For a solar eclipse to occur, the moon must be in between the Earth and the Sun. This occurs when the Moon is new — that is, when the side of the moon facing the Earth receives no solar illumination. The Day Night Band on Suomi-NPP, or NOAA-21, or NOAA-20 (NOAA-20 is shown above), is therefore only detecting light Cities/Towns, from Gas Flares (as in the arc of light over parts of south Texas, or over the Gulf of Mexico), from Aurora (not in this picture), from fires (none burning in this imagery) or from reflected Earth Air Glow. What information in the Day Night Band tells you where clouds are in such as case? Clouds are faintly visible over the western Gulf of Mexico because of reflected Air Glow. Note also how the city lights over western Louisiana and over northern Mississippi (for example), are slightly blurred. This occurs when visible light energy from city lights is scattered as it moves upward through clouds.

The VIIRS instrument also includes infrared detectors that can better articulate (compared to the Day Night Band image above) where clouds occur. A line of convection (with cold cloud tops) over eastern Arkansas/northern Mississippi is responsible for the attenuation of the visible light there. Cirrus and mid-level clouds are present over western Louisiana. Note in the toggle below the lack of apparent surface features in both the 11.45 µm and 3.74 µm infrared imagery over southeast Texas — compared to the presence of warmer features (likely lakes) over northern Texas. (Click here for an annotated 11.45 µm image).

The 3.74 µm brightness temperature in that uniform region is cooler than the 11.45 µm brightness temperature. This is consistent with the presence of low stratus in that location, and IFR Probability fields at that time agree with the likelihood of low stratus.

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For a period of about 45 days on either side of the Spring (Vernal) and Fall (Autumnal) Equinox (NOAA OSPO Bulletin), each GOES briefly passes through the Moon’s shadow (requiring it to operate on battery power). Near the times of the satellite “local midnight” — around 0900 UTC for GOES-18 and 0500 UTC for GOES-16 — stray light can enter the ABI instrument, potentially causing damage. Portions of the Earth likely affected by this stray light are not scanned, leading to areas of missing data (referred to as Stray Light Zones or Keep-Out Zones).

Daily GOES-18 (GOES-West) Water Vapor images during  the 19 February to 07 April 2024 period are shown near the beginning (above) and end (below) of the Eclipse period — displaying the maximum coverage of missing data on each of those days.

Daily GOES-16 (GOES-East) Water Vapor images for that same 19 February to 07 April period are shown below, near the end of that satellite’s Eclipse period.

It should be noted that the size of the Stray Light Zone varies for each of the Infrared spectral bands, as shown below.

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5-minute CONUS Sector GOES-16 (GOES-East) Mid-level Water Vapor (6.9 µm) and Upper-level Water Vapor (6.2 µm) images (above) revealed that the outline of a portion of Florida’s east coast (specifically along the Gold Coast and the Emerald Coast) could briefly be seen during the day on 05 April 2024. 1901 UTC Water Vapor images with/without a map overlay are shown below. The outline of Florida has been evident in Water Vapor imagery in the past, but usually during the much colder and drier winter months (for example, February 2019).

Along the west coast of Florida that morning at Tampa Bay, 1200 UTC rawinsonde data (above) depicted a Total Precipitable Water value of 0.44 in; while that TPW value was unusually low for Tampa Bay, their sounding climatology (below) indicated it was greater than the record low 12 UTC / 05 April value of 0.20 in. It is that dry air that then moved eastward across Florida during the day.

Plots of Weighting Functions for GOES-16 Mid-level Water Vapor and Upper-level Water Vapor (below) showed the dry middle/upper-tropospheric air’s effect on the height of the peak contribution for those two spectral bands that morning at Tempa Bay — lowering their peaks to 661 hPa and 535 hPa, respectively — with some radiation being sensed from as low as the 750-850 hPa layer (low enough to detect some of the upwelling radiation emitted by the land/water thermal gradient along Florida’s east coast).

For reference, the GOES-16 Upper-level Water Vapor (Band 08) and Mid-Level Water Vapor (Band 09) Weighting Functions (calculated using a US Standard Atmosphere temperature/moisture profile, at a satellite Zenith Angle of 35º) typically peak at 344 hPa and 442 hPa, respectively (below).

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A series of Advanced Scatterometer (ASCAT) images (ascending passes) from Metop-B, above, show a large region of gale force winds surrounding the Hawai’ian Islands between 3 April and 5 April 2024. The entire island chain is under Wind Advisories or Gale Warnings; additionally, High Surf Advisories are in effect on the eastern sides of most islands as shown in the screen capture of the website of the Honolulu NWS Forecast Office below. Small Craft Advisories are also widespread around the islands.

The strong winds are Equatorward of an unusually strong Anticyclone (> 1050 mb!) that has been moving through the north-central Pacific Ocean as depicted in the GFS model output shown below (taken from this website).

Synthetic Aperture Radar (SAR) winds (source), below, also show gale-force winds in/around Hawai’ian islands, but the islands are blocking winds such that relatively calm regions extend for some distance downwind of the islands. (The lighter winds in the lee of the islands show up in the scatterometry fields shown above as well, most especially in the imagery from 4 April).

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What do the waves look like? Altimetry data, below, shows slowly building Significant Wave Heights (defined as the average of the highest 1/3rd of the wave heights) between 3 and 5 April 2024. (Imagery from here)

Observed waves (from this website) north of Maui, below, and east of Kaneohe Bay, Oahu (bottom) also show building wave heights from 3-5 April.

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