Category 4 Hurricanes Kilo, Ignacio, and Jimena in the Pacific Ocean

August 30th, 2015

Suomi NPP VIIRS true-color image composite [click to enlarge]

Suomi NPP VIIRS true-color image composite [click to enlarge]

A composite of Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images from the SSEC RealEarth site (above; click to enlarge) showed Hurricanes Kilo, Ignacio, and Jimena in the Central and Eastern Pacific Ocean on 29 August 2015. All three of these Category 4 hurricanes were located east of the International Dateline, which is the first such occurrence since reliable records began in the satellite era.

An animation of GOES-15 (GOES-West) Infrared (10.7 µm) images (below; click image to play animation) showed the evolution of these 3 tropical cyclones during the 29-30 August period.

GOES-15 Infrared (10.7 µm) images [click to play animation]

GOES-15 Infrared (10.7 µm) images [click to play animation]

The MIMIC Total Precipitable Water product (below; click image to play animation) indicated that all 3 storms were easily able to tap abundant moisture from the Intertropical Convergence Zone (ITCZ).

MIMIC TPW product [click to play animation]

MIMIC TPW product [click to play animation]

Mesoscale Convective System in South Dakota

August 27th, 2015

Suomi NPP VIIRS Infrared (11.45 µm) and Day/Night Band (0.7 µm) images [click to enlarge]

Suomi NPP VIIRS Infrared (11.45 µm) and Day/Night Band (0.7 µm) images [click to enlarge]

A large Mesoscale Convective System (MCS) developed over western South Dakota late in the day on 26 August 2015, moving eastward across the state and producing wind gusts as high as 79 mph (SPC storm reports). A nighttime comparison of Suomi NPP VIIRS Infrared (11.45 µm) and Day/Night Band (0.7 µm) images at 0842 UTC (above) showed the large cloud shield with cloud-top IR brightness temperatures as cold as -74º C at the central cluster of overshooting tops; bright white pixels on the Day/Night Band image were portions of the cloud illuminated by intense lightning activity. Various types of waves were also seen in the VIIRS imagery: (1) concentric gravity waves propagating outward from the central cluster of overshooting tops, (2) transverse banding emanating radially outward in portions of the northern semicircle of the MCS, and (3) a large arc of waves moving westward away from the back edge of the storm.

Regarding the large arc of waves along the back edge of the MCS, GOES-13 (GOES-East) water vapor (6.5 µm) images (below; click image to play animation) revealed a signal of strong subsidence (warming/drying, darker blue color enhancement) as the westward-expanding cloud mass was acting as an obstacle to the prevailing westerly winds coming from Wyoming and Montana.

GOES-13 water vapor (6.5 µm) images [click to play animation]

GOES-13 water vapor (6.5 µm) images [click to play animation]

GOES-14 SRSO-R: central Montana wildfire

August 15th, 2015

GOES-15 (left), GOES-14 (center), and GOES-13 (right) 3.9 µm shortwave IR images [click to play MP4 animation]

GOES-15 (left), GOES-14 (center), and GOES-13 (right) 3.9 µm shortwave IR images [click to play MP4 animation]

A comparison of 4-km resolution GOES-15 (GOES-West), GOES-14, and GOES-13 (GOES-East) 3.9 µm shortwave infrared images (above; click to play MP4 animation; also available as a 9.4 Mbyte animated GIF) showed the development and evolution of the “hot spot” (dark black to yellow to red color enhancement) associated with a small wildfire that formed near the border of Fergus and Petroleum counties in central Montana during the afternoon hours on 15 August 2015. With GOES-15 Routine Scan mode “SUB-CONUS” sectors, images were available up to 6 times per hour (at :00, :11, :15, :30, :41, and :45); with GOES-13 in Rapid Scan Operations (RSO) mode, images were available up to 8 times per hour (at :00, :07, :15, :25, :30, :37, :45, and :55). The GOES-14 satellite had been placed into Super Rapid Scan Operations for GOES-R (SRSO-R) mode, providing images at 1-minute intervals to emulate what will be available with mesoscale sectors from the ABI instrument on GOES-R.

For the central Montana wildfire, the first unambiguous signature of a darker black wildfire hot spot began to appear on each satellite after about 1945 UTC, with the first color-enhanced pixels (signifying a shortwave IR brightness temperature of 331.9 K) showing up on the 2026 UTC GOES-14 image. The hottest fire pixel  on the GOES-15 images was 336.5 K at 2130 UTC, while the hottest fire pixel on GOES-13 images was 329.8 K at 2125 UTC. From 2120 to 2130 UTC, the hottest GOES-14 fire pixels were 341.2 K (the saturation temperature of the 3.9 µm detectors on that satellite).

With the finer spatial resolution of the shortwave IR detectors on the polar-orbiting MODIS (1-km) and VIIRS (375-meter) instruments, a fire hot spot was first detected on the 1857 UTC VIIRS image (below).

Terra/Aqua MODIS and Suomi NPP VIIRS 3.7 µm shortwave IR images [click to enlarge]

Terra/Aqua MODIS and Suomi NPP VIIRS 3.7 µm shortwave IR images [click to enlarge]

Eruption of the Cotopaxi volcano in Ecuador

August 14th, 2015

GOES-13 visible (0.63 µm) images [click to play animation]

GOES-13 visible (0.63 µm) images [click to play animation]

GOES-13 visible (0.63 µm) images (above; click to play animation) displayed distinct dark-gray ash plumes from 2 separate daytime eruptions of the Cotopaxi volcano in Ecuador on 14 August 2015 (there was also an initial eruption that occurred during the preceding nighttime hours). The asterisk near the center of the images marks the location of the volcano summit. Volcanic ash fall was observed in the capitol city of Quito (station identifier SEQU, located about 50 km or 30 miles north of the volcano), and some flights were diverted due to the volcanic ash cloud.

The corresponding GOES-13 infrared (10.7 µm) images (below; click image to play animation) showed that cloud-top IR brightness  temperatures were as cold a -53º C (orange color enhancement) at 1915 UTC.

GOES-13 infrared (10.7 µm) images [click to play animation]

GOES-13 infrared (10.7 µm) images [click to play animation]

The volcanic cloud features were also easily tracked on GOES-13 water vapor (6.5 µm) images (below; click image to play animation). In fact, note how the signature in the water vapor imagery is more distinctly seen for a longer period of time than on the 10.7 µm infrared imagery.

 GOES-13 water vapor (6.5 µm) images [click to play animation]

GOES-13 water vapor (6.5 µm) images [click to play animation]

The tan-colored volcanic ash cloud was also evident on Aqua MODIS and Suomi NPP VIIRS true-color Red/Green/Blue (RGB) imagery (below), as viewed using the SSEC RealEarth web map server.

Aqua MODIS true-color images [click to enlarge]

Aqua MODIS true-color images [click to enlarge]

Suomi NPP VIIRS true-color image [click to enlarge]

Suomi NPP VIIRS true-color image [click to enlarge]

A comparison of Suomi NPP VIIRS visible (0.64 µm) and infrared (11.45 µm) images is shown below (courtesy of William Straka, SSEC). The coldest cloud-top IR brightness temperature was -72.7º C.

Suomi NPP VIIRS visible (0.64 µm) and infrared (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS visible (0.64 µm) and infrared (11.45 µm) images [click to enlarge]