1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed Category 1 Hurricane Lee as it moved northward between Buoy 41048 and Bermuda (station identifier TXKF) on 14 September 2023. As shown in the plot below, the highest wind gust at Buoy 41048 was 41.0 m/s (79.7 knots, or 97.7 mph) at 2010 UTC (data transmission from the buoy ceased after 2310 UTC). The strong winds from Lee produced wave heights to 32 ft — and produced upwelling that cooled the water temperature several degrees.

In 1-minute GOES-16 “Clean” Infrared Window (10.3 µm) images (below), the coldest cloud tops exhibited infrared brightness temperatures around -80ºC (brighter shades of white embedded within darker black regions).

Analyses of deep-layer wind shear from the CIMSS Tropical Cyclones site (below) showed that Lee was moving into an environment of increasingly unfavorable shear as it gained latitude — which was acting to suppress the development of deep convection and the maintenance of a well-defined eye.

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Daytime EUMETSAT Meteosat-10 High Resolution Visible (0.8 µm) images (above) showed Storm Daniel as it developed into a Medicane over the southern Mediterranean Sea on 09 September (with convective bands wrapping around the storm center), then moved inland across northeastern Libya on 10 September 2023.

Hourly MIMIC Total Precipitable Water images from 09 to11 September (below) displayed bands of TPW in the 2.0-3.0 inch range (darker shades of red) wrapping around the center of Storm Daniel as it moved inland — causing heavy rainfall and extensive flooding (see this Climate Connections blog post for more details). Ship reports indicated that water temperatures in the central Mediterranean Sea — where Storm Daniel had meandered for a few days before approaching Libya — were in the 77-79ºF range.

As the center of Storm Daniel was approaching the Libya/Egypt border on 11 September, a MIMIC Total Precipitable Water image with an overlay of Metop-C ASCAT surface scatterometer winds at 0800 UTC showed a long fetch of winds in the 25-33 knot range (red barbs) approaching the coast of Libya — then at 1100 UTC, a ship report within the same region of that ASCAT fetch reported a wind speed of 40 knots (below).

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5-minute PACUS Sector GOES-18 (GOES-West) Shortwave Infrared (3.9 µm) and SO2 RGB images (above) showed the thermal anomaly (heat signature) and a plume of SO2 (brighter shades of cyan) for 1.5 hours following the onset of an eruption of Kilauea on the Big Island of Hawai`i late in the day on 10 September 2023.

The Kilauea eruption began at 0115 UTC on 11 September (3:15 PM HST on 10 September) — and about 15 minutes later, the GOES-18 3.9 µm Shortwave Infrared brightness temperature sensed at the volcano summit reached 137.88ºC (below) — which is the saturation temperature of GOES-18 ABI Band 7 detectors.

GOES-18 True Color RGB + Nighttime Microphysics RGB images from the CSPP GeoSphere site (below) displayed the volcanic plume as it moved southwest; the Kilauea summit’s thermal anomaly appeared as darker blue pixels in the final (0411 UTC) Nighttime Microphysics RGB image of the animation.

A longer animation of larger-scale GOES-18 Shortwave Infrared and SO2 RGB images (below) revealed the continued southwest transport of the SO2 plume for about 10 hours post-eruption. The GOES-18 Shortwave Infrared brightness temperature sensed at the Kilauea summit remained at the aforementioned 137.88ºC saturation temperature for nearly the entire time period shown.

A Suomi-NPP VIIRS Day/Night Band (0.7 µm) image valid at 1247 UTC or 2:47 AM HST (below) showed a large bright signature over the Kilauea area, due to the intense glow of the volcanic lava flows. The VIIRS instrument was scanning from NW to SE; note the dark streak extending SE of the bright Kilauea glow, which was a hysteresis effect due to the sensor becoming saturated by the intense volcanic signature.

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1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) showed Lee as it intensified to become a Category 1 Hurricane in the Central Atlantic Ocean on 06 September 2023. The coldest cloud-top infrared brightness temperatures were around -90C (brighter white pixels embedded within darker black areas). 

Lee had been moving across warm water — and was traversing an environment having low deep-layer wind shear (below) — factors which were favorable for intensification. Water temperature and wind shear imagery was sourced from the CIMSS Tropical Cyclones site.

Meanwhile, in the East Pacific Hurricane Jova rapidly intensified to a Category 4 storm by 2100 UTC on 06 September, exhibiting a pinhole eye as seen in GOES-18 (GOES-West) Visible and Infrared imagery (below).

Similar to Lee, Jova had been moving across warm water — and was traversing an environment having low deep-layer wind shear (below) — factors which were favorable for intensification.

Jova was later upgraded to Category 5 intensity at 0900 UTC (Infrared images: animated GIF | MP4). 

===== 07 September Update =====

At 0300 UTC on 08 September, Hurricane Lee was upgraded to a Category 5 storm (the first Category 5 of the 2023 Atlantic Basin season). 6 hours of 1-minute GOES-16 Infrared images leading up to that time are shown above — and the 0100 UTC Infrared image with an overlay of Metop-C ASCAT surface scatterometer winds is shown below. Note: 25-km resolution ASCAT winds are available in AWIPS, which indicated a maximum speed of 75 knots — however, the Ultra-High Resolution (UHR) ASCAT wind product at that time (source) had a maximum speed of 136 knots.

Even though deep-layer wind shear was gradually increasing in its vicinity, Lee reached Category 5 intensity as it began to move across water with increasing values of Ocean Heat Content and Sea Surface Temperature (below).

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