GOES-15 0.63 µm visible channel images (click image to play animation)

GOES-15 0.63 µm visible channel images (above; click image to play animation) showed a distinct hazy plume streaming southeastward from the Katmai volcano area in Alaska on 22 September 2013. This was a signature of re-suspended volcanic ash — a deep layer of ash has remained on the ground near the volcano following the massive 1912 eruption — which was carried aloft by strong winds on the back side of a deep area of low pressure over the Gulf of Alaska (below).

Suomi NPP VIIRS 0.7 µm Day/Night Band image

A closer view using a sequence of four Suomi NPP VIIRS 0.7 µm Day/Night Band images (below) showed the evolution of the ash plume as it moved over southeastward over Kodiak Island and then out over the Gulf of Alaska. Winds at Kodiak (station identifier PADQ) gusted as high as 55 knots or 63 mph. With limited snow cover and strong winds (which were enhanced by local terrain effects), the surface volcanic ash was easily lofted to great heights.

Suomi NPP VIIRS 0.7 µm Day/Night Band images

An image of a MODIS-based NOAA/STAR/CIMSS Volcanic Ash Height product is shown in combination with the Volcanic Ash Advisory that was issued by the Anchorage Volcanic Ash Advisory Center (below).

MODIS Ash Height product with Volcanic Ash Advisory

MODIS Ash Height product

A sequence of three MODIS Volcanic Ash Height product images (above) suggested that the average height of the re-suspended ash plume was around 9,000 – 11,000 feet. A vertical profile of CALIPSO satellite-based lidar data near the source of the ash plume (below; courtesy of Mike Pavolonis, NOAA/NESDIS/STAR) indicated that the top of the plume was around 3.5 km or 11,000 feet (at 12:57 UTC, near latitude/longitude 58 N / 155 W).

CALIPSO total attenuated backscatter

The corresponding MODIS Ash Mass Loading product (below) indicated values of 2-3 tons per square kilometer existed over much of the ash plume.

MODIS Ash Mass Loading product

Finally, the corresponding MODIS Ash Mass Effective Radius product (below) showed that much of the plume likely consisted of particles with radii in the 4-6 µm range, with a maximum value of 8.33 µm.

MODIS Ash Mass Effective Radius product

Additional information on the NOAA/UW-CIMSS GOES-R Volcanic Ash Products shown above can be found in this Java-based VISITview lesson (a separate Lesson Playback Control window will open to assist in viewing the lesson content).

===== 23 September Update =====

Suomi NPP VIIRS 0.7 µm Day/Night Band image

On the following day (23 September), a Suomi NPP VIIRS 0.7 µm Day/Night Band image (above) showed that the resuspended Katmai ash plume was still present, but was much less expansive than what was seen on 22 September.

Hat tip to Mark Ruminski of the NOAA/NESDIS Satellite Services Division for bringing this interesting event to our attention!

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MTSAT-2 10.8 µm IR images (click image to play animation)

McIDAS images of MTSAT-2 10.8 µm IR channel data (above; click image to play animation) showed Super Typhoon Usagi in the West Pacific Ocean as it continued to move northwestward across the Philippine Sea. Note the slight amount of “trochoidal wobble” seen in the path of the eye. The coldest IR brightness temperature seen on the MTSAT-2 IR images was -92º C at 12:32 UTC. At the time of these images, advisories issued by the Joint Typhoon Warning Center listed the maximum sustained winds at 140 knots, with gusts to 170 knots; at its peak intensity, Usagi had an estimated lowest pressure of 882 hPa, making it the most intense tropical cyclone so far in 2013.

TMI and SSM/I 85 GHz microwave brightness temperature images

From the CIMSS Tropical Cyclones site, a comparison of 85 GHz microwave images from the TRIMM Microwave Imager (TMI) at 10:35 UTC and the DMSP SSM/I at 19:13 UTC (above) displayed a very small ring of high brightness temperatures surrounding the “pinhole eye”.

MIMIC-TC morphed microwave images (below; click image to play animation) showed a well-defined closed eyewall during much of the early part of the day on 19 September.

MIMIC-TC morphed microwave imagery (click image to play animation)

MTSAT-2 IR image with AASCAT scatterometer surface winds

Scatterometer surface winds from the ASCAT instrument at 13:17 UTC  (above) and the OSCAT instrument at 15:10 UTC  (below) showed the large areal coverage of strong winds around the center of Usagi.

MTSAT-2 IR image with OSCAT scatterometer surface winds

 ===== 20 September Update =====

MTSAT-2 0.67 µm visible channel images (click image to play animation)

MTSAT-2 0.67 µm visible channel images (above; click image to play animation) showed the detailed structure of the compact eye of Super Typhoon Usagi.

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Suomi NPP VIIRS 11.45 µm IR channel and 0.7 µm Day/Night Band images

AWIPS images of Suomi NPP VIIRS 11.45 µm IR channel and 0.7 µm DayNight Band data showed Hurricane Manuel centered just off the west coast of Mexico at 07:54 UTC or 12:54 AM local time (above) and at 09:37 UTC or 2:27 AM local time (below) on 19 September 2013. Manuel had just reached hurricane intensity several hours earlier. In the 07:54 UTC images above, hints of an eye feature were present on both the IR and the Day/Night Band. In the 09:37 UTC images below, evidence of offshore convective bursts could be seen (many of which exhibited cloud-top IR brightness temperatures of -80º C and colder, violet color enhancement).

Suomi NPP VIIRS 11.45 µm IR channel and 0.7 µm Day/Night Band images

Manuel rapidly lost organization and intensity upon moving inland over the rugged terrain of the Sierra Madre Occidental, becoming a remnant area of low pressure over northern Mexico at the end of the day on 19 September.

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Before (07 September) and after (17 September) MODIS false-color Red/Green/Blue (RGB) images

A comparison of “before” (07 September 2013) and “after” (17 September 2013) 250-meter resolution MODIS false-color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (above) showed a dramatic change in the appearance of the South Platte River that flows northeastward across northeastern Colorado. Following the record-setting rainfall across much of the Front Range of Colorado (previous blog post), much of this water (darker blue in appearance on the RGB images) was being carried across northeastern Colorado by the South Platte River and its tributaries.

Hydrographs for 3 different locations along the South Platte River in Colorado (Kersey, Balzac, and Julesburg, below) showed the actual and forecast maximum river crests — note that the peak river crest of 18.79 feet at Kersey eclipsed the previous record of 11.7 feet set in 1973.

A comparison of AWIPS images of consecutive overpasses (1 hour and 44 minutes apart) of Suomi NPP VIIRS 1.61 µm near-IR data on 14 September (below) appeared to indicate that the dark signal of the leading edge of the South Platte River flooding could be seen moving rapidly southeastward along that particular portion of the river.

The Suomi NPP VIIRS 1.61 µm image at 19:58 UTC on 17 September (below) showed that the dark signature of flooding along the South Platte River had nearly reached the Colorado/Nebraska border.

Note that the South Platte River flooding is not evident on the corresponding 0.64 µm VIIRS visible channel image (below) — this is due to the fact that there is not much contrast between the sediment-rich water and the adjacent dry soils (much of northeastern Colorado remains in a drought).

Suomi NPP VIIRS 0.64 µm visible channel and 1.61 µm near-IR channel images

===== 18 September Update =====

Suomi NPP VIIRS 1.61 µm near-IR images (17 vs 18 September)

A comparison of AWIPS images of Suomi NPP VIIRS 1.61 µm near-IR images (above) showed the progression of the leading edge of the flooding along the South Platte River in a 24-hour period (from 19:58 UTC on 17 September to 19:42 UTC on 18 September). The dark signal of river flooding had extended northeastward across the Nebraska border.

The hydrograph for Julesburg in far northeastern Colorado (below) showed that the river had already crested above the previous record stage of 10.4 feet.

Julesburg, Colorado hydrograph

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