Eruption of Alaska’s Bogoslof volcano

December 22nd, 2016 |

Himawari-8 0.64 µm (left) and GOES-15 0.63 µm (right) Visible images [click to play animation]

Himawari-8 0.64 µm (left) and GOES-15 0.63 µm (right) Visible images [click to play animation]

Following a short-lived eruption on 21 December, the Bogoslof volcano in the eastern Aleutian Island chain of Alaska erupted again at about 0110 UTC on 22 December 2016. The volcanic cloud could be seen moving north/northeastward away from Bogoslof (denoted by the yellow * symbol) on Himawari-8 and GOES-15 Visible images (above). The higher spatial and temporal resolution from Himawari-8 (0.5 km at nadir, with images every 10 minutes) provided a more detailed view of the cloud feature compared to GOES-15 (with 1.0 km resolution at nadir, and images every 15 minutes); however, the ABI instrument on the GOES-R series will have an identical 0.5 km resolution Visible band. Another Himawari-8 Visible image animation is available from RAMMB.

Multispectral Red/Green/Blue (RGB) images from the NOAA/CIMSS Volcanic Cloud Monitoring site (below) displayed a signal of the volcanic cloud during the ~2.5 hours following the onset of the eruption — since this particular RGB combination uses the 3.9 µm Shortwave Infrared band, the volcanic cloud feature appeared as darker shades of magenta during the first few images while reflected solar illumination was present before sunset.

Himawari-8 false-color RGB images [click to play animation]

Himawari-8 false-color RGB images [click to play animation]

Another variant of RGB images (below) uses the 8.5 µm “cloud top phase” band, which is also sensitive to SO2 absorption; in this case, the appearance of the volcanic cloud feature was dominated by shades of yellow, indicating high levels of SO2.

Himawari-8 false-color RGB images [click to play animation]

Himawari-8 false-color RGB images [click to play animation]

A comparison of the 3 Himawari-8 water vapor bands (below) showed that a strong signature of the volcanic cloud was seen on the lower-tropospheric 7.3 µm band; this was due to the fact that the 7.3 µm band is also sensitive to elevated levels of SO2 loading in the atmosphere (which was also noted at the bottom of this Mount Pavlof eruption blog post). These same 3 water vapor bands (Upper-level, Mid-level and Lower-level) will be available from the GOES-R series ABI instrument.

Himawari-8 6.2 µm (top), 6.9 µm (middle) and 7.3 µm (bottom) Water Vapor images [click to play animation]

Himawari-8 6.2 µm (top), 6.9 µm (middle) and 7.3 µm (bottom) Water Vapor images [click to play animation]

A closer view using Himawari-8 false-color images (below) includes a magenta polygon surrounding the volcanic cloud soon after the onset of the eruption — this is an example of an experimental automated volcanic eruption alerting system. According to Michael Pavolonis (NOAA/NESDIS), “Using our automated cloud object tracking algorithm, the eruption produced a cloud at 01:30 UTC that was about 19 deg C colder than the background imaged by Himawari-8 at 01:20 UTC.  Taking into account the pixel size, background cloud cover, and time interval between successive images, the 19 deg C change is about an 11 standard deviation outlier relative to a very large database of meteorological clouds.  The vertical growth anomaly calculation is the basis of one the components of our experimental automated volcanic eruption alerting system”.

Himawari-8 false-color images, with a polygon surrounding the volcanic cloud [click to enlarge]

Himawari-8 false-color images, with a polygon surrounding the volcanic cloud [click to enlarge]

The creation of RGB images such as those shown above will be possible from the GOES-R series of satellites (beginning with GOES-16), since the ABI instrument has the 8.4 µm and 12.3 µm bands that are not available from the current generation of GOES imager instruments.

Additional satellite images of this event are available from NWS Anchorage.

Moderate to severe turbulence aloft near the International Date Line

December 14th, 2016 |

Himawari-8 Water Vapor (6.2 µm) images, with pilot reports of turbulence [click to play animation]

Himawari-8 Water Vapor (6.2 µm) images, with pilot reports of turbulence [click to play animation]

Himawari-8 Water Vapor (6.2 µm) images (above; also available as MP4 and McIDAS-V animations) revealed the presence of a subtle packet of upper-tropospheric gravity waves propagating southeastward near the International Date Line (180º longitude over the central Pacific Ocean), just to the west/southwest of Midway Atoll on 14 December 2016 — and there were a few pilot reports of moderate to severe turbulence (which were responsible for at least one injury) in the general vicinity of this gravity wave feature from 1530 to 1740 UTC, at altitudes of 35,000 to 38,000 feet:

PHNL UUA /OV 2800N 18000W/TM 1530/FL380/TP B767/TB MOD-SEV/RM ZOA CWSU
PHNL UUA /OV 2643N 17757W/TM 1732/FL350/TP A330/TB SEV/RM ZOA CWSU
PHNL UUA /OV 2626N 17917W/TM 1740/FL360/TP B747/TB SEV/RM ZOA CWSU

A larger-scale view using all 3 water vapor bands of the AHI instrument on the Himawari-8/9 satellites (below; also available as an MP4 animation) showed that a broad trough was moving eastward away from the International Date Line, with the signature of a jet streak diving southward toward the region of the turbulence reports (Note: the ABI instrument on the GOES-R series of satellites will feature these same 3 upper level, mid-level and lower level water vapor bands).

Himawari-8 Water Vapor (6.2 µm, top; 6.9 µm, middle; 7.4 µm, bottom) images [click to play animation]

Himawari-8 Water Vapor (6.2 µm, top; 6.9 µm, middle; 7.4 µm, bottom) images [click to play animation]

GFS model 250 hPa analyses (12 UTC | 18 UTC | source) confirmed that the region of turbulence reports was located within the exit region an approaching 50-70 m/s or 97-136 knot upper tropospheric jet, where convergence (red contours) was maximized.


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Similarly, Himawari-8 water vapor image Derived Motion Winds, below, also indicated increasing upper-tropospheric convergence along the International Date Line (180º longitude) between 25º and 30º N latitude from 12 UTC to 18 UTC (below; source).

Himawari-8 water vapor image Derived Motion Winds at 12 UTC, with corresponding contours of Upper-tropospheric divvergence [click to enlarge]

Himawari-8 water vapor image Derived Motion Winds at 12 UTC, with corresponding contours of Upper-tropospheric divvergence [click to enlarge]

Himawari-8 water vapor image Derived Motion Winds at 15 UTC, with corresponding contours of Upper-tropospheric divergence [click to enlarge]

Himawari-8 water vapor image Derived Motion Winds at 15 UTC, with corresponding contours of Upper-tropospheric divergence [click to enlarge]

Himawari-8 water vapor image Derived Motion Winds at 18 UTC, with corresponding contours of Upper-tropospheric divergence [click to enlarge]

Himawari-8 water vapor image Derived Motion Winds at 18 UTC, with corresponding contours of Upper-tropospheric divergence [click to enlarge]

A comparison of 2-km resolution Himawari-8 and 4-km resolution GOES-15 Water Vapor images (below; also available as an MP4 animation) showed that the gravity wave feature was not readily apparent on the lower spatial resolution GOES-15 images (which were only available every 30 minutes, in contrast to every 10 minutes from Himawari-8). The same color enhancement is applied to both sets of images — but because of differences between the Himawari-8 vs GOES-15 water vapor band characteristics (namely the central wavelength and the spectral response function, but also the water vapor weighting function profiles as influenced by the dissimilar satellite viewing angles) the resulting water vapor images differ in their general appearance.

Himawari-8 Water Vapor (6.2 µm, left) and GOES-15 Water Vapor (6.5 µm, right) images, with pilot reports of turbulence [click to play animation]

Himawari-8 Water Vapor (6.2 µm, left) and GOES-15 Water Vapor (6.5 µm, right) images, with pilot reports of turbulence [click to play animation]

This case demonstrated well the importance of viewing all 11 bits of information contained in the Himawari-8 Imagery. The animation at the top of the Blog Post shows an 8-bit display; a similar 8-bit display that uses a different color enhancement is here, courtesy of Dan Lindsey at CIRA. All 8-bit displays are limited to 256 different colors. The image below compares 8-bit (McIDAS-X on the left) and 11-bit (McIDAS-V on the right) displays at 1530 UTC.

Himawari-8 Water Vapor (6.2 µm) image at 1530 UTC, as viewed using 8-bit McIDAS-X (left) and 11-bit McIDAS-V (right) displays [click to enlarge]

Himawari-8 Water Vapor (6.2 µm) image at 1530 UTC, as viewed using 8-bit McIDAS-X (left) and 11-bit McIDAS-V (right) displays [click to enlarge]

Here is a toggle from AWIPS that compares 11-bit and 8-bit displays. The feature causing the turbulence is quite subtle, and 11-bit displays (which allow 2048 different colors) are necessary to accurately show it.

 

Heavy rainfall and high-elevation snowfall in Hawai’i

December 2nd, 2016 |

GOES-15 Water Vapor (6.5 µm) images, with overlays of GFS model 500 hPa geopotential height [click to play animation]

GOES-15 Water Vapor (6.5 µm) images, with overlays of GFS model 500 hPa geopotential height [click to play animation]

6-hour interval GOES-15 (GOES-West) Water Vapor (6.5 µm) images with overlays of GFS model 500 hPa geopotential height (above) showed middle to upper tropospheric moisture that was being drawn northwestward toward Hawai’i by the circulation of a closed low centered southwest of the state during the 01-02 December 2016 period.

A closer view using 15-minute interval GOES-15 Water Vapor images (below) showed 2 distinct pulses of moisture moving across the eastern portion of the island chain. Due to the prolonged flow of moisture and the variable terrain, Flood Warnings and Winter Storm Warnings were issued for the Big Island of Hawai’i (as shown using RealEarth).

GOES-15 Water Vapor (6.5 µm) images, with hourly surface reports [click to play MP4 animation]

GOES-15 Water Vapor (6.5 µm) images, with hourly surface reports [click to play MP4 animation]

Hourly images of the MIMIC Total Precipitable Water (TPW) product (below) showed the large plume of moisture, which had its roots within the Intertropical Convergence Zone (ITCZ). Maximum TPW values in the vicinity of Hawai’i were in the 50-55 mm (2.0-2.2 inch) range. 24-hour rainfall amounts were as high as 6.27 inches on the island of Hawai’i and 3.67 inches on the island of Kauai.

MIMIC Total Precipitable Water product, with tropical surface analyses [click to play animation]

MIMIC Total Precipitable Water product, with tropical surface analyses [click to play animation]

===== 03 December Update =====

GOES-15 Visible (0.63 µm) images (below) provided glimpses of the snow-covered peaks of Mauna Kea and Mauna Loa (circled in red) on the Big Island of Hawai’i early in the day on 03 December.

GOES-15 Visible (0.63 µm) images, with hourly surface reports [click to play animation]

GOES-15 Visible (0.63 µm) images, with hourly surface reports [click to play animation]

Hurricane Force low in the North Pacific Ocean

November 17th, 2016 |

GOES-15 Water Vapor (6.5 µm) images, with hourly surface and buoy/ship reports [click to play MP4 animation]

GOES-15 Water Vapor (6.5 µm) images, with hourly surface and buoy/ship reports [click to play MP4 animation]

GOES-15 (GOES-West) Water Vapor (6.5 µm) images (above; also available as a 52 Mbyte animated GIF) showed the development of a Hurricane Force low in the North Pacific Ocean during the 15 November – 17 November 2016 period. Surface analysis charts for this storm, produced by the Ocean Prediction Center, are shown below.

Surface analyses from 12 UTC on 15 November to 12 UTC on 17 November

Surface analyses from 12 UTC on 15 November to 12 UTC on 17 November

Although it was more of an oblique viewing angle, JMA Himawari-8 AHI Water Vapor (6.2 µm, 6,9 µm and 7.3 µm) images (below; also available as a 27 Mbyte animated GIF) provided a nice view of the storm on 15 November as it was intensifying to produce Hurricane Force winds.

JMA Hmawari-8 Water Vapor (6.2 µm, top; 6.9 µm, middle; 7.3 µm, bottom) images [click to play MP4 animation]

JMA Hmawari-8 Water Vapor (6.2 µm, top; 6.9 µm, middle; 7.3 µm, bottom) images [click to play MP4 animation]

Since the ABI instrument on GOES-R is nearly identical to the AHI, there will also be imagery from 3 water vapor bands (6.2 µm, 6.9 µm and 7.3 µm) available once GOES-R becomes operational (as GOES-16) in 2017.