-33000 ft) northwest of KIAH (below).

A plot of rawinsonde data from Fort Worth at 1200 UTC (below) showed a moist layer from 294-217 hPa (30000-36000 ft), where these contrails likely developed and persisted.

Other examples of circular contrails have been previously documented on this blog.

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