“Cooling pond effect snow” in northern Illinois

December 30th, 2012 |
MODIS true-color and false-color Red/Green/Blue (RGB) images

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

A comparison of 250-meter resolution MODIS true-color and false-color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (above) revealed an interesting snow cover feature (snow appears as white on the true-color image, and cyan on the false-color image) surrounding a small body of water in northern Illinois (just north of the cursor) on 30 December 2012.

A closer view of that area using Google Earth (below) indicated that the small body of water was the cooling pond of the LaSalle County Nuclear Generating Station.

MODIS true-color image (displayed using Google Earth)

MODIS true-color image (displayed using Google Earth)

An AWIPS image of the MODIS Sea Surface Temperature (SST) product (below) showed that SST values were as warm as 55.8 F in the cooling pond — so the flow of colder air (which was generally in the 20s to 30s F) from a variety of directions produced “cooling pond effect snowfall” immediately downwind of the pond.

MODIS Sea Surface Temperature product

MODIS Sea Surface Temperature product

 

Blowing dust in northern Mexico, southwestern Texas, and southeastern New Mexico

November 10th, 2012 |
MODIS 11-12 µm IR brightnes temperature difference with surface METAR reports and frontal analysis

MODIS 11-12 µm IR brightnes temperature difference with surface METAR reports and frontal analysis

Strong southwesterly winds (gusting as high as 86 mph in New Mexico and 73 mph in Texas) ahead of an advancing cold front were causing dense plumes of blowing dust that restricted surface visibility to 0.5 mile at El Paso, Texas (station identifier KELP) on 10 November 2012. An AWIPS image of the 1-km resolution MODIS 11-12 µm IR brightness temperature difference (BTD) product (above) showed the areal coverage of the blowing dust (cyan to yellow color enhancement) at 20:17 UTC (3:17 PM local time).

The blowing dust plumes could also be seen on a 250-meter resolution MODIS true-color Red/Green/Blue (RGB) image from the SSEC MODIS Today site (below).

MODIS true-color Red/Green/Blue (RGB) image (displayed using Google Earth)

MODIS true-color Red/Green/Blue (RGB) image (displayed using Google Earth)

MODIS 0.65 µm visible channel and 11.0 µm IR channel images

MODIS 0.65 µm visible channel and 11.0 µm IR channel images

AWIPS comparisons of 1-km resolution MODIS (above) and Suomi NPP VIIRS (below) visible channel and IR channel images revealed that the airborne dust exhibited a cooler signature (lighter gray enhancement) on the IR imagery.

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

In spite of a brief downgrade, Sandy maintains hurricane intensity

October 27th, 2012 |
POES AVHRR 12.0 µm, MODIS 11.0 µm, and Suomi NPP VIIRS 11.45 µm IR images

POES AVHRR 12.0 µm, MODIS 11.0 µm, and Suomi NPP VIIRS 11.45 µm IR images

During the overnight hours after midnight on 27 October 2012, Sandy was briefly downgraded to a Tropical Storm by the National Hurricane Center (discussion archive). A sequence of AWIPS images of 1-km resolution POES AVHRR 12.0 µm, MODIS 11.0 µm, and Suomi NPP VIIRS 11.45 µm IR images (above) showed persistent pockets of deep convection north and west of the center of the tropical cyclone.

Since the Moon was in the waxing gibbous phase (at 97% of full moon phase), it provided ample illumination for a “night-time visible” image using the Suomi NPP Day/Night Band (DNB) at 06:43 UTC or 2:43 AM local time (below). A few overshooting top features could be seen in the DNB image, which corresponded with the areas of colder cloud top IR brightness temperatures seen on the VIIRS 11.45 µm IR image at that same time.

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

After sunrise, GOES-14 1-minute interval SRSOR visible channel data (below; click image to play HD format QuickTime movie) showed great details of the deep convective development north and west of the partially-exposed low-level circulation center.

GOES-14 0.63 µm visible channel image (click image to play QuickTime movie)

GOES-14 0.63 µm visible channel image (click image to play QuickTime movie)

Additional GOES-14 SRSOR images during the afternoon hours (below; cick image to play HD format QuickTime movie) continued to show the development of convective bursts just north of the partialy-exposed low-level circulation center.

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

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

A larger-scale view using MODIS 0.65 µm visible, 11.0 µm IR, and 6.7 µm water vapor channel images (below) showed the very large size of the cloud field associated with Sandy (which had re-gained hurricane intensity by this time). Also evident on the MODIS water vapor channel image was the large intrusion of dry air wrapping around the southern and eastern quadrants of Sandy, hinting at the early stages of a transition from a tropical system to an extratropical system.

MODIS 0.65 µm visible, 11.0 µm IR, and 6.7 µm water vapor channel images

MODIS 0.65 µm visible, 11.0 µm IR, and 6.7 µm water vapor channel images

An Aqua MODIS true-color Red/Green/Blue (RGB) image from the SSEC MODIS Today site (below) revealed large areas of increased turbidity in the waters just west of Florida and the Bahamas, due to mixing from the strond winds associated with Hurricane Sandy.

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

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

Finally, it was observed that there were a number of pilot reports of moderate to severe turbulence near the western periphery of the cloud shield of Sandy, where there were also hints of a transvese banding structure. Two notable pilot reports are displayed on Suomi NPP VIIRS 11.45 µm IR and MODIS 6.7 µm water vapor channel images (below).

Suomi NPP VIIRS 11.45 µm IR image with pilot report of severe turbulence

Suomi NPP VIIRS 11.45 µm IR image with pilot report of severe turbulence

MODIS 6.7 µm water vapor channel image with pilot report of moderate turbuence

MODIS 6.7 µm water vapor channel image with pilot report of moderate turbuence

Strong winds and blowing dust across Nebraska, Kansas, and Oklahoma

October 18th, 2012 |
Suomi NPP VIIRS 0.64 µm visible channel images

Suomi NPP VIIRS 0.64 µm visible channel images

AWIPS images of Suomi NPP VIIRS 0.64 µm visible channel data (above) showed the hazy signature of a dense plume of blowing dust along the southwestern periphery of a large mid-latitude cyclone that was centered over Minnesota and Wisconsin on 18 October 2012. Surface winds gusted as high as 73 mph in Nebraska and 56 mph in Kansas, reducing visibility to near zero in areas of dense blowing dust.

An animation of AWIPS 4-panel images of GOES-13 0.63 µm visible channel, 6.5 µm water vapor channel, 10.7 µm IR channel, and 3.9 µm shortwave IR data (below; click image to play animation) showed (1) the evolution of the dense plume of blowing dust on visible imagery as it developed and moved southeastward across Nebraska, Kansas, and Oklahoma; (2) a well-defined dry region (yellow color enhancement) on water vapor imagery that highlighted strong middle-tropospheric subsidence that initiated the downward transfer of momentum leading to the subsequent strong winds at the surface; and (3) the appearance of wildfire “hot spots” (black to yellow to red color enhancement) on the shortwave IR imagery in northeastern Colorado and southwestern Nebraska.

GOES-13 0.63 µm visible, 6.5 µm water vapor, 10.7 µm IR, and 3.9 µm shortwave IR images (click image to play animation)

GOES-13 0.63 µm visible, 6.5 µm water vapor, 10.7 µm IR, and 3.9 µm shortwave IR images (click image to play animation)

An Aqua MODIS true-color Red/Green/Blue (RGB) image from the SSEC MODIS Today site (below) showed the tan/light brown signature of the most dense portion of the blowing dust plume. The blowing dust reduced surface visibility to near zero in a number of areas, forcing road closures across parts of Nebraska and Kansas — including a multiple-vehicle accident that closed Interstate 35 near Blackwell, Oklahoma.

MODIS true color image (displayed using Google Earth)

MODIS true color image (displayed using Google Earth)

 

MODIS 0.64 µm visible channel and 11-12 µm IR brightness temperature difference (BTD) product

MODIS 0.64 µm visible channel and 11-12 µm IR brightness temperature difference (BTD) product

A comparison of the MODIS 0.64 µm visible channel data with the corresponding 11-12 µm IR brightness temperature difference (BTD) product (above) demonstrated that the BTD product did a better job at depicting the broad areal extent of the airborne dust (lighter blue to cyan color enhancement) at 20:13 UTC (3:13 PM local time). There was one pilot report of moderate to severe turbulence over northeastern Oklahoma near the leading edge of the dust plume.

===== 19 October Update =====

The MODIS BTD product was then able to follow the movement of the dust plume during the subsequent overnight hours, when visible channel imagery was no longer available — the plume became more narrow and less dense as it continued to move southeastward across Arkansas and then over northern Mississippi and Alabama by 08:10 UTC (4:10 AM local time) on 19 October (below).

MODIS 11-12 µm IR brightness temperature difference (BTD) product

MODIS 11-12 µm IR brightness temperature difference (BTD) product

After sunrise on the morning of 19 October, the hazy signature of the airborne dust could be seen on GOES-14 0.63 µm visible channel images over the southeastern US (below). There were pilot reports of flight visibility being restricted to 2 miles at an altitude of 1000 feet over southeastern Tennessee (GOES-13 visible image | MODIS BTD image), and 3 miles at an altitude of 3500 feet over northern Alabama (GOES-13 visible image | MODIS BTD image).

GOES-14 0.63 µm visible channel images

GOES-14 0.63 µm visible channel images