ILX Mesoscale Discussion

GOES_East Mesosector 2 Imagery (Band 2)

The effective surface cold front remains well north of Illinois, draped west to east across central Wisconsin as of the 22z surface analysis. Further south across the state, two main forcing mechanisms continue to play host to strong to severe convection. The first (southernmost boundary) is nearly stationary acting as the area of primary convergence, while also service as the dividing line between 70 degree dewpoints (south) and mid to upper 60s (north). The second is an outflow boundary loosely associated with earlier day convection, which continues to race southward driven largely by cold pool propagation. This boundary is anticipated to overtake the primary boundary over the next few hours, ushering the majority of shower and storm activity south of the Lincoln IL CWA later this evening (Showcased well by NUCAPS forecasts). With ample CAPE (1500 - 2500 J/KG per the 22z AllSkyLAP product) remaining along and south of said boundaries, storms are expected to retain their intensities through the early evening hours. Primary threats will remain damaging wind gusts, large hail, and flash flooding primarily in areas that see repeat thunderstorm convection this afternoon and evening.

-----------------------------------------------------------------------------------------------------Mountain Bone

LSX Mesoscale Discussion (Mountain Bone)

Ongoing sub-severe convection continues to develop along a decayed MCS boundary. This convection is primarily located along and south of the I-70 Corridor as of 2130z, but continues to press east into a favorable environment for continued/sustained convection, characterized by modest Instability (1400 - 2000 J/KG ML CAPE) according to All-Sky LAPS derived CAPE values and near 70 degree dewpoint temperatures. Kinematics continue to be unimpressive, with the majority of the forecast area remaining in an area characterized by sub-40kt bulk shear values with little to no sfc-1km effective shear layer. A stray embedded strong to supercellular storm will remain possible this afternoon and evening as the multicell cluster continues to fill in and push east, especially with the arrival of a weak LLJ feature which may help to organize/ strengthen the area of convection by 00z/7pm CDT. PWATs (1.5 to 1.75inches) continue to increase, especially across the low to mid-levels, which could support some isolated heavy downpours which may lead to additional flooding. Primary threats: Strong winds, small hail, and flooding rains.
-----------------------------------------------------------------------------------------------------Mountain Bone

EAX Mesoscale Type Discussion (Mountain Bone)

Continuing to see clearing behind the decaying MCS as of 21z. This has allowed ML Cape values to jump above the 2000 - 3000 J/KG range along and northwest of I-35 per the All-Sky Layer Convective Available Potential Energy product. This is in general agreement with 18z NUCAPs soundings with further downstream propagation of best CAPE region likely over the next few hours per the NUCAPs forecast products. With that being said, not sold on the availability of an efficient enough lifting mechanism across this region over the next few hours to get widespread initiation underway. Best chance of seeing that will be further east of I-35 where a pretty pronounced differential heating boundary exists per in-situ observations.
Convection development and location is too uncertain to entertain a watch issuance this far north as of 21z Tuesday.
--------------------------------------------------------------------------------------------------Mountain Bone

Area Discussion Prior to Severe Wx Kickoff

Area discussion for the Dakotas: Lower heights area located over western S Dakota and stacks from 700-500mb and will make its way easterly throughout the day. 850mb winds from the south at 30Kts.
METSAT shows low/mid clouds moving into ND from the west with clearing over the center of the states where wx is expected. Upstream surface observations support this clearing as they show dry air advecting into the area from the south.

Radar shows weak convective activity to the north moving into Canada. Models and the SREF are in agreement that the majority of thunderstorm development happen around 1-3z.

Merged TPW Composite total PW values over the center of the N/S Dakota states where convection is expected according to SPC outlook is less than 1” with values between .80-.95” and AllSkyLAP 900mb PW is even lower at .30”.



NUCAPS fcst Sfc CAPE overlay CAPE values range between 400-500/kg but there are quite a few gaps in coverage.



Meanwhile AllskyLAP CAPE shows 900-1500J/kg, and NAM models show extremely high CAPE values of 3000-4500J/kg.



Local TAFs show no thunderstorms or even rain while the SPC continues to carry SLGT over the Dakotas. It’ll be interesting to see how this scenario plays out as the day progresses.

--DESMOND--

Separating threats in D2D with ProbSevere2

It's nice to break out ProbHail, ProbWind, and ProbTor as separate displays (right hand column below) - something that is not even possible with the ProbSevere v2 placefiles.



ProbHail was the greatest threat (far upper left panels), topping out around 33%, and culminating in a quarter size hail report (below, upper right). It's been pointed out that ProbSevere has been much harder to calibrate out west where there are fewer reports and thermodynamics are different. So, it's really all about trends instead of quantities.



#MarfaFront

Wrappin' my head around some other GLM stuff

Upper Left: 1-minute visible with 5 minute cloud flash (1-min update)
Upper Right: Total Optical Energy
Lower Left: GLM Average Group Area
Lower Right: Event Density
Bright yellow/orange colors on lower left depict a smaller average group area associated with a tighter concentration of flashes. We are intermittently seeing greater concentrations at the southern extent in an area otherwise associated with little activity. 



Now taking a look at a specific time below...



We see a single pixel of orange (lower part of lower left panel) corresponding with a small group area. This appears to be associated with two fairly isolated ENTLN flashes (upper left).  Total Optical Energy (upper right) and Event Density values (lower right) are not overly impressive, which is not surprising, given the limited activity.

Now for something else that's rather striking (ha ha) in the eastern half of this area. ENTLN cloud flashes depict two active areas in the northeast corner but little if any activity to the southeast beyond that. Shown another way...



So, we see good connectivity in probable electrification from northwest to southeast that is not otherwise apparent in the flash data. So, I'm slowly coming around to the idea that this can be helpful for IDSS applications when lightning is a concern with multi-cell clusters featuring extensive anvil coverage.

#MarfaFront

GLM - Florida Coast

Convection off the coast of Florida developed into a few organized strong to severe storms over marine zones. GLM Flash Extent Density (upper left)  was far and away the most useful of the GLM products available for warning operations. The strongest storms were the most evident on this product compared to the others, and rapid lightning increases were most easily noted. This allows for quick use of the lightning data for situational awareness and setting priorities when there are numerous storms to interrogate. The other GLM products generally washed out any signal of which storms were the strongest, and didn't provide as much information about overall storm trends.


The rapid 1-minute update times that can be linked with 1-minute meso sector satellite imagery and 2-minute MRMS data can allow for more rapid warning decisions (and thus more lead time) when all considered together with base radar data.

Compared to ENTLN 1km total flash data, there wasn't much difference in warning utility between the two products. The same information can be derived from each product in terms of storm intensity and picking out the strongest updrafts. I would give a slight edge to the ENTLN in terms of product display as the smaller grid allows for better viewing of the background satellite imagery. However, the spatial extent aspect of the GLM has advantages for public safety messaging. So overall a very even match between the two products.



-- warmbias --

Event Density with RGB Composite VIS/IR Sandwich

Image 1 shows the  GOES16 RGB Composite VIS/IR Sandwich.  This product displays the texture of the convective cloud tops and the temperature of those cloud tops.  The texture and temperature of the clouds provides information about the updraft.  The 2nd image shows the most intense GOESR GLM event densities and how they correspond with the taller clouds and strong updrafts. - Jonathan W. Smith (ESSIC/UMD)

This was interesting

Since things were kinda boring over HGX today I had to look for things to blog about. Here is something interesting that I noticed with the Vis/IR Sandwich RGB. At the beginning of the loop the RGB didn't show any IR brightness temperatures. As the TCU continued to develop we saw pixels of IR brightness temperatures starting to show up indicating cold cloud tops and the potential for glaciation to start. Low and behold, if we continue to watch the loop, more pixels start showing up...and a few minutes later both GLM and ground based networks picked up on a couple of CGs. As the thunderstorm developed, cloud tops cooled and more pixels started getting displayed we began to see more lightning.  This was something that I didn't expect the RGB to pick up on and potentially helpful for situational awareness and IDSS in the west where most lightning tends to come from single cell thunderstorms. If you are able to pick up on these ahead of time you may be able to some lead time before lightning occurs.



Update...it happened again, pixels starting being displayed and then lightning occurred within a couple of minutes. If this generally hold true for single cell thunderstorms this would be awesome for outdoor IDSS.

Comparison of ATPW and Blended TPW

I was finally able to take a look the ATPW (top left) and compare it with the operational blended TPW (top right). My first impression was that both products show similar large scale patterns with a large plume of moisture extending from the Gulf of Mexico into the Ohio River Valley. The ATPW also tends to show a little more detail in the moisture field compared to the blended TPW.

At 15Z ATPW shows an area of lower moisture over the Texas Gulf coast which is sort of fills in by 17Z, likely due to upstream moisture being advected into the area. In contrast, this moisture is continuously present in the blended TPW. ATPW generally had PWATs around 1.5 in, while the blended TPW had PWATs around 1.7-1.8 in. In contrast, 12Z RAOBs along the coast had PWATs that ranged from 1.6 inches at KBRO to around 1.8 at KLCH. These values seems to match better with the blended TPW product. I suspect that the upstream convection over Louisiana and lingering clouds over the coast impacted the ATPW that was corrected in the blended TPW.

Average Flash Area Product & Convective Development

Isolated convection trying to develop across TX Panhandle. GLM Average Flash Area product picking up on initial lightning activity within the developing convection.

Scale (and color table choice) is Everything

Big flashes taking place in the stratiform region of the departing MCS across the eastern third of Texas.  A LOT of big flashes:



But that doesn't tell the full story; there are a LOT of big flashes but they are being masked by the scaling of Flash Area.  Right now the scale runs from 64 km² to 2000 km².  What happens if we bump that max side up to 4000 km²?



There we go, a bit better discrimination on the big-side of the scale!  It may be hard to see but there is one "white" flash in there; a slightly larger 4600 km² flash southeast of DFW.

That. is. Yuuuuuuuuuuge.

So, lesson of the day; check the values of flash size (or any flash component).  See if there are values past the end of the current color scale.  Right click on the appropriate product, select Change Colormap , and bump that up some.  May be able to pull out a bit more information than what comes as the default.  Once again however...YMMV.

-Dusty

Here's an exciting non-case. Hooary!

In this example, Houston County in the far Northern HGX CWA was in horrible radar coverage with 0.5 degree radar scans over 12kft AGL. With the success of GLM FED predicting severe storms earlier in the day this was used to give confidence NOT to issue a warning for this area, despite slight bowing in the sloppy reflectivity and an abundance of activity in the ENTLN network.



#ProtectAndDissipate

GLM Activity In Developing Line of Storms

The outflow from the main line of storms was moving west and combined with a strong cell which was spawned off the dryline, resulting in a strong line of storms forming where the two converged. Something that was noted was the delay in GLM FED with the developing convection, where flashes could be seen quickly from the ENTLN. Chalked this up to the optical depth of the storm at the time covering the flashed from the GLM given the extent of cloud-to-ground strikes. Later on, a line of increased GLM FED could be seen.





#ProtectAndDissipate

GOES All Sky LAP TPW and CIRA Merged TPW Cloud Mask Differences

At 22 UTC on 6 May 2019, the All Sky LAP and CIRA Merged TPW Data type products show differences in the cloud mask.  A shallow Cu field over NC / SC is indicated in GOES visible imagery,.  The data type masks of the two products (blue = clear; yellow / gray = clouds) show some clouds in the All Sky LAP mask, while the CIRA Merged TPW mask does not have these Cu detected.  This is likely due to the lower resolution (~ 15 km) of the GOES-16 TPW data used in Merged TPW versus the All Sky LAP resolution.







GOES-R TPW has a nominal resolution of 10 km.

JohnF

Early Detection of Convection w/GLM

Impressed by the early convective detection by GLM in this case. The image below was in real time and you can see the GLM Minimum Flash Area and Flash Extent Density is already lighting up in Oldham County in the AMA CWA. However, the 1-minute MESO GOES-16 data barely had cooling cloud tops being detected and there was no detection of precip at that location on MRMS yet (actual first time of detection was 2-minutes sooner than picture below where MRMS has no detection of radar echoes).



#ProtectAndDissipate

GLM behavior, overlaid with +40dbz/vis sat throughout a CI event and storm split

Full loop from CI through storm split. A good practice for GLM users overlaying with radar is to Alpha your color table below a certain range (in this case 40 dbz) to mask out low reflectivity values and focus on storm cores only. Because of the parallax error, the storm cores on GLM are displaced to the northwest of the radar cores - a hidden benefit for storm interrogation!

There are several things to note here. First is the onset of GLM data - this storm featured explosive development. The GLM data here is 5 min/1min update. Because of this, the upward trend is rather sudden - for early stages in deep convection it may be best to use 1 min data. As the supercell splits, the the different cores are most evident in the top left, which is Event density data. FED, AFA, and TOE do not snow this trend nearly as well. I chose not to include a loop of Minimum area, because this data was too low -resolution to capture details of different cores this close.



This is a longer loop of the same event showing the storm through its demise. You can see the Average Flash Area in the storm in the bottom left really increase as this particular supercell diminishes. This is consistent with the idea that shorter length lightning in the core ceases and most of the remaining strikes are longer flash events in the residual anvil.

-Dusty Davis

GLM, Satellite, and Convection Initiation

For the first time this week, finally got a chance to examine CI using GLM data. I built a 4 panel that worked well for me (ENTLN CG and cloud flashes on each panel):

top L: 1 minute visible with flash extent density (FED) and event density (ED)

top R: 1 minute Vis/IR sandwich with 1 minute total optical energy (TOE)

bottom L: 1 minute Day Cloud Phase Distinction/Day Convection RGBs with average flash area (AFA)

bottom R: MRMS -10C reflectivity with minimum flash area (MFA)





Agitated cu developed just prior to this image at 1634z. These two images highlight the differences between FED (upper L of the top image) and ED (upper L of the bottom image). You'll notice that the flash extent density is much more muted than the event density. You can really hone in on the strongest initial convective cores with the ED and TOE compared to the FED.





Next two images are at 1651z with FED highlighted in the top image and ED in the bottom. Again, your eye is immediately drawn to the event density vs. the flash extent density. Also, your total optical energy corroborates with high values on the southern cell (at least with respect to electrical activity...radar showed both cores with similar 50 dBZ heights).





By 1725z, both event density and total optical energy are beginning to overwhelm and lose granularity. At this point, flash extent density highlights the more active cores. ED and TOE are both still useful, but the distinct advantages they showed earlier in convective evolution have degraded as convection has matured.





by 1929z, it's fairly obvious that the advantage TOE had in highlighting distinct cores early is no longer. While you can see smaller areas of enhanced optical energy, it is far noisier. We've noticed this throughout the week that TOE's usefulness seems to wane as convection matures and storms are extremely electrically active. Flash extent density seems to be a better choice at this point compared to event density, as was the case at 1725z.

A few of the biggest takeaways...Total optical energy (1 minute) serves a very useful purpose for CI as it can highlight areas of new updraft growth, but loses impact as storms become mature and lightning becomes well established across the area. Event density would seem to be a better choice for CI compared to flash extent density as well.

The four panel that I built I've found very useful for CI or subsequent new updraft development by combining the best of visible imagery, RGBs (are utilized to diagnose glaciation within clouds), and the MRMS -10C reflectivity. Time for more coffee.

--Stanley Cupp

Spectacular 1 min GOES satellite imagery of a Colorado supercell

Using feature following zoom to stationary view track a supercell  in ECO. Many things visible here, including uplift and twisting of stratus deck in the inflow region, anvil plume texture, and updraft texture. The parallax error ends up helping the user get more info about the vertical structure and composition of the storm - contrary to the often requested need for 'parallax corrected' imagery.



Day cloud phase 1 min of the same storm. Does not get much better than this!

-Dusty Davis

GLM Total Optical Energy for early storm development

GLM Total Optical Energy product shows rapid increase of lightning in a 14 minute span for a developing thunderstorm in southwest Texas.  This is useful information to forecasters for diagnosing storm intensification which usually precedes a response on radar. 

-Jake Johnson