The KNP Complex wildfire continued to burn in central California on 04 October 2021, producing a pair of pyrocumulonimbus or pyroCb clouds — one during the atypical late morning hours (beginning around 1530 UTC, or 11:30 am PDT) and the other during the more typical late afternoon hours (beginning around 2130 UTC, or 5:30 PM PDT). 1-minute Mesoscale Domain Sector GOES-17 (GOES-West) “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.35 µm) images (above) showed the pyroCB clouds, fire thermal anomalies or “hot spots” (clusters of red pixels) and cold cloud-top infrared brightness temperatures, respectively. The minimum 10.35 µm temperatures were near -60ºC. Note the relatively warm (darker gray) appearance of the pyroCb clouds in the 3.9 µm images — this is a characteristic signature of pyroCb cloud tops, driven by the smoke-induced shift toward smaller ice particles (which act as more efficient reflectors of incoming solar radiation, contributing to the warmer 3.9 µm brightness temperatures). Note: beginning at 1700 UTC, overlapping GOES-17 Mesoscale Sectors provided imagery at 30-second intervals.

1-minute GOES-17 True Color RGB images created using Geo2Grid (below) showed the first pyroCb cloud as it continued to move northeastward across the California/Nevada border, and then the second pyroCb cloud as it moved northwestward. The change in direction of motion was influenced by the approach of an offshore closed low from the west (250 hPa analysis: 12 UTC | 00 UTC). 

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US Space Force EWS-G1 (formerly GOES-13) Infrared Window (10.7 µm) images (above) showed
Hurricane Shaheen weakening to a Tropical Storm shortly after it made a rare landfall along the coast of Oman on 03 October 2021. The storm exhibited an eye at times as it was a Category 1 Hurricane over the Gulf of Oman. This was likely the first tropical cyclone to make landfall along that coastal portion of Oman since 1890 (Wikipedia).

Meteosat-8 Infrared images, with contours of deep-layer wind shear from the CIMSS Tropical Cyclones site (below) indicated that the storm was moving through an environment of low shear.

Suomi-NPP VIIRS True Color RGB and infrared Window (11.45 µm) images viewed using RealEarth (below) showed the Category 1 Hurricane at 0927 UTC.

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GOES-17 (GOES-West) Dust RGB and Ash RGB images (above) revealed a plume of resuspended volcanic ash — from the 1912 eruption of Novarupta-Katmai — moving southeastward across the Shelikof Strait toward Kodiak Island in southern Alaska on 02 October 2021. The remnant ash on the surface was lofted by strong northwesterly winds along  the rear edge of Hurricane Force and Storm Force lows in the Gulf of Alaska (surface analyses), and imagery suggested that the ash  plume (shades of pink to magenta) began to develop just after 0600 UTC. At Buoy 46077 in the Shelikof Strait, a peak wind gust of 35 knots occurred around 14 UTC.

Both RGB image combinations use the same ABI spectral bands, but in this case the plume of airborne ash showed up a bit better on the Dust RGB  (below) because of how the 3 components of that RGB are scaled.

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Alexa Ross, a scientist at CIMSS (and CIMSS Blog contributor) has created a Matlab program that reads in NUCAPS EDR data from any Direct Broadcast datastream (here, for example), or from NOAA CLASS, and creates color-coded plots at NUCAPS data levels (that is, at any one of the 100 pressure levels used in the Radiative Transfer Model that drives the retrieval). Output from the program for four separate granules between 1817 and 1819 UTC is shown above. Temperatures are notably warmer over land than over the Atlantic Ocean, a temperature distribution in agreement with GFS model output (GFS model imagery from the College of Dupage website).

This program does not (as yet) indicate whether or not the retrieved profile has converged to a solution. It is up to a user to apply some quality control to the data. The very warm pixel at 1817 UTC over the Atlantic Ocean, for example, looks suspect. Cloud imagery is an important tool for anticipating whether a retrieval will converge — click here to see an 1820 UTC GOES-16 True-Color imagery over the scene, taken from the CSPP Geosphere site.

Gridded NUCAPS (available from this NASA SPoRT website) can also be used to view the horizontal distribution of temperatures across the NUCAPS data swath. The toggle below shows the 850-mb Temperature field and also the Quality Control flags.

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