Gravity waves over the Gulf of Mexico and Florida

January 22nd, 2020 |

GOES-16 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images, with pilot reports of turbulence [click to play animation | MP4]

GOES-16 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images, with pilot reports of turbulence [click to play animation | MP4]

GOES-16 (GOES-East) Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (above) showed a packet of gravity waves over the eastern Gulf of Mexico and southern Florida on 22 January 2020. Later time in the time period, there were isolated pilot reports of moderate turbulence in the vicinity of the waves (though it’s uncertain whether the gravity waves were directly responsible).

What caused these gravity waves to form and slowly propagate southeastward is also uncertain — earning this example its place in the “What the heck is this?” blog category. The SPC Mesoscale Analysis at 07 UTC (below) did show weak convergence of 300 hPa ageostrophic winds (dark blue oval) in the entrance region of a secondary jet streak “J” over the Gulf of Mexico — this convergence could have played a role in the gravity wave development.

SPC Mesoscale Analysis valid at 07 UTC, showing 300 hPa height, isotachs and ageostrophic winds [click to enlarge]

SPC Mesoscale Analysis valid at 07 UTC, showing 300 hPa height, isotachs and ageostrophic winds [click to enlarge]

GOES-16 Derived Motion Winds (calculated using 6.9 µm imagery) in the vicinity of the gravity waves (below) had velocities in the 50-60 knot range at pressure levels of 370-380 hPa (0916 UTC).

GOES-16 Water Vapor (6.2 um) Derived Motion Winds [click to enlarge]

GOES-16 Water Vapor (6.9 µm) Derived Motion Winds [click to enlarge]

Also of note was the fact that the surface of Florida was sensed by Low-level Water Vapor imagery (below). With an unseasonably cold, dry air mass moving southward over the peninsula, the 7.3 µm water vapor weighting function was shifted to lower altitudes — this allowed the thermal contrast between relatively cool land surfaces and the surrounding warmer water to be seen in the 7.3 µm imagery.

GOES-16 Low-level (7.3 µm) Water Vapor images, with pilot reports of turbulence [click to play animation | MP4]

GOES-16 Low-level (7.3 µm) Water Vapor images, with pilot reports of turbulence [click to play animation | MP4]

At Key West, Florida the Total Precipitable Water value of 0.3 inch calculated from 12 UTC rawinsonde data (below) was a new record for the date/time (the previous record minimum value was 0.36 inch).

Climatology of Total Precipitable Water for the Key West, Florida rawinsonde site [click to enlarge]

Climatology of Total Precipitable Water for the Key West, Florida rawinsonde site [click to enlarge]

Eruption of Mount Shishaldin in Alaska

January 19th, 2020 |

Topography along with Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images at 1323 UTC [click to enlarge]

Topography along with Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images at 1323 UTC [click to enlarge]

Following two days of increasing seismicity, Mount Shishaldin began a period of more intense eruptive activity around 0930 UTC on 19 January 2020 — a comparison of topography along with Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images at 1323 UTC (above) displayed a distinct thermal anomaly (cluster of red 3.74 µm pixels) and a volcanic cloud moving east-southeastward.

Comparisons of Shortwave Infrared and Infrared Window images from Suomi NPP VIIRS and GOES-17 ABI (below) revealed a parallax shift that is inherent with geostationary imagery at high latitudes.

Comparison of Shortwave Infrared images from Suomi NPP VIIRS (3.74 um) and GOES-17 ABI (3.9 um) [click to enlarge]

Comparison of Shortwave Infrared images from Suomi NPP VIIRS (3.74 µm) and GOES-17 ABI (3.9 µm) [click to enlarge]

Comparison of Infrared Window images from Suomi NPP VIIRS (11.45 µm) and GOES-17 ABI (10.35 µm) [click to enlarge]

Comparison of Infrared Window images from Suomi NPP VIIRS (11.45 µm) and GOES-17 ABI (10.35 µm) [click to enlarge]

A toggle between GOES-17 parallax correction vectors and magnitudes for cloud top heights of 15,000 feet (4.5 km) and 30,000 feet (9.1 km) are shown below —  the amount of northwestward volcanic cloud displacement between the Suomi NPP and GOES-17 Infrared images roughly matched the 16 km (or 10 mile) value for a 15,000 foot cloud top in that region of the Full Disk. Later advisories listed the maximum ash height at 20,000-30,0000 feet.

GOES-17 parallax correction vectors (green) and magnitudes (km, red) [click to enlarge]

GOES-17 parallax correction vectors (green) and magnitudes (km, red) [click to enlarge]

1-minute Mesoscale Domain Sector GOES-17 (GOES-West) Split Cloud Top Phase (11.2 – 8.4 µm) images (below) displayed an increasing volcanic ash signal (negative values, darker blue to violet enhancement) beginning around 01 UTC on 20 January. Some light ash fall was reported at False Pass, Alaska.

GOES-17 Split Cloud Top Phase (11.2 - 8.4 um) images [click to play animation | MP4]

GOES-17 Split Cloud Top Phase (11.2 – 8.4 µm) images [click to play animation | MP4]

10-minute images of GOES-17 radiometrially retreived Ash Height from the NOAA/CIMSS Volcanic Cloud monitoring site (below) indicated that the bulk of the ash plume existed within the 2-6 km altitude range.

GOES-17 Ash Height product [click to play animation | MP4]

GOES-17 Ash Height product [click to play animation | MP4]

In corresponding GOES-17 False Color Red-Green-Blue (RGB) images (below), the volcanic plume exhibited shades of red/magenta/pink — the characteristic signature of an ash-laden cloud.

GOES-17 False Color RGB [click to play animation | MP4]

GOES-17 False Color RGB [click to play animation | MP4]

Tropical Cyclone Tino in the South Pacific Ocean

January 16th, 2020 |

Himawari-8

Himawari-8 “Clean” Infrared Window (10.4 µm) images [click to play animation | MP4]

JMA Himawari-8 “Clean” Infrared Window (10.4 µm) images (above) showed the development of Tropical Cyclone Tino in the South Pacific Ocean on 16 January 2020. Tino was moving southeast toward the island nation of Fiji. Convection around the tropical cyclone exhibited extensive cloud-top infrared brightness temperatures (IRBTs) of -90ºC and colder (shades of yellow embedded within the dark purple enhancement), including a few red -100ºC pixels at 1630 UTC.

Plots of rawinsonde data from Fiji (below) showed a tropopause around 100 hPa, where the temperature was around -85ºC — so the tropical overshooting tops with IRBTs in the -90 to -100ºC range were extending into the stratosphere.

Plots of rawinsonde data from Fiji [click to enlarge]

Plots of rawinsonde data from Nandi, Fiji [click to enlarge]

Plots of deep-layer wind shear from the CIMSS Tropical Cyclones site (below) indicated that Tino gradually intensified within a narrow zone of light shear.

Plots of deep-layer wind shear [click to enlarge]

Plots of deep-layer wind shear [click to enlarge]

===== 17 January Update =====

GOES-17

GOES-17 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

A GOES-17 (GOES-West) Mesoscale Domain Sector was positioned over Tropical Cyclone Tino on 17 January, providing images at 1-minute intervals — “Clean” Infrared Window (10.35 µm) images (above) showed the continued development of convective bursts, which at times exhibited IRBT values as cold as -100ºC (red pixels on the coldest portion of the enhancement).

Eruption of the Taal Volcano in the Philippines

January 12th, 2020 |

Himawari-8

Himawari-8 “Red” Visible (0.64 µm, left) and “Clean” Infrared Window (10.4 µm, right) images [click to play animation | MP4]

The Taal Volcano erupted in the Philippines around 0850 UTC on 12 January 2020. JMA Himawari-8 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.4 µm) images (above) displayed the volcanic cloud during the initial 3 hours post-eruption. Note the presence of a pronounced “warm wake” (red enhancement) downwind (north) of the summit of Taal — this appeared to be an Above-Anvil Cirrus Plume (AACP), as seen in a toggle between the Visible and Infrared images at 1910 UTC (below).

Himawari-8 "Red" Visible (0.64 µm) and "Clean" Infrared Window (10.4 µm) images at 1910 UTC [click to enlarge]

Himawari-8 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.4 µm) images at 1910 UTC [click to enlarge]

The warmest Himawari-8 10.4 µm brightness temperatures within the Above-Anvil Cirrus Plume were around -60ºC (red enhancement), which corresponded to approximately 21 km on data from 3 rawinsonde sites in the Philippines (Legaspi, Mactan and Laoag) (below).

Plots of rawinsonde data from Legaspi, Mactan and Laoag in the Philippines [click to enlarge]

Plots of rawinsonde data from Legaspi, Mactan and Laoag in the Philippines [click to enlarge]

The TROPOMI detected SO2 at altitude of 20km on 13 January:


A longer animation of Himawari-8 Infrared imagery revealed the intermittent presence of the warm wake feature until about 1400 UTC. The coldest 10.4 µm cloud-top brightness temperature was -89.7ºC.

Himawari-8 "Clean" Infrared Window (10.4 µm) images [click to play animation | MP4]

Himawari-8 “Clean” Infrared Window (10.4 µm) images [click to play animation | MP4]

A large-scale view of Himawari-8 Infrared images (below) showed that the volcanic cloud was advected a great distance north-northeastward.

Himawari-8 "Clean" Infrared Window (10.4 µm) images [click to play animation | MP4]

Himawari-8 “Clean” Infrared Window (10.4 µm) images [click to play animation | MP4]

A toggle between NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images (below) showed the volcanic cloud at 1649 UTC.

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images at 1648 UTC (credit: William Straka, CIMSS) [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images at 1648 UTC (credit: William Straka, CIMSS) [click to enlarge]

In a sequence of Split Window Difference (11-12 µm) images (Terra MODIS, NOAA-20 VIIRS and Suomi NPP VIIRS) from the NOAA/CIMSS Volcanic Cloud Monitoring site (below), there was only a subtle ash signature (blue enhancement) immediately downwind of the Taal summit — due to the large amount of ice within the upper portion of the volcanic cloud, the infrared spectral ash signature was significantly masked.

Split Window Difference (11-12 um) images from Terra MODIS, NOAA-20 VIIRS and Suomi NPP VIIRS [click to enlarge]

Split Window Difference (11-12 µm) images from Terra MODIS, NOAA-20 VIIRS and Suomi NPP VIIRS [click to enlarge]

Of interest was the fact that Manila International Airport (RPLL) reported a thunderstorm at 15 UTC — there was a large amount of lightning produced by Taal’s volcanic cloud.

===== 14 January Update =====

GOES-17 SO2 RGB images [click to play animation | MP4]

GOES-17 SO2 RGB images [click to play animation | MP4]

2 days after the eruption, the leading edge of Taal’s SO2-rich volcanic plume (brighter shades of yellow over areas of cold clouds) began to appear within the far western view of GOES-17 (GOES-West) Full Disk SO2 Red-Green-Blue (RGB) images (above), about 1000 miles southeast of Japan. There were also some thin filaments of SO2 (brighter shades of white over warm ocean areas) moving southward, about 1500 miles west of Hawai’i.