Developing Storm Using CI

I noticed at 20:17z the cluster of CU showed up as green for development.  On radar the returns were green and low but showed some development.  When the CI went away in the next frame, we had yellow returns on radar...then it grew to a t-storm by 21:38z.

Lightning started showing up just after the CI fields disappeared. 

MAF - RGBs Showing Convection Developing over the Davis Mountains

2115Z: Convection continues to develop over the Davis Mountains of SW TX with ice clouds now present as identified by the Day Cloud Phase, Day Cloud Convection, & Simple Water Vapor GOES-16 derived RGBs. Additionally, MRMS isothermal reflectivity shows our first echoes developing at the -20C level. However, no signs of any lightning activity yet on the GLM products.
This region has been my primary of interest for storms this afternoon so will continue to monitor these cells as the afternoon continues.

GOES-16 RGB 4-Panel:

Peter Sunday

Developing Showers. Using ALLSkyLAP

Some showers have popped in the area that showed mid-level clouds on the water vapor imagery an hour ago or so.  The cloud tops are up to 20-30,000 ft.  The showers are moving into a better environment where they can tap into CAPE.  That has increased to over 1,000J/kg. There is no lightning showing up in GLM...yet.  We're really just waiting around to see if these organize at all. 

-Penny Gardens

GLM FED vs ED with GOES-16 Ch 13 and Day Cloud Convection

I can see some utility to using 5-min/1-min update GLM Event Density when forecasting storm intensification. I compared both the 5-min/1-min update GLM Flash Extent Density (FED) and the 5-min/1-min update GLM Event Density (ED), also showing IR and Day Cloud Convection at the same time(s) as a storm along the central MD / N VA border strengthened pretty rapidly over a 15-min period.

Throughout the strengthening process, the 5-min GLM ED picked up on the strengthening updraft/strengthening process better than the 5-min GLM FED, as evidenced by the high number of events in the ED product vs lower numbers in the FED product. One can also see the development very clearly in the IR image (cloud top cooling) and Day Cloud Convection (bubbling up of the convective cloud and beginning of the anvil spreading) in the three images below.

As Event Density numbers can get pretty high (they reached 207 per 5 min in this small storm), I would recommend making the gradient in the color bar above 100 events stand out a lot better; half the bar is a blue color, which is less than 20 events...probably not that useful for a 5-min product.

1849Z (except IR, which is 1847Z):

1855Z (except IR, which is 1857Z):

1904Z (except IR, which is 1902Z):

- Thomas Bell

ProbSevere Percentages Associated With Storm Clustering?

[21:00 UTC] As strong to severe convection continues to progress just south of the immediate DC area, it was interesting to note that ProbSevere percentages increased as the algorithm(s) clumped the separate storms together as if they were "one" storm. When this happened, ProbSevere showed an unrealistic jump in severe percentages that then decreased again once the algorithm identified the cluster as "multiple" storms. Interestingly though, in the following couple of radar scans following the "separate clustering", the 0.5 degree V from KLWX showed an enhanced area of outbound wind of approximately 40 to 45 kts at several hundred feet AGL. For ProbSevere, but more specifically ProbWind, values did not respond and remained fairly low (on the order of 40-60%). Therefore, the ProbSevere "increase" seemed more tied to the false clustering of storms rather than the specific increase/enhancement in outbound/outflow from the storms themselves.

 Fig. 1: Note the sudden increase in ProbSevere as it falsely "clusters" the storms together, but then returns to "regular" values as it identifies the storms as separate entities.

Rosie Red

MAF - Gridded NUCAPS comparisons

2045Z: With the first echoes appearing over the Davis Mountains, I was able to look at gridded NUCAPS to determine the state of the atmosphere. I was most interested in looking at the mid-level lapse rate fields, especially if they were steeper than  my initial analysis earlier this afternoon.

NUCAPS 700-500 mb lapse rates were generally around 6.5-7 C/km over SE NM & W TX. Comparing these lapse rates to the HRRR, GFS, & NAM40 the NUCAPS were the least steep with the GFS & NAM40 especially forecasting 700-500 mb lapse rate values of 7-7.5 C/km. In this case NUCAPS actually compared the best to SPC mesoanalysis values which are what I usually look at in a warning operation environment. This helped add to my confidence in the overall evolution of the event & widespread severe weather still looks unlikely.
NUCAPS 700-500 mb lapse rates 4panel:

Earlier this afternoon I was looking at the gridded NUCAPS fields with the data blacked out in areas with bad NUCAPS soundings. It was difficult to piece together spatial trends & gradients with all of the data blackouts & I did not find these fields very useful. As of this blog post we now have the NUCAPS gridded fields with continuous data & the blacked out areas now filled in. While this data may not be as "realistic" it is much easier to spatially analyze the data & use the product in an operational sense. I would highly recommend preesenting the data this way in an operational setting.
NUCAPS Spatially Continuous Data:

Peter Sunday

I noticed with the storm that is warned in NM we have the highest probability in ProbSevere, but the lightning has disappeared briefly.  Then the lightning returned.  This is an atypical storm since it has formed in the mountains so the threshold for severe warnings is different than a great plains storm.   The warning continues for another 40s mins.  Lightning rates keep disappearing, showing a decrease in activity.  The ProbSevere has decreased as well. The threshold for severe hail, and wind are both very low as the lightning has almost disappeared. 

The storm is continuing to weaken...the lightning products are back and forth.  The warning is still up and there are no storm reports.

MD for WFO Sterling - 21:00 UTC

[21:00 UTC] Convection continues to progress east-southeast through my area this afternoon, and is approximately 2/3 of the way through the CWA as of this writing. Ahead of the convection, low level moisture and instability continues to pool (particularly in the south/east portions of the FA), per latest AllSkyLAP Precipitable Water and CAPE fields (see below). Nevertheless, mid-level lapse rates continue to be fairly marginal, so do think that severe hail risk will remain fairly low. With steeper low level lapse rates, wind continues to be the primary threat with this convection, and have already seen several damaging wind reports in my southwest with a localized bowing structure that moved through just before 20:00 UTC. Environment behind the more or less continuous convective structure has been worked over quite a bit, so think that while storm chances will linger, severe threat has pretty much ended in these areas.

As for the storms themselves, have seen a recent drop in cloud top temperatures and jump in cloud top heights with the convection that has just moved through the immediate DC area. Have also seen a corresponding increase in ProbSevere (but more specifically, ProbWind) and these storms will continue to be the main item of interest over the next several hours, particularly as they move into an environment that has become increasingly supportive of storm maintenance.

Fig. 1: AllSkyLAP Layer PW at 20:00 UTC

Fig. 2: AllSkyLAP Layer CAPE at 20:00 UTC

Fig. 3: GOES-East Cloud Top Temperature from approximately 20:00 UTC to 21:00 UTC

Rosie Red 

Severe CI

At first glance I used severe CI to see where the best chance for a severe storm may develop.  But further investigation showed that I misinterpreted what it actually meant.
When I scrolled over the value, it was blue and read 1%.  I thought blue could be 10-20% chance, but in this case it was very low.   That 1% chance is too low to plot, in my opinion.  The color table had no change from 0% to 30% so maybe get rid of everything before 30%?  Trying to filter out the noise and the unnecessary data.

-Penny Gardens

A comparison of NUCAPS and model 850-500mb lapse rates

Just did a comparison of NUCAPS, HRRR, GFS-20 and NAM40 850-500mb lapse rates (loaded as images) as storms were just beginning to fire across the Mid-Atlantic. Where data was available during the pass, the model and NUCAPS data compared favorably around the 17-18Z timeframe. Unfortunately, due to clouds and precip areas, the NUCAPS data was pretty choppy-looking, which one can see below. (NUCAPS image is top left, HRRR is top right, GFS-20 is bottom left, NAM-40 is bottom right.)

I did learn from one of the developers that, via a plan view, NUCAPS data displays much better as an image than it does as a grid. I loaded the data as a grid just for the heck of it. I will definitely stick with the image view!

- Thomas Bell