Himawari-9 Band 10 (Low-level water vapor, 7.3 µm) infrared imagery, above, shows Tropical Storm Mawar to the southeast of Guam. At 0600 UTC, Mawar’s center was about 400 miles south-southeast of the island of Guam. The short water vapor animation above shows an expanding cirrus shield with outflow in all directions. Mawar is expected to become a typhoon later today, and all interests in the southern Marianas islands (Guam and the CNMI are under a Typhoon Watch) should be monitoring the progress of this storm as it approaches.

Canada’s RCM-2 (RADARSAT Constellation Mission-2) Satellite, carrying Synthetic Aperture Radar (SAR), overflew the system at 0813 UTC on 21 May. The toggle below compares Clean Window infrared imagery (Band 13, 10.4 µm) from Himawari-9 and the SAR wind analysis at nearly the same time. SAR instantaneous winds are close to 70 knots (see this figure, from here). The SAR imagery does not show a closed-off eye. Himawari-9 shows very cold cloud tops to the west of the SAR-diagnosed surface center, with Band 13 Brightness temperatures close to -95^oC. The parallax shift in the Himawari-9 imagery for very cold cloud tops near 148^oE Longitude (Himawari-9 is over the Equator at 140.7^oE) will not be excessive; however, those coldest cloud tops are in reality a bit farther to the east.

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UPDATE: Mawar intensified to a Category 1 Typhoon at 1200 UTC (JTWC advisory) — 2.5-minute rapid scan JMA Himawari-9 “Clean” Infrared Window (10.4 µm) images (below) showed the cold overshooting tops that continued to exhibit infrared brightness temperatures in the -90 to -95ºC range.

Himawari-9 Infrared Window (11.2 µm) images with an overlay of deep-layer wind shear at 1200 UTC from the CIMSS Tropical Cyclones site (below) indicated that Mawar was moving through an environment of low shear — which, in addition to the storm traversing warm water (Sea Surface Temperature + Ocean Heat Content) favored a continuing trend of intensification.

Interests in Guam and the CNMI (the southern Marianas Islands) should closely monitor the progress of Mawar. Refer to the Joint Typhoon Warning Center (Link), the National Weather Service in Guam (Link) and the Tokyo RSMC (Link) for more information.

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1-minute Mesoscale Domain Sector GOES-18 (GOES-West) Fire Temperature RGB and “Clean” Infrared Window (10.3 µm) images (above) showed the intensification of 3 wildfires in northeast British Columbia on 20 May 2023. Two of the fires produced pyrocumulonimbus (pyroCb) clouds, exhibiting cloud-top 10.3 µm infrared brightness temperatures of -50ºC or colder (shades of red) — which then eventually moved eastward across far northwest Alberta.  The southernmost fire continuously exhibited a 3.9 µm infrared brightness temperature of 137.88 K — the saturation temperature of GOES-18 ABI Band 7 detectors — for a period of 70 minutes (from 2240-2350 UTC).

During the time period that the fires were burning very hot and beginning to produce pyroCB clouds, 1-minute GOES-18 Fire Temperature RGB images and “Red” Visible (0.64 µm) images with an overlay of the Fire Power derived product (below) showed that the southernmost fire frequently exhibited Fire Power values in excess of 5000 MW (with a peak of 5487.76 MW at 2304 UTC). The Fire Power derived product is a component of the GOES Fire Detection and Characterization Algorithm (FDCA).

The subsequent motion of the 2 pyroCb anvils was evident in GOES-18 Nighttime Microphysics RGB imagery from the CSPP GeoSphere site (below), as they drifted southeast across Alberta and Saskatchewan.

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As West Pacific Tropical Depression 02W — previously discussed in this blog post — intensified to become Tropical Storm Mawar at 1200 UTC on 20 May 2023, 2.5-minute rapid scan JMA Himawari-9 “Clean” Infrared Window (10.4 µm) images (above) showed pulses of cold overshooting tops that frequently exhibited infrared brightness temperatures in the -90 to -95ºC range.

Himawari-9 Infrared Window (11.2 µm) images with an overlay of deep-layer wind shear at 1800 UTC from the CIMSS Tropical Cyclones site (below) indicated that Mawar was moving into an environment of lower shear, which favored a trend of continued intensification.

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GOES-18 (GOES-West) “Clean” Infrared Window (10.3 µm) images (above) showed the formation of a pyrocumulonimbus (pyroCb) cloud — produced by a wildfire southwest of Fort Nelson, British Columbia (station identifier CYYE) — around 2340 UTC on 19 May 2023. Cloud-top infrared brightness temperatures reached -61ºC as the pyroCb cloud drifted eastward across Alberta.

GOES-18 True Color RGB and Nighttime Microphysics RGB images from the CSPP GeoSphere site (below) showed the late-day pyroCb formation and its subsequent eastward motion after sunset.

VIIRS Infrared Window (11.45 µm) images from Suomi-NPP (valid at 0952 UTC) and NOAA-20 (valid at 1042 UTC) are shown below. Cloud-top infrared brightness temperatures were as cold as -63ºC in the NOAA-20 image (which is mislabeled as NPP).

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