Day 1 Wrap Up

Below are comments from yesterday's activity:

GLM

Came in pretty open minded and didn’t know what to expect

Found it useful overlayed with the ENI data

Helped provide more details than what was there before

Liked having the aerial extent of lightning for lightning safety

Found it useful to incorporate within a TV broadcast, especially in showing the coverage of the lightning
within a storm

Still useful to compare with current lightning network to get the CG strokes in conjunction with the GLM
data

Not sure what to make of the event density and group density with it being the first time seeing it

With the 5 minute running sum, a lot of the cores would run off the top of the color scale

ProbSevere

Seemed to work pretty well with the convective line in Virginia

ProbTor had a bit of a ramp up as the storms approached D.C. as some rotation developed around D.C.
on the north end of the line

The color scale seems not intuitive where the low end and high end fit both in the cool color range

Provides good triage in busy situations and works very well

Tried overlaying it on MRMS products instead of having it on base data and liked having it that way
pretty well

Having more discrete colors instead of a gradient or have increasing line thickness with higher
probabilities

ProbTor should probably have a different color scale loaded more to the lower end instead of the
same as wind and hail.

Think it’s better to have all of the individual hazards contours and readouts than the whole big long
readout

It would be useful to have a time series tool for ProbSevere

NUCAPS

Modified didn’t come in yesterday would have been a useful product yesterday.

Surface temperatures and dew points were quite a bit too cold in the regular NUCAPS

The spatial availability is a great aspect of the soundings especially in areas of sparse coverage

Thought the data looked pretty good particularly in the mid and upper levels

Training needs to be hit harder to know that these soundings exist now

Gridded products need to be simplified to have options of surface data instead of just pressure levels

Having the more passes the better

Useful for these purposes of having greater observational coverage

For boundary layer identification having the more timely data is very important, when looking at lapse
rates or something having the less timely data can still be useful

Bad soundings were advertised as bad

CI and All-Sky LAP

The All-Sky LAP was found useful but could definitely see where the model is seen

Might be better to use the RAP or to have a little better blending to make it less blocky

The CI didn’t seem to handle the towering Cu in NW Oklahoma very well where convection ended up
firing later in the day

There were quite a few false alarm areas in the field as well

Would be able to filter out some of the noise by raising the lower end threshold to eliminate some of
the very low probabilities

Didn’t look at the severe since regular CI values were all pretty low

Tornado Potential Near Washington D.C.

A line of thunderstorms from southern Pennsylvania to northern West Virginia moved southeast into Virginia and Maryland around the Washington, D.C. area. For much of the afternoon, the main threat was from damaging wind and hail.

As the line moved through northern Virginia, it began to interact and eventually merge with a couple of isolated severe thunderstorms that formed earlier in the afternoon ahead of the main line. A field of broken cumulus clouds in between the line and the isolated cells developed very rapidly into a line of severe thunderstorms that produced a number of reports of large hail and damaging straight-line winds.

As the northern end of the line approached the Washington, D.C. area, the southern end of the line surged southeastward into the area south of the isolated cells. The northern end of the line slowed as the cells merged with the northern end of the line. As a result, a very nice mesocyclone became very evident in the NEXRAD imagery as it passed near the Sterling radar site. Tornado warnings were issued, although no touchdowns were reported (a funnel cloud was observed at the Sterling office).

Of particular interest to me was the increase in lightning as the merging between the cells and the line took place, followed by a decrease in lightning as the mesocyclone formed. Also evident was the progression of overshooting cloud tops along the line as the mergers took place, with the overshooting tops traveling in an east-northeasterly direction toward the DC area while the line of storms moved steadily to the southeast. as the more robust thunderstorm activity moved southeast of the DC area, you could see how by using the NEXRAD data along with the satellite and lightning data the tornado threat might have been on the increase toward the DC area, while a more significant wind, hail, and heavy rain threat was favoring areas to the south.

Finally, the ProbTor product took that into account and while not overly high, showed an increase to about 30% as the storms moved toward Washington, D.C., then decreased very rapidly after that as the mesocyclone became rain-wrapped and fell behind the main line of thunderstorms as they headed south of the DC area.

Gary Cannalte

Prob Severe With Line West of D.C.

The image below shows a 4-panel display of the prob severe product for the line of strong to severe storms near the D.C.  area this afternoon. This includes the experimental ProbWind (upper right), ProbHail (lower left) and ProbTor (lower right). Up to this time (2212z) ProbWind had been running 80% or better and ProbHail at 90% or better. ProbTor stayed below 10% and would typically be lower anyway, especially in a QLCS situation. WFO LWX did issue a tornado  warning at 2212z.

Al Cope

Convective Initiation Product

Given the strong instability across the region, I was anticipating a greater signal in the CI product. AllSkyLAP CAPE values sstill exceeded 2500 J/kg in the area and Cu were finally beginning to bubble up, but the CI product showed little in the way of probabilities.

Fig 1.  AllSkyCAPE indicating 2500+ J/kg at 2200 UTC.

Fig 2. CI Probability product at 2237 UTC.

I'm sure there are other limiting factors that I'm not taking into account but I found this discrepancy and departure from my conceptual model to be interesting.

wall_cloud

Severe Weather Over Virginia/Maryland

It was interesting to see the evolution of severe weather to the northwest of Washington, D.C. A line of thunderstorms in southern Pennsylvania and northern West Virginia was moving to the southeast, while isolated cells developed and became severe ahead of the main line near Madison, VA. It was interesting to see how the lightning from the GLM data ramped up quickly shortly before the storm became severe (it produced quarter sized hail).

I was able to note the 1 minute average flash area spread will out ahead of the precipitation area in front on the storm and also extend in the anvil behind the storm as well. As a broadcast meteorologist, it was a great way to explain to viewers the lightning threat away from the precipitation.

Gary Cannalte

Anvil lightning

The GLM data is providing a great example of anvil lightning this afternoon. Per the ENI lightning data, no ground strikes are occurring to the north of the primary cell, but there are Pulse/Flash detections.

Fig 1. Comparison of the GLM and ENI lightning data.

The GLM data shows a large area of low flash density, but the total energy signature and average flash area are relatively high.  I find this to be very useful in the IDSS realm where lightning can occur at various distances from the storms themselves. The GLM provides a good situational awareness whereas the ENI data is somewhat difficult to see given the small size of the data points.

wall cloud

Late Afternoon Convective Trends

Convective development continues to increase near the northwest portion of the forecast area late this afternoon. This broken convective line extends from the Kansas City area into the Texas panhandle along a frontal boundary/dry line.

Day Cloud Phase Distinction RGB/Day Cloud Convection RGB/GLM Flash Extent Density

The airmass to the east of the boundary is becoming very unstable with surface temperatures near 90F and surface dew points near 70F. CAPE values on AllSKy LAP CAPE are around 3000 J/kg. However, a similar NUCAPS sounding suggests CAPE values near 5000 J/kg in the same area. These values are closer to those suggested by some high resolution guidance.

AllSky LAP CAPE

NUCAPS Sounding East of Dry Line

The main limiting factor for severe storms this afternoon is relatively weak shear, with bulk shear values  around 25 kts. However, shear profiles will increase somewhat over the next couple of hours as a weak upper-level disturbance interacts with the dry line. Some of this enhancement can already be seen with the development over the Texas panhandle.

Alex Brown

Watching lightning initiation

I wanted to compare the ENI Total Lightning with the GLM when it come to detecting the onset of lightning within a developing storm. A storm was developing along the OK/KS border between 19-20z.  Overlaying both the ENI and GLM data, they were actually VERY close.

Fig 1. Initial lightning dection on storm near Ponca City,

 OK.

The ENI had the earlier detection in this case, but only by one minute. One thing that jumped out very quickly was the parallax issue which caused the ENI and GLM data to be offset by ~10 miles, each detecting lightning on different sides of the state line.

wall_cloud

Forecast for 5/14/18

Significant instability is currently observed across the Southern Plains. AllSkyLAP CAPE values on the order of 3000-3500 J/kg were detected over north central OK and southern KS. Surface temperatures in the lower 90s were already allowing storms to develop as of 19z with more widespread convection anticipated over the next few hours.

Fig 1. AllSkyLAP CAPE at 1900 UTC.

Deep-layer shear is not optimal for the development of supercells today, but effective bulk wind difference ~30 kts will support mutlicellular convection along the quasi-stationary front and southward in the vicinity of the dryline. Expect multicell clusters to develop this afternoon, providing a significant hail threat given the steep mid-level lapse rates (NUCAPS 700-500 mb lapse rates exceeding 8 C/km) and ample buoyancy. As cold pools begin to develop in a deep mixed boundary layer, storms will likely grow upscale into several loose multicell systems with the severe weather threat transition more toward wind.

Fig 2. NUCAPS 18 UTC sounding near KPNC.

wall_cloud

Week 3 Day 1

Today begins the third week of the Satellite Proving Ground Experiment in the HWT. Today we will be beginning operations in the Sterling, Va and Norman, OK CWAs. These will experience totally different environments as a line of storms is expected to move over the Mid-Atlantic this afternoon and severe storms should develop along the dryline in western Oklahoma later today. It will be a good test to evaluate the products in these two different environments.

-Michael