Archive for the ‘RGB’ Category
The VIIRS DNB Radiance and Radiance RGBs showed an increase in fire activity on the night following record high temperatures and unstable conditions over northern NM. The Thompson Ridge Fire is nearly 22,000 acres, the Tres Lagunas Fire 10,000 acres, and the newly started Jaroso Fire is approximately 1,000 acres. The DNB products showed the increased radiance between Monday, June 10th and Tuesday, June 11th, especially for the Tres Lagunas Fire. The new Jaroso Fire to the north of Tres Lagunas is clearly visible on the nighttime product on the morning of the 11th. Some cloud cover is also visible on the Radiance RGB to the north of the Thompson Ridge Fire on the 11th.
It’s been a pretty foggy morning across the Huntsville metro area! But if you’re looking for insight on the extent of the fog from early morning GOES visible imagery, good luck! Mid-level clouds were obscuring lower-level features for a large portion of the region.
Fortunately, the earlier VIIRS pass gave a much better perspective on the fog, despite being on the very edge of the early morning pass.
Some nice details stand out in this image, particularly the multiple river valleys that can be picked out across north Alabama and middle Tennessee. This implies that the fog may be a little more localized than previously thought, and agrees nicely with the rapid improvement of visibility that is being reported after sunrise.
The Tres Lagunas fire erupted during the mid afternoon hours of May 30, 2013. The fire grew quickly to 450+ acres and remained active into the overnight hours. Critical fire weather conditions will redevelop today thus more growth is expected.
Author: Emily Berndt
Mount Pavlof, one of Alaska’s most active volcanoes, has been erupting since last week. The plume has caused some disruption of flights and ash fallout in nearby communities. The Alaska Volcano Observatory has been closely monitoring it’s activity (http://www.avo.alaska.edu/activity/Pavlof.php). The steam, ash, and gas plume is continually created as hot lava contacts snow and ice. The steam, ash, and gas plume has occasionally reached up to 20,000 ft and has been carried downwind as much as 100 km to the northeast, east, and southeast before dissipating. This graphic from the Alaska Volcano Observatory shows the location of Mount Pavlof within the Aleutian Island Chain.
The plume can be seen in the VIIRS RGB Dust product. Let’s first look at the VIIRS true color product. Inside the red circle, you can see a faint brown plume, but it’s not easy to see (click on the images).
Now take a look at the VIIRS RGB Dust product. On the three images below there is a pink/red streak (inside the purple circle) emanating from the location of Mount Pavlof.
This is an excellent example of the utility of multichannel RGB products to obtain a clearer view of the location and extent of volcanic plumes.
During the afternoon of May 20, 2013, the city of Moore, Oklahoma was struck by a large, violent tornado that caused widespread damage and numerous fatalities. Some aspects of the tornado and the resulting damage are observable from space. As with Superstorm Sandy and Hurricane Isaac, the VIIRS day-night band can be used to monitor changes in light resulting from a variety of features, such as moonlight reflection off of cloud tops or the surface, lightning from thunderstorms, fires, or human activity. The images below show day-night band imagery prior to the major tornado as observed in the early morning of May 20 and an image obtained in the early morning of May 21. In the May 21 image, thunderstorms continued east of Oklahoma City. Reflected moonlight provides imaging of ongoing thunderstorms and the DNB captures a few lightning flashes. Clearing skies over the Oklahoma City area help to identify the outages resulting from the tornado several hours earlier. When pre- and post-event imagery are combined in a 24-bit RGB image, reductions in light output appear in shades of light yellow across the Moore, OK area. Changes in cloud cover between the two days result in other shades of blue to identify cloud contamination where the RGB change product is not applicable. A zoomed-in portion for Oklahoma City is shown in the final image.
Many SPoRT team members have spent time in the Oklahoma City area as students at the University of Oklahoma in Norman, or through collaborations with other scientists at the National Weather Center. Our thoughts are with our colleagues in Moore and the citizens of Oklahoma during their recovery efforts.
I’ve been working the midnight shift at the office for the last few nights and have found the MODIS and VIIRS RGB imagery particularly useful. I have viewed the imagery each night and even referenced it specifically in my Area Forecast Discussion early on the morning of the 16th.
A swath of dry air wrapping around the base of the closed low could be seen moving into the region, from Louisiana into Mississippi early on the morning of May 16th. While this was apparent in standard 4 km GOES water vapor imagery, the MODIS Airmass RGB certainly showed more detail. This type of imagery also has the ability to delineate airmass of differing characteristics. Notice the warm, moist airmass across much of the Southeast, ahead of and along the cloud shield. The Nighttime Microphysics RGB image valid at the same time below provided more detail of low level clouds upstream and in the local area, which was important for the forecast.
Since it was apparent that some clearing was indeed possible, if not likely for parts of the area during the morning and into the afternoon, I decided to increase my forecast temperatures. With this type of imagery, it is far easier to delineate between cloud types, and makes the forecast process more efficient. I also noticed that much of the cloud cover at the time to our west, particularly over the Arklamiss area, was mostly cirrus clouds.
This morning, the aviation forecaster and I used the imagery to distinguish between cloud types once again.
While an area of deep convection can be seen in northern Alabama (red colors in north central AL), at the time we were actually more concerned about the low clouds and fog impacting our TAF sites. The image above showed that the low stratus were present across much of northern Alabama and prevalent enough to keep IFR conditions in for the MSL TAF. Additionally, a narrow line of clouds stretching from NE Oklahoma to north central Mississippi could be seen in the imagery. This turned out to be a weak, albeit developing baroclinic boundary upon which deep convection resulted in Mississippi. The RGB imagery above essentially make the forecast process much more efficient and were utilized in several aspects of forecasting this morning. We are eager to get this type of imagery in AWIPS II at some point in the near future.
The MODIS dust and nighttime microphysics products proved very useful during a potent cold frontal passage across eastern NM during the early morning of April 23, 2013. Widespread extreme to exceptional drought conditions have lead to many days this month reporting blowing dust. While most blowing dust cases have occurred during the day, this case is more interesting since the dust occurred at night while low clouds were developing behind the front. The four panel image below illustrates how all the MODIS imagery used together provides better insight into areas of dust versus low clouds. The top left image is the MODIS dust product, the upper right image is the MODIS nighttime microphysics, the lower left is the MODIS 11-3.9micron, and the lower right is the MODIS-GOES hybrid 11micron. The front is clearly visible in the dust product and supported well by the surface observations. Dust at night appears in dark magenta, low clouds light blue in the microphysics product, and yellow in the 11-3.9micron. Visibilities were reported down to 3 to 5 miles around Clovis and Portales and 1.5 miles at Roswell as the front barreled through. Click image to enlarge.
I wanted to point out a couple of Day-Night Band (DMB) observations from the VIIRS instrument aboard the Suomi NPP satellite since we are at full moon. Yesterday, smoke from firest could easily be seen in GOES 4-km visible imagery. However, the loss of visible at nighttime with conventional geostationary imagery makes it nearly impossible to detect smoke plumes at night. The DNB imagery, while just a snapshot from a polar orbiter, at least allows for a check of how phenomena have evolved since the loss of standard daytime visible imagery. Notice the plumes of smoke in the loop of GOES imagery below.
A few of the smoke plumes really stand out: one in SW Arkansas at site KDEQ, one west of McComb, MS and another between Jackson and Hattiesburg, MS. Notice that the smoke plume from the fire in far SE OK was reducing visibility at KDEQ in SW Arkansas. At times, visibility was reduced to 1 3/4 SM, which is within IFR conditions. If this was a Terminal Aerodrome Forecast (TAF) site, this would cause potentially large aviation impacts and a forecaster would want to know about the evolution of the fire and smoke after sunset. Granted, while only serving as a snapshot, the DNB imagery (images 2 and 3 below) show that the fires and smoke in the region had essentially dissipated by the satellite pass at approximately 0751 UTC Mar March 27.
Now, the question might remain, did the smoke actually disappear/dissipate or are the smoke plumes simply not showing up in the imagery? It seems more likely that the smoke/fires had dissipated. Early morning daytime visible imagery just after sunrise (not shown) indicated that the fires indeed had burned out.
Now, for another type of phenomenon…snow.
During the day, clouds may linger over recent snowfall and it can be difficult for forecasters to discern the true extent of the snow. Sure, observations allow forecasters a sense of the extent of snow cover, but may not allow for a sufficient assessment of its true extent. Notice in the short loop below, the clouds moving across recent snow in sections of the Midwest.
In the imagery above, a trained eye can differentiate snow on the ground in portions of eastern Missouri and western Illinois from cloud cover. However, forecasters and others would want to know the extent of snow cover on the ground over the area. The VIIRS DNB Radiance RGB combined with the VIIRS Nighttime Microphysics RGB later that night after clouds had cleared somewhat helped to answer that question.
In the DNB RGB image above (image 5), the snow field is relatively easy to see extending from eastern Missouri into western Ohio. Some clouds still obscure the view and SPoRT’s Nighttime Microphysics RGB product (image 6 above) makes it very easy to distinguish clouds from areas of snow. The low/mid clouds in the area appear as yellows/oranges, while higher, colder clouds appear as deeper magenta/reds. Toggling the two images (as shown in image 7 below) makes the ease of detecting snow vs. clouds apparent.