A strong cold front is ushering in markedly colder air for much of the central and eastern U.S. over the next several days. The cold front today is highlighted by extreme temperature contrasts over the Southern Plains, with high winds and blowing dust along and behind the front as it surges southward through Colorado and Kansas. Figures 1 and 2 show the VIIRS dust RGB images over the Plains at 1906 to 2049 UTC, respectively. One can easily identify the increase in dust coverage (given by the darker pink colors) by 2049 UTC over southeastern Colorado as the front propagates southward. A corroborating surface analysis valid at 2043 UTC in Figure 3 depicts visibility reductions at Lamar, CO (LAA; 2 miles), La Junta, CO (LHX; 1 mile), and Pueblo, CO (PUB; 3 miles) in southeastern Colorado. Notice temperatures in the 80s across the Oklahoma and Texas Panhandles, while temperatures are in the 20s and 30s across northeastern Colorado and northwestern Kansas. Quite the contrast!
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SPoRT has been investigating options to obtain near-real time NUCAPS (NOAA Unique CrIS and ATMS Processing System) data to expand the ozone products to Suomi NPP retrievals. The AIRS ozone products cover a Northwestern Hemisphere domain (Link to SPoRT AIRS products) and were specifically created for the National Centers (WPC and OPC) to aid interpretation of the Air Mass RGB for identifying and forecasting stratospheric intrusions that can lead to rapid cyclogenesis and hurricane-force wind events in the North Atlantic and North Pacific Oceans. The AIRS data are obtained from NASA Land Atmosphere Near-Real Time Capability for EOS (LANCE), rather than Direct Broadcast, so that the products can be created in hourly swaths that cover the OPC domain. Since the ozone products are created from polar-orbiting retrievals, forecasters are eager for better temporal and spatial resolution. Use of retrievals from newer instruments such as Suomi-NPP CrIS/ATMS can provide additional overpasses to improve spatial and temporal resolution when paired with AIRS.
Suomi NPP data are available on the NOAA Comprehensive Large Array-Data Stewardship System (CLASS). Typically data are obtained from CLASS by choosing options such as data type, domain, and time on the website and placing an order. Depending on the size of the order, it can take about an hour to 24 hours for your request to be processed and ready for download via ftp. Manually placing an order is not an optimal approach for near-real time data processing and product development.
Recently SPoRT investigated the CLASS subscription service and has had success in obtaining NUCAPS data with a 2-3 hour latency. The CLASS subscription service is a valuable tool, comparable to NASA LANCE, for obtaining near-real time NUCAPS data. Others in the community who are interested in obtaining NUCAPS data with reduced latency and need a larger domain than what is available from Direct Broadcast should investigate the CLASS subscription service. Below is a outline of steps to set up a CLASS subscription for NUCAPS data.
First go to CLASS, create a user account and sign in. Click on “Subscriptions” in the left side menu. Choose your data product from the dropdown menu and click “Add New” to begin setting up the subscription details. For NUCAPS choose S-NPP Data Exploitation Granule Data (NDE_L2)
Next, set up the search criteria for your subscription by choosing the domain either by making a box on the map or entering latitude and longitude values beside the map. Click on the box next to “NUCAPS Environmental Data Records” and click on “S-NPP”. Click on “Delivery Options” to continue.
Last set up the delivery options. Choose “yes” for a recurring schedule and set the start and end dates. The start and end dates do not include the year, therefore you’ll need to modify the start and end date as the end of the year approaches. Choose whether or not you want email notifications. I would initially choose “yes” so you can start to gauge how quickly your subscription is being processed from the time your data arrives in CLASS. Note that you will get an email for every granule and sometimes the email notifications are delayed quite a bit after your data is ready. The notifications are initially helpful as you first set-up your subscription. As a side note I did enjoy spamming myself with approximately 20-30 CLASS email notifications per hour when I first set up my subscription so I could see how it was working and could gauge the data latency. Most important, choose how often you want to receive data in the dropdown list beside “Include delivery manifest”. I’ve chosen “Every 1 hour”, but depending on the product and your needs, you can choose any interval from 1-24 hours. Features such as the digital signature and checksum aren’t always necessary but you can decide if you need them by reading about them on the class help pages. Now click “Save” to finish.
Once your subscription is set up, you can log in at any time to view, modify, or disable your subscription. Just click on “Subscriptions” on the left side menu after you have logged in.
Once your data arrives in CLASS your order will be processed. Therefore the subscription service can provide automatic distribution of near-real time products as long as the data is arriving in CLASS near-real time. If the data is not pushed to CLASS near-real time by the product developer or NDE than the subscription service can’t be used for near-real time purposes (unless you don’t mind a 6-24 hour or longer latency). Not all Suomi NPP products are pushed to CLASS in a real-real time capability. Thankfully NUCAPS is pushed to CLASS relatively quickly after it is processed and can be obtained via CLASS near-real time. Your subscription will have a unique ID and your order will be available on the ftp site in a directory named with your username and subscription ID. The data will also be available via a unique http site named with your username and subscription ID. Now your data is in one place and can be accessed via scripting and ftp without manually submitting an order on CLASS.
Latency of products getting to CLASS and figuring out how to order data without manually submitting an order on the website have been the largest deterrents for SPoRT using CLASS data for real-time product development. Not all Suomi NPP data is immediately pushed to CLASS near-real time, however contacts at NESDIS have indicated that in the next 6-months or so, more Suomi NPP data will be pushed to CLASS in near-real time mode. Utilizing the CLASS subscription service opens up a new opportunity for SPoRT and the community to use NUCAPS data (and in the near future, other Suomi NPP data sets) from CLASS for product development.
More information on CLASS subscriptions can be found within the CLASS help pages.
One night after a widespread dense fog event, we have been monitoring more fog formation very closely. Unlike the previous night, the visibility has not fallen quite so far, so fast at most of the airports across the Tennessee Valley; just a few sites in typically fog-prone valleys are reporting visibility of less than 1 mile. However, coverage is the question, and the default 11-3.9 micron satellite imagery was not particularly helpful in diagnosing that. There are hints of fog in the valleys of northeastern Alabama, but it’s tough to be sure how widespread the fog might be.
The Nighttime Microphysics RGB imagery was much, much more useful–and confirmed what the surface observations were telling us. The 0802 UTC pass indicated that much of the fog is confined to the river valleys in and around the Huntsville CWFA, especially in the northeast Alabama valleys and the Elk River around the Tennessee-Alabama border (near where the mouse pointer is located). Furthermore, the fainter gray-cyan colors surrounding the Tennessee River (bisecting the CWA) supported some of the less-dense fog reports coming from airports such as Muscle Shoals (KMSL) and Huntsville (KHSV).
This imagery helped confirm the surface observations, and helped with the decision to avoid a widespread dense fog advisory–at least temporarily.
Starting around 07Z last night, we noticed a station in the far northeast corner of Colorado reporting some reduction in visibility, with no other stations nearby reporting any reduction. We couldn’t see any indication in the 11u-3.9u IR satellite imagery. Once the VIIRS DNB imagery came in of the 09:04UTC imagery set, it was definitely evident in the Nighttime Microphysics channel, slightly in the Dust RGB channel, but not at all in the other DNB channels. Good to know the sensor was reporting correctly!
Seen above, top to bottom: VIIRS DNB Reflectance RGB, IR Longwave, Dust RGB, Nighttime Microphysics imagery. The latter definitely shows the small patch of fog clearly with the whiter (lower) clouds.
A cooler, drier continental airmass was moving into the Tennessee Valley on the evening of Sunday, September 21st. Showers and a few thunderstorms developed along the associated frontal boundary as it crossed into the Huntsville County Warning and Forecast Area late in the afternoon and through much of the evening. One thunderstorm began to strengthen as it crossed from the Lynchburg, TN area into northwestern portions of Franklin County, TN (Image 1). The total lightning data, in fact, provided the first indication that this cell was undergoing strengthening. Notice the “spike” in data, particularly beginning at 2153Z, when values jumped from a moving average of around 50-100 to over 200.
Severe weather was not expected this evening, with somewhat unfavorable environmental conditions. Nevertheless, cells during the late afternoon were being watched for incidences of strong winds (up to about 40 mph), small hail and frequent lightning. The “spike” in the lightning data was the first indicator that this cell was undergoing strengthening and prompted heightened situational awareness and thus closer inspection of radar data. A special weather statement was issued for this cell at 2204Z. Had it not been for the total lightning data running and viewable in the AWIPS II window, a closer inspection of this cell may not have been prompted until later. These data have proven beneficial to operations for over a decade now at the Huntsville NWS office, and will continue to be a integral part of operations here for some time to come.
The Air Mass RGB imagery product via MODIS has often appeared to lack “green” coloring near the edge of the swath and there have been noticeable differences between the channels from Aqua and Terra used within the RGB. Forecasters from the Great Falls, MT and Albuquerque, NM WFOs applying this experimental data noted these issues. The above image is a limb and bias corrected version of the Air Mass RGB. The water vapor and ozone channels tend to “cool” near the swath edge as they pass through more atmosphere and the differences in satellite instrument quality result in physical characteristics between the images having different coloring. SPoRT has worked to develop a non-linear function to correct much of the limb cooling as well as a bias correction, both through comparison of the MODIS instruments to the EUMETSAT SEVIRI instrument. Annotations to the image attempt to classify the various features indicated by the resulting composite color during a MODIS pass from 1859 UTC on 13 May 2014 when a cold air mass was moving into the upper Midwest. Simple interpretation guides can be found via SPoRT’s Training page or EUMETSAT. For comparison, additional plots of GOES Water Vapor, and NAM 500mb Temperature, Humidity, and Height 0-hour analysis and 6-hour forecasts are provided below for reference. There is also a single image of the Hybrid GEO/LEO Water Vapor / Air Mass RGB product that loops GOES Water Vapor imagery and inserts the MODIS Air Mass RGB swath as it is available because the RGB is largely made up of water vapor channels. Both the Hybrid and single-swath MODIS files are available in netCDF format for use in AWIPS I or II as well as KML format.
This new limb/bias corrected Air Mass RGB product is credited in large part to graduate student work being done at the University of Alabama Huntsville in conjunction with NASA/SPoRT. Primary contributors are:
Nicolas Elmer (UAH graduate student)
Dr. Emily Berndt (NASA/SPoRT Post-Doctoral Scientist)
Dr. Gary Jedlovec (NASA/SPoRT PI)
Additional contributors include:
Frank LaFontaine (Raytheon, Data processing and analysis)
Kevin McGrath (Jacobs, Product code development and real-time processing)
Matthew Smith (UAH, Data processing and product code development)
Dr. Andrew Molthan (NASA/SPoRT, RGB code development and research science)
NAM 500mb, 0-hour forecast valid 1200 UTC, 12 May 2014 of Temperature, Humidity, and Height via
CAR RAL website
Despite the hours of darkness becoming rare over Alaska as the northern hemisphere approaches its summer solstice, the RGB Night-Time Microphysics product still has some utility in Alaska south of the Arctic Circle right around midnight. Just before midnight Alaska Time on May 6, 2014 (0743 UTC, May 7) an RGB NT Micro image derived from the SNPP VIIRS instrument depicted a deck of moderately low marine stratus clouds over the northeastern Bering Sea, as outlined in the black box in Figure 1.
A closer view of this area is shown in Figure 2, along with the ceiling and visibility data from surface observing sites. In this scenario, ceilings, rather than visibility, are the problematic weather element, with the exception of Nome where the imagery shows a localized area of higher conditions. It can be challenging to discern ceilings and visibilities from satellite imagery, and in this respect the RGB NT Micro product has an advantage over conventional satellite imagery. Per the Quick Guide available at http://weather.msfc.nasa.gov/sport/training/rgb_ntmicro/RGB%20Night-time%20Microphysics%20Reference%20Guide%20AK%20by%20SPoRT.pdf and as demonstrated in the Alaskan training module http://weather.msfc.nasa.gov/sport/training/aviationForecasting_Alaska/launcher.html a tan to light green appearance indicates low clouds, but not necessarily fog, in colder climate regions such as Alaska. Surface observations on Saint Lawrence Island and in the Yukon Delta area indicate MVFR ceilings of between one and three thousand feet, but no reduction to visibility due to fog.