Himawari-8 ‘Target Area’ imagery (with a 2.5-minute timestep) on 5 April show the evolution of Cyclone Seroja over the Timor Sea northwest of Australia. (Click here for an mp4 animation). Periodic bursts of deep convection (black and white in the color-enhancement) are apparent in the center of the storm. Analyses from the CIMSS Tropical Weather Site (link) show the storm in a region of warm Sea Surface Temperatures. Modest shear is present and it is changing the convective core of the storm in the animation above from circular to elongated over the 8-hour animation. However, strengthening is forecast.

Visible imagery at sunrise on 6 April shows the evolution of the storm.

Himawari-8 imagery courtesy JMA. You can also view satellite imagery over the area from KMA.

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Update 8 April

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Himawari-8 imagery (10.41 µm), below, from 0300-1610 UTC on 8 April, show a large cirrus canopy initially over Seroja eroding (You can see the 0300 and 1610 UTC images alone toggling here) Can you tell from this infrared imagery where the storm center sits?

This is certainly a case where microwave imagery can (and should!) be used to better pinpoint the circulation center.  ASMU-B imagery at 89 GHz (from here), below, storm-centered at 2307 UTC 7 April, 0207 8 April and 1143 UTC on 8 April show a storm center near 18ºS, 111.5ºE at around 1200 UTC on 8 April.  Here is the Himawari-8 Clean Window infrared at 1140 UTC.  Could you place the center near its microwave-suggested center using this infrared imagery?

Imagery from the CIMSS Tropical Website (link), below, show that Seroja on 8 April was traversing a region of low shear.  Sea surface temperatures at present under the storm are warm; however, the projected path of the storm is towards cooler ocean waters.  There is abundant upper-level divergence over the storm and to the northwest of Seroja as well.

Radarsat-2 Synthetic Aperture Radar (SAR) wind data (from this website), shown below, from 1054 UTC on 8 April, can also be used to infer a circulation center.

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The incipient circulation of Cyclone Seroja moved very slowly across the island of Timor in Indonesia during the 03 April – 04 April 2021 period — and the MIMIC Total Precipitable Water product (above) depicted very high values over that area (just northwest of Australia).

At Kupang’s El Tari Airport, precipitation amounts included 547 mm (21.5 inches) during the 48 hours ending at 00 UTC on 05 April — with the heaviest amounts of 106 mm (4.2 inches) in 6 hours and 80 mm (3.1 inches) in 3 hours occurring during the 00-06 UTC period on 04 April when the pressure was falling as Cyclone Seroja began to slowly organize and intensify (below). Flash flooding affected much of the island, with multiple deaths being reported.

JMA 2.5-minute interval rapid scan Himawari-8 “Clean” Infrared Window (10.4 µm) images (below) revealed a few convective bursts — with cloud-top infrared brightness temperatures of -90ºC and colder (yellow pixels embedded within darker shades of purple) — in the vicinity of Kupang (station identifier WATT) between 04 UTC on 04 April and 00 UTC on 05 April.

A NOAA-20 VIIRS Infrared Window (11.45 µm) image at 0550 UTC visualized using RealEarth (below) showed one lone -90ºC pixel within a convective burst centered just north of Kupang.

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CMORPH estimates of 7-day precipitation (available in RealEarth) over the region show 300-400 mm over West Timor, and values exceeding 700 mm (!!) over the adjacent ocean.

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Every Spring season, many states conduct prescribed burns as a part of land management within forests, parks, wetlands etc — and GOES-16 (GOES-East) True Color RGB images created using Geo2Grid (above) showed a large number of smoke plumes associated with prescribed burning across parts of the central US on 02 April 2021.

Of particular interest was a very long smoke plume that was seen streaming northward across southern Lake Michigan — a closer view using GOES-16 True Color RGB images centered over that area (below) indicated that 2 separate plumes merged into one larger/longer smoke plume that continued to drift north-northeastward toward the west coast of Lower Michigan. The source of these smoke plumes was the combination of a small prescribed burn and a larger wildfire within the Indiana Dunes National Park near the coast of Lake Michigan.

375-meter resolution Suomi NPP VIIRS True Color RGB and Shortwave Infrared (3.74 µm) images (below) provided a more detailed view of the smoke plume over far southern Lake Michigan, as well as thermal anomalies (clusters of hot pixels) associated with the industrial sites producing the smoke.

The pair of 1-minute GOES-16 Mesoscale Domain Sectors was positioned to cover the northern and southern portions of the central US  — and a small overlap of the sectors provided 30-second imagery over the Nebraska/Kansas border area. 30-second GOES-16 Fire Temperature RGB images (below) offered a qualitative view of the locations and relative intensities of a few prescribed burns in the southwestern portion of Nebraska.

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GOES-16 (GOES-East) Shortwave Infrared (3.9 µm) images (above) showed the thermal anomaly (cluster of darker red pixels) associated with a fire at a metal recycling plant in La Crosse, Wisconsin — located at the center of the images — on 02 April 2021. According to media reports, over 100 vehicles were burning at the facility. Farther to the south, a few thermal signatures of prescribed burns were seen in northeastern Iowa.

A brief smoke plume was produced by the recycling center fire, as shown in GOES-16 True Color RGB images (below), which drifted north-northeastward. Smoke plumes from the prescribed burns were also evident.

A time series plot of surface weather conditions at La Crosse Regional Airport (below) showed the strong southerly winds gusting to 27 knots around the time of the fire, which transported the smoke plumes northward.

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