The hourly water vapor animation above over the Atlantic Basin shows the evolution of a strong tropical wave that moved through the Greater Antilles during the week of 23-29 August 2016. (GOES-14 viewed this system on 25 August and 28 August). There are many areas of convection, including Hurricane Gaston, which storm enters the domain from the east. Gaston is no threat to land, however.

Of more interest to the United States are Tropical Depression #8, a small system just southeast of Cape Hatteras, represented as a circular cluster of thunderstorms at the end of the animation, and Tropical Depression #9 near western Cuba. (Click here for an annotated water vapor imagery identifying the storms) Tropical Depression #9 has emerged from the system discussed here. Interests along the coast of North Carolina and Virginia should pay close attention to forecasts on Tropical Depression #8, and those on the Gulf Coast from Louisiana eastward should monitor Tropical Depression #9. For the latest information, see the webpages of the National Hurricane Center.

MIMIC Total Precipitable Water, below, for the 72 hours ending at 1800 UTC on 29 August (from this site), shows that Tropical Depression #8 and Hurricane Gaston, are near regions of dry air that might influence their evolution. In contrast, Tropical Depression #9 is embedded within an atmosphere rich in moisture.

The next two names for tropical cyclones in the Atlantic are Hermine and Ian.

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Typhoon Lionrock (12W) in the West Pacific Ocean briefly intensified to Category 4 during the northeastward motion segment of its rather unusual track (above) — the intensity estimate from the Advanced Dvorak Technique peaked at 112.4 knots from 2140 UTC on 26 August to 0630 UTC on 27 August (plot | text).

During this period of intensification, 2.5 minute interval rapid-scan Himawari-8 Visible (0.64 µm) and Infrared Window (10.4 µm) images (below; also available as a large 85 Mbyte animated GIF) revealed complex patterns of cloud-top radial and transverse banding. Surface mesoscale vortices were also seen at times within the open eye feature.

A few hours later, the Category 3 intensity typhoon continued to exhibit a well-defined eye structure in both DMSP-15 SSMI Microwave (85 GHz) and Himawari-8 Infrared Window (10.4 µm) images around 18 UTC (below).

During the nighttime hours preceding the intensification to Category 4, a comparison of Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images (below; courtesy of William Straka, SSEC) showed the eye of Lionrock at 1631 UTC on 26 August.

===== 28 August Update =====

Typhoon Lionrock again intensified to a Category 4 storm on 28 August; a comparison of 2.5 minute interval rapid-scan Himawari-8 Visible (0.64 µm) and Infrared Window (10.4 µm) images is shown above (also available as a large 68 Mbyte animated GIF).

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GFS model fields from this site (above) showed a relatively compact storm that was deepening as it moved northeastward across southern and central Norway on 26 August 2016.

EUMETSAT Meteosat-10 Visible (0.75 µm) and Infrared Window (10.8 µm) images (below; also available as an MP4 animation) revealed the development of thunderstorms over southern Norway during the 0900-1300 UTC period. Cloud-to-ground lightning from one of these storms is believed to have killed 323 reindeer near the southeastern corner of the Hardangervidda National Park (which is located in the center of the visible and infrared satellite images).

The coldest cloud-top infrared brightness temperatures of the thunderstorms on the 1100 UTC image was -51º C, which corresponded to an altitude of around 10.5 km on the 1200 UTC Ørland rawinsonde report (below) — looking at the individual sounding profiles, Ørland to the north of Hardangervidda was still in the moist convective environment near the center of the storm system, while Stavanger to the south began to show the drier air aloft in the wake of the northeastward-moving storm.

A composite of Suomi NPP VIIRS true-color Red/Green/Blue (RGB) image swaths as viewed using RealEarth (below) showed the widespread thunderstorms across southern Norway on the earlier (eastern) 1103 UTC overpass, while the later (western) 1243 UTC overpass showed the effects of the mid-level drier air that was beginning to overspread the region as the center of the parent storm system moved northeast.

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GOES-14 SRSO-R Imagery is being produced over the Greater Antilles on 25 August 2016 to monitor a tropical wave (Invest 99L) that is moving towards Florida and the southeast United States. The visible animation above shows a highly sheared system: a low-level circulation center (LLCC) is evident north of Hispaniola and east of the Turks and Caicos, but strong convection (overshooting tops are readily apparent) is displaced well to the east of the system. There is also considerable convection over Hispaniola.

A 2-panel comparison of GOES-14 Visible and Infrared Window images, below (also available as a large 200 Mbyte animated GIF), provided a slightly closer view of the LLCC feature.

Wind shear analyses from the CIMSS Tropical Weather site, below, show the surface circulation is within a small ribbon of relatively strong shear. Development chances will increase if the wind shear relaxes. A GOES-13 Visible image with overlays of satellite winds and wind shear is available here.

Metop-A overflew the system at about 0200 UTC on 25 August (link to orbit path), and winds near Tropical Storm Force cover a wide swath of the southwestern Atlantic. Even if this system does not develop into a Tropical Depression, gusty winds and abundant moisture (see the animation of MIRS Total Precipitable Water from this site, below) herald a weekend when it’s appropriate to pay attention to the weather because of the potential for rain and winds.

===== 28 August Update =====

Invest 99L developed into Tropical Depression 09 around 21 UTC on 28 August. A comparison of 1-minute GOES-14 Visible (0.63 µm) and Infrared Window (10.7 µm) images, above (also available as a large 94 Mbyte animated GIF), showed the tropical depression as it moved westward through the Florida Straits.

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