Tropical Storm Karl in the middle of the Atlantic Ocean was a disorganized storm early on 19 September (as noted in these two discussions from the National Hurricane Center at 0300 and 0900 UTC): the surface circulation was displaced to the south and west of the deep convection. Night-time determination of the center location from infrared imagery for such storms is difficult. However, the Day/Night Band on the VIIRS instrument on board Suomi NPP can provide visible imagery at night and such visible imagery can aid in surface feature detection. The toggle above shows the 11.45 µm Infrared image from Suomi NPP just before 0400 UTC and the 0.70 µm Day/Night Band visible image from the same time. With the aid of ample illumination from the Moon (that was in the Waning Gibbous phase, at 85% of Full) the low-level swirl of clouds was apparent near the storm center at 18.2 N, 46.7 W (a bit south and west of the center as noted by the National Hurricane Center at 0300 UTC).
A zoomed-in image toggle centered on the low-level circulation is below.
(Imagery courtesy of William Straka, SSEC)
Tropical Storm Julia formed near the coast of northeastern Florida overnight on 13 September 2016 (NHC advisory archive) and moved inland over Jacksonville Florida. Suomi NPP Day/Night Band imagery, toggled above with 11.45 micron Infrared imagery shows a sheared system with most of the convection east and north of the center (that was at that time inland over Florida). Julia’s slow movement in combination with abundant moisture (a Total Precipitable Water product from this site is shown below) means flooding is likely in some regions.
===== 13 September Update =====Super Typhoon Meranti went through a secondary round of intensification on 13 September (ADT plot) , with the JTWC estimating maximum sustained winds of 165 knots with gusts to 200 knots at 21 UTC. CIMSS Satellite Consensus (SATCON) plots of wind and pressure indicated that Meranti reached peak intensity near the middle of the day. Himawari-8 Infrared Window (10.4 µm) images (above; also available as a 114 Mbyte animated GIF) continued to display a well-defined eye with an annular storm structure during this period. A faster version of the animated GIF better showed the pronounced trochoidal motion exhibited by the eye of Meranti, as it moved just south of the island of Taiwan. The eye of Meranti passed directly over the small Philippine island of Itbayat, as seen on Himawari-8 Infrared Window (11.45 µm) images viewed using RealEarth (above).
Suomi NPP overflew Meranti around 1730 UTC, just as the eye of the storm was passing over Itbayat. In a toggle between VIIRS Infrared Window (11.45 µm) and Day/Night Band (0.7 µm) images (below; courtesy of William Straka, SSEC) ample lunar illumination provided a very good “visible image at night” which also included a bright lightning streak emanating from the eastern eyewall of the Category 5 storm. The image pair also shows a good example of the “stadium effect” eye geometry (where the eye diameter at the surface is smaller, and opens to a wider distance with increasing height). A larger-scale view of the entire storm from the Day/Night Band is available here; the corresponding 11.45 µm Infrared image is available here.In a comparison of DMSP-15 SSMI Microwave (85 GHz) and Himawari-8 Infrared Window (11.45 µm) images around 1830 UTC (above), the appearance of concentric eyewalls on the microwave data suggested that Meranti was preparing to go through an eyewalll replacement cycle, which also signaled that the storm was perhaps near maximum intensity.
This formation of concentric eyewalls was nicely depicted by the MIMIC-TC product (below).
=====14 September Update =====
Less than 2 hours prior to landfall (which was around 1905 UTC on 14 September, over Xiamen City in the Fujian Province of China), a toggle between Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images at 1716 UTC (above) still showed well-defined curved banding structures around the center of of the Category 2 typhoon.
Himawari-8 Infrared Window (10.4 µm) images from pre-landfall at 0600 UTC on 14 September to post-landfall at 0600 UTC on 15 September (below; also available as a 47 Mbyte animated GIF) showed that Meranti quickly dissipated as it moved inland over mainland China. The images are centered on Xiamen (station identifier ZSAM); alternate animation versions with the BD grayscale enhancement are available in MP4 and animated GIF format.About 4 hours after landfall, good curved banding structure was still observed in DMSP-18 SSMIS Microwave (85 GHz) imagery at 2314 UTC, while the overall presentation of the storm on Himawari-8 Infrared Window (11.45 µm) imagery began to deteriorate (below).