LBF HWT Blog Day 4

 We didn’t have too many storms occur during operations today, but that allowed us to be able to focus more on CI. 

LightningCast for CI

Was able to use LightningCast for convective initiation today as LBF was waiting for storms to fire back up for the afternoon and evening. Initially we were thinking storms would form first over the southern portion of the CWA based off of modeled convective parameters but at 2101Z, a 25% chance of lightning popped up via LC for the north-central portion of the forecast area. This 25% contour appeared a few minutes before radar reflectivity started showing up for the same area. Seeing even the 10% contour show up earlier on, clued me into the fact that we needed to shift our focus further north than we originally thought. These storms seemed to be forming along a shear gradient and weak boundary.

Of note, I am using the parallax corrected LC.

LC, GLM FED, and DCPD at 2100Z

LBF radar at 2109Z

By 2116Z, both GLM and ENTLN showed the first flash of lightning, allowing for around 15 minutes of lead time off of the 25% contour.

For comparison, these storms were forming ahead of the highest PHS CAPE and ahead of any of its stronger gradients.

21Z:

22Z:

As our day was winding down, LC continued to indicate areas to watch before it showed up on radar, but I did not grab additional images.

NUCAPS:

Tried to compare NUCAPS soundings today as we did have an overlap, but unfortunately ran into technical issues within my CAVE so was not able to do much with it. Another limiting factor was that the only “green” soundings from Aqua within our CWA fell within the far western scans which we were told by one of the developers they would next expect good data from, being on the limb. But for comparison, here are Aqua (1911Z) and NOAA-20 (1953Z) sounding from points NW of North Platte.

Points selected were both NW of the town of North Platte, circled below. The NE point of the two is Aqua and SW point is NOAA-20

- Matador

GLM FED vs ENTLN | ProbSvr on Pulse High Plains Convection | LightningCast DSS

 GLM FED vs ENTLN → Impacts on ProbSevere??

Spreading anvils from strong to severe storms over far southeastern CO east of Trinidad, likely caused an obscuration of lightning activity into the GLM product. The ENTLN ground network picked up a strong spike in cloud flashes associated with this cell SW of Kim, CO going up from ~150 to ~350 in ~5minutes. Whereas the GLM FED from both GOES-16 and GOES-17 only showed a few flashes observed. Could this be from both GOES satellites having an obscured view of the updraft? Image 2 below shows the anvils spreading in nearly all directions, or far enough in all directions to obscure the light emanating from lightning flashes within the updraft.

GLM GOES-16 vs ENTLN near Kim, CO at 2020Z

GOES-16 Day-Cloud-Phase Distinction RGB - Anvils spreading in all directions from convective updraft core.

Did this lightning obscuration impact the readout from the ProbSevere v3 model? Image 3 below shows a drastic difference in ProbSevere at the 2020Z timeframe of the Kim, CO storm, 29% on version 3 compared to 72% on version 2. More specifically, ProbHail on version 3 was only at 14%. There are other possible causes to this low percentage, notably a low EBShear value of 19kts, and low 715 j/kg CAPE within the -10C to -30C hail growth zone. So while low GLM values may not have had a large weight on bringing down the ProbHail percentage, other unimpressive model or mesoanalysis values may have played the bigger role. The high sun angle and the brightness of surrounding cirrus anvils may have also contributed to the lower GLM FED values. GLM FED from both GOES-16 and GOES-17 were observed to pick up on increased lightning activity more easily later in the afternoon.

These factors went opposite of what radar interrogation yielded for this storm, which included a tall convective updraft with 40+dBZ well above 30,000’ at storm top, and MESH reaching to or just above 1.00” during the 2015Z-2025Z timeframe.

ProbSevere v3 Low ProbSevere and low ProbHail for severe warned storm SW of Kim.

 

Optical flow winds in the image below picked up on strong storm top divergence from severe warned storms just east of Raton, NM. This coincided well with observed storm top divergence signatures seen from the PUX radar velocity product in the second image below.

Optical Flow Winds | 50-70kts southerly wind barbs evident on cell near Raton, NM

Radar Velocity signature showing storm-top divergence of 85-95kts.

The PUB WFO had an example DSS event in Trinidad, CO, the Santa Fe Trail Days event which had events going on all day. The threat of lightning impacting the outdoor event, and the threat of severe weather was the main area of concern. There was already ongoing convection in the area at the start of the day’s trial run, so a nowcast graphic was produced utilizing LightningCast to show where the highest threat of lightning was. Coupled with an underlying satellite image, a brief forecast over the next hour showing storm motion and what the continued threat of lightning was going to be was also included. The display of LightningCast in percentage was an easy way to display the lightning risk. An ad-hoc Low/Slight/Moderate/High description of each threat tier was added in, but in no way reflects a sound or thorough best practice for a description of lightning risk.

DSS Graphic using LightningCast to showcase the risk of cloud-to-ground lightning at the hypothetical Santa Fe Trail Days Event in Trinidad, CO.

After the short-fuse nowcast graphic was sent, a longer fuse DSS graphic was issued to give a sense of the lightning risk will be through the rest of the day. For this, the PHS Sfc CAPE field was used to display the potential thunderstorm strengths. This would likely not be used in an actual DSS event, given the lack of understanding the intended audience would have of surface based CAPE and instability. But it does highlight the potential use if communicated properly.

Second longer fuse DSS graphicast showcasing the days thunderstorm risk for the Santa Fe Trail Days at Trinidad, CO.

A third DSS graphicast was issued later in the afternoon highlighting the progression of storms toward the ESE away from Trinidad, CO. The message focused on their still being a cloud-to-ground lightning risk in the area of Trinidad, via display of LightningCast, but a lowering risk moving in from the west. Further messaging of the expected end time of the lightning risk was also conveyed in this graphic.

Third short-fuse DSS graphicast showcasing current MRMS radar overlaid by LightningCast

- TRIP

Differences in Prob Severe v2 vs v3

Some significant differences in probabilities for v2 vs v3. Noted on this storm in northern New Mexico. Not quite sure the reasoning for this large discrepancy. 

Storm ID: 346478 in Northern New Mexico June 9, 2022.

Notable Differences in ProbSevere in the time series.

Storms going up right along forecasted boundary from PHS CAPE

Storms developing in Prowers County in southeastern Colorado.

- David Spritz

Lightning and Severe threats in North Carolina

The forecasters in Wilmington, NC are providing DSS for a concert on the beach just east of the city of Wilmington. ProbSevere LightningCast is showing the lightning threat of developing storms to Wilmington's west and northwest. The Storm Prediction Center also has posted a marginal severe wind threat in Wilmington's CWA. Hopefully FEEBS fans will stay safe!

Figure 1: Animation of LightningCast contours, GOES-16 day land cloud convection RGB, and GOES-16 GLM flash-extent density over southern North Carolina.

ProbWind and ProbTor Performance

 ProbSevere May Have Caught a Missed Severe Wind Event

The ProbSevere v3 drew attention to a cell near Bloomington, IN on the afternoon of June 8th. Specifically it was drawing attention to the wind threat with a high ProbWind percentage reaching 50% to 60%. However, radar interrogation was only initially yielding velocity of 30-40kts on the inbound side of the cell, sub-severe but certainly SPS worthy. There were a few scans yielding up to 45kts as well. So initially there was a little wondering why there was higher ProbWind percentages. Quick realization of the storm track being perpendicular to the radar beam could explain the lower velocity signatures here. Knowing this, ProbSevere and its ProbWind portion was drawing attention to a scenario that otherwise may have been missed if only looking at velocity data and not realizing the storm track relative to the radar beam.

ProbSevere v3 of “Bloomington Cell”

STP went up at 20Z coincident with new SPC mesoanalysis.

ProbSevere v3 readouts of “Bloomington Cell” at 1940Z

KIND Velocity signature of the “Bloomington Cell” @ 1941Z

ProbTOR Missed a Likely Tornado Event - First Example

At 2005Z the KIND radar showed a solid and persistent tornado signature on a cell near Shelbyville, IN. To go along with this in the overall outlook for the day was an MD highlighting the tornado risk and a Tornado Watch that included the southern half of IN. However, the ProbTor parameter did not tick up in response to the tornado signature on radar. The observed uptick at 2000Z, coincided with the intake of the new SPC mesoanalysis data that ProbSevere v3 ingests as described by the product’s providers. Even still, this uptick was small only amounting to a ~5% increase.

ProbTor only peaking at ~15%

The second image below may explain some of this away, showing that two individual cells were coalesced into a single storm identified by ProbSevere v3. These two cells were relatively close to each other, so much so that they did appear as one on MRMS data. However, the third image of SRM and V show the tornado signature associated with the northern cell. This combination, with the southern cell having a much lower tornado potential and being ingested by the northern cell may have played a role in lowering the overall ProbTor percentage.

ProbSevere v3 showing that cell being grouped with another to its south, could this have inhibited the increase in ProbTor?

SRM (left) and V (right) showing the TOR signature with this cell.

Multiple LSRs for wind damage were observed from this event, with a “tornado possible” added to the remarks.

The PHS SigTOR parameter also further supported the tornado risk during the 2000Z hour. The image below shows the PHS SigTOR parameter at 2000Z with ProbTOR percentages overlaid on top. The cell which produced the likely tornado east of Shelbyville, IN is sampled in the image with the ProbTOR only at 9%.

PHS SigTOR parameter pegging the area that produced a TOR. The cell highlighted with ProbTor readout produced the Tornado Warning referenced earlier.

ProbTOR Missed a Likely Tornado Event - Second Example

From roughly 2130Z to 2200Z, a supercell passing west to east through west-central OH showed a persistent meso signature as seen from the KILN radar in Wilmington, OH. This signature eventually depicted gate-to-gate shear and tornado warnings were issued for this cell. The same ongoing Tornado Watch from the prior example also covered this same region. Image three also shows the PHS SigTOR Parameter showing higher tornado potential in the region, although not directly overlaid with where the Tipp City cell was. However, the ProbTor parameter of ProbSevere v3 did not show a corresponding jump in tornado potential. Unlike the prior example which showed the ProbSevere v3 grabbing a second much weaker cell with the tornado producing cell, this was a discrete cell with no merger occurring.

Highlighted in the Tornado Warning issued by the Wilmington, OH office, was a tornado debris signature. The KDAY metar located just south of Tipp City also included “tornado” in the remarks signature, shown in image four.

KILN SRM and V showing tornado signature near Tipp City.

Time series of ProbSevere with persistently low ProbTor for tornado warned storm west of Tipp City.

PHS SigTOR Parameter highlighting higher tornado potential in the region with overlaid ProbSevere - ProbTor percentage for tornado warned cell by Tipp City.

The KDAY metar showed “tornado” in the remarks section for the cell passing through Tipp City.

- Trip

PHS, NUCAPS, Optical Flow, Prob Severe Fun

 PHS and NUCAPS

Today worked out well with PHS and NUCAPS. NUCAPS data came in shortly after opening up our work stations. We decided to compare the output between PHS, NUCAPS, and SPC mesoscale analysis. The variable that we chose was surface CAPE.

They all seemed to match up well highlighting the higher instability to the south that would gradually  push north this afternoon. It was definitely a confidence builder in each product to see the agreement between them.

Optical Flow

We also decided to compare the Optical Flow winds to SPC mesoscale analysis. Once storms developed a bit more, you can pick out a slight directional divergence signal in the flow. Looking at SPC mesoscale analysis there is also directional divergence is present in the mesoscale analysis.

Overall looking at these two examples, using these tools together can be a way to verify information and give the meteorologist more confidence (or less) in a specific product to help them with forecasts, DSS, and warning operations.

Prob Severe

We were able to compare Prob Severe V3 to the time when there was an observed report and when the new tornado warning came with a radar observed tag due to a CC drop. The first image is when there was a twitter report of a tornado around 2142Z in SE Darke county.

At 2144Z the Prob Severe V2 tornado jumped to 21% while V3 only went to 6%.

The next image below is when the radar confirmed tornado was reported.

- Noctilucent & Matador

PHS CAPE localized maximum compared with storms developing in the area

 PHS CAPE values increase from north to south over Fort Stockton. This correlated well with RAP mesoanalyzed SB CAPE on SPC webpage. Storms actively going up along this gradient as an outflow boundary pushed south during the early afternoon from overnight convection over Oklahoma.  

PHS CAPE 18Z 1 hour forecast for 19Z

PHS CAPE 18Z 2 hour forecast for 20Z.

Storms developing over Fort Stockton via Day Cloud Phase Distinction on GOES 17 Mesosector

We showed above that the north side of the outflow would contain more instability - which is directly related to the moisture from the morning MCS outflow. The Gridded NUCAPS provides additional insight using the 850mb moisture fields from both AQUA and NOAA20 respectively - validating our hypothesis.

We double checked since there was a dust advisory/dust in the forecast and yes - Dust

Don't warn if pop = 0

Convection was skirting the northeast portion of the CWA so we’ll use the recent pass of NOAA-20 to view the potential for convection redevelopment to the west and affecting the forecast in our CWA. Here are the Modified NUCAPS soundings:

The top image is for the sounding in Jones county, below is Scurry - which shows a capping inversion still in place.

Storm Motion

Weak winds aloft and throughout the atmosphere have contributed to very little in the way of storm motion. Hence, locally heavy rainfall may begin to evolve, even over an area that has received very little rainfall in the last 6 months.

Optical Flow Winds in the 200-100 mb level.

Day Cloud Phase valid 2041Z.

Day Cloud Phase valid 2141Z.

PHS depicts this plume of moisture and associated instability will back into New Mexico this evening. Could it play a part in tomorrow's severe weather risk?

Here is what happened at El Paso when the front backed into the area - Dewpoint jumped from 30F to 50F

- David Spritz

- Mr. Bean