VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images from NOAA-20 at 1502 UTC (above) and from Suomi NPP at 1552 UTC (below) showed Category 2 Typhoon Wutip in the West Pacific Ocean (southeast of Guam) on 21 February 2019. With Moon in the Waning Gibbous phase (at 95% of Full), ample illumination was provided to highlight the “visible image at night” capability of the Day/Night Band.

Notable features included deep convection near the storm’s center of circulation (with the presence of subtle cloud-top gravity waves), and transverse banding along the eastern periphery of the cold central dense overcast. Bright pixels seen in the Suomi NPP Day/Night Band image were the result of clouds being illuminated by lightning activity. VIIRS images courtesy of William Straka, CIMSS.

===== 22 February Update =====

Typhoon Wutip intensified to a Category 3 storm on 22 February (ADT | SATCON) — rapid scan JMA Himawari-8 Infrared Window (10.4 µm) images at 2.5 minute intervals (above) revealed cloud-top infrared brightness temperatures of -90ºC and colder (yellow pixels surrounded by darker purple) shortly after 00 UTC. Multiple convective bursts developed around the center of circulation, and evidence of eye formation was seen for a short time beginning around 1137 UTC.

Himawari-8 “Red” Visible (0.64 µm) images of Wutip (below) showed that a distinct cloud-free eye did not form during that time period.

A DMSP-17 SSMIS Microwave (85 GHz) image from the CIMSS Tropical Cyclones site (below) showed a nearly complete ring of strong convection around the eye region at 0916 UTC. A 24-hour animation of MIMIC-TC morphed microwave imagery is available here.

Prior to becoming a typhoon, Wutip had been moving over water with warm Sea Surface Temperatures and high Ocean Heat Content values (below).

===== 23 February Update =====

2.5-minute rapid scan Himawari-8 Infrared Window (10.4 µm) images (above) revealed the formation of a large and well-define eye with an annular eyewall structure as Wutip rapidly intensified (ADT | SATCON) to Category 4 Super Typhoon status on 23 February. Mesovortices could be seen rotating within the eye. Wutip became the most intense February typhoon on record in the Northwest Pacific basin.

In a toggle between NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images at 1602 UTC (below), these mesovortices were also apparent — with the help of reflected moonlight — in the Day/Night Band.

As noted in a 21 UTC discussion from the JTWC, Wutip had a well-defined poleward outflow channel within the upper troposphere (below), which was a favorable factor for its intensification.

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GOES-17 is typically operational using Mode 3 Scanning, in which mode Full Disk images are acquired every 15 minutes (in addition to a PACUS sector every 5 minutes and two mesoscale sectors every minute).  NOAA/NESDIS plans a transition to operational Mode 6 scanning at some point in Spring, and testing for that is ongoing.  In Mode 6, Full Disk images are acquired every 10 minutes (while maintaining the 5-minute PACUS imagery and two 1-minute Mesoscale sectors), a Full Disk sequencing that aligns with Himawari-8 Full Disk image acquisition.  This means that stereoscopic views using GOES-17 (overhead at 137.2º W) and Himawari-8 (overhead at 140.8º E) can be created with a 10-minute time step when GOES-17 is in Mode 6 (vs. every 30 minutes when GOES-17 is operating in Mode 3, as shown here).

The stereoscopic animation above shows tropical convection that was trailing western Pacific then-Tropical Storm Wutip (link 1,  link 2 on Typhoon Wutip);  The three-dimensions apparent in the stereoscopic imagery allow for easy identification of vertical shear — over the southwestern corner of the image, for example.

Tropical Storm Wutip was on the extreme limb of GOES-17’s field of view on 20-21 February; nevertheless, data could be used to view the storm, in stereo, with Himawari-8. That animation is shown below.  Wutip is on the western edge of the imagery.

Himawari-8 imagery is courtesy the Japan Meteorological Agency, JMA.

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Stereoscopic views of Visible Imagery (from GOES-16 and GOES-17, above) allow for visualization of three dimensions, as shown in the mp4 animation above (click here for an animated gif of the same scene). The imagery captures multiple cloud layers over the western United States (a map will show up in the animation) as a potent system moved eastward.

GOES-R includes four channels in the near-visible including the Cirrus Channel at 1.37 µm. The Cirrus Channel is useful here because the water vapor absorption of 1.37 µm energy means that any near-surface signal is absorbed, so mostly high-level clouds are present (low clouds become visible in the cirrus channel in very dry atmospheres). The animation below (the animated gif is here) is a stereoscopic view created with 1.37 µm imagery and the structure of the high clouds is more apparent.

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Both GOES-16 (GOES-East) and GOES-17 (GOES-West) were placed into the Mode 6 scan strategy for a 3-day period of testing beginning at 1500 UTC on 19  February 2019 — which provides Full Disk images every 10 minutes (instead of every 15 minutes for the more common Mode 3 scan strategy). Further details on GOES-R series scan modes are available here and here. GOES-16 Full Disk “Red” Visible (0.64 µm) images are shown above, with Mid-level Water Vapor (6.9 µm) images below.

One of the more striking features over the North Atlantic Ocean was a rapidly-intensifying Hurricane Force low — an animation that cycles through GOES-16 Visible and Water Vapor images of this system is displayed below.

GOES-16 Air Mass RGB images from the AOS site (below) exhibited the orange-to-red hues of ozone-rich air within the atmospheric column due to a lowered tropopause associated with the rapidly deepening North Atlantic storm.

Looking to the west with GOES-17, Full Disk animations of Visible and Water Vapor images are shown below.

The more frequent 10-minute images allowed a short-lived signature of orographic waves within a transient dry slot immediately downwind (northeast) of Atka (PAAK) in the Aleutian Islands of Alaska  (below) — such a signature often indicates a high potential of turbulence. There were also areas of transverse banding seen with the jet stream cirrus just southeast of Atka (another satellite signature of turbulence).

Similar to what was seen over the North Atlantic, GOES-17 Air Mass RGB images (below) exhibited the orange-to-red hues of ozone-rich air within the atmospheric column due to a lowered tropopause poleward of the jet stream axis as it moved northeastward across the Aleutians.

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