Himawari-9 Infrared Imagery, above, shows Mawar as it develops and eye and strenghtens to Super Typhoon status. The animation above shows a well-developed symmetric storm with good outflow from all quadrants. The eye is seemingly in steady state from about 0300-0900 UTC, after which time its size shrinks. The 0600 UTC update from the Joint Typhoon Warning Center reported a central pressure near 923 mb. Based on the analysis of heat content in the ocean (from the SSEC Tropical Weather Website), below, Mawar is close to its maximum strength.

The DPRINT product (formerly called Open-AIIR), a Machine-Learning tool that estimates winds based on satellite presentation, available at the SSEC Tropical Weather Website, suggests a peak in intensity occurred around 1000 or 1100 UTC on 23 May. However, Mawar remains a Super Typhoon. Microwave observations of the eyewall structure (here), can be used to monitor the possibility of an Eyewall Replacement Cycle (ERC), which cycle will be responsible for short-time period variations in typhoon strength from now through landfall on/near Guam. Such cycles are challenging to predict in advance.

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The RCM-2 satellite made another overpass over Mawar, this time at 0830 UTC on 23 May (previous SAR Observations are discussed here and here). The image below compares the SAR observations with the Target Himawari Band 13 (Clean Window, 10.4 µm) image. The strongest SAR winds are not completely encircling the eye. All Mawar SAR observations/analyses can be accessed here.

Waves at Ipan, southeast of Guam, shown below, have increased to 16 feet. Significant coastal flooding is expected on Guam with this storm.

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Current forecasts have the path of Mawar bisecting the island of Guam. Refer to the National Weather Service Guam Forecast office website for more information (Local statements from the Guam forecast office are here). Other information is available at the JTWC and Tokyo RSMC.

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Update, 1700 UTC on 23 May

The satellite presentation of Mawar has degraded, and the eye is no longer so striking in satellite imagery. The animation below runs from 0634 UTC, when the eye is distinct, through 1657 UTC on 23 May.

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Target Sector (2.5-minute interval) JMA Himawari-9 Visible and Infrared images (above) covered the period when Typhoon Mawar reached Category 4 intensity at 0000 UTC on 23 May 2023 (JTWC advisory | SATCON | ADT). Mesovortices within the eye were evident in the Visible imagery, and cloud-top infrared brightness temperatures surrounding the eye were frequently -80ºC or colder (shades of violet).

A Suomi-NPP VIIRS Day/Night Band (0.7 µm) image valid at 0320 UTC on 23 May (below) showed a larger-scale view of Typhoon Mawar as it was centered about 200 miles southeast of Guam.

A few hours prior to reaching Category 4 intensity, a DMSP-17 SSMIS Microwave (85 GHz) image at 2047 UTC on 22 May (above) revealed a small eye, with spiral bands wrapping into the storm center. An ATMS Microwave (183 GHz) image at 0319 UTC on 23 May (below) showed Mawar a few hours after it reached Category 4 intensity.

Himawari-9 Infrared Window (11.2 µm) images with an overlay of deep-layer wind shear at 0000 UTC from the CIMSS Tropical Cyclones site (below) indicated that Mawar was moving through an environment where the shear gradient was large (but likely decreasing along the storm’s northwestward path). Aiding intensification was the fact that Mawar was traversing very warm water (Ocean Heat Content | Sea Surface Temperature).

Several hours after sunset, a Suomi-NPP VIIRS Day/Night Band (0.7 µm) image valid at 1554 UTC on 23 May (below) revealed mesospheric airglow waves (reference) radiating westward through northward away from Mawar (whose eye was located less than 100 miles southeast of Guam, PGUM, at the time of the image). These vertically-propagating gravity waves were generated by deep convection within Mawar’s eyewall.

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Typhoon Mawar in the western Pacific is moving towards the southern Marianas (the islands of Guam and Rota are both under a Typhoon warning). Radar Constellation Mission Satellite 2 (RCM-2) overflew the storm at 0813 UTC on 21 May, and at 0821 UTC on 22 May, and a toggle of the observations is shown below. The storm is far better organized on 22 May, with a distinct eye and eyewall present in the SAR winds as shown in the toggle below. Peak instantaneous winds increased from around 70 knots on 21 May to 85 knots on 22 May (shown in this toggle using images taken from this website), and the storm has increasing symmetry. Note: the 0600 UTC update from the JTWC discussed peak 1-minute sustained winds of 90 knots.

How did the Himawari-9 infrared imagery change within those same 24 hours? The 4-panel below includes the SAR data on the left and Band 13 “Clean Window” infrared imagery (10.4 µm) from Himawari-9 on the right. Very cold cloud tops persist over the center of the storm, but an obvious eye is not yet apparent in the infrared imagery, at least not at the times shown. A prominent outer rainband is apparent in the imagery from 22 May to the north of the eye.

The zoomed-out imagery, below, shows the evolution and movement of the storm between 0810 UTC 21 May and 0820 UTC 22 May, the approximate times of the SAR overpasses. As of 0600 UTC, Mawar was located 280 miles south-southeast of Guam, moving north-northwestward at 6 knots, with a central sea-level pressure of 969 mb.

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More information on this dangerous storm is available at the website of the Guam National Weather Service (link), at the Joint Typhoon Weather Center (link), at the Tokyo RSMC (link) and at the SSEC Tropical Weather website (link).

Added: The Himawari-9 Target Sector has been over Mawar for several days now, providing imagery every 2.5 minutes. An mp4 animation showing the evolution of the storm on 21-22 May is below. The development of an eye appears to occur at the end of the animation.

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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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