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A cold front will sag slowly southward across the mid-South and Mid-Atlantic during the upcoming weekend, and will likely stall over the Carolina Piedmont region as a couple of waves of low pressure move along the front. The broad scale lift of the moisture-laden airmass ahead of and over the shallow front will be capable of producing moderate to heavy rainfall in the Carolinas through early next week. Recently, the Raleigh NWS forecast area experienced heavy rainfall (see recent blog post from the Raleigh NWS office) which lead to the moistening of soils and some instances of flooding. If the heavy rains in the latest forecast by the Weather Prediction Center (WPC) materialize, then current soil moisture levels suggest the risk for flooding will be increased. Take a look at the SPoRT LIS 0-200 cm Relative Soil Moisture (%) analysis below from 12Z this morning (Image 1).

Figure 1.  SPoRT LIS 0-200 cm Relative Soil Moisture (%, RSOIM), valid 12Z 11 Sep 2014.  An area with RSOIM values around 50-60% is circled in black centered on the eastern part of the Raleigh forecast area.

Image 1. SPoRT LIS 0-200 cm Relative Soil Moisture (%, RSOIM), valid 12Z 11 Sep 2014. An area with RSOIM values around 50-60% is circled in black centered on the eastern part of the Raleigh forecast area.

The area circled in black indicates portions of the Raleigh NWS forecast area where 0-200 cm Relative Soil Moisture (RSOIM) values exceed 55%. Here in the Huntsville area, subjective analysis of several synoptic rainfall events suggests that when 0-200 cm RSOIM values exceed this threshold, the risk of flooding of basins and rivers in our area is increased substantially. Next, let’s take a look at the latest 5-day precipitation graphic produced by the Weather Prediction Center (WPC, Image 2).

Image 2.  WPC (HPC in label) 5-Day Total Precipitation ending 12Z 16 Sep 2014.

Image 2. WPC (HPC in label) 5-Day Total Precipitation ending 12Z 16 Sep 2014. The region with relatively moisture 0-200 cm soils is circled in black.

In this latest update from the WPC, precipitation amounts totaling around two to four inches are forecast for portions of the Raleigh NWS forecast area. Of course, these totals are likely to be adjusted over the days ahead. Additionally, some of the precipitation during this period is likely to be convective in nature, which will make the resulting precipitation in the region more heterogeneous, and it may fall in several distinct episodes, reducing the overall average rainfall rate. Nevertheless, since soil moisture levels have now exceeded a seemingly critical threshold, this particular area may bear watching for potential flooding if the rains materialize.

The Raleigh WFO together with the Huntsville and Houston WFOs are participating currently in a more formal assessment of several SPoRT LIS variables. Although this and other soil moisture variables have demonstrated utility for assessing both drought and flood risk in the Huntsville forecast area over the last few years, this is the first formal assessment to evaluate the utility in different environments simultaneously.

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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.  WFO Raleigh is currently evaluating these soil moisture products.

A significant rain event occurred across central and eastern North Carolina on 08 and 09 September 2014 as surface low moved northeast along a stalled cold front that was located in the Coastal Plain of the Carolinas. Radar estimates which match fairly well with surface observations indicated a large area of 2 to 4 inches of rain fell across eastern NC with several locations receiving between 6 and 8 inches of rain (Fig. 1).

Fig. 1. The 48 hour precipitation estimate for North Carolina for the period ending at 12 UTC on 9 September 2014.

Fig. 1. The 48 hour precipitation estimate for North Carolina for the period ending at 12 UTC on 9 September 2014.

This heavy rain resulted in a significant increase in the 0 to 10cm below ground Relative Soil Moisture (RSM) as noted in the animation of RSM from 12 UTC on 7 September through 00 UTC on 09 September, 2014 shown below (Fig. 2). The 0 to 10cm RSM product provides the ratio of the water content per total soil volume between the wilting and saturation points for a given soil type, expressed as a percentage. The RSM product provides information about the soil saturation state. Since this RSM product highlights the moisture in a very shallow layer between the surface and about 4 inches below ground, the values change quickly as the heavy rain begins and diminishes.

Fig. 2. An animation of the LIS 0 to 10cm below ground Relative Soil Moisture product from 12 UTC on 7 September through 00 UTC on 09 September, 2014.

Fig. 2. An animation of the LIS 0 to 10cm below ground Relative Soil Moisture product from 12 UTC on 7 September through 00 UTC on 09 September, 2014.

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The previous blog post made by the NWS forecast office at Raleigh, NC (WFO RAH) illustrated the decrease in LIS total column relative soil moisture over North Carolina (NC) associated with the recent lack of rainfall through 1 September.  Despite receiving some nominal precipitation up to 0.50″ during the previous week, portions of eastern NC experienced the greatest amount of soil drying compared to central NC where practically no rain fell.

This response in the Noah land surface model within the real-time SPoRT-LIS is related to the disparate soil composition across NC as seen in Figure 1.  The soils consist of mostly sand or sandy loam composition across eastern NC compared to silty loam in central NC.  The movement of water in lower porosity, sandy soils is dominated by capillary action (upward movement of water against gravity) and thus readily release its water at higher soil moisture values.  Meanwhile, higher porosity soils (i.e., clay/silt with numerous smaller pores) retain water for longer time periods and tend to dry out more slowly at higher values of soil moisture (google “water retention curve” for more details).  Thus, despite the modest rainfall over the sandy soils of eastern NC, the soil actually dried out faster than over central NC where less rainfall was observed.

soilType_nc

Figure 1. Soil texture classifications used in the SPoRT-LIS runs of the Noah land surface model, centered over North Carolina.

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NASA SPoRT has developed a real-time configuration of the NASA Land Information System (LIS) that runs over much of the central and eastern United States at 3-km grid spacing.  The LIS produces several products, including a suite of soil moisture products that can be used to help assess drought and flooding potential.  WFO Raleigh is pleased to be participating (along with WFOs Houston and Huntsville) in an assessment of these products from August through October.

Central North Carolina has been in a short-term relative dry spell of late, with much of the area having seen little to no rainfall in the last week (Fig. 1). One ramification of this lack of rainfall is the soil drying evident in the 1-week difference in column relative soil moisture imagery (Fig. 2), which shows marked drying over all of Central NC in the last week. Interestingly, in coastal sections of NC that actually have seen some rainfall in the last week, the soil drying has been even more pronounced. Reasons for this are unclear, but it may have to do with the soil type over Eastern NC.

7dayrainfall.ending12z20140901

Fig. 1. Seven-day rainfall over North Carolina, for the period ending at 8 am EDT 1 September 2014.

1weekdiffinsoilmstr.ending00z20140901

Fig. 2. One-week difference in column relative soil moisture (%) over North Carolina, for the period ending at 8 pm EDT 31 August 2014.

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NASA SPoRT has developed a real-time configuration of the NASA Land Information System (LIS) that runs over much of the central and eastern United States at 3-km grid spacing.  The LIS produces several products including a suite of soil moisture products that can be used as a tool for assessing drought and flooding potential.  WFO Raleigh along with WFOs Houston and Huntsville are participating in an assessment of these products during August and September. SPoRT created a couple of training modules (LIS Primer module and LIS Applications Module) to prepare NWS forecasters for this new dataset.

There are four LIS soil moisture products that are made available to WFO Raleigh forecasters in AWIPS-2 and which are available online at http://weather.msfc.nasa.gov/sport/case_studies/lis_SEUS.html for the Southeast and http://weather.msfc.nasa.gov/sport/case_studies/lis_NC.html for North Carolina.  The products include:

  1. Volumetric Soil Moisture (0 to 10cm) [SOIM0-10]
  2. Below Ground Relative Soil Moisture (0 to 10cm) [RSOIM]
  3. Below Ground Relative Soil Moisture (0 to 200cm) [INT-RSOIM]
  4. Below Ground One Week Change in Column Relative Soil Moisture (0 to 200cm) [RSOIMDIFF]

Each week, WFO Raleigh Hydrologist Michael Moneypenny serves as a member of the North Carolina Drought Management Advisory Council (NCDMAC) which provides recommendations to the U.S. Drought Monitor (USDM).  The USDM consists of a consortium of academic and government partners, including the University of Nebraska-Lincoln National Drought Mitigation Center (NDMC) and various other federal and state agencies.

WFO Raleigh started receiving the LIS soil moisture products in July and evaluating the products in August. The products were first used during the weekly NCDMAC collaboration call on Tuesday August 5th.  The LIS data was used to expand the D0 (abnormally dry) category at a sub-county level into portions of Robeson and Scotland Counties. In particular, the 0-200 cm Relative Soil Moisture Weekly Change product was used to show changes in the deep layer soil moisture. In figure 1 below, the upper image was referenced by the NCDMAC during the August 5th collaboration call to recommend expansion of D0 at the sub-county scale in the area circled.

In addition, a more formal demonstration of the full suite of LIS soil moisture products was conducted during the weekly NCDMAC collaboration call on Tuesday August 12th. In figure 1 below, the lower image was used to inspect the short time scale improvement of soil moisture conditions in the areas under D0 drought designation. While the graphic shows marked improvement from significant rainfall, the D0 areas were not modified as lingering 30 and 60 day rainfall deficits in these areas (in addition to crop reports), overshadowed the short term improvement.

The NCDMAC will be examining how best to utilize these products for drought assessment. Preliminary ideas include: 1) how the products can be correlated to the observed well level observations available via the USGS and state networks, and 2) how the SPoRT products can be used to enhance or complement the Standardized Precipitation Index product produced by the NC State Climate office.

Figure 1. The 0-200 cm Relative Soil Moisture Weekly Change products ending at 08/05/2014(top) and 08/12/2014(bottom) are shown above. The U.S. Drought Monitor status is shown in the insert in the lower left with the area of abnormally dry conditions (D0) shown in the yellow shading.

Figure 1. The 0-200 cm Relative Soil Moisture Weekly Change products ending at 08/05/2014(top) and 08/12/2014(bottom) are shown above. The U.S. Drought Monitor status is shown in the insert in the lower left with the area of abnormally dry conditions (D0) shown in the yellow shading.

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Since the advent of the AWIPS II era, LIS data have been absent in AWIPS, beginning spring 2012 here at NWS Huntsville.  Forecasters at the Huntsville WFO had become somewhat accustomed to looking at the data/imagery online through the SPoRT website (http://weather.msfc.nasa.gov/sport/), which is still a great resource for data and information.  However, this limited the full functionality of the LIS data, especially when considering the lack of ability to overly with other data and make efficient forecast assessments.  The LIS data have been used at NWS Huntsville in the past to assess everything from flooding probability, to drought development, and to the potential for freezing precipitation accumulation.  Thanks to the hard work of the SPoRT team however, we now have LIS data flowing again in AWIPS II!  These data have become very useful operationally here at NWS Hun, and I’m going to be sharing a number of operational examples here on the blog in the days and weeks to come, in addition to some examples in my presentation at the upcoming SPoRT 2014 Virtual Workshop on Thurs, Feb 13th.

First, here is a sample of the SpoRT LIS depiction of shallow layer (0-10 cm) relative soil moisture (%) from the other day, Jan 27, 2014…

Image 1.  SPoRT LIS 0-10 cm Relative Soil Moisture (%), 27 Jan 2014

Image 1. SPoRT LIS 0-10 cm Relative Soil Moisture (%), 1200 UTC 27 Jan 2014

And, here is a sample of the Skin Temperature product from the same date/time…

SPoRT LIS Skin Temperature (C), 1800 UTC 27 Jan 2014

SPoRT LIS Skin Temperature (C), 1200 UTC 27 Jan 2014

Now, take a look at the LIS skin temperature the next day after a modified arctic airmass had moved into the deep South, and when a relatively rare winter precipitation event was unfolding across parts of the region.

Image 3.  SPoRT LIS Skin Temperature product 1200 UTC 28 Jan 2014

Image 3. SPoRT LIS Skin Temperature (C) 1800 UTC 28 Jan 2014.  Color shadings from dark blue to white indicate areas where surface skin temperatures are <0C.

As stated above, with the data in AWIPS II, the ability to overlay other data/imagery can be very beneficial for operational forecasters.  Below, is an image of the Skin Temperature product overlaid with a regional WSR-88D radar composite (0.5 reflectivity), along with surface METAR observations.

Image 4.  SPoRT LIS Skin Temperature overlaid with the regional WSR-88D radar composite and surface METAR observations, valid 1800 UTC 28 Jan 2014

Image 4. SPoRT LIS Skin Temperature overlaid with the regional WSR-88D radar composite (30% transparency-adjusted, 0.5 reflectivity) and surface METAR observations, valid 1800 UTC 28 Jan 2014

Together with other imagery and data, the value of this product, particularly when combined with other data, can be extraordinarily beneficial for operational forecasters.  Forecasters have the ability to sample the data in AWIPS II, with direct readout of Skin Temperatures in degrees Celsius as they mouse-over a location.  Combining the radar data with the skin temperature can provide further evidence and a more efficient assessment of locations where precipitation is likely occurring over a frozen surface.

Of course, there are numerous potential applications of these and other LIS data, and as stated earlier, I’ll be addressing more of those in future posts.  By the way, we are currently finalizing a LIS training module, and will have instructions for the ingest and display of these data in AWIPS II available soon.

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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.

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.

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.

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.

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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