20 days after Leslie initially formed (and 17 days after it underwent extratropical transition), an Aqua MODIS True Color Red-Green-Blue (RGB) image viewed using RealEarth (above) showed the storm at 1419 UTC on 13 October 2018, when it was still classified as a Category 1 Hurricane off the coast of Portugal. The southwest-to-northeast oriented cloud band just west of Leslie was associated with an advancing cold front (surface analyses), which soon began to absorb the tropical cyclone and aid in its extra-tropical transition a few hours prior to landfall.

EUMETSAT Meteosat-11 middle/upper-tropospheric Water Vapor (6.25 µm) images (below) exhibited a warm/drying trend (brighter shades of yellow) along the western and southern edges of Leslie as it moved inland across Portugal. Hourly Meteosat-11 Water Vapor images visualized using RealEarth are available here.

Along the coast of Portugal a thunderstorm was reported at Porto (LPPR) from 1930-2000 UTC (about an hour before landfall). Farther to the south, shortly after landfall the surface winds gusted to 55 knots (63 mph or 28.3 m/s) at Monte Real Air Base (LPMR) at 21 UTC and 42 knots (48 mph or 21.6 m/s) at Ovar Military Base (LPOV) at 23 UTC. The highest wind gust was 95 knots (110 mph or 49 m/s) at Figueira da Foz, located along the coast between LPMR and LPOV:

According to data from @ipma_pt a maximum wind gust of 176,4 km/h has been measured in Figueira da Foz near the coast during the passage of storm #Leslie! Two more hurricane-force gusts were observed in Coimbra and Aveiro (Image source: https://t.co/gOO95O2WUz). #wetter pic.twitter.com/T55ykhL8Vm

— Luca Mathias (@meteomathias) October 14, 2018

Meteosat-11 lower/middle-tropospheric Water Vapor (7.35 µm) images (below) revealed the characteristic “scorpion tail” signature of a Sting Jet (Monthly Weather Review | Wikipedia), along with a mesoscale region of warming/drying (darker shades of orange) driven by strong subsidence — this subsidence feature corresponded well with the report of strong winds at Figueira da Foz. Further discussion of this sting jet event is available here.

Radar composites from the Portuguese Institute for Sea and Atmosphere (IPMA) confirmed that post-tropical cyclone Leslie made landfall around 2100 UTC (below).

Although the view from GOES-16 (GOES-East) was very oblique, the warm/dry signature around the western and southern edges of the storm was still evident on Mid-level Water Vapor (6.9 µm) imagery (below).

The entire life cycle of Leslie — from becoming a named Subtropical Storm at 15 UTC on 23 September to making landfall as a post-tropical cyclone in Portugal at 21 UTC on 13 October — is shown with 15-minute GOES-16 “Clean” Infrared Window (10.3 µm)  and Mid-level Water Vapor (6.9 µm) images (below). Note that 5-minute imagery was available on 01 October, when GOES-16 was performing a test of the Mode 4 scan strategy.

The long and winding adventure of Hurricane #Leslie has finally come to a close. Over its 22.25 day existence as a coherent cyclone, it largely spun harmlessly over open ocean. It ultimately impacted #Portugal as an extratropical cyclone, producing wind gusts upwards of 110mph. pic.twitter.com/9vrOiBxQAy

— Brenden Moses (@Cyclonebiskit) October 14, 2018

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The VIIRS (Visible-Infrared Imaging Radiometer Suite) instrument onboard NOAA-20 includes a Day Night Band that can be used to assess, among other things, power outages after a strong storm such as Hurricane Michael. The toggle above shows Day Night Band imagery from 6 October (before Michael) and 12 October (after Michael), and the change in illumination from city lights over the Florida Panhandle northeastward into east-central Georgia is stark.

Of course, clouds can also mask city lights in the Day Night Band. However, 11.45 µm infrared imagery from VIIRS, below, on 12 October, shows scant evidence of clouds over the region where city lights are missing.

(NOAA-20 images here courtesy William Straka, CIMSS)

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A sequence of Infrared Window images from Terra/Aqua MODIS (11.0 µm) and NOAA-20/Suomi NPP VIIRS (11.45 µm) (above) showed Category 4 Hurricane Michael as it was making its approach toward the Florida coast during the nighttime hours preceding sunrise on 10 October 2018. The yellow pixels east of the eye on the 0724 UTC VIIRS image highlighted cloud-top infrared brightness temperatures of -90ºC and colder (with a minimum of -92ºC).

Toggles between VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP (below; courtesy of William Straka, CIMSS) revealed convectively-generated mesospheric airglow waves propagating away from the hurricane.

Overlapping GOES-16 (GOES-East) Mesoscale Domain Sectors provided 30-second interval  “Clean” Infrared Window (10.3 µm) and “Red” Visible (0.64 µm) images of Michael after sunrise (below).

Closer views of GOES-16 Visible and Infrared images (below) showed Hurricane Michael making landfall around 1730-1745 UTC near Mexico Beach, Florida as a Category 5 storm with estimated maximum sustained winds of 140 knots (160 mph) and a minimum central pressure of 919 hPa (27.41 inches). During the 24-hour period prior to landfall, Michael had been moving over water having moderate Ocean Heat Content and warm Sea Surface Temperatures; and as had been the case during much of Michael’s time as a hurricane, in spite of the fact that deep-layer wind shear was somewhat unfavorable (09 October | 10 October landfall), the storm was still able to maintain a trend of intensification (ADT | SATCON). Additional information regarding the landfall of Michael (and its historical significance) is available here.

GOES-16 Geostationary Lightning Mapper (GLM) Groups — aggregates of individual lightning Events — are plotted on 30-second GOES-16 Visible images (below). The red symbols denote lightning Groups within the 1-minute period immediately preceding the Visible image time. The native GLM parallax correction is turned off — so the lightning locations correspond to where the satellite viewed the lightning signatures at the tops of the clouds.

As pointed out on Twitter by the SOO at NWS Nashville, GOES-16 Visible imagery (below) revealed the bright white sandy beaches of Saint Andrew Sound (Google Maps) as the eye of Michael passed overhead. Surface observations from Panama City (KECP), Tyndall AFB (KPAM) and Apalachicola (KAAF) are plotted on the images — all 3 sites stopped reporting after landfall, presumably due to power outages (the peak wind gust at Tyndall AFB was 129 mph). A longer animation (from 1300-1959 UTC) of 30-second GOES-16 Visible images is available here (courtesy of Pete Pokrandt, UW-AOS).

The signature of the beaches was also evident on GOES-17 Visible imagery (below) —  but since that satellite was scanning at the standard 5-minute interval, they were only seen on 2 consecutive images. Note that GOES-17 imagery shown here  is preliminary and non-operational.

One item of local curiosity that was observed on GOES-16 Visible imagery: a darker shadow-like feature within the eye, which slowly migrated from the northern to the western portion during the 1613-1642 UTC period (1625 UTC still image | MP4 animation). Closer inspection of the GOES-16 ABI Near-Infrared and Infrared spectral bands (below) indicated that this was indeed a cloud shadow, from a cirrus filament that became detached from the southeastern edge of the eyewall and then rotated cyclonically within the eye to cast a shadow against the brightly-illuminated quasi-vertical edges of the eyewall.

A sequence of Infrared Window images from Aqua MODIS (11.0 µm) and NOAA-20/Suomi NPP VIIRS (11.45 µm) (below) provided a high-resolution view of the cold cloud tops associated with Michael during and shortly after landfall.

On a larger scale, GOES-16 mid/upper-level Derived Motion Winds from the CIMSS Tropical Cyclones site (below) revealed the development of a well-defined outflow channel to the north of the storm, especially during the 12 hours prior to landfall — this enhanced poleward outflow (aided by the approach of an upper-level trough from the central US) may have been a contributing factor in Michael’s continued intensification leading up to landfall.

Aqua MODIS Near-Infrared “Cirrus” (1.37 µm) and Water Vapor (6.7 µm) images (below) showed that clouds and moisture were being transported by this outflow channel as far northward as the Ohio River Valley shortly after the time of landfall.

A GOES-16 Red-Green-Blue (RGB) animation (below; courtesy of Rick Kohrs, SSEC) showed the landfall of Michael.

A stereoscopic animation using GOES-16 and GOES-17 Visible imagery is provided below; to view the animation in 3-D, cross your eyes until 3 images appear — then focus on the image in the middle. Note that GOES-17 images shown here are preliminary and non-operational.

===== 11 October Update =====

A before/after comparison of Aqua MODIS True Color RGB images (source) from 06 October and 11 October (above) showed a dramatic increase in turbidity of the water off the “Emerald Coast” portion of the Florida Panhandle — this turbidity was the result of turbulent mixing of the relatively shallow continental shelf water by the strong winds of the hurricane. The close-up images above are centered off the coast near the landfall location; the large-scale images below show more of the Gulf Coast, from Texas to the Florida Peninsula.

Hourly images of the MIMIC Total Precipitable Water product during the 5-day period from 07-11 October (below) showed the transport of tropical moisture from the Caribbean Sea across the Gulf of Mexico and over the southeastern US — heavy rainfall and flooding occurred from Florida and Alabama to the Mid-Atlantic states (WPC summary).

The entire life cycle of Michael can be viewed in a compilation of GOES-16 Infrared 1-minute (or 30-second, when available) Mesoscale Sector images from 07-11 October, available here  — with a zoomed-in version of the images from 08-11 October available here or on YouTube (courtesy of Pete Pokandt, UW-AOS).

===== 18 October Update =====

A comparison of before/after Terra MODIS True Color RGB images from 04 October and 18 October (above) revealed a broad swath of damaged/dead vegetation (lighter shades of brown) along the path of strongest winds associated with the eyewall of Hurricane Michael.

Larger-scale versions of those same before/after Terra MODIS True Color RGB images from the SSEC MODIS Direct Broadcast site (below) showed that the path of damaged vegetation extended far northeastward across Georgia — Michael was still at Category 3 intensity when its center moved into the southwestern corner of the state.

A before/after comparison of Terra MODIS False Color RGB images (using Bands 7-2-1) from 04 October and 12 October (below) showed the area rivers that were in varying stages of flooding (darker shades of blue) following the heavy rainfall from Michael (the total precipitation was 8 inches above normal or 600% of normal for the 14-day period of 04-18 October). Most obvious was the Chipola River, which was at Moderate flood stage on 14 October.

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Metop-A ASCAT scatterometer data (above) showed surface wind speeds as high as 64 knots near the storm center while Michael was at Category 2 intensity just northwest of Cuba at 0307 UTC on 09 October 2018.

A toggle between Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images at 0752 UTC (below; courtesy of William Straka, CIMSS) revealed transverse banding north of the storm center on the Infrared image, and mesospheric airglow waves propagating westward away from Michael on the Day/Night Band image.

5-minute GOES-16 (GOES-East) “Clean” Infrared Window (10.3 µm) images from 0517-1332 UTC (below) showed a series of relatively brief convective bursts around the storm center, but in general Michael exhibited a somewhat disorganized appearance during that time period.

After sunrise, 1-minute Mesoscale Domain Sector GOES-16 “Red” Visible (0.64 µm) images (below) revealed the gradual formation of a more well-defined eye during the day, with episodic clusters of convective “hot towers” developing in the southeastern and eastern portions of the eyewall — which then rotated around to the north and northwest of the eye. By 18 UTC Michael had intensified to a Category 3 storm.

1-minute GOES-16 “Clean” Infrared Window images (below) indicated that infrared brightness temperatures associated with these hot towers were often as cold as -80º to -89ºC (violet to darker purple enhancement).

Michael had been encountering unfavorable deep-layer wind shear and had also been moving over a pocket of water with low Ocean Heat Content northwest of Cuba (below). However, once the hurricane began to move over waters having higher OHC in addition to warm Sea Surface Temperature, it gradually began to intensify from a Category 2 to a Category 3.

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