Subtropical Storm Debby

August 7th, 2018 |

“Red” Visible (0.64 µm) images from GOES-17 (left) and GOES-16 (right) [click to play animation | MP4]

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

“Red” Visible (0.64 µm) images from GOES-17 and GOES-16 (above) showed the circulation and convective banding associated with Subtropical Storm Debby in the Atlantic Ocean on 07 August 2018.

Deep-layer wind shear analysis from the CIMSS Tropical Cyclones site (below) indicated that Debby was in an environment of low shear.

GOES-16

GOES-16 “Red” Visible (0.64 µm) image, with deep-layer wind shear analysis [click to enlarge]

Hurricane John

August 7th, 2018 |

GOES-16

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

1-minute Mesoscale Domain Sector “Red” Visible (0.64 µm) images from the AOS site (above) showed the circulation of Hurricane John as it was intensifying from a Category 1 to a Category 2 storm off the west coast of Mexico on 07 August 2018. Several tropical overshooting tops could be seen in the animation.

GOES-16 Upper-level Water Vapor (6.2 µm), Mid-level Water Vapor (6.9 µm), Low-level Water Vapor (7.3 µm) and “Clean” Infrared Window (10.3 µm) images (below) revealed an interesting gravity wave that was propagating northward away from the center of John. This wave appeared to perturb the cloud tops — perhaps via vertical mixing — leading to a slight warming of the colder cloud-top infrared brightness temperatures as the wave passed. The appearance and behavior of this wave was very similar to another observed in Nebraska, Colorado and Kansas on 22 July.

GOES-16 Upper-level Water Vapor (6.2 µm, top left), Mid-level Water Vapor (6.9 µm, top right), Low-level Water Vapor (7.3 µm, bottom left) and

GOES-16 Upper-level Water Vapor (6.2 µm, top left), Mid-level Water Vapor (6.9 µm, top right), Low-level Water Vapor (7.3 µm, bottom left) and “Clean” Infrared Window (10.3 µm, bottom right) images [click to play MP4 animation]

Another item of interest was the circulation of weakening Tropical Storm Ileana being absorbed by the larger circulation of intensifying Hurricane John — this process was illustrated by 3-hourly 850 hPa relative vorticity analyses derived from GOES-15 (GOES-West) satellite winds (below). Similar results were seen at the 700 hPa, 500 hPa and 200 hPa pressure levels.

3-hourly analyses of 850 hPa relative vorticity [click to enlarge]

3-hourly analyses of 850 hPa relative vorticity [click to enlarge]

===== 08 August Update =====

Visible images from GOES-15, GOES-14, GOES-17 and GOES-16 [click to play animation | MP4]

Visible images from GOES-15, GOES-14, GOES-17 and GOES-16 [click to play animation | MP4]

GOES-15 (GOES-West), GOES-14, GOES-17 and GOES-16 (GOES-East) Visible images (above) showed 4 views of Hurricane John after it had diminished to a Category 1 storm on 08 August.

Note that the GOES-15 and GOES-14 Visible images do not appear as bright as those from GOES-17 and GOES-16 — prior to the GOES-R Series of satellites, the performance of visible detectors degraded over time, leading to imagery that appeared more dim as the Imager instrument aged. Visible detectors on the new ABI instrument benefit from on-orbit calibration to remedy this type of degradation.

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

Hurricane Hector

August 6th, 2018 |
NOAA-20 and Suomi NPP VIIRS Infrared Window (11.45 µm) images [click to enlarge]

NOAA-20 and Suomi NPP VIIRS Infrared Window (11.45 µm) images [click to enlarge]

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

A toggle between NOAA-20 and Suomi NPP VIIRS Infrared Window (11.45 µm) images (above; courtesy of William Straka, CIMSS) showed the well-defined eye of Hurricane Hector after it had reached Category 4 intensity on 06 August 2018 (advisories: EPAC | CPAC).

GOES-17 “Red” Visible (0.64 µm) images (below) revealed cloud-top gravity waves within the eyewall region of the storm, along with thin filaments of transverse banding in the northern semicircle farther from the eye.

GOES-17

GOES-17 “Red” Visible (0.64 µm) images [click to play animation | MP4]

GOES-15 (GOES-West) Visible (0.63 µm) and Infrared Window (10.7 µm) images (below) showed that eyewall cloud-top infrared brightness temperatures were in the -70 to -80ºC range (black to white enhancement).

GOES-15 Visible (0.63 µm, left) and Infrared Window (10.7 µm, right) images [click to play animation | MP4]

GOES-15 Visible (0.63 µm, left) and Infrared Window (10.7 µm, right) images [click to play animation | MP4]

A magnified view of GOES-15 Visible images (below) revealed mesovortices within the eye of Hector.

GOES-15 Visible (0.63 µm) images [click to play animation | MP4]

GOES-15 Visible (0.63 µm) images [click to play animation | MP4]

Metop ASCAT surface scatterometer winds (below) surrounding the eye were near 70 knots around 1930 UTC.

GOES-15 Infrared Window (10.7 µm) image and Metop ASCAT surface scatterometer winds [click to enlarge]

GOES-15 Infrared Window (10.7 µm) image and Metop ASCAT surface scatterometer winds [click to enlarge]

The MIMIC-TC morphed microwave product (below) showed that Hector underwent an eyewall replacement cycle early in the day on 05 August, and then maintained a well-defined eye as it subsequently strengthened to a high-end Category 4 intensity on 06 August (ADT | SATCON).

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

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

===== 07 August 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]

A nighttime NOAA-20 VIIRS Day/Night Band (0.7 µm) image (above) revealed the presence of mesospheric airglow waves (reference) propagating northwestward away from Category 4 Hurricane Hector on 07 August. Note that these high-altitude waves were not apparent on the corresponding Infrared Window (11.45 µm) image.

Hurricane Chris accelerates away from the United States

July 11th, 2018 |

GOES-16 ABI Band 2 (“Red Visible”) Visible (0.64 µm) Imagery, 1852-2117 UTC on 11 July 2018 (Click to animate)

Hurricane Chris is accelerating away from the United States (although it will likely pass very close to Cape Race, Newfoundland Canada). Visible Imagery (GOES-16 ABI Band 2, “Red Visible”, at 0.64 µm), above, from late afternoon on 11 July shows a well-developed storm with a pronounced eye.

Before Sunrise on 11 July 2018, both NOAA-20 and JAXA’s Global Change Observation Mission (GCOM) Satellite overflew the storm at slightly different times.  The VIIRS (Visible Infrared Imaging Radiometer Suite) instrument NOAA-20 samples in the visible and infrared part of the electromagnetic spectrum whereas the AMSR2 Instrument (Advanced Microwave Scanning Radiometer 2) on GCOM samples in the microwave.  Because microwave energy can penetrate clouds, it can be used to estimate rainfall, and the toggle below steps through the Infrared (11.45 µm) and Day Night Band Visible (0.70 µm) from VIIRS (at 0645 UTC) as well as the Convective Precipitation and Surface Rain rate from AMSR2 (at 0618 UTC). 

Lunar illumination is absent  in the Day Night band visible imagery, but Earth glow nevertheless illuminates the eye of the storm;  in addition, two lightning streaks are visible north and east of the center.  Surface Rain and Convective Rain rates show the heaviest rains near the storm center, as expected (NOAA-20 VIIRS and GCOM AMSR2 imagery courtesy William Straka, CIMSS).

VIIRS Infrared (11.45 µm) and Visible (0.70 µm) Day Night Band Visible Imagery, 0645 UTC on 11 July 2018, and GCOM AMSR2 Convective Precipitation and Surface Rain Rate estimates at 0618 UTC on 11 July (Click to enlarge)