Autumn tree colors seen in MODIS true-color imagery

September 30th, 2012
MODIS true-color Red/Green/Blue (RGB) image

MODIS true-color Red/Green/Blue (RGB) image

A spectacular display of autumn tree colors can be seen on 30 September 2012 across parts of northeastern Minnesota, northern Wisconsin, and the Upper Peninsula of Michigan in this 250-meter resolution Aqua MODIS true-color Red/Green/Blue (RGB) image from the SSEC MODIS Today site (above).

===== 02 October Update =====

Two days later, another view of the autumn tree foliage colors was provided by a Terra MODIS true-color RGB image from the SSEC MODIS Direct Broadcast site (below).

MODIS true-color Red/Green/Blue (RGB) image

MODIS true-color Red/Green/Blue (RGB) image

Thunderstorms producing heavy rain and flooding in Puerto Rico

September 27th, 2012
GOES-14 0.63 µm visible channel images (click to play animation)

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

Deep moisture and an unstable atmosphere were in place across the island of Puerto Rico on 27 September 2012, creating an environment favorable for the development of strong thunderstorms during the afternoon hours (in response to sea breeze convergence and local terrain effects). 1-km resolution GOES-14 0.63 µm visible channel images (above; click image to play animation) and 4-km resolution GOES-14 10.7 µm IR channel images (below; click image to play animation) showed the development of large thunderstorms which produced very heavy rainfall (as much as 3-4 inches within a 1-2 hour period) which caused flooding problems.

Due to the fact that the the radar at San Juan, Puerto Rico had suffered an outage, the National Weather Service forecast Office in Miami, Florida was called upon to perform back-up duties during the outage (which included the issuance of Area Forecast Discussions and Flood Advisories). To obtain more frequent satellite images during the radar outage, Miami also called for GOES-14 to be placed into Rapid Scan Operations (RSO) — but unfortunately the default CONUS RSO scan sector was used, which did not extend far enough eastward to cover Puerto Rico. Just 3 days earlier, GOES-14 had been activated to replace GOES-13 as the operational GOES-East satellite (since GOES-13 instrument problems caused it to go into standby mode on 23 September)

GOES-14 10.7 µm IR channel images (click to play animation)

GOES-14 10.7 µm IR channel images (click to play animation)

A closer view using 374-meter resolution Suomi NPP VIIRS 0.65 µm visible channel and 11.45 µm IR channel images (below) showed the strongest thunderstorm located over the southwestern portion of the island at 17:27 UTC. The coldest cloud top IR brightness temperature on the VIIRS images was -83º C (compared to -65º C around that same time on GOES-14 IR imagery).

Suomi NPP VIIRS 0.65 µm visible channel and 11.45 µm IR channel images

Suomi NPP VIIRS 0.65 µm visible channel and 11.45 µm IR channel images

Intense cyclone in the Gulf of Alaska

September 26th, 2012
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 cyclone rapidly intensified (deepening 42 mb in 24 hours, and 26 mb in 12 hours) in the Gulf of Alaska on 26 September 2012, and was expected to produce winds up to hurricane force. An AWIPS image comparison of Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel images at 11:24 UTC (above) showed great detail to the cloud features as the storm began to exhibit a classic “cusp” signature as rapid intensification was underway (IR image with surface analysis overlay).

McIDAS images of GOES-15 6.5 µm water vapor channel data (below; click image to play animation) portrayed the evolution of the storm from 04:00 UTC to 23:45 UTC.

GOES-15 6.5 µm water vapor channel images (click to play animation)

GOES-15 6.5 µm water vapor channel images (click to play animation)

VIIRS Day/Night Band: nocturnal detection of wildfire smoke aloft

September 26th, 2012
Suomi NPP VIIRS 0.7 µm Day/Night Band, 11.45 µm IR, and IR difference "fog/stratus product" images

Suomi NPP VIIRS 0.7 µm Day/Night Band, 11.45 µm IR, and IR difference “fog/stratus product” images

A comparison of AWIPS images of Suomi NPP VIIRS 0.7 µm Day/Night Band, 11.45 µm IR, and IR difference “fog/stratus product” data (above) revealed that the Day/Night Band (DNB) can be used for nocturnal detection of dense layers of wildfire smoke aloft (in this case, over parts of Montana, Wyoming, North Dakota, South Dakota, and Nebraska). The brighter DNB signal of the elevated smoke layer was not correlated with any features seen on either the IR image or the fog/stratus product image at 08:04 UTC (2:04 AM  local time) on 26 September 2012.

The MODIS aerosol optical depth (AOD) product (below) showed that high ADO values were found over that region during the afternoon hours (20 UTC) on 25 September. Forward trajectories from the IDEA-I site indicated that the majority of this smoke would be drifting slowly eastward.

MODIS aerosol optical depth (AOD) product

MODIS aerosol optical depth (AOD) product

The hazy signal of this veil of smoke aloft could also be seen on GOES-14 0.63 µm visible channel images late in the day on 25 September and again early in the day on 26 September (below), when the sun angle was low to help highlight the presence of the smoke.

GOES-14 0.63 µm visible channel images

GOES-14 0.63 µm visible channel images