Brian Bernard runs a website in Southern Canada called Golden Horseshoe Weather. Brian obtains near real-time sea surface temperature (SST) and green vegetation fraction (GVF) products from SPoRT for ingest into a version of the Environmental Modeling System (EMS) that he runs. This model is a 4-km Advanced Research Weather and Research Forecasting (WRF-ARM) model that encompasses Southern/Central and part of Northern Ontario. It uses 40 vertical layers, with most of the layers between 1013 to 650 mb in order to better resolve lake-breeze boundaries and lake effect areas. As a result, use of the high-resolution SPoRT SST data is critical for resolving some of these boundaries.
Southern and Central Ontario is bounded by water on three-sides and one of the forecasting challenges for the meteorologist is the interaction of the marine layer and the land area. Most of our severe thunderstorm events occur during interactions with lake-breeze boundaries. In winter, parts of Southern/Central and Northern Ontario are downwind in cyclonic flow events and are susceptible to lake-effect snows. Areas downwind of Lake Huron can also be affected by multi-lake effect snows.
Brian posts numerous output fields from his real-time WRF runs to a modeling subsection of his website, which is frequented by Canadian, provincial, and U.S. government meteorologists, private sector and media meteorologists, as well as weather enthusiasts and storm chasers. The model is initialized daily at 00Z and run for 36 hours; output is generally available by 1:00 A.M. local time.
A recent lake-effect snowfall event in Southern Ontario was captured well by WRF with the inclusion of the SPoRT SST. The 24 November 1200 UTC radar image from the King City radar in Ontario shows two distinct lake-effect snow bands (one southwest of Barrie and Midland; one near London). The corresponding 36-hr WRF forecast (initialized at 0000 UTC on 23 November; valid at 1200 UTC on 24 November) of 900 mb omega shows that the strongest vertical motions associated with snow bands occurred almost exactly in the location of the two snow bands observed in the radar.
Radar reflectivity (dBZ) from the King City radar from 1200 UTC (left) and Exeter radar from 1210 UTC (right) on 24 November 2013 showing two distinct lake-effect snow bands over Southern Ontario.
36-hr WRF forecast of low-level vertical velocities valid at 1200 UTC on 24 November 2013. The larger magnitude vertical velocities are snow bands.
In addition to his use of the SPoRT data for modeling applications, Brian also obtains satellite imagery products from SPoRT’s publically-accessible FTP server and generates relevant imagery over Southern Canada for his website users. As an additional verification of this snow event, Brian used SPoRT’s MODIS false color snow cover product to compare with forecasted snow depth output from WRF. In the false color image below, the red areas outline where there is snow on the ground, and the outline of the fallen snow matches very closely with the areas where snow was forecasted to fall in the 36-hr forecast. While the MODIS false color product is unable to provide any quantitative information about snow depth, the MODIS image is annotated with reports from the two areas where the heaviest snowfall occurred. The heaviest snowfalls in the 36-hr WRF forecast also match nicely with the bull’s eyes of where the heaviest snowfall was reported.
MODIS false color imagery from 1640 UTC on 24 November 2013 showing the extent of the snowfall that occurred during this lake-effect snowfall event over southern Ontario. The red areas indicate snow on the ground. The circled areas with annotations show the areas of the heaviest reported snowfall.
36-hr WRF forecast of model snow depth valid at 1200 UTC on 24 November 2013. The spatial extent of the snow on the ground and largest snowfall areas over southern Ontario coincide with what is seen in the MODIS false color image and snowfall reports.
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A ridge of high pressure moved into the desert southwest in the wake of a strong winter storm system that impacted the region last weekend. Strong low level inversions beneath the ridge and melting snow cover increased the potential for an extended period of low clouds and freezing fog. The MODIS Nighttime Micropyhsics product valid at 0501 UTC November 29, 2013 showed low clouds and possible areas of freezing fog along the I-70 corridor over and west of Grand Junction. Observations at Grand Junction verified IFR low clouds at 900′ with visibilities above 6 miles. The following VIIRS Nighttime Microphysics product at 0904 UTC November 29, 2013 showed low clouds and freezing fog expanding eastward into the Colorado, Gunnison, and Uncompahgre River Basins and the Grande Valley south of Grand Junction. Visibilities have been significantly reduced to 1/4 mile at Montrose and farther south at Cortez. The ceiling at Montrose is 200′ with visibility at 3/4 mile. The nighttime microphysics product shows exceptional detail within the narrow valleys along Roan Creek to the northeast of Grand Junction. Notice the fog and low cloud deck is very close to Rifle at 0904 UTC but the observation still suggests clear skies. 31 minutes later at 0935 UTC the observation at Rifle dropped to LIFR at 400′ however visibilities remained at or above 6 miles.
MODIS NT Microphysics product valid at 0501 UTC November 29, 2013.
VIIRS NT Microphysics product valid at 0904 UTC November 29, 2013.
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The SPoRT LIS soil moisture data have continued to be useful at NWS Huntsville, as a tool for assessing drought and flooding potential. Recently, forecasters found utility in assessing the threat for flood potential leading up to a heavy rain event forecast for the area. A “typical” 2-3 inch rainfall event, even in the cold season, can lead to some instances of localized flooding, especially if embedded convection exists. Nevertheless, just stratiform rain events of this magnitude can cause gradual rises of streams and minor flooding if antecedent soil moisture values are relatively high. So, in order to get a more quantitative understanding of soil moisture amounts, forecasters have come to rely on the SPoRT LIS data. On Nov 25th, as moderate to heavy rain was approaching the area, one of the Huntsville forecasters consulted the LIS data to determine soil moisture values and the flooding threat. In her forecast discussion, she noted, “THE AXIS OF HEAVIEST PRECIP IS CURRENTLY FORECAST TO EXTEND FROM AROUND TUSCALOOSA UP ACROSS THE SPINE OF THE APPALACHIANS…WITH AMOUNTS ACROSS OUR CWA RANGING FROM 1.5-3+ INCHES. CULLMAN/MARSHALL/DEKALB COUNTIES WILL BE MOST LIKELY TO SEE THESE 3+ INCH TOTALS. WITH 3 AND 6 HR FLASH FLOOD GUIDANCE OVER 2 INCHES ACROSS THE CWA…AND DRY SOILS INDICATED IN THE NASA LIS DATA…THIS SUGGESTS WE WILL BE ABLE TO HANDLE MUCH OF THIS RAINFALL SINCE IT WILL BE OCCURRING OVER THE ENTIRE DAY.” The following grapics show the shallow and deep layer relative soil moisture on the morning of Nov 25th, before much of the heavy rain began to affect the area.
Image 1. SPoRT LIS 0-10 cm relative soil moisture 0600 UTC Nov 25, 2013
Image 2. SPoRT LIS Column-Integrated (0-200 cm) Relative Soil Moisture 0600 UTC Nov 25, 2013
Notice that values in much of north central Alabama, in the area of expected heaviest rainfall, were around 30 to 45%. Although still somewhat anecdotal and subjective, local use has shown that values under 50% during a typical 1-3 inch stratiform rain event will not lead to flooding, or only very isolated instances of minor flooding. Forecast rainfall amounts were on target, as about 1.5 to 3 inches resulted across the area. No flooding was reported. The next graphic shows the deep layer soil moisture as of this morning. Soil moisture values even after the heavy rainfall of 2-3 inches in portions of north central Alabama only climbed to about 40 to 50%.
Image 3. SPoRT LIS Column-Integrated (0-200 cm) Relative Soil Moisture 0600 UTC Nov 28, 2013
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A strong winter storm system that impacted NM over the weekend delivered the first round of significant widespread snowfall for the 2013-2014 winter season. Major impacts to travel were reported across much of the area along with record to near record cold temperatures. The VIIRS DNB Reflectance imagery after the storm showed several interesting features over the area. Crisp city lights over central and eastern NM on top of areas of light yellowish reflectance values contrast the more blurred city lights over western NM with the same light yellowish reflectance. The VIIRS Nighttime Microphysics from the same time provides much better insight into what is happening over the region. Thick low clouds are detailed very well over western NM while central and eastern NM remain clear.
The MODIS Snow Cloud RGB product dives even deeper into the story. Much of central and eastern NM are snow covered and several well defined snow bands can be seen. There are even some low clouds still hanging tough over northwest NM. The composite radar reflectivity from the 24th shows how these snow bands set up over the area. Minor impacts to aviation occurred over western NM as MVFR conditions impacted Farmington and Gallup with 12 to 24 hours of broken ceilings.
Posted in JPSS Proving Ground, MODIS, RGB, Training, VIIRS | 1 Comment »
Strong winds have been occurring for the last several days in the Gulf of Tehuantepec of the eastern Pacific Ocean, to the south of eastern Mexico. These strong gap winds result from cool high pressure systems that surge southward through the western Gulf of Mexico, with the air funneled through the relatively lower elevation of Chivela Pass in eastern Mexico (Fig. 1). These high winds have been nicely depicted by the Weather Research and Forecasting (WRF) model runs produced through a collaboration between SPoRT and NASA/SERVIR, as shown by the 30-h forecast maximum hourly 10-m wind speed in Fig. 2, valid on 1200 UTC 12 November. A corresponding image of WindSat retrieved winds is shown in Fig. 3 for roughly the same time as the WRF model forecast.
The SPoRT/SERVIR WRF model forecasts over the Caribbean and Central America are unique in that the model runs are generated daily in real-time using cloud computing resources. The model runs are initialized at 0600 UTC, ingest SPoRT sea surface temperatures in the initial conditions, and are integrated out to 48 hours. The team is working to migrate the model output to a real-time web map service.
This latest surge of cold air impacting the U.S. Deep South today will continue unabated into the Gulf of Tehuantepec over the next day or so. Today’s SPoRT/SERVIR WRF model run suggests a substantial increase in the wind speeds to over 20 m/s by 0600 UTC 14 November (Fig. 4). Winds are forecast to exceed 20 m/s from about 1500 UTC 13 November through 1200 UTC 14 November. The National Hurricane Center’s Tropical Analysis and Forecast Branch put out an experimental graphic indicating this expected increase in wind speeds and accompanying high seas in the eastern Pacific Ocean (Fig. 5).
Figure 2. Thirty-hour forecast of maximum hourly 10-m wind speed (m/s) from SPoRT/SERVIR WRF model run, valid at 1200 UTC 12 November 2013.
Figure 3. Image of retrieved WindSat winds valid 1225 UTC 12 November 2013, courtesy of the Naval Research Laboratory.
Figure 4. Twenty-four hour forecast of maximum hourly 10-m wind speeds from the SPoRT/SERVIR WRF model, valid 0600 UTC 14 November 2013.
Fig. 5. Experimental Graphical Forecast produced by NHC’s Tropical Analysis and Forecast Branch, valid through 0000 UTC 14 November 2013.
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NASA provides high spatial resolution sensors that can be used to identify significant areas of urban, land surface, and coastal change following disasters. SPoRT is investigating the use of this type of imagery for the analysis of tornado and hail damage tracks within the continental United States, but has also obtained imagery (via the USGS Earth Explorer and Hazards Data Distribution System) over the Tacloban City area, particularly hard-hit by Super Typhoon Haiyan. Whereas MODIS (250 m) and VIIRS (350 m) each have a moderate spatial resolution and large swath width and view the surface a couple of times per day, ASTER and the Landsat-8 Operational Land Imager provide a higher spatial resolution (15 m, 30 m) but with less frequent collection. Below are some examples of true color Landsat-8 imagery, similar to the interpretation of aerial photography, and a natural color image from ASTER. Natural color imagery attempts to replicate the overall quality of a true color image with green vegetation, blue water, and grayish urban areas, but ASTER lacks the specific R, G, B visible wavelength bands required for a “true” true color image. By comparing relatively cloud free Landsat-8 data from July and data collected today from ASTER, areas of significant change can be identified by changes in color and texture. These correspond to surface changes, such as vegetation damage or disruption of the typical pattern of road networks due to surface debris. In mountainous areas, there may also be indications of river flooding, though the overall darkening of pixels in the region may also be caused by cloud shadows that complicate the analysis. NASA has several ongoing projects related to disaster analysis and response activities, extending the societal benefits of on-orbit sensors. SPoRT seeks opportunities to leverage these assets to benefit end-user decision making, in collaboration with other NASA researchers and the broader scientific community.
Landsat-8 false color composite over the Tacloban City area from July 2013. Red areas indicate significant vegetation, dark blues as water, clouds in white, and less vegetated or urban areas in shades of gray to cyan.
ASTER false color composite from November 13, 2013. Changes in color, such as changes from reds to grays, or reds to dark blues, and other changes in texture identify possible flood or damage areas following the storm when compared to Landsat pre-storm image.
Landat-8 true color image of the Tacloban City area acquired on July 9, 2013.
ASTER natural color imagery from November 13, 2013 and some areas of change in color and or texture versus the Landsat-8 true color imagery. Some cloud contamination (shadowing) and thin clouds or haze across the area also contributes to changes in color and reflectance. Note that natural color is an approximation of true color capabilities.
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