GOES-15 (left) and GOES-13 (right) 0.63 µm visible channel images (click image to play animation)

A comparison of McIDAS images of 1-km resolution GOES-15 (GOES-West) and GOES-13 (GOES-East) 0.63 µm visible channel data (above; click image to play animation) showed the smoke plume from the Springs Fire near Camarillo, California on 02 May 2013. GOES-15 (positioned over the Equator at 135º West longitude) had a better viewing angle of the smoke plume, while GOES-13 (positioned at 75º West longitude) was in Rapid Scan Operations (RSO) mode and was therefore able to provide more frequent images.

AWIPS images of 4-km resolution GOES-15 3.9 µm shortwave IR data (below; click image to play animation) showed the development and rapid growth of the fire “hot spot” signature (dark black enhancment) after 14:01 UTC (7:01 AM local time). At Point Mugu (station identifier KNTD), the surface winds gusted to 27 knots from the southwest at 17 UTC, then shifted and gusted to 30 knots from the northwest at 19 UTC, and then shifted again and gusted to 30 knots from the southwest at 20 UTC. Surface visibility at this site was reported to be as low as 2 miles to the north and northeast of the station, with an overcast layer of smoke during most of the day. Not far inland at Sandberg (station identifier KSDB), winds gusted to 46 knots and the dew point temperature dropped to -19º F (making for a relative humidity of 2%!).

GOES-15 3.9 µm shortwave IR images (click image to play animation)

===== 03 May Update =====

AWIPS images of 1-km resolution Suomi NPP VIIRS 3.74 µm shortwave IR and 0.7 µm Day/Night Band data at 09:41 UTC or 2:41 AM local time on 03 May (below) showed a very large fire “hot spot” (yellow to red to black color enhancement) on the shortwave IR image, and the Day/Night Band revealed the hazy signature of smoke aloft that had drifted offshore and south and southeastward along the southern California coast.

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

During the following afternoon on 03 May, 250-meter resolution true-color and false-color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (below) showed the dense smoke plume continuing to drift offshore; the hottest active fire regions appeared as light red features on the false-color image.

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

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Suomi NPP VIIRS 11.45 µm IR channel and 0.7 µm Day/Night Band images (with overlays of cloud-to-ground lightning strikes)

A large nocturnal mesoscale convective system (MCS) was moving eastward across the Gulf of Mexico during the pre-dawn hours on 01 May 2013. AWIPS images of Suomi NPP VIIRS 11.45 µm IR channel and 0.7 µm Day/Night Band (DNB) data with an overlay of cloud-to-ground lightning strikes (above) revealed numerous cloud-top gravity waves. In addition to providing a “visible image at night” that helped to highlight these gravity waves as well as shadows from overshooting tops, the DNB image also showed several bright “streaks” denoting cloud tops illuminated by areas of intense lightning activity. The coldest cloud top IR brightness temperatures (associated with some of the overshooting tops) were -76º C.

A Suomi NPP VIIRS 11.45 µm IR image with surface buoy reports (below) showed that there was a peak wind gust of 45 knots (52 mph) at Buoy 42003 (which occured at 06:50 UTC).

Suomi NPP VIIRS 11.45 µm IR channel image with surface buoy reports

A comparison of 1-km resolution Suomi NPP VIIRS 11.45 µm IR and 4-km resolution GOES-13 IR images (below) demonstrated the advantage of higher spatial resolution for showing the detailed cloud top structures exhibited by the MCS.

Suomi NPP VIIRS 11.45 µm IR channel and GOES-13 10.7 µm IR channel images

A great deal of lightning was associated with this MCS as it propagated eastward across the Gulf of Mexico, with the storm often producing over 1000 cloud-to-ground strikes within a 15-minute period (below; click image to play animation).

GOES-13 10.7 µm IR channel images with cloud-to-ground lightning strikes (click image to play animation)

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GOES-15 IR brightness temperature difference “Fog/stratus product” (click image to play animation)

The San Francisco Bay Area National Weather Service forecast office made use of a variety of satellite images and products to monitor the development of fog and stratus clouds along the central California coast during the pre-dawn hours of 30 April 2013. From their forecast discussion:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
451 AM PDT TUE APR 30 2013

.DISCUSSION…AS OF 3:20 AM PDT TUESDAY…SATELLITE AND SURFACE OBS INDICATE ONLY SOME MINOR POCKETS OF LOW CLOUDS AND PATCHY FOG.
RIGHT NOW HALF MOON BAY IS THE ONLY SPOT REPORTING REDUCED VISIBILITIES WHILE MONTEREY NOW HAS A CEILING. DETAILS FROM THE OVERNIGHT
SATELLITE FOG PRODUCT ARE A BIT DIFFICULT TO MAKE OUT ALTHOUGH LOOKS LIKE THE AREAS ARE VERY SMALL IN NATURE.

Using the 4-km resolution GOES-15 11-3.9 µm IR brightness temperature difference (BTD) “fog/stratus product” with the default gray-scale enhancement applied (above; click image to play animation), it was indeed difficult to unambiguously determine the motion and areal coverage of the darker fog and stratus features (especially in the Monterey Bay area). Applying a tailored color enhancement to that same GOES-15 BTD fog/stratus product does help a little to highlight some of the more well-defined fog and stratus features (with a darker orange color), but there is also a tendency to produce large areas of noisy “false alarm” fog/stratus signals (yellow color enhancement) over much of the inland areas of central California.

In the Aviation section of their forecast discussion, mention was made of the GOES-R Marginal Visual Flight Rules (MVFR) product, which is produced using an algorithm designed for the upcoming GOES-R satellite (but applied to current GOES-15 data):

MONTEREY BAY AREA TERMINALS…SHORT LIVED MVFR THIS MORNING. VIIRS DAY NIGHT SATELLITE AND GOES-R MVFR PROBABILITIES INDICATE CLOUD DECK IS PATCHY.

This GOES-15 product (below; click image to play animation) did indeed show that the areas of 50-80% MVFR Probability were patchy in nature in the vicinity of Monterey Bay.

GOES-15 MVFR Probability product (click image to play animation)

Other GOES-R Fog/Low Stratus products (produced as part of the GOES-R Proving Ground activities at CIMSS/ASPB) include an Instrument Flight Rules (IFR) Probability product, a Low Instrument Flight Rules (LIFR) Probability product, and a Low Cloud Thickness product.

Mention was also made of the Suomi NPP VIIRS 0.7 µm Day/Night Band, which provided a high spatial resolution (750 meters, re-mapped onto a 1-km AWIPS grid) “visible image at night” (below), helping to confirm the spotty nature of the coverage of fog/stratus in the Monterey Bay area.

Suomi NPP VIIRS 0.7 µm Day/Night Band image

Meanwhile, fog and stratus were more widespread across the southern California coast and adjacent offshore waters – for more details, see the GOES-R Fog Product Examples site.

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Suomi NPP VIIRS 0.7 µm Day/Night Band and IR brightness temperature difference “Fog/stratus product”

A number of interesting night-time images were available using the Suomi NPP VIIRS 0.7 µm Day/Night Band (DNB) on 26 April 2013 — since there was abundant illumination from the full “Pink Moon”, this allowed the DNB to provide “visible images at night” which showed city lights as well as a number of meteorological phenomena. We’ll begin our tour in the northeastern US, where a comparison of the VIIRS DNB with the corresponding IR brightness temperature diference (BTD) “Fog/stratus product” (above) showed narrow fingers of valley fog from northwestern Pennsylvania to eastern Ohio at 06:52 UTC or 2:52 AM local time.

Farther to the south, a narrow band of thick cirrus cloud (which exhibited IR brightness temperatures as cold as -40º C) was casting a shadow on the ground from far southeastern Kentucky to northeastern Tennessee (below).

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

Over the north-central US, the VIIRS DNB showed areas that still had substantial snowpack remaining across parts of North Dakota, South Dakota, and Minnesota at 08:34 UTC or 3:34 AM local time (below). Even though there were patches of cirrus cloud over North Dakota (which appear black on the Fog/stratus product), features such as the ice-covered Lake Sakakawea, the Souris River (parts of which were in flood stage and producing moderate flooding), and the edge of the snow cover could still be identified through these high-level clouds on the DNB image.

Suomi NPP VIIRS 0.7 µm Day/Night Band and IR BTD “Fog/stratus product” images

To the south, clouds bands associated with an undular bore could be seen on the DNB image over the Texas Panhandle region (below).

Suomi NPP VIIRS 0.7 µm Day/Night Band image with METAR surface reports

Moving toward the western US, images of the DNB and the 11.45 µm IR channel centered over the Salt Lake City, Utah area (below) revealed colder (violet color enhancement on the IR image) snow-covered mountain ranges (most notable were the Wasatch Range in Utah and the Wind River Range in Wyoming), as well as the large, bright area of the Bonneville Salt Flats in the Great Salt Lake Desert.

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

Finally, some interesting views along the West Coast of the US, beginning with a comparison of the VIIRS DNB and BTD Fog/stratus product centered over the Seattle and Vancouver Island region at 10:12 UTC or 3:12 AM local time (below). Fingers of marine layer stratus clouds could be seen moving inland across the Olympic Peninsula of far northwestern Washington State — and the snow-covered Olympic Mountains (which includes Mount Olympus at an elevation of 7,962 ft or 2,427 m) were plainly visible on the DNB image. Stratus clouds were also seen moving inland through the Strait of Juan de Fuca, as well as into the southern portion of Puget Sound.

Suomi NPP VIIRS 0.7 µm Day/Night Band and IR brightness temperature difference “Fog/stratus product”

Farther to the south along the southern Oregon and northern California coasts, the inland extent of fingers of marine layer stratus clouds could again be seen on both the VIIRS DNB and BTD Fog/stratus product images (below).

Suomi NPP VIIRS 0.7 µm Day/Night Band and IR brightness temperature difference Fog/stratus product

Finally, a comparison of VIIRS DNB and BTD Fog/stratus product images centered over the San Francisco area (below) showed where marine layer stratus clouds covered portions of the San Francisco Bay, San Pablo Bay, and adjacent inland valleys. Other features of interest included a small eddy circulation just offshore of Monterey (KMRY), as well as an aircraft dissipation trail slicing southwest-to-northeast through the patch of offshore stratus cloud located just to the northwest of the eddy (likely caused by a jet either ascending or descending through the cloud flying outbound or inbound from San Francisco International airport KSFO).

Suomi NPP VIIRS 0.7 µm Day/Night Band and IR brightness temperature difference “Fog/stratus product” images

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