The Samoan Islands are again within a moisture-rich airmass, as shown by the MIMIC estimates of Total Precipitable Water shown below. The MIMIC fields do not show obvious gradient that might be used to estimate when rains might be especially widespead. The airport at Pago Pago American Samoa has had a little under 2″ of rain the 24 hours ending at around 9 AM Samoa Standard Time on 9 April. Flood Warnings were posted overnight on the 8th (in part because of scenes like this image from the NWS Pago Pago Slack Channel!)

Infrared imagery, below (source), from 0250 UTC to 1840 UTC (that is, 350 PM to 750 AM American Samoa Time), shows extensive overnight convection that moves from south of American Samoa northward. By the end of the animation, the focus of convection is north of the Samoan Islands with a strengthening line of westward-moving convection is also moving along 5^oS latitude. Convection over the Samoan Islands weakens as the westward-propagating line strengthens.

Water Vapor imagery for the same interval, below, also shows a diminishing trend for convection over the Samoan Islands.

LightningCast probabilities over Amercan Samoa, below (from this site) show a big difference between 0630 and 1930 UTC on 9 April 2024. Lightning probabilities were high and lightning was active at 0630 UTC. By 1930 UTC, activity was much reduced, with elevated LightningCast probabilities confined to regions south of American Samoa. This might be a region to watch for development.

GFS estimates of the Galvez-Davison Index (GDI), below (source) from the 1200 UTC GFS run show large values (>45) of GDI persisting over and south of the Samoan Islands until about 0000 UTC on 11 April. The potential for heavy rain continues over American Samoa for another day despite the respite shown in the ABI data above. (Note from this blog author: I find forecasting for American Samoa very very difficult!) (Here is blog post comparing GDI to DSI estimates of K-Index). The 2100 UTC LightningCast probabilities (here), do show an increase in probabilities of a GLM observation (and actual GLM observations) just to the south of Tutuila, so perhaps convection is starting to become more widespread.

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Contributors: Scott Bachmeier, Mat Gunshor, Rick Kohrs, Margaret Mooney, Jim Nelson, Tim Schmit, and Eric Verbeten.

Another CIMSS Satellite Blog on the Eclipse, when time compositing imagery from 2024 (and 2017).

A similar loop as above, but with a special enhancement (contrast stretch) is in this CIMSS Satellite Blog post (which also includes a comparison of the 2017 and 2024 eclipse events).

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The eclipse starts in the GOES-West footprint, as shown above (Here’s a link to a Full-Disk GOES-West animation). By 1700 UTC, however, GOES-East starts to view it, as shown below (Here’s a link to a Full-Disk GOES-East animation).

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Here are CIMSS Natural Color animations from GOES-West and GOES-East Full Disk showing the eclipse shadow.

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To examine the effects of the eclipse shadow on surface weather, let’s turn to GOES-16 Near-Infrared “Vegetation” images (below), centered over North Texas. Many sites recorded drops in surface air temperature of 4-5 degrees F as the shadow traversed the area — for example, see these plots of surface report data across North Texas at Brownwood, Fort Worth, DFW Airport and Paris.

The corresponding hourly GOES-16 Land Surface Temperature (LST) derived product (below) displayed cooling LSTs as the shadow’s arrival halted the trend of midday heating.

The eclipse shadow and its effect on surface cooling was also evident in imagery from polar-orbiting satellites. 3 consecutive overpasses of NOAA-20 and Suomi-NPP provided VIIRS False Color RGB and Shortwave Infrared images centered over northwest Arkansas (below) — which showed a notable cooling of surface infrared brightness temperatures across the Mississippi Alluvial Plain as the shadow moved across the region. In addition, a number of METAR sites reported surface air temperature drops of 5-6 degrees F as incoming solar radiation decreased.

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More imagery of the 2024 Eclipse is available at the Satellite Liaison Blog.

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Early on 8 April (CSPP Geosphere link also shown below), there are some obvious winners and losers as far as Eclipse-viewing goes, as shown with GOES imagery. If you’re in western New York State, for example, things look unfortunate. Texas? Hit or miss: plenty of clouds, but not completely overcast. Maine? That looks pretty good to this blogger! We’ll see how things evolve during the day however. Here in Madison WI, skies look like a view of a 90%-eclipsed sun is likely. Check out the CSPP Geosphere site for the latest imagery.

Real-time animations of the Eclipse will be available at the website shown above, https://www.ssec.wisc.edu/datacenter/eclipse2024/ . Animations will include ABI and SUVI data.

Just seven years after a total eclipse swept northwest to southeast across the Contiguous United States (as discussed in blog posts here and here), a total solar eclipse will move southwest to northeast from Mexico to the eastern Great Lakes to New England on 8 April 2024. During and after the event, we will post an animation (above) with combined views from GOES-18 and GOES-16 showing the satellite view of the Moon’s shadow. There will also possibly be mesoscale sectors covering the path of the eclipse (link).

The paths of the 2017 eclipse and the 2024 eclipse are shown below. (Shout out to those Americans who had the foresight to live in the intersecting paths of totality near Carbondale IL as shown in the figure below the two globes, from this handy website). See composite eclipse shadow images from the 2017 and 2024 events at this blog post.

The animation below (from Rick Kohrs, SSEC/CIMSS), shows the region of the shadow as it moves across North American and adjacent waters, from sunrise over the Equatorial Pacific to sunset over the north Atlantic. (The same animation with a stationary map is here).

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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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