Yarnell Hill Fire in Arizona

June 30th, 2013 |
GOES-15 0.63 µm visible channel images (click image to play animation)

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

The Yarnell Hill Fire (InciWeb) was a relatively small wildfire that was started by lightning from a dry thunderstorm southwest of Prescott, Arizona on 28 June 2013. However, fire conditions became more favorable for growth on 30 June, as surface air  temperatures rose above 100 F across the area with low relative humidity values. During the afternoon hours, GOES-15 0.63 µm visible channel images (above; click image to play animation; also available as a QuickTime movie) showed that a line of thunderstorms developed over northwestern Arizona, and moved toward the southwest (the red circle highlights the general area of the Yarnell fire). It is likely that strong surface winds associated with a thunderstorm outflow boundary (nearby surface mesonet data) caused rapid growth and an abrupt change in direction of the fire, which tragically killed 19 firefighters who attempted to shelter in place (for additional details, see the Wildfire Today site).

On the GOES-15 visible imagery, a smoke plume became more obvious after 16:45 UTC, with the first formation of pyrocumulus clouds evident at 21:00 and 21:30 UTC. As the cloud shield of the thunderstorm line moved over the fire, the images revealed the development of a pyrocumulonimbus (pyroCb) cloud which exhibited a pronounced overshooting top at 23:45 UTC.

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

Taking a look at the period of pyroCb formation, the overshooting plume and pronounced overshooting top could be seen spreading southward (due to northerly winds aloft, as shown on Flagstaff AZ rawinsonde data) on the GOES-15 0.63 µm visible images (above) — and this pyroCb plume and overshooting top appeared warmer/darker on GOES-15 3.9 µm shortwave IR images (below), which indicated that the plume was comprised of smaller particles which were more efficient reflectors of solar radiation.

GOES-15 3.9 µm shortwave IR images (click image to play animation)

GOES-15 3.9 µm shortwave IR images (click image to play animation)

On GOES-15 10.7 µm longwave IR images (below), the coldest cloud top IR brightness temperature of -65 C (darker red color enhancement) was associated with the overshooting top at 23:45 UTC.

GOES-15 10.7 µm longwave IR images (click image to play animation)

GOES-15 10.7 µm longwave IR images (click image to play animation)

Shown below is a comparison of the 23:45 UTC images of GOES-15 visible, shortwave IR, and longwave IR images.

Comparison of 23:45 UTC GOES-15 visible, shortwave IR, and longwave IR images

Comparison of 23:45 UTC GOES-15 visible, shortwave IR, and longwave IR images

A comparison of Suomi NPP 0.64 µm visible channel and 11.45 µm IR channel images at 21:22 UTC (below) showed the Yarnell fire “hot spot”  (dark black pixels), with some pyrocumulus clouds beginning to form to the east/northeast of the fire source (due to strong southwesterly winds in the boundary layer).

Suomi NPP VIIRS 0.64 µm visible and 11.45 µm longwave IR images

Suomi NPP VIIRS 0.64 µm visible and 11.45 µm longwave IR images

The corresponding Suomi NPP VIIRS true-color image is shown below, visualized using the SSEC Web Map Server. Again, the smoke plume from the fire can be seen, along with the development of pyrocumulus clouds to the east/northeast.

Suomi NPP VIIRS true-color image

Suomi NPP VIIRS true-color image

 

Flagstaff, Arizona WSR-88D radar base reflectivity and volume of 13.5 dBZ reflectivity isosurface (click image to play animation)

Flagstaff, Arizona WSR-88D radar base reflectivity and volume of 13.5 dBZ reflectivity isosurface (click image to play animation)

Volumetric displays of Flagstaff, Arizona WSR-88D radar base reflectivity and spectrum width are shown above and below, respectively (radar data visualized using GR2Analyst software, courtesy of Jordan Gerth, CIMSS). The viewing perspective is looking from the northwest, so Prescott is located in the left corner of the data cube, and the Yarnell fire with its growing pyrocumulus (pyroCu) and pyrocumulonimbus (pyroCb) cloud is located in the right corner of the data cube.

The blue-shaded isosurface of the 13.5 dBZ base reflectivity (from 22:42 to 23:48 UTC) showed the upward pulsing of the pyroCu and finally the pyroCb, which grew upward past an altitude of 40,000 feet on the final image (23:48 UTC, about the time that the prominent overshooting top was seen on the 23:45 UTC GOES-15 visible image).

The Doppler radar spectrum width is shown from 23:34 to 23:48 UTC. This parameter represents the amount of variance in the velocity field. Note the higher spectrum width values (darker orange shading) associated with the growth of the pyroCb cloud over the Yarnell fire — this was likely a result of the variety of particles (biomass burning particles, supercooled water droplets, ice crystals) moving upward at different velocities because of their differing size and shape characteristics.

Flagstaff, Arizona WSR-88D radar spectrum width (click image to play animation)

Flagstaff, Arizona WSR-88D radar spectrum width (click image to play animation)

 

 

Eruption of the Pavlof Volcano in Alaska

June 25th, 2013 |
GOES-15 0.63 µm visible channel images (click image to play animation)

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

According to the Alaska Volcano Observatory, the Pavlof Volcano began to experience a vigorous eruption around 06:50 UTC on 25 June 2013. As daylight arrived a few hours later, the volcanic plume (which contained some ash) was evident on McIDAS images of 1-km resolution GOES-15 0.63 µm visible channel data (above; click image to play animation). The high-altitude portion of the volcanic plume was estimated to be around 28,000 feet above sea level — this darker-gray plume could be seen drifting northwestward above the lower-altitude clouds over the southern Bering Sea.

During the early morning, a warm thermal anomaly of 42.85º C (darker black enhancement) could be seen at the location of the volcano on a 4-km resolution GOES-15 3.9 µm shortwave IR channel image at 14:45 UTC (below).

GOES-15 3.9 µm shortwave IR channel image

GOES-15 3.9 µm shortwave IR channel image

Even with a very large oblique viewing alngle from the Japanese MTSAT-2 satallite, the volcanic cloud and plume rising from the Pavlof Volcano (denoted by the letter “P”) could be seen on a visible channel image at 15:01 UTC (below).

MTSAT-2 visible image

MTSAT-2 visible image

Flooding in Alberta, Canada

June 21st, 2013 |
GOES-15 6.5 µm water vapor channel images with plots of surface weather (click image to play animation)

GOES-15 6.5 µm water vapor channel images with plots of surface weather (click image to play animation)

Very heavy rainfall in much of southwestern Alberta (upwards of 200 mm or 7.9 inches) caused severe flooding in the Calgary (YYC) area beginning on 19 June and 20 June 2013. A sequence of McIDAS images of hourly GOES-15 6.5 µm water vapor channel data (above; click image to play animation) showed three distinct pulses of moisture that moved across the YYC region during the 18 June – 21 June period. The circulation around an area of low pressure that was moving slowly across the northwestern US (below) allowed deep tropospheric moisture to be transported eastward against the high terrain of the Rocky Mountains, which was a factor in producing such heavy precipitation amounts.

Water vapor image composites + ECMWF model 500 hPa geopotential heights

Water vapor image composites + ECMWF model 500 hPa geopotential heights

 

Blended Total Precipitable Water product

Blended Total Precipitable Water product

The Blended Total Precipitable Water product (above) showed TPW values as high as 31 mm or 1.2 inches over much of the region on the morning of 20 June — these TPW values were 190-200% above normal for this area and this time of the year (below).

Blended Total Precipitable Water Percent of Normal product

Blended Total Precipitable Water Percent of Normal product

Summer Solstice in Alaska

June 21st, 2013 |
GOES-15 0.63 µm visible channel images (click image to play animation)

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

GOES-15 (GOES-West) 0.63 µm visible channel images (above; click image to play animation) showed the cloud features over much of Alaska on 21 June 2013 (the day of the summer solstice). Record heat had been occurring across much of Alaska during the previous week, and Barrow (BRW) had a daily record high temperature of 62 F on 20 June. Note that there were numerous thunderstorms that developed over the Brooks Range and even over the North Slope regions of Alaska — on 20 June, over 4000 cloud-to-ground lightning strikes were detected. The haziness seen early in the animation was due to widespread smoke from wildfires that had been burning in southwestern Alaska a few days earlier.