Eruption of Bogoslof in Alaska’s Aleutian Islands

May 28th, 2017 |

Himawari-8 Visible (0.64 µm, left) and Infrared Window (10.4 µm, right) images, with hourly surface and ship reports plotted in yellow [click to play animation]

Himawari-8 Visible (0.64 µm, left) and Infrared Window (10.4 µm, right) images, with hourly surface and ship reports plotted in yellow [click to play animation]

The Bogoslof volcano in Alaska’s Aleutian Islands erupted around 2216 UTC on 29 May 2017. A comparison of Himawari-8 Visible (0.64 µm) and Infrared Window (10.4 µm) images (above; MP4) showed the volcanic cloud as it drifted north/northeastward.

A very oblique view of the volcanic cloud was captured by Korean COMS-1 satellite at 2315 UTC (below).

COMS-1 Visible (0.67 µm) images, with surface observations plotted in yellow [click to enlarge]

COMS-1 Visible (0.67 µm) images, with surface observations plotted in yellow [click to enlarge]

Himawaari-8 false-color images from the NOAA/CIMSS Volcanic Cloud Monitoring site (below) revealed the initial signature of a volcanic cloud — however, this signature became less distinct after about 02 UTC on 29 May.

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

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

A different type of Himawari-8 false-color imagery (below) makes use of the 8.5 µm spectral band, which can help to infer the presence of sulfur dioxide within a volcanic cloud feature. A similar 8.4 µm band is available from the ABI instrument on the GOES-R series of satellites.

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

3Himawari-8 false-color images [click to play animation]

A blend of Himawari-8 Infrared Window (10.4 µm) and radiometrically-retrieved Ash Cloud Height is shown below; the maximum ash cloud height was generally in the 10-12 km (33,000-39,000 feet above sea level) range (dark blue color enhancement). A volcanic ash signal was no longer apparent after 2320 UTC — this was likely due to enhanced ash particle removal via water (both liquid and ice) related processes.

Himawari-8 Infrared Window (10.4 µm) images and Ash Cloud Height retrievals [click to play animation]

Himawari-8 Infrared Window (10.4 µm) images and Ash Cloud Height retrievals [click to play animation]

A DigitalGlobe WorldView image at 2234 UTC (below) provided remarkable detail of the Bogoslof volcanic cloud shortly after the eruption began.


Blowing Dust over northern Montana

May 24th, 2017 |

GOES-16 Visible Imagery (0.64 µm) from 1707 through 1802 UTC on 24 May 2017 (Click to enlarge)

GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing

The strong pressure gradient around a Low Pressure system over Alberta and Saskatchewan caused strong winds across northern Montana on 24 May 2017, and blowing dust was the result, especially in Hill and Blaine Counties. The visible animation, above, from 1707 to 1802 UTC on 24 May, shows a faint hazy signature along the border of Canada.  The emphasis is on the word ‘faint’ — it is very difficult to pick out the signature unless you know it’s there already  (Thanks to MIC Tanja Fransen at WFO Glasgow for alerting us to this event).  The ‘Blue’ Visible band animation (below) similarly shows the dust, but it is not distinct in this band either.  (*Note* — part of this, of course, is because the default enhancement for visible imagery has been used.  If the ‘low light’ enhancement is applied, the dust signature is more apparent. This visible animation from 1502-2122, courtesy Tanja Fransen, more obviously shows the dust).

GOES-16 Visible Imagery (0.47 µm) from 1707 through 1802 UTC on 24 May 2017 (Click to enlarge)

Brightness Temperature Difference products are routinely available in AWIPS. The Split-Window Difference (SWD), below, shows the difference between the ‘Clean Infrared Window’ (10.33 µm) and the ‘Dirty Infrared Window’ (12.3 µm) (‘Clean’ and ‘Dirty’ referring to a little and more, respectively, water vapor absorption) has historically been used to detect dust: dust will absorb 10.33 µm radiation but it will not absorb 12.3 µm radiation, thus the SWD can highlight regions of dust.  However, that difference is also influenced by water vapor above the dust, and by the type of dust being lofted.

Split Window Difference (10.33 µm – 12.2 µm) from 1707 to 1802 UTC, 24 May 2017 (Click to enlarge)

The Cloud Phase Difference (8.5 µm – 11.2 µm) also can highlight regions of dust, and for this case the signal of dust was a bit more distinct.

Cloud Phase Brightness Temperature Difference (8.5 µm – 11.2 µm) from 1707 to 1802 UTC, 24 May 2017 (Click to enlarge)

Surface data plotted over the 0.64 µm at 1712 UTC, below, show the strong winds in the region (Here is an image at 1802 UTC). Visibilities in the areas of blowing dust were reported to be near zero.

GOES-16 Visible (0.64 µm) at 1712 UTC and 1700 UTC surface observations (Click to enlarge)

A Terra MODIS true-color Red/Green/Blue (RGB) image at 1745 UTC, below, revealed that the source of some of the most dense dust plumes appeared to be uncultivated fields located north and northeast of Havre.

Terra MODIS true-color RGB image (Click to enlarge)

Terra MODIS true-color RGB image (Click to enlarge)

(Added: Stuart Lawrence, south of Rosetown in west-central Saskatchewan, tweeted out this video that showed the dust storm there. He reported winds up to 98 km/hour). Here is another image of the dust in Saskatchewan.

The GOES Aerosol/Smoke Products (GASP) showed a noticeable signal for this dust. Here is a large-scale animation from 1315-2145 UTC, with a closer view from 1015-2345 UTC here)

Mud Creek landslide along the California coast

May 22nd, 2017 |

As seen in the Tweet above from NWS San Francisco Bay Area, a major landslide occurred along the California coast in the Big Sur area (at Mud Creek) during the nighttime hours on 20 May 2017. A large portion of coastal Highway 1 was closed by the massive amount of debris.

A timely overpass of the Landsat-8 satellite at 1840 UTC on 22 May (along with the cooperation of a gap in cloudiness) provided 30-meter resolution false-color Red/Green/Blue (RGB) imagery (source) which showed the landslide debris extending off the coast and into the adjacent nearshore water of the Pacific Ocean (below). Before/after photos of the landslide site can be seen here.

Landsat-8 false-color images [click to enlarge]

Landsat-8 false-color images [click to enlarge]

text

Fog/stratus in the Strait of Juan de Fuca

May 20th, 2017 |

** The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. **

As seen in a Tweet from NWS Seattle/Tacoma (above), a plume of fog/stratus moved rapidly eastward through the Strait of Juan de Fuca on 20 May 2017. A closer view of GOES-16 Visible (0.64 µm) images (below; also available as an MP4 animation) shows the formation of “bow shock waves” as the leading edge of the low-level fog/stratus plume encountered the sharply-angled land surface of Whidbey Island at the far eastern end of the Strait near sunset — surface observations indicated that the visibility at Naval Air Station Whidbey Island was reduced to 0.5 mile just after the time of the final 0327 UTC image in the animation.

GOES-16 Visible (0.64 µm) images, with hourly plots of surface reports [click to play animation]

GOES-16 Visible (0.64 µm) images, with hourly plots of surface reports [click to play animation]

A Suomi NPP VIIRS Visible (0.64 µm) image with RTMA surface winds (below) indicated that westerly/northwesterly wind speeds were generally around 15 knots at 21 UTC (just after the primary fog/stratus plume began to move into the western end of the Strait). Four hours later, there was a northwesterly wind gust of 27 knots at Sheringham, British Columbia (CWSP).

Suomi NPP VIIRS Visible (0.64 µm) images, with RTMA surface winds plotted in cyan [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) images, with RTMA surface winds plotted in cyan [click to enlarge]

During the following nighttime hours, a Suomi NPP VIIRS infrared Brightness Temperature Difference (11.45 – 3.74 µm) “Fog/Stratus Product” image at 0910 UTC (below) revealed that the fog/stratus plume covered much of the Strait (especially along the Washington coast), and that the leading edge had begun to spread both northward and southward from Whidbey Island. In addition, note the presence of a linear ship track (darker red enhancement) extending southwestward from Cape Flattery.

Suomi NPP VIIRS Infrared brightness temperature difference (11.45 - 3.74 µm)

Suomi NPP VIIRS infrared Brightness Temperature Difference (11.45 – 3.74 µm) “Fog/Stratus Product” image, with RTMA surface winds plotted in cyan [click to enlarge]

Bill Line (NWS Pueblo) showed the nighttime fog/stratus monitoring capability of a GOES-16 infrared Brightness Temperature Difference product:


On a side note, in the upper right portion of the GOES-16 (as well as the VIIRS) visible images one can also see the hazy signature of glacial sediment  flowing from the Fraser River westward into the Strait of Georgia. Longer-term changes in the pattern of this glacial sediment are also apparent in a comparison of Terra MODIS true-color Red/Green/Blue (RGB) images (source) from 20 April, 07 May and 20 May 2017 (below).

 

Terra MODIS true-color RGB images [click to enlarge]

Terra MODIS true-color RGB images [click to enlarge]