Gridded NUCAPS Issue WI/MN

Sampling Total PW gridded NUCAPS with contours overlaid on top, we see that the values are unrealistically high (over 3 inches). The 18 UTC soundings from the Twin Cities offices shows PWATs only around 1.30” which confirms this is incorrect. Also, the contours are in centimeters, not inches which is what the images. I plotted the NUCAPS sounding points to see if the points were “yellow” but it looks like the points were unavailable at this time step.

From this time step, the gridded NUCAPS matched up very well with the special 18 UTC soundings and the total PW values are realistic and make sense given the environment. Also the NUCAP points are all green which solidifies that the satellite was able to obtain a good sample.

– Fear the Shear

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NUCAPS in the ARX area

Comparison of a modified 18z NUCAPS sounding in far southern MN suggested a fairly accurate temperature profile (surface temperatures in southern MN were warmer than up at MSP.). NUCAPS did miss a pronounced dry layer around 700 mb, while it was too dry higher up especially around 500mb.

We also noticed some erroneous gridded NUCAPS precipitable water data round 16z across the Midwest (values of 3 to 4 inches). These looked more reasonable with the pass at 18z.

There was also 120 to 150% 850mb and 925mb RH.

The only satellite pass around that time was Metop-A. While the soundings were yellow, they generally were ok and didn’t match the gridded data.

– Barry Allen

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Modified NUCAPS Soundings-FSD

Noticed some issues with the modified NUCAPS soundings in the FSD area.  In some of the cases where the odd errors in the soundings.  Not sure what caused them or why they showed up but here are some examples.

First pass of NOAA-20.

Note the odd look of the temperature trace in the mid levels (note the sharp increase in temp just above 700mb).  This was noticed in a number of the neighboring dots.  This error seemed to get better the further away you got from this location.  We were hoping this would improve when the second pass came overhead later at 20Z.  Below is an example of this error from the second pass.

Second pass NOAA-20.

As can be seen from the image above, the second pass still had this error (note the sudden change in the temperature trace at about 600mb).  After looking at the conditions in the area, several questions as to why this was occurring came up.  It appeared the surface temperatures were rather reasonable and the atmospheric conditions were also close to what the sounding may be trying to depict.  There was some thought the modified NUCAPS may be having difficulty with the moisture trace rather than the temperature trace.

It was also noted that when using the “pop up skew-T” function it would not see this error.  It was discovered the reason for this is the “pop up skew-T” function would not see the modified soundings that Nsharp would display.  

Why this was occurring I really could not tell.  One of the PIs indicated the algorithm may not be handling the moisture trace well.  It was also noticed the surface wind fetch was coming from the southwest and that is coming off the sandhills of Nebraska.  This is a very wet area and is perpetually wet.  Is it possible that some localized moisture advection was not accounted for?  Can’t say for sure but mention it here to indicate what could be going one.  


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NUCAPS MultiSat Sampling

I was pleasantly surprised to see that when multiple sources of NUCAPS data were displayed at the same time that I could sample, via the pop up Skew-T and moving the mouse across the sounding swath, all sets of NUCAPS data and that it wasn’t dependent on which source of NUCAPS was ‘editable’.

However, depending on WHICH source of NUCAPS soundings was indicated as ‘Editable’ (in this case, the METOP-A – in blue), only those soundings could be opened in the NsharpEditor. Not necessarily a big deal but it is something that some folks may need to have explained to them.

Additionally, I have found the pop up Skew-T doesn’t always work. Often, it seems that when the NUCAPS data is more than an hour old or so, moving the mouse across the soundings results in no changes in the pop up readout. Is this related to the ‘age’ of the NUCAPS data or a bug with the pop up Skew-T?

Similarly, a new pass of data came in and I was unable to get updated readouts from the pop up Skew-T, therefore I ‘unloaded the “Radar Popup SkewT” (green legend, above), turned off sampling, then went back through the process of Volume > Popup Skew-T, turning on Sampling (right click), and sample cloud heights from NUCAPS (top of right click menu) and was able to then sample the NUCAPS.

– Guillermo

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NUCAPS sounding near Charleston

I made some comparisons between a NUCAPS sounding at 1824z near Charleston, SC and the 12z observed sounding at Charleston, SC. Both soundings were manually modified to a surface temp/dew point of 87/72 (modified NUCAPS soundings were unavailable at this location). Overall the NUCAPS sounding matches the overall profile fairly well with mid-level drying and a fat CAPE profile aloft, with similar SBCAPE, PWATs, and DCAPE values.  I did notice a warm layer centered near 700mb (the base of what appears to be an elevated mixed layer), which resulted in higher MLCIN values and higher 700-500mb lapse rates. This could indicate more capping than is actually present, though perhaps stronger convection where the cap does break. This warm layer also appears warmer than in an 18z HRRR initialized sounding at the same location.

I also looked at Gridded NUCAPS 700mb temperature data compared to 18z 700mb temperatures from the RAP and GFS. While there was some missing data in the area of interest from Gridded NUCAPS, the values just south of that area are higher than what the models were showing.

Late day update: the modified NUCAPS soundings eventually filled in.

It was a few degrees cooler at the surface, but that may be because it went off the 17z RTMA rather than the 18z METARs at that time.

– Barry Allen

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Random NUCAPS Observations

Thunderstorms in the Charleston CWA are marginally interesting at best today so I have been spending some time browsing some parameters that aren’t necessarily severe weather related. NUCAPS availability across the eastern United States looks pretty good today!

I haven’t had the opportunity to use the pop-up skew-t functionality in AWIPS until now (didn’t even know it existed, in fact). It is a bit buried and it took me a few tries to get it to work, but this makes it a lot easier to go through all of these different points and try to find an area of interest without having to go into the occasional information overload that is NSHARP unnecessarily.

After looking at some soundings I went to explore the gridded NUCAPS data, which looks very promising. There was a slight learning curve as I had to get used to the polar orbiting satellite paradigm once again, but being able to see the data from all of the points in a plan view format can help with the information overload mentioned above. I noticed the gridded NUCAPS has some ozone and Haines Index fields. Air quality and fire weather are kind of a big deal where I forecast out west, so these fields will be fun to explore once they’re available in my home AWIPS. Seems like the Ozone Anomaly fields might be a bit easier to understand than the Total Ozone, as apparently Dobson units measure the ozone differently than something like PPM. I tried to investigate this data for the west after that NUCAPS pass came in today but a lot of the gridded data was incomplete. I suspect it was due to the lack of available soundings (saw a fair amount of yellow and red for whatever reason). I’ll take another look tomorrow.

– Earl Grey Tea

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Modified NUCAPS Sampling: PopUp vs Nsharp

When trying to sample NUCAPS and modified NUCAPS soundings (via Volume > Popup SkewT) I realized that the popup SkewT only showed the actual NUCAPS profile (there was a notable peculiarity in the modified profile boundary layer that I was looking for in the popup).

I don’t think this was an error in AWIPS, because when right-clicking and selecting ‘sample cloud heights/radar skewT’, the options presented only include NUCAPS, not also modified NUCAPS. So, by my understanding, when displaying modified NUCAPS, the popup SkewT will reference the original.

This second image, perhaps, further illustrates the issue. When displaying only the modified NUCAPS on the map and selecting the profile of interest (in the FSD CWA), the sounding with the interestingly-generated inversion (I believe the subject of another blog post) displays in NsharpEditor. However, the popup SkewT profile does not, because it seems to be showing the original NUCAPS profile.

– Guillermo

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Storms in northern and central Florida


On the afternoon of June 15, 2 different convective regimes were noted across Florida, with different GLM lightning characteristics. A cold front was sinking southward towards the Florida panhandle, with convection developing along the Gulf sea breeze along the FL panhandle. Convection of more uncertain forcing developed in Central Florida.

Convection along the FL panhandle had higher MLCAPE and DCAPE due to mid-level drier air and steeper lapse rates, with somewhat lower PWATs. SBCAPE in excess of 5000 J/kg and MLCAPE in excess of 3000 J/kg was unusually high for this region. Convection in central FL was in a more tropical air mass, with PWATs at or above 2 inches and more saturated profiles. Convection in the FL panhandle developed in an area with very high microburst composite parameter values, indicating conditions very favorable for microbursts and localized damaging wind gusts.

12z TAE sounding:

15z XMR sounding:


19z DCAPE:

19z PWATs:

Microburst composite parameter 19z:

The FL panhandle convection was more intense on radar and also had higher flash extent densities. It also tended to have lower minimum flash areas, centered on locally strong updrafts. Notable hail cores were observed aloft, and melting of these hailstones caused strong downdrafts and damaging wind reports, and in a few instances quarter size hail made it to the ground, with one instance of golf ball size hail..


The central FL convection was weaker and had also been going on for longer, so there was some convective debris stratiform precipitation with larger minimum flash areas. Flash extent densities were lower than in the FL panhandle. There were still areas of lower minimum flash area centered on the updrafts.

The GLM flash points were very useful and lined up with the NLDN and ENTLN strikes and flashes. The parallax correction was especially useful for DSS purposes as partners often request notification on lightning strikes within a particular radius on the order of 8 to 20 miles, so an accurate location is important. At first glance there were much less flash points but this appeared to be due to the data only being 1 minute data without having the 5 minute accumulation that the NLDN and ENTLN offers. Having this similar 5 minute accumulation would be imperative for using the GLM flash points in operations. The sampled metadata for the flash points appeared less useful operationally. The flash area would be more of interest than the duration, but with a large number of flash points some sort of graphical depiction would be needed, and flash extent density seems to serve this purpose.


One interesting thing that was noted was v3 had much lower ProbHail than v2, while still having decent ProbSevere (mainly wind-driven values). We speculated that this was due to some of the machine learning based on environment and climatology, since severe hail would be less likely this time of the year with higher freezing levels/hot surface temperatures causing melting. However, in this case a golf ball size hail LSR was issued at 19:59z (report time appeared to be incorrect) for 2 ENE Saunders in Bay County, FL. This was comparable to MRMS MESH which maxed out at 1.89”.

On the technical side, I did want to note that typically I have sampling turned off in AWIPS, but then double-click on something that I want to sample. Since the ProbSevere timeseries plugin is also opened by double-clicking on the object, sometimes when I meant to double-click to sample the ProbSevere values I accidentally ended up opening a time series. And then I would double-click outside the ProbSevere area to sample something else or turn off sampling and I would get a black banner. Perhaps the timeseries doubleclick function could be turned on and off by making the ProbSevere product editable or not editable in the legend.


Gridded NUCAPS and individual NUCAPS soundings at 1840z showed steeper 700-500mb lapse rates than what was shown on the SPC mesoanalysis and some of the morning soundings, in areas away from convection. It’s hard to say which one was right, but the hail cores observed do seem more consistent with 700-500 mb lapse rates of near 7 C/km or greater. (Note that it would be useful to have contours to go with the images on the gridded NUCAPS plots.)

NOAA-20 sounding availability and example sounding (1823z)

1840z gridded NUCAPS 700-500mb lapse rate:

18z SPC mesoanalysis 700-500mb lapse rate:

NUCAPS also indicated the more saturated profiles/weaker lapse rates in the central FL convective regime.

NUCAPS did indicate some of the higher CAPE values, but with missing data in much of the area of interest as convection had already initiated when the pass occurred.

– Barry Allen

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NUCAPS Sounding comparison to Observed Sounding

Noticed an across the board temperature discrepancy between the Observed Sounding at KJAX and two of the NUCAPS soundings from the afternoon pass of NOAA-20.  Looked at two different NUCAPS soundings which straddled KJAX.  The morning sounding at KJAX (12Z) showed a typical morning, warm tropical but capped sounding.  The two NUCAPS soundings were from six hours later showed a surface change that would be expected but then showed decent cooling from the morning through the entire column.  The image below shows the two NUCAPS soundings, one is in focus (red/green), the second NUCAPS soundings is the drab color and the observed sounding is in blue.  This shows the two NUCAPS soundings to be very similar and follow each other well but are also a few to several degrees cooler than the observed sounding. 

While I would expect some areas of the column to cool with a sea breeze front coming through, but not the entire column.  When I see this type of discrepancy, it makes me not want to trust the NUCAPS sounding in this case as it does not seem to make much sense with the ground truth of the actual measured RAOB.  Of note, when the NUCAPS sounding was taken, the line of sight was free of clouds and the “dots” were green; however, there were thunderstorms to the north and west of KJAX and they had an outflow boundary approaching the area rapidly.  Could this have made a difference?  I don’t know but it is worth noting this did occur.  Also, we also noted the NUCAPS soundings for this area were all cold in comparison to the morning RAOB.  Looking further west to KTLH, the NUCAPS soundings and the observed soundings looked much closer and made a lot more sense.  So, could this be a marine layer influence?  Could this be just a bad batch?  Could this be a bad thermometer and wet bulb sensor on the actual RAOB?  All valid questions that I can’t answer but put here as possibilities that can’t be verified.  

Of note, we also looked at the differences between the KSC 15Z sounding and the afternoon and the afternoon pass of the NOAA-20 NUCAPS soundings.  These two were much closer and seemed to be much closer together.  Also note, the time difference between the two soundings is only 3 hours in comparison to six.  The image below is the KSC sounding comparison.  The sounding in focus is the actual KSC RAOB and the NUCAPS sounding is in the background.


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Using NUCAPS (Modified & UnModified)

Advantages to vs. AWIPS NSHARP.

NSHARP – AWIPS (Advantage is being able to see both modified & unmodified soundings (Advantage is the cleaning picture and able to display two or more soundings on the same backgrounding – Skew-T)

How two passes of the NOAA-20 near the same location can be used to determine the small changes in the atmosphere.

(Green/Red – Moisture/Temperature Profile at the 1842Z Pass)

(Green/Red – Moisture/Temperature Profile at the 2042Z Pass) Note the increase in moisture in the boundary layer which corresponds to the increase in CAPE.

These two comparisons of the soundings within two hours of each pass showed how well the NUCAPS can be used for small differences in atmospheric moisture and instability.

During this time period, there was a pronounced dry-line west of the sounding, and a synoptic scale front approximately 100 miles to the north of this NUCAPS sounding.

Note where the dryline (Cumulus line over northeast Mt) was located and how you can use NUCAPS to show how capped or uncapped the atmosphere becomes in the afternoon with the NOAA-20 passes.

– wxboy65

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