Fog/stratus dissipation in southern Louisiana

October 30th, 2018 |

GOES-16

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

The topic of a conversation on Twitter, GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) revealed curious circular areas of fog/stratus dissipation across southern Louisiana on the morning of 30 October 2018. — making it a natural candidate for the “What the heck is this?” blog category.

GOES-16 GEOCAT Low IFR Probability and Fog/Low Stratus Depth products (below) indicated that this fog and low stratus had been increasing in coverage and spreading northward across Louisiana during the preceding nighttime hours (VIIRS fog/stratus Brightness Temperature Difference images) — and the fog/stratus was relatively shallow, only having a depth of about 300 feet or less. In fact, if you look closely at the Visible animation above, a few small spots of slightly brighter cloud can be seen in the vicinity of Baton Rouge KBTR which are tall objects (such as refinery stacks, and even the State Capitol building) protruding above the fog/stratus and acting as an obstacle to their flow.

GOES-16 Low Instrument Flight Rules (IFR) Probability [click to play animation | MP4]

GOES-16 Low Instrument Flight Rules (IFR) Probability [click to play animation | MP4]

GOES-16 Fog/Low Stratus Depth product [click to play animation | MP4]

GOES-16 Fog/Low Stratus Depth product [click to play animation | MP4]

A sequence of 4-panel comparisons of GOES-16 “Blue” Visible (0.47 µm), “Red” Visible (0.64 µm) and Near-Infrared “Vegetation” (0.86 µm) images with Near-Infrared “Snow/Ice” (1.61 µm), Near-Infrared “Cloud Particle Size” (2.24 µm) and Shortwave Infrared (3.9 µm) images (below) showed no indication of any substantial differences between the cloud material within the circular features and the adjacent fog/stratus. The largest “outer rings” of the dissipating fog/stratus areas had a small amount of vertical extent, which cast a shadow that was best seen in the Near-Infrared 0.86 µm and 1.61 µm images.

4-panel comparisons of GOES-16

Sequence of 4-panel comparisons of GOES-16 “Blue” Visible (0.47 µm), “Red” Visible (0.64 µm), Near-Infrared “Vegetation” (0.86 µm), “Snow/Ice” (1.61 µm), and “Cloud Particle Size” (2.24 µm), and Shortwave Infrared (3.9 µm) images [click to play animation | MP4]

The most plausible explanation for the circular dissipation features turned out to be fires that were set in sugar cane fields following harvest — particulates in the smoke could have “seeded” the fog/stratus cloud layer, either changing the particle size distribution or making the cloud more susceptible to faster dissipation after sunrise due to solar heating of black carbon nuclei within the cloud droplets.  An Aqua MODIS Shortwave Infrared (3.7 µm) image from the previous afternoon (below) did reveal a number of small thermal anomalies or fire “hot spots” (yellow to red pixels) across the region at 1909 UTC (2:09 PM local time).

Aqua MODIS Shortwave Infrared (3.7 µm) image [click to enlarge]

Aqua MODIS Shortwave Infrared (3.7 µm) image [click to enlarge]

Similarly, GOES-16 Shortwave Infrared images on 29 October (below) also showed signatures of widespread small and generally short-lived fires (darker black pixels) across southern Louisiana. Surface winds were very light across that area (KARA | KPTN | KNBG | KMSY | KNEW), minimizing smoke dispersion from any fires.

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]

Flood wave along the Nueces River in Texas

October 27th, 2018 |

As pointed out by NWS Corpus Christi (above), GOES-16 (GOES-East) Near-Infrared “Vegetation” (0.86 µm) images revealed an interesting flood wave moving along the Nueces River on 27 October 2018 (following a recent period of heavy rainfall).

A toggle between before (10 October) and after (27 October) Aqua MODIS False Color Red-Green-Blue (RGB) images from the MODIS Today site (below) showed dramatic differences between the amount of water (darker shades of blue) flowing along portions of the Nueces River on those 2 days.

Before (10 October) and after (27 October) Aqua MODIS False Color RGB images [click to enlarge]

Before (10 October) and after (27 October) Aqua MODIS False Color RGB images [click to enlarge]

A comparison of Suomi NPP VIIRS Visible (0.64 µm), Near-Infrared Vegetation (0.86 µm) and Near-Infrared Snow/Ice (1.61 µm) images from 27 October (below) demonstrated the improved land/water contrast of the Near-Infrared imagery, which makes it helpful for diagnosing certain types of flooding signatures.

Suomi NPP VIIRS Visible (0.64 µm), Near-Infrared Vegetation (0.86 µm) and Near-Infrared Snow/Ice (1.61 µm) images [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm), Near-Infrared Vegetation (0.86 µm) and Near-Infrared Snow/Ice (1.61 µm) images [click to enlarge]

===== 28 October Update =====

GOES-16 Near-Infrared

GOES-16 Near-Infrared “Vegetation” (0.86 µm) images at 1552 UTC on 27 and 28 October [click to enlarge]

A toggle between GOES-16 Near-Infrared “Vegetation” (0.86 µm) images at 1552 UTC on 27 and 28 October (above) showed the advance of the flood wave during that 24-hour period.

A comparison of Suomi NPP VIIRS Near-Infrared “Vegetation (0.86 µm) and “Snow/Ice” (1.61 µm) images from the early afternoon hours on 27 and 28 October (below) displayed these 24-hour changes at a higher spatial resolution (375 meters, vs 1 km at satellite subpoint with GOES-16). The rear edge of the flood wave (located about 25 miles southeast of Cotulla) appeared to show up a bit better in the 0.86 µm images than the 1.61 µm.

Suomi NPP VIIRS Near-Infrared

Suomi NPP VIIRS Near-Infrared “Vegetation (0.86 µm) and “Snow/Ice” (1.61 µm) images from 27 and 28 October [click to enlarge]

Finally, in a toggle between 250-meter resolution Aqua MODIS False Color RGB images from 27 and 28 October (below), the advance of the leading edge of the flood wave can clearly be seen.

Aqua MODIS False Color RGB images from 27 and 28 October [click to enlarge]

Aqua MODIS False Color RGB images from 27 and 28 October [click to enlarge]

===== 29 October Update =====

GOES-16 Near-Infrared

GOES-16 Near-Infrared “Vegetation” (0.86 µm) images from 1552 UTC on 27, 28 and 29 October [click to enlarge]

GOES-16 Near-Infrared “Vegetation” images from 1552 UTC on 27, 28 and 29 October (above) showed the continued eastward movement of the flood wave down the Nueces River.

Mountain waves and a banner cloud over the Northeast US

October 25th, 2018 |

GOES-16 Low-level (7.3 µm), Mid=level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images [click to play MP4 animation]

GOES-16 Low-level (7.3 µm), Mid=level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images [click to play MP4 animation]

GOES-16 (GOES-East) Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (above) revealed 2 types of terrain-induced features — mountain waves, and a banner cloud (reference 1| | reference 2) — across the Northeast US on 25 October 2018.

The mountain waves were more widespread and long-lasting, while the banner cloud formed to the lee of the White Mountains in New Hampshire and Maine (extending downwind as far as 100 miles). Mountain waves are often associated with turbulence; pilot reports of Moderate turbulence appeared in the vicinity of mountain waves over far eastern New York at 1202 UTC1417 UTC and 1742 UTC. A toggle between a 1009 UTC 6.9 µm Water Vapor image with the banner cloud and Topography is shown below; a later comparison at 1802 UTC showing widespread mountain waves can be seen here.

GOES-16 Mid-level Water Vapor (6.9 µm) image + Topography [click to enlarge]

GOES-16 Mid-level Water Vapor (6.9 µm) image + Topography [click to enlarge]

Strong winds were prevalent across that region in the wake of a storm centered over the Gulf of Saint Lawrence at 12 UTC — this storm produced as much as 5-12 inches of snow on the previous day in Vermont, New Hampshire and Maine:  NWS Burlington | NWS Gray | NWS Caribou — and the approach of a mid/upper-level jet streak (below). Winds gusted to 74 knots at Mount Washington, New Hampshire.

GOES-16 Mid-level (6.9 µm) Water Vapor images, with RAP40 wind isotachs at 300 hPa [click to play animation | MP4]

GOES-16 Mid-level (6.9 µm) Water Vapor images, with RAP40 wind isotachs at 300 hPa [click to play animation | MP4]

A comparison of 1-km resolution Aqua MODIS Water Vapor (6.7 µm) and Infrared Window (11.0 µm) images at 0648 UTC (below) showed that there were some areas where the mountain waves existed in clear air, with no clouds as an indicator of wave presence (for example, over western Maine).

 Aqua MODIS Water Vapor (6.7 µm) and Infrared Window (11.0 µm) images [click to enlarge]

Aqua MODIS Water Vapor (6.7 µm) and Infrared Window (11.0 µm) images [click to enlarge]

A general lack of wave clouds over western Maine around that time was also evident on VIIRS Day/Night Band (0.7 µm) images (below) from Suomi NPP (at 0603 UTC) and NOAA-20 (at 0650 UTC). In this case, with ample illumination from the Moon — in the Waning Gibbous phase, at 99% of Full — the “visible image at night” capability of the Day/Night Band was fully realized.

Suomi NPP (0603 UTC) and NOAA-20 (0650 UTC) VIIRS Day/Night Band (0.7 µm) images [click to enlarge]

Suomi NPP (0603 UTC) and NOAA-20 (0650 UTC) VIIRS Day/Night Band (0.7 µm) images [click to enlarge]

Regarding the banner cloud which was present from about 0830-1700 UTC, the GOES-16 Cloud Top Height  and Cloud Top Phase products (below) indicated that the tops of the feature were around 24,000-25,000 feet (or 7.6 km, where the temperature was -43.1ºC on the 12 UTC Gray ME sounding: plot | text) and composed of ice crystals.

GOES-16 Cloud Top Height product [click to play animation | MP4]

GOES-16 Cloud Top Height product [click to play animation | MP4]

GOES-16 Cloud Top Phase product [click to play animation | MP4]

GOES-16 Cloud Top Phase product [click to play animation | MP4]

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 this plume of smaller particles was 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]