The National Weather Service forecast office on Guam (at 13.4^oN, 144.7^oW) is paired with an L/X band satellite receiver that can download data from Polar Orbiting satellites, which data can subsequently be processed by Polar2Grid software to produce useful products. The animation above shows 4 different Himawari-9 Band 13 images on 21 September, a day when Guam was experiencing intermittent rains as a feature moved northward. When do you think the rain was heaviest? Did you choose 1130 UTC? That is what the microwave-derived rainrate suggests (see below). A side-by-side comparison of the Himawari Band 13 imagery and Microwave-derived rain rate is here. A meteorogram for Guam International airport is here: Heaviest observed rains were around 1200 UTC; rains ended around 1500 UTC. That is in agreement with the microwave diagnoses.

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What was the environment around Guam? Microwave estimates of Total Precipitable Water, below, (source), show Guam near the northern edge of a moisture-rich band of tropical origins. Advanced Scatterometer winds, at bottom, from MetopB and MetopC (times as noted in the caption), show a convergence line nearing Guam on 20 September (on 21 September, ASCAT did not sample over Guam).

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Thanks to Douglas Schumacher, CIMSS, for supplying the imagery from the Guam Direct Broadcast antenna!

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CSPP Geosphere, often featured on this blog, is a website which allows users to view near-real-time imagery of GOES-East and GOES-West ABI data. All sixteen spectral bands on the ABI are available to view, along with RGB imagery. Full disk products are available, along with Continental United States (CONUS) and the two mesoscale sectors. Every ten-minute Full disk frame of data is included on CSPP Geosphere. The data is archived back approximately two weeks, allowing users to look at past events. The interface of the CSPP site allows the user to select specific time frames they are interested in viewing. CSPP allows users to save animations with 144 or fewer frames, making the frame selection tool very useful.

To create an animation like the one below, the user can select a frame every third hour, going back seven days. This creates a weekly animation, showing frames every three hours (0000Z, 0300Z, 0600Z, 0900Z, etc.) for each day.

The video shows a fairly active week for cyclones in the Atlantic. Hurricane Lee made landfall on 2023-09-16 as a post-tropical cyclone on the western coast of Nova Scotia. There is also Hurricane Margot, which has veered to the east to the mid-Atlantic, far away from any coastline.

On 2023-09-17, the structure which will become Hurricane Nigel becomes quite apparent. It is designated a hurricane on 2023-09-18 at 0900Z. By 2023-09-19 at 0300Z, the rotational structure is clear and an eye is apparent. On 2023-09-20 around 1200Z, Nigel’s path begins to move eastward. It is forecast to devolve into an extratropical cyclone and currently poses no threat to human populations.

The full disk animation from CSPP Geosphere allows users to view many interesting weather phenomena over the Atlantic Ocean. Along with the lifecycles of hurricanes, one can see large amounts of dust blowing off of the Sahara Desert in West Africa. At the mouth of the Amazon River, there is visible river sediment outflow from the Amazon’s delta and estuary.

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GOES-West imagery, above, from the CSPP Geosphere site, shows Hawaii in a tradewind regime (direct link to animation). The animation, from 0121 to 0556 UTC on 21 September 2023, shows the steady progression of cloud lines moving east-to-west, with embedded regions of apparent showers that generate outflow boundaries. At 0431 UTC, Sentinel-1A overflew the eastern Hawai’ian islands, and a high-resolution picture of the surface winds resulted (Data are available online as well: Normalized Radar Cross Section Data, and Winds). The three wind footprints are stitched together below.

Strong winds — nearly 30 knots — are associated with a modest looking (and decaying) convective cell just to the east of Maui. None of the convection in this scene reaches particularly high into the atmosphere; cloud top brightness temperatures are in the 5-10^o C range. The Hilo Sounding at 0000 UTC on 21 September 2023 shows a tradewind inversion top at 750 hPa, suggesting the clouds reached to about that level. (The strong winds of the Alenuihaha channel are also shown!) Note also the strong winds in the lee of the Big Island of Hawai’i.

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Sentinel orbits are such that exact repeats occur every 12 days. The Ocean Virtual Laboratory allows a user to track the overpasses.

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1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) included time-matched (+/- 3 minutes) plots of SPC Storm Reports — which showed severe thunderstorms that moved eastward and southeastward across parts of Kansas, Oklahoma and Texas on 19 September 2023.

1-minute GOES-16 “Clean” Infrared Window (10.3 µm) images (below) indicated that the coldest pulsing overshooting tops associated many of the storms exhibited infrared brightness temperatures in the -60 to -65ºC range (darker shades of red). These thunderstorms produced a tornado in Kansas, hail up to 2.75 inches in diameter in Texas and damaging winds up to 74 mph in Oklahoma.

5-minute CONUS Sector GOES-16 Visible images with overlays of the CAPE, Lifted Index and Total Precipitable Water derived products (below) showed that these storms intensified as they moved into a corridor of instability and moisture. CAPE values were as high as 1400 J/kg, LI values reached -6ºC and TPW values exceeded 1.60 in.

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