Oil slick off the Louisiana coast

April 29th, 2010
MODIS true color and false color RGB images (29 April 2010)

MODIS true color and false color RGB images (29 April 2010)

250-meter resolution MODIS true color and false color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (above) showed that the oil slick resulting from the offshore oil rig fire and collapse (following an explosion on the night of 20 April 2010) continued to get closer to the coast of Louisiana on 29 April 2010. Along the far western edge of the oil slick, a small smoke plume can be seen drifting northeastward, due to a small controlled burn (the winds were from the southwest at altitudes of about 1 km and higher).

A comparison of MODIS true color images on 21, 22, 25, 29 April, and 01 May (below) show the original smoke plume from the burning oil rig, followed by the dramatic growth and change in shape of the oil slick during that period.

MODIS true color RGB images (21, 22, 25, 29 April and 01 May 2010)

MODIS true color RGB images (21, 22, 25, 29 April, and 01 May 2010)

An AWIPS image of the MODIS visible channel data with an overlay of buoy, ship, and ASCAT scatterometer winds (below) showed that southeasterly winds at the surface across the northern Gulf of Mexico were helping to move the oil slick closer to the Mississippi River Delta region of Louisiana.

MODIS visible image + surface buoy/ship data + ASCAT scatterometer winds

MODIS visible image + surface buoy/ship data + ASCAT scatterometer winds

The POES AVHRR Sea Surface Temperature (SST) product (below) revealed that the oil slick feature continued to exhibit SST values that were several degrees F cooler (upper 60s F, green colors) than the surrounding waters (lower 70s F, yellow to orange colors) — see a previous loop of AVHRR and MODIS SST images from 25-26 April. The very warm SST values (upper 70s to low 80s F, darker red colors) associated with the Gulf of Mexico Loop Current can be seen in the lower right corner of the image.

POES AVHRR Sea Surface Temperature (SST) product

POES AVHRR Sea Surface Temperature (SST) product

Plume of blowing dust/sand originating from White Sands, New Mexico

April 29th, 2010
GOES-13 0.65 µm visible channel images

GOES-13 0.65 µm visible channel images

McIDAS images of the GOES-13 0.65 µm visible channel data (above) showed the development of a well-defined plume of blowing dust/sand that appeared to originate from the White Sands, New Mexico area on 29 April 2010 — this plume of airborne aerosols very quickly reached the Texas/New Mexico border by about 21 UTC. Very strong winds (gusting to 50-70 mph) across the region were responsible for the widespread areas of blowing dust, which restricted surface visibilities to below 3 miles at a number of sites across New Mexico.

First GOES-15 Full Disk IR Images

April 26th, 2010
First official GOES-15 10.7 µm longwave IR image (click image to enlarge)

First official GOES-15 10.7 µm longwave IR image (click image to enlarge)

The first official GOES-15 full disk InfraRed (IR) images became available at 17:30 UTC on 26 April 2010. The GOES-15 Imager 10.7 µm longwave IR image is shown above – similar images are available for the 0.65 µm visible channel, the 3.9 µm shortwave IR, the 6.5 µm water vapor channel, and the 13.3 µm CO2 channel.

GOES-15 was launched on 04 March 2010, with the first visible images from the Imager instrument available on 06 April and from the first visible images from the Sounder instrument on 08 April. GOES-15 will have a Post Launch Test beginning in August 2010.

Color-enhanced GOES-15 IR images

GOES-15 multi-panel display of the Imager visible and IR channels

A multi-panel display showing all 5 of the  GOES-15 Imager channels is shown above. For comparison purposes, a similar multi-panel display  of all five of the GOES-13 Imager channels is shown below.

GOES-13 multi-panel display of the Imager visible and IR channels

GOES-13 multi-panel display of the Imager visible and IR channels

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GOES-13 and GOES-15 10.7 µm IR images

GOES-13 and GOES-15 10.7 µm longwave IR images

Some close-up comparisons of GOES-13 and GOES-15 IR images show similar results from the two satellites. The image above uses GOES-13 and GOES-15 10.7 µm longwave IR channel data to display a cluster of strong convection over the far eastern Gulf of Mexico, between Florida and Cuba — the coldest 10.7 µm IR brightness temperatures seen were 196.2 K (-77.0º C) on GOES-13, vs 194.9 K (-78.3º C) on GOES-15.

The image below is a comparison of the 13.3 µm CO2 channels. Note that the Field of View (FOV) of the 13.3 µm CO2 channel has improved from 8 km on GOES-13 to 4 km on GOES-15 — as a result, the edges of cloud features now appear much smoother on the GOES-15 13.3 µm image.

GOES-13 and GOES-15 13.3 µm CO2 channel images

GOES-13 and GOES-15 13.3 µm CO2 channel images

Looking farther to the west, the image below shows the Gulf of Mexico Loop Current, using the 3.9 µm shortwave IR channel data from GOES-13 and GOES-15. AWIPS images of the Sea Surface Temperature (SST) products from MODIS and AVHRR indicated that the SST values were as warm as 80º F within the Loop Current, surrounded by waters with SST values in the 70-75º F range.

GOES-13 and GOES-15 3.9 µm shortwave IR images

GOES-13 and GOES-15 3.9 µm shortwave IR images

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GOES-13 and GOES-15 6.5 µm water vapor images

GOES-13 and GOES-15 6.5 µm water vapor images

A comparison of the GOES-13 and GOES-15 6.5 µm water vapor channels (above) showed a pocket of very dry air (yellow to orange color enhancement) to the north of the aforementioned strong convection located between Florida and Cuba. This dry air was a signature of a well-defined  “jet stream break”, as verified by GFS model 250 hPa wind speed isotachs (below).

GOES-13 water vapor image + GFS 250 hPa wind speed isotachs

GOES-13 water vapor image + GFS 250 hPa wind speed isotachs

Deadly tornado outbreak across the Deep South

April 24th, 2010
GOES-13 6.5 µm water vapor imagery + surface fronts

GOES-13 6.5 µm water vapor imagery + surface fronts

On a rare “High Risk” SPC Convective Outlook day, a significant tornado outbreak occurred across the Deep South region of the US on 24 April 2010 which produced long-track tornadoes that were responsible for at least 10 fatalities across parts of Mississippi (SPC storm reports | NWS Jackson MS event summary). AWIPS images of the GOES-13 6.5 µm water vapor channel data with overlays of surface fronts (above) showed a cold frontal boundary advancing eastward across the region, with a strong punch of dry air aloft associated with an upper level jet stream. The NAM model fields suggested that the maximum winds within the jet core were in the 140-145 knot range, but there were a number of MADIS 1-hour interval atmospheric motion vectors with speeds of 155-157 knots along the sharp dry-to-moist water vapor gradient.

Widespread cloudiness obstructed a good view of the amount of Total Precipitable Water (TPW) that was available using the GOES Sounder or MODIS, but the Blended Total Precipitable Water product (below) showed that TPW values of 40 – 50 mm (red to violet color enhancement) were in place within the warm sector ahead of the cold front.

Blended Total Precipitable Water product

Blended Total Precipitable Water product

An animation of GOES-13 10.7 µm IR images (below) revealed that the cluster of severe convection appeared to intensify as it crossed the Mississippi River from Louisiana into Mississippi after about 16 UTC. While there was not the typical “enhanced-v” storm top signature that is often seen with severe convection, the GOES-13 IR cloud top brightness temperatures did cool to -60º C and below (darker red color enhancement) after 13:40 UTC, reaching a minimum value of -63º C at 18:32 UTC.

Closer views of the IR imagery showed that these storms were characterized by a great deal of cloud to ground lightning strikes (24-hour total lightning strikes) as they produced a number of tornado and damaging wind reports. Farther to the north, there was a report of softball-size hail (4.5 inches in diameter) in western Tennessee at 21:00 UTC.

GOES-13 10.7 µm IR images + METAR surface reports

GOES-13 10.7 µm IR images + METAR surface reports

A comparison of a 1-km resolution MODIS 11.0 µm IR image with the corresponding 4-km resolution GOES-13 10.7 µm IR image as the core of the storm was crossing the Mississippi River around 16:30 UTC (below) demonstrates (1) the improvement in accuracy of storm top brightness temperature detection with higher spatial resolution (-69º C with MODIS, versus -58º C with GOES), and (2) the “parallax shift” associated with the relatively large geostationary satellite view angle (note that the storm features are shifted a bit to the northwest on the GOES-13 image). The SPC storm reports of tornadoes and damaging winds within the 16:14 – 17:55 UTC time range are also plotted on the two IR images. A similar AVHRR 10.8 µm IR image at 18:40 UTC with an overlay of SPC severe reports can be seen here.

MODIS 11.0 µm IR and GOES-13 10.7 µm IR images (with overlays of severe reports)

MODIS 11.0 µm IR and GOES-13 10.7 µm IR images (with overlays of severe reports)

===== 25 April Update =====

Comparison of MODIS true color images from 15 April and 25 April 2010

Comparison of MODIS true color images from 15 April and 25 April 2010

Viewing a comparison of “before” (15 April) and “after” (25 April) 250-meter resolution MODIS true color images (above) and false color images (below), from the SSEC MODIS Today site, the subtle signature of a portion of the tornado damage path can be seen. Viewing the MODIS true color image using Google Earth, the southwest-to-northeast oriented tornado damage path can be seen extending from the eastern half of Yazoo county into the southern portion of Holmes county in Mississippi. The tornado that struck the Yazoo City area has been given a preliminary damage assessment rating of EF4, with a maximum damage path width of 1.75 miles.

Comparison of MODIS false color images from 15 April and 25 April 2010

Comparison of MODIS false color images from 15 April and 25 April 2010

===== 28 April Update =====

A comparison of 250-meter resolution Aqua MODIS visible Band 1 and Band 2 images from 28 April 2010  (below) reveals portions of the tornado damage path across parts of Issaquena and Yazoo counties in Mississippi. In areas with a higher density of trees, the tornado damage path appears as a lighter shade of gray on the Band 1 image, and as a darker shade of gray on the Band 2 image.

Portions of the tornado damage path on MODIS visible bands 1 and 2

Portions of the tornado damage path on MODIS visible band 1 and visible band 2 images

Related sites:

Weather Underground radar images

AccuWeather WeatherMatrix blog post