Cyclone Batsirai reaches Category 4 intensity

February 3rd, 2022 |

EWS-G1 Infrared Window (10.7 µm) images [click to play animated GIF | MP4]

US Space Force EWS-G1 (formerly GOES-13) Infrared Window (10.7 µm) images (above) showed Cyclone Batsirai in the South Indian Ocean — just north of the island nations of Mauritius and Réunion — during the time period it was classified as a Category 4 intensity storm (00 UTC on 02 February to 15 UTC on 03 February 2022). Note that the small-diameter eye became notably larger by the end of the animation.

A DMSP-17 SSMIS Microwave (85 GHz) image from the CIMSS Tropical Cyclones site (below) displayed evidence that Batsirai had recently completed an eyewall replacement cycle (ERC), with the faint signature of the original small-diameter eye surrounded by the new large-diameter eye. This ERC process — seen in a 48-hour MIMIC-TC animation — initiated Batsirai’s gradual  decline in intensity.

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

EWS-G1 Visible (0.63 µm) images (below) showed that the small eye was initially cloud-filled, but eventually cleared during the day on 02 February — to reveal the possible existence of eye mesovortices (although such features are difficult to diagnose using 30-minute images) .

EWS-G1 Visible (0.63 µm) images [click to play animated GIF | MP4]

Typhoon Tiffany makes landfall in Australia

January 9th, 2022 |

JMA Himawari-8 Visible (0.64 µm) images [click to play animated GIF | MP4]

JMA Himawari-8 Visible (0.64 µm) images (above) showed Tropical Cyclone Tiffany as it made landfall along the eastern coast of the Cape York Peninsula in Queensland, Australia on 09 January 2022. [UPDATE: just prior to making landfall around 0130 UTC on 10 January, Tiffany intensified to a Category 1 typhoon (JTWC discussion)].

A longer animation of Himawari-8 Infrared (10.4 µm) images (below) revealed pulses of overshooting tops which exhibited cloud-top infrared brightness temperatures in the -90 to -95°C range.

JMA Himawari-8 Infrared (10.4 µm) images [click to play animated GIF | MP4]

A stepped sequence of zoomed-in Suomi-NPP VIIRS Infrared (11.45 µm) images at 1517 UTC, viewed using RealEarth (below) showed a few red pixels — which highlighted cloud-top infrared brightness temperatures of -100°C or colder.   

Suomi-NPP VIIRS Infrared (11.45 µm) image at 1517 UTC [click to enlarge]

DMSP-16 SSMIS Microwave (85 GHz) imagery from the CIMSS Tropical Cyclones site (below) showed convection wrapping around a very small eye feature at 1905 UTC.

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

Himawari-8 Infrared images with contours of deep-layer wind shear (below) indicated that Tiffany was moving through an environment of light to moderate shear. 

JMA Himawari-8 Infrared images, with contours of deep-layer wind shear [click to enlarge]

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]

===== 30 September Update =====

GOES-16 “Red” Visible (0.64 µm) images (credit: Tim Schmit, NOAA/NESDIS/ASPB) [click to play animation | MP4]

Sam was still a Category 4 hurricane on 30 September — and GOES-16 Visible images (above) showed that Sam exhibited a relatively compact eye, with hints of mesovortices within the eye.      

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]