2.5-minute interval rapid scan JMA Himawari-8 Infrared Window (10.4 µm) images (above) showed Typhoon Surigae undergoing rapid intensification (ADT | SATCON) to become a Category 4 storm as of 18 UTC on 16 April 2021.

A DMSP-16 SSMIS Microwave (85 GHz) image from the CIMSS Tropical Cyclones site (below) displayed a well-defined eye, with distinct spiral bands feeding into the eyewall.

After sunrise, Himawari-8 “Red” Visible (0.64 µm) images (below) showed the relatively compact eye, with hints of low-level mesovortices within the eye.

===== 17 April Update =====

The prolonged period of rapid intensification continued overnight, and as of 12 UTC on 17 April Surigae had become a Category 5 Super Typhoon — 2.5-minute interval rapid scan Himawari-8 Infrared images (above) showed the well-defined eye as the storm tracked northwestward across the Philippine Sea (just east of the Philippines). A faster animation (GIF | MP4) helped to highlight the trochoidal motion (wobble) of the eye — a behavior often seen with intense tropical cyclones. The 21 UTC advisory from JTWC listed sustained winds of 165 knots (and objective intensity estimates from ADT and SATCON were around 170 knots), making Surigae the only tropical cyclone on record to reach that intensity during the month of April.

Year and date of all 165kt tropical cyclones on record around the world. pic.twitter.com/JLUwjceapf

— Sam Lillo (@splillo) April 17, 2021

An animation of Himawari-8 Infrared images with an overlay of deep-layer wind shear (below) indicated that Surigae was moving through a region of low to moderate wind shear; the storm was also moving across very warm water (SST + OHC).

Around the time that Surigae was reaching its peak intensity, a Suomi NPP VIIRS Day/Night Band (0.7 µm) image several hours before sunrise (below) revealed concentric mesospheric airglow waves (reference) propagating away from the energetic Category 5 tropical cyclone.

In closer view of time-matched Himawari-8 Infrared and Suomi NPP Day/Night Band images (below), a cluster of bright DNB pixels highlighted the presence of lightning activity along the inner edge of the northern eyewall.

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2.5-minute interval rapid scan JMA Himawari-8 Infrared Window (10.4 µm) images (above) revealed intermittent cloud-top infrared brightness temperatures of -100ºC and colder (red pixels embedded within yellow-to-black inner cores) — with the coldest being -101.7ºC at 1342 UTC — within the Central Cold Cover (CCC) pattern of Tropical Storm Surigae on 15 April 2021.

A zoom-in of NOAA-20 VIIRS Infrared Window (11.45 µm) imagery at 1644 UTC as viewed using RealEarth (below) also showed 2 clusters of red -100ºC and colder pixels, with a minimum of -103.6ºC (incidentally, the coldest pixels on the 1644 UTC Himawari-8 Infrared image were -96ºC). About an hour and 15 minutes after this NOAA-20 image, Surigae was upgraded to a Category 1 typhoon (the first typhoon of the 2021 season in the West Pacific basin).

A plot of 12 UTC rawinsonde data from Yap Island showed that the coldest air temperature was -84.7ºC at 100 hPa (16.7 km) — so an overshooting top of -100ºC or colder indicated a significant vertical ascent above the tropopause.

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Himawari-8 Window Channel infrared imagery (10.41 µm), above, shows a well-defined tropical disturbance (Tropical Depression #2 has become become Tropical Storm Surigae by 0900 UTC on 14 April; this website shows Pacific basin names and includes audio pronunciation examples) moving between Yap and Palau in the western Pacific to the southwest of Guam. The disturbed weather in this region has persisted for many days as it has moved towards the west-northwest, as shown in the rocking MIMIC Total Precipitable Water animation below.

NOAA-20 NUCAPS estimates of tropopause Heights, below, show the storm in a region with a very high tropopause, around 120 hPa. The system is moving towards a region with similarly high tropopauses.

Water Vapor imagery (6.24 µm and 7.3 µm) from near sunrise of 14 April show moist air in the immediate environment surrounding the storm (Link).  Visible imagery at sunrise on 14 April, below, show strong and persistent deep convection.

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It is interesting to note that during the ~12 hours prior to the disturbance (dubbed Tropical Invest 94W) being named Tropical Depression 02W at 12 UTC on 13 April, 2.5-minute interval Himawari-8 Visible (0.64 µm) images from 0002-0802 UTC (below) revealed a trio of low-level vorticies circulating around the incipient storm center. The northernmost vortex appeared to play a role in the initiation of a small cluster of sheared convection. While an exposed low-level circulation center is common in deteriorating highly-sheared tropical cyclones, the presence of 3 vortices during the formative stages of development is rather unusual.

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Imagery from the CIMSS Tropical Weather Site (link), below, shows the system in a region of very warm Sea Surface Temperatures and modest shear.  Strengthening is forecast as it moves towards the Philippines.

 

Himawari-8 Imagery courtesy of JMA, the Japan Meteorological Agency.

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CSPP GeoSphere allows a user to view True Color imagery (and individual GOES-16 bands) in real time using data from the four GOES-16 domains:  Full Disk, CONUS, and Mesoscale Sectors 1 and 2.  The animation above shows the 1330 UTC eruption (11 April 2021) of Soufriere, one of a series of eruptions from that volcano (as discussed here and elsewhere).  The ash emitted by the short (duration) eruption then moves westward towards Barbados, following upper-level winds.  (Low-level winds are easterly).  The rapid ascent of the ash cloud is documented below, showing 4 images from the Full Disk imagery at 1320, 1330, 1340 and 1350 UTC.

Rapid changes suggest Mesoscale imagery would be useful.  Indeed, volcanic events area ranked #2 on the GOES-R MDS Priority List, after only a SPC High/Moderate Risk for Severe weather.  Thus, mesoscale Sector 2 imagery was available over the area.   That is shown below and it better captures the time of the eruption and better resolves the ascent through the troposphere.

Seven consecutive zoomed-in 1-minute images are shown below, from 1329 through 1336 UTC on 11 April (with the map removed; CSPPGeo link used here; a similar animation from the CIRA Slider is here.) They show the initial stages of this particular eruption.  A Pileus cap is obvious at the top of the eruption at 1329 UTC. (Animation available here as an mp4).

Quantitative information on some aspects of this series of events can be found at the VOLCAT website.  You can also find information at the Washington DC VAAC (Volcanic Ash Advisory Center).

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