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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5-minute CONUS Sector GOES-16 (GOES-East) True Color RGB images from the CSPP GeoSphere site (above) displayed smoke plumes from widespread prescribed burning in the Flint Hills of eastern Kansas and Oklahoma on 04 April 2024. There were also dense smoke plumes originating from another cluster of prescribed burns in the vicinity of the Oklahoma/Arkansas border.

GOES-16 “Red” Visible (0.64 µm) images with an overlay of the Fire Mask derived product (a component of the GOES Fire Detection and Characterization Algorithm FDCA) depicted the areal coverage and diurnal behavior of the fire thermal signatures (below). A similar animation using the GOES-16 Fire Power derived product is available here: GIF | MP4.

Judging from the surface reports, most of the smoke appeared to have been dispersed above the boundary layer (a few locations intermittently reported the base of the smoke layer to be in the 2200-4400 ft range) — but the surface visibility was briefly reduced by smoke to 4-6 miles at sites such as Emporia, Kansas and Claremore, Oklahoma (below).

Previous examples of the annual Flint Hills prescribed burn activity during the Spring season have been documented on this blog in 2022, 2019, 2017,and 2010.

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