During the weekend of Mar 02-03 2014, several weather features moved northeast across the area. The precipitation started out as rain across West Virginia with some freezing rain, sleet and snow across portions of southeast Ohio. Colder air began to filter into the region and as it did, the precipitation changed from rain to freezing rain to sleet and finally to snow. By 603 AM, the precipitation had turned to snow across all of West Virginia, but for portions of the extreme southeast counties.
I have attached two images from around 6 AM on Mar 3rd. The first image showed the radar data from KRLX at 603 am while the second image was the 607 am SFR product and 6 AM surface observations. When comparing these images, the “best” SFR signal for heavy snow was located along a line where the precipitation transitioned from freezing rain to snow. The heaviest signal in the SFR images was actually located over Mingo County where a total of 8 inches of snow was reported from the storm.
Freezing rain was falling across portions of extreme southeast West Virginia. Bluefield WV (KBLF) is located southeast of the “SFR” heaviest snow signal in an area where the SFR product is not showing anything. The SFR product did a great job across that area as the 6 AM KBLF observation indicated freezing rain was falling at that time.
Posted in Data Assimilation, Training | 1 Comment »
Well, it’s February and it’s the East Pacific off of California, so the short answer is no. But. . .what an amazing structure, right? We haven’t seen anything this good looking in the tropical Atlantic in years! But I digress. . .
MODIS RGB Air Mass product valid at 0621 UTC on 02/28/14. The blue lines are the boundaries of OPC (north), TAFB (south), and Hawaii (west)
MODIS RGB Air Mass product valid at 1032 UTC on 02/28/14.
The first image was collected four hours before the second image and you can see how the center of the intense storm developed an “eye-like” feature (images courtesy of NASA SPoRT). Notice the distribution of the pinks and reds in both images as well. That is dry, stratospheric air filling the center of the strong upper-level low (~300-500 mb). The second area shows an additional area of pink approaching the southern California coast. This area is associated with strong instability that has led to rare California thunderstorms.
So, how do we know if there is stratospheric air?
AIRS Total Column Ozone product valid at 2200 UTC on 02/27/14.
AIRS Ozone Anomaly Product valid at 2200 UTC on 02/27/14.
The first image above is the AIRS Total Column Ozone product developed at NASA SPoRT. The color bar on the left is not correct. The main idea is that the warmer (cooler) the colors, the more (less) ozone is in the atmospheric column. The green colors indicate ozone levels above 200 Dobson Units (ozone unit of measurement) with the magenta areas indicating ~500 Dobson Units. The second image shows the AIRS Ozone Anomaly product with the first level of blue indicating 125% of normal, while the yellow region indicates >200% of normal ozone at that latitude and geographic location. Stratospheric air is associated with high levels of ozone and potential vorticity which can help identify the strength of the upper-level low. These images show the connection of this ozone pocket with the “reservoir” of ozone located in the northern latitudes at this time of year.
AIRS Total Column Ozone Product valid at 1000 UTC on 02/28/14.
AIRS Ozone Anomaly valid at 1000 UTC on 02/28/14.
As the upper-low cut off and became stacked over the surface low (~971 mb), you can see how the high concentration of ozone becomes more focused over the storm. Once again, the magenta coloring indicates ozone levels >500 Dobson Units. The anomalies are more incredible with a large area of >200% of normal directly west of southern California.
I will continue to work with forecasters at OPC, TAFB, SAB, and WPC on discovering ways to use these products in conjunction with the RGB Air Mass products to gauge storm strength and look for signals upstream of developing tropopause folds and stratospheric intrusions.
GOES-15 Visible imagery with the GLD-360 30-minute lightning density product overlaid.
The ozone isn’t the only impressive part of this storm. Notice the occasional bursts of lightning within the spiral bands of the parent storm. Although not completely unusual, this is a great indicator of how much energy is available to this storm.
GOES-Sounder RGB Air Mass product with GLD-360 lightning strikes overlaid.
I put together a longer animation of the GOES-Sounder RGB Air Mass product with the GLD-360 lightning strikes overlaid. Note the first system that came ashore in California earlier this week, then moved over the four-corners regions with plenty of lightning, especially for this time of year. The current storm is seen lurking offshore with more lightning developing in a band of thunderstorms that moved from Los Angeles to just north of San Diego. This system will be responsible for the next bought of winter weather for the Midwest to the Mid-Atlantic next week.
Thanks for reading and as always, feel free to contact me with questions and feedback!
Posted in AIRS, GOES-R Proving Ground, JPSS Proving Ground, MODIS, RGB | 1 Comment »
A weather system moved across the area during the overnight hours into the morning hours on Feb 26 2013. As a result…a band of snow developed and moved southeast. As of 8 AM…most locations were reporting 1.5 to 2.5 inches…with some higher anmounts.
I have attached two images from approximately the same time. The first image shows a radar mosaic from 1024 UTC for West Virginia and surrounding areas while the second image is an SFR image from 1022 UTC. The radar mosaic shows the heaviest snow across eastern Kentucky into the southern counties of West Virginia. The SFR image shows the best signal for snow across northern portions of West Virginia. Surface observations generally showed the heavier snowfall…based on visibility…was falling from eastern Kentucky across southern West Virginia into the northeastern West Virginia counties.
Each dataset had it’s strengths and weaknesses. However, using a combination of all three datasets was the best method to show the overall coverage of the heavier snow.
Posted in Uncategorized | 1 Comment »
GOES IR (left), NESDIS Snowfall Rate Product (center) and Composite NEXRAD Base Reflectivity (right) for around 1045 UTC 28 January 2014.
In the early morning hours of 28 January (approximately 1047 UTC or 4:47 AM CST), the Operational NESDIS Snowfall Rate Product (SFR; above center), that uses the Advanced Microwave Sounder Unit (AMSU-A) and Microwave Humidity Sounder (MHS) on-board four Low Earth Orbiting (LEO) NOAA POES and EUMETSAT Metop satellites to produce a liquid equivalent snowfall rate over land, was detecting snow in the clouds over Central Alabama (red circle) and an area from northern Mississippi into Central Tennessee (yellow oval). In both areas there was some enhanced cooler cloud tops on the geostationary infrared imagery (above, left) and light precipitation detected by the composited NEXRAD base reflectivity (above, right) in approximately the same area that the SFR was detecting snow in the clouds. However, the only snow being observed (light snow at that) at the surface at the time was in Northwest Mississippi at Tunica Municipal Airport. The SFR has a known high bias for sensing low liquid equivalent rates/light snow and so forecasters need to understand that just because the product is sensing snow in the clouds, the relatively low moisture that may exist close to the surface at the start of an event can initially prevent the precipitation from reaching the ground. Now let’s focus on the Central Alabama snow being detected by the SFR at 1047 UTC in the enhanced satellite geostationary IR cloud tops and aloft by the radar. At this time no snow was being observed around the Birmingham, Alabama area. Still the SFR would have provided valuable information to forecasters that the snow detected in the clouds could be seeding existing clouds (a precursor) and with increased moisture more easily support snow eventually reaching the ground later in the morning. This is what actually occurred as Birmingham-Shuttlesworth International Airport started to observe snow reaching the ground shortly before 16 UTC (10 AM CST) and was confirmed by the approximate 1615 UTC SFR (below, center), GOES IR (below, left) and composite NEXRAD (below, right) imagery/data; about 5 hours after the 1047 UTC SFR was detecting snow in the clouds. NESDIS researchers and analysts are carefully looking at the SFR product’s sensing of the snow in the cooler enhanced IR cloud tops as a precursor to snow eventually reaching the ground; thus helping alert forecasters to the impending snow reaching the ground. And in this case once the snow started reaching the ground in the Birmingham area just before 16 UTC, its intensity increased through the rest of the morning and into the afternoon on the 28th (snow-water equivalent reached 0.03″ through 18 UTC and an additional 0.05″ fell between 18 and 21 UTC .
GOES IR (left), NESDIS Snowfall Rate Product (center), Composite NEXRAD Base Reflectivity (right) for around 1615 UTC 28 January 2014. Black Circle depicting snow in and around Birmingham, Alabama.
Posted in Uncategorized | 2 Comments »
VIIRS DNB Reflectance RGB within AWIPS/D2d for 17 February 2014 at 0905 UTC over the Colorado, Wyoming, Nebraska, Kansas region
The VIIRS Day-Night Band (DNB) RGB imagery from SPoRT uses the DNB channel for both the red and the green components of the RGB, and then the single channel 11 micron band for the blue component. So warm, reflective clouds have both red and green and result in a shade of yellow while cold, reflective clouds appear in shades of blue to white. The image above from 17-February-2014 has a mixture of yellow, blue, and white objects, but the question is: Are all of these areas clouds? Some of the city lights appear to be distinct, sharp yellow points on the ground with little diffusion of light through clouds even though they are surrounded by shades of yellow. Notice the area at the intersection of the CO, WY, and NE borders as well as some of the inter-mountain regions of western Colorado and how the city lights in these regions are not blocked, nor spread over a large area due to scattering by the clouds.
VIIRS Nighttime Microphysics RGB within AWIPS/D2d for 17 February 2014 at 0905 UTC over the Colorado, Wyoming, Nebraska, Kansas region
The Nighttime Microphysics RGB imagery from VIIRS is provided above as a comparison to the DNB. Using this RGB one can identify areas of clouds and their type. Several of the areas in question turn out to be surface features as opposed to clouds. This realization that clouds do not exist in some of the yellow shaded areas of the DNB as well as the fact that city lights are not scattered in these regions, leads one to conclude that the DNB is showing snow on the ground. Several areas are labeled as “Snow Cover”. However, note that some clouds do exist. In fact some low clouds in the inter-mountain west of Colorado are evident in yellowish-green tones, and low- and mid-level clouds are highlighted in northwest Kansas and northeastern Colorado. The Nighttime Microphysics RGB also hints at the potential of fog in southeast Colorado with dull gray to shades of aqua. Perhaps snow cover has melted to some extent to provide a moist ground with clear skies overnight that resulted in some very thin, to scattered fog or low clouds. Below are images of the same time but over a wider area in order to provide greater perspective. Note that much of the yellow shaded areas in the DNB RGB are the result of snow cover vs low cloud features. Hence VIIRS demonstrates valuable insight to both clouds and surface features at night via reflected moonlight.
VIIRS DNB RGB within AWIPS/D2d for 17 February 2014 at 0905 UTC over the western U.S.
VIIRS Nighttime Microphysics RGB within AWIPS/D2d for 17 February 2014 at 0905 UTC over the western U.S.
Posted in VIIRS | Tagged Day-Night Band, DNB, fog, low clouds, nighttime microphsycis, ntmicro, Snow Cover, VIIRS | 1 Comment »
The Huntsville County Warning Area received widespread 3-5 inch snowfalls Wednesday night, with a few sites reporting as high as 10 inches! While it’s melting quickly today with temperatures in the mid and upper 30s, the snow cover did hang around long enough to be captured by the mid-morning MODIS pass (though we are on the very edge of the pass, so the bowtie distortions are noticeable). That might be nothing new, but this is the first time we’ve been able to view such imagery in AWIPS II.
MODIS Snow/Cloud RGB Image valid 1546 UTC 13 February 2014
MODIS True Color Image valid 1546 UTC 13 February 2014, viewed in AWIPS II CAVE
The Snow-Cloud RGB is particularly illuminating, as it effectively illustrates the downslope-induced cloud breaks over northern Georgia.
Great job to the SPoRT AWIPS II team on helping us get these data back into AWIPS! There are still some kinks to work out, but this essentially restores the SPoRT data feed that was in place before our A2 upgrade in June 2012.
Posted in AWIPS II, MODIS | 3 Comments »
SPoRT continues to work with select NWS WFOs in evaluating the NESDIS SFR product.
One thing to take into consideration when using data from “whisk-broom” instruments on polar-orbiting satellites, such as the Advanced Microwave Sounding Unit (AMSU) used to generate the SFR product, is that data at the edge of the swath (i.e. limb) may provide misleading or erroneous observations. As the instrument scans farther from nadir, it is looking through more of the atmosphere, creating both a bigger observation field of view (i.e., larger pixel) and having the signal attenuated by more atmospheric constituents (e.g., in-cloud and falling snow). As a result, when interpreting the SFR product, it is important to look for the extent of the swath (outlined in gray in the product in AWIPS) to determine whether the observed SFR is going to be limited by these limb effects.
Let’s take a look at an example over the NY Tri-State area for the post Super Bowl snow event. In the first image, from Metop-A valid at 1458 UTC, there is a large area of snowfall across the area. The heaviest SFRs appear to be around 1.2-1.5 in/hr (when multiplying the liquid equivalent by 10) across central and southern New Jersey. However, an hour later (see second image from Metop-B valid at 1554 UTC), the shape of the heaviest SFR has expanded north and west and there are now readings over 2.0 +in/hr. Other areas that had a SFR of less than 0.5 in/hr in the 1458 UTC image, appear to have a SFR of around 1.0 in/hr just an hour later, which is a large jump in intensity.
While it is certainly possible that the snow evolved and intensified in less than an hour, it is more likely that instrument limb effects are likely to blame for the larger SFRs in the second image. Make sure to check that swath edge when using polar-orbiting satellite data!
NESDIS SFR Product from 1458 UTC on 3 February 2014 showing snow detected near nadir for Metop-A.
NESDIS SFR Product from 1554 UTC on 3 February 2014 depicting what are likely erroneous higher intensity SFR values along the swath edge from Metop-B.
Posted in Passive Microwave, QPE, Training | 5 Comments »