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!
Expanding D0 in Central NC Utilizing 0-200cm RSoM in Conjunction with 30-90 Day Precip Deficits
The North Carolina Drought Management and Advisory Council (NCDMAC) has a teleconference each Tuesday afternoon to discuss drought conditions and submit recommended changes to the U.S. Drought Monitor (http://drought.gov/drought). A variety of data are considered, such as streamflows, reservoir and monitored well levels, and agricultural reports. Relative soil moisture fields from NASA’s Short-term Prediction Research and Transition Center (NASA/SPoRT- http://weather.msfc.nasa.gov/sport), are newer datasets which have been introduced and evaluated over the past few months.
A Case from 10/28/2014
Below are 30, 60, and 90 day rainfall deficits, as well as the 0-200 cm relative soil moisture (RSoM) product from NASA/SPoRT. The circled area in each image corresponds to the area designated as ‘abnormally dry’ (D0) for the previous week. The RSoM (using a rather subjective 25% threshold) shows very strong correlation to rainfall deficits in the longer time frames (60 and 90 days), which are the fields typically used to help delineate low base flow in areas where reliable streamflow data is more sparse. The high resolution of the RSoM (which is more evident than can be seen in the downsized image), allows for sub-basin and sub-county scale delineation of areas of concern.
Southerly expansion of D0 conditions were recommended (below), with the RSoM’s weighing heavily on the decision to do so. The U.S. Drought Monitor author for the week, Brian Fuchs, was on the call and requested information concerning the NASA/SPoRT product suite. He was provided LIS links and information.
NASA SPoRT has developed a real-time application of the NASA Land Information System (LIS) that runs over much of the central and eastern United States. The LIS produces several products, including a suite of soil moisture products that can be used to help assess drought and flooding potential. There are four LIS soil moisture products that are made available to WFO Raleigh forecasters in AWIPS-2 and which are available online for the Southeast and for North Carolina.
A fairly significant rain event occurred across central North Carolina on 15 and 16 October 2014 as a cold front and a wave of low pressure moved across the region. Two day precipitation totals across the WFO RAH CWA (Fig. 1) indicated between 0.75 and 1.25 inches of rain fell across the western Piedmont with much more significant amounts generally ranging between 1.5 and 3.0 inches across the eastern Piedmont and Coastal Plain of North Carolina. The heaviest rain occurred across Franklin, eastern Wake, northern Johnston, and western Nash Counties.
One of the SPoRT-LIS fields that forecasters have found quite useful during the assessment is the one-week change in total column relative soil moisture (RSM, 0-2 m). The RSM is the ratio of the current volumetric soil moisture between the wilting and saturation points for a given soil type, with values scaling between 0% (wilting) and 100% (saturation). The one-week change product valid at 12 UTC on 14 October, just prior to the rain event, is shown in Fig. 2 with the RAH CWA outlined in red. This product indicates that much of the southern and eastern portions of the RAH CWA have experienced a relative soil moisture decrease during the previous week, while locations near the Virginia border, especially across the northern Piedmont have had a relative soil moisture increase.
This rainfall produced significant rises on many rivers and creeks across the northeast Piedmont and the Coastal Plain of North Carolina. Figure 3 shows the gage height on the Swift Creek at Hilliardston which had an uncharacteristic rapid response and the gage height on the Neuse River at Smithfield which exceeded flood stage.
It was noted that the locations that experienced the most significant rises along with some flooding where in the river basins that had a notable overlap of the one-week increase in total column relative soil moisture prior to the event and the basins which experienced the most significant rainfall as shown in the composite image in Fig. 4.
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.
So, with the moon now passing into the waning crescent phase, the Day-Night Band imagery is less operationally useful, at least for the detection of fog and other lower level cloud types. That is, at least until the moon is back into the waxing gibbous phase. Nevertheless, when cirrus clouds aren’t present, the Nighttime Microphysics RGB has proven to be a very valuable tool for the detection of fog and other low-level clouds. Just this morning a forecaster at the Huntsville, AL WFO was able to use the imagery not only for the detection of fog, but also to aid in the issuance of a special weather statement about the fog. The image below valid at ~724 UTC (0224 am CDT) 17 Oct shows the fog (whitish-aqua colors) lying across the valley areas of NE Alabama and adjacent areas of southern Tennessee and NW Georgia.
Around the time of this image, the visibility in the foggy locations had decreased to ~1/4 – 1/2 SM or less. Notice the fog in the DeKalb Valley is fainter than the fog in areas to the north and west. Not only is the DeKalb Valley more narrow, but the fog was likely more shallow. This feature of the imagery can also help to guide forecasters in assessing the longevity of the fog once sunrise breaks. Over time, forecasters can develop a sense of pattern recognition with the varying degrees of color shading and tailor forecasts to better match the time of dissipation. In this case, the fog in the DeKalb Valley began to dissipate significantly by about 1430 UTC, while the deeper and more expansive fog to the north and west lasted about an hour longer.