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.
Archive for the ‘Training’ Category
NWS ABQ continues to research the MODIS RGB airmass imagery and its potential to improve prediction of significant fire weather, wind, and dust events across New Mexico. The MODIS satellite captured a stunning example of a dynamic dry slot within the base of a strong mid latitude cyclogenesis over the central Rockies. Blowing dust in association with the strong jet core sliding directly over eastern NM produced very hazardous conditions for much of the afternoon. The lead meteorologist from Cannon Air Force Base reported visibilities down to around 100 yards at times with the sky completely obscured for roughly 5 hours. This was the worst dust storm for the region that he could remember going back to 2006. He also mentioned the region is about as close to the Dust Bowl as he can imagine with essentially no top soil left after multiple strong wind events already this season and persistent severe to extreme drought.
The heaviest snowfall from the blizzard of February 24-25, 2013 can still be seen on satellite imagery across portions of east central NM. The 1km True Color imagery shows a very well defined area where the heaviest snowfall occurred and the 500-meter Visible imagery from this same area details some interesting terrain features. The satellite images were posted as a Graphicast today and shared via Facebook. The snow pack is still having a significant influence on humidity and temperature forecasts in this area and forecasters continue using the imagery to provide greater accuracy. The snow cover imagery validated the 12 hour snowfall forecast during the heart of blizzard conditions with exceptional accuracy. Snowfall amounts were slightly less than forecast however the areal coverage was pinpointed very well.
A dry slot approaching NM on Friday, February 8, 2013 will deliver a significant blast of high winds, blowing dust, and critical fire weather conditions to portions of central and eastern NM on Saturday, February 9th. The hybrid RGB Air Mass product from 200pm on the 8th shows an exceptionally well defined delineation between moist cirrus over NM and the deep dry slot over the Great Basin. The GOES water vapor stitch was positioned perfectly to show the dramatic comparison of the enhanced detail in the atmospheric composition available on the RGB.
The MODIS NT Microphysics RGB Friday morning October 26, 2012, indicated color difference in the low cloud fields over eastern NM and southern TX. Despite these low cloud layers at relatively similar levels, the atmospheric characteristics in the secondary post cold frontal airmass over NM contrasts the warmer cloud layer over TX. Relatively little impact occurred at airport terminal sites over NM however some very light snow was reported beneath these clouds along the Colorado border.
Yesterday, we posted a series of images of Hurricane Earl, using various spectral bands from MODIS to produce colorful composites that provided image enhancement to illuminate specific features within the imagery. Here, as an example, is how the various channels can be combined to produce the final composite. In this example, data are provided from a nighttime orbit of the Aqua satellite, with a nadir track nearly coincident with the center of the hurricane circulation, providing a clear, high resolution picture of the storm within the MODIS infrared bands. Due to the nighttime orbit, image composites that make use of the visible, solar reflectance bands are not available, and this example uses the “nighttime microphysics” color combinations that require only infrared brightness temperatures and their differences. We will start off with a traditional infrared image of the storm using the 11 um channel:
The final RGB composite is the “sum” of color components representing the basic colors that produce a final pixel color on the monitor: red, green, and blue. In the “nighttime microphysics” enhancement, contributions to the red shades are determined from the difference in the 12-11 micron infrared brightness temperature. To provide additional enhancement, the 256 available intensities of red color are concentrated within a range from -4 to +2 K, or about 0.02 K of precision assigned to each red shade. Values less than -4 K are set to zero (black) and values approaching +2 K increase in red shading, with all values greater than +2 set to the maximum red intensity. In the image below, the “red channel” is shown, with Hurricane Earl prominently displayed. Therefore, the brightest red shades are associated with deep, convective cloud tops. Open water and low clouds still appear as shades of red since they contribute infrared brightness temperatures, but with reduced temperature differences.
Contributions to green intensities are determined from a difference between the 11um infrared and 3.9 um near-infrared brightness temperatures, focusing on a range from 0 to 10 K. The greatest differences are assigned to the brightest green shadings, and here emphasize the deepest convection associated with the core and northern portions of Hurricane Earl. Additional convection is present over northern South America. Lower cloud tops with less convective activity appear in darker green shades, while some of the thinner ice clouds to the southwest of the circulation produce minimal or negative differences and contribute little to the green intensity.
Finally, we have the blue contribution. Blue intensities are provided by the 11 um channel, limited to a range from 243 to 293 K. This image is somewhat similar to a basic infrared image that has not been color flipped. In an image that has not been color flipped, cold brightness temperatures appear black — it is the inverting of the gray scale that provides the traditional “clouds are white” imagery used in operations and on GOES web imagery. Here, high blue intensities correspond to warm temperatures, and black colors appear at cold temperatures associated with cooler cloud top temperatures. Low clouds therefore contribute darker blue (low blue intensity), and open water is bright blue (very warm).
When these colors are combined from each of the R, G, and B panels, the final product is a full range of colors that comprise the “RGB Composite”. Near the circulation center, the active convection contributes high red intensities and high green intensities, which combine to shades of yellow. Some of the granulation and stippling appear due to saturation of the green channel contribution and artifacts of reprojecting the original MODIS data from the swath to the final, mapped area. However, these yellow shades are limited to areas of active convection within the tropical cyclone and also in northern South America. Many of the higher and thinner ice clouds only contributed in the red channel, but not significantly, so that appear as dark shades of red. Meanwhile, open waters contributed to all of the RGB components with emphasis on blue shades, leading to a purple appearance. Low clouds are offset from the remainder of the darker purple background, since they contributed greater amounts to each of the R, G, B components, which tends to lighten the otherwise purple shade. Bottom line — there are a number of imagery features that can be enhanced through MODIS channel composites, and future GOES-R channel differencing, beyond our current capabilities. SPoRT will continue to investigate “best practices” for transitioning these concepts to forecast operations.
Gary Jedlovec and Geoffrey Stano made a visit to the Albuquerque, NM WFO last week to discuss the office’s use of SPoRT forecast products. The ABQ CWA is one of the largest in the country and covers the northern two-thirds of the state. The limited number of surface observation sites and gaps in radar coverage over the region present forecast challenges not always encountered by other offices. The staff of the ABQ WFO regularly use a number of SPoRT products including the MODIS and GOES Low Cloud and Fog products, the CIRA TPW product, and MODIS land surface temperatures. They regularly provide feedback to the SPoRT liaison team on the erformance of the products. They also desire help with minimum temperature forecasts, fire weather support, precipitation mapping and lightning monitoring. SPoRT took this opportunity to provide additional training to ABQ staff members on the use of MODIS and total lightning observations for specific forecast problems. SPoRT is working to make total lighting observations from the White Sands LMA available to the ABQ WFO to help with some of these observational and forecast issues.
Here is a screen shot of the SPoRT created training module on the GOES Aviation Fog Depth product. This particular page of the module shows the use of a NESDIS created enhancement that is applied to the GOES 11-3.9 micron differencing product in order to estimate the fog depth. The training is 16 minutes in length and provides the forecaster with the background on why and how this product can be applied, along with an example from the HUN WFO. Click here to see the module.
One of the first questions that follows a severe weather event (like the one Thursday) is: what happened? And how strong was it? Often, the first thing that comes to people’s minds is a tornado, but as we all know, not all severe weather damage is caused by a tornado.
It falls upon National Weather Service storm survey teams to make the decision. As a severe weather event is coming to an end, NWS forecasters and managers begin to determine strategies for surveying significant storm damage, and assemble teams to examine the damage first-hand. The surveyors are equipped with GPS devices and high-resolution maps, digital cameras, and reference material. The GPS and mapping work is done so that the scope of the event can be understood and catalogued for future research, and the reference material allows survey teams to compare what they see at the time to past surveys or idealized estimates. Radar data and existing reports are also key components of the survey, providing survey teams an estimate of what to expect. (Was there rotation? Was it a line of thunderstorms? How are the damage reports arranged?)
How do we decide if it’s a tornado, a microburst, or straight-line wind damage? It’s tough to describe it in a blog post, but like with many things in meteorology and the National Weather Service, training is required. Meteorologists must take special training modules to be permitted to survey thunderstorm damage, and must have a good idea of the inner workings of the thunderstorm to be able to visualize what may have occurred. Survey teams will often chart what they observe on maps to help with this visualization process and to compare with radar data. However, in general, straight-line winds sweep across an area, affecting multiple locations at the same time; tornado damage is usually more concentrated, possibly appearing somewhat random or occurring on a long, thin path; and microburst damage is a combination of the two, with concentrated damage occurring over a large swath where the storm collapsed and winds spread outward.
Determining the intensity of a storm has become more scientific with the implementation of the Enhanced Fujita Scale in February 2007. The “EF” scale was calculated by engineers and scientists based on extensive testing. It divides what surveyors may see into damage indicators (DI’s for short), which are then divided into degrees of damage (DOD’s). For example, if multiple large branches were snapped in an area of oak trees, that would fall under DI #27, “Tree-hardwood”, and the corresponding DOD would be 2 (Large branches broken, 1-3” in diameter). Based on testing, that yielded wind speeds ranging from 61 mph to 88 mph. If the trees were snapped at the trunk, wind speeds increase to 76 to 118 mph. Surveyors assign an EF-scale rating to tornadoes based on observations of these damage indicators and the degrees of damage.
Depending on the scope of the event, storm surveys can take hours or even days, as the survey team drives around to find damage, and stops to examine the patterns more closely. For example, in the case of the February 6, 2008 outbreak where two EF-4 tornadoes occurred, surveys occurred over a period of several days, including multiple trips to the damaged areas, aerial surveys to determine the extent of the damage, and consulting with experts with decades of experience. Conversely, weaker, shorter-lived tornadoes like the ones that occurred on April 2, 2009, required the work of two teams (due to the locations of the storms) over roughly half a day.
We hope to have more “inside the NWS” posts in the future to clear up some of the mysteries of NWS actions and operations. In the meantime, here’s hoping we spend less time on this particular duty over the coming weeks.