Supplemental Soundings Today for Potential Severe Weather

Just a heads up that some supplemental atmospheric soundings are expected today from Dr Douglas Miller’s group at UNC Asheville. A 12 UTC sounding is already available and a 15 UTC sounding is anticipated.  You can access them at… http://www.atms.unca.edu/iphex/rt_iphex_2014.html.

iphex2014_iop20_snd01

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SPC Mesoanalysis Products Including the SHERB during the 08 October High-Shear Low-CAPE Tornado Event in WV

(with contributions from Steve Keighton)

Late in the evening on Tuesday, 7 October 2014, a high-end EF1 tornado struck Mercer County West Virginia in the WFO Blacksburg, VA CWA. The Mercer County tornado produced significant tree damage, minor damage to a few homes and barns, and significant damage to a mobile home that injured two residents (Fig. 1). The tornado was on the ground from 1139 PM EDT to 1149 PM EDT between Matoaka and Spanishburg,  in far southern West Virginia, around 10 miles from the Virginia border (Fig 2.). The tornado had a path length of 5.5 miles and estimated maximum wind speeds of 105 MPH.

Figure 1.  Single wide mobile home was lifted and thrown in the opposite direction of storm motion producing non-life threatening injuries to an adult and child. Numerous trees were blown down in a perpendicular manner to the storm motion (right).

Figure 1. Single wide mobile home was lifted and thrown in the opposite direction of storm motion producing non-life threatening injuries to an adult and child. Numerous trees were blown down in a perpendicular manner to the storm motion (right).

Figure 2. Zoomed in tornado track is shown in red with larger regional perspective shown in the insert.

Figure 2. Zoomed in tornado track is shown in red with larger regional perspective shown in the insert.

Other severe weather was observed in the eastern Ohio Valley and central Appalachians on Tuesday and Tuesday night including an EF2 tornado near Raleigh, West Virginia (see SPC storm reports). The Raleigh tornado occurred in the WFO Charleston, WV CWA, about an hourly earlier but only 10 miles north of the Mercer County Tornado.

Figure 3. The regional reflectivity radar composite from 0330 UTC.

Figure 3. The regional reflectivity radar composite from 0330 UTC.

While a thorough case study and analysis of the forecast process and guidance is unavailable at this time, we thought we would share some of the SPC mesoanalysis products near the time of the tornado touch down between 0339 and 0349 UTC on 8 October. Figure 3 is the 0330 UTC regional reflectivity radar composite. The storms of interest are located across far southern West Virginia, in a broken line with embedded shallow supercells.

Figure 4. Radar imagery from the kfcx radar at 0342 UTC on 8 October with base reflectivity data at 0.5 degrees (left) and the 0.5 degree storm relative velocity imagery (right).

Figure 4. Radar imagery from the kfcx radar at 0342 UTC on 8 October with base reflectivity data at 0.5 degrees (left) and the 0.5 degree storm relative velocity imagery (right).

Radar imagery at a time when the tornado was on the ground is shown in fig. 4 from KFCX (Blacksburg, VA) at 0342 UTC on 8 October. Base reflectivity data at 0.5 degrees is shown on the left with a high reflectivity core noted northeast of Matoaka. The 0.5 degree storm relative velocity imagery is shown in fig. 4 to the right with a small and compact circulation noted southeast of Arista.

Figure 5. SPC mesoanalysis from 0300 UTC on 08 October 2014 of 0-6 km bulk shear in kts.

Figure 5. SPC mesoanalysis from 0300 UTC on 08 October 2014 of 0-6 km bulk shear in kts.

Strong deep layer flow was noted over the Ohio Valley and Appalachians with the 0-6 km bulk shear analyzed by SPC between 60 and 70 kts (Fig. 5). The air mass across the southern Appalachians was only weakly unstable (Fig. 6) with the SBCAPE values analyzed around 100 J/Kg (left) and MUCAPE values between 100-250 J/Kg (right) at 0300 UTC. These bulk shear and instability values are consistent with High-Shear Low-CAPE (HSLC) events.

Figure 6. SPC mesoanalysis from 0300 UTC on 08 October 2014 of SBCAPE (left) and MUCAPE (right).

Figure 6. SPC mesoanalysis from 0300 UTC on 08 October 2014 of SBCAPE (left) and MUCAPE (right).

Figure 7. SPC mesoanalysis from 0300 UTC on 08 October 2014 of the SHERB parameter.

Figure 7. SPC mesoanalysis from 0300 UTC on 08 October 2014 of the SHERB parameter.

A key outcome of a recent CSTAR project is a new experimental parameter called SHERB to identify the potential for tornadoes and significant severe wind events in HSLC environments. The SHERB parameter is a product of the 0-3 km shear magnitude, the 0-3 km lapse rate, and the 700-500 hPa lapse rate normalized so that the optimal SHERB threshold is 1. SHERB values above 1 are more likely to be associated with significant severe convection than non-severe convection. The SPC mesoanlysis of the SHERB parameter from 0300 UTC (Fig. 7) indicated a region of elevated threat with SHERB values ranging between 1.0 and 1.25 across the central Appalachians.

SPC composite convective parameters including the Significant Tornado Parameter and the Supercell Composite Parameter are shown in Fig. 8.  These composite parameters suggest the greatest significant tornado or supercell threat was located across the Tennessee Valley and the southern Appalachians, near but not coincident with the location of the tornado. Additional insight into the mesoscale environment can be gleamed from the SPC Mesoscale Discussions issued at 1950 UTC and 2359 UTC on 07 October.

Figure 8. SPC mesoanalysis from 0300 UTC on 08 October 2014 of the Significant Tornado Parameter (left) and the Supercell Composite Parameter (right).

Figure 8. SPC mesoanalysis from 0300 UTC on 08 October 2014 of the Significant Tornado Parameter (left) and the Supercell Composite Parameter (right).

Thanks to Phil Hysell and Robert Stonefield from WFO Blacksburg who conducted the Mercer County storm survey and provided the photos.

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Examples of Gust Factor at Water-Land Interface

The CSTAR TC Winds team recently had a conference call reviewing the performance of our experimental tools and methodologies during the 2014 hurricane season. During the discussion of our experiences during Hurricane Arthur, one issue was noted with the performance of the TC Wind Gust methodology at the immediate coast where differing gust factors for the land and marine locations result in some unrepresentative data. The images below demonstrate the issue and a potential work around.

Sustained Winds:
Sustained

Gust Factors:

over all land=1.50/all water=1.25                  1.50 inland/ 1.375 land near coast/ 1.25 waterGustGustsNew

Note the higher gusts over land in above image on left compared to adjacent water areas in narrow strip of coastal southeast VA. Image at right uses a third gust factor of 1.38 in region of 2-3 grid points (land within 5 to 7.5 km of water). This removes the bias for the most part.  Just experimenting here, exact values of gust factors may vary slightly. Let me know what you think, Thanks, Larry B.

Posted in CSTAR, TC Inland and Marine Winds | 2 Comments

Two CSTAR Supported High-Shear, Low-CAPE Published in Weather and Forecasting

In case you missed it, the most recent edition of Weather and Forecasting features two articles from NC State collaborators investigating High-Shear, Low-CAPE (HSLC) Environments as a part of a previous CSTAR project. A followup project entitled “Improving Understanding and Prediction of High Impact Weather Associated with Low-Topped Severe Convection in the Southeastern U.S.” is getting underway and will build off of the previous HSLC research.

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HMT-Southeast Pilot Study Concluding

Dear HMT-Southeast community,

hmt.sepsAs summer draws to a close, the HMT-Southeast Pilot Study (HMT-SEPS) is also nearing the end of its ~16-month field deployment period. We want to thank you, the HMT-Southeast community, for a successful field project that has certainly proven to be a foundation upon which many meaningful partnerships have been built. We would like to take this opportunity to provide a summary of HMT-SEPS activities and future plans, and in addition, we hope that this correspondence will encourage community dialogue regarding ongoing and future related projects.

The summary below aims to highlight some select HMT-SEPS project accomplishments over the past couple of years. For additional information on HMT-SEPS in general, earlier documents can be found here and the HMT-SEPS Facebook page provides a useful timeline of HMT activities and events in the region. In addition, you can always feel free to contact our HMT-SEPS team with additional questions or follow-up.

Review of HMT-SEPS objectives:

  • The objective of the HMT-Southeast Pilot Study was to provide advanced hydrometeorological observations focused in western North Carolina, with some instrumentation also located in central and coastal NC.
  • HMT-SEPS was made possible by partnering with NASA’s IPHeX ground validation campaign.
  • HMT-SEPS was also able to identify and pursue several key Southeast-focused “science questions” targeting operationally-relevant heavy-precipitation-related topics (see “Research” below)

Observations, Instrumentation, and Field Deployment:

  • Four wind profiling radars and six surface meteorology sites were installed by NOAA HMT. Most of this instrumentation (with the exception of New Bern, NC) will be removed from the field beginning October 2014.
  • Two NC DENR/DAQ-owned wind profilers (Clayton, NC and Charlotte, NC) were repaired/upgraded and brought back on-line. These systems will continue to operate under the NC DENR/DAQ and data will continue to be available online through HMT and MADIS.
  • Observations have been available in real-time for all users since 2013, and archived data will remain available for download and data analysis.
  • HMT supported additional radiosonde balloon launches during IPHeX thanks to UNC-Asheville faculty and students.
  • HMT supported gap-filling radar observations during IPHEX thanks to NSSL staff and students from the Univ. of OK.
  • Support from the NOAA Hurricane Sandy Supplemental (Disaster Relief Act) has allowed us to add three new Atmospheric River Observatories in the Southeast; these will remain through the 2015 hurricane season.

HMT-SEPS research has been driven by the following main themes:

  • The Climatology of Southeast US Extreme Precipitation Events (Lead by ESRL PSD, B. Moore et al. 2014 (MWR, in press))
  • SE US QPF error climatology (Efforts ongoing at ESRL PSD, North Carolina State University; Baxter et al. 2014)
  • Case Studies of heavy precipitation events (e.g., a 2013 western NC flash flood)
  • Heavy precipitation processes and the relevance of “atmospheric rivers” to heavy SE precipitation (Efforts ongoing at ESRL PSD)
  • Bulk microphysical characteristics of NC precipitation observed with disdrometers and vertically pointing precipitation profilers; assess performance of default NEXRAD rainfall algorithms. (ESRL PSD)
  • Performance assessment of radar, gauge, and multi-sensor QPE in the upper Catawba river basin (ESRL PSD, OHD)

Work along all of these themes will continue into FY15 thanks in large part to support from the Sandy Supplemental funding. We plan to keep posting publication information and presentations on research findings on the HMT-Southeast Documents page. Please feel free to be in touch for additional details about any of these projects.

Collaborations and partnerships:

We have been incredibly fortunate to have established fruitful partnerships with many groups and individuals in our HMT-Southeast community. From supporting university students to learning from WFO forecasters who have been in the trenches during heavy precipitation events of interest, any success that HMT-SEPS can claim is very much attributable to our interactions with all of you.

Some of our key partnerships over the past few years have included: NASA, Duke, NCSU, CSTAR/USWRP, UNCA, NCAR, WPC, NSSL, NWS Eastern Region, and NWS WFOs (GSP and RAH in particular!). This is by no means a complete list, and it has been our pleasure to work with everyone in this uniquely engaged and motivated meteorological community.

The Future:

  • The New Bern, NC ARO will remain in place for an additional 12 months (through November 2015).
  • The 3 new AROs at Johns Island, SC, Moss Point, MS and Sydney, FL will operate through November 2015. Observations can be accessed here.
  • Research studies will continue as outlined above with support provided by NOAA ESRL PSD and the Sandy Supplemental funding award. Several collaborative efforts will also continue (e.g., NCSU/CSTAR, QPE/OHD) thanks to external support as well.
  • Additional and/or future HMT efforts in the Southeast US will be determined by external interest and available funding.

We hope to remain engaged with the HMT-Southeast community as we continue to make progress on research efforts as described above, and we aim to present and publish our findings on these projects throughout the next year or so. We also plan to continue to serve the community by continuing to host HMT-SEPS observations for download, as well as make ourselves available for future collaborations on relevant regional endeavors.

Please feel free to be in touch with any questions, comments, or project feedback. We look forward to future collaborations. Sincerely,

The NOAA HMT Southeast Team

Kelly Mahoney

Rob Cifelli

Ellen Sukovich

Allen White

Clark King

 

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N.C. State – NWS CSTAR Project Examining High-Shear Low-CAPE Convection Starting to Ramp Up

Improving Understanding and Prediction of High Impact Weather Associated with Low-Topped Severe Convection in the Southeastern U.S.The project entitled “Improving Understanding and Prediction of High Impact Weather Associated with Low-Topped Severe Convection in the Southeastern U.S.” will be a collaboration between principal investigators (PIs) and students at N.C. State University in collaboration with a dozen WFOs in the Southeast along with the Storm Prediction Center and the HMT group at the Earth System Research Lab. The three-year project is being funded as a part of the NOAA/NWS Collaborative Science, Technology, and Applied Research (CSTAR) Program. This project will build off of previous collaborative research between N.C. State and the NWS which has had very successful research to operation results along with the integration of students into NOAA and the NWS.

Severe convective storms in environments with large vertical wind shear and marginal instability (so-called “high-shear low-CAPE”, or “HSLC” events) represent a significant short-term, high-impact forecasting and warning challenge, particularly in the Southeastern and Mid-Atlantic states of the U.S. These environments account for a substantial fraction of severe wind and tornado reports in the region, and they are present for many hours each year. The long-range goal of the research is to improve predictions and warnings for hazardous weather in HSLC environments.

The research will be conducted through a set of collaborative research studies that are listed below:

  • HSLC process study using idealized modeling and emulated radar sampling (PI Dr Parker along with students Keith Sherburn and Jessica King)
  • Operational NWP Resolution and sensitivities study using HSLC event hindcasts (PI Dr Lackmann along with student Lindsay Blank)
  • Predictability study using ensembles and dynamical-statistical downscaling (PI Dr Xie along with Dr. Bin Liu and student Dianna Francisco)
  • Operational assessment of HSLC forecasting composite parameters (PI Dr Parker along with student Keith Sherburn)

Participants have been invited to a workshop this November in Raleigh to share results from the previous CSTAR research and to spin up the new collaboration with discussions on project execution. Prior to the workshop, Keith Sherburn will be leading a webinar providing a review of the previous HSLC research and an introduction to an operational assessment of HSLC forecast parameters that begins this fall in earnest.

Posted in CSTAR, High Shear Low Cape Severe Wx | 1 Comment

Evolution of the NASA SPoRT LIS 0 to 10cm Below Ground Relative Soil Moisture Product During an Extreme Rainfall Event

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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