Thoughts on 11 November 2015 HSLC severe event in Midwest


Figure 1. Verification of SPC’s Day 1 outlooks for 11 November 2015, from earliest (bottom) to latest (top). Credit Dr. James Correia.

On November 11, 2015, a generally well-forecast (Figure 1) high-shear, low-to-moderate CAPE severe event affected portions of the Midwest. Convection initially developed during the late morning in the vicinity of the triple point of an intense surface cyclone across northeastern Kansas and southeastern Nebraska, with some discrete supercells noted early in the event. Over time, convection congealed into a QLCS with embedded supercellular elements as it raced eastward towards the Great Lakes, producing isolated tornadoes and damaging straight-line winds through much of Iowa, northern Missouri, and northwestern Illinois. After dark, convection gradually weakened below severe limits, with the last report of wind-related damage coming just after 8:30 PM in north central Illinois.


Figure 2. Surface chart from 1900 UTC 11 November 2015. Note a surface cyclone center in southeast Nebraska, a warm front extending into Iowa, a dryline from eastern Kansas through central Oklahoma, and a cold front from central Kansas through the Texas and Oklahoma panhandles. Image courtesy of UCAR.

Aside from one unique feature (a dryline, which can be seen in the surface observations of Figure 2), this setup was very similar to HSLC events across the Southeast and Ohio Valley. Forcing was intense through the depth of the troposphere, with a potent surface cyclone, low-level jet, upstream mid-level vorticity maximum, and upper-level jet streak all present. Additionally, SHERBS3 values were elevated across most of the warm sector, extending from southeast Nebraska and southern Iowa southward through Texas (Figure 3).


Figure 3. SPC mesoanalysis SHERBS3 values valid at 2000 UTC, approximately the time of first tornado occurrence in western Iowa. Click image for better resolution.

This case could be dissected in several ways, but I wanted to address a few key points that came to mind while watching this event unfold and in the hours after.

First, the SHERBS3, by itself, showed a very large false alarm area across locations where convection struggled to get organized, particularly across the Ozarks. The convection ultimately attaining severe strength developed and persisted in an environment with both favorable SHERBS3 values and intense forcing. Differential divergence, the 300 hPa analysis, and 700-400 hPa differential vorticity advection from the SPC mesoanalysis are shown in Figures 4, 5, and 6, respectively, to illustrate my point.


Figure 4. SPC mesoanalysis differential divergence valid at 2000 UTC. Click image for better resolution.


Figure 5. SPC mesoanalysis 300 hPa analysis valid at 2000 UTC. Click image for better resolution.


Figure 6. SPC mesoanalysis 700-400 hPa differential vorticity advection valid at 2000 UTC. Click image for better resolution.

Second, as forcing (particularly low-level convergence; see Fig. 7) began to wane after dark and the line began to out race the favorable environment (Figs. 8 and 9), convection quickly diminished in intensity. The line was likely sensitive to the fact that favorable forcing and thermodynamics were becoming displaced with time; I suspect this was ultimately the result of the system’s demise, rather than simply losing surface-based instability.


Figure 7. SPC mesoanalysis differential divergence valid at 0300 UTC, approximately half an hour after the final severe wind report. Click image for better resolution.


Figure 8. SPC mesoanalysis SHERBS3 valid at 0300 UTC. Note that the convective line is largely east of the SHERBS3 bullseye (cf. Fig. 8) and approaching values of SHERBS3 < 1. Click image for better resolution.


Figure 9. SPC mesoanalysis 0-3 km CAPE (red contours) and surface vorticity (blue contours) valid at 0300 UTC. Note that the convective line is largely east of the analyzed 0-3 km CAPE bullseye.

Finally, a sounding launched from DVN approximately one hour before the convective line arrived was not all that impressive (Fig. 10). This brings to mind a few considerations; either a) the environment was evolving extremely rapidly ahead of the line, b) given the intense system kinematics, only very weak convection was necessary to mix down significantly severe winds, or c) the sounding is unrepresentative of the local environment given its horizontal displacement after launch (as suggested by Jessica King this morning during a conversation about the event).


Figure 10. 0000 UTC DVN sounding from the SPC. Click image for better resolution.

All of these are plausible. Jessica’s simulations have revealed rapid destabilization occurring prior to the arrival of HSLC convective lines. Further, areas upstream (e.g., eastern Kansas/northwestern Missouri) were reporting near-severe winds with showers early in the event. Additionally, given the strong winds throughout the profile, DVN’s 0000 UTC sounding was likely in central or eastern Wisconsin by the end of its ascent.

I will leave potential (idealistic) ways to address all of these possibilities in future events for further discussion. For now, please share your thoughts on this recent event!

Posted in Convection, CSTAR, High Shear Low Cape Severe Wx | 5 Comments

CIMMSE Collaborators Participate in the VORTEX Southeast Project


National Severe Storms Laboratory truck used during a previous field experiment.

This week, several CIMMSE collaborators travelled to Huntsville, Alabama, for the first VORTEX-SE Workshop. The Verification of the Origins of Rotation in Tornadoes EXperiment-Southeast (VORTEX-SE) is a research program to understand how environmental factors characteristic of the southeastern United States affect the formation, intensity, structure, and path of tornadoes in this region. VORTEX-SE will also determine the best methods for communicating forecast uncertainty related to these events to the public, and evaluate public response. In many ways, VORTEX-SE represents a new approach to tornado research in general. The goal of the workshop is to produce a road-map showing specific research projects in the physical and social sciences that could be undertaken in the next few years, as well as the mechanisms for transferring knowledge to operations and applications.

Later this spring in March and April 2016, the first field observing campaign of VORTEX-SE will be held. The current concept is to operate during 4-5 periods of several days each, observing the growth of instability and shear in the atmosphere and the eventual thunderstorm activity, with any associated tornadoes, accompanying the passage of large-scale weather systems. The focus in this campaign will be on the boundary layer evolution during these events.

You can learn more about the VORTEX Southeast Project including topics & impacts, supported research, and the schedule of events at…

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An Examination of Preliminary Local Storm Reports during the Historic South Carolina Rainfall Event September 30th, 2015 – October 6th, 2015

1. Introduction

During the historic South Carolina rainfall event of September 30th, 2015 to October 6th, 2015, National Weather Service (NWS) offices at Greenville-Spartanburg (GSP), Columbia (CAE), Charleston (CHS), and Wilmington (ILM) issued a combined 550 Preliminary Local Storm Reports (LSRs) for the South Carolina Counties within their County Warning Areas (CWAs) (Fig. 1). The large scale of this event resulted in at least one LSR for 33 of the 46 South Carolina counties. These LSRs documented nine precipitation and non-precipitation event types from 24 verification sources. This examination will rank the verification sources for all event types and for flood related event types for events that occurred in South Carolina.


Fig. 1. NWSChat Local Storm Report App for GSP, CAE, CHS, and ILM September 30th, 2015 – October 6th, 2015.

2. Data Analysis

A dataset of the LSRs was obtained and exported in spreadsheet format using the NWSChat Local Storm Report App for GSP, CAE, CHS, and ILM for September 30th, 2015 through October 6th, 2015. The LSRs were filtered to exclude reports from North Carolina and Georgia. This process limited the dataset to LSRs from South Carolina counties, documenting coastal flood, flash flood, flood, heavy rain, high astronomical tides, marine thunderstorm winds, non-thunderstorm wind damage, thunderstorm wind damage, and thunderstorm wind gust. Flood events were limited to LSRs that documented coastal flood, flash flood, flood, and high astronomical tides.

LSRs were provided by 24 verification sources. A few sources were combined to simplify data analysis, reducing the verification sources to 18. The following is a list of the simplified verification sources: 911 call center, broadcast media/media, CoCoRaHS, co-op observer, county official, department of highways, emergency management, fire department/rescue, law enforcement, mesonet, NWS employee, NWS storm survey, official NWS observation/ASOS, other federal/Coast Guard, public, social media, tide gage, and trained spotter/HAM.

3. Results

A comparison of the contributions of verification source for all events and for flood related events is illustrated with a Doughnut graph (fig.2).

Fig. 2. Doughnut graph of percent of reports provided from all events (inner circle) and flood events (outer circle). Note: The legend list from top to bottom corresponds to the graph clockwise, starting at the 12 o’clock position.

Fig. 2. Doughnut graph of percent of reports provided from all events (inner circle) and flood events (outer circle). Note: The legend list from top to bottom corresponds to the graph clockwise, starting at the 12 o’clock position.

A. All Events

Five verification sources provided nearly 75 percent of the 550 precipitation and non-precipitation related LSRs during this historic event (Table 1). The five sources that provided the most reports were law enforcement, emergency management, public, 911 call center, and NWS employee. Law enforcement was the leading verification source, reporting 46 percent of all events.

B. Flood Related Events

Five verification sources provided 80 percent of the 371 flood related LSRs during this historic event (Table 2). The five sources that provided the most reports were law enforcement, emergency management, public, 911 call center, and broadcast media/media. Similar to all events, law enforcement was the leading verification source, reporting 42 percent of reports of flooding. It is interesting to observe that law enforcement cited LSRs outnumbered LSRs from traditional sources (trained spotters and HAMs) by a ratio of 17:1.

Table 1. Percentage, total number, and ratio of reports provided by verification sources for all event types.

Table 1. Percentage, total number, and ratio of reports provided by verification sources for all event types.

Table 2. Percentage, total number, and ratio of reports provided by verification sources for flood events.

Table 2. Percentage, total number, and ratio of reports provided by verification sources for flood events.

4. Summary

Law enforcement provided information that was used in 46 percent of all event LSRs and 42 percent of flood related LSRs during this historic South Carolina rainfall event. The text of the LSRs using law enforcement as the information source indicates that 90% to 95% of these reports are from the South Carolina Highway Patrol (SCHP). The SCHP lists the real-time location, type, and time of traffic related incidents on the South Carolina Department of Public Safety (SCDPS) Web site for the seven troops serving the state.

In the summer of 2011, Mike Jackson and Neil Dixon at NWS GSP, created a script called the SC Highway Patrol Collective (SCHPC). The SCHPC collects reports off the SCDPS Web page that contain keywords (roadway flooding, tree on roadway, closed roads, etc.) and stores them in a 45 day archive. The original script was shared with NWS CAE, CHS, and ILM in the spring of 2014. In the summer of 2015, an updated version of the SCHPC was created by Justin Lane, NWS GSP (fig 3).

Fig. 3. Screen capture of the second version of the SC Highway Patrol Collective.

Fig. 3. Screen capture of the second version of the SC Highway Patrol Collective.

It is likely that the use of the SCHPC, leveraging a human/machine mix, made the collection and dissemination of storm reports more efficient and convenient to the NWS meteorologists. These reports are especially useful during nighttime hours, across rural areas, and locations were emergency managers/911 centers are extremely busy. As a result, the rich supply of real-time information collected by the SCHPC aided in the creation of more informative and timely NWS statements, warnings, and LSRs.

Posted in General Information, Hydrology | Tagged , | 2 Comments

Using MRMS rainfall estimates at ILM

A minor flooding event this morning (Nov 3, 2015) in the Wilmington, NC forecast area was the first time I utilized MRMS (Multi-Radar Multi-Sensor) data operationally.

Sustained isentropic lift across a stalled front over eastern Georgia led to widespread moderate rain during the night of November 2 into the morning of November 3.  Widespread 2 to 4 inch rainfall amounts were reported by gauges across Brunswick and Horry counties.  A CoCoRaHS observer from station SC-HR-75 seven miles north of Myrtle Beach reported 6.50 inches of rain, the highest total in the region.

This was a warm rain/coalescence-dominated event, and legacy Storm-Total Precipitation from the KLTX radar underestimated by 50% versus gauge data.  That error plus beam blockage made the product virtually unusable.  ILM forecasters have been dealing with radar beam blockage over the past several years due to a large and growing pine plantation near our NEXRAD radar site in Shallotte, NC.  Dual-Pol precipitation estimates were closer to gauge totals but still suffered from beam blockage over the highly populated regions of coastal Brunswick, Horry and Georgetown counties.

MRMS precipitation estimates with gauge-bias correction was outstanding, particularly when verified against some of the higher CoCoRaHS totals we had in Brunswick and Horry counties.  MRMS is already proving itself to be an excellent new tool both in terms of data accuracy and removing beam blockage artifacts.



MRMS rainfall estimates

Location        Gauge    MRMS    Difference
Wilmington       2.19    2.03      -7%
N. Myrtle Beach  2.30    2.70     +17%
Lumberton        1.09    1.28     +17%
Florence         0.46    0.49      +7%

Southport 5.9W   1.98    1.84      -7%
Varnamtown 1.3SW 2.23    2.24       0%
Calabash 1.2NW   3.86    3.59      +7%
Conway 5 SSE     3.10    3.28      +6%
Conway 6.2 E     4.08    3.83      -6%

Tim Armstrong       NWS Wilmington, NC

Posted in Hydrology | 4 Comments

SREF-SHERB upgrades, and a reminder about HSLC event feedback form

Item 1:

The SREF ensemble members have recently been updated (thanks to Jonathan Blaes for bringing this to my attention).  The upgrades include the following:

– The seven Weather Research and Forecast (WRF) Nonhydrostatic Mesoscale Model (NMM) members will be eliminated.  This includes the following members: ctl, n1, p1, n2, p2, n3, p3.

– The Nonhydrostatic Multiscale Model on B-Grid (NMMB) model members will be increased from 7 to 13 members. The new NMMB members will be: n4, p4, n5, p5, n6, p6.

– The Advanced Research WRF (WRF-ARW) members will also be increased from 7 to 13 members. The new ARW members will be n4, p4, n5, p5, n6, p6.

You may have noticed that these upgrades “broke” the SREF-SHERB plots that are hosted at:

I believe I have fully updated the file management and plotting scripts and that  the updated SREF is now fully represented in our graphics.  Please do monitor and report any issues that you encounter.

Item 2:

With the HSLC season ramping up (and in light of recent inquiries) it is a good time to remind all NOAA partners that we are very interested in your feedback on how various sources of guidance are performing during HSLC events (and nulls or close-call events too).

As a reminder, the “home base” for HSLC resources is:

And, the post-event feedback form is:

We sincerely appreciate your contributions and commentary.  This is an important aspect of the assessment that needs to happen as a part of our CSTAR program!

Posted in High Shear Low Cape Severe Wx | Tagged | Leave a comment

RAH’s Use of NASA SPoRT LIS Relative Soil Moisture Product During the 1-5 October 2015 Carolina Rain Event


WPC 3-day QPF forecast valid 00 UTC 01 October through 00 UTC 04 October, 2015.

In late September, a slow moving upper-level low pressure system was forecast to drop into the Southeast and migrate across the eastern Gulf States. In addition, Hurricane Joaquin was over the Bahamas and was, for a time, forecast to lift north along the Atlantic seaboard with heavy rain likely impacting the eastern Carolinas. The QPF forecast evolved from focusing near Joaquin’s forecast track near the coast to further inland as it became clearer that the upper-level  low and not the hurricane would be the driving force behind the precipitation.  At one point, the forecast for most of North Carolina, including almost all of WFO Raleigh’s (RAH) area, was for rainfall to exceed 6 inches (right).

Even through central NC had been slowly edging back into more severe drought conditions and streamflows were quite low, a forecast of 6 inches of rain was alarming, and a flood watch was issued for all of RAH’s forecast area. In addition, contingency forecasts from the Meteorological Model Ensemble Forecast System (MMEFS) predicted as much as an 80 percent chance of moderate or greater flooding for many of RAH’s river flood forecast points.

NASA SPoRT 0-200 cm Relative Soil Moisture product from 12 UTC 29 September 2015.

NASA SPoRT 0-200 cm Relative Soil Moisture product from 12 UTC 29 September 2015.

NASA SPoRT has developed a real-time configuration of the NASA Land Information System (LIS) that runs over much of the central and eastern United States at 3-km grid spacing.  The 0-200 cm relative soil moisture product from the LIS leading into the event (right) depicted very dry soil conditions with a majority of the area with only 20-25 percent saturation. This was a consideration when river flood warnings were issued, as while the total amount of forecast rainfall was impressive, the event was going to be spread mainly over a 48 hour (10/1-3) time window, which would allow the very dry subsoils to effectively buffer the infiltrating rainfall.


Analyzed rainfall amounts for the period from 01 through 05 October, 2015.

Total rainfall from the event generally ranged from 3 to 5 inches (right), with both the amount and coverage of the precipitation occurring just under critical thresholds to avoid significant flooding issues. A number of flood warnings and advisories were issued, with the impact and damage relatively limited to travel inconvenience. There were 5 river forecast points which exceeded minor flood stage, with none reaching moderate flood stage.

The rainfall’s long duration allowed the bulk of the rain to infiltrate deeply rather than run off, which provided major benefits for late season agriculture, both for harvest and soil preparation for winter crop planting.  The 0-200 cm relative soil moisture recharge was the most dramatic we have seen here at RAH to date (below), with post-storm percentages rebounding to 35 to 55 percent of capacity.


Comparison of NASA SPoRT 0-200 cm Relative Soil Moisture product from 12 UTC 29 September with 00 UTC 06 October, 2015.

In addition, public water supply reservoirs rose to target pools and the U.S. Drought Monitor removed all drought conditions from the Tar Heel state for the first time since the beginning of summer.


Comparison of the Drought Monitor from 29 September with 06 October, 2015.

Posted in Hydrology | 1 Comment

October 2015 CSTAR High-Shear Low-CAPE Conference Call – Presentation from Jason Schaumann on QLCS Tornado Warning Research


The Three Ingredients Method as described in Schaumann and Przybylinski 2012.

Our October CSTAR call featured a guest presentation from Jason Schaumann, Lead Forecaster from the NWS Springfield, MO office, who shared work that he and other Central Region colleagues have been conducting on QLCS tornado warning strategies. The presentation focused on the introduction of the three ingredients method for anticipating mesovortex genesis and rapid intensification, statistical findings from a 2013 Hollings Scholar study, both warm and cold season examples of the operational application of the technique, along with radar features/mesoscale parameters which indicate an increased likelihood for tornadoes.

A recording of the presentation is available at…
A copy of the slide deck is available at…


Using the three ingredients method as a foundation, we have identified additional radar features and mesoscale parameters which indicate an increased likelihood for tornadoes

Some additional background on the project and reference information is available below…
The 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 and Southern Region offices. The first presentation covers the three ingredients method while the second presentation covers radar and warning strategies.

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