30-second imagery of Hurricane Ian

September 27th, 2022 |

GOES-16 “Red” Visible (0.64 µm) images, with and without an overlay of GLM Flash Extent Density [click to play animated GIF | MP4]

Overlapping 1-minute Mesoscale Domain Sectors provided 30-second interval GOES-16 (GOES-East) “Red” Visible (0.64 µm) images, with and without an overlay of GLM Flash Extent Density (above) — which showed the well-defined eye of Category 3 Hurricane Ian as it moved away from the northern coast of Cuba on 27 September 2022. Near-continuous lightning activity was seen in the eyewall region of Ian during the 7-hour period from 1300-2000 UTC.

The corresponding 30-second GOES-16 “Clean” Infrared Window (10.3 µm) images (below) showed cloud-top infrared brightness temperatures as cold as -83ºC.

GOES-16 “Clean” Infrared Window (10.3 µm) images [click to play animated GIF | MP4]

In a toggle between NOAA-20 VIIRS Infrared Window (11.45 µm) and Visible (0.64 µm) images valid at 1847 UTC (below), the coldest cloud-top infrared brightness temperatures at that time were around -83ºC (darker shades of purple),

NOAA-20 VIIRS Infrared Window (11.45 µm) and Visible (0.64 µm) images, valid at 1847 UTC [click to enlarge]

Low-Earth Orbit satellite views of Ian as it formed, and comparisons to Geostationary imagery

September 26th, 2022 |

Polar-orbiting satellites have microwave detectors that give important information about the low-level structure of an evolving tropical cyclone. If high clouds are omnipresent, it can be difficult for an analyst to diagnose storm strength with accuracy. Microwave energy penetrates clouds, however, and low-earth orbit (LEO) observations of microwave frequencies can reveal much about a storm’s structure.


24 September: South of Haiti


Consider the imagery below, showing the cluster of thunderstorms associated with then-Tropical Storm Ian south of Haiti. Based on just the still infrared image (admittedly, this would be easier with an animating image!), where would you place the center? Microwave data — 36.5 GHz and 89 GHz data from GCOM-W1 (from the AOML Direct Broadcast site here) suggest a center in between the top large regions of cold cloud tops in the infrared imagery (the 0900 UTC discussion has a center near 14.7oN, 73.5oW). MIMIC Tropical Cyclone imagery (from this link) for Ian on 24 September (here) can help a user determine where the center is as well.

GOES-16 ABI Band 13 Infrared (10.3 µm) imagery, and GCOM-W1 AMSR-2 Microwave imagery (36.5 and 89.0 GHz), 0620 UTC on 24 September 2022 (Click to enlarge)

25 September: Southwest of Jamaica


One day later, imagery from ABI and GCOM-W1 show a better-defined tropical system at 0700 UTC (Here’s the NHC discussion from 0900 UTC, at which time the center was at 14.9oN, 78.8oW). Even from the still ABI image, one could infer a center based on the spiral bands. Microwave information (36.5 and 89.0 GHz) certainly will increase confidence. Indeed, the low-level microwave signal (i.e., from 36.5 GHz) suggests a center very near the 0900 UTC location. The MIMIC TC animation from 0000 UTC 25 September – 0000 UTC 26 September (link) is showing a stronger signal for a center as well.

GOES-16 ABI Band 13 Infrared (10.3 µm) imagery, and GCOM-W1 AMSR-2 Microwave imagery (36.5 and 89.0 GHz), 0700 UTC on 25 September 2022 (Click to enlarge)

26 September: south of Western Cuba


NOAA-20 ATMS imagery (88 GHz) over Ian, 0606 and 0746 UTC on 26 September 2022 (Click to enlarge)

The LEO coverage on 26 September is a great example of why multiple LEO satellites are vital. The early-morning coverage from NOAA-20 is shown above; the gap between the two satellite passes is in an unfortunate spot for monitoring this tropical cyclone! However, Suomi NPP orbits overlap NOAA-20, and on this day Suomi NPP overflew the center of the storm, as shown below. The cadence was NOAA-20 to the east, 45 minutes later Suomi-NPP over the center, 45 minutes later NOAA-20 to the west. Here is an animation of the three passes. Polar monitoring capabilities will receive a big boost when JPSS-2 (slated to become NOAA-21) is launched (tentatively scheduled for 1 November 2022).

Suomi-NPP ATMS Microwave Imagery, 88.0 GHz, 0656 UTC on 26 September 2022 (Click to enlarge)

Ian at 0700 UTC on 26 September, below, is on the cusp of being upgraded to a hurricane (0600 UTC intermediate advisory), and an animation of the Band 13 imagery (a still image is shown below for comparison to the ATMS imagery) shows the center of rotation even though an eye is not present in the infrared (although one in the microwave).

GOES-16 ABI Band 13 Infrared (10.3 µm) imagery, and Suomi-NPP ATMS Microwave imagery (88.0 GHz), ca. 0700 UTC on 26 September 2022 (Click to enlarge)

ATMS and AMSR2 imagery as shown above are created from passive microwave sensors; that is, the sensors are detecting the microwave imagery emitted by the ocean, land, clouds and atmosphere. Other LEO satellites emit energy (“ping”) in the microwave and listen for a return signal. This leads to both scatterometry (not shown, as from the Advanced Scatterometer — ASCAT — instrument on Metop-B and Metop-C — available here) and Synthetic Aperture Radar imagery (available here for tropical cyclones), and shown below. The image below shows infrared and GLM imagery for then-newly upgraded Hurricane Ian (link). Although a distinct eye is still not present in the infrared imagery, SAR wind data defines an obvious region of reduced winds. Maximum SAR winds in this image are just above 70 knots.

GOES-East ABI Band 13 Infrared imagery (10.3 µm), GLM 1-minute aggregate Total Optical Energy (TOE) and RSAT-2 SAR Winds over Ian, 1110 UTC on 26 September 2022 (Click to enlarge)

VIIRS and ATMS imagery of Hurricane Ian on 27 September is here. For the latest information on Hurricane Ian, please refer to the National Hurricane Center. People in southern (and especially southwestern) Florida should be paying very close attention to this storm.

Parallax shifts in VIIRS views of Fiona

September 19th, 2022 |

VIIRS Day Night Band visible (0.7 µm) imagery from Suomi NPP (0549 UTC) and NOAA-20 (0638 UTC) on 19 September 2022 (Click to enlarge)

Suomi NPP and NOAA-20 both overflew Hurricane Fiona (NPP flew overhead to the east, NOAA-20 flew overhead to the west) in the early morning of 19 September 2022, as shown above in imagery created at AOML (The Atlantic Oceanagraphic and Meteorological Laboratory) and displayed at the Direct Broadcast site there. The images appear to show an eastward motion of the eye — but GOES-16 animations, below, show a persistent west-northwest motion (landfall occurred in the Dominican Republic around 0730 UTC).

GOES-16 Band 13 Infrared Imagery (10.3 µm), 0301 – 0946 UTC on 19 September 2022 (Click to enlarge)

The apparent eastward motion of the eye also shows up in the infrared imagey, which rules out artifacts related to shadowing.

VIIRS M15 (10.8 µm) infrared imagery from Suomi-NPP (0549 UTC) and NOAA-20 (0636 UTC) on 19 September 2022 (Click to enlarge)
Suomi NPP Day Night Band imagery and GOES-16 Band 13 Infrared imagery, ca. 0556 UTC on 19 September 2022 (Click to enlarge)

This might be an example of a Parallax shift in VIIRS imagery causing a shift in a feature. NOAA-20’s nadir was over Jamaica, considerably to the east of the Mona Passage where Fiona’s eye was developing. A parallax error may be responsible, because satellite navigation will place the tall clouds farther from the sub-satellite point than observed.


The full-resolution Day Night band imagery from Suomi NPP, and from NOAA-20 (both available from the CIMSS ftp site here and here) show strong convection starting ca. 0530 UTC and continuing through ~0630 UTC near the eye.

Unusually low ice concentration in the Beaufort Sea and Chukchi Sea

September 13th, 2022 |

Suomi-NPP VIIRS Visible images [click to play animated GIF | MP4]

A sequence of Suomi-NPP VIIRS Visible images (above) showed a large area of ice-free water in the western Beaufort Sea and eastern Chukchi Sea north of Alaska — with limited sea ice concentration as far north as 80º N latitude — on 13 September 2022.  

False Color RGB images from NOAA-20 and Suomi-NPP, viewed using RealEarth (below) provided another depiction of the large ice-free region the Beaufort Sea (as well as adjacent portions of the Chukchi Sea).

False Color RGB images from NOAA-20 and Suomi-NPP [click to play animated GIF]

 Sea Ice Concentration (based on the NOAA Enterprise Algorithm) at 0000 UTC on 13 September (below) also showed limited ice coverage and concentration extending past 80º N latitude.

Sea Ice Concentration at 0000 UTC on 13 September [click to enlarge]

According to Rick Thoman (University of Alaska, Fairbanks), Beaufort Sea ice extent was the 9th lowest on record for this date: