Widespread clouds can easily hide the location of active precipitation. When that happens, well-timed microwave information can show where precipitation is most likely. In the slider example above, Aqua MODIS infrared imagery with a grey-scaled enhancement (collected over Guam just before 0350 UTC on 9 July) shows regions of convection west and south of Guam (circled in yellow). Where are the heaviest rains located, and where are the stratiform rains, and what regions are mostly dry, but under clouds? GCOM-W1 AMSR-2 data (collected over Guam around 0403 UTC on 9 July) can give information to address those questions. In this case, it reveals the regions underneath the clouds where strongest convection is most likely. This example highlights why JPSS data can be so vital in regions where radar coverage is lacking (or when the radar goes down!): because the microwave data can give important information about what’s going on underneath the cloud canopy.

Of course, enhancements to the infrared imagery can also provide information, especially about how things are evolving with time. That’s shown in Himawari-9 infrared imagery (Clean window, Band 13 — 10.4 µm — and Upper-level Water Vapor, Band 8 — 6.25 µm) shown below. Note the appearance and decay of multiple cold cloud tops in the infrared data as convective towers evolve with time. A best practice is to combine the information gained by the snapshot given by the microwave data and use that information to infer what is occurring underneath the clouds in the geostationary data.

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The imagery below compares NOAA-20 VIIRS imagery and rain rate derived from ATMS (at 0322 UTC) to the same GCOM AMSR-2 imagery as shown above.

Many thanks to Brandon Aydlett, Science and Operations Officer, WFO Guam, for the Aqua MODIS, Suomi-NPP and GCOM-W1 AMSR-2 imagery that was downloaded at the WFO GUM L/X Band direct broadcast antenna and processed with CSPP software.

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GOES-18 (GOES-West) “Clean” Infrared Window (10.3 µm) and “Red” Visible (0.64 µm) images (above) included plots of the 15 Severe Thunderstorm Warning polygons issued by NWS Fairbanks on 07 July 2023 — which was a record number of warnings issued by that forecast office for a single calendar day. The coldest cloud-top 10.3 µm infrared brightness temperatures were -51C — which corresponded to an altitude around 36,000 feet, according to 0000 UTC rawinsonde data from Fairbanks (below).

Recall that when viewing geostationary imagery at high latitudes, parallax must be taken into account — for example, the cold overshooting top east of Fort Yukon seen on the 0410 UTC image (above) was actually located over a point about 35 km (22 miles) to the south-southeast (below), placing it closer to Circle.

In GOES-18 Day Cloud Phase Distinction RGB images (below), developing cumulus clouds that were beginning to glaciate exhibited shades of green. Given that many of these thunderstorms occurred in rather remote areas, verification was difficult — but there was one report of tree damage in Chalkyitsik.

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GOES-18 (GOES-West) Day Land Cloud Fire RGB, Shortwave Infrared (3.9 µm), “Clean” Infrared Window (10.3 µm) and Near-Infrared “Vegetation” (0.86 µm) images with an overlay of the Fire Power derived product (a component of the GOES Fire Detection and Characterization Algorithm FDCA) (above) showed that the Hossitl Creek wildfire complex northeast of Fort Nelson (CYYE) — in far northeastern British Columbia (and far southwestern Northwest Territories) — produced a pair of pyrocumulonimbus (pyroCb) clouds on 05 July 2023. Strong northeasterly winds in the wake of a cold frontal passage likely played a role in the rapid flare-up of ongoing fires (and the subsequent pyroCb development).

The thermal signature of active wildfires along the southern perimeter of the complex was either partially or completely masked by clouds much of the time, but one fire did exhibit 3.9 µm brightness temperatures as hot as 76.1ºC and Fire Power values as high as 1550.7 MW (both occurring at 2010 UTC). The pyroCB clouds exhibited cloud-top 10.3 µm infrared brightness temperatures as cold as -54.54ºC at 0110 UTC — at that same time/location, the CIMSS-derived CLAVR-x Cloud Top Temperature was -58.27ºC, with a corresponding Cloud Top Height of 40,266.81 feet (below).

In GOES-18 True Color RGB images from the CSPP GeoSphere site (below), shades of tan to light brown helped to identify the smoke-laden anvil of the pyroCb clouds as they merged and drifted southeastward across the British Columbia / Alberta border.

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GOES-18 (GOES-West) Nighttime Microphysics RGB and daytime True Color RGB images from the CSPP GeoSphere site (above) displayed the cyclonic circulation of an actinoform cloud feature as it moved westward toward Hawai`i on 03 July 2023.

A closer view using GOES-18 “Red” Visible (0.64 µm) and Day Cloud Phase Distinction RGB images (below) showed the actinoform cloud as it approached the island of Oahu. 15-minute METAR surface reports revealed that one of the actinoform’s “spiral bands” produced brief (20-30 minute) periods of light rain and/or drizzle — first at Kaneohe Bay (PHNG) beginning around 0201 UTC, and then at Wheeler Air Force Base (PHHI) beginning around 0331 UTC — as it passed over the island.

According to the Day Cloud Phase Distinction RGB Quick Guide, shades of green generally denote cloud tops that are beginning to glaciate — but in this case, a GOES-18 Day Cloud Phase Distinction RGB image at 2301 UTC (below) included cursor-sampled values of RGB components along with the corresponding Cloud Top Phase and Cloud Top Height derived products at that same location. Since cloud-top 10.3 µm infrared brightness temperatures at that cursor location were quite warm (15.27ºC), derived products indicated that the Cloud Top Phase was Water (as opposed to a Mixed water/ice phase, which is often associated with cloud features exhibiting similar shades of green in this particular RGB).

AWIPS Users: a variety of GOES RGB types combined with Derived Product Readouts is available under the Satellite -> Local Menu Items menu (below).

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