Hurricane Walaka

October 1st, 2018 |

GOES-15 Infrared Window (10.7 µm) images [click to play animation | MP4]

GOES-15 Infrared Window (10.7 µm) images [click to play animation | MP4]

GOES-15 (GOES-West) Infrared Window (10.7 µm) images (above) showed the formation of a well-defined eye of Hurricane Walaka during a period of rapid intensification (ADT | SATCON) from 0000-2330 UTC on 01 October 2018; Walaka was classified a Category 5 hurricane as of the 02 October 00 UTC advisory. Walaka was moving over very warm water with Sea Surface Temperatures of 30ºC.

A 1536 UTC DMSP-16 SSMIS Microwave (85 GHz) image from the CIMSS Tropical Cyclones site (below) revealed a small eye (reported to be 20 nautical miles in diameter at 21 UTC).

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

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

A side-by-side comparison of JMA Himawari-8 and GOES-15 Infrared Window images (below) showed Walaka from 2 different satellite perspectives — the superior spatial resolution of Himawari-8 (2 km, vs 4 km for GOES-15) was offset by the much larger viewing angle. Cloud-top infrared brightness temperatures were -80ºC and colder (shades of violet) from both satellites early in the animation, but warmed somewhat into the -70 to -75ºC range by 00 UTC on 02 October.

Infrared Window images from Himawari-8 (10.3 µm, left) and GOES-15 (10.7 µm, right) [click to play animation | MP4]

Infrared Window images from Himawari-8 (10.3 µm, left) and GOES-15 (10.7 µm, right) [click to play animation | MP4]

===== 02 October Update =====

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

Walaka remained classified as a Category 5 hurricane until the 15 UTC advisory on 02 October, when it was assigned Category 4 status after some weakening as a result of an overnight eyewall replacement cycle. A toggle between NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images (above; courtesy of William Straka, CIMSS) showed the storm at 1240 UTC or 2:40 am local time.

GOES-15 Infrared Window (10.7 µm) images (below) showed the northward motion of Waleka. Given that the storm was forecast to pass very close to Johnston Atoll, the US Coast Guard was dispatched to evacuate personnel on Johnston Island.

GOES-15 Infrared Window (10.7 µm) images; the white circle shows the location of Johnston Atoll [click to play animation | MP4]

GOES-15 Infrared Window (10.7 µm) images; the white circle shows the location of Johnston Atoll [click to play animation | MP4]

The MIMIC-TC product (below) showed the eyewall replacement cycle during the 0000-1445 UTC period.

MIMIC-TC morphed microwave product [click to play animation]

MIMIC-TC morphed microwave product [click to play animation]

Around 1830 UTC, a toggle between GOES-15 Infrared (10.7 µm) and GPM GMI Microwave (85 GHz) images (below) showed a small eye, with evidence of a larger outer eyewall suggesting that another eyewall replacement cycle was taking place.

GOES-15 Infrared Window (10.7 µm) and GPM GMI Microwave (85 GHz) images [click to enlarge]

GOES-15 Infrared Window (10.7 µm) and GPM GMI Microwave (85 GHz) images [click to enlarge]

West Pacific Super Typhoon Trami

September 24th, 2018 |

Himawari-8 Infrared Window (10.4 µm) images [click to play animation | MP4]

Himawari-8 “Clean” Infrared Window (10.4 µm) images [click to play animation | MP4]

Himawari-8 “Clean” Infrared Window (10.4 µm) images (above) showed Typhoon Trami at Category 4 intensity during the 23-24 September 2018 period. The typhoon was going through an eyewall replacement cycle during this time — as seen on the MIMIC-TC product — which halted the period of rapid intensification that began early on 23 September (ADT | SATCON). Note the significant trochoidal motion (wobble) of the storm during the first half of the animation.

With the arrival of daylight late on 24 September UTC (25 September local time), the satellite presentation of then Category 5 Trami was quite striking, with surface mesovorticies within the large eye seen on both Visible and Infrared rapid-scan (2.5-minute interval) images (below). The deep-layer mean steering flow was also very light, allowing the forward motion of Trami to slow considerably.

Himawari-8

Himawari-8 “Red” Visible (0.64 µm, left) and “Clean” Infrared Window (10.4 µm, right) images [click to play animation | MP4]

Trami was in an environment characterized by low values of deep-layer wind shear, as shown in an animation of Himawari-8 Infrared Window (10.4 µm) images from the CIMSS Tropical Ctclones site (below).

Himawari-8 Infrared Window (10.4 µm) images, with deep-layer wind shear analysis at 00 UTC [click to enlarge]

Himawari-8 Infrared Window (10.4 µm) images, with deep-layer wind shear analysis at 00 UTC [click to enlarge]

After nightfall on 25 September, and overpass of NOAA-20 provided VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images of Trami at 1634 UTC (below; courtesy of William Straka, CIMSS). Due to the very slow motion of the typhoon, strong winds had induced upwelling of cooler water from below the ocean surface — which in turn brought a gradual weakening of the storm to a Category 4 intensity. Ample illumination from a Full Moon demonstrated the “visible image at night” capability of the Day/Night Band.

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]


Though the eye had become more cloud-filled, distinct surface mesovortices were still present — captured in stunning detail by an astronaut on the International Space Station:


Super Typhoon Mangkhut makes landfall in the Philippines

September 14th, 2018 |

Himawari-8 Infrared Window (10.4 µm) images [click to play MP4 animation]

Himawari-8 Infrared Window (10.4 µm) images [click to play MP4 animation | Animated GIF]

Himawari-8 Infrared Window (10.4 µm) images (above) showed Super Typhoon Mangkhut making landfall as a Category 5 intensity storm over the far northern portion of Luzon in the Philippines just after 17 UTC on 14 September 2018 (1 am local time on 15 September). The eye quickly deteriorated and became cloud-filled after moving inland.

The MIMIC-TC morphed microwave product (below) indicated that Mangkhut was in the process of completing an eyewall replacement cycle shortly before making landfall.

westernMIMIC-TC morphed microwave product [click to enlarge]Mangkhut moved over waters of the western Philippine Sea having high values of Ocean Heat Content and Sea Surface Temperature during the final day preceding landfall (below).

Ocean Heat Content and Sea Surface Temperature data along the path of Mangkhut [click to enlarge]

Super Typhoon Jebi

August 31st, 2018 |

Himawari-8

Himawari-8 “Clean” Infrared Window (10.4 µm) images [click to play MP4 animation]

West Pacific Typhoon Jebi underwent a period of very rapid intensification on 30 August 2018 (ADT | SATCON), reaching Category 5 Super Typhoon intensity. Himawari-8 rapid-scan (2.5 minute interval) “Clean” Infrared Window (10.4 µm) images (above) showed that Jebi began to exhibit an annular appearance with a nearly symmetric eyewall as it moved through the Northern Mariana Islands (north of Guam). The eye passed just south of the uninhabited volcanic island of Pagan around 16 UTC on 30 August.

Himawari-8 “Red” Visible images (below) revealed mesovortices within the eye of Jebi.

Himawari-8

Himawari-8 “Red” Visible (0.64 µm) images [click to play MP4 animation]

Toggles between VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP (below) showed more detailed views of (1) the well defined eye, (2) surface mesovortices within the eye, and (3) storm-top gravity waves that were propagating away from the eyewall region. With the Moon in the Waning Gibbous phase (at 77% of Full), ample illumination was available to provide detailed “visible images at night” using the VIIRS DNB.

NOAA-20 Day/Night Band (0.7 µm) and infrared Window (11.45 µm) images at 1602 UTC [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm) and infrared Window (11.45 µm) images at 1602 UTC [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and infrared Window (11.45 µm) images at 1652 UTC [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and infrared Window (11.45 µm) images at 1652 UTC [click to enlarge]

Convective Rain Rate and Surface Rain Rate products derived from GCOM-W1 AMSR2 data (below) showed the heavy rainfall occurring within the eyewall region and a primary feeder band to the west. VIIRS and AMSR2 images courtesy of William Straka, CIMSS.

GCOM-W2 AMSR2 Convective Rain Rate and Surface Rain Rate products [click to enlarge]

GCOM-W2 AMSR2 Convective Rain Rate and Surface Rain Rate products [click to enlarge]

As Jebi tracked west-northwestward across the West Pacific, products from the CIMSS Tropical Cyclones site showed that it had been moving over waters having high values of Sea Surface Temperature and Ocean Heat Content (below).

Track of Jebi, with Sea Surface Temperature and Ocean Heat Content [click to enlarge]

Track of Jebi, with Sea Surface Temperature and Ocean Heat Content [click to enlarge]

A 48-hour animation of the MIMIC-TC product (below) showed the evolution of the Jebi from 29-31 August. The storm was completing an eyewall replacement cycle near the end of the animation, with the eye becoming distinctly larger.

MIMIC-TC product, 29-31 August

In a comparison of DMSP-16 SSMIS Microwave (85 GHz) and Himawari-8 Infrared Window (10.4 µm) images at 1900 UTC (below), the Microwave data helped to better visualize the structure of the large eyewall in addition to a long, narrow feeder band wrapping inward toward the eye.

DMSP-16 SSMIS Microwave (85 GHz) and Himawari-8 Infrared Window (10.4 µm) images [click to enlarge]

DMSP-16 SSMIS Microwave (85 GHz) and Himawari-8 Infrared Window (10.4 µm) images [click to enlarge]