Water changes over the Gulf of Mexico from Ian

September 30th, 2022 |

Polar-Orbiting satellites flying over Florida viewed remarkable changes in water quality from before and after the passage of Hurricane Ian. Imagery from Suomi-NPP, for example, from 25 September and 30 September, toggled below (imagery derived from the VIIRS Today website), shows a large increase in turbidity in the Gulf (and over the Atlantic off the coast of eastern Florida) as well as discharge plumes from near Fort Myers and from points to the south.

VIIRS Today True-Color imagery from Suomi-NPP, 25 and 30 September 2022 (Click to enlarge)

True-color imagery from the Aqua MODIS instrument (below), taken from the MODIS Today website, also shows the dramatic changes (between 25 September and 30 September) in turbidity and water quality off the southwestern coast of Florida.

MODIS True-color imagery over the southeastern Gulf of Mexico before (25 September) and after (30 September) Hurricane Ian

Note: Hurricane Wilma caused a similar increase in turbidity (link).

Thanks to RIck DiMaio, Lewis University, for pointing this out!

01 October Update: One feature of interest was a small cyclonic eddy that developed along the end of a long curved filament of cyan-colored turbidity which was wrapping around the Florida Keys — shown in GOES-16 (GOES-East) True Color RGB images from the CSPP Geosphere site  (below).

GOES-16 True Color RGB images [click to play MP4 animation]

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]

Fiona intensifies to a Category 4 hurricane

September 21st, 2022 |

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animated GIF | 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 Fiona as it intensified to a Category 4 Hurricane just east of The Bahamas at 0900 UTC on 21 September 2022. The coldest cloud-top 10.35 µm infrared brightness temperatures were around -81ºC.

GOES-16 Infrared images with and without a overlay of GLM Flash Extent Density (below) did reveal isolated brief periods of lightning in the eyewall region of Fiona — but most of the lightning activity was associated with convection well east of the eye.

GOES-16 “Clean” Infrared Window (10.35 µm) images, with and without a overlay of GLM Flash Extent Density [click to play animated GIF | MP4]

The corresponding 1-minute GOES-16 Cloud Top Temperature and Cloud Top Height derived products are shown below — the coldest Cloud Top Temperature values were around -84ºC, while maximum Cloud Top Height values were around 58,000 feet.

GOES-16 Cloud Top Temperature and Cloud Top Height derived products [click to play animated GIF | MP4]

In a time-matched comparison of Infrared Window images from Suomi-NPP and GOES-16 at 0700 UTC (below), the coldest cloud-top infrared brightness temperatures were -86ºC and -81ºC, respectively. A slight northwestward parallax displacement was evident with the GOES-16 image.

Infrared Window images from Suomi-NPP (11.45 µm) and GOES-16 (10.35 µm) [click to enlarge]

===== 23 September Update =====

GOES-16 “Clean” Infrared Window (10.35 µm) images [click to play animated GIF | MP4]

As Fiona passed just to the northwest of Bermuda during the nighttime hours on 22-23 September, it was briefly downgraded to a Category 3 storm at 0600 UTC (before being again upgraded to Category 4 at 1200 UTC on the following morning) — but a wind gust to 81 knots (93 mph) was recorded at Bermuda Naval Air Station (station identifier TXKF) shortly before 10 UTC while that airport was temporarily closed to air traffic (Bermuda discussion). 1-minute GOES-16 Infrared images (above) showed Fiona during the 0000-1000 UTC period on 23 September.

A DMSP-17 SSMIS Microwave (85 GHz) image at 1053 UTC from the CIMSS Tropical Cyclones site (below) exhibited the eye and eyewall structure about an hour after the peak wind gust at Bermuda.

DMSP-17 SSMIS Microwave (85 GHz) image at 1053 UTC [click to enlarge]

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.