Dramatic Soil Moisture Transformation over North Carolina Associated with Flooding Rainfall from Hurricane Florence

Dramatic Soil Moisture Transformation over North Carolina Associated with Flooding Rainfall from Hurricane Florence

As anticipated, Hurricane Florence resulting in monumental rainfall totals, particularly across southern and eastern North Carolina.  This past week’s rainfall totals are depicted in Figure 1, derived from the NOAA/National Weather Service Advanced Hydrologic Prediction Service (AHPS).  Widespread totals exceeded 10” across most of southern/eastern North Carolina and far eastern South Carolina, with maximum rainfall of more than 20” along and within a few counties of the Atlantic Coast.

Fig1_AHPS_11-18Sep_rainfallTotals_countyLabels

Figure 1.  Weekly total rainfall (inches), valid 11-18 September 2018, from the National Weather Service Advanced Hydrologic Prediction Service (AHPS) product.  Four counties are denoted, for which soil moisture histogram animations are shown later in this article.

The extreme rainfall dramatically impacted the soil moisture, which underwent a substantial transformation from very dry to near-saturation across south-eastern North Carolina.  Figure 2 shows soil moisture retrievals before and after Hurricane Florence from NASA’s Soil Moisture Active Passive (SMAP) mission, which estimates near-surface soil moisture (~top 5 cm) in near-real-time derived from passive microwave satellite observations.  A 6-day animation of hourly SPoRT-LIS simulated 0-100 cm relative soil moisture images overlaid with Multi-Radar Multi-Sensor rainfall contours (Fig. 3) nicely shows how the predominantly very dry soils across North and South Carolina prior to Florence were quickly moistened to near saturation over just a few days.  [Ongoing research at SPoRT seeks to further improve the experimental soil moisture estimates by assimilating SMAP retrievals into the SPoRT-LIS framework.]

Fig2_SMAP_Florence_before_and_after

Figure 2.  NASA Soil Moisture Active Passive (SMAP) Level 2 soil moisture retrievals from before (top panel; valid 11 September) and after Hurricane Florence (bottom panel; valid 16 September).

Fig3_rsoim0-100_20180912-17_Florence-NC_anim

Figure 3.  Animation of hourly SPoRT-LIS 0-100 cm relative soil moisture images overlaid with MRMS precipitation contours, valid for the period 0000 UTC 12 Sep to 2300 UTC 17 Sep 2018. [Click on image for full resolution]

Similar to that shown in a companion blog article, Figure 4 shows the evolution of shallow (0-10 cm) to total column/deep (0-200 cm) soil moisture percentiles relative to the SPoRT-LIS 1981-2013 climatological database.  Anomalously dry soil moisture is depicted by orange/red colors, while anomalously wet soil moisture is given by green/blue colors.  Prior to Hurricane Florence, much of South Carolina and southern parts of North Carolina were experiencing unusually dry soil moisture for this time of year.  Despite the capacity for the soils to receive moisture, the historic rainfall was enough to overcome soil moisture deficits, quickly leading to near-saturated soil conditions in all model depths, and ultimately substantial flooding.  An interesting feature to note after the storm impact is the very high soil moisture percentiles greater than 98th percentile across South Carolina in the shallow layers.  Meanwhile, the deeper soils experienced excessive soil moisture percentiles above the 98th percentile predominantly over North Carolina where the heaviest rainfall occurred and where the pre-storm dry anomalies were not as large as in South Carolina.

Fig4a_vsm0-10percent_20180910-17_nc_animFig4b_vsm0-40percent_20180910-17_nc_animFig4c_vsm0-100percent_20180910-17_nc_animFig4d_rsm02percent_20180910-17_nc_animFigure 4.  Daily animations of SPoRT-LIS soil moisture percentiles relative to 1981-2013 climatology, valid from 10 to 17 September over model depths at (top image) 0-10 cm, (2nd image) 0-40 cm, (3rd image) 0-100 cm, and (bottom image) total model column 0-200 cm.  [Click on each individual image for full resolution]

 

Finally, the dramatic transformation in soil moisture is nicely highlighted by examining the present-day, county-averaged values relative to the 1981-2013 climatological distributions, as shown in Figure 5 at four select counties in North Carolina.  Robeson and Cumberland counties (first and third images in Figure 5) experienced the driest soils prior to Hurricane Florence (westernmost counties in Fig. 1), whereas New Hanover and Craven counties (second and fourth images in Figure 5) were more moist prior to Florence’s rainfall.  Each of the four sampled counties ultimately experienced record daily soil moisture values by 17 September (99.9th percentiles).  However, the moist antecedent soils in Craven county led to record soil moisture values by 15 September, whereas the other counties that began with drier soils achieved record values by 16 or 17 September.  In summary, despite predominantly dry soils prior to Hurricane Florence across much of the Carolinas, the tremendous 10-30”+ rainfall totals led to a quick saturation of the soils and massive, widespread flooding.

Fig5a_Robeson_County_NC_7dayloop_ending_20180917Fig5b_New_Hanover_County_NC_7dayloop_ending_20180917Fig5c_Cumberland_County_NC_7dayloop_ending_20180917Fig5d_Craven_County_NC_7dayloop_ending_20180917Figure 5. Daily animations of SPoRT-LIS total column, county-averaged soil moisture histograms, valid from 10-17 September 2018 for (top image) Robeson county, NC [city of Lumberton], (2nd image) New Hanover county, NC [city of Wilmington], (3rd image) Cumberland county, NC [city of Fayetteville], and (bottom image) Craven county, NC [city of New Bern].  Gray bars represent frequency distribution of 1981-2013 climatological 0-200 cm relative soil moisture values, vertical colored lines are reference percentiles, and black dashed line is present-day, county-averaged soil moisture value. [Click on each image for full resolution]

 

Hurricane Florence to Impact the Carolinas with Massive Rainfall

All eyes are on North and South Carolina as Major Hurricane Florence approaches the region over the next two days.  One important component to the official forecast is for the storm to slow down as it approaches the coast, due to the collapse of major atmospheric steering currents.  As a result, the NCEP Weather Prediction Center is predicting extreme rainfall amounts, especially for southeastern coastal North Carolina where 15-20”+ of rainfall is anticipated over the next 7 days (Fig. 1).

Fig1_WPCQPF_HurricaneFlorence_20180912

Figure 1.  NCEP Weather Prediction Center 7-day rainfall forecast, valid for the period 1200 UTC 12 September through 1200 UTC 19 September 2018. [Click image for full view]

An examination of the antecedent soil moisture is helpful to qualitatively assess the ability of the ground to absorb some of the moisture from the incoming rainfall.  Figure 2 shows a collage of shallow to deep soil moisture percentiles from 12 September within the four layers of the Noah land surface model, as being run in real time within NASA SPoRT’s configuration of the Land Information System (i.e., “SPoRT-LIS”).  The percentiles are derived from a 1981-2013 database of SPoRT-LIS daily soil moisture values in order to compare the present-day soil moisture to historical values on any given day of the year.  In Fig. 2, we see that recent soil moisture values are historically quite dry over central/northern South Carolina and into far southern North Carolina, with values under the 10th percentile (and even 2nd percentile, yellow/red shades) in some areas.  Meanwhile, as one traverses inland and northward, the soils steadily moisten to anomalously wet conditions (green/blue shades), especially over interior North/South Carolina to the Appalachian Mountains.

Fig2_SPoRT-LIS-soilMoisturePercentiles

Figure 2.  SPoRT-LIS soil moisture percentiles on 12 September 2018, relative to 1981-2013 daily climatological values for the following layers: (a) 0-10 cm (top model layer), (b) 0-40 cm (top two model layers), (c) 0-100 cm (top three model layers), and (d) 0-200 cm (all four model layers). [Click image for full view]

The dry soil moisture anomalies near the coast suggest that the soils will initially be able to absorb incoming rainfall fairly effectively.  However, as prolonged heavy rainfall continues with the expected slow movement of Hurricane Florence, the soils should quickly become saturated, thereby leading to enhanced runoff and flooding potential over time.  So while having dry soils will be of some help early in the event, a prolonged exceptional rainfall up to 20”+ will lead to substantial flooding regardless of the initial soil moisture distribution.

The blog author documented a similar scenario (also over South Carolina), where substantial moisture from Hurricane Joaquin in Autumn 2015 led to 20”+ rainfall totals, largely occurring over dry soils in an area of moderate to severe drought, thereby completely eliminating the drought classification in South Carolina and producing substantial flooding.  A similar scenario was also seen associated with Hurricane Harvey in southeastern Texas last year, where very dry soils were prevalent prior to Harvey’s landfall north and west of Houston Metro.  However, given the very prolonged exceptional rainfall event, incredible soil moistening and flooding occurred anyway in much of southeastern Texas.

 

Extreme Wildfire Setup over Southern High Plains for 17 April

The fire weather outlook for today (17 April 2018) looks very dire over the Southern High Plains of western Texas, New Mexico, and portions of western Oklahoma, southwestern Kansas, and southeastern Colorado. The combination of very little precipitation in recent months along with expected strong winds and extremely low relative humidities will set the stage for potentially dangerous wildfires over this region. The NCEP Storm Prediction Center has the highest threat category in today’s fire weather outlook across the region, with a large swath of extremely critical fire weather conditions expected (Fig. 1).

The persistent lack of precipitation over the Southern High Plains and Desert Southwest regions and its impact on deep-layer soil moisture is captured by the SPoRT-LIS 6-month change in total column relative soil moisture, as posted on the SPoRT-LIS graphics web page (Fig. 2; https://weather.msfc.nasa.gov/sport/case_studies/lis_CONUS.html).  A sharp transition lies across Kansas, Oklahoma and Texas, where a strong drying signal is seen across western portions of these states into New Mexico, Arizona, and Mexico, whereas dramatic moistening is prevalent in the last 6 months over the Mississippi, Ohio, and Tennessee River Valleys.  Substantial drying is also noted over the southern Florida Peninsula, with wetting seen over the West Coast and Pacific Northwest (Fig. 2).

Since the unusual and persistent dry pattern over the Southern Plains and Desert Southwest has occurred during the winter months when vegetation is typically dormant (which taps into the deeper soil moisture layers), the anomalously dry conditions are best captured by soil moisture percentiles in the near-surface layer of the SPoRT-LIS.  The total column SPoRT-LIS soil moisture percentiles does not depict an overly dramatic anomaly over the Desert Southwest (Fig. 3; unusual dryness is most prevalent in the deep layers from Oklahoma/Kansas up to Wisconsin/Illinois); however, the shallow soil moisture percentiles capture the anomalous drying over these regions near the surface, as seen in the animation of daily 0-10 cm percentiles for April  in Fig. 4, especially over West Texas, New Mexico and Arizona.  Medium-range forecasts suggest there could be precipitation over the Southern High Plains this weekend, but numerous wetting events will be needed to relieve the ongoing drought conditions.

Figure 1. NCEP Storm Prediction Center’s Day-1 fire weather outlook map for 17 April 2018.

Figure 2. Six-month change in SPoRT-LIS total column relative soil moisture for the period ending 16 April 2018.

Figure 3. SPoRT-LIS total column relative soil moisture percentiles, valid for 16 April 2018.

Figure 4. Daily animation of top-layer (0-10 cm) SPoRT-LIS soil moisture percentiles for the period 1 April to 16 April 2018.

Comparison of Soil Moisture Response in Hurricanes Harvey and Irma

Comparison of Soil Moisture Response in Hurricanes Harvey and Irma

After a record [nearly] 12 years between landfalling major hurricanes [cat 3 or higher], the United States has now experienced two major hurricanes making landfall less than three weeks apart from one another.  Hurricane Harvey brought exceptional record rainfall to southeastern Texas and southwestern Louisiana because it stalled shortly after landfall due to a lack of atmospheric steering currents.  Less than 3 weeks later, Major Hurricane Irma made landfall twice in Florida: once in the Lower Keys and again near Marco Island on the southwestern coast.  A long-lived cat 5 hurricane prior to landfall, Irma had a very large wind field which resulted in far-reaching impacts along the Florida East Coast, up to Charleston, SC, and inland to Atlanta, GA, with millions of households and businesses without electricity and/or water.

Here at the NASA SPoRT Center, we have been closely monitoring these two hurricanes through numerous social media and blog posts of unique satellite products and through SPoRT’s real-time instance of the NASA Land Information System (“SPoRT-LIS”).  This blog post serves to compare the soil moisture responses to hurricanes Irma and Harvey rainfall, as depicted by the real-time SPoRT-LIS output.  The Relative Soil Moisture (RSM) variable is shown throughout this article, since it takes into account the variations in soil composition by scaling the moisture availability between the wilting point (plants cannot uptake moisture) and saturation point (soil cannot hold any more water).  The SPoRT-LIS runs the Noah land surface model, which estimates soil moisture through 4 layers: 0-10, 10-40, 40-100, and 100-200 cm depth.  We first examine the response during Irma in the top 0-10 cm layer, followed by 0-100 cm layer for both storms, and then compare the total column (0-200 cm) values relative to historical values from a climatological database spanning 1981-2013 (33 years).

Figure 1 compares the weekly rainfall accumulation primarily from Hurricane Irma over the Southeastern U.S. to the August monthly rainfall total over Texas/Louisiana, primarily contributed from Hurricane Harvey during the final week of August. Rainfall from Irma was quite substantial in the Florida peninsula up to coastal South Carolina, where numerous locations measured over 10″ of rain in less than 2 days. Rainfall of 3-5″ extended inland to northern Georgia and central South Carolina, with lesser amounts generally below 3″ across eastern and northern Alabama (Fig 1, left panel).  The highest totals were along the southwestern and eastern Florida coasts.  This rainfall still pales in comparison to the widespread 20″+ that fell across a huge part of southeastern Texas and western Louisiana, albeit over a 5-6 day span.  Highest totals exceeded 50″ near Beaumont/Port Arthur, TX!

PrecipComparison

Fig 1.  Comparison of weekly rainfall estimate associated with Hurricane Irma (left), and August monthly rainfall estimate associated with Hurricane Harvey (right).

The 0-10 cm RSM animation in Fig 2 for hurricane Irma shows how quickly the top soil layer responds to incoming rainfall within the Noah land surface model in SPoRT-LIS.  The heavy rainfall rates up to 4″ per hour or more led to a quick saturation during 10 September across the Florida peninsula, eventually extending up to coastal Georgia and South Carolina on the 11th.  Similarly, as rainfall ends we can see the 0-10 cm RSM quickly decrease from south to north as the moisture infiltrates into deeper model layers and/or evaporates back to the atmosphere.  We also see that the top soil layer does not completely saturate across interior Georgia and Alabama, likely due to lower rain rates, drier initial soils, and different soil composition compared to the fast-responding sandy soils across Florida.

rsoim0-10_hurricaneIrma_10-12Sep_anim

Fig 2.  Hourly animation of SPoRT-LIS 0-10 cm relative soil moisture (RSM) and Multi Radar Multi Sensor (MRMS) quantitative precipitation estimates (QPE) from 0000 UTC 10 September through 1200 UTC 12 September 2017, associated with Hurricane Irma.

Meanwhile, the RSM averaged over the top 3 layers (0-100 cm; Fig 3) takes a longer time to moisten up during the heavy rainfall of Irma. We do see values approaching saturation across southwestern, central, and particularly northeastern Florida near the end of the rainfall event as the deeper soils have had an opportunity to recharge.

Over southeastern Texas and Louisiana (Fig 4), the 0-100 cm RSM animation shows how the prolonged, training heavy rainfall led to near saturation of the top meter of the Noah model, despite dry antecedent conditions (especially west of the Houston metro, where the RSM transitioned from less than 10% to nearly saturation!).  The much longer rainfall duration with hurricane Harvey led to sustained higher values of soil moisture in the top one meter.

rsoim0-100_hurricaneIrma_10-12Sep_anim

Fig 3.  Hourly animation of SPoRT-LIS 0-100 cm RSM and MRMS QPE from 10-12 September 2017, associated with Hurricane Irma.

rsoim0-100_hurricaneHarvey_25-30aug_anim

Fig 4.  Hourly animation of SPoRT-LIS 0-100 cm RSM and MRMS QPE from 25-30 August 2017, associated with Hurricane Harvey.

Finally, the total column 0-200 cm layer can require months or years to respond to rainfall events (or lack thereof), depending on the soil composition.  However, with major rainfall events like hurricanes Harvey and Irma, the total column RSM does respond dramatically and subsequently can depict substantial wet anomalies.  To that end, the SPoRT-LIS has a daily, county-based climatological database of modeled soil moisture from 1981-2013 from which current conditions can be compared to depict anomalies via percentiles relative to the 33-year distribution.  Fig 5 shows these percentiles color-coded to depict dry anomalies (less then 30th percentile) or wet anomalies (greater than 70th percentile) according to the scales beneath the figure.

Following hurricane Irma, we see that portions of southwestern and northeastern Florida have 0-200 cm RSM greater than the 98th percentile, as well as parts of west-central Georgia (Fig 5; left panel).  In general, the extreme wet percentiles are fairly spotty across the domain.  However, following hurricane Harvey (Fig 5; right panel), the 0-200 cm RSM percentiles are “off the charts” high, with dozens of counties experiencing soil moisture exceeding the [33-year] historical 98th percentile.  In fact, the soil moisture was SO anomalously moist following hurricane Harvey that the average daily value across all of Jefferson County, TX (Beaumont/Port Arthur) exceeded all values in the entire 33-year database by the end of August!  This unusual condition is highlighted in Fig 6, which shows a daily animation of historical 0-200 cm RSM histograms for Jefferson County, TX, with the current 2017 county-averaged values in the vertical dashed line.  We see that by the end of hurricane Harvey, the vertical dashed line is well above any values from the 33-year historical distribution, thereby quantifying how exceptionally unusual this rainfall event was in southeastern Texas.

PercentileComparison

Fig 5.  SPoRT-LIS 0-200 cm RSM percentile, valid at 1200 UTC on 12 September 2017 (post-Irma; left), and 30 August 2017 (post-Harvey; right).

Jefferson_County_TX_30day_realtimeLoop

Fig 6. Animation of daily distributions of 0-200 cm RSM for all SPoRT-LIS grid points residing in Jefferson County, TX (Beaumont/Port Arthur) during the month of August 2017.  Gray bars are the frequencies of 0-200 cm RSM from the 33-year SPoRT-LIS climatology; colored vertical lines are reference percentiles according to the legend in the upper right; and the bold vertical dashed line is the county-averaged value for the present day in August 2017.

Soil Moisture Conditions over Southeast Texas Prior to Hurricane Harvey

Soil Moisture Conditions over Southeast Texas Prior to Hurricane Harvey

As much-anticipated Hurricane Harvey approaches the southern and eastern coast of Texas today, it is worth examining the pre-existing soil moisture over the region to understand the capacity of the land surface to absorb the upcoming rainfall.  Granted, the amount of rainfall simulated by numerical guidance is off-the-charts high (e.g., today’s 0600 UTC initialized NAM model [Fig. 1] shows 84-hour maximum accumulated rainfall of over 60″ between Corpus Christie and Houston!!).  Thus, extreme flooding is anticipated, regardless of the amount that can be absorbed by the soils.

Fig1_NAMFLT_prec_precacc_084

Figure 1.  The NCEP/NAM model 84-hour forecast of total accumulated precipitation (inches) over Southeastern Texas, from the simulation initialized at 0600 UTC 25 August 2017 [image courtesy of College of DuPage forecast page].

SPoRT manages a real-time simulation of the NASA Land Information System (hereafter, “SPoRT-LIS“), running over the Continental U.S. at ~3-km grid resolution.  The SPoRT-LIS product is a Noah land surface model climatological and real-time simulation over 4 model soil layers (0-10, 10-40, 40-100, and 100-200 cm).  The climatological simulation spans 1981-2013 and forms the basis for daily-updated total-column soil moisture percentiles (forthcoming in Fig. 3), in order to place current soil moisture values into historical context.  For real-time output, the Noah simulation is regularly updated four times per day as an extension of the long-term climatology simulation.  It includes NOAA/NESDIS daily global VIIRS Green Vegetation Fraction data, and the real-time SPoRT-LIS component also incorporates quantitative precipitation estimates (QPE) from the Multi-Radar Multi-Sensor (MRMS) gauge-corrected radar product.  The climatological SPoRT-LIS is based exclusively on atmospheric analysis input from the NOAA/NASA North American Land Data Assimilation System – version 2.

Relative Soil Moisture output from the SPoRT-LIS over the 0-100 cm layer is shown in Fig. 2 over Southeastern Texas and Louisiana at 1200 UTC this morning.  A marked gradient between very dry soils to the west and moist soils to the east occurs in the vicinity of the greater Houston metropolitan area.  The soils in the region bounded by Corpus Christi, San Antonio, Austin, and Houston (areas forecast to have the greatest rainfall from Hurricane Harvey) are extremely dry prior to Harvey’s landfall.  This dryness will help to some extent in absorbing the initial rainfall from Hurricane Harvey.  But with such excessive rainfall being forecast over a prolonged time period (3-5+ days), it won’t be long before the upper portions of the soil column saturates and widespread areal flooding occurs.  In addition, the high forecast rainfall rates could easily result in flash flooding (despite prevailing soil dryness), especially further inland where terrain plays a more important role in runoff and flash flooding.

The total column relative soil moisture percentile from 24 August shows that historically-speaking, the soil moisture is slightly drier than normal, particularly along the coastal plain between Corpus Christi and Houston (Fig. 3).  In this corridor, the soil moisture is generally between the 10th and 30th percentile compared to the 1981-2013 climatological distribution for 24 August.

Fig2_rsoim0-100_20170825_12z_tx_cityLabels

Figure 2.  SPoRT-LIS relative soil moisture (RSM) distribution in the 0-1 meter layer across Southeastern Texas and Louisiana, valid 1200 UTC 25 August 2017.  RSM values of 0% represent wilting (vegetation cannot extract moisture from soil) and 100% represents saturation (subsequent rainfall becomes runoff).

Fig3_rsm02percent_20170824_12z_tx

Figure 3.  Total column (0-2 m) relative soil moisture percentile valid 24 Aug 2017, as compared to all 24 August soil moisture values from a 33-year climatological simulation of the SPoRT-LIS.

Finally, an hourly animation of the 1-day changes in 0-10 cm (top model layer) relative soil moisture show that the near-surface soils are quickly moistening between Corpus Christi and Houston, as the initial rainbands of Hurricane Harvey began impacting the coastal plain this morning.  As the soils continue to moisten rapidly from the top-down, subsequent rainfall will quickly lead to runoff and flooding.

Fig4_rsoim0-10diff1_20170825_anim

Figure 4.  Hourly animation of 1-day change in top-layer (0-10 cm) relative soil moisture, for the time period spanning 0000-1400 UTC 25 August 2017.  Each hourly image is a simple difference in 0-10 cm relative soil moisture between the current and previous day at the same valid hour.  Line contours depict one-hour QPE from the MRMS product, as input to the real-time SPoRT-LIS.

Detecting tornado tracks using Synthetic Aperture Radar (SAR) imagery

NASA SPoRT has been working to support the NWS’s use of the Damage Assessment Toolkit (DAT) by integrating multiple satellite datasets into the DAT framework to assist in damage surveys.  Imagery from MODIS, VIIRS, and Landsat 8 are available daily within the application while imagery from higher resolution satellites, such as Terra ASTER and other high-resolution commercial imagery are facilitated by our partnership with the USGS’s Hazard Data Distribution System (HDDSexplorer.usgs.gov). One new area being explored is the application of Synthetic Aperture Radar (SAR) imagery to detect tornado damage.

ClearkLake_WI_SAR_Tornado.gif

Zoomed-in section of the SAR change detection RGB generated from Sentinel-1B imagery from May 10 and May 22, 2017.  The damage indicators show preliminary track information as of June 2, 2017 and are not considered final.

On the evening of May 16th, 2017, a supercell tracked across Wisconsin producing a strong tornado. The resulting 83-mile long track tornado produced EF-3 damage.  Shown in the image above is a prototype change detection RGB using data from Sentinel-1(A/B), a European Space Agency (ESA) satellite with a SAR instrument on board. Unlike optical sensors, which observe surface reflectance and temperature, SAR instruments measure backscatter from the surface, allowing the instrument to be used at all times of the day and in any sky conditions. SPoRT has been working with the Alaska Satellite Facility, NASA’s SAR Distributed Active Archive Center (DAAC) to receive these products for evaluation and put them in the DAT to help with the identifying of damage tracks, especially in areas where damage surveys can be more challenging (i.e. forested areas, poor road network).  The RGB takes advantage of the dual polarization from the sensor, assigning the VV and VH corrected polarization from the post-event granule to the red and green channels of the RGB, respectively.  The blue channel is a difference image of the VH polarization (same as what is used in the green channel) from the before and after granules.  The resulting RGB will show any changes between the two granules in a aqua/periwinkle/purple-color.  Although the RGB will show all change between the granules over the ~12-day period (i.e. agricultural growth), tornado tracks tend to be linear, making it a possible to discern/identify the damage track.  Without the hindrance of clouds that constantly plague damage detection in optical imagery, SAR imagery offers another tool to operational forecasters for use during damage surveys.  The team is also working on other change or anomaly detection techniques to facilitate mapping of tornado and severe weather damage.

Stark contrast in Eastern U.S. soil moisture following Hurricane Matthew

Stark contrast in Eastern U.S. soil moisture following Hurricane Matthew

Major Hurricane Matthew left a trail of destruction in its wake from the Caribbean up through the U.S. East Coast.  As Hurricane Matthew tracked northward along a large portion of the U.S. Southeast Coast from Florida to North Carolina, the rainfall impacts worsened.  Figure 1 shows the weekly rainfall spanning 4-11 October, ranging from ~2-8 inches along the Florida East Coast to 10-20 inches in the eastern Carolinas.  Since antecedent soil moisture was highest in the eastern Carolinas (Fig. 2), the extreme rainfall led to the most serious flooding in this area.

fig1

Fig. 1.  Weekly rainfall totals from 4 – 11 October 2016.

fig2

Fig. 2.  Total Column (0-2 m) relative soil moisture prior to Hurricane Matthew’s impact on North and South Carolina, valid at 0000 UTC 7 October 2016.

Referring back to the precipitation totals in Fig. 1, we can see that there was a sharp rainfall gradient on the northwestern edge in the Middle Atlantic region.  Interestingly, this gradient in Hurricane Matthew’s rainfall coincided with a pre-existing transition zone between wet conditions near the Atlantic coast and drought conditions further inland from the Appalachians through New England.  The net result was to accentuate the wet-dry contrast already in place.  The animation in Fig. 3 highlights this contrast nicely by presenting the SPoRT-LIS daily total-column relative soil moisture percentiles from 1-12 October.  The percentiles are based off a 1981-2013 daily soil moisture climatology that SPoRT produced from its ~3-km resolution SPoRT-LIS simulation.  By 9 October, notice the incredible transition from excessively wet soil moisture exceeding the 98th percentile (Carolinas through the southern half of Delaware) to extremely dry soil moisture less than the 5th percentile across Pennsylvania into the Northeast (as well as much of the inland Southeastern U.S.).  In fact, total column soil moisture values are less than the 2nd percentile over a large part of Ohio, Pennsylvania, New York, and the New England states, indicative of the ongoing severe drought there.

fig3_loop

Fig. 3. Daily animation of SPoRT-LIS total column relative soil moisture percentile from 1 to 12 October 2016.