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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 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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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 0900 UTC Nov 25, 2013

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

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

Image 3. SPoRT LIS Column-Integrated (0-200 cm) Relative Soil Moisture 0600 UTC Nov 28, 2013

 

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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 1.  Topography in Eastern Mexico leading to strong gap winds in the Gulf of Tehuantepec.

Figure 1. Topography in Eastern Mexico leading to strong gap winds in the Gulf of Tehuantepec.
Image credit: http://www.wunderground.com/blog/24hourprof/tehuantepecer.

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 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.  WindSat image of wind vector valid 1200 UTC 12 November 2013, courtesy of the Naval Research Laboratory.

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.

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.

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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The latest version of the Advanced Research WRF (WRF EMS v3.4.1) is up and running at NWS Huntsville.  While we still have some adjustments to make, which primarily involve getting ALL of the desired forecast parameters into AWIPS II…the data are mostly available (example shown in image 1).  One of the primary advantages of outputting data to AWIPS II is the ability to overlay multiple fiorecast parameters (image 1), and to include other data sets such as regional METARs.  This can provide forecasters with the ability to make quick qualitative and quantative analysis of the model’s performance with real-time data sets.

Image 1.  HUN local WRF EMS nested 3km domain displayed in AWIPS II.  Shown are surface dewpoints (F, image), surface wind streamlines (knots, white lines), mean sea-level pressure (mb, yellow lines), and METAR plots valid 1500 UTC 14 Aug 2013.  This is the 3 hour forecast data from the 1200 UTC "SPoRT" model run.

Image 1. WFO HUN local WRF EMS nested 3km domain displayed in AWIPS II. Shown are surface dewpoints (F, color image), surface wind streamlines (knots, white lines), mean sea-level pressure (mb, yellow lines), and METAR plots valid at 1500 UTC 14 Aug 2013. Note that these are 3 hour forecast data from the 1200 UTC “SPoRT” model run.

Our office IT has created a new data viewer as well, which has some great features: capable of displaying data/imagery from archived model runs, can automatically generate animated .gifs, allows switching between the SPoRT and control models for quick, qualitative analysis between the two model runs.

Image 2.  New HUN WRF EMS Viewer. Data shown are 3km inner domain 3-hour forecast 2 m temperatures valid 1500 UTC 14 August 2013.

Image 2. New HUN WRF EMS Viewer. Data shown are 2m temperatures valid 1500 UTC 14 August 2013, from the 3km nested 1200 UTC SPoRT model run.

The HUN office is involved in a collaborative effort with SPoRT, configuring our local model to use MODIS-derived data (GVF, SSTs,) and the SPoRT Land Information System (land surface model) in our operational run.  A control model is also being run on the same system, using standard NAM and other climatological data sets in place of the SPoRT related data sets.  SPoRT is providing an updated version of the Meteorological Evaluation Tools (MET) which will make objective, quantitative analysis and verification of the model runs possible.  It is expected that the more representative, higher resolution SPoRT related data sets will translate to better overall accuracy of forecast parameters in the SPoRT model run vs those of the control run when compared with real-world in-situ observations.  We will be running the MET for specific events and perhaps to determine and compare longer term biases between the two model runs over the remaining summer and the upcoming fall/winter.

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