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So, recently I’ve had the opportunity to use and evaluate soundings from the NOAA Unique Combined Atmospheric Processing System (NUCAPS).  These soundings, produced by the ATMS and CrIS instruments onboard the Suomi NPP satellite, are available in AWIPS generally twice per day over any given location.

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Image 1.  NUCAPS Sounding data availability example, ~19 UTC 24 July 2016. Colors represent quality control flags — green are considered best available and most representative data.

A couple of advantages of the NUCAPS soundings is they’re available in relatively high spatial resolution (image 1) and also in between radiosonde launches.  So, a forecaster wanting to know more about tropospheric conditions during the midday or early afternoon (usually the most crucial period for severe weather analysis) can utilize NUCAPS sounding data, since radiosonde data won’t be available until later in the evening (unless ~18 UTC launches are being conducted at their location).  On a number of days in recent weeks, a lack of sufficient boundary layer moisture (probably partly due to an ongoing drought in the region) have dampened convective development.  A good understanding of the degree of convective inhibition (CIN) present on a given day can be difficult to obtain and model analyses and forecasts don’t always seem to have a good handle on this.  Even other robust analyses often struggle with a seemingly accurate depiction of CIN on many days.  However, knowledge of CIN, among other factors, can be important when forecasting probabilities for convective development on summer days.

Recently however, I’ve noticed that NUCAPS soundings did indicate the presence of CIN when convective development was perhaps less than expected or forecast.  July 20th was one of these days.  Take a look at the NAM Bufr Sounding for HSV, valid for 19 UTC on 20 July 2016 (image 2).

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Image 2.  NAM Bufr Sounding for KHSV, 19 UTC 20 July 2016

The NAM Bufr model sounding indicated robust CAPE values (generally >2500 J/Kg) and little to no CIN.  Now, let’s take a look at a couple of nearby representative NUCAPS soundings (unfortunately, they don’t include the associated data tables).  Image 3 shows the locations of the NUCAPS soundings with respect to the KHSV observation site and the location in the NAM forecast sounding above (image 2).

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Image 3.  NUCAPS Sounding locations for image 4…also, the KHSV location in northern Alabama

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Image 4.  NUCAPS Soundings at 19 UTC for location A (left, west of KHSV) and location B (right, southwest of KHSV), 20 July 2016

Even though data tables are not shown from the NUCAPS soundings, notice that they indicate much less instability and less steep lapse rates than the NAM Bufr sounding prognostications for the same time (19 UTC).   Also, notice that LCL levels are below the LFC, indicating some amount of CIN at both locations.  If memory serves correctly, NUCAPS soundings indicated CIN values around 25-50 J/Kg at this time.  So, for a forecaster struggling with the likelihood/coverage of convective development and the strength of convective updrafts, the NUCAPS data would have suggested lesser magnitude for both, over the NAM progs.  Image 5 shows the general dearth of convective activity in the area of northern Alabama near 19 UTC that day.  And indeed, convection was generally limited through the afternoon, with mostly isolated, small cells present.

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Image 5. Composite reflectivity (dBZ) at 1830 UTC 20 July 2016

When viewing the NUCAPS soundings, I’ve generally been looking for CAPE/CIN values while in the convective season.  Of course, having to click on a number of soundings can be a bit laborious.  As part of a JPSS Proving-Ground/Risk Reduction multi-organization project, researchers at CIMSS, CIRA, GINA and NASA SPoRT have developed gridded NUCAPS data, which were utilized in the Hazardous Weather Testbed this past spring.  I’ll be working with members of the SPoRT team to ingest those data in AWIPS II here at the HUN office in the near future for my own testing, evaluation and feedback to the NUCAPS group within the JPSS Proving Ground.  I’m looking forward to the future use and evaluation of these potentially useful operational data sets.

Here at the Huntsville, AL Weather Forecast Office (WFO) we’ve pointed out total lightning data’s operational utility a number of times in this blog.  After all, the data have been a rather integral part of our severe weather operations for at least 13 years.  Anyway…I’m going to do it again.  I think it can be beneficial to reiterate the value of certain data sets from time to time, especially to reemphasize their operational utility to new members of the forecasting and research community and perhaps newcomers to the SPoRT blog.

This afternoon and evening was a somewhat typical summertime convective event for the Tennessee Valley.  Showers and thunderstorms developed in the early afternoon and gradually increased in coverage and intensity during the mid to late afternoon hours.  By the time I arrived on shift at about 3 pm CDT, a few thunderstorms were showing signs of intense updrafts (~50 dBZ at the -10C isotherm level), but were still not to the level of producing severe weather.  Nevertheless, multiple outflow boundaries interacting with the hot, humid and unstable airmass caused decent coverage of shower and thunderstorm activity, especially in northeastern portions of Alabama during the mid afternoon into the early evening.  A few thunderstorms contained strong updrafts, heavy rainfall, frequent lightning and wind gusts up to about 40 mph.  The first of these started showing signs of strengthening in eastern portions of DeKalb County, AL shortly after 3 pm CDT.  The first image below (image 1) shows a snapshot of total lightning data (flash extent density) from the North Alabama Lightning Mapping Array (NALMA) at 2014 UTC.  Values at this time in the developing storm were just around 10 flashes per 2-minutes.  By 2022 UTC however, flashes had increased to nearly 50 flashes per 2-minutes (Image 2).

Total Lightning (per North Alabama Lightning Mapping Array), 23 July 2016 2014 UTC

Image 1. Total Lightning (per North Alabama Lightning Mapping Array), 23 July 2016 2014 UTC

Image 2.

Image 2.  Total lightning (per NALMA), 23 July 2016 2022 UTC

Importantly, increases in total lightning activity are directly related to updraft strength within storm cells so it was no surprise that reflectivity values increased correspondingly.  The next two images show the increases in Multi-radar Multi-sensor (MRMS) isothermal reflectivity (dBZ) at the -20 C level during the same period (Images 3 and 4).

Image 3. Multi-radar Multi-sensor isothermal reflectivity (dBZ) 23 July 2016 2014 UTC

Image 3. Multi-radar Multi-sensor isothermal reflectivity (dBZ) at -20 C over portions of NW Alabama and NW Georgia, 23 July 2016 2014 UTC

 

Image 4.

Image 4.  Multi-radar Multi-sensor isothermal reflectivity (dBZ) at -20 C over portions of NE Alabama and NW Georgia, 23 July 2016 2022 UTC

Data such as the MRMS isothermal reflectivity when used in conjunction with other data such as total lightning (or flash extent density) allow for a good evaluation of updraft development within thunderstorms and their evolution through time.  Environmental parameters on this day suggested that severe weather was not likely.  Nevertheless, the strengthening updrafts were followed by wind gusts around 30 to 40 mph, which were recorded at a few of our surface observation sites.  Special Weather Statements were used to address this marginal thunderstorm threat during the afternoon and evening.  Interestingly, notice that the total lightning data at 2022 UTC (Image 2) indicated that the updraft in the northern cell in DeKalb County was perhaps the strongest at the time (due to higher values on flash extent density), while MRMS reflectivity values were higher at the same time in the southern cell (image 4).  Subsequently, the northern cell strengthened and became the dominant cell over the next 30 minutes.  On days such as this when there are often multiple thunderstorms ongoing at any one time, and this happens often here in the TN Valley in the summertime, total lightning data can be an effective situational awareness tool for evaluating storms that are undergoing strengthening and helping to provide proper focus for operational meteorologists.

NWS Huntsville is providing Impact-Based Decision Support Services (IDSS) to protect life and property at an outdoor sporting competition in the Decatur, Alabama area this week.  A decaying Mesoscale Convective System (MCS) moved across north Alabama this afternoon, forcing a delay in the competition for several hours.  While the North Alabama Lightning Mapping Array (NALMA) helped determine what to tell local emergency managers about the start of the lightning threat, the NALMA really shined in trying to figure out when the lightning threat would end.

KGWX Radar Reflectivity and North Alabama Lightning Mapping Array, valid 1949 UTC 14 July 2016

KGWX Radar Reflectivity and North Alabama Lightning Mapping Array, valid 1949 UTC 14 July 2016

The example images include NALMA Flash Extent Density data, which are represented by irregular pink and purple shapes displayed over the KGWX radar reflectivity.  Both the 1949 and 2007 UTC indicate scattered very low flash rates extending over a broad area–including the Decatur area–suggesting occasional in-cloud flashes within the trailing stratiform region of the MCS.  This is a known threat with MCSs, but it was not clear at the time how long the lightning threat would persist.  Use of total lightning information from NALMA enabled NWS Huntsville staff to determine that the lightning threat would not subside until rain subsided.

KGWX Radar Reflectivity and North Alabama Lightning Mapping Array, valid 2007 UTC 14 July 2016

KGWX Radar Reflectivity and North Alabama Lightning Mapping Array, valid 2007 UTC 14 July 2016

With the launch of GOES-R and the Geostationary Lightning Mapper, these kinds of data will improve lightning-based IDSS across a much wider cross section of the CONUS.

On April 27, 2011, a severe weather outbreak occurred across the southeastern United States, resulting in 199 tornadoes across the region and over 300 fatalities (NWS 2011 Service Assessment).  Alabama was among the states hardest hit, with 68 tornadoes surveyed by the National Weather Service (NWS) Weather Forecast Offices (WFOs) in Huntsville, Birmingham, and Mobile, Alabama, and over 250 reported fatalities in the state. Huntsville, home to NASA’s Marshall Space Flight Center and the Short-term Prediction Research and Transition (SPoRT) Center, lost power along with most of Madison County after tornadoes severed major utility lines.  The power outage lasted well over a week in some areas. Once power was restored, SPoRT team members were able to provide satellite imagery to our partners in the National Weather Service to help clarify some of the high-intensity tornado damage tracks that occurred throughout the state. SPoRT provided pre- and post-event difference imagery at 250 m spatial resolution from the Moderate Resolution Imaging Spectroradiometer (MODIS) and 15 m false color composites from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). These surveys helped our NWS partners confirm their ground surveys, but also helped to correct the characteristics of several tracks (Molthan et al. 2011). Many of these products remain available through the SPoRT web page (link) and also through the USGS Earth Explorer portal (link).

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The MODIS Band 1 difference image above shows some of the scars left behind by the April 27, 2011 tornado outbreak. Radar snapshots were taken from various times to identify the supercell thunderstorms associated with each track.  Reproduced from Molthan et al. 2011.

Follow-on studies examined the capability of various NASA sensors for detecting and measuring the length and width of scars visible when using the Normalized Difference Vegetation Index, or NDVI, a measurement of vegetation greenness and health commonly derived from multiple satellite imaging platforms.  SPoRT examined NDVI products from MODIS (250 m), Landsat-7 Enhanced Thematic Mapper Plus (ETM+, 30m) and ASTER (15 m) collected in May and June 2011. Possible tornado tracks were identified, mapped, and were then measured to compare against the official NWS damage surveys.  In general, many of the major tornadoes (defined here with maximum intensity EF-3 and greater) were at least partially visible at resolutions of 15-250 m, though weaker tornadoes or those that occurred in complex terrain were more difficult to detect using NDVI and a single snapshot in time. As tornadoes initiated and increased in intensity, or dissipated and decreased in intensity, some of their characteristics became more difficult to detect.  However, some weaker tornadoes were also apparent in Landsat-7 imagery (30 m) in well-vegetated areas.  A summary of the study is available as a publication in the National Weather Association’s Journal of Operational Meteorology. In 2013, SPoRT received support from NASA’s Applied Sciences: Disasters program to partner with the NWS and facilitate the delivery of satellite imagery to their Damage Assessment Toolkit (DAT).  The DAT is used by the NWS to obtain storm survey information while in the field. Satellite imagery from NASA, NOAA, and commercial sensors (acquired in collaboration with USGS and the Hazards Data Distribution System) helps to supplement the survey process by providing an additional perspective of suspected damage areas.

Many of the damage scars apparent from the April 27, 2011 outbreak exhibited signs of recovery and change in the years following the outbreak.  Other tornado events also brought additional vegetation damage and scarring to the region. With five years passing since the 27 April 2011 tornado outbreak, annual views of cloud-free imagery have been obtained from the Landsat missions, operated and managed as a collaboration between the USGS and NASA.  In the viewer linked below, SPoRT has collaborated with the USGS Earth Resources Observation Systems (EROS) Data Center to acquire 30 m true color and vegetation index information from Landsat 5, Landsat 7, and Landsat 8 during the late spring and summer months when local vegetation is at its greenest, allowing the greatest contrast between damaged and undamaged areas. Users can take a look at these images in a web viewer that allows toggling between different products and years, view some of the tornado tracks surveyed by the NWS following the April 27, 2011 event, and zoom into areas of interest to examine how some of the affected areas have evolved over time:

Tuscaloosa, AL

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The above animation shows the year before and years after the EF-4 tornado impacted the Tuscaloosa area. The tornado track has seen a significant recovery, but a scar still remains in 2015. In addition to seeing how the landscape as recovered from tornado, development in and around Tuscaloosa is also apparent.  Missing pixels in 2012 are due to an issue with the Landsat-7 imager.

Hackleburg-Phil Campbell

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Similar to the Tuscaloosa animation, this animation shows the recovery of the EF-5 tornado that moved through Hackleburg and Phil Campbell, before tracking northeast across the Tennessee River.  Missing pixels in 2012 are due to an issue with the Landsat-7 imager.

Gridded NUCAPS products developed as part of a multi-organization JPSS PG/RR project are currently being evaluated at the Hazardous Weather Testbed (HWT) Experimental Warning Program (EWP).  The project contains contributions by researchers from UW/CIMSS, CSU/CIRA/ UAF/GINA, and SPoRT.  NUCAPS soundings are retrieved temperature and moisture soundings from the Suomi-NPP CrIS and ATMS sounders.  The evaluation of NUCAPS at HWT is aimed at providing upper air temperature and moisture information in the pre-convection environment to better understand variables that are necessary for convection and severe weather.  The Gridded NUCAPS products allows for isobaric plan views of temperature and moisture that forecasters can use to gain confidence in the model output

Forecasters at the HWT-EWP posted some input on the use of the Gridded NUCAPS products.  On the Satellite Proving Ground at HWT Blog (http://www.goesrhwt.blogspot.com/2016/04/nucaps-planviews.html), a forecaster noted:

“[Gridded NUCAPS] would be beneficial in the forecasting environment as added temperature data would be available in between standard upper-air launches.  This could serve as a good proxy to help judge the strength of a capping inversion, while also possibly serving as an additional information source during winter wx events.

However, the forecaster also noted that the amount of missing data included in the product limits its utility.  Currently, the Gridded NUCAPS contains only the highest quality (i.e., “best”) data that comes from a combination of both microwave and infrared (top image below).  In this image, the dark blue pixels represent the data that are discarded due to QC issues.  However, this quality control can be strict at times and leave out “good” data that can still be useful to the forecasters.  When these “good” data are included, there are much more useful data (bottom image below) without any noticeable discontinuities or oddities in the data.

SPoRT plans to use the feedback from HWT-EWP participants to test pushing the inclusion of the “good” quality data to the Gridded NUCAPS product to provide forecasters with more data for their analysis.

NUCAPS.2016.04.21.1902329.853mbtemp_QCeq1

853 hPa Gridded NUCAPS temperature product from 21 April 2016 at 1902 UTC including only the highest quality flags.  Dark blue pixels denote discarded data that results in data gaps.  Note that a lot of over-land observations are discarded.

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853 hPa Gridded NUCAPS temperature product from 21 April 2016 at 1902 UTC including both “best” and “good” quality flags.  Dark blue pixels denote discarded data.  Missing pixels generally correspond to thick cloud features.

 

On April 16th a fire was reported in the Shenandoah National Park in eastern Rockingham County, Virginia, situated roughly between the cities of Harrisonburg and Charlottesville. Estimated at about 500 acres (per latest news reports), the fire (named the Rocky Mountain Fire) is large enough and producing a sufficient amount of smoke to be seen in Geostationary satellite data from GOES-13 this afternoon (Image 1).

GOES_AfternoonLoop_18Apr2016

Image 1. GOES visible loop, 1646-1845 UTC, 18 April 2016.  A plume of smoke can be seen extending SSE of the fire in the central portion of the image.  The Charlottesville, VA observation site (in the path of the smoke) contains a report of smoke in the last couple of frames of the loop.

However, the fire can also be seen in Day-Night Band Imagery, produced by the VIIRS instrument aboard the Suomi-NPP satellite.  The first image below (image 2) shows no visible fire early on the morning of the 16th and the growth of the fire over the next couple of mornings in the next two images (images 3, 4).

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Image 2.  VIIRS Day-Night Band Radiance RGB, 0729 UTC 16 April 2016. The circle shows the eventual location of the fire (although not evident yet in this image from the morning of April 16th).

 

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Image 3. VIIRS Day-Night Band Radiance RGB, 0710 UTC 17 April 2016. The small white dot in the center of the circle likely represents the fire early on the morning of the 17th.

 

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Image 4. VIIRS Day-Night Band Radiance RGB image, 0615 UTC 18 April 2016, showing the much larger “Rocky Mountain Fire” in portions of the Shenandoah Nat’l Park in eastern Rockingham County, VA.

 

On December 23, 2015, an unusual early winter season tornado outbreak struck much of the Tennessee Valley. Several tornadic supercell thunderstorms developed across northern Mississippi and western Tennessee in the afternoon hours, producing several large long-track tornadoes that unfortunately resulted in numerous fatalities and injuries. These same storms then moved rapidly east-northeastward at up to 70 mph across Middle Tennessee during the evening, spawning 4 tornadoes and causing 2 deaths and 7 injuries. Prior to this tornado outbreak, only 7 tornadoes had ever been recorded across Middle Tennessee since the 1800s, easily making this the largest and worst December tornado outbreak in Middle Tennessee history.

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OHX radar base reflectivity (left) & storm-relative velocity (right) at 623 pm CST on December 23, 2015 showing a supercell thunderstorm with an EF2 tornado in progress southeast of Linden, TN

NWS Nashville sent out three storm survey teams to evaluate all of the damage from these tornadoes on Christmas Eve and again on Christmas Day. Unfortunately, the affected areas were very rural and mostly inaccessible to the storm survey teams, with few roads available to evaluate damage indicators or determine beginning and end points. Thankfully, Landsat 8 imagery was available in the online Damage Survey Interface (DAT beta version) that depicted the swaths of blown down forests along the tornado paths that tracked through areas where the storm survey teams could not access. Landsat imagery allowed NWS Nashville personnel to extend two of the tornado paths by several more miles than originally estimated.

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Landsat 8 panchromatic imagery (contrast enhanced) from March 22, 2016 showing the damage swath from an EF2 tornado that killed 2 people southeast of Linden, TN. The beginning point of this tornado was adjusted ~2 miles further southwest than originally estimated based on the satellite imagery.

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