“Orographically Induced Cirrus Clouds in the Lee of the Southern Appalachian Mountains” published in NWA Journal of Operational Meteorology

Stations

GOES Infrared Satellite Imagery from 1145 UTC on 7 January 2015 showing the relative locations of KGSO, KRDU, KRWI, and KFAY.

For those that have been following some of the Orographic Cirrus posts that have been on here over the last couple of years, the NWS WFO Raleigh is proud to announce that this work has been published in the National Weather Association Journal of Operational Meteorology and can be found at http://www.nwas.org/jom/abstracts/2015/2015-JOM10/abstract.php.  The .pdf can be attained through the NWA website.  Thanks to the many on this list that have provided valuable feedback and support throughout this project. The abstract follows.  -Ryan Ellis (WFO RAH)

The development of orographically induced cirrus clouds in the lee of the southern Appalachian Mountain chain can result in areas of unanticipated cloudiness downstream of the higher terrain across the Carolinas and Virginia. Both the degree of cloudiness and its impact on surface temperatures can reduce forecast accuracy. The general environmental conditions favorable for orographic cirrus development are known and have been qualitatively documented but to this point have not been extensively quantified. This study attempts to quantify the conditions necessary for orographic cirrus development across the southern Appalachian Mountains. Geostationary Operational Environmental Satellite imagery and atmospheric soundings are evaluated in order to better understand the most important environmental conditions needed for an orographic cirrus event to occur as well as which scenarios may produce null events. Case studies will be presented illustrating classic orographic cirrus events and their impacts on local forecast variables. Finally, best practices for operational forecasting of orographic cirrus are proposed, and the role of high-resolution models in the detection of orographic cirrus events is discussed.

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Resources to Assist with QLCS Tornado Warning Decision Making

I wanted to pass along some work that WFOs Springfield and St. Louis MO along with other partners have been doing relating to efforts to improve QLCS Tornado Warnings. These efforts have an overlap with some of the our HSLC CSTAR work.

Jason Schaumann, Lead Forecaster WFO Springfield, MO will be providing a presentation discussing some of this work during an upcoming conference call, likely in October. Prior to the October call, it would be helpful to have our group work through the links below including the SLS manuscript, Hollings website, Google Site, and YouTube videos. The two YouTube presentations are a great overview of all of the work over the last five years. During the call, Jason can help if anyone would like further explanation, or examples, or alternatively, he can demonstrate through a case study.

Snapshot of a reference for the Three Ingredients method for Meso Genesis, Intensification, and Tornadogenesis in a QLCS

Snapshot of a reference for the Three Ingredients method for Meso Genesis, Intensification, and Tornadogenesis in a QLCS

The initial work: Operational Application of 0-3 Km Bulk Shear Vectors in Assessing QLCS  Mesovortex And Tornado Potential by Jason Schaumann and Ron Pryzbylinski describes the three ingredients method for anticipating mesovortex genesis and rapid intensification. This methodology applies for both the cold and warm seasons. A statistical research project was conducted by a Hollings Scholar student to show the statistical significance of the three ingredients method.

Subsequently they worked to identify additional mesoscale and radar signatures that represent an increased probability for damaging winds and tornadoes from mesovortices. The recent culmination of these efforts includes guidance for issuing severe thunderstorm and tornado warnings for mesovortices.  Most recently, Michael Mathews from Bismark, ND developed a two page handout and video condensing and highlighting this work.

Jason constructed a Google Site which summarizes all of this work. Included on this site are two recent webinars that were given to Central Region (and a few Southern Region) offices. The first presentation covers the three ingredients method while the second presentation covers radar and warning strategies.

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

HSLC Idealized Hodograph Sensitivity Studies: Overview of all 12 Simulations

During the July conference call, I presented preliminary work from a matrix of 12 simulations geared towards exploring the sensitivity of HSLC convection to low-level hodograph shape and the wind profile’s orientation relative to an initiating cold pool. As I focused on only four of the 12 simulations, one of the requests stemming from discussion during the call was to see simulated reflectivity, cold pool, vertical vorticity, and vertical velocity animations in addition to rotation track Hovmoller plots for all 12. These are attached as a set of powerpoint slides at the end of this post, along with a refresher of the hodographs used in this study.

12pan_overview

Snapshot of all 12 simulations at t = 100 min. Animations are available in the attached powerpoint.

Ultimately, the four “core” simulations discussed during the July conference call (control L-shaped, CCW ball cap, control quarter turn, and control spatula) exhibit the most realistic and representative HSLC convection. However, interesting features are shown in the other simulations, including situations with overrunning convection and shear-parallel bands of convection. Some of the simulations not included in the core set still produce strong near-surface rotation and may be worth future investigation.

Further analysis and discussion, particularly on the four core simulations, is provided in an extended abstract associated with a recent presentation of this work at the AMS Mesoscale Conference. A link to this document will be provided in an upcoming blog.

Powerpoint: hodo_12pans

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Last Days of GOES-14 Super Rapid Scan Operations

GOES-14 Super Rapid Scan Operations for GOES-R (SRSOR) will end on 22 August, 2015. Super Rapid Scan Operations (SRSO) provides 1-minute imagery to support multiple research and GOES-R/S user readiness activities. The SRSO domain is usually selected a day or two in advance. The domain schedule along with selected imagery from prior days is available at: http://cimss.ssec.wisc.edu/goes/srsor2015/GOES-14_SRSOR.html#sched_and_movies

Yesterday, the domain included much of the Mid Atlantic and provide a very nice view of developing convection as noted in the loop of AWIPS imagery shown at the bottom of the post. The loop includes one minute visible satellite imagery and a regional radar composite updated every 6 minutes.

Today, the domain for the 1-minute imagery is centered over Hurricane Danny well out in the Atlantic.

GOES SRSOR visible satellite loop from 1806-1933 UTC on 21 August 2015

GOES SRSOR visible satellite loop from 1806-1933 UTC on 21 August 2015

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GOES-14 will be in Super Rapid Scan Operations with imagery over the Carolina’s and Virginia’s Today (8/10)

GOES SRSOR visible satellite loop from 1730-2359 UTC on 09 June 2015

GOES SRSOR visible satellite loop from 1730-2359 UTC on 09 June 2015

GOES-14 Super Rapid Scan Operations for GOES-R (SRSOR) will begin on 10 August and will continue for through 21 August, 2015. Super Rapid Scan Operations (SRSO) will provide 1-minute imagery to support multiple research and GOES-R/S user readiness activities. The SRSO domain is usually selected a day or two in advance. The domain schedule along with selected imagery from prior days is available at: http://cimss.ssec.wisc.edu/goes/srsor2015/GOES-14_SRSOR.html#sched_and_movies  Additional background information including training and links to online imagery is available at: http://cimss.ssec.wisc.edu/goes/srsor2015/GOES-14_SRSOR.html

This will be a great opportunity to view the data over our region. NWS forecasters will be able to view some of this data in real-time in AWIPS-2. An example of GOES SRSOR imagery during a test this past June is shown in the image above.

Imagery including visible, infrared, and water vapor is available on the web at the links below…

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CSTAR High-Shear Low-CAPE Conference Call Notes – July 2015

July 2015 CSTAR High-Shear Low-CAPE Conference Call Notes

The call occurred on Tuesday, July 28th, from 11AM to around 1145 AM EST. There were participants from NC State, AKQ, BMX, CAE, GSP, HUN, LWX, RAH, RNK, and SPC.

1) Research update from Keith Sherburn on the HSLC process study using idealized modeling and emulated radar sampling project. The slide deck is available for downloading at https://goo.gl/0iJUna

  • imageSubtle changes in low-level hodograph shape and orientation have a large impact on convective evolution in HSLC environments, as shown by a matrix of 12 simulations.
  • Streamwise vorticity/storm-relative helicity in lowest levels is critical for strong, rotating updrafts and intense low-level vortices due to enhanced dynamic lifting.
  • The amount of line-normal flow even in the lowest 1 km affects the ability for convection to move off of an initiating boundary.
  • Hodograph shape aloft plays a role in precipitation fallout, ultimately altering the proximity of adjacent updrafts/downdrafts from neighboring cells, potentially influencing the life cycle of low-level vortices.
  • Future work will examine the development and failed development of intense, long-lived, low-level vortices in these simulations and compare their origins to those in higher-CAPE environments.

2) Research update from Lindsay Blank on the operational NWP resolution and sensitivity study using HSLC event hindcasts project.

The slide deck is available for viewing at https://goo.gl/er5HZS

  • Lindsay is focusing on three metrics: radar reflectivity, hourly precipitation, and rotational tracks.
  • The new model setup is being used. It appears that the model is overactive in the coarser the domain.
  • Preliminary results indicate that WRF produces more hourly precipitation than Stage IV observations.

 3) Discussion of QLCS Tornado Warnings Work in central Region at WFO Springfield MO

Jonathan previously passed along some notes on the work that WFO Springfield MO and other partners have been doing relating to efforts to improve QLCS Tornado Warnings. Jason Schaumann, SOO NWS Springfield, MO, provided much of the information shown below. Based on some initial feedback, we are planning on inviting Jason to present some of his work in a future conference call.

The initial work: Operational Application of 0-3 Km Bulk Shear Vectors in Assessing QLCS  Mesovortex And Tornado Potential by Jason Schaumann and Ron Pryzbylinski describes a three ingredients method for anticipating mesovortex genesis and rapid intensification. This methodology applies for both the cold and warm seasons. A statistical research project was conducted by a Hollings Scholar student to show the statistical significance of the three ingredients method.

Subsequently they worked to identify additional mesoscale and radar signatures which represent an increased probability for damaging winds and tornadoes from mesovortices. The recent culmination of these efforts includes guidance for issuing severe thunderstorm and tornado warnings for mesovortices.  Most recently, Michael Mathews from Bismark, ND developed a two page handout and video condensing and highlight this work. Jason has constructed a Google Site which summarizes all of this work. Included on this site are two recent webinars that were given to Central Region (and a few Southern Region) offices. The first presentation covers the three ingredients method while the second presentation covers radar and warning strategies.

4) Next Conference Call

Since many of the NC State students have different schedules this semester because of classes, we will need to identify a time to have regular monthly calls. Please keep an eye out for an email requesting input.

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A Brief Look at Rapid Environmental Changes in a HSLC Case (January 29-30, 2013)

Note: A few figures are provided in the following PowerPoint: Figures

One of the goals of the current CSTAR project is to study the environmental evolution that occurs during HSLC events.  Dr. Parker and I have been primarily focused on the changes in the synoptic-to-mesoscale environment in the ~6 hours leading up to convection. In order to study a handful of HSLC events, we have performed simulations with the Advanced Research Weather Research and Forecasting (WRF-ARW) model using NAM analyses as initial and boundary conditions. These simulations are run at 3 km horizontal grid spacing, and data is output every 5 minutes.  This allows us to examine the evolution of the simulated synoptic and mesoscale environments on relatively small time and spatial scales.

Animations of simulated composite reflectivity and surface equivalent potential temperature (see PowerPoint link) inform us that these environments can change very rapidly, and that the associated boundaries (e.g., cold fronts, outflow) can be quite extreme. In the particular case shown from January 29-30, 2013, an intense outflow boundary races ahead of a surface cold front, triggering significant convection in Tennessee and Kentucky regardless of CAPE values less than 500 J/kg. An interesting thing to note is the increase of surface equivalent potential temperature just ahead of the outflow boundary as it approaches; this occurs from 0500 to 1000 UTC and therefore cannot be attributed to diurnal heating. Our goal is to clarify how the environment is changing in the few hours prior to severe convection.

In order to determine how and why CAPE might be changing, we took 6 hour boundary-relative time series of surface based CAPE, surface potential temperature, surface mixing ratio, and lapse rate at several points ahead of the outflow boundary and took an average (see plots in PowerPoint link). Increases in all variables are evident, though some increase more than others.  This is common among the several cases we have simulated thus far.

The question we are targeting to answer here is how changes in each of these variables individually affect CAPE.  The next step is to determine how much of the increases in surface-based CAPE can be attributed to increases in solely surface temperature and/or surface moisture.  We have made some progress in answering this question and an update will be provided soon.

Posted in CSTAR, High Shear Low Cape Severe Wx | Tagged , | 3 Comments