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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RADARSAT-2 and RCM-3 satellites had nearly simultaneous overpasses over Typhoon Koinu on 3 October 2023, as shown below. (See this blog post from 2 October for more on Koinu) Both SAR analyses showed the strongest winds (nearly 120 knots) in the southern eyewall of the storm, with long interesting wind minima features (close to 65 knots, dark cyan/green in the enhancement, surrounded by stronger winds, exceeding 80 knots, yellow in the enhancement), threading in towards the storm’s eyewall.

How do the SAR Wind fields compare to Himawari-9 infrared imagery? That is shown in two toggles below (0945 UTC was shortly after sunset over the storm, so visible data aren’t used here). The eye is distinct in the SAR imagery, as it was on 2 October. There is some warming in the center of the storm, and cold cloud tops are apparent in the eyewall — especially over the region of strongest SAR-diagnosed winds. An hour-long animation of the Himawari-9 target scene is below the two toggles.

This RCM-3 SAR wind analysis (from this website) uses the same color scale as this example from this blog post. The side-by-side comparison, below, shows that peak winds have increased since 2122 UTC 01 October, and the areal extent of the winds have also broadened.

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Target Sector (2.5-minute interval) JMA Himawari-9 AHI Visible and Infrared images (above) showed Typhoon Koina as it intensfied to a Category 3 storm by 0000 UTC on 02 October 2023 (SATCON). Cloud-top infrared brightness temperatures were as cold as -90C.

Just prior to the start of the Himawari-9 animation, an image of RCM-3 Synthetic Aperture Radar (SAR) winds at 2122 UTC on 01 October (source) is shown below — which depicted a narrow but fully closed eyewall.

Later in the day, Himawari-9 Infrared Window (11.2 µm) images with an overlay of deep-layer wind shear at 2100 UTC — from the CIMSS Tropical Cyclones site (below) indicated that Koinu was moving through an environment where the shear (around 15 knots) was favorable. In addition, Koinu was traversing warm water (Ocean Heat Content | Sea Surface Temperature).

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