A recent question from the Weather Service Office in Pago Pago, Amercian Samoa, brought up the issue of parallax. GOES-18 is located at a longitude of 137 degrees west, while American Samoa is at 170 degrees west. This means there’s around 33 degrees of longitude between the two. By comparison, this is similar to viewing Billings, Montana, from GOES-19 (East) or Denver, Colorado from GOES-18 (West). This results in a significant amount of parallax. This CIMSS Satellite Blog post from 2006 (twenty years ago!) gives a great overview of parallax and its issues. However, we’ll briefly summarize parallax here: the farther away from nadir the satellite is viewing, the more oblique the scan angle. For deep clouds, this means the satellite is more likely to see the side of a cloud rather than the top as the cloud gets closer to the edge of the satellite’s field of view. This also means that the position of the cloud will be incorrectly placed. Check out the following cartoon:

The red house is in the cloud’s shadow, while the blue house is in clear sky. However, because the satellite is viewing the cloud at an angle, the position of the cloud is mapped to a different location than where it actually is. From the satellite’s point of view, the red house is actually in clear sky while the blue house is beneath the cloud. Imagine the surprise of the Blue House citizens when they’re told that it’s cloudy overhead!

American Samoa is far enough west that it is within the field of view of Japan’s Himawari-9 geostationary satellite, too. That satellite is located at a longitude of 141 degrees east, putting it about 49 degrees of longitude away from American Samoa (similar to viewing Seattle from GOES East). Given the deep convection that is frequently found in the tropical Pacific, it’s interesting to compare the two perspectives. The following image pair shows American Samoa, the independent nation of Samoa, and the tropical Pacific at the same time using the True Color RGB from both Himawari-9 (left) and GOES-18 (right). You can drag the slider left and right to see how the change in satellite changes the apparent positions of the clouds.

There are a couple of interesting things to note in this set of images. One of the most glaring (literally!) changes is the difference in sun glint. This occurs when the solar angle over a particular location in the ocean is the same as the satellite viewing angle of that location. The ocean acts as a mirror and reflects the sun’s light into the satellite’s imager. The geometry is just right that GOES-18 detects a significant amount of sun glint at this time. However, because Himawari-9 is in a different position, it doesn’t detect any glint even though it’s imaging the same location at the same time. The angles just don’t work to produce the same result.

The other interesting thing to note is the different impacts of parallax depending on cloud height. Low clouds, like the developing cumulus in the lower right of the images, are largely unaffected by parallax since they’re so close to the ground. High clouds, by contrast, see significant displacement between the two satellite views. This is easily seen in the animation below, in which the small cumulus clouds in the upper right show much less of a spatial change than the upper level cirrus streaks seen elsewhere in the image.

Of course, these location differences are also seen in the infrared imagery as well. In fact, the differences can appear to be even larger in the infrared than in the visible. This is because clouds tend to be white whether you’re seeing their tops or their sides and so it can be difficult to discern what part of the cloud a satellite is seeing.. However, because the temperature of deep convection changes dramatically from bottom to top, the IR signatures will look quite different from the two perspectives, as you can see with the slider below. Again, these are images from the same time and location, just differing from the angle at which they were taken.

The next effect of parallax is to make clouds appear farther from the sub-satellite point than they actually are. This effect is negligible for shallow clouds or for locations that are near the sub-satellite point. But for locations that are on the edge of a satellite’s field of view, like in higher-latitude regions or those, like American Samoa, which are tropical but far away from the sub-satellite point, deep convection can experience significant parallax.

2 blog posts that mention the effect of GOES-18 parallax for deep convection (that produced heavy rainfall) over American Samoa are here and here.

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As a strong arctic cold front moved southward across the Gulf of Mexico toward southern Mexico on 04-05 February 2026, the cold front fractured as it moved inland across Mexico’s Isthmus of Tehuantepec — the cold air was then channeled southward through Chivela Pass and emerged as a Tehuano (or “Tehuantepecer“) gap wind that eventually fanned outward across the Gulf of Tehuantepec and adjacent Pacific Ocean. 10-minute Full Disk scan GOES-19 (GOES-East) Near-Infrared images (above) showed the hazy plume of dust that was being transported offshore — along with a narrow arc cloud that marked the edges of this Tehuano flow.

The pulse of Tehuano winds emerging southward across the Gulf of Tehuantepec and the Pacific Ocean was seen in ASCAT winds from Metop-B and Metop-C (below).

The highest Metop-B wind speed was 40 kts (below).

At the leading (southern) edge of the Tehuano flow, a ship reported NE winds gusting to 35 kts at 1800 UTC (below).

The broad plume of dust lofted by Tehuano winds was apparent in True Color RGB images from both GOES-18 and GOES-19 (below).

Just south of the Pacific coast of Mexico, wind-driven significant wave height values derived from SWOT were as high as 9.55 ft at 2321 UTC (below).

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GOES-19 (GOES-East) SUVI images from the SSEC Geostationary Satellite Imagery site (above) displayed a brief but strong solar flare that occurred on 04 February 2026.

A bulletin issued by the Space Weather Prediction Center (below) classified the X-class flare’s intensity as X4.2.

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A deepening circulation north of Palau in the western Pacific is projected to intensify into a tropical storm between 3 and 4 February 2026. This system is currently (as of 1600 UTC on 3 Feb 2026) labeled as Invest 94W, but analysis from the Joint Typhoon Warning Center projects intensification into a tropical cyclone. A closer look at satellite products can help inform the discussion of what will happen next. Infrared satellite imagery from Himawari-9’s Advanced Himawai Imager reveals a largely asymmetric circulation between Palau and the Micronesian island of Yap.

It can be hard to identify the center of circulation given upper level divergent flow is at times obscuring the lower level flow. Scatterometry can help clear up the confusion by providing a more easily-discernible view of the ocean surface-level winds. Unfortunately, the center of circulation has slipped through the gaps of the most recent ASCAT overpasses, so the broader but noisier OSCAT-3 winds have to be used instead. Winds appear to be on the order of 30-40 kts at the heart of the circulation.

Of course, warm sea surface temperatures are an important factor in tropical cyclone development. The NOAA Geo-Polar blended SST product is a valuable resource for this. Here, the area surrounding the invest has been circled to aid in location. SSTs are between 28-32 C (82 -90 F) so a substantial amount of latent heat is available for the developing system to access.

Larges amounts of water vapor are present in the atmosphere as well, as seen in the CIMSS MIMIC-TPW2 product. The invest is found between 130 and40 degrees E at 10 degrees N. These satellite-derived total precipitable water values are approaching 70 mm.

The CIMSS Environmental Steering product calculates mean winds over various layers through analysis of satellite-observed motion. For an as-yet weaker system like Invest 94W, the 700-850 hPa mean layer can provide useful insight (stronger cyclones use deeper layers). Here, the steering flow suggests that the system will propagate westward toward the Philippines as time progresses.

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