Rim Fire in California

August 22nd, 2013 |
Suomi NPP VIIRS 3.74 µm shortwave IR and 0.7 µm Day/Night Band images

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

A night-time (10:01 UTC or 3:01 AM local time) comparison of AWIPS images of Suomi NPP VIIRS 3.74 µm shortwave IR and 0.7 µm Day/Night Band data (above) showed signatures of the Rim Fire which had been burning since 17 August near Yosemite National Park in California. On the shortwave IR image, numerous “hot spots” (black to yellow to red enhancement) revealed the location of larger, hotter fires that were burning along the periphery of the large burn scar. The Day/Night Band image showed (1) a bright white glow over the area of active fires, and (2) light gray signatures of the primary middle to upper altitude smoke plume that was moving northward, in addition to an area of lower altitude smoke that was moving westward toward lower elevations. Due to ample illumination from a 98% full waning gibbous Moon phase, the “visible image at night” capability of the Day/Night Band proved to be useful for identifying the location of the smoke plumes.

Later that day during the afternoon hours the Rim Fire exhibited very active growth, nearly doubling in size to over 105,000 acres (Wildfire Today | InciWeb). A comparison of 250-meter resolution MODIS true-color and false-color images from the SSEC MODIS Today site (below) showed the large and very dense smoke plume at 18:42 UTC (11:42 AM local time).

MODIS true-color and false-color Red/Green/Blue (RGB) images

MODIS true-color and false-color Red/Green/Blue (RGB) images

The GOES-14 satellite had been placed into Super Rapid Scan Operations for GOES-R (SRSO-R) mode, providing images at 1-minute intervals during the entire day. A sequence of these GOES-14 SRSO-R 0.63 µm visible channel images (below; click image to play animation) showed that the initial northward motion of the smoke plume began to transition to a more northeasterly motion after about 17 UTC. This was due to a shift in the winds aloft as a semi-stationary cut-off low just west of the coast of California began to move northward during the day.

GOES-14 0.63 µm visible channel images (click image to play animation)

GOES-14 0.63 µm visible channel images (click image to play animation)

The  change in the winds aloft which allowed the smoke plume to begin drifting more toward the northeast prompted the National Weather Service forecast office at Reno, Nevada to amend their forecasts for some areas to include smoke and haze (complete AFD):

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
207 PM PDT THU AUG 22 2013

ONLY MINOR CHANGES MADE TO ONGOING FORECAST WITH THE GREATEST CHANGE TO ADD SMOKE AND HAZE DUE TO MULTIPLE ONGOING WILDFIRES, THE GREATEST CONTRIBUTOR BEING THE RIM FIRE JUST WEST OF YOSEMITE. THE UPPER LEVEL LOW WHICH HAS BROUGHT US PLENTY OF THUNDERSTORMS THE PAST FEW DAYS IS BEGINNING TO LIFT NORTH WITH A DRIER  SOUTHWEST FLOW RESULTING ACROSS NORTHEAST CALIFORNIA AND NORTHWEST NEVADA.

Surface visibilities at locations such as South Lake Tahoe were reduced as low as 1.25 miles once the smoke plume began to move over that area.

===== 23 August Update =====

Night-time Suomi NPP VIIRS 3.7 µm shortwave IR images on 21, 22, and 23 August

Night-time Suomi NPP VIIRS 3.7 µm shortwave IR images on 21, 22, and 23 August

Suomi NPP VIIRS 3.74 µm shortwave IR images on 3 consecutive nights (21, 22, and 23 August) showed the rapid increase in size of the Rim Fire (above).

Another example of smoke from the Rim Fire being detected during the night-time hours can be seen at 09:43 UTC or 2:43 AM local time on 23 August (below). The VIIRS 0.7 µm Day/Night Band image revealed a number of discrete plumes of smoke streaming northward, then northeastward toward the Lake Tahoe area. At South Lake Tahoe the surface visibility at the time of the image was 2 miles, but it decreased to 1/2 mile four hours later.

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

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

SRSO-R Imagery of convection over the Upper Midwest

August 21st, 2013 |
GOES-14 0.63 µm visible channel images (click image to play animation)

GOES-14 0.63 µm visible channel images (click image to play animation)

A cold front moving through Wisconsin triggered severe convection (SPC storm reports) on 21 August 2013. GOES-14 SRSO-R data gives a compelling look at the convective development at 1-minute intervals. Because of the satellite position, the rear inflow into the convection near Rice Lake, WI, is very apparent.

It is useful to compare the SRSO-R views of the convection from GOES-14 (30-second imagery will be available with GOES-R) to the routine scanning strategy used by GOES-13. That comparison is shown below. Routine scanning is unable to capture the very dynamic nature of rapidly evolving convection.

GOES-14 (left, SRSO-R) and GOES-13 (right) 0.63 µm visible channel images (click image to play animation)

GOES-14 (left, SRSO-R) and GOES-13 (right) 0.63 µm visible channel images (click image to play animation)

Even Rapid Scan Operations (RSO) imagery (GOES-13 was in RSO during this event) can also miss important details, especially at times when GOES-East is doing a full-disk scan (at 20:45 UTC, for example) and no imagery is available for 30 minutes. The loop below compares SRSO views of this system (top) to RSO (middle) to standard 15-minute scanning (bottom). GOES-R will have the capability simultaneously to scan globally and in designated mesoscale sectors.

GOES-14 (SRSO-R, top; RSO, middle; standard, bottom) 0.63 µm visible channel images (click image to play animation)

GOES-14 (SRSO-R, top; RSO, middle; standard, bottom) 0.63 µm visible channel images (click image to play animation)

GOES-13 Sounder DPI values of Lifted Index (click image to play animation)

GOES-13 Sounder DPI values of Lifted Index (click image to play animation)

GOES-13 sounder Derived Product Imagery (DPI) of the Lifted Index (above, available at this site) and Convective Available Potential Energy (below) readily shows the unstable airmass supporting the convection.

GOES-13 sounder Convective Available Potential Energy (CAPE) product (click image to play animation)

GOES-13 sounder Convective Available Potential Energy (CAPE) product (click image to play animation)

Total Precipitable Water (available at this site), below, shows moisture pooling along the approaching front.

GOES-13 Sounder DPI values of Total Precipitable Water

GOES-13 Sounder DPI values of Total Precipitable Water

First snowfall of the season in northeastern Alaska

August 21st, 2013 |
Suomi NPP VIIRS 11.45 µm IR channel images (click image to play animation)

Suomi NPP VIIRS 11.45 µm IR channel images (click image to play animation)

AWIPS images of Suomi NPP VIIRS 11.45 µm IR channel data (above; click image to play animation) showed the development of a cyclonic swirl of middle to high altitude clouds associated with an upper-level shortwave moving northward over northeastern Alaska on 20 August 2013. This disturbance helped to reinforce the northerly to northeasterly flow of unseasonably cold air across the Beaufort Sea and North Slope regions of Alaska, producing upslope winds along the Brooks Range — this scenario led to the first major snowfall of the season in northern Alaska, with eastern portions of the Brooks Range and North Slope regions receiving several inches of accumulation.

The first glimpse of snow cover appeared on a Suomi NPP VIIRS 0.7 µm Day/Night Band image at 11:57 UTC or 3:57 AM local time on 21 August (below), as clouds began to clear in the vicinity of Anaktuvuk Pass (PAKP) to Arctic Village (PARC) and points northward. The long and narrow bright streak seen over land in the western portion of the Day/Night Band image is the glow of the aurora borealis (note the lack of a signal there on the corresponding 11.45 µm IR channel image) — in contrast, the bright features seen over water in the eastern/northeastern portion of the Day/Night Band image were clouds becoming illuminated by the rising sun.

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

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

A mid-day comparison of Suomi NPP VIIRS 0.64 µm visible channel and false-color Red/Green/Blue (RGB) images at 20:14 UTC or 12:14 PM local time (below) revealed the areal extent of the fresh snow on the ground — new snow appeared as darker shades of red across the eastern Brooks Range and North Slope regions (in contrast to supercooled water droplet clouds, which appeared as varying shades of white). Snow depth reports ranged from 2-6 inches at 12 UTC. Note that clouds whose tops were composed of ice crystals also appeared as varying shades of red on the RGB image.

Suomi NPP VIIRS 0.64 µm visible channel and false-color Red/Green/Blue (RGB) images

Suomi NPP VIIRS 0.64 µm visible channel and false-color Red/Green/Blue (RGB) images

A comparison of two consecutive VIIRS false-color RGB images at 20:14 and 21:53 UTC (below) indicated that the outer edges of the snow cover were slowly melting, as surface air temperatures were able to recover into the 30s and 40s F over that region. With the combination of fresh snow cover, clearing skies, and light winds the morning low on 21 August was 23º F at Anaktuvuk Pass (PAKP); their high temperature on 20 August during the period of accumulating snow was just 36º F.

Suomi NPP VIIRS false-color Red/Green/Blue (RGB) images at 20:14 and 21:53 UTC

Suomi NPP VIIRS false-color Red/Green/Blue (RGB) images at 20:14 and 21:53 UTC

 

Mesoscale Convective Vortex over Nevada

August 19th, 2013 |

 

GOES-13 10.7 µm IR channel images (click image to play animation)

GOES-13 10.7 µm IR channel images (click image to play animation)

AWIPS images of 4-km resolution GOES-13 10.7 µm IR channel data (above; click image to play animation) showed areas of nocturnal thunderstorms over southeastern California, western Arizona, and southern Nevada on 19 August 2013. These storms were initially producing numerous cloud-to-ground lightning strikes and exhibiting cloud-top IR brightness temperatures as cold as -66 C, but they began to dissipate toward sunrise as they continued to move northward.

A comparison of 375-meter resolution (projected onto a 1-km AWIPS grid) Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel images at 09:17 UTC (below) provided a good example of the “visible image at night” capability of the Day/Night Band.

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

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

The GOES-14 satellite had been placed into Super Rapid Scan Operations for GOES-R (SRSO-R) mode, and was providing images at 1-minute intervals on this day. Once the cirrus canopy from the dissipating thunderstorms eroded, the GOES-14 0.63 µm visible channel images (below; click image to play animation; also available as a QuickTime movie) revealed the presence of a small yet well-defined Mesoscale Convective Vortex (MCV) which continued to propagate northward across far eastern Nevada. Toward the end of the animation (20:57 UTC), the MCV appeared to be playing a role in the initiation of new convection along its northern (leading) edge.

GOES-14 0.63 µm visible channel images (click image to play animation)

GOES-14 0.63 µm visible channel images (click image to play animation)

A comparison of Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images at 20:43 UTC (below) showed that there were a couple of negative polarity cloud-to-ground lightning strikes (yellow) being produced by the convection that developed along the leading edge of the MCV.

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

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

 

Blended Total Precipitable Water product

Blended Total Precipitable Water product

The Blended Total Precipitable Water (TPW) product (above, shown at 3-hour intervals) indicated that a plume of TPW values in the 30-38 mm or 1.2-1.5 inch range (varying shades of yellow) were in place over the region where the thunderstorms had developed and moved northward. These monsoonal TPW values were 175-200% of normal for this area and this time of year (below).

Blended Total Precipitable Water Percent of Normal product

Blended Total Precipitable Water Percent of Normal product

 

GOES IR image with GFS 850-500 hPa shear

GOES IR image with GFS 850-500 hPa shear

In addition, the 850-500 hPa wind shear values across the region at 12 UTC (above) and 18 UTC (below) were relatively low, creating a favorable environment for the MCV to persist for several hours.

GOES IR image with 850-500 hPa shear

GOES IR image with 850-500 hPa shear