New Paper Comparing ASOS Near-Surface Winds and WSR-88D-Derived Wind Speeds in Landfalling Tropical Cyclones

Map of ASOS and WSR-88D sites along with tropical cyclone tracks used in the study. 

A new article in Weather and Forecasting by Krupar et al. entitled “A Comparison of ASOS Near-Surface Winds and WSR-88D-Derived Wind Speed Profiles Measured in Landfalling Tropical Cyclones” may be of interest to some collaborators. The researchers made 22 comparisons during landfalling TC events in the Gulf of Mexico to compare low-level WSR-88D wind data with ASOS surface wind and wind gust observations within 10 km of the RDA. The goal was to develop an empirical relationship to relate the TC boundary layer wind to near surface winds. They found that radar based, site-specific linear regression equations using a 0–200-m layer average wind speed can be used to predict the ASOS 10-m standardized mean wind speed while a non-site-specific linear regression model using a VAD 0–500-m mean boundary layer wind can be used to predict ASOS 10-m nonstandardized gust wind speeds.

Posted in TC Inland and Marine Winds, Uncategorized | Leave a comment

GOES-14 will be in Super Rapid Scan Operations Through August 25th


GOES SRSOR visible satellite imagery from 1558 UTC 15 August 2016 in AWIPS

GOES-14 Super Rapid Scan Operations for GOES-R (SRSOR) began on 9 August and will continue for through 25 August 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:  Additional background information including training and links to online imagery is available at:

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 from AWIPS is shown in the image above.

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

Posted in Satellite | 2 Comments

Mesonet Data Captures Impressive Nocturnal Surface Theta-E Rise Immediately Ahead of QLCS EF1 Tornado in Ohio (June 23rd, 2016)

During the nighttime hours of June 22nd/23rd, a cluster of severe thunderstorms expanded (QLCS) as it moved from Indiana into Ohio ahead of a seasonably strong shortwave trough shifting through the Great Lakes.


This cluster of storms had previously been responsible for significant/high-end wind gusts across portions of northern Indiana earlier in the night, evolving within and through the heart of a well-predicted SPC Moderate Risk threat area.  As the line moved into the National Weather Service (NWS) Wilmington, Ohio (WFO ILN) forecast area, rapid line-embedded mesovortex evolution began in northern Warren County and continued across much of Clinton County, moving very close to both the WFO ILN WSR-88D, and a Ohio Department of Transportation Road Weather Information System (RWIS) site.  A 20+ mile EF1 tornado was surveyed beginning near Waynesville, OH, to just south of Wilmington, OH, and included a near-miss of both the WFO and the RWIS site, but allowed for some interesting findings.


Detailed data from the RWIS station was sent to WFO ILN by the ODOT RWIS coordinator, Timothy Boyer, and comes courtesy of ODOT.  This data revealed an anomalous mid-summer nocturnal rise in boundary layer theta-e in the hours preceding the QLCS arrival in Warren/Clinton counties.


As background, in our HSLC CSTAR group, Jessica King presented to us the results of her study of numerical simulations of severe weather environments at night in the Ohio Valley/Southeast. The results of her study of severe vs. non-severe events showed that rapid changes in SBCAPE immediately ahead of the line (within the 1-3 hours previous to severe report) was an excellent discriminator vs shear and cooling aloft.  Below is a screen capture of her results – notice in the severe-vs.non-severe plots how SBCAPE increases dramatically in the hour(s) previous to severe events. In seemingly most (>90%) of her simulations, SBCAPE increased by 200-600 J/kg within 2 hours of the severe event.



Courtesy: Jessica King

Here is another image from Jessica’s research showing the surface theta-e field ahead of an idealized convective boundary from her study of these severe cases.  Notice the narrow plume of significant implied advection in theta-e relative to the convective boundary.

Courtesy: Jessica King

With data from the RWIS, and the timeliness of a 05Z special sounding taken at WFO ILN, augmentation of the 05Z surface conditions to what was in place at 07Z (when the tornado touched down and moved through the area) revealed key thermodynamic changes to the environment occurred in the 2.5 hours between 0430Z sounding launch, and tornadogenesis immediately west of Wilmington.  While it’s easy to get caught up with the fact that the RWIS measured an 80 mph gust (image below) as the tornado passed very close by, the surface temperature/dewpoint trends in the hours prior to the tornado are key and critical.  There is a steady and impressive rise in surface theta-e as measured by the site. This is in the depth of night (3 AM EDT) — in summer — when rises in surface temperature/dewpoint are very difficult in comparison to strong advection regimes typically seen in the cool season QLCS scenario. The fact this advection occurred in late June is  very significant.   From a temperature/dewpoint of 71F/69F at sounding release (balloon actually released at 0430Z) to 76/73 at 07Z when a tornado was on the ground very near the RWIS and sounding location, this well-timed and well-located data provided verification to the simulations observed in Jessica’s work.  This may seem incidental at first look – only a 5F (temperature) and 4F (dewpoint) rise in 3.5 hours – but for nocturnal QLCSs in mid-summer this equates to a rapid change in near-storm environment and threat.



Wilmington RWIS Time Series (Courtesy Timothy Boyer, ODOT)


Using the same SBCAPE/SBCINH computing methods as the 05Z sounding linked via SPC above, augmenting that sounding used the observed surface temperature and dewpoint (subjectively maintaining a similar mixing ratio and temperature lapse rate immediately above the surface), the environment felt by tornadic QLCS near Wilmington featured an SBCAPE rise from 456 (with SBCINH of -269 suggesting elevated storms) to > 2000 J/kg with SBCINH reduction to -25 (suggesting surface based storms).  That’s a huge change in threat/environment over the period of 3 hours — at night.

05Z KILN Special Sounding Augmented With 07Z RWIS Surface Conditions

Granted this event was far from a traditional HSLC event which was the crux of Jessica’s study, but as we’ve seen time and time again with nocturnal QLCS events in the Ohio Valley (and elsewhere) amidst strong low level shear, if your boundary layer theta-e advection is aggressive/strong – warning meteorologists should anticipate resultant increase in impacts via damaging wind and/or mesovortex tornadoes provided ambient low level shear/cold pool balance is optimal.


Below is the evolution of the tornadic circulation via KILN WSR-88D (top images) and FAA Terminal Doppler Weather Radar (TDWR) at Dayton, OH (bottom images) which was surveyed to be a 20+ mile EF1.  There was even very subtle TDS (reduction in correlation coefficient co-located with the SRM velocity couplet) on KILN from Waynesville to just west of WFO ILN before noise/clutter near the radar masks the signal.  For the WSR-88D imagery, upper left quadrant is 0.5 degree reflectivity (with MESO-SAILS 3 invoked), upper right is 0.5 degree SRM.  For the TDWR imagery, the bottom left is 0.3 degree reflectivity, and the bottom right is 0.3 degree SRM.

KILN (top) and Dayton TDWR (bottom) reflectivity and velocity loop

From a wind shear perspective, this event possessed the ingredients seen in other high-impact QLCS nocturnal wind events in the Ohio Valley (and elsewhere), with strong 0-1km effective SRH (owing to a strong west-southwesterly low level jet).

07Z SPC 0-1km Effective SRH (Courtesy SPC and Jonathan Blaes)

Also of interest, is the SPC Mesoanalysis clearly indicating a large area positive nocturnal surface theta-e advection with relative maximum in advection centered very near WFO ILN in southwest Ohio.



07Z SPC Surface Theta E (Green Contours) and Advection (Purple Contours) — Courtesy SPC and Jonathan Blaes

Posted in Uncategorized | 5 Comments

Webinar on the Environmental Conditioning of Cool Season, Low Instability Thunderstorm Environments in the Tennessee and Ohio Valleys and Southeastern U.S.

In late April, Jessica King, presented a summary of much of her CSTAR research simulating severe and non-severe high shear, low CAPE convective events. The presentation focused on the examination of the rapid destabilization that occurs in the few hours leading up to severe convection in the simulated events and the mechanisms responsible for the rapid changes in CAPE. Links to the PowerPoint slides and the recorded webinar are available at the bottom of the post. Some notes from the presentation are shared below.

fig1Low instability severe thunderstorms are heavily concentrated in the Southeast especially in the Ohio, Tennessee, and Mississippi Valleys. These events tend to occur in the cool season, often in the overnight and early morning hours, and frequently with a convective mode of mini-supercells or QLCSs. The occurrence of severe convection in low instability environments can often be explained by the presence of synoptic scale forcing and mid-latitude cyclones. The research goal was to determine mechanisms by which environmental conditioning occurs in severe and non-severe high shear, low CAPE thunderstorm events.

Simulated Environments
fig1.5Jessica conducted real-data simulations of high shear, low CAPE events when there was at least a “slight” risk for severe storms and the SfcOA (SPC mesoanalysis) CAPE ≤ 1000 J kg-1 and 0-3 km shear ≥ 18 m s-1. She developed a 3-hour time series analysis for separate points in a 7×7 grid for the three hours prior to severe convection. The 0-1km wind shear showed some discrimination between severe and non-severe events with values higher in severe events, especially at night. The wind shear tended to remain relatively steady over time while the CAPE increased over time.

Calculating Contributions to CAPE
fig3Advection of high theta-e air often leads to an increase in CAPE. A plot of 3-hour change in SBCAPE up to the event time shows a much larger increase in SBCAPE prior to the event for severe events with a smaller increase for non-events. An increase in CAPE can be realized by 1) increasing surface temperature 2) increasing surface moisture or 3) decreasing temperature aloft. The mechanisms for destabilization varied significantly among all environments with significant destabilization occurring in the 3 hours prior to severe events. The change in surface moisture was a positive contribution to increase in CAPE for all cases. Warming near the surface was important in destabilizing all of the severe events as well, and cooling near the surface may be detrimental in the non-severe events. The increase in surface temperature was noted for both daytime and nocturnal cases.

Synoptic Forcing for Ascent
fig4Forcing for ascent can be driven by processes such as warm advection, lifting by a front or boundary, and cyclonic vorticity advection aloft. These processes can lead to the release of potential instability. The release of potential instability through layer lifting occurred prominently in 4 of the simulated severe events. In these 4 cases, the 3km vertical velocity increases significantly and the 0-3km lapse rate became less negative in the hour before the severe event as the synoptic forcing approaches.

The SHERBS1 and to a lesser extent the SHERBS3 were discriminators between the severe and non-severe events. The skill of the SHERBS1 was likely a result of the 0-1km shear serving as a good differentiator. Work is underway to modify the SHERB parameters to perhaps include a term to account for the release of potential instability.

Future Work and Looking Ahead
• Investigate larger scale observations and climatologies to identify recurring synoptic-to-mesoscale patterns in cool season, low instability events in the Southeast.
• Examine the vertical distribution of CAPE.
• The recognition of patterns in high-resolution model data and observations that indicate a low CAPE environment has the potential to evolve into a severe-weather producing environment.
• The availability of datasets and tools to examine data in the highest temporal resolution possible is critical. In many events, some of the higher resolution data doesn’t show a supportive environment 3 hours in advance of the event but a rapid change in low-level moisture or temperature can occur just ahead of the line that provides the needed buoyancy. Sub-hourly time scales or other perspective may provide an opportunity to anticipate these events.
• There may be an R2O pathway with the near-storm situational awareness environment tool that is under development which provides a means for detailed monitoring of the environment.
• There was also an interest in requesting the SPC produce some 1 or 2 hour change fields for surface temperature and moisture.

PowerPoint slide deck
Video recording of webinar


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

Interesting Findings from Two Fall HSLC Cases (23 Nov. 2014 & 18 Nov. 2015)

CSTAR folks,

We wanted to post a review of several HSLC cases that had some significant operational utility here at FFC to garner further insight, comments, or discussion you may have (included some discussion points at the end).  Both happen to be November events, with the first (23 Nov. 2014) providing a unique outlier to some previous local research, and the second more recent case (18 Nov. 2015) lending to a situation where the SHERBS3 may have been the heaviest hitter of the available predictive severe parameters.


23 Nov. 2014 QLCS Tornadic Event: Persistent Regeneration of Weak Tornadoes with Pronounced Tornado Debris Signatures

  • Poster presentation at 2016 AMS Annual Meeting
  • Coordinated topics/previous research with Jason Deese (FFC), John Banghoff (Ohio State Univ.), Steve Nelson (FFC), and Dr. Gary Lackmann (NC State Univ.)

The tornadic development across central Georgia on the afternoon of 23 Nov. 2014 was not the typical case one would expect in the Southeast U.S. for two reasons:

  1. Persistent northern bowing segment or “broken-S” QLCS convective mode resulting in six separate tornadoes
  2. Pronounced tornadic debris signatures (TDS) seen with five of the six tornadoes, some of which lofted debris to a significant height above the ground more than previously documented with weak tornadoes (Banghoff and Nelson, 2014)

Figure 1. Surveyed event tornadoes and damage points.

The synoptic setup consisted of a negatively titled upper shortwave trough tracking northeastward across the southeast CONUS (Fig. 2) with an attendant low pressure system drawing strong low level Gulf moisture advection (Fig. 3).


Figure 2: 500 mb analysis (2000z)


Figure 3. 850 mb analysis (2000z)

A parent surface high pressure system situated off the mid-Atlantic coast had previously resulted in hybrid cold-air damming (CAD) along the eastern slopes of the Appalachians, and allowed for the periphery of the wedge of cold air or “wedge front” to be present across central Georgia (Fig. 4).


Figure 4. Surface analysis (2000z)

The combination of these influencing features provided a HSLC environment for convective development (Fig. 5).  A special 18z upper air release also came out of TAE and indicated HSLC parameters even away from the wedge influence (Fig. 6).


Figure 5: Instability and shear parameters (2000z)


Figure 6: Special 18z TLH raob instability and shear parameters

Tornadogenesis was observed to consistently occur along the wedge front as it rapidly retreated northeastward across central Georgia ahead of the aforementioned system.



Figure 7: Radar snapshots of 6 tors at time of genesis

Dual-polarization radar data were analyzed for each of the tornadic cells to assess strength of rotation (Vr and NROT) and max TDS heights (used GR2Analyst).


Figure 8: Method of using dual-pol radar data to analyze TDS height


Figure 9: Resultant TDS heights during 6 tornado lifespans


Figure 10: Resultant Vr and NROT values during 6 tornado lifespans

Much of this data were also analyzed during the event in real-time to assist in enhanced wording of the tornado warnings (prior to implementation of Impact-Based Warning (IBW) wording).


Figure 11: Examples of enhanced wording used in real-time warnings

The analyzed TDS heights primarily stayed in a 6-11 kft range, which is more common to the significant EF2 category observed with previous research (Fig. 12).  While the surveyed tornadoes in this event mainly fit in the weak EF0-EF1 categories, it is proposed that such anomalously high TDS heights were due to the presence of abundant fall foliage and lofted leaf debris combined with subsequent tornadic updraft regeneration.


Figure 12: Annotated from Entremont and Lamb, 2013

It is also proposed that the wedge front provided a nearly steady source of low level streamwise vorticity available for tilting into the vertical within the convective updraft as subsequent downdrafts instigated persistent tornadogenesis by bringing vorticity to the surface.  Presence of the front thus compensated for the lack of surface based instability in the HSLC environment and helped focus tornadic development. This serves as an extension to previous research on wedge front influence in conversely low shear high CAPE environments (Fig. 13).


Figure 13: Annotated from Baker and Lackmann, 2009

Trends in observed radar data and associated near-storm environment from this particular case provide unique utility in operations.  The findings not only extend the proposed effect of wedge front influence on convection in HSLC environments, but also present an upper bound of TDS height correlation to tornado strength during the fall season.  This provides aid to awareness and enhanced wording in warning decisions. Warning operators could justify a seasonal adjustment to the threshold for tornado damage threat tags with the newly implemented IBW structure (Fig. 14).


Figure 14: Decision Aid utilizing previous TDS research from Banghoff and Nelson

Since the 2016 AMS Annual Meeting, Keith Sherburn provided some archived SHERBS3 and SHERBE plots near the time of initial tornadogenesis for the case (Fig. 15).


Figure 15: SHERB parameters during tornado lifespans (2000-2200z)

Interestingly, the SHERBS3 parameter captured the threat better than the SHERBE as critical values nosed farther north and east near the storm locations.  The SHERBE actually had an opposite trend in central Georgia as it weakened and diminished in spatial coverage. While SHERBE calculations set the effective shear magnitude to zero where CAPE is absent, it is noted this could miss events where CAPE is under-forecast/diagnosed.  In a rapidly retreating wedge situation, this is more likely to occur, especially if guidance struggles to resolve the strength, timing, and extent of the wedge to begin with.  It’s hypothesized the SHERBS3 has potential to more likely illustrate the favorable environment interacting with the wedge periphery in an HSLC environment.



18 Nov. 2015 QLCS Tornadic Event

A strong upper low pressure system and associated surface front brought a squall line of storms across north and central Georgia during the late afternoon and evening hours of 18 Nov. 2015.  Three tornadoes formed in the northern part of a pronounced bowing segment along the squall line as it tracked across portions of Coweta, Fulton, and DeKalb counties (Fig. 2). The first two tornadoes resulted in EF-1 rated damage, with one near Palmetto and another near Fairburn. The final tornado was a very brief EF-0 in DeKalb County near Tucker (specifics listed below). Some observed TDSs in radar imagery allowed for enhanced wording of the warnings.


Figure 1: Surface analysis


Figure 2: Radar imagery of northern QLCS bowing segment

There were also indications of a lingering wedge front/retreating warm front near the northern notch of the bowing segment, where there were still some ageostrophic roots to a 1030+mb parent high off the NE coast, and perhaps some in-situ reinforcement occurring from upstream solar sheltering seen in the 2000z obs plot below (Fig. 3).  This boundary could have been interacting with the near-storm environment, providing a more steady source of low level streamwise vorticity necessary for tornadogenesis and subsequent regenerations.


Figure 3: Surface analysis and obs


First tornado (Coweta Co. 448 PM EST):

Rating: EF-1
Peak Wind: 105 MPH
Path Length: 0.2 MILES
Path Width: 200 YARDS

Figure 4: Radar imagery of first tor


Figure 5: Surveyed path of first tor

Second tornado (Fulton Co. 459 PM EST):

Rating: EF-1
Peak Wind: 95 MPH
Path Length: 2.6 MILES
Path Width: 200 YARDS

Figure 6: Radar imagery of second tor


Figure 7: Surveyed path of second tor

Third tornado (DeKalb Co. 547 PM EST):

Rating: EF-0
Peak Wind: 75 MPH
Path Length: 0.12 MILES
Path Width: 100 YARDS

Figure 8: Radar imagery of third tor


Figure 9: Surveyed path of third tor

The environmental parameters also fit the bill for HSLC.  Below are reanalysis plots for 0-6 km bulk shear, 0-1km SRH, SBCAPE, SHERBE, and SHERBS3 compared to the SPC storm reports at times near the initial tornado occurrence (2000z and 2100z in Fig. 10 and 11 respectively).


Figure 10: Instability and shear parameters (2000z)


Figure 11: Instability and shear parameters (2100z)

Again, both SHERBE and SHERBS3 have critical threshold values north of the instability axis near the areas of tornadogenesis, and the SHERBS3 had better coverage than the SHERBE.  This still is in support of the SHERBS3 parameter potentially being a greater predictive parameter in retreating wedge front situations with limited CAPE.




Initial discussion thoughts from both case analyses…

  • Did any other office have some notable observations or analysis from either of these past two events (more likely from 23 Nov. 2014 since 18 Nov. 2015 was quite localized)?  Perhaps another event with a similar setup or outcome?
  • Any further insight into the following proposed operational applications:
    • Raising the Fall seasonal threshold for TDS height and enhanced wording correlation for Impact-Based Warnings
    • Influence of wedge front given HSLC environments
    • Potential for SHERBS3 to capture severe threat better than SHERBE in rapidly retreating wedge cases


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

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.

gfsUS_500_avort_036 (1)

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.


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.



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.


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


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.

Screen Shot 2016-03-23 at 8.43.42 AM.png

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.

Screen Shot 2016-03-23 at 8.42.34 AM.png

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

Posted in Uncategorized | 1 Comment

NWP Systems Reference Updated for ECMWF Changes


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:

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


Posted in Uncategorized | 1 Comment