Hurricane Ian makes landfall in Florida

September 29th, 2022 |

GOES-16 “Clean” Infrared Window (10.3 µm) and “Red” Visible (0.64 µm) images [click to play animated GIF | MP4]

Overlapping 1-minute Mesoscale Domain Sectors provided 30-second interval GOES-16 (GOES-East) “Clean” Infrared Window (10.3 µm) and “Red” Visible (0.64 µm) images (above) during a 7-hour period that included the landfall of Hurricane Ian along the southwest coast of Florida at 1905 UTC (Visible | Infrared) on 28 September 2022. Moving across very warm water (where buoy Sea Surface Temperature values were 82-85ºF), Ian intensified to a Category 4 hurricane at 1200 UTC, and further intensified as it neared the Florida coast to just below Category 5 strength (rated at 135 knot sustained winds). As Ian moved inland, peak wind gusts were as high as 140 mph, and heavy rainfall exceeded 10 inches within a 4-hour period (WPC Storm Summary). These strong winds quickly resulted in power outages to 96-99% of customers in DeSoto, Charlotte and Lee Counties by 2244 UTC — note the disappearance of surface plot data in the GOES-16 imagery after 20 UTC at sites such as Venice (peak gust 90 knots / 104 mph), Punta Gorda (peak gust 117 knots / 135mph) and Fort Meyers (peak gust 87 knots / 100 mph).

30-second GOES-16 Visible images with time-matched plots of GLM Flashes (below) indicated that lightning activity within the eyewall decreased as the eye of Ian approached the coast.

GOES-16 “Red” Visible (0.64 µm) images, with plots of GLM Flashes [click to play animated GIF | MP4]

In a comparison of ~500-meter resolution GOES-16 Visible and ~15-meter resolution Landsat-8 Panchromatc images valid at 1557 UTC — viewed using RealEarth (below) — the Landsat image provided a more detailed view of the cloud structures within the eye of Hurricane Ian as it was just off the west coast of Florida.

GOES-16 “Red” Visible (0.64 µm) and Landsat-8 Panchromatic (0.59 µm) images, valid at 1557 UTC [click to enlarge]

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 makes landfall in Nova Scotia

September 24th, 2022 |

GOES-16 Mid-level Water Vapor (6.9 µm) images [click to play animated GIF | MP4]

Hurricane Fiona transitioned to a strong post-tropical cyclone just prior to making landfall in Nova Scotia, Canada around 0700 UTC on 24 September 2022 — 1-minute Mesoscale Domain Sector GOES-16 (GOES-East) Mid-level Water Vapor (6.9 µm) images (above) showed the storm during the 0200-1800 UTC period. This anomalously-deep cyclone may have set a new Canadian record (931 hPa) for minimum mean sea level pressure (surface analyses). The highest surface wind gust was 97 knots / 112 mph / 179 km/h at mesonet site Arisaig (along the northeastern coast of mainland Nova Scotia), with a peak wind gust of 90 knots / 104 mph / 167 km/h at METAR site Grand Etang CWGQ (just off the west coast of Cape Breton Island) shortly before 0800 UTC. A preliminary storm summary issued by Environment Canada is available here.

One feature of interest was a region of lee waves generated by strong easterly boundary layer winds interacting with the Highlands terrain in the northern portion of Cape Breton Island — these waves spread westward across parts of the Gulf of Saint Lawrence (below).

Comparison of GOES-16 Water Vapor image at 0700 UTC and topography [click to enlarge]

Sentinel-1A Synthetic Aperture Radar (SAR) water surface winds at 1015 UTC (below) captured lighter winds of 20 knots or less (brighter shades of violet) within the post-tropical cyclone’s eye as it was emerging northwestward from Cape Breton Island — along with an arc of strong winds within the storm’s eastern semicircle, where speeds of 100 knots or higher (shades of red) were seen. Off the north coast of Cape Breton Island, the peak wind gust at St. Paul Island (CWEF) just prior to 1000 UTC was 85 knots — and SAR winds at 1015 UTC in the vicinity of CWEF were in the 75-80 knot range.

Sentinel-1A Synthetic Aperture Radar (SAR) winds at 1015 UTC [click to enlarge]


The animation of GOES-16 airmass RGB, below, shows the evolution of Fiona and its interaction with a Potential Vorticity Maximum (orange/red in the RGB).

GOES-16 airmass RGB, 0000 UTC 21 September – 0000 UTC 25 September

Perhaps you are skeptical that the Orange/Red signature in the Airmass RGB is a Potential Vorticity Signature. Consider the animation below, downloaded from the TropicalTidbits website and showing 00 – 30 hour GFS model output from the run initialized at 0000 UTC on 23 September. A rich source of cyclonic potential vorticity air (in orange) wraps around Fiona as it moves north. Similar behavior is apparent in the Airmass RGB animation above. This cross section (also from the excellent Tropical Tidbits site) of the model data (24 h into the forecast run) also shows a classic stratospheric intrusion structure.

330 K Potential Vorticity color-shaded in PV Units at 6-h time-steps, 0000 UTC on 23 September 2022 through 0600 UTC on 24 September 2022 (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]