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]

Hurricane Rosa

September 28th, 2018 |
GOES-15 Ifrared Window (10.7 µm, left) and GOES-17

GOES-15 Infrared Window (10.7 µm, left) and GOES-17 “Clean” Infrared Window (10.3 µm, right) images [click to play animation | MP4]

* GOES-17 images shown here are preliminary and non-operational *

GOES-15 (GOES-West) Infrared Window (10.7 µm) and GOES-17 “Clean” Infrared Window (10.3 µm) images (above) showed Hurricane Rosa on the morning of 28 September 2018, after it had rapidly intensified to Category 4 intensity overnight (ADT | SATCON). Since GOES-17 was operating in a Mode 6 scan strategy, images were available every 10 minutes (compared to every 15 minutes from GOES-15, with 30-minute gaps during Full Disk scans every 3 hours). A notable warming trend was seen in the cloud tops surrounding the eye.

A toggle between DMSP-18 SSMIS Microwave (85 GHz) and GOES-15 Infrared Window (10.7 µm) from the CIMSS Tropical Cyclones site (below) showed the bands of heavier precipitation withing the central dense overcast surrounding the eye at 1333 UTC.

DMSP-18 SSMIS Microwave (85 GHz) and GOES-15 Infrared Window (10.7 µm) images [click to enlarge]

DMSP-18 SSMIS Microwave (85 GHz) and GOES-15 Infrared Window (10.7 µm) images [click to enlarge]

After sunrise, a comparison of GOES-15 Visible (0.63 µm) and GOES-17 “Red” Visible (0.64 µm) images (below) revealed an eye that was filled with low-level clouds.

GOES-15 Visible (0.63 µm, left) and GOES-17 "Red" Visible (0.64 µm, right) images [click to play animation | MP4]

GOES-15 Visible (0.63 µm, left) and GOES-17 “Red” Visible (0.64 µm, right) images [click to play animation | MP4]

An animation of the MIMIC-TC product (below) showed that Rosa went through an eyewall replacement cycle during the morning, and was downgraded to a Category 3 intensity at 15 UTC.

MIMIC-TC morphed microwave product, 0000-1545 UTC [click to enlarge]

MIMIC-TC morphed microwave product, 0000-1545 UTC [click to enlarge]

A Nebraska thunderstorm and a Wyoming wildfire, as viewed by GOES-15, GOES-17 and GOES-16

August 29th, 2018 |
Visible images from GOES-15 (0.63 µm, left), GOES-17 (0.64 µm, center) and GOES-16 (0.64 µm, right), with SPC storm reports plotted in red [click to play animation | MP4]

Visible images from GOES-15 (0.63 µm, left), GOES-17 (0.64 µm, center) and GOES-16 (0.64 µm, right), with SPC storm reports plotted in red [click to play animation | MP4]

* GOES-17 images shown here are preliminary and non-operational *

A comparison of Visible images from GOES-15 (GOES-West), GOES-17 and GOES-16 (GOES-East) (above) showed an isolated thunderstorm that developed in the Nebraska Panhandle late in the day on 29 August 2018. The storm produced hail (SPC storm reports), and also exhibited an Above Anvil Cirrus Plume. The images are displayed in the native projection of each satellite, with no re-mapping.

One other feature that was seen north of the thunderstorm was smoke which was being transported eastward from the Britania Mountain Fire in southeastern Wyoming. The smoke was more apparent on the GOES-17 and GOES-16 images as forward scattering increased toward sunset.

Shortwave Infrared imagery from the 3 satellites revealed important differences affecting fire detection: namely spatial resolution and viewing angle. The 3.9 µm detector on the GOES-15 Imager has a spatial resolution of 4 km (at satellite sub-point), compared to 2 km for the GOES-16/17 ABI. Given that the fire was burning in rugged mountain terrain, the view angle from each satellite had an impact on the resulting bire brightness temperature values. For example, the first indication of very hot (red-enhanced) pixels was at 1527 UTC from GOES-16/17, vs 1715 UTC from GOES-15; at the end of the day, the very hot fire pixels were no longer seen with GOES-15 after 2300 UTC, but continued to show up in GOES-17 imagery until 0042 UTC and in GOES-16 imagery until 0122 UTC.

Shortwave Infrared images from GOES-15 (3.9 µm, left), GOES-17 (3.9 µm, center) and GOES-16 (3.9 µm, right) [click to play animation | MP4]

Shortwave Infrared images from GOES-15 (3.9 µm, left), GOES-17 (3.9 µm, center) and GOES-16 (3.9 µm, right) [click to play animation | MP4]

Hail-producing thunderstorm in South Dakota

August 26th, 2018 |
Visible images from GOES-15 (0.63 µm, left), GOES-17 (0.64 µm, center) and GOES-16 (0.64 µm, right) [click to play animation | MP4]

Visible images from GOES-15 (0.63 µm, left), GOES-17 (0.64 µm, center) and GOES-16 (0.64 µm, right), with SPC storm reports plotted in yellow [click to play animation | MP4]

 * GOES-17 images shown here are preliminary and non-operational *

A comparison of Visible images from GOES-15 (GOES-West), GOES-17 and GOES-16 (GOES-East) (above) showed a severe thunderstorm that developed ahead of an advancing cold front (surface analyses) in central South Dakota late in the day on 26 August 2018. This storm produced hail as large as 4.0 inches in diameter (SPC storm reports), and also exhibited an above anvil cirrus plume (AACP) which is a signature often associated with severe thunderstorms.

The images are displayed in the native projection of each satellite, with no re-mapping. Note the important differences due to satellite scan strategy — the GOES-15 imager was initially performing a Full Disk scan, so imagery was only available every 30 minutes; the GOES-17 ABI was scanning at the standard “CONUS Sector” 5 minute interval; a GOES-16 ABI Mesoscale Domain Sector was providing images every 1 minute.