Target Sector (2.5-minute interval) JMA Himawari-9 AHI Clean Infrared Window (10.4 µm) images (above) showed Typhoon Koinu after it reached Category 4 intensity at 0600 UTC (SATCON) on 04 October 2023. The coldest cloud-top infrared brightness temperatures (-80 to -89C, shades of violet to purple) were generally confined to the southern semicircle of the storm. A faster animation (GIF | MP4) revealed a bit of trochoidal motion (wobble) to Koinu’s eye.

Even though Koinu was traversing an area of warmer water (Sea Surface Temperature | Ocean Heat Content), it was moving through an environment of increasing deep-layer wind shear (source). The general satellite presentation began to deteriorate — with the eye becoming more cloud-filled — as it approached the far southern tip of Taiwan, making landfall around 2332 UTC.

Microwave (85 GHz) images from DMSP and GMI satellites (below) provided 3 views of the evolving eyewall structure at 0934 UTC, 1651 UTC and 2032 UTC.

A toggle between daytime (0450 UTC) and nighttime (1719 UTC) Suomi-NPP VIIRS Day/Night Band (0.7 µm) images (below) also showed that Koinu’s eye became more cloud-filled during that 12-hour period.

It is worth noting that the eye of Koinu passed directly over Orchid Island around 1334 UTC — where an unconfirmed wind gust of 213 mph (95.2 m/s) was measured at the Lanyu Weather Station within the rear eyewall at 1351 UTC.

Statistics released by CWA confirmed that Lanyu observed a gust of 95.2m/s in the last hour, and the data was missing after the 10-minute sustained wind speed rose to 47.6m/s. The current MSLP at Lanyu has dropped to 939hpa, which also broke the historical record? pic.twitter.com/N7eccj3YP5

— Jim yang (@yangyubin1998) October 4, 2023

Unofficially, this 213 mph wind gust is the 3rd highest highest wind gust ever measured on Earth. https://t.co/WgbqoxmB1W

— Colin McCarthy (@US_Stormwatch) October 4, 2023

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The North Texas panhandle is experiencing severe weather on October 4, 2023. Animation 1 shows Radar reflectivity in tight areas of convection across the panhandle. The GOES Day Cloud Phase Distinction RGB shown in Animation 2 confirms convection, showing overshooting tops becoming wispy ice clouds (appearing orange in the RGB).

An enhanced risk of convection was predicted by the Storm Prediction Center for this exact area. More precise forecasts of weather severity can be assessed using the ProbSevere product. ProbSevere uses a combination of satellite data, ground-based data, and numerical weather models. It can be thought of as a probability of severe weather. Note how ProbSevere follows areas of high reflectivity.

Part of ProbSevere includes ProbHail, which signifies the probability of hail. The figure above overlays ProbHail with Radar Reflectivity. Focus on the bright region to the far right, near the border of Hardeman and Jackson counties. This area has a hail probability equal to 77% and corresponds with reflectivity values near 64 dBZ. With reflectivity values that high, hail is a definite likelihood.

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 associated with the severe thunderstorms that moved eastward across parts of Oklahoma and Texas on 04 October 2023.

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Mostly clear skies over the western Atlantic on 4 October 2023 meant that the Advanced Clear Sky Processor for Oceans (ACSPO) algorithm could produce a near-complete picture of sea-surface temperatures using data from NOAA-20’s VIIRS instrument. The sinuous Gulf Stream is marked as a region of warmest waters, around 85^oF off the coast of South Carolina (pink in the enhancement used); once past 70^oW Longitude, warmest surface waters in the Gulf Stream are closer to 80^oF (orange in the enhancement).

There is a GOES-16 Level 2 Sea Surface Temperature product as well, computed hourly; it is shown in the animation below that brackets the VIIRS SSTs shown above (and here).

The toggle below compares the higher-spatial-resolution VIIRS SST field with the GOES Level 2 Product.

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GOES-18 (GOES-West) SO2 RGB and Ash RGB images (above) showed the complex transport of a volcanic cloud produced by an explosive eruption of Mount Shishaldin that began around 1350 UTC on 03 October 2023. The bulk of the higher-altitude volcanic cloud was rich in SO2 (shades of yellow in both RGB types), while a smaller mid-level portion that had high ash content exhibited shades of reddish-brown in the Ash RGB (and shades of blue to pink in the SO2 RGB images).

2 Pilot Reports (PIREPs) issued shortly after the eruption onset indicated an ash height of 21000 ft at 1400 UTC, and 40000 ft at 1446 UTC (below).

In Nighttime Microphysics RGB  + daytime True Color RGB images from the CSPPGeoSphere site (below), after sunrise the ash-rich portion of the volcanic cloud exhibited shades of tan to darker brown, as it moved to the south-southwest.

A radiometrically retrieved Volcanic Ash Cloud Height product from the NOAA/CIMSS Volcanic Cloud Monitoring site (below) indicated that parts of the volcanic cloud may have reached heights in the 18-20 km range (black enhancement) within 20 minutes of the eruption onset.

About 14 minutes after the explosive eruption began, a toggle between Suomi-NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images valid at 1404 UTC (above) revealed that the coldest cloud-top infrared brightness temperature was -64.37ºC (cyan color enhancement) — while the hot lava flows spreading away from the summit of Shishaldin exhibited surface infrared brightness temperatures as high as 106.85ºC (darker black enhancement).

The -64.37ºC cloud-top infrared brightness temperature was indicative of a significant air parcel overshoot of the local tropopause — which was -50.5ºC at an altitude of 9292.4 m (30486.9 ft) according to 1200 UTC rawinsonde data from nearby Cold Bay, Alaska (below).

On a side note, a toggle between Infrared Window images from Suomi-NPP and GOES-18 (below) showed (1) the large northwest parallax offset associated with GOES-18 imagery at such high latitudes, which would be about 35 km or 22 mi for a 50 kft cloud top feature in the vicinity of Shishaldin, and (2) the significantly colder cloud-top infrared brightness temperature sensed with the higher spatial resolution VIIRS instrument (375 m, vs the nominal 2 km at satellite sub-point for GOES-18 ABI).

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