A series of LightningCast Probability plots from this RealEarth-powered website, below, shows increasing probabilities of lightning over the South Pacific to the south of American Samoa’s Manu’a Islands. The 75% contour (magenta) appears at 0530 UTC; the first GLM observation is shown at 0620 UTC. LightningCast is the probability that a GLM observation will occur within the next 60 minutes, so this is a good case showing its efficacy.

The WSO forecast office in Pago Pago was using this product to advertise the danger from lightning, as shown in the screenshot below for their Facebook page (direct link to the image). The time of the image below (ca. 0826 UTC) is after the end of the animation above; the lightning with this convective complex continued for several hours.

GOES-18 Level 2 products below (Lifted Index, left, scaled from -5 to 10 and Total Precipitable Water, right, scaled from 1 to 2.5 inches) show that the convection developed in a region where TPW and instability were both increasing to the north. Knowledge of the distribution of these level 2 products in concert with the development of LightningCast probabilities is a good indicator that convection will develop. The convection that developed eventually overspread Tutuila; the airport at Pago Pago received more than 0.5″ of rain.

View only this post Read Less

Overlapping 1-minute Mesoscale Domain Sectors provided 30-second interval GOES-16 (GOES-East) images from all 16 of the ABI spectral bands plus a Rocket Plume RGB (above) — which displayed signatures of the SpaceX Starship 2 rocket that was launched from the Starbase facility in Boca Chica Beach, Texas at 13:02:53 UTC on 18 November 2023. The Stage 1 rocket booster condensation cloud was evident in images from all 16 spectral bands, as it began to drift slowly southeastward away from the Texas coast — and the ascending rocket booster’s thermal signature was seen in Near-Infrared and Infrared spectral bands 03-16, as well as the Rocket Plume RGB.

A close-up view using 16-panel displays of all GOES-16 ABI spectral bands (below) showed that a reflectance signature of the Stage 1 rocket booster was evident in most of the Visible and Near-Infrared bands (01/02/03/05/06) at 13:02:55 UTC, along with a warm thermal signature in Infrared bands 07 and 11-15. After that time, warm thermal signatures then became apparent in all Near-Infrared and Infrared spectral bands (03-16) as the rocket began its ascent.

A larger-scale look at GOES-16 Upper-level Water Vapor (6.2 µm), Mid-level Water Vapor (6.9 µm), Low-level Water Vapor (7.3 µm) and Rocket Plume RGB images (below) allowed a signature of the Stage 2 rocket booster to be followed farther east across the Gulf of Mexico.

In a series of toggles between GOES-16 Upper-level Water Vapor (6.2 µm) and Shortwave Infrared (3.9 µm) images at 13:05:25 UTC, 13:06:25 UTC, 13:07:25 UTC and 13:09:25 UTC (below) a small cluster of warm 3.9 µm pixels (darker shades of orange-red) marked the exit point of hot exhaust from the Starship booster engines — and in 6.2 µm images, the trailing exhaust plume extended southwestward then westward from those warm 3.9 µm pixels. Note the change in exhaust plume shape with time and atmospheric layer: at altitudes of 61-101 km (where the Mesosphere and lower Thermosphere had more density, and higher ambient pressure), the plume was more linear — but at higher altitudes of 128-149 km (where the Thermosphere was much less dense, with lower ambient pressure) the plume was able to expand outward into more of a curved shape.

Thanks to Todd Beltracci, The Aerospace Corporation, for his analysis of Starship 2 test flight telemetry and how it related to the various GOES-16 image features.

View only this post Read Less

The Solar Ultraviolet Imager (SUVI) on GOES East captured a partial solar eclipse during the new moon on November 13th. But the moon’s shadow didn’t reach Earth. Why’s that?

Solar eclipses are only possible when the new moon occurs near the nodes of the lunar orbit, which is where the moon’s path intersects with the Sun-Earth ecliptic plane. This alignment makes it possible for the moon’s shadow to reach Earth’s surface and cause an eclipse.

Lunar nodes only align with the Sun-Earth line twice a year. The time on either side of that alignment is often called an “eclipse season.”  

Turns out geosynchronous satellites, which orbit Earth 22 thousand miles above the equator (several Earth diameters high) can pass through the lunar shadow during an eclipse season without the moon’s shadow reaching Earth, essentially meaning satellites have longer eclipse seasons than Earth.

Monday November 13 marked one lunar cycle since the October annular eclipse on Earth, so SUVI was within an extended satellite eclipse season and able to track the moon transiting the Sun from geostationary orbit.

View only this post Read Less

Metop-B and Metop-C both overflew Tropical Storm Mal as it approached the island of Fiji on 14 November. The toggle above shows the two wind plots from this website, MetopC from 0933 UTC and MetopB from 1013 UTC. The two swaths show the center of the storm moving southeast, skirting the main islands of Fiji. A shortcoming of ASCAT winds in tropical cyclones occurs when winds exceed 40 knots; the wind (and rain) perturbs the ocean surface sufficiently at those speeds to change the backscatter of microwave radiation back to the satellite. Still, ASCAT gives a good overall view of the outer wind fields, including where gales are occurring and where the circulation center sits.

RCM-1 (Radar Constellation Mission-1) overflew Mal at 0637 UTC on 14 November, and the Synthetic Aperture Radar (SAR) wind field from that is shown below (source). The wind analysis from the SAR data (here) suggests that the SW quadrant of the storm has the weakest winds. The blocking effect of the terrain from both Viti Levu (the largest island in the Republic of Fiji) and the Kadavu Islands is apparent in the imagery below, with weaker east-southeast winds in the lee of the islands.

The toggle below compares the SAR winds with the GOES-18 Clean Window infrared (Band 13, 10.35 µm) imagery. There is a significant parallax shift in the infrared imagery; the Republic of Fiji is just east of the dateline, and GOES-West is overhead at the Equator at 137.2^oW. The SAR-derived storm center is likely nearer to the center of the very cold clouds.

Satellite-derived winds are available hourly from GOES-18, and they are shown below. In the vicinity of Mal, only high-level winds can be generated, because only high-level cloud features can be tracked. The structure of Mal is acting as a blocking feature, and upper-level winds are diverted around it. In addition, a poleward outflow jet is apparent to the east and southeast of the storm. Note also the very strong shear at the southern edge of the domain. Low-level winds (in blue) are flowing in an opposite direction to the upper-level winds (in white).

---

A second SAR observation, this time from RCM-3, occurred at 1757 UTC. The toggle below shows the change in the infrared imagery between the two SAR observation times, one at 0640, one at 1750 UTC. The development of outer bands in the storm is most notable, as is the appearance of an eye-like structure at 1750 UTC.

By 1750 UTC, SAR winds show a significantly strengthened system southwest of Fiji. A circular eye that is more symmetric is apparent in the SAR imagery, and hints of an eye are starting to develop in the GOES-18 imagery. Note that the GOES-18 Visible imagery has been brightened (0-30 vs. the default 0-130) in this near-sunrise image. (Here is a toggle of the RCM-1/RCM-2 SAR Winds).

View only this post Read Less