NUCAPS Data from Yesterday’s (May 20th) Event…

So, at the map briefing this morning there was a LOT of discussion about yesterday’s event, and the fact that despite the tornadoes that did occur, this was a “bust” of sorts.   That is, there wasn’t near the widespread development of supercells that was anticipated.  There may be multiple reasons for this, but I thought I’d take an initial look at some data and soundings again from yesterday to see if anything stands out that I happened to miss.

Here’s a sounding (radiosonde) taken from Norman (KOUN) yesterday at 18 UTC 20 May 2019.

KOUN Sounding (radiosonde) from 18 UTC 20 May 2019

Notice that lapse rates were not particularly steep through the sounding, with 850-500 lapse rates around 6 C/km.  Also, notice the deep moist layer from the surface up through ~700 mb, which I’m told that this is rather unusual for this area.

Ok, let’s take a look at a NUCAPS sounding in this proximity taken from the ~20 UTC swath.

NUCAPS Sounding from ~20 UTC 20 May 2019 (“green” sounding south of Norman, 34.98N 98.26W)

Immediately, I notice that the NUCAPS sounding doesn’t have the deep moist layer that the KOUN sounding showed just about 2 hours earlier.  If anything, this layer did not disappear during the 2 hours, it remained, and perhaps even got a bit deeper.  The 00 UTC KOUN sounding (not shown) indicated a moist depth up through about 680 mb or so.  Ok fine…there’s the limitations with the accuracy of observations in the boundary layer in NUCAPS, but this is still important to capture since many severe weather parameters are derived from the surface or near-surface layers.  However, it was noticed that lapse rates aloft were fairly similar, showing lapse rates that were not very steep, about 6.6 C/km in the 850-500 mb layer.  The modified sounding (shown next) also didn’t capture the moist boundary layer.

Modified NUCAPS Sounding from S of Norman, 34.98N, 98.26W

I did want to point out again the good characterization of the mid-layers.  Granted, while the NUCAPS soundings didn’t capture every squiggle in the dew point temperature aloft, it did capture the overall character of the moisture profile.

Well, I ended up having to give up my workstation, but perhaps this case should be investigated some more.  Although not shown here, the lapse rates and theta-e from my memory did appear to show a relatively large W-E gradient across the area from north Texas into S-Central Ok.


NUCAPS Soundings Observations…Finally a Swath Over our Area of Severe Weather…

Hi all,

Ok, just a couple of quick observations and comparison of a NUCAPS (direct broadcast) sounding with a modified sounding over an area of interest this afternoon.  The NUCAPS sounding locations and the particular sounding of interest can be seen in Image 1 below.

Image 1: NUCAPS Sounding locations near 20 UTC 20 May 2019.  The Direct Broadcast and Modified Soundings that appear in this analysis were taken from the location of the pointer (notice this is in the far SW portion of the High Risk in north Texas).

The next image below (image 2) shows the Direct Broadcast NUCAPS sounding valid ~2000 UTC 20 May 2019.   The sounding indicates high CAPE values at this sounding location (~2800 J/Kg MUCAPE, and 2400 J/Kg MLCAPE), and steep lapse rates aloft, in excess of 8 C/km.  This type of atmospheric profile would support severe weather in the area today.

Image 2:  DB Sounding taken in SW corner of High Risk (location shown at pointer above).

The next image is the modified sounding taken at the same location.  Notice the increased CAPE values…

Image 3: Modified NUCAPS sounding from the same location as above.  However, with the modified boundary layer, notice the higher overall CAPE values.

By the way, soundings in this general area, including the yellow soundings indicated high CAPEs with “reasonable” looking values.  However, there was a fairly significant gradient noticed in overall low-level instability noticed in soundings to the east of this location.  This could be a good case for the NUCAPS team to go back and take a further look.

-Kris W

NUCAPS swath…just a bit too far east…

So, hello from my initial post from HWT, here during the week of May 20th.  Yes, this is shaping up to be an active day and perhaps week.  Taking a first look at the NUCAPS soundings for this afternoon…and…the latest ~18 UTC swath is just a bit too far east to be of a lot of use here in the primary action area for severe convection.  Notice in the first image the SPC Outlooks (High Risk area nearly entirely to the west of the soundings).   Nevertheless, I’ll take a look at the next swath to see the coverage over the main area of expected severe weather.

Image: Day One Convective Outlook (from SPC), NUCAPS Improved Latency soundings (~1817 UTC), and GOES-16 Vis (0.64 um).

-Kris W

the California convection that could actually convect

A late season trof moving onto the west coast has everyone east of the Rockies excited for tomorrow and the weekend. It is associated with an unusually late season and significant rain event throughout CA with afternoon storms scattered about in the central valley, deserts, and Sierra Nevada. The GLM was able to detect lightning in several storms in CA and NV. NOAA-20 made an overpass around 21Z and provided several viable soundings in the San Joaquin Valley and near the CA coast.

The NUCAPS sounding centered in Tulare County is shown below. MUCAPE values on the order of 563 J/kg were supportive of low-topped thunderstorms.  Neighboring soundings indicated similar or slightly reduced values of instability. With the focus on severe convection east of the Rockies, it is nice to see NUCAPS perform so well in a completely different region and dynamical regime (namely post-frontal open cellular convection).

Brian Kahn


15 min prior to 1.75″ hail and 20 min prior to baseball-size hail, a supercell tracked NNW-SSE through Vermillion Co, IL …the Probsvr nailed the values for ProbHail at 96%, VILD 4.3, and a well defined TVS (100kt G-G) and strong MESO on NEXRAD ~ 7k’NUCAPS SVR TS values kinda nailed it in Ern IL :

East Central IL  (green dot) MU and FCST SFC CAPE were > 4000, LIs were > 12, DCAPE > 1000 (~50KT Gusts), SHIP > 1 and LR H8 – H5 ~8SRM showed Storm Top Div > 130kt 12 min prior to the Baseball Sized hailThis storm is not diminishing, with Storm Top DIV remaining well over 100ktEastern end of MCS continues to chug thru central IN (2130-2300z), ProbSVR ~ 23z looking good, more warnings on the way

Were there indications there could be large hail in eastern IL?

Short answer: Yep.

NUCAPS Modified Sounding near Champaign/Urbana, IL from 18Z pass.

Since there were no 18-19Z special soundings from the IL/IN area, I looked to the AllSkyLAP CAPE which was only getting GFS retrievals in the ILX area. Those values were around 2300 J/KG or so.  The NUCAPS modified sounding near Champaign/Urbana, IL (shown above; the closest green dot to the storm that produced the severe hail), suggested more than 3500 J/KG of MLCAPE. Yesterday’s NUCAPS soundings suggested that the NUCAPS CAPE values were a bit high, but the ProbSevere MLCAPE values at the time of the baseball size hail in Westville (2105Z) were near 2773 J/KG.  So, yes, plenty of sources suggested high CAPE and thus there could be large hail in the area.

Also of note: The operational GOES 16 CAPE did not show any values because of clouds across the area.

-Tempest Sooner

A Day to Compare

I initially wanted to compare model data, especially skew-t’s, that I usually use, to the NUCAPS products. My purpose was to  ascertain the feasibility of replacing or supplementing  point based model products with NUCAPS. As I was unable to access the model data I use daily I decided to compare NUCAPS with NAM and GFS.

First the comparisons in the rapidly changing thunderstorm environment in which I interrogated a large MCS over the Illinois/Indiana border.

I compared NUCAPS 18z skew-t (from clear air area) to NAM and GFS skew-t’s, at the same time and location.

NUCAPS presents a much more stable and dry environment than the model skew-t shows, and also much more stable than the actual current environment considering this storm has already produced hail, tornadoes and heavy rain.

Next, I compared an AllSkyLAP CAPE img at 18z (point J on the above picture),  to a NAM CAPE map over the same area/time. AllSkyLAP seems to be about 500J/kg higher than the NAM CAPE map.

Finally, I compared a NUCAPS CAPE img and the NUCAPS Skew-T at 18z over the same area and there was a huge variance. The skew-t was higher than the CAPE img by over 1300J/kg.

Lastly I decided to compare NUCAPS and model data from a stable area, non changing area.

I compared an observed skew-t from the KS/OK boarder to a NUCAPS skew-t. There is a one hour difference in the data but for the sake of this comparison I think this will work. 

The observed skew-t is a relatively dry column with .87pw and a T/D of 31/20C  at the surface and 10/-20C at 700mb. The CAPE is at a ridiculous 3746 J/kg. But with no moisture, lifting mechanism nor shear I wouldn’t expect development. When compared to the NUCAPS skew-t one can see a definitive difference. CAPE on the NUCAPS is at 0 with T/D at 24/11C at the surface and 7.9/-9.3C at 700MB which is a huge departure from what the observed skew-t showed…but how would the observed skew-t hold up to a model skew-t?

NAM 18Z model skew-t compared to the 17Z observed skew-t from the same area shows 28/17C SFC temps, only 3C off from the observed skew-t and at 700MB NAM shows 9.5/-8C only .5C off the temperature and 11 off the DP. Also, CAPE was much closer than when compared to the NUCAPS where SFC CAPE on the NAM is 3246J/kg and 3746J/kg on the observed.

Overall, after this small sample size of data, both severe weather and in clear weather, I believe that I would continue to use NAM/GFS over NUCAPS for my point based forecast needs.