WFO Amarillo launched a 19z special sounding today in support of potential severe storms later in the evening. Meanwhile, NOAA-20 passed over WFO Amarillo at 1935z, merely 30 minutes after the observed sounding release but likely about an hour before the full observed profile was complete.

An SPC marginal risk was over west Texas (see below) for the 20z issuance with the main threats being large hail and damaging wind gusts. The 12z observed sounding from Amarillo shows a pronounced low level capping inversion with a convective temperature of around 86 degrees F. Overall, the wind profile is weak with little to no shear but just enough to support a few strong to severe storms. Mixed layer CAPE is around 1000 J/kg, but the downdraft CAPE is closer to 1200 and supports the potential for some strong to damaging wind gusts with collapsing storms and/or areas conducive to strong downward motion.

Sharppy was then utilized to compare the observed 19z sounding from Amarillo to the closest NUCAPS sounding to the office’s location. Image B contains the values for the observed sounding with the purple representing the sharppy NUCAPS sounding. Image C contains the values for the sharppy NUCAPS with the observed sounding in purple. One of the biggest differences between the soundings that plays a key role in the instability parameters is the surface temperatures. The observed sounding recorded a surface temperature of 83 degrees F, which the sharppy NUCAPS sounding recorded a surface temperature of 89 degrees F. That difference of 6 degrees fully breaks the capping inversion on the sharppy NUCAPS sounding, but the observed sounding still appears to be a few degrees shy of breaking the 750mb cap. The values such as MLCAPE are drastically different with the observed sounding showing around 1500 J/kg, while the sharppy NUCAPS sounding shows ~2500 J/kg. The observed sounding does show an increase since the 12z launch of DCAPE now around 1600 J/kg, but the sharppy NUCAPS does not relay this same increase and instead remains near 1200 J/kg.

So the biggest fault in the NUCAPS values being off was likely the surface temperatures being too warm. In order to validate this reasoning, the modified NUCAPS sounding for this time and location was utilized. However, since the modified soundings are calculated with NSHARP and not sharppy, the original NUCAPS from both algorithms were compared. Image D shows the NSHARP NUCAPS sounding pulled from the CAVE in awips. This can be compared to Image C, which was the NUCAPS sounding plotted with a different program called sharppy.

Looking at the profile itself, the biggest difference that stands out would be near the surface. As stated before the surface temperature on the sharppy NUCAPS sounding was 89 deg F, while the NSHARP sounding reveals a surface temperature of around 80 deg F. The NSHARP sounding temperature is lower than the observed sounding at 19z, but yet was able to mix out the capping inversion. Knowing that NUCAPS in general is not overly impressive with the boundary layer, there is a chance had there been a 12z pass, that the NUCAPS sounding wouldn’t have had such a strong inversion as the observational sounding at 12z showed. Therefore the surface temperature wouldn’t have needed to be as warm. The remainder of the parameters seem to compare pretty well between the two versions of the NUCAPS profile.

Now, what happens if the surface temperature from observations are used to modify the NSHARP NUCAPS profile for better representation of that boundary layer. Image E represents this modified sounding where the surface temperature is now closer to 83 deg F, which is what the 19z observed sounding from the same location measured. Comparing this modified sounding to the observed, there is still the issue of the NUCAPS wiping out the inversion layer at around 750 mb. Warming the temperature was not going to bring the inversion back, so this is something that is more a failure starting with the non-modified NSHAPR NUCAPS profile. MLCAPE is still significantly different, but ignoring the inversion in the observed sounding and looking at a surface based parcel, the two soundings are pretty comparable with around 3500 J/kg of SBCAPE. Downdraft CAPE values did not change with the modified NSHARP NUCAPS sounding and this could allude to the fact that again the NUCAPS profiles lack good boundary layer details and a much smoother profile.

Overall, had Amarillo not done a 12z launch, the NUCAPS profiles were pretty comparable to the observed sounding. The biggest concern would be if the purpose was to find if there still remains a capping inversion in place that may hinder storm development. Spoiler alert, storms did develop as temperatures warmed a bit more through the afternoon and were also just a bit warmer further west along the New Mexico/Texas border. A few severe wind reports occurred with the cluster of storms, along with some small hail and maybe even a few larger hail stones of around a quarter that weren’t reported.

– Harry Potter