HWT Day 2: Protecting the Quartet

Protect the Quartet!

Today we were charged with the noble task of watching over the the Quartet Festival located in Lawrenceburg TN. Gaps in the cloud coverage allowed us to utilize some of the satellite products a little more efficiently today. Our first sign of trouble came as convection began to form out in front of the main line moving WNW out of Alabama. LightningCast 60-min prob gave us our first initial heads up that lightning was possible with storms forming out ahead of the main line. A combination of Octane overlaid with GLM data was the primary source in our decision making to issue a notification to the event organizers. Thanks to our quick decision making, everyone is alive to sing again another day.

We combined lightning cast and ENTLN data with the radar to provide ground truth on when lighting was first scene within the 15 mile range ring which allowed us to issue follow up messages regarding the likelihood of ongoing lightning potential. Requesting a LightningCast point too also gave us confidence in issuing notifications to the event organizers.

Discussing the LightningCast Probability data with Kilometers we were discussing ways to get more information out of it. We settled on loading the LightningCast as an image rather than contours. This combined with the sample tool and overlayed with Total Lightning products was more useful when forecasting for a specific DSS point. We also went ahead and limited the data being showed on the lower end of the GLM Flash Density. We didn't want to exclude the Flash Density on the lowest end all together, but we wanted to highlight and compare the GLM Flash Density to the areas with the highest Octane SpeedSandwich. Our end result was this GIF below:

Today was a day to dive into GLM and Lightning probabilities. Once we settled on what we wanted to look at to make DSS related decisions, we realized that it wasn't intuitive to the public. We needed a way to redesign the the Lightning Cast data to be easy to look at to the public. Because the NWS already has a color table for threats utilized by our National Centers, we decided to model our threat level based on the SPC's convective outlook to create new colors for the contours. The following graphic is the end product of that:

As the system moved past, identifying areas that we could issue the all clear on was our next priority. The LightningCast created a nice looking bell curve that lined up with the time that the MCS moved over the event and showed the trends of the storm began to wind down.

Missing data

Charmander and Kilometers were watching over an event in central Tennessee and employed the lightning cast meteogram. The probability of lightning tool worked (img. 1) great for alerting the event staff to an increase in the lightning threat, providing about 45 minutes of lead time. 

I began to monitor the cell for further intensification and any chance that it could become severe. In the background of this work I was also monitoring for lightning activity from the cell. Eventually, the cell did produce lightning. Image two showed the ENTLN product pick up on a series of cloud flashes, with the GLM product showing some light lightning activity two minutes later (img. 3).  

Positive for GLM was that the latency was not an issue. What was more of an issue was that the meteogram from lightning cast never plotted the GLM data on the meteogram. If the person working the event shared the meteogram to event organizers, they would assume this was a missed event. Positive though, is that the organizers could be shown the GLM image or ground network data and be assured that their actions were not for nothing. This left us wondering why the meteogram did not show the lightning activity picked up in the vicinity?

We saw that the GLM began showing up when the main line of convection moved through the event space about an hour later than we identified it through alternate means (img. 4).

 

Image one: Meteogram for the Probability of Lightning product with GLM flash Density.

 Image two: GLM Data quality (upper-left), GLM Background Image (upper-right, Day cloud phase RBG overlaid with GLM Flas Density (Bottom-right), ENTLN observed lighting flashes and cloud-to-ground strikes (bottom-right).

 Image three: GLM Data quality (upper-left), GLM Background Image (upper-right), Day cloud phase RBG overlaid with GLM Flas Density (Bottom-right), ENTLN observed lighting flashes and cloud-to-ground strikes (bottom-right). 

 

 Image four: Meteogram for the Probability of Lightning product with GLM flash Density beginning at 15:15 local time.  

 

- Kilometers / Charmander

Convective Initiation Failure

 Watching a New Updraft Among ongoing Convection

Multiple supercell thunderstorms were ongoing across South Texas along and behind a southward moving outflow boundary within a strongly unstable airmass. At 2115Z, a new updraft began to develop near Realitos, TX to the southwest of an ongoing thunderstorm.

Fig 1: Notice the cooling cloud tops in the CTC image (top right) near Realitos, TX at 2114Z. This updraft is evident in the Day Cloud Phase Distinction RGB and Visible imagery.

About 5 minutes later, the cloud top cooling peaks near Realitos. The first faint radar echo become evident to the southwest of the ongoing supercell.

Fig 2: Cloud top cooling peaks at 2119Z near Realitos. The first weak radar echo is evident to the southwest of the ongoing supercell.

At 2127Z, the cloud top cooling product indicates that cooling has significantly decreased. Meanwhile the cloud top divergence product suggests little to no meaningful divergence is occurring. This suggests that the updraft has weakened and will not likely continue to develop. The latest CRP 0.3 degree reflectivity shows an intensification of the precipitation in this area, but the satellite derived imagery suggests that this intensification on radar is temporary and the updraft will continue to weaken.

Fig 3: Cloud top cooling has decreased and no notable cloud top divergence is observed. There is still considerable "texture" in the visible and daytime RGB. Notice the increase in reflectivity to the south of the ongoing thunderstorms.

The information from the derived products suggest that this updraft will likely not develop into an additional thunderstorm near the outflow boundary. There were several minutes of lead time over radar/visible imagery gained from these derived products to indicate that the updraft would not develop fully into a new thunderstorm. An animation of the updraft sequence is shown below.

wthrman

 

 

Octane Trying with Confirmed Tornado within QLCS

Day 1:

    A NE-to-SW line of storms approaching the southern Texas/Louisiana border from the west with another W-to-E oriented line of scattered storms developing along a stationary front. The eastward moving storms starting to bow out with notch in the line starting to develop near the town of Starks, LA. Low-level rotation starting to show on SRV with a weak TDS showing up between 2115-2117Z and a stronger TDS at 2130Z. Radar starting to show what looks to be an embedded supercell within the line and several mesovortices beginning to develop just offshore along the southern half of the line. 

  2117Z

 

2130Z

        Leading up to the development of the tornado, the Octane speed product indicated a decent speed decrease on the upshear side of the storm before tornadogenesis. The Octane speed product also showed higher speeds wrapping slightly back to the west just to the north of the main updraft. The Octane direction product also showed an interesting appendage developing just to the east of the speed min at the same time.   

 

 

 

        As the storm cycled, and new updraft and meso developed, another speed min and direction changed was noted. The two products again showed higher speeds bending back to the west and the northern side of the updraft and another appendage developing on the direction product. While this storm did not produce a tornado, strong wind gusts of 55-60 mph and damage was reported.

 

 

 

 

- Vera Mae

Getting in Shape

Two aspects for what constitutes operational relevance jump to mind when discussing radar imagery. The first is the shape and the second is the intensity. In the image below a line of storms is moving through central Tennessee. The GREMLIN emulated radar is doing a fine job at showing the location of the convection. Where it is still lacking some usefulness to warning operations is not having high enough DbZ returns. Even so, between the two aspects, I believe GREMLIN is resolving the more operationally useful aspect because we can use the prob-severe tool to infer strength and warn on the meso-scale analysis.

 

Image one: GREMLIN Emulated Radar on the left and the MRMS composite reflectivity on the right.

Image two: GREMLIN Emulated Radar on the left and the MRMS composite reflectivity on the right later in the event.

-Kilometers

Lake Charles Radar Confirmed Tornado

 An MCS resulted in a number of TDS and TVS signatures on radar near Lake Charles today. 

This one was capture to the WNW of Sulphur LA as an MCS surged east in an atmosphere that had 5000J/KG of SBCAPE. In addition to a TDS a LSR was submitted to the Lake Charles office regarding significant damage to the Walmart in Sulphur downstream of where these stills were taken. Radar was primarily used to determine that a tornado was on the ground. Looking at some of the Octane data, it was noted that this tornado formed on the leading edge of a speed minimum on the EMESO-1 Octane Speed Display. 

As the storm moved toward Lake Charles, the line segment began to bow out. Numerous reports of wind damage came in with an Semi being flipped on I-10 and a 60MPH wind gust reported by the Lake Charles ASOS. Velocity data showed a strong signal for damaging winds, and the Octane Speed Sat Display again gave us a significant gradient between speeds as the storm passed over Lake Charles. This data could be useful in verifying the potential for damaging winds, especially when storms are close to the radar. 

The Octane Sandwich display seems to be an upgrade to the Day Cloud Phase Distinction although both displays could serve different purposes, with Day Cloud being useful in watching storms develop, while Octane is useful once storms become more organized in identifying more distinct elements of the storm. 

-Charmander

Gremlins are dismantling the nebula!

 Hi everyone! 

First blog post for the Satellite Convective Applications Experiment - Week 1, let's go!

The loop below shows an example of this from the Corpus Christi, Texas. Notice the convection moving out of the frame to the northeast is bounded by prob-lightning contours (Gif 1). My desire would be to have these better matched to the storms. Right now, the contours are too nebulous.

GIF one: MRMS reflectivity at -10 C overlaid with lightning cast 60-min probability. 

Why do I care about it's nebulousness? When I am providing decision support to an event, I want to know which cell is driving the highest probability, which is building and be able to anticipate the lightning threat based on the cells movement. 

As my partner in the testbed pointed out, the anvil(s) (see image one below) were merging and this was likely causing the nebulousness. 

   Image one: GOES East Day Cloud Phase RBG channel.

Our discussion began to expand to others in the testbed and an idea emerged to try and reduce the nebulousness. The idea was to use the GREMLIN Radar Emulation product to further train the lightning cast dataset so that the probabilities become anchored by the emulated MRMS product. 

Below is a GIF of the GREMLIN and MRMS product. With the GREMLIN product using some of the same satellite features as the lightning cast; the two products have some base level of compatibility. And so my challenge to the developers of these products is, an these two be combined such that lightning cast is mapped to the convective feature causing the probability. 

GIF Two: GREMLIN Emulated Radar on the left, and MRMS composite reflectivity on the right.

-Kilometers

Beginning of the 2024 Satellite Convective Applications Experiment

The time has come! Six months of planning and the 2024 Convective Applications Experiment begins at NOAA's Hazardous Weather Testbed in Norman, Oklahoma. Sixteen NWS forecasters will get to demonstrate five experimental products in live and archived severe weather scenarios to improve NWS severe convective warnings, impact-based decisions support services (IDSS), and enhance the transition of new technologies into operations. The schedule is as follows:

• Week 1: 13-17 May, In-Person
• Week 2: 20-24 May, In-Person
• Week 3: 3-7 June, Virtual

Five products headline the testbed this year, with a mix of applications that covers mesoanalysis, convective initiation, warning issuance, IDSS support, machine learning, and even mesoscale modeling. The products are as follows:

• GLM Background and Data Quality Product
• GREMLIN (GOES Radar Estimation via Machine Learning to Inform NWP)
• OCTANE (Speed, Direction, Cloud-Top Cooling and Divergence)
• Polar Hyperspectral Soundings with Microwave and ABI data (PHS) Model
• NOAA/CIMSS ProbSevere LightningCast

Each product will have its own tag, so you can follow along with each product (GLM-DQP, GREMLIN, OCTANE, PHS, and LightningCast) or the entire experiment at HWT2024!

Lastly WDTD is hosting R2O O2R Tales (ROOTs) webinars, formerly known as Tales from the Testbed, featuring testbed forecasters on May 17th and 24th at 11am CDT. Those interested may register here (Note: You must submit the form multiple times to register for multiple webinars).

Thank you all, and happy forecasting!

-Kevin Thiel, SPC/HWT Satellite Liaison

Cold front on the Plains

A potent cold front swept through the Great Plains in late April, spawning severe storms, including supercells, producing large hail, severe wind gusts, and tornadoes. 

Figure 1: Storm Prediction Center local storm reports from 12Z on 30 April to 12Z on 1 May 2024.

ProbSevere LightningCast was able to pick out developing convection along and ahead of the cold front, shown by regions of enhanced probabilities---first in eastern Nebraska, and then later in Kansas and Oklahoma. Toggle back and forth in time in the animation below to investigate model lead time to the first GLM flashes in different cells.

LightningCast is being evaluated at the HWT this spring, with some new features including:

• better probability calibration (as a result of more training data)
• static and on-demand lightning dashboards
• GOES-West version trained on only GOES-18 data
• an additional output product, the probability of ≥ 10 flashes in the next 60 minutes

The lightning dashboards are available from the LightningCast webpage for static locations such as airports and football stadiums, as well as dynamically changing locations like active wild-land fires.

The panel above shows some time series of LightningCast probabilities for the 5-min CONUS sector (red) and 1-min mesoscale sector (yellow) for Wichita Mid-Continent Airport, as storms developed and traveled over the airport. Blue dots are GLM centroid observations within 5 miles (large dots) and 10 miles (small dots) of the airport. 

A new feature being evaluated this year at HWT is the on-demand dashboard capability, whereby a NOAA user can submit location and timing information for an event that they want a dashboard for. They simply fill out this form and receive an automated email with the valid link: https://go.wisc.edu/x16m56. In this way, forecasters can get custom guidance for locations they are serving with decision support. This capability has already been used for events such as NFL games and state fairs.

Below is output from ProbSevere IntenseStormNet, which is a deep-learning model like LightningCast, but uses images of GOES-R ABI and GLM data to predict the probability of "intense" convection, from a satellite perspective. It is useful as storms are maturing. 

From the animation above, one can see how strong overshooting tops, bubbly-like texture in the cloud tops, and above-anvil cirrus plumes correspond well with stronger probabilities, which correlate well with local storm reports. IntenseStormNet works well for deep convection, day and night. Output from this model is used in ProbSevere v3, but can also be useful stand-alone severe-weather guidance in regions without radar coverage.