Hurricane Sam reaches Category 4 intensity

September 25th, 2021 |

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

1–minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (above) showed Hurricane Sam as it intensified from a Category 3 to a Category 4 storm (ADT | SATCON) in the central Atlantic Ocean on 25 September 2021. The eye became cloud-filled during the middle portion of the day, but Visible images revealed the presence of mesovortices within the eye both early and late in the day.

A DMSP-16 SSMIS Microwave (85 GHz) image at 1918 UTC from the CIMSS Tropical Cyclones site (below) displayed a fully closed eyewall, with several spiral bands wrapping inward toward the storm center.

DMSP-16 SSMIS Microwave (85 GHz) image at 1918 UTC [click to enlarge]

GOES-16 Infrared images with an overlay of deep-layer wind shear at 2200 UTC (below) indicated that Sam was in an environment of low shear — which favored intensification as the hurricane moved across relatively warm water (SST | OHC).

GOES-16 Infrared images, with an overlay of deep-layer wind shear at 2200 UTC [click to enlarge]

During the following nighttime hours, ample illumination from the Moon — which was in the Waning Gibbous phase, at 81% of Full — provided a “visible image at night” using the Suomi NPP VIIRS Day/Night Band (0.7 µm) (below).

Suomi NPP VIIRS Day/Night Band (0.7 µm) image [click to enlarge]

===== 26 September Update =====

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4

On the following day, Sam exhibited a similar appearance on 1-minute GOES-16 Infrared and Visible images (above), with a small 7-15 mile diameter eye (containing mesovortices, as seen in Visible imagery). Both Infrared and Visible images revealed repeated pulses of gravity waves propagating away from the storm center. Sam’s intensity peaked at 135 knots late in the day (NHC advisory).

1-minute GOES-16 Visible images with plots of corresponding GLM Flashes (below) showed that Sam exhibited an Enveloped Eyewall Lightning signature (reference).

1-minute GOES-16 “Red” Visible (0.64 µm) images, with 1-minute GLM Flashes plotted in red [click to play animation | MP4]

Hurricane Ida develops an eye over the Gulf of Mexico, as intensification continues until landfall

August 28th, 2021 |

GOES-16 “Clean” Infrared Window (10.35 µm) and “Red” Visible (0.64 µm) images [click to play animation | MP4]

1-–minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (above)  showed that Hurricane Ida gradually developed an eye, as the Category 1 storm intensified to Category 2 by 1800 UTC on 28 August 2021.

DMSP-17 SSMIS Microwave (85 GHz) image at 1235 UTC [click to enlarge]

Microwave (85 GHz) images from DMSP-17 (above) and DMSP-16 (below) — from the CIMSS Tropical Cyclones site — provided 2 views of the eye and eyewall structure at 1235 UTC and 2205 UTC, respectively.

DMSP-16 SSMIS Microwave (85 GHz) image at 2205 UTC [click to enlarge]

Ida was moving across very warm water (SST | OHC) — and was forecast to pass over an area of very high Ocean Heat Content associated with a warm eddy that was shed from the Gulf of Mexico’s Loop Current. Ida was also moving through an environment of low wind shear (below), which favored further intensification as it continued to approach the Louisiana coast.

GOES-16 Infrared images, with contours of deep-layer wind shear at 20 UTC [click to enlarge]

===== 29 August Update =====

GOES-16 “Clean” Infrared Window (10.35 µm) and “Red” Visible (0.64 µm) images [click to play animation | MP4]

Ida reached Category 4 intensity at 0600 UTC on 29 August; 1-minute GOES-16 Infrared and Visible images (above) depicted a well-defined eye during the hours leading up to the hurricane making landfall along the coast of Louisiana at 1655 UTC.

GMI Microwave imagery at 1510 UTC (below) portrayed a closed eye, with the heaviest precipitation located within the eastern semicircle of Ida.

GMI Microwave (85 GHz) image at 1510 UTC [click to enlarge]

A closer view of 1-minute GOES-16 Visible images (below) revealed the presence of low-level mesovortices within the eye of Ida — a feature often observed with high-intensity tropical cyclones. The mesovortices persisted as the hurricane moved inland, as Ida was slow to weaken. Just east of the eye, Galliano (KGAO) reported wind gusts as high as 85 knots (plot | text), before observations ceased after 21 UTC (presumably due to power outages).  A separate mesonet station at Galliano recorded a wind gust of 122 mph (NWS New Orleans tweet | plot); a ship reported a wind gust of 194 knots (tweet).

 

GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

The MIMIC Total Precipitable Water product (below) showed that Ida was transporting rich tropical moisture northward across the central Gulf of Mexico coast of the US, raising a threat for flooding rainfall. 

MIMIC Total Precipitable Water product, 28-29 August [click to enlarge]

Elsa briefly regains hurricane intensity before making landfall along the Florida coast

July 6th, 2021 |

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

Late in the day on 06 July 2021, Tropical Storm Elsa regained hurricane intensity as of 0000 UTC, just off the west coast of Florida. 1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (above) showed the tropical cyclone during the 1500 UTC to 0000 UTC time period. In the morning, cloud-top infrared brightness temperatures of -80ºC or colder were seen (violet pixels), but during most of the day they were in the -70 to -79ºC range. While Elsa had been moving over water with Sea Surface Temperature values around 28ºC, the Ocean Heat Content of those waters was relatively low.

For a few hours the low-level circulation of Elsa remained exposed from its deep convection to the northeast — and GOES-16 Visible images with an overlay of deep-layer shear at 1800 UTC, from the CIMSS Tropical Cyclones site (below), showed that this was due to westerly shear values around 25-30 knots over the area.

GOES-16 “Red” Visible (0.64 µm) images, with an overlay of deep-layer wind shear at 1800 UTC [click to enlarge]

GOES-16 “Red” Visible (0.64 µm) images, with an overlay of deep-layer wind shear at 1800 UTC [click to enlarge]

The center of Elsa moved just to the east of Buoy 42023 — a plot of wind speed/gust and pressure is shown below.

Plot of wind speed/gusts and pressure at Buoy 42023

Plot of wind speed/gusts and pressure at Buoy 42023

A DMSP-15 Microwave (85 GHz) Microwave image at 2155 UTC (below) indicated that Elsa had nearly completed the formation  of a closed eyewall at that time.

DMSP-15 Microwave (85 GHz) Microwave image at 2155 UTC [click to enlarge]

DMSP-15 Microwave (85 GHz) Microwave image at 2155 UTC [click to enlarge]

GOES-16 Infrared  / Water Vapor Difference images (below) revealed pockets of stronger overshooting tops near the center of deep convection during the hours leading up to Elsa reaching hurricane intensity.

GOES-16 Infrared / Water Vapor Difference images [click to enlarge]

GOES-16 Infrared  / Water Vapor Difference images [click to enlarge]

===== 07 July Update =====

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

After once again weakening to Tropical Storm intensity at 0600 UTC, Elsa eventually made landfall along the coast of Florida around 1500 UTC on 07 July, as seen in 1-minute GOES-16 Visible and Infrared images (above) — inland impacts included an EF0 tornado, wind gusts to 71 mph and rainfall exceeding 11 inches (NWS Public Information Statements).

At 1223 UTC, a DMSP-17 SSMIS Microwave image (below) indicated that a closed eyewall was not present with Elsa at that time.

DMSP-17 SSMIS Microwave (85 GHz) image [click to enlarge]

DMSP-17 SSMIS Microwave (85 GHz) image [click to enlarge]

Cyclone Tauktae in the Arabian Sea

May 16th, 2021 |

US Space Force EWS-G1 Infrared (10.7 µm) images [click to play animation | MP4]

US Space Force EWS-G1 Infrared (10.7 µm) images [click to play animation | MP4]

US Space Force EWS-G1 Infrared (10.7 µm) images (above) showed Cyclone Tauktae in the Arabian Sea (just off the west coast of India) as it intensified from a Category 1 to a Category 3 storm on 16 May 2021.

A DMSP-18 SSMIS Microwave (85 GHz) image from the CIMSS Tropical Cyclones site (below) revealed a fully enclosed eye at 1142 UTC, shortly before Tauktae reached Category 3 intensity at 12 UTC.

DMSP-18 SSMIS Microwave (85 GHz) image at 1142 UTC [click to enlarge]

DMSP-18 SSMIS Microwave (85 GHz) image at 1142 UTC [click to enlarge]

===== 17 May Update =====

US Space Force EWS-G1 Infrared (10.7 µm) images [click to play animation | MP4]

US Space Force EWS-G1 Infrared (10.7 µm) images [click to play animation | MP4]

EWS-G1 Infrared images (above) showed Cyclone Tauktae making landfall along the coast of India around 1745 UTC on 17 May, with a Category 3 intensity (ADT | SATCON).