AllSkyLAP Resolves Dry Mid-Level Layer

An eastward moving plume of moisture and instability was clearly depicted in the GOES16-Merged GFS AllSkyLAP products.  Estimated MLCAPE in the lower left panel is similar to the SPC mesoanlaysis data.  Into central Pennsylvania, values were in the 500-700 J/kg range.  So certainly on the low end for severe weather potential in the State College CWA based on instability alone.  However, one interesting feature caught my eye in the 700-300mb AllSky PWAT analysis -- a west-to-east band of low values advecting through Indiana and Ohio into western PA. This mid-level drying is attendant to the eastern periphery of an EML that originated over the southwest U.S.  A plume of warmer 700mb temperatures in the RAP analysis matches up well with this dry band of mid-level air.  With the chance for scattered convection later today in central PA, the influx of a dry mid-level layer may aid in the production of strong convective winds/downbursts. -Roy

GLM Observations in the Tx Panhandle

A supercell moving northward along the dryline over the Texas Panhandle region underwent a split over the last 20 minutes or so. Preceding the split, there was a notable decrease in 5 minute GLM Flash Extend Density and Event Density.  After the split, there were to notable maxes in both of these products. However, in the GLM Minimum Flash Area, this trend was not observed due to the more coarse resolution of the product. Better resolution may have helped identify both updraft regions within the 2 storms after the split. Additionally, a downward trend was noted in 5 Event Density and Flash Extent Density despite no real change in the ENTLN lightning activity. A loop of GLM data and IR/Vis depicting  this storm split is below.



-64BoggsLites

Comparisons of NUCAPS and Model Data Lapse Rates...

So, it can be refreshing to see when NUCAPS data agree with model data, but I'm often more interested in those cases where there are differences, and potentially important differences.  Notice in the images below the comparisons between NUCAPS 850-500 mb lapse rates and various model data.

Image 1. 850-500 mb lapse rates from NUCAPS (upper left), HRRR (upper right), GFS (lower left), and NAM40 (lower right), valid ~18 UTC 23 May 2019

Notice the relatively large differences that stretch SW to NE from central W VA into New England.  Taking a look at nearby radar imagery, it's clear why this area had significantly lower lapse rate values in the NUCAPS data than the models; a line of showers and thunderstorms were present along this path of lower values that was displayed in the NUCAPS gridded data (Image 2).

Image 2.  850-500 mb lapse rates from NUCAPS (upper left), HRRR (upper right), GFS (lower left), and NAM40 (lower right), along with 0.5 Refl from the KCCX radar, valid ~18 UTC 23 May 2019

Of course, the NUCAPS retrievals certainly would have been affected by this area of denser clouds and precipitation.  Nevertheless, lapse rates would be affected (lowered) by the convection in those locations, which is depicted in the NUCAPS data only.  So, the lack of this feature in the models would then affect their forecast in this region going forward.  It will be interesting to see the NUCAPS forecast data in this type of scenario.  In fact, one of the forecasters here is taking a look.

-Kris W

Examining the NUCAPS FCST of CAPE

Below is a loop of the NUCAPS CAPE forecast for the afternoon across the CTP CWA.



Unfortunately, the product is very blocky, and makes it hard to use, especially since some of the missing data is in the time and place where high impact weather may occur. It's clear that it is trying to show some elevated CAPE moving across central Pennsylvania, but the values are very suspect to me given the missing chunks of information.

Thorcaster

Using Modified NUCAPS to help examine air mass downstream

The air mass in the CTP CWA has been modified somewhat based on earlier convection. Here's a NUCAPS sounding from central PA (note that it was yellow, meaning it IR retrieval failed due to clouds, but the microwave was successful).



Notice the low level CAP, as well as the modest mid level lapse rates of 6.1 C/km. To get an idea of the air mass characteristics, I looked at a couple of NUCAPS soundings further to the west. The first was west of Pittsburgh along the PA/OH border.



The mid level lapse rates were the same as further east, but the warmer temps and higher dew points were supporting non-zero SBCAPE values. There was still some CIN, however, and the MLCAPE was a paltry 23 J/kg.
Moving further west, I examined a NUCAPS soudning in central Ohio, potentially indicative of the air mass that would move into the CWA later in the day due to the mean westerly flow at mid and upper levels.



There was a noticeable difference in the mid level lapse rates, with a more significant value of 7.1 C/km.  Also notice the DCAPE was in excess of 1000 J/kg, compared to values of 500-600 J/kg further east. This would indicate that there will be at least a threat of severe winds with convection that develops later in the day in the CTP CWA despite the early in the day convection that modified the air mass during.

Thorcaster

TX Panhandle AllSky CAPE

A moderate risk for severe weather across portions of the Texas Panhandle today. Some convection is already on going along and north of a nearly stationary front stretched from the northern Panhandle into Kansas. Despite the cloud debris, the All Sky layer CAPE product still looks to be doing an acceptable job of analyzing the degree of instability present in the area. 18z values near Amarillo match well with the 18z special sounding at KAMA with values generally between 1600-2000 J/kg. The blotchiness of the all sky product between clear/cloud cover is a bit distracting, but the difference in values is a small enough magnitude that it does not compromise the forecaster's ability to use the product.



Dave Grohl

Examining environment using All Sky Lap PW

Covering the CTP (State College) area today. Initial convection has moved through, but models are suggesting redevelopment later in the afternoon along a front.  The help see changes in the atmospheric moisture, I've captured an animation of a 4 panel AllSkyLAP PW.



For reference, the upper left is the total column PW, the upper right is 1-0.9 sigma, the lower left is 0.9-0.7 sigma, and the lower right is 0.7-0.3 sigma.  What stands out to me surging eastward of lower values of the upper-most layer (0.7-0.3) towards the CWA, while the lowest layer (1-0.9) is remaining mainly unchanged. This suggests that the drying above the 0.7 sigma level (approximately 600-700 mb for CTP) may lead to increased values of DCAPE later this afternoon, so that any storms that do manage to initiate could have a threat of severe winds.

Thorcaster

Jefferson City tornado

A violent tornado hit the capital of Missouri last night at around 11:20pm local time. ProbTor showed rapid increases as well as some large fluctuations in probability prior to and during the tornado. After leaving Jefferson City, the storm continued to be warned and ProbTor again increased to probabilities ≥ 60% for about an hour; no reports of any kind were recorded during this time, however. You can see the archived time series of probabilities and predictors here.

Figure 1: Time series of ProbSevere products with NWS warnings and LSRs.

Figure 2: ProbSevere with MRMS MergedRef and NWS warnings in AWIPS2

GLM ENTLN comparison

Comparing GLM flash extent density and GLM event density to ground based ENTLN data along the Kansas/Missouri border region, there is a notable minimum in GLM data with a couple of the large clusters of ground based lightning clusters, while the other ground based lightning clusters seem to correlate relatively well with GLM data. Very strange indeed



-64BoggsLites

Lightning Jump in GLM FED, but not Earth Networks data

Storms continue just after 7pm near the Oklahoma/Texas border. A currently severe-warned storm saw a substantial and rapid increase in lightning activity observed by the GLM Flash Extent Density product. However, the ground based lightning network did not follow the same trend and remained fairly steady. The ground based data is more reasonable considering the storm did not experience any sort of significant strengthening during this time period. Earlier discussions with lightning detection experts suggested the low GLM FED count may be due to the location of lightning within the storm updraft region, which could impact how well GLM can sense it. That is difficult for the typical operational meteorologist to consider in real-time since it goes well beyond current training, and leads to decreased forecast confidence in the lightning data.



Dave Grohl