Hurricane Willa

October 22nd, 2018 |

GOES-16

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

GOES-16 (GOES-East) “Clean” Infrared Window (10.3 µm) images (above) showed Willa during the 48 hours that it rapidly intensified (ADT | SATCON) from a Tropical Storm at 15 UTC on 20 October to a Category 5 Hurricane at 15 UTC on 22 October 2018. Willa  — which became the third Category 5 hurricane of the 2018 season in the northeast Pacific basin (east of 180º longitude) — formed and had been moving over very warm water, with Sea Surface Temperatures of 29-30ºC. Deep-layer wind shear was also light during the 15 hour period lead up to Category 5 intensity.

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images (below; courtesy of William Straka, CIMSS) showed Category 4 Willa off the west coast of Mexico at 0852 UTC on 22 October. The Moon was in the Waxing Gibbous phase (at 95% of Full), providing ample illumination for a “visible image at night” using the VIIRS Day/Night Band. Intricate cloud-top gravity waves were seen propagating radially outward from the storm center.

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]

1-minute Mesoscale Domain Sector GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window images (below) revealed the small eye of the Category 5 hurricane after sunrise, with multiple convective bursts that erupted along the western edge of the eyewall. A continuous series of storm-top waves could be seen propagating radially outward away from the eye on Visible imagery. However, the eye eventually became cloud-filled as Willa began to undergo an eyewall replacement cycle — the formation of a larger-diameter outer eyewall was evident on the MIMIC-TC product — and weaken to a Category 4 intensity.

GOES-16 "Red" Visible (0.64 µm) and "Clean" Infrared Window (10.3 µm) images [click to play MP4 animation]

GOES-16 “Red” Visible (0.64 µm, left) and “Clean” Infrared Window (10.3 µm, right) images [click to play MP4 animation]

GOES-17 “Red” Visible (0.64 µm) images (below) provided a more direct view of the storm, since the satellite was positioned over the Equator at 89.5º W longitude while in its post-launch testing location.

GOES-17

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

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

 

Cloud plume from an industrial source in Ontario, Canada

October 21st, 2018 |

Thanks go out to Jason Alumbaugh from NWS Marquette, who sent the following in an email:

“Previous shift here at NWS Marquette passed along interesting feature on satellite last night. Origin of the feature is approx. 49.23 N and 91.00 W (just west of CWDV – Upsala in Ontario) but eventually the plume spread as far south as south central Upper Michigan and northeast Wisconsin (IMT to MNM). Our meteorologists said it looked like a fire and called Environment Canada overnight but they had not heard of anything reported.”

GOES-16

GOES-16 “Red” Visible (0.64 µm), Near-Infrared “Snow/Ice” (1.61 µm), Near-Infrared “Cloud Particle Size” (2.24 µm) and Shortwave Infrared (3.9 µm) images [click to play animation | MP4]

Taking a look at the initial daytime formation of the plume on 20 October 2018, a very subtle signature could be seen at times in GOES-16 (GOES-East) “Red” Visible (0.64 µm) images, but the plume was more obvious in the Near-Infrared “Snow/Ice” (1.61 µm), Near-Infrared “Cloud Particle Size” (2.24 µm) and Shortwave Infrared (3.9 µm) imagery (above). Emissions from an industrial source (likely a power plant, or perhaps the Domtar paper mill?) acted as cloud condensation nuclei, causing a higher concentration of smaller supercooled cloud droplets downwind of the plume source — and these smaller particle were more reflective and thus appeared brighter in the 1.61/2.24 µm images and warmer (darker gray) in the 3.9 µm images.

Color-enhanced 3.9 µm Shortwave Infrared imagery (below) showed the transition from a warmer (darker red) plume during the day — due to enhanced reflection of incoming solar radiation — to a colder (darker blue) plume at night.

GOES-16 Shortwave Infrared (3.9 µm) images [click to play animation | MP4]

GOES-16 Shortwave Infrared (3.9 µm) images [click to play animation | MP4]

The higher spatial resolution of MODIS and VIIRS imagery from the polar-orbiting Terra/Aqua and NOAA-20/Suomi NPP satellites offered alternative views of the plume. A comparison of Suomi NPP VIIRS Visible (0.64 µm), Day/Night Band (0.7 µm), Near-Infrared “Snow/Ice” (1.61 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images (below) showed the early stage of the plume during the day on 20 October — as was seen with GOES-16, the plume signature was most obvious in the 1.61 µm Snow/Ice and 3.74 µm Shortwave Infrared imagery.

Suomi NPP VIIRS Visible (0.64 µm), Near-Infrared

Suomi NPP VIIRS Visible (0.64 µm), Day/Night Band (0.7 µm), Near-Infrared “Snow/Ice” (1.61 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images [click to enlarge]

A nighttime comparison of Suomi NPP VIIRS Day/Night Band (0.7 µm), Shortwave Infrared (3.74 µm), Infrared Window (11.45 µm) and Fog/stratus Brightness Temperature Difference (11.45-3.74 µm) images (below) revealed signatures of the plume at 0716 UTC or 2:16 am CDT on 21 October, after it had traveled nearly 350 miles from the Ontario source to the Green Bay, Wisconsin area. Cloud-top 11.45 µm infrared brightness temperatures of the plume and the surrounding supercooled clouds were generally in the -13º to -16ºC range.

Suomi NPP VIIRS Day/Night Band (0.7 µm), Shortwave Infrared (3.74 µm), Infrared Window (11.45 µm) and Fog.stratus BTD (11.45-3.74 µm) images [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm), Shortwave Infrared (3.74 µm), Infrared Window (11.45 µm) and Fog/stratus BTD (11.45-3.74 µm) images [click to enlarge]

A sequence of nighttime Fog/stratus BTD images from Terra/Aqua MODIS and NOAA-20/Suomi NPP VIIRS (below) showed the plume moving southeastward across the Upper Peninsula of Michigan into northeastern Wisconsin. BTD values associated with the plume were in the 3-5ºC range (darker shades of red). [Note: the NOAA-20 VIIRS images are incorrectly labeled as Suomi NPP]

Terra/Aqua MODIS and NOAA-20/Suomi NPP VIIRS Fog/stratus BTD images [click to enlarge]

Terra/Aqua MODIS and NOAA-20/Suomi NPP VIIRS Fog/stratus BTD images [click to enlarge]

Subtle signature of temperature advection seen in GOES-16 infrared imagery

October 18th, 2018 |

Topography background with surface pressure analyses at 03, 06 and 09 UTC [click to enlarge]

Topography background with surface pressure analyses at 03, 06 and 09 UTC [click to enlarge]

With a large dome of high pressure centered over Iowa/Missouri/Illinois (above), the stage was set for a night of strong radiational cooling across much of the Upper Midwest on 17/18 October 2018. Minimum temperatures were generally in the 20-40ºF range, with the coldest being 15ºF at Champion in the Upper Peninsula of Michigan.

An animation of 5-minute GOES-16 (GOES-East) “Clean” Infrared Window (10.3 µm) images (below) suggested a lack of clouds across most of the region, except for some patchy mid/high-level clouds drifting slowly northward from Nebraska/Wyoming across western South Dakota and far southeastern Montana. However, a close inspection of the imagery revealed the subtle appearance of “motion” across northern/eastern North Dakota into eastern South Dakota and far western Minnesota. This was noted by Carl Jones (NWS Grand Forks), who further pointed out “strong winds just above the surface (45 kt at 900ft per KMVX VWP) mixing down a huge warm tongue at 900mb along with downslope influences”. A comparison of the GOES-16 Infrared images with topography showed the slightly higher elevation of the Coteau du Missouri (elevation around 2000 feet) across southwestern North Dakota and western South Dakota along with the more narrow Coteau des Prairies in northeastern South Dakota and southwestern Minnesota — and a subtle “downslope warming” effect could be seen on the Infrared images (warmer temperatures are darker shades of blue with the applied enhancement).

GOES-16

5-minute GOES-16 “Clean” Infrared Window (10.3 µm) images + topography, with hourly plots of surface reports [click to play animation | MP4]

The same effect was evident on hourly images of the GOES-16 Land Surface Temperature product (below). However, with the Land Surface Temperature product enhancement, warmer temperatures appear as lighter shades of cyan.

GOES-16 Land Surface Temperature product + topography, with hourly plots of surface reports [click to play animation | MP4]

Hourly GOES-16 Land Surface Temperature product + topography, with plots of surface reports [click to play animation | MP4]

Similarly, a sequence of higher spatial resolution Infrared Window images from Terra/Aqua MODIS (11.0 µm) and NOAA-20/Suomi NPP VIIRS (11.45 µm) (below) showed the slow propagation of the downslope warming. The lack of fog or low clouds was confirmed via this comparison of VIIRS Infrared Window and “Fog product” Brightness Temperature Difference at 0903 UTC; no airports were reporting any clouds or a surface visibility less than 10 miles.

Infrared Window images from Terra/Aqua MODIS (11.0 µm) and NOAA-20/Suomi NPP VIIRS (11.45 µm), with topography and plots of surface reports [click to enlarge]

Infrared Window images from Terra/Aqua MODIS (11.0 µm) and NOAA-20/Suomi NPP VIIRS (11.45 µm) + topography, with plots of surface reports [click to enlarge]

12 UTC NAM40 winds and isotachs at a height of 0.5 km above ground level (below) verified the presence of broad southwesterly flow off the Coteau du Missouri and the Coteaus des Prairies, with subtle warming (darker shades of blue) immediately downwind.

GOES-16

GOES-16 “Clean” Infrared Window (10.3 µm) image + topography, with NAM40 winds/isotachs at 0.5 km above ground level [click to enlarge]

Plots of 12 UTC rawinsonde data from Bismarck, North Dakota and Aberdeen, South Dakota (below) showed strong low-level temperature inversions that morning — and at the top of those temperature inversions, southwesterly winds of 27 knots at a height of 1056 feet over Bismarck and 26 knots at 728 feet over Aberdeen.

Plot of 12 UTC rawinsonde data from Bismarck, North Dakota [click to enlarge]

Plot of 12 UTC rawinsonde data from Bismarck, North Dakota [click to enlarge]

Plot of 12 UTC rawinsonde data from Aberdeen, South Dakota [click to enlarge]

Plot of 12 UTC rawinsonde data from Aberdeen, South Dakota [click to enlarge]

 

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]