NUCAPS Sounding Verification – Day 3 (June 15, 2022)

I had a great opportunity to get some verification on a NUCAP sounding that passed through shortly after 19z on June 15, 2022.  It was the NOAA-20 which just happened to pass over eastern Iowa where the DVN WFO launched a special sounding at 19z on the same day.  I’d estimate the locations of the two soundings compared were roughly 50-60 miles apart. The DVN sounding was equidistant from 4 NUCAP soundings and all those soundings had very similar readouts from one another (see Figure 1).  One of the disadvantages of the NUCAP soundings is no winds are measured, but there are plenty of other parameters that could be compared from the two soundings. The first thing that I compared were the CAPE values (See Table 1).  The other two tables below compare other various parameters.

Some interesting differences between the CAPE values measured. Uncertain why the NUCAP sounding doesn’t suggest any 0-3CAPE values, especially since the much larger surface based CAPE.  Another big difference that really stood out was the freezing level heights and the Convective Temperature. Obviously the NUCAP sounding may have overestimated the temperature profile and thus larger CAPE values, but I found it interesting that the freezing level from the NUCAPs sounding was slightly lower. The RH values were fairly similar, particularly the midRH values, but also eyeballing the dew point temperature profile, they are pretty close near the surface.

Overall, I do like the NUCAP soundings availability as it is another tool available for the forecast toolbox.  It might be wise (as with all things meteorology) to be careful with totally believing some of the NUCAP sounding readings after seeing this comparison.

Table 1: CAPE parameters compared from 19z soundings.  (J/kg)


Table 2: Comparing various parameters found in soundings. Note: LCL, LFC, LI, etc are all measured from the surface.


Table 3: Comparing various lapse rates and -20C/-30C heights.


Figure 1: Location of the DVN 19z special sounding and the NUCAPS NOAA-20 1921z sounding.

Figure 2: DVN special sounding launched at 19z on Jun 15, 2022.

Figure 3: NUCAP NOAA-20 sounding at 1943z on Jun 15, 2022.


The utility of satellite derived data in mesoanalysis & near term convective forecasting

The most common mesoanalysis tool is the SPC (RAP) Mesoanalysis Page

While there was no new convection in the operational period for the RNK CWA, satellite based products did show their utility as a cross check with the SPC Mesoanalysis. Since the SPC Meso-a page starts with a RAP model background field, the ability to QC check this data will be helpful in gauging the accuracy of hourly RAP and HRRR model fields. In this way, you can gauge whether the Mesoanalysis and hourly updating fields are either on track or likely vary in meaningful ways from satellite derived data.   Having this data will be especially useful in locations that do not have frequent or any aircraft vapor soundings.

Mid-level lapse rates

SPC Meso-A 700-500 mb lapse rates at 19z 6/14

NUCAPS 700-500 mb lapse rates at 1819z 6/14

Excluding the likely unreliable data in the region of lingering cloud cover across central Virginia, the NUCAPS data roughly ranged from 6.5C to 7.6C/km across the RNK CWA, which is fairly close to the SPC Meso-A 700-500 mb lapse rates. Within the past few years, maximum 2-6 km AGL lapse rates were added to the SPC Meso-A page. The question I had was, with its good mid-level moisture sampling, would a NUCAPS sounding be a good QC check for the SPC max 2-6 km AGL LR field? Examples are shown below.

SPC Meso-A Max lapse rate (C/km) in 2-6 km AGL layer at 19z 6/14

NUCAPS sounding near Martinsville, VA at 1819z 6/14

As you can see from the SPC mesoanalysis graphic, there was a region of 7.5 C/km to 8.4 C/km maximum lapse rates in the 2-6 km AGL layer. The NUCAPS sounding above sampled a layer of 7.9 C/km lapse rates from just below 700 mb to just below 500 mb, which verifies the SPC Meso-A field.

CAPE analysis

SPC Meso-A SBCAPE and SBCIN at 20z 6/14

SPC Meso-A MLCAPE and MLCIN at 20z 6/14

SPC Meso-A MUCAPE and LPL at 20z 6/14

Here we’ll compare the SPC Meso-A graphics to the PHS initialization at the same hour.

PHS SFC CAPE at 20z 6/14

In general, the CAPE values on the satellite derived initialization is less aggressive the SPC Meso-A SBCAPE, but the distribution is similar, showing a west to east gradient, with lower values east where there remained lingering debris cloud cover. The MLCAPE and MUCAPE fields show a similar west-east gradient in CAPE, while SBCIN and MLCIN are also maximized in the cloud cover area across central VA.

The gridded NUCAPS MAXCAPE field was from the 18z hour per 1819z sounding availability, and was noisier data as would be expected due to unreliable retrievals under thick cloud cover.

Gridded NUCAPS MAXCAPE at 18z 6/14

Excluding the bullseye to the northeast, the distribution on the NUCAPS compares favorably to the SPC Meso-A MUCAPE field. Furthermore, recalling the NUCAPS 1819z sounding near Martinsville, MUCAPE values over that area on the SPC Meso-A field vs. the NUCAPS sounding match up well. While the time difference between the NUCAPS and SPC Meso-A fields is something to take into consideration when using the data, the less than 2-hour difference between them helps in this case. Furthermore, if we were using the NUCAPS data to compare to the SPC Meso-A graphics, we would’ve done a direct 18z check as well.

– Hurricane84

Storm Movement and Severity at TAE

Down in Tallahassee, there are two boundary layers where storms are initiating or ongoing.  There is a lingering MCS that moved down from the Midwest overnight and a Sea Breeze. You can see the CAPE gradients along the both boundaries and how that progresses forward in time with both the boundaries interacting with one another.




This tracks very well when you overlay the visible satellite imagery with the PHS images as you can see the cumulus field along the CAPE gradient. This gives a good visualization of where storms are initiating along the Sea Breeze and the strongest storm movement along the MCS.
As these two boundaries move closer together they will be moving into a more favorable low level environment. It would be nice to have the Polar Orbiting Satellite NUCAPS sounding data available. This way we could verify lapse rates and what Prob Severe is giving us. While an upper level ridge is in place over the southern CONUS what sounding information we did have early on in the forecast period was very helpful as outside of the storm environment skies were clear. I was able to grab some gridded NUCAPS data that shows the diurnal destabilization of the low levels from 18Z. Now that it is 21Z, that data isn’t as helpful in either a warning or pre convective event because things could have changed drastically in the 3 hrs since the last Polar Orbiter moved through.
After overlaying Prob Severe with the PHS CAPE and Visible Satellite imagery, you can see your strongest storms along the CAPE gradient which tracks well. However, there are differences between Prob Severe Version 2 and Version 3.
A great example of the differences between PSv3 and PSv2 is with one of the strongest storms of the day for the Tallahassee CWA. Version 2 seems to try to highlight a hail threat at 48% while Version 3 has prob severe hail at 6%.  It seems that Version 2 is overestimating the Hail threat for this area. Especially given the subpar mid level lapse rates at 5 C/km or less, storm motion of around 5 kts or less and the upper level subsidence. The storm environment just is not conducive to produce quarter sized or larger hail.
– Cirrus Fields

NUCAPS Sounding Feedback – Day 2

One of the first things that I realized that became a challenge when experimenting with the NUCAPS soundings was when after you load up one from the map, Nsharp loads up in another tab automatically.  This is totally fine, but a nice feature would be to show the location of the dot that you clicked on. This might be in a small map located in Nsharp.

Another cool feature (in AWIPS) would be to maybe highlight the dot that is already loaded in Nsharp on the planview map.  Because when you go back to the planview to click another dot, I’d forget which one I already loaded.  I guess to help this, another option would be to have the capability to load up multiple dot soundings and toggle them off and on.

Lastly, a feature I’d love to see are winds in these NUCAP soundings.  Winds are an extremely powerful tool when forecasting severe storm mode, storm motion, etc.  but also it would be helpful to identify levels of turbulence and even LLWS.  If we could see areas where there might be moderate to severe turbulence, this is great information to air traffic controllers in order to divert aircraft to different levels or north/south of those strong winds.


Comparing profiles and instability

For the RNK CWA today, new afternoon convection didn’t materialize, although residual precip and cloud cover exited the eastern CWA to the southeast (blue arrow in KCFX 0.5 Z below from ~19Z) and seem to have left stable air behind.

The corresponding visible satellite for the same time is shown below.



Only the western half of the CWA looked to remain sun-lit, with potential for additional development. Although there wasn’t much forcing, initially the airmass looked unstable, but how unstable was it really?

Looking at the RAP forecast valid at 19Z below (point B corresponds to the KFCX radar location), around 4000 J/kg are forecast.  It’s worth noting, the RAP model did correctly capture the relatively low CAPE to the east, in the stable area where previous precipitation was still exiting.

However, leveraging polar hyper-spectral sounding and ABI combined modifications to a RAP-like model, the following PHSnABI derived CAPE can be compared to the RAP forecast above.

This seems to show a more toned down instability situation relative to the RAP, particularly around our point B.  If correct, this could partly explain the less-than-anticipated convective development.  But the higher resolution data also gives clues to where CAPE remains relatively higher than the surroundings.  In fact, the 19Z visible satellite does appear to show an attempt at cumulus development along the CAPE gradient east of point B… to be fair, the RAP had the same gradient, too.  I didn’t get a chance to overlay visible imagery with the PHSnABI data above today, but it would’ve been interesting to see directly how the cloud fields overlapped.

I didn’t dig deep into why PHSnABI CAPE was lower than the RAP, but the comparison graphics available on Polar/Geo-Satellite Atmospheric Profiles – SSEC ( could hold answers.

Between the plotted differences in both temperature and mixing ratio, the values in central/western Virginia are a bit noisy and hard to generalize… but there do seem to be some reductions particularly in mixing ratio at all three levels (850, 700, and 500 hPa), suggesting RAP might have been too moist. (Zoomed in example below for 850 hPa SAT minus RAP mixing ratio over Virginia, with dark blue indicating -5 g/kg correction )

Now how about soundings? Looking at a special ~19Z (or 18Z?) sounding from KRNK, a colocated RAP model sounding (at point B) also at 19Z, and a NUCAPS sounding around the same point and time, we can compare the temperature and moisture profiles.

Overall, temperature profiles appear decent for all three. It’s primarily moisture which seems to differ, with the RAP being the most moisture-rich in both boundary layer and in a layer centered around 600 mb (note a ~1.64 PWAT from the RAP sounding). The NUCAPS has less low level and mid-level moisture overall, and a PWAT of 1.45. Despite the NUCAPS’ smoothed profile, if NUCAPS is supposed to have skill at retrieving mid-level moisture profiles, perhaps this is useful information. Finally, in the actual RAOB, a very high moisture observation at the surface may have caused the computed SB CAPE to be quite high… however, the low-level moisture as a whole arguably matches the NUCAPS sounding a bit better. The mixed layer CAPE in fact matches better between the RAOB and NUCAPS soundings, and so does the overall PWAT.

Buzz Lightyear

Difference in Instability in NUCAPS and PHS

We noticed some large differences in SBCAPE values between the NUCAPS data and the PSH over the Raleigh CWA. NUCAPS had values of over 4000 J/Kg over a large area just to the south of Raleigh with PHS indicating values of less than 1000 J/Kg over the entire domain. Looking at surface observations, the surface dewpoints from NUCAPS may be slightly higher and did modify the boundary layer in the soundings below. This modification yielded values closer to 1500-2000 J/Kg. The modified soundings also introduced some capping to the sounding as well. Included the visible satellite imagery to show the lack of cumulus development in the area to the south of Raleigh.

Gridded NUCAPS CAPE 18z

PHS CAPE at 20z.

The point selected with the nearest ob used for images below:

Original NUCAPS Sounding

Original Modified NUCAPS

Modified NUCAPS Modified Sounding for nearest observation point (90°F/70°F)


LightningCast/NUCAPS and Isolated to Scattered Convection in FGF

Convection developed rapidly to the south of the main area of convection in an area of high instability. This was first picked up by higher probabilities in the LightningCast data. There was some rapid cumulus development that was picked up well by the algorithm. Probabilities went well above 75% around 5 minutes or so from the first GLM detection. NUCAPs data indicated MLCAPEs of around 2000 J/Kg in this area supporting the quick upscale growth.

Convection developed rapidly to the south of the main area of convection in an area of high instability. This was first picked up by higher probabilities in the LightningCast data. There was some rapid cumulus development that was picked up well by the algorithm. Probabilities went well above 75% around 5 minutes or so from the first GLM detection. NUCAPs data indicated MLCAPEs of around 2000 J/Kg in this area supporting the quick upscale growth.

LightningCast and GLM at 2131 UTC

DCP RGB and LightningCast  2131 UTC

MRMS -10 Reflectivity and LightningCast first GLM detection at 2135 UTC

So let’s take a look at some NUCAPS soundings as we had three overpasses right before the convection initiated in the above examples.  Here is the first overpass with the sounding point selected with the red arrow:

NUCAPS Sounding at 1823 Z

Not too shabby with a MLCAPE value of 2094 J/kg.  (And why mixed-layer? Hank likes ML because very few times do parcels start at the surface for SB, and MUCAPE is just fun to look at).

The next overpass was 2003 UTC (about an hour and a half after the previous overpass) to see if the environment has changed much:

MLCAPE of 1235.  Hmmmm…that’s quite a drop in MLCAPE compared to previous overpass.  Two things to remember; this is on the edge of the field-of-view (matter of fact, the eastern edge).  Luckily we have a Modified NUCAPS for the same profile point which adjusts the boundary layer:

Yeah, that looks much more reasonable based on observational trends (few clouds to change the mid-atmospheric profile, increasing surface T/Td conditions) with 2185 J/kg MLCAPE.  But wait, there’s more!  We also have a:


This was almost directly under NADIR so we should have much better profile retrieval.  Sure enough, MLCAPE value is almost 3000 J/kg in between the 1823 and 2003 UTC NOAA-20 sounding retrievals.

How does this all tie into the weather for FGF today?  This is what the SPC Mesoanalysis graphics had for 2100 UTC MLCAPE values:

They all combine to increase confidence on what conditions COULD be in areas where the models are saying one thing and an observational system is indicating potential reality (remember, it’s still a remote sensing platform with their own set of issues). In our case, the bulls-eye of 3000 J/kg in east central Minnesota is likely real and needs to be an area to watch…and that is where the Lightning Cast product at the start of our post indicated the potential for new activity to develop.  Pretty cool stuff…

– Marty McFly/Hank Pym

Metwatch for Wilmington DSS event

Metwatch for Wilmington NC started with modified NUCAPS soundings and a comparison with NAM BUFKIT profiles:

Looking at 700mb temperatures, BUFKIT has about 8C for that layer, and here is the gridded NUCAPS 700mb temperature layer. Note: not a lot of advection noted at 700mb, with low level dry advection (not shown)

Watching this cell just outside the CWA pulse and then fall apart…PWV3 never exceeds 4% with this pulse. LightingCast also showed a rapid drop in probabilities.

Not much happened today, but just along the coast was this little area of enhanced CAPE (3000j/kg)…so you’re saying there’s a chance…

Comparison between parallax corrected and uncorrected lightning cast. You can see the image above and to the right (corrected) has some higher percentages getting into the 20 mi range ring compared to the non corrected data which just has the 25% grazing the 20 mi range ring. Having the corrected data could be more beneficial to providing DSS support.

– Mr. Bean

– Noctilucent

LBF HWT Blog Day 4

We didn’t have too many storms occur during operations today, but that allowed us to be able to focus more on CI.

LightningCast for CI

Was able to use LightningCast for convective initiation today as LBF was waiting for storms to fire back up for the afternoon and evening. Initially we were thinking storms would form first over the southern portion of the CWA based off of modeled convective parameters but at 2101Z, a 25% chance of lightning popped up via LC for the north-central portion of the forecast area. This 25% contour appeared a few minutes before radar reflectivity started showing up for the same area. Seeing even the 10% contour show up earlier on, clued me into the fact that we needed to shift our focus further north than we originally thought. These storms seemed to be forming along a shear gradient and weak boundary.
Of note, I am using the parallax corrected LC.
LC, GLM FED, and DCPD at 2100Z
LBF radar at 2109Z
By 2116Z, both GLM and ENTLN showed the first flash of lightning, allowing for around 15 minutes of lead time off of the 25% contour.
For comparison, these storms were forming ahead of the highest PHS CAPE and ahead of any of its stronger gradients.
As our day was winding down, LC continued to indicate areas to watch before it showed up on radar, but I did not grab additional images.


Tried to compare NUCAPS soundings today as we did have an overlap, but unfortunately ran into technical issues within my CAVE so was not able to do much with it. Another limiting factor was that the only “green” soundings from Aqua within our CWA fell within the far western scans which we were told by one of the developers they would next expect good data from, being on the limb. But for comparison, here are Aqua (1911Z) and NOAA-20 (1953Z) sounding from points NW of North Platte.
Points selected were both NW of the town of North Platte, circled below. The NE point of the two is Aqua and SW point is NOAA-20
– Matador

PHS, NUCAPS, Optical Flow, Prob Severe Fun


Today worked out well with PHS and NUCAPS. NUCAPS data came in shortly after opening up our work stations. We decided to compare the output between PHS, NUCAPS, and SPC mesoscale analysis. The variable that we chose was surface CAPE.
They all seemed to match up well highlighting the higher instability to the south that would gradually  push north this afternoon. It was definitely a confidence builder in each product to see the agreement between them.

Optical Flow

We also decided to compare the Optical Flow winds to SPC mesoscale analysis. Once storms developed a bit more, you can pick out a slight directional divergence signal in the flow. Looking at SPC mesoscale analysis there is also directional divergence is present in the mesoscale analysis.
Overall looking at these two examples, using these tools together can be a way to verify information and give the meteorologist more confidence (or less) in a specific product to help them with forecasts, DSS, and warning operations.

Prob Severe

We were able to compare Prob Severe V3 to the time when there was an observed report and when the new tornado warning came with a radar observed tag due to a CC drop. The first image is when there was a twitter report of a tornado around 2142Z in SE Darke county.

At 2144Z the Prob Severe V2 tornado jumped to 21% while V3 only went to 6%.

The next image below is when the radar confirmed tornado was reported.
– Noctilucent & Matador