Re-suspended volcanic ash from the Novarupta volcano in Alaska

September 29th, 2014
GOES-15 0.63 µm visible channel images (click to play animation)

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

McIDAS images of GOES-15 0.63 µm visible channel data (above; click image to play animation) showed the hazy signature of a plume of re-suspended volcanic ash originating from the region of the Novarupta volcano in Alaska, moving southeastward over the Shelikof Strait toward Kodiak Island on 29 September 2014. The 1912 eruption of Novarupta left a very deep deposit of volcanic ash, which often gets lofted by strong winds in the early Autumn months before snowfall covers the ash (another example occurred on 22 September 2013). Surface winds gusted as high as 30 knots at regional reporting stations, with numerical models estimating terrain-enhanced winds as high as 40-50 knots over the Novarupta ash field.

An AWIPS II image of POES AVHRR 0.86 µm visible channel data (below) showed the ash plume at 22:46 UTC; a pilot report at 22:45 UTC indicated that the top of the ash plume was between 4000 and 6000 feet above ground level.

POES AVHRR 0.86 µm visible channel image, with METAR surface reports and Pilot reports (PIREPs)

POES AVHRR 0.86 µm visible channel image, with METAR surface reports and Pilot reports (PIREPs)

A sequence of 3 Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images from the SSEC RealEarth web map server (below) indicated that the re-suspended ash plume had been increasing in areal extent during that period.

Suomi NPP VIIRS true-color images from 27, 28, and 29 September

Suomi NPP VIIRS true-color images from 27, 28, and 29 September

A sequence of 4-panel products from the NOAA/CIMSS Volcanic Cloud Monitoring site (below) shows False-color images, Ash/dust cloud height, Ash/dust particle effective radius, and Ash/dust loading (derived from either Terra/Aqua MODIS or Suomi NPP VIIRS data).

4-panel MODIS/VIIRS products: False color image; Ash/dust cloud height; Ash/dust particle effective radius; Ash/dust loading

4-panel MODIS/VIIRS products: False color image; Ash/dust cloud height; Ash/dust particle effective radius; Ash/dust loading

Hat tip to Mark Ruminski (NOAA/NESDIS) for alerting us to this event.

The King Fire in California

September 19th, 2014
Suomi NPP VIIRS true-color images

Suomi NPP VIIRS true-color images

The King Fire began burning in central California (between Sacramento and Lake Tahoe) during the evening hours on 13 September 2014. A sequence of daily (12-19 September) Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images from the SSEC RealEarth web map server site (above) showed that as the prevailing southwesterly wind pattern switched to easterly on 19 September, there was a major change in the transport of smoke from the King Fire. The final image in the series zooms out to show how much of central California had become over-run with thick smoke.

A comparison of AWIPS-II images of Suomi NPP VIIRS 0.7 µm Day/Night Band and 3.74 µm shortwave IR image at 09:18 UTC or 2:18 AM local time (below) revealed the bright glow of the large fire complex, along with the large fire “hot spot” signature (black to yellow to red color enhancement).

Suomi NPP VIIRS 0.7 µm Day/Night Band and 3.74 µm shortwave IR images

Suomi NPP VIIRS 0.7 µm Day/Night Band and 3.74 µm shortwave IR images

Suomi NPP VIIRS 3.74 µm shortwave IR images during the overnight hours (just after 2 AM local time) on 17 and 18 September (below) showed the dramatic northeastward advance of the fire hot spot signature during that 24-hour period. Smoke from the fire was reducing the surface visibility to 3-4 miles as far to the northeast as Lovelock (KLOL) and Fallon (KNFL) in Nevada.

Suomi NPP VIIRS 3.74 µm shortwave IR images

Suomi NPP VIIRS 3.74 µm shortwave IR images

MODIS false-color images show areas of flooding in Montana

August 26th, 2014
Before (12 August) and after (26 August) MODIS false-color RGB images

Before (12 August) and after (26 August) MODIS false-color RGB images

Some locations in northeastern Montana received up to 7-8 inches of rainfall over a 5-day period (NWS Glasgow rainfall map), which led to flooding in many areas. A comparison of before (12 August) and after (26 August) 250-meter resolution MODIS false-color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (above) showed the areal extent of flooding (cyan to darker blue areas on the 26 August image). The RGB images use MODIS bands 7/2/1 to help highlight the areas of of floodwater.

The maps below show the total observed rainfall, the departure from normal, and the percent of normal for the 7-day period ending on 26 August.

Observed 7-day rainfall

Observed 7-day rainfall

7-day rainfall departure from normal

7-day rainfall departure from normal

7-day rainfall percent of normal

7-day rainfall percent of normal

The effect of wind shear on Tropical Storm Karina

August 24th, 2014
GOES-15 0.63 µm visible channel  images (click to play Animated GIF)

GOES-15 0.63 µm visible channel images (click to play Animated GIF)

GOES-15 0.63 µm visible channel images (Animated GIF | MP4 movie | YouTube video | QuickTime movie) showed the decoupling of the upper-level and lower-level circulations of Tropical Storm Karina in the East Pacific Ocean on 24 August 2014. This decoupling was caused by strong wind shear along the western periphery of Category 5 Hurricane Marie, which was located to the east-southeast of Karina (large-scale view). Kudos to Dennis Chesters (NASA/Goddard) for bringing this interesting case to our attention (and providing the QuickTime movie linked to above).

The corresponding GOES-15 10.7 µm IR channel images (Animated GIF | MP4 movie | YouTube video) showed the cold clouds (red to black to white to purple color enhancement) associated with the upper-level circulation moving northward and quickly dissipating; the signature of the warmer clouds (darker cyan color enhancement) associated with the lower-level circulation can also be seen emerging from beneath the cold cloud shield and moving eastward.

GOES-15 10.7 µm IR channel images (click to play Animated GIF)

GOES-15 10.7 µm IR channel images (click to play Animated GIF)

A closer view provided by a Suomi NPP VIIRS true-color Red/Green/Blue (RGB) image from the SSEC RealEarth web map server (below) showed the separation of the upper-level and lower-level circulations around 21:53 UTC.

Suomi NPP VIIRS true-color RGB image

Suomi NPP VIIRS true-color RGB image

A sequence of 4 images (15, 18, 21, and 00 UTC) from the CIMSS Tropical Cyclones site (below) shows GOES-15 6.5 µm water vapor channel images with overlays of deep-layer wind shear (derived from satellite winds). To the east of Karina (which was located in the center of the images), the large anticylcone aloft associated with Category 5 Hurricane Marie can be seen, with increasing vales of southeasterly wind shear moving over Karina.

GOES-15 6.5 µm water vapor images with overlays of deep layer wind shear

15 UTC GOES-15 6.5 µm water vapor images with overlays of deep layer wind shear

The 3 image comparisons below show the separation of the centers of upper-level divergence (yellow) and lower-level convergence (cyan) as the decoupling process was occurring at 18 UTC, 21 UTC, and 00 UTC.

18 UTC GOES-15 6.5 µm water vapor image with upper-level divergence (yellow) and GOES-15 10.7 µm IR image with lower-level convergence (cyan)

18 UTC: GOES-15 6.5 µm water vapor image with upper-level divergence (yellow) and GOES-15 10.7 µm IR image with lower-level convergence (cyan)

21 UTC: GOES-15 6.5 µm water vapor image with upper-level divergence (yellow) and GOES-15 10.7 µm IR image with lower-level convergence (cyan)

21 UTC: GOES-15 6.5 µm water vapor image with upper-level divergence (yellow) and GOES-15 10.7 µm IR image with lower-level convergence (cyan)

00 UTC: GOES-15 6.5 µm water vapor image with upper-level divergence (yellow) and GOES-15 10.7 µm IR image with lower-level convergence (cyan)

00 UTC: GOES-15 6.5 µm water vapor image with upper-level divergence (yellow) and GOES-15 10.7 µm IR image with lower-level convergence (cyan)

===== 25 August Update =====

GOES-15 0.63 µm visible channel images, with Metop ASCAT surface scatterometer winds

GOES-15 0.63 µm visible channel images, with Metop ASCAT surface scatterometer winds

Even though the southeastward-moving low-level circulation of Karina had been downgraded to a Tropical Depression with 30 knot winds, there was still an impressive burst of convection just west of the center as it began to move back over warmer water on 25 August. Metop ASCAT surface scatterometer winds (above) showed a small pocket of winds in the 30.0-39.9 knot range (green wind barbs) at 18:29 UTC.

There were also some Tropical Overshooting Top (TOT) targets detected within the convective burst (below); TOT symbols: Red = 0-1 hour previous, Green = 1-2 hours previous, Blue = 2-3 hours previous.

GOES-15 Infrared - Water Vapor difference product, and Tropical Overshooting Tops product (TOT symbols: Red = 0-1 hour previous, Green = 1-2 hours previous, Blue = 2-3 hours previous)

GOES-15 Infrared – Water Vapor difference product, and Tropical Overshooting Tops product (TOT symbols: Red = 0-1 hour previous, Green = 1-2 hours previous, Blue = 2-3 hours previous)