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

PHS CAPE localized maximum compared with storms developing in the area

PHS CAPE values increase from north to south over Fort Stockton. This correlated well with RAP mesoanalyzed SB CAPE on SPC webpage. Storms actively going up along this gradient as an outflow boundary pushed south during the early afternoon from overnight convection over Oklahoma.

PHS CAPE 18Z 1 hour forecast for 19Z

PHS CAPE 18Z 2 hour forecast for 20Z.

Storms developing over Fort Stockton via Day Cloud Phase Distinction on GOES 17 Mesosector

We showed above that the north side of the outflow would contain more instability – which is directly related to the moisture from the morning MCS outflow. The Gridded NUCAPS provides additional insight using the 850mb moisture fields from both AQUA and NOAA20 respectively – validating our hypothesis.

We double checked since there was a dust advisory/dust in the forecast and yes – Dust

Don’t warn if pop = 0

Convection was skirting the northeast portion of the CWA so we’ll use the recent pass of NOAA-20 to view the potential for convection redevelopment to the west and affecting the forecast in our CWA. Here are the Modified NUCAPS soundings:

The top image is for the sounding in Jones county, below is Scurry – which shows a capping inversion still in place.

Storm Motion

Weak winds aloft and throughout the atmosphere have contributed to very little in the way of storm motion. Hence, locally heavy rainfall may begin to evolve, even over an area that has received very little rainfall in the last 6 months.

Optical Flow Winds in the 200-100 mb level.

Day Cloud Phase valid 2041Z.

Day Cloud Phase valid 2141Z.

PHS depicts this plume of moisture and associated instability will back into New Mexico this evening. Could it play a part in tomorrow’s severe weather risk?

Here is what happened at El Paso when the front backed into the area – Dewpoint jumped from 30F to 50F

– David Spritz

– Mr. Bean

ILN HWT Blog Day 3


Did finally get a chance to check out NUCAPS for today’s case as the timing and location of the data was more compatible. It was good info ahead of the storms as it showed the low LCL values (mainly noticed in the modified soundings), below 1000 ft which is what you want to see for potential tornadoes. Overall, liked getting to dig into the NUCAP soundings, but given the finicky timing and data quality, it’s not something I could use on a regular basis for warning operations. Would be better suited for short term forecasting or possibly as the mesoanalyst.

GLM & LightningCast

For GLM, I set the max value at 130. I originally set it to 65 as I had been using in the high plains the past few days, but for these midwest storms it seemed too sensitive. 130 was a good value for today, likely because of the larger and more numerous storms than I dealt with today versus the previous days.
Also tried out the parallax corrected LightningCast today. Liked that it gave a more accurate location when using it for a specific location such as today’s DSS event. While it was made to pair with radar, it was still useful when using it with satellite products – just had to take a few seconds to make the mental adjustments at the beginning.


Prior to entering the ILN CWA, the PHS STP showed an area of high STP values in and near Rush County, Indiana. The actual IND office did issue a tor warning for this area at 4 PM ET.
Over time, I did notice that for STP, really just the current hour and the next couple of hours were useful. Jumping to 3 or 4 hours ahead it seemed that the data was missing for areas I expected to see higher values. Once the next run came in and I went back and looked, the data was much better. For an example below, there was a vast difference for 21Z between the 18Z run and the 20Z run where the 18Z run for that time did not seem realistic but the 20Z run was more what I expected to see.
08.18 run for 21Z


After talking with one of the ProbSevere people, was able to learn that the threshold for ProbTor is lower than that for Wind or Hail. For training purposes, it would be good to include this information to give a mental threshold for forecasters, such as an ongoing tornado would likely see a max of around 60% for ProbTor. It makes sense that the probs would be lower for tors just as they are for SPC outlooks where the tor percentages are also lower than that for wind or hail.
– Matador

Comparing NUCAPS Soundings along Warm Front Passage

NUCAPS Sounding (1832 UTC)

NUCAPS Modified Sounding (1832 UTC)

NUCAPS and NUCAPS Modified soundings displayed were along a warm frontal passage lifting south to north across southern Indiana. The modified NUCAPS sounding provided a more realistic depiction of the environment with higher levels of instability (CAPE and DCAPE). Furthermore, the LCL values represented in the modified sounding were lower; depicting an environment more favorable for tornadoes along the warm front.

– 2%hatched

Northeast Colorado Supercells

Nowcasting Supercell storm entering CWA: The loop of instability and SigTor highlight the southeast/south central CWA east of Colorado Spring, ahead of an already ongoing storm. North of this storm an environment of favorable instability exists up to about the latitude of Denver, with a significant drop off to the north.

When it comes to high and northern plains – parallax becomes an issue. In this case lighting was occurring just on the other side of the border with the CWA, so here are the two LightningCasts (with/without parallax correction) for comparison:

ProbSevere v3 increases correlating to entering a favorable environment

PHI localized CAPE corridor

New area of MFA suggesting spitting storm with new updraft core of the established cell. (1950 UTC)

Storm cell split denoted by MFA with two distinct areas of MFA in upper right panel. (2000 UTC)

Focused on the cell east of Denver – this cell and subsequent others that developed are in the favorable area of instability. Just to the north of Boulder we spotted a few cells that attempted to develop, however in the lower instability environment movement off the higher terrain resulted in these cells falling apart. Through the rest of the afternoon this area remained convection free.

Sig Tor blip. A SRVE like feature was observed but at this time convergence associated with this feature wasn’t favorably located under the updraft.

Cell developing east of Denver, noted by the MFA  in the upper right panel. (2020 UTC)

Cell rapidly develops in an area of localized higher instability denoted by the PHS values discussed earlier on.(2034 UTC)

The LightningCast has identified the left turning nature of the storm(s) east of Denver

An interesting note was comparing the differences between GOES East (left panel) and GOES West (right panel). These subtle differences can  be effective in analyzing the strengthening of a thunderstorm.

In the middle of METWATCH – NUCAPS became available (about 1 hour latency). The sounding below is a modified NUCAPS profile, depicting the environment in which our storms developed. Storm mode was supercellular with frequent spitting of cells.

-Mr. Bean