Potential HSLC severe event Thursday, March 24th, including VORTEX-SE deployment

A potent upper-level trough (Fig. 1) and associated surface cyclone (Fig. 2) moving through the eastern CONUS will bring a chance for severe high-shear, low-CAPE (HSLC) convection to portions of the Ohio and Tennessee Valleys on Thursday. This event is especially noteworthy because in addition to potentially affecting several collaborating CWAs, the VORTEX-SE project (including CSTAR students Jessica King and Keith Sherburn from NC State) will be operating in and near Huntsville, AL.

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Figure 1. 500 hPa absolute vorticity (1/s) and geopotential heights (m) for 0000 UTC 23 March 2016 GFS, valid 1200 UTC 24 March 2016. Credit College of DuPage.

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Figure 2. 2-m theta-E (K) and 10-m winds (kt) for 0000 UTC 23 March 2016 GFS, valid 1800 UTC 24 March 2016. Credit College of DuPage.

 

Several features of this setup are consistent with recent HSLC research of severe events. The narrow plume of low-level high theta-E air stretching from near the Gulf of Mexico northward through Tennessee (Fig. 2) is similar to that found in Jessica King’s high-resolution simulations and contributes to increased CAPE in this area, particularly in the NAM (Fig. 3). Additionally, forecast soundings suggest continuous advection of high theta-E in the low-levels throughout the event (not shown). Coupled with a rapid decrease in theta-E with height and favorable “ball cap”-shaped hodograph (both shown in Fig. 4), the thermodynamic and kinematic setup appear favorable for severe HSLC convection. Though best upper-level forcing for ascent is projected to lift northward away from the area of interest as the event goes on (note location of vorticity maximum in Fig. 5 compared to Fig. 1), other signs point to this being a severe event.

 

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Figure 3. SBCAPE (contoured, J/kg), SBCIN (hatched, J/kg), and 10-m wind (kt) for 0600 UTC 23 March 2016 NAM, valid 2100 UTC 24 March 2016. Credit College of DuPage.

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Figure 4. 0600 UTC 23 March 2016 NAM forecast sounding for northern Alabama valid 2100 UTC 24 March 2016.

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Figure 5. As in Fig. 1, but valid 1800 UTC 24 March 2016.

 

Convection-allowing NCAR ensembles suggest the possibility for rotating updrafts (Fig. 6) within a broken line of convection (Fig. 7). As noted, VORTEX-SE will be operating on this project with its multiple mobile sounding and radar teams, sticknet array, lightning mapping array, and disdrometers, in addition to other fixed instrumentation. More information on the project can be found here.

I plan to write a follow-up blog discussing VORTEX-SE operations during the event following its conclusion. However, this is an important and exciting step in our aims toward improving the understanding and forecasting of HSLC convection, as this (if it verifies) will be the most-sampled HSLC severe event in history.

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Figure 6. 0000 UTC 23 March 2016 NCAR ensemble paintball plot of hourly maximum 2-5 km updraft helicity > 50 m2/s2 valid 2000 UTC 24 March 2016.

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Figure 7. 0000 UTC 23 March 2016 NCAR ensemble paintball plot of 1-km AGL reflectivity > 40 dBZ valid 1900 UTC 24 March 2016.

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NWP Systems Reference Updated for ECMWF Changes

nwp.basic

Snapshot of the basic NWP configuration and setup reference. 

On March 8, the European Centre for Medium-Range Weather Forecasts (ECMWF) upgraded the Integrated Forecast System (IFS) with a significant reduction of the horizontal resolution of the high-resolution (HRES) and ensemble (ENS) forecasts. The upgraded horizontal resolution is now around 9 km for the HRES from the previous 16 km grid spacing. Details on these and other changes to the modeling system related to the implementation of IFS cycle 41r2 is available at the following URL: https://software.ecmwf.int/wiki/display/FCST/Implementation+of+IFS+cycle+41r2

With this significant change, we wanted to share our updated NWP reference that Shawna Cokley from WFO Raleigh maintains. The reference provides details on the run time, number of forecast hours, horizontal grid spacing, vertical levels, and output frequency along with details on how the modeling system handles convection, microphysics, radiation, initial/boundary conditions, date of recent upgrade and more. Links to the full reference as well as a basic overview reference are shown below. If you have any comments or notice any items that need attention, please let us know.

Basic NWP Configuration and Setup Reference

Full NWP Configuration and Setup Reference

 

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CSTAR Project Presentation from the AMS Annual Meeting

In January, Lindsay Blank traveled to the 96th Annual Meeting of the American Meteorological Society in New Orleans to present a talk on her CSTAR HSLC project. This presentation won 2nd place in the oral presentation category in the 6th Conference on Transition of Research to Operations Student Competition. A recording of this presentation is available at the following link:

Blank and Lackmann,”Operational Predictability of Explicit High Shear, Low CAPE Convection”
Presentation

If you have any questions or comments on this presentation, please feel free to address them here or contact Lindsay through email (lrblank@ncsu.edu).

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

Observational Resources for the Potential Severe Weather on Wednesday 24 February 2016

 

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SPC Day 2 categorical and probabilistic outlooks for Wednesday.  

The latest Severe Weather Outlook from the SPC indicates an enhanced risk of severe weather on Wednesday, 24 February, across central and eastern NC with a slight risk across much of the mid and south-Atlantic with a region of significant severe weather possible in the NC Coastal Plain and the Eastern Piedmont. I thought it might be helpful to share some of the new or irregularly available observations data that will likely be available on Wednesday including GOES-14 Super Rapid Scan 1-minute data, the NCEP “Fire Weather Nest” 1.33km high-res nest run model, MESO-SAILS nearly 1-minute radar data, and special upper air soundings.

 

GOES-14 Super Rapid Scan Operations for GOES-R will be centered over the Southeast on 24 February, 2016. Super Rapid Scan Operations will provide 1-minute satellite imagery to support multiple research and GOES-R/S user readiness activities. Additional background information including training and links to online imagery is available at: http://cimss.ssec.wisc.edu/goes/srsor2016/GOES-14_SRSOR.html. Imagery including visible, infrared, and water vapor is available on the web at the links below…

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NCEP Fire Weather Nest domain for the 00 UTC, 06 UTC, and 12 UTC runs on 24 February.

The NCEP “Fire Weather Nest” 1.33km high-res nest model run will be centered over a portion of the severe weather threat area for the 00 UTC, 06 UTC, and 12 UTC runs on 24 February. The Fire Weather Nest will be centered at 35.5N, -79.0W as shown in the image to the right. You can access forecast fields from the 1.33km high-res FWN run at the following URL: http://www.emc.ncep.noaa.gov/mmb/mmbpll/firewx/

 

The Multiple Elevation Scan Option for Supplemental Adaptive Intra-Volume Low-Level Scan (MESO-SAILS) capability for the Doppler radar is being testing at 13 CONUS locations including Raleigh, NC (KRAX) and Morehead City, NC (KMHX) which are both in the severe weather threat area. MESO-SAILS will allow radar operators to add two, three or four low-level elevation scan updates per volume scan which depending on other factors could result in a base radar scan almost every minute which would allow excellent sampling of the low-levels and a unique perspective on the convection.

In addition, several special upper air soundings are anticipated tomorrow. These have been schedule for 15Z at Greensboro (KGSO) and likely a few other NWS locations. Some universities in the area may release soundings with NC State likely to do so and perhaps others from UNC Asheville and possibly UNC Charlotte. Finally, the Simmons Weather group at Fort Bragg and Simmons AAF may release some soundings on Wednesday.

Posted in Convection, High Shear Low Cape Severe Wx, NWP, Satellite | Leave a comment

NWFS Collaboration Group authors “Northwest Flow Snow Aspects of Hurricane Sandy” in Feb. 2016 Weather and Forecasting

Just a short note to let readers know that several of us who have been collaborating on NW Flow Snow issues in the southern Appalachians now for a number of years have had our manuscript on the northwest flow snow associated with the remnants of Hurricane Sandy (Oct 2012) published in Weather and Forecasting. This will appear in the February issue, and for now is available as an early release version to WaF subscribers here:

http://journals.ametsoc.org/doi/pdf/10.1175/WAF-D-15-0069.1

My sincere appreciation goes to all the co-authors for the hard work in putting this together and final modifications leading to publication: Doug Miller, David Hotz, Pat Moore, Baker Perry, Larry Lee (yes, even in retirement!), and Daniel Martin.

We will likely move on to other NWFS topics for awhile, including HiRes model validation for typical NWFS events, but the opportunity for simulating many of the forcing mechanisms and moisture sources associated with the historic Sandy snowfall is something that some of us may still pursue.

Steve K.

 

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GOES-14 will be in Super Rapid Scan Operations with imagery over the Carolina’s and Virginia’s Today (2/3)

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GOES SRSOR visible satellite loop from 1806-1933 UTC on 20 August 2015

GOES-14 Super Rapid Scan Operations for GOES-R (SRSOR) began on 1 February and will continue for through 24 February, 2016. 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/srsor2016/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/srsor2016/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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December 23, 2015 Severe Weather Potential

Contrary to other potential severe high-shear, low-CAPE (HSLC) setups so far this autumn and winter, tomorrow’s setup appears to have the majority of pieces in place. The main story may be the high-CAPE setup during the afternoon and early evening across the Mississippi and Tennessee Valleys, areas encompassed by the Storm Prediction Center’s Day 2 enhanced risk. However, many signs point to a continued threat overnight extending into the Ohio Valley. While this will again occur west of several of our collaborating WFOs, it will likely be an event worth studying.

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Figure 1. Images from 1200 UTC 22 Dec. 2015 GFS, valid 0000 UTC 24 Dec. 2015: (top left) 500 hPa absolute vorticity and geopotential heights, (top right) 850 hPa isotachs (kt), wind barbs, and geopotential heights, (bottom left) 2-m theta-E and 10-m wind barbs, and (bottom right) 0-3 km energy helicity index.

Figure 1, valid at 0000 UTC December 24th, shows a strong, negatively tilted trough across the Midwest with an attendant 850 hPa closed low and intense low-level jet. A baroclinic zone is evident in the 2-m theta-E field across the Midwest and Ozarks, with a warm sector extending into Great Lakes region. The EHI shows a “reservoir” of favorable values extending from the Ohio River southward into the Deep South. Additionally, SREF mean SHERBS3 (Fig. 2, left) and SHERBE (Fig. 2, right) values remain enhanced across the Tennessee and Ohio Valleys from 00z through 06z, suggesting a continued threat of severe weather during the overnight hours.

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Figure 2. SREF ensemble mean SHERBS3 (left) and SHERBE (right) values valid for 0000 UTC 24 Dec. 2015 (top) and 0600 UTC 24 Dec. 2015 (bottom).

Finally, despite fairly modest lapse rates overnight in the Ohio Valley (Fig. 3) compared to those farther south (Fig. 4), hodographs appear favorable for the development of embedded rotation within an evolving QLCS in both locations.

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Figure 3. 1200 UTC 22 Dec. 2015 NAM forecast sounding valid for 0300 UTC 24 Dec. 2015 in central Ohio.

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Figure 4. As in Fig. 3, but for eastern Tennessee.

Though this may not get a lot of comments due to the holidays around the corner, I wanted to post a brief overview due to the heightened threat. This should be quite an event to watch!

 

Posted in CIMMSE, Convection, CSTAR, High Shear Low Cape Severe Wx, Uncategorized | 3 Comments