Blowing dust along the southwest coast of Greenland

October 14th, 2018 |

As noted by Santiago Gassó, a long and very narrow plume of airborne dust was evident just off the southwest coast of Greenland on 14 October 2018. Terra MODIS and Suomi NPP VIIRS True Color Red-Green-Blue (RGB) images as viewed using RealEarth are shown below. An exposed (free of snow cover) glacial outlet between Qeqertarsuatsiaat and Paamiut was the point source of the dust plume — the change in water colors (shades of cyan) highlighted the offshore flow of meltwater from this glacier into the Labrador Sea, which then began to curve northward within the West Greenland Current. The strong pressure gradient between high pressure over southern Greenland and a low pressure southeast of the island (surface analyses) along with a passing trough axis caused brisk northerly winds, which lofted the aerosols into the boundary layer.

Terra MODIS and Suomi NPP VIIRS True Color RGB images [click to enlarge]

Terra MODIS and Suomi NPP VIIRS True Color RGB images [click to enlarge]

The plume of aerosols was also apparent on GOES-16 (GOES-East) “Red” Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images (below). The appearance of the plume on 1.61 µm imagery was due to the bright color of the “glacial flour” particles, which were efficient reflectors of incoming solar radiation — this brighter signature showed up well against the dark appearance of the water (which strongly absorbs radiation at the 1.61 µm wavelength).

GOES-16

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

GOES-16 Near-Infrared

GOES-16 Near-Infrared “Snow/Ice” (1.61 µm) images [click to play animation | MP4]

The plume of airborne dust was also seen on GOES-17 Visible and Near-Infrared images (below), although the viewing angle was less favorable than from GOES-16.

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

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

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

GOES-17 Near-Infrared "Snow/Ice" (1.61 µm) images [click to play animation | MP4]

GOES-17 Near-Infrared “Snow/Ice” (1.61 µm) images [click to play animation | MP4]

Unfortunately, there were no surface observations in the vicinity of the plume source to indicate how strong the surface winds were blowing; the closest active reporting sites along the southwest coast of Greenland were Godthaab/Nuuk to the distant north and Narsarsuaq to the distant south (large-scale Near-Infrared image). However, Metop-B ASCAT winds (source) just offshore of the plume origin area were in the 30-40 knots range around 1440 UTC (below).

Metop-B ASCAT surface scatterometer winds [click to enlarge]

Metop-B ASCAT surface scatterometer winds [click to enlarge]

Post-Tropical Cyclone Leslie makes landfall in Portugal

October 13th, 2018 |

Aqua MODIS True Color RGB image [click to enlarge]

Aqua MODIS True Color RGB image, with and without surface reports [click to enlarge]

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.

EUMETSAT Meteosat-11 Water Vapor (6.25 µm) images, with hourly plots of surface winds and gusts in knots [click to play animation | MP4]

EUMETSAT Meteosat-11 Water Vapor (6.25 µm) images, with hourly plots of surface winds and gusts in knots [click to play animation | MP4]

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:

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.

Meteosat-11 Water Vapor (7.35 µm) images, with hourly splots of surface winds and gusts in knots [click to play animation | MP4]

EUMETSAT Meteosat-11 Water Vapor (7.35 µm) images, with hourly plots of surface winds and gusts in knots [click to play animation | MP4]

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

Radar reflectivity composites [click to play animation]

Radar reflectivity composites [click to play animation]

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).

GOES-16 Mid-level Water Vapor (6.9 µm) images, with hourly plots of surface winds and gusts in knots [click to play animation | MP4]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with hourly plots of surface winds and gusts in knots [click to play animation | MP4]

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.

GOES-16

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

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

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



Category 4 Hurricane Michael makes landfall along the Florida coast

October 10th, 2018 |

Sequence of Infrared Window images from Terra/Aqua MODIS (11.0 µm) and Suomi NPP VIIRS (11.45 µm) [click to enlarge]

Infrared Window images from Terra/Aqua MODIS (11.0 µm) and NOAA-20/Suomi NPP VIIRS (11.45 µm) [click to enlarge]

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.

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]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

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).

GOES-16

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

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

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

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 high-end Category 4 storm with maximum sustained winds of 135 knots (155 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 "Red" Visible (0.64 µm) images [click to play MP4 animation]

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

GOES-16 "Clean" Infrared Window (10.3 µm) images [click to play MP4 animation]

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

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).

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with surface observations and with/without a map overlay [click to play animation | MP4]

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.

GOES-17 "Red" Visible (0.64 µm) images, with surface observations and with/without a map overlay [click to enlarge]

GOES-17 “Red” Visible (0.64 µm) images, with surface observations and with/without a map overlay [click to enlarge]

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.

16-panel images of all GOES-16 ABI spectral bands [click to play animation | MP4]

All 16 spectral bands of the GOES-16 ABI [click to play animation | MP4]

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.

Infrared Window images from Aqua MODIS (11.0 µm) and NOAA-20/Suomi NPP VIIRS (11.45 µm) [click to enlarge]

Infrared Window images from Aqua MODIS (11.0 µm) and NOAA-20/Suomi NPP VIIRS (11.45 µm) [click to enlarge]

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.

GOES-16 Mid/Upper-level winds, 21 UTC on 09 October to 21 UTC on 10 October [click to enlarge]

GOES-16 Mid-level (6.9 µm) Water Vapor images with Mid/Upper-level winds, from 21 UTC on 09 October to 21 UTC on 10 October [click to enlarge]

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.

Aqua MODIS Near-Infrared

Aqua MODIS Near-Infrared “Cirrus” (1.37 µm) and Water Vapor (6.7 µm) images [click to enlarge]

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

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

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

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.

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

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

Aqua MODIS True Color RGB images from 06 October and 11 October [click to enlarge]

Aqua MODIS True Color RGB images from 06 October and 11 October [click to enlarge]

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.

Aqua MODIS True Color RGB images from 06 October and 11 October [click to enlarge]

Aqua MODIS True Color RGB images from 06 October and 11 October [click to enlarge]

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).

MIMIC Total Precipitable Water images, 07-11 October [click to play animation | MP4]

MIMIC Total Precipitable Water images, 07-11 October [click to play animation | MP4]

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 =====

Terra MODIS True Color RGB images from 04 October and 18 October [click to enlarge]

Terra MODIS True Color RGB images from 04 October and 18 October [click to enlarge]

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.

Terra MODIS True Color RGB images from 04 October and 18 October [click to enlarge]

Terra MODIS True Color RGB images from 04 October and 18 October [click to enlarge]

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.

Terra MODIS False Color RGB images from 04 October and 12 October [click to enlarge]

Terra MODIS False Color RGB images from 04 October and 12 October [click to enlarge]

Medicane “Zorbas”

September 29th, 2018 |

NOAA-20 and Suomi NPP VIIRS Day/Night Band (0.7 µm) images [click to enlarge]

NOAA-20 and Suomi NPP VIIRS Day/Night Band (0.7 µm) images [click to enlarge]

Medicane “Zorbas” — as named by Freie Universität Berlin (surface analyses) — developed in the Mediterranean Sea late in the day on 27 September 2018. A toggle between VIIRS Day/Night Band (0.7 µm) images from NOAA-20 and Suomi NPP (above; courtesy of William Straka, CIMSS) revealed the well-defined circulation of the storm a few hours after Midnight local time on 28 September. Note the bright streak north of the storm center on the NOAA-20 image — this was an area of clouds illuminated by intense lightning activity. Other less prominent lightning streaks were evident in thunderstorms farther to the east over the Mediterranean Sea. On the Suomi NPP image, a small bright spot could be seen, evidence of minor volcanic activity at Mount Etna on the island of Sicily, as well as the hazy signature of a plume of blowing dust/sand that was moving northward off the coast of Libya. The corresponding VIIRS Infrared images are available here.

During the following daylight hours of 28 September, EUMETSAT Meteosat-11 High Resolution Visible (0.8 µm) images (below) showed the storm as it became better organized and increased intensity. Another dense plume of blowing dust/sand began to move off the coast of Libya late in the day.

Meteosat-11 Visible (0.8 µm) images, with hourly plots of wind barbs (yellow) and wind gusts (red) [click to play animation | MP4]

Meteosat-11 Visible (0.8 µm) images, with hourly plots of wind barbs (yellow) and wind gusts (red) [click to play animation | MP4]

On 29 September, Meteosat-11 Visible (0.8 µm) images (below) showed the Medicane moving inland along the Peloponnese coast of southern Greece — shortly after the storm center passed, winds gusted to 48 knots at Kalamata at 1220 UTC (while a heavy thunderstorm was being reported).

Meteosat-11 Visible (0.8 µm) images, with hourly plots of winds (yellow) and gusts in knots (red) [click to play animation | MP4]

Meteosat-11 Visible (0.8 µm) images, with hourly plots of wind barbs (yellow) and gusts in knots (red) [click to play animation | MP4]

A sequence of Terra and Aqua MODIS True Color Red-Green-Blue (RGB) images from 28 and 29 September from RealEarth (below) showed another view of the Zorbas on those 2 days (the valid time of the Terra MODIS image showing the eye-like feature on 29 September was 0911 UTC). Sea Surface Temperatures were near 25ºC in the central Mediterranean Sea where Zorbas was intensifying.

Terra/Aqua MODIS True Color RGB images on 28 and 29 September [click to enlarge]

Terra/Aqua MODIS True Color RGB images on 28 and 29 September [click to enlarge]

Hourly images of the MIMIC Total Precipitable Water product (below) showed moisture associated with the storm, which produced heavy rainfall and flash flooding in parts of southern Greece — the NESDIS Blended TPW Anomaly product indicated that this moisture was as much as 200% of normal for the region and date. Additional information and videos can be found here.

MIMIC morphed Total Precipitable Water images, 27-29 September [click to play animation | MP4]

MIMIC morphed Total Precipitable Water images, 27-29 September [click to play animation | MP4]